@article { ISI:000227026100019, title = {Electrochemical studies of poly (3,4-ethylenedioxythiophene) PEDOT/VS2 nanocomposite as a cathode material for rechargeable lithium batteries}, journal = {Electrochemistry Communications}, volume = {7}, number = {2}, year = {2005}, month = {FEB}, pages = {213-218}, publisher = {ELSEVIER SCIENCE INC}, type = {Article}, address = {360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USA}, abstract = {

Here, we demonstrate the electrochemical characterization of a new type of layered poly (3,4-ethylenedioxythiophene) PEDOT/ VS2 nanocomposite. It has been prepared via flocculation of delaminated VS2 with subsequent in situ oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) with VS2 as a host material in the presence of an external oxidizing agent. The interlayer spacing Of VS2 expands from 5.71 to 14.01 A and this interlayer separation is consistent with the existence of a monolayer of PEDOT in the VS2 framework. X-ray diffraction, XPS and TEM studies have been;shown the change in interlayer separation is consistent with the existence of two phases of organic and inorganic species in the nanocomposites corresponding to the intercalation of PEDOT in the VS2 framework. The application potential of the nanocomposite as a cathode material for rechargeable lithium batteries is also demonstrated by the electrochemical intercalation of lithium into the PEDOT/VS2 nanocomposite, where a significant enhancement in the discharge capacity is observed (similar to130 mAh/g) compared to that (80 mAh/g) for pristine VS2. (C) 2004 Published by Elsevier B.V.

}, keywords = {layered nanocomposite, lithium batteries, polythiophene, vanadium disulfide}, issn = {1388-2481}, doi = {10.1016/j.elecom.2004.12.013}, author = {Murugan, A. Vadivel and Gopinath, Chinnakonda S. and Vijayamohanan, K.} } @article { ISI:000233825900101, title = {Enhancement of double-layer capacitance behavior and its electrical conductivity in layered poly (3, 4-ethylenedioxythiophene)-based nanocomposites}, journal = {Applied Physics Letters}, volume = {87}, number = {24}, year = {2005}, month = {DEC}, pages = {243511}, publisher = {AMER INST PHYSICS}, address = {CIRCULATION \& FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA}, abstract = {

In this letter, we report on the enhanced double-layer capacitance of a layered poly (3, 4-ethylene dioxythiophene) PEDOT-MoO3 nanocomposite, which has been synthesized by a novel microwave irradiation method. The x-ray photoelectron spectroscopy analysis shows the changes in electron density and the shift in binding energy suggesting charge transfer from sulfur atoms upon PEDOT intercalation between MoO3 layers. The room-temperature conductivity for the PEDOT-MoO3 composite is found to be 1.82x10(-1) S cm(-1), which is four orders of magnitude higher than that of the pristine oxide (3.78x10(-5) S cm(-1)). The enhanced double-layer capacitance of the PEDOT-MoO3 nanocomposite (similar to 300 F g(-1)) compared to that (similar to 40 mF g(-1)) of pristine MoO3 is attributed to higher electronic conductivity, enhanced bidimensionality, and increase in surface area of the nanocomposite.

}, issn = {0003-6951}, doi = {10.1063/1.2140468}, author = {Murugan, A. Vadivel and Viswanath, A. K. and Campet, Guy and Gopinath, Chinnakonda S. and Vijayamohanan, K.} } @article { ISI:000227016500007, title = {In situ XPS investigations of Cu1-xNixZnAl-mixed metal oxide catalysts used in the oxidative steam reforming of bio-ethanol}, journal = {Applied Catalysis B - Environmental}, volume = {55}, number = {4}, year = {2005}, month = {FEB}, pages = {287-299}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

A series of CuNiZnAl-multicomponent mixed metal oxide catalysts with various Cu/Ni ratios were prepared by the thermal decomposition of Cu1-xNixZnAl-hydrotalcite-like precursors and tested for oxidative steam reforming of bio-ethanol. Dehydrogenation of EtOH to CH3CHO is favored by Cu-rich catalyst. Introduction of Ni leads to C-C bond rupture and producing CO, CO2 and CH4. H-2 yield (selectivity) varied between 2.6-3.0 mol/mol of ethanol converted (50-55\%) for all catalysts at 300 degreesC. The above catalysts were subjected to in situ XPS studies to understand the nature of active species involved in the catalytic reaction. Core level and valence band XPS as well as Auger electron spectroscopy revealed the existence of Cu2+, Ni2+ and Zn2+ ions on calcined materials. Upon in situ reduction at reactions temperatures, the Cu2+ was fully reduced to Cu-0. while Ni2+ and Zn2+ were partially reduced to Ni-0 and Zn-0, respectively. On reduction, the nature of ZnO on Cu-rich catalyst changes from crystalline to amorphous, relatively inert and highly stabilized electronically. Relative concentration of the Ni-0 and Zn-0 increases upon reduction with decreasing Cu-content. Valence band results demonstrated that the overlap between 3d bands of Cu and Ni was marginal on calcined materials, and no overlap due to metallic clusters formation after reduction. Nonetheless, the density of states at Fermi level increases dramatically for Ni-rich catalysts and likely this influences the product selectivity. (C) 2004 Elsevier B.V. All rights reserved.

}, keywords = {auger electron spectroscopy, Autothermal reforming, Bio-ethanol, copper oxide, fuel cell, Hydrogen, hydrotalcite, mixed metal oxides, nickel oxide, oxidative steam reforming, Steam reforming, XPS}, issn = {0926-3373}, doi = {10.1016/j.apcatb.2004.09.007}, author = {Velu, S. and Suzuki, K. and Vijayaraj, M. and Barman, S. and Gopinath, Chinnakonda S.} } @article { ISI:000227966600021, title = {Insight into the mechanism of selective mono-N-methylation of aniline on Cu1-xZnxFe2O4: a DRIFTS study}, journal = {Journal of Molecular Catalysis A - Chemical}, volume = {231}, number = {1-2}, year = {2005}, month = {APR}, pages = {169-180}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Mechanism of selective mono-N-methylation of aniline with methanol on Cu1-xZn2FeO4 catalysts was investigated in detail. The interaction of reactants (aniline. methanol and methanol: aniline) and possible products (N-methylaniline (NMA), N,N-dimethylaniline (DMA) and o-toluidine (OT)) on catalysts surface was studied by temperature-dependent in situ FTIR spectroscopy. Methanol adsorbs dissociatively over catalysts surface at 373 K as methoxy species and is oxidized to formate species at high temperature through dioxymethylene and/or formaldehyde as a surface intermediate species. On the other hand, adsorption of aniline:methanol mixtures shows that methanol oxidation was completely hindered in the presence of aniline. Aniline adsorbs on the Lewis acid sites at \<= 373 K with phenyl ring oriented in a perpendicular manner to the catalyst surfaced however, N-H bond scission occurs above 373 K. A comparison of adsorbed NMA and methanol: am line (3:1) mixture on Cu0.5Zn0.5Fe2O4 shows NMA forms from the reaction mixture at 473 K. However, maximum activity at 573 K in catalytic reaction studies suggests that desorption limits the methylation kinetics. FTIR study displays stable aniline and methyl species on ZnFe2O4 even at 573 K; however. no methyl species is detected on Cr0.95Zn0.05Fe2O4 at 473 K due to methanol reforming reaction and that limits the overall reaction and hence low catalytic activity. It is proposed that methanol is protonated on catalysts surface by the labile H+ due to N-H bond scission. Co-adsorption of acidity probes with aniline and methanol indicates that aniline methylation takes place at single acid-base site. (c) 2005 Elsevier B.V. All rights reserved.

}, keywords = {Aniline, Cu1-xZnxFe2O4, desorption limited, DRIFT, IR, Methanol, N-methylaniline, N-methylation, reaction mechanism}, issn = {1381-1169}, doi = {10.1016/j.molcata.2005.01.014}, author = {Vijayaraj, M. and Murugan, B. and Shubhangi B. Umbarkar and Hegde, S. G. and Gopinath, Chinnakonda S.} } @article { ISI:000230467900038, title = {Isothermal kinetic study of nitric oxide adsorption and decomposition on Pd(111) surfaces: molecular beam experiments}, journal = {Journal of Physical Chemistry B}, volume = {109}, number = {27}, year = {2005}, month = {JUL}, pages = {13283-13290}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

The kinetics of NO adsorption and dissociation on Pd(111) surfaces and the NO sticking coefficient (S-NO) were probed by isothermal kinetic measurements between 300 and 525 K using a molecular beam instrument. NO dissociation and N-2 productions were observed in the transient state from 425 K and above on Pd(l 11) surfaces with selective nitrogen production. Maximum nitrogen production was observed between 475 and 500 K. It was found that, at low temperatures, between 300 and 350 K, molecular adsorption occurs with a constant initial SNO of 0.5 until the Pd(I 11) surface is covered to about 70-80\% by NO. Then SNO rapidly decreases with further increasing NO coverage, indicating typical precursor kinetics. The dynamic adsorption-desorption equilibrium on Pd(I 11) was probed in modulated beam experiments below 500 K. CO titration experiments after NO dosing indicate the diffusion of oxygen into the subsurface regions and beginning surface oxidation at \>= 475 K. Finally, we discuss the results with respect to the rate-limiting character of the different elementary steps of the reaction system.

}, issn = {1520-6106}, doi = {10.1021/jp050813f}, author = {Thirunavukkarasu, K and Thirumoorthy, K and Libuda, X and Gopinath, Chinnakonda S.} } @article { ISI:000227146700004, title = {MCM-41-supported platinum carbonyl cluster-derived asymmetric hydrogenation catalyst}, journal = {Journal of Catalysis}, volume = {229}, number = {2}, year = {2005}, month = {JAN}, pages = {298-302}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

Anionic platinum carbonyl cluster has been ion paired with cinchonidium groups that are chemically bound to the surface of MCM-41 and fumed silica. In the hydrogenation of methyl pyruvate or acetophenone the fumed silica-based catalyst gives zero enantioselectivity, but under optimum conditions enantiomeric excesses of \>90 and similar to40\%, respectively, are obtained with the MCM-41-based catalyst. (C) 2004 Elsevier Inc. All rights reserved.

}, keywords = {asymmetric catalysis, functionalized inorganic oxides, hydrogenation catalysts, platinum carbonyl cluster}, issn = {0021-9517}, doi = {10.1016/j.jcat.2004.11.010}, author = {Basu, Susmit and Paul, Himadri and Gopinath, Chinnakonda S. and Bhaduri, Sumit and Lahiri, Goutam Kumar} } @article { ISI:000230467900037, title = {Molecular beam study of the NO plus CO reaction on Pd(111) surfaces}, journal = {Journal of Physical Chemistry B}, volume = {109}, number = {27}, year = {2005}, month = {JUL}, pages = {13272-13282}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Nitric oxide (NO) reduction with carbon monoxide (CO) on the Pd(111) surface was studied under isothermal conditions by molecular beam techniques as a function of temperature, NO:CO beam composition, and beam flux. Systematic experiments were performed under transient and steady state conditions. Displacement of adsorbed CO by NO in the transient state of the reaction was observed at temperatures between 375 and 475 K for all the NO: CO compositions studied. NO accumulation occurs on Pd(l 11) surface under steady state conditions, below 475 K, due to stronger chemisorption of NO. The steady state reaction rates attain a maximum at about 475 K, nearly independent of beam composition. N-2 was found to be the major product of the reduction, along with a minor production of N2O. The production of N2 and N2O indicates molecular and dissociative adsorption of NO on Pd(l 11) at temperatures up to 525 K. Postreaction TPD measurements were performed in order to determine the nitrogen coverage under steady-state conditions. Finally, the results are discussed with respect to the rate-controlling character of the different elementary steps of the reaction system.

}, issn = {1520-6106}, doi = {10.1021/jp050478v}, author = {Thirunavukkarasu, K and Thirumoorthy, K and Libuda, J and Gopinath, Chinnakonda S.} } @article { ISI:000230698100015, title = {Molecular origins of wettability of hydrophobic poly(vinylidene fluoride) microporous membranes on poly(vinyl alcohol) adsorption: Surface and interface analysis by XPS}, journal = {Journal of Physical Chemistry B}, volume = {109}, number = {29}, year = {2005}, month = {JUL}, pages = {13941-13947}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

irreversible adsorption of poly(vinyl alcohol) (PVA) on hydrophobic, porous poly(vinylidene fluoride) (PVDF) membranes was carried out using aqueous PVA solution. Water permeation was observed in PVDF microporous membranes after PVA adsorption, and maximum permeability was obtained after treatment with 4\% PVA solution. Water permeability increased linearly with increasing PVA concentration up to 4\%, and then a marginal decrease with a further increase in PVA concentration occurred. PVA adsorbed PVDF membranes were subjected to intense physicochemical analysis, especially with XPS. XPS results display the presence of an interface between PVA and PVDF, and the binding energy (BE) of the interface is low for the PVDF membranes treated with 4\% PVA. Carbon from CF2-groups and F 1s core level clearly showed a decrease in its content on the surface after PVA adsorption and showed a minimum fluorine content at 4\% PVA. F Is BE shifts by 0.5 eV upon PVA adsorption and is independent of PVA concentration. EDAX analysis indicates that the bulk oxygen content remains within 4.5 +/- 0.6\% and is independent of the PVA concentration. Nonetheless, a large amount of surface atom percentage of oxygen (20 +/- 4\%) from 0 Is core level shows an increase in PVA content on the surface of PVDF, and it is restricted mostly to the surface. The 4\% PVA treated PVDF membrane clearly shows a broadening of O 1s core level to lower BE and indicates the interaction between PVDF and PVA which is significantly different compared to any other compositions. A new valence band feature at low BE, which is nonexistent on PVDF, develops after PVA adsorption. This indicates that the shift in the nature of the highest occupied molecular orbital (HOMO) derived mostly from oxygen; simultaneously, a suppression in the PVDF derived band indicates the change in nature of the PVA adsorbed surfaces from hydrophobic to hydrophilic. The above observations also suggest an irreversible electronic interaction between PVA and PVDF, possibly through charge transfer.

}, issn = {1520-6106}, doi = {10.1021/jp050806r}, author = {Gholap, S. G. and Badiger, Manohar V. and Gopinath, Chinnakonda S.} } @article { ISI:000230848700026, title = {Nature of manganese species in Ce1-xMnxO2-delta solid solutions synthesized by the solution combustion route}, journal = {Chemistry of Materials}, volume = {17}, number = {15}, year = {2005}, month = {JUL}, pages = {3983-3993}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

A series of manganese-cerium oxide composites with Mn concentrations in the range of 1-20 mol \% in ceria was prepared by the solution combustion technique using urea as fuel. The nature, type, and oxidation state of Mn species in ceria were investigated by X-ray diffraction (XRD), diffuse reflectance UV-visible spectroscopy, electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy, and temperature-programmed reduction techniques. The study reveals that the method of preparation significantly influences the type of manganese species in ceria. Wet-impregnation, coprecipitation, and solid-state synthesis techniques lead to clustered MnOx-like species in the ceria matrix, while the present method of preparation (solution combustion route) yields a highly dispersed form of Mn species. In the reported series of samples, Mn is present mainly in +2 and +3 oxidation states and there is no evidence for the presence of Mn 41 species. Powder X-ray diffraction studies at variable temperatures (298-1323 K) indicate the formation of Ce1-xMnxO2-delta Solid solutions. No separate MnOx-type phase was detected even at 1323 K. EPR studies reveal that the isolated Mn2+ and Mn2+ species are present in at least three different structural locations: species A, Mn ions in ceria-lattice defect sites; species B, Mn ions in framework Ce4+ locations; and species C, Mn ions in interstitial locations and at the surface of ceria. The Mn3+ ions in ceria exhibit a facile reduction and reoxidation behavior when exposed to dry hydrogen and subsequently to air at elevated. temperatures. A highly dispersed state of Mn3+ and Mn2+ in ceria, facile redox behavior, and a synergistic Mn-ceria interaction are some of the unique properties of this material prepared by the solution combustion procedure.

}, issn = {0897-4756}, doi = {10.1021/cm050401j}, author = {Murugan, B. and Ramaswamy, A. V. and Srinivas, D. and Gopinath, Chinnakonda S. and Ramaswamy, V.} } @article { ISI:000227565800022, title = {Oxidative dehydrogenation of ethylbenzene over vanadia-alumina catalysts in the presence of nitrous oxide: structure-activity relationship}, journal = {Journal of Catalysis}, volume = {230}, number = {2}, year = {2005}, month = {MAR}, pages = {484-492}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

A series of vanadia-alumina catalysts with different vanadia contents were prepared by a wet impregnation method. The influence of the local structure of vanadia in these catalysts on the oxidative dehydrogenation of ethylbenzene with nitrous oxide was investigated. The use of N2O as a co-feed remarkably enhanced the styrene yield compared with the use of N-2. Characterization of these vanadia catalysts by XRD, FTIR, UV-vis, TPR, XPS, and V-51 NMR techniques suggests that the nature of the VOx species depends on the vanadia loading: the predominant species are monomeric vanadia at lower loadings, two-dimensional polyvanadates at intermediate loadings, and bulk-like V2O5 and AlVO4 at higher loadings. The rate of oxidative dehydrogenation (ODH) of ethylbenzene per vanadium atom increases with vanadia loading and reaches a maximum at 10 wt\%, the loading at which the surface predominantly contains polyvanadate species. The observed variation in the selectivity of products with vanadium loading indicates that the monomeric V5+ species favors dehydrogenation, whereas bulk-like V2O5 preferentially participates in the dealkylation of ethylbenzene. The vanadium species remains at a higher oxidation state in the presence of N2O, leading to a higher styrene yield. than in a N-2 atmosphere. The ODH turnover rates increased with decreasing energy of the absorption edge in the UV-vis spectrum, at low VOx coverages of less than one monolayer on the Al2O3 surface. (c) 2005 Elsevier Inc. All rights reserved.

}, keywords = {absorption edge energy, Alumina, ethylbenzene, Nitrous oxide, oxidative dehydrogenation, polyvanadates, styrene, vanadia}, issn = {0021-9517}, doi = {10.1016/j.jcat.2005.01.010}, author = {Shiju, N. R. and Anilkumar, Mettu and Mirajkar, Subhash P. and Gopinath, Chinnakonda S. and Rao, B. S. and Satyanarayana, C. V.} } @article { ISI:000233846100021, title = {Synthesis, characterization, electronic structure, and photocatalytic activity of nitrogen-doped TiO2 nanocatalyst}, journal = {Chemistry of Materials}, volume = {17}, number = {25}, year = {2005}, month = {DEC}, pages = {6349-6353}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Nitrogen-doped TiO2 (N-TiO2)) nanocatalyst with spherical shape and homogeneous size has been synthesized through a chemical method using TiCl3 as precursor. The light absorption onset shifts from 380 nm on pure TiO2 to the visible region at 550 nm with N-TiO2. A clear decrease in the band gap and the nitrogen 2p states on the top of the valence band on N-TiO2 (compared to TiO2) is deduced from the optical absorption spectroscopy results. The chemical nature of N has been evolved as N-Ti-O in the anatase TiO2 lattice as identified by X-ray photoelectron spectroscopy (XPS). Photocatalytic decomposition of methylene blue has been carried out both in the UV and in the visible region and N-TiO2 shows higher activity than the Degussa P25 TiO2 photocatalyst in the visible region.

}, issn = {0897-4756}, doi = {10.1021/cm052047v}, author = {Sathish, M and Viswanathan, B and Viswanath, RP and Gopinath, Chinnakonda S.} } @article { ISI:000239326400010, title = {On the {\textquoteleft}{\textquoteleft}Active spacer and stabilizer{\textquoteright}{\textquoteright} role of Zn in Cu1-xZnxFe2O4 in the selective mono-N-methylation of aniline: XPS and catalysis study}, journal = {Journal of Catalysis}, volume = {241}, number = {1}, year = {2006}, month = {JUL}, pages = {83-95}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

A systematic catalytic methylation study on ferrospinel materials led to the selective production of N-methylaniline (NMA) with Cu1-xZnxFe2O4. Aniline methylation was carried out on Cu1-xZnxFe2O4 with a feed composition of CH3OH:PhNH2:H2O = 3:1:1 at 513-633 K. NMA was formed selectively on all of the catalyst compositions, with trace amounts of secondary products under most of the conditions. Cu0.5Zn0.5Fe2O4 composition showed high catalytic activity and stability up to 100 h. Although the Cu2+ was responsible for methylation activity, Zn2+ enhanced the overall stability of the catalyst system. XPS investigations revealed that the degree of Cu2+ reduction decreased dramatically from x = 0.05/0.25 to 0.5/0.75 on spent catalysts. TPR studies indicated that the reducibility of Cu2+ decreased from fully reducible at 523 K with Cu-rich compositions to partially reducible at 573 K on x = 0.5. Stable activity observed on Cu0.5Zn0.5Fe2O4 can be attributed to the highly heterogeneous distribution of metal ions. This heterogeneous distribution indicates an important role of zinc, likely as an {\textquoteleft}{\textquoteleft}active spacer cum stabilizee{\textquoteright} that hinders the reduction of active Cu2+ and contributes to prolonged activity. (c) 2006 Elsevier Inc. All rights reserved.

}, keywords = {Aniline, Ferrite, N-methylaniline, N-methylation, spacer, stabilizer, surface distribution, TPR, XPS}, issn = {0021-9517}, doi = {10.1016/j.jcat.2006.04.010}, author = {Vijayaraj, Munusamy and Gopinath, Chinnakonda S.} } @article { ISI:000241492900018, title = {Autoreduction of cyanoferrate(III) ions in a polymer electrolyte membrane: all solid state electrochemical and spectroscopic investigations}, journal = {Chemistry of Materials}, volume = {18}, number = {22}, year = {2006}, month = {OCT}, pages = {5244-5252}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

The effect of dielectric confinement on proton-coupled electron-transfer behavior and spectroscopic properties of cyanoferrate ions in a polymer electrolyte membrane (Nafion) has been investigated in an {\textquoteleft}{\textquoteleft}all-solid-state{\textquoteright}{\textquoteright} electrochemical cell, using techniques such as cyclic voltammetry, zero current chronopotentiometry, electrochemical impedance, diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), UV-visible spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron spin resonance spectroscopy (ESR). From the above investigations, we found that cyanoferrate(III) ions undergo autoreduction in the ionomer matrix, for which a sulfonate-coupled mechanism has been proposed. This report demonstrates the effectiveness of the micellar interface in tuning the redox potential of the confined ions. A systematic analysis of the cyclic voltammetry and impedance data for the [Fe(CN)(6)](4)(-)- containing Nafion membrane enables the estimation of a standard rate constant for [Fe(CN) 6](4-) oxidation, k(o), as 5.44 x 10(-6) cm/s and a diffusion coefficient, D-o, as 1.3 x 10(-12) cm(2)/s. A similar calculation yields a value of 4.8 x 10(-12) cm(2)/s for the diffusion coefficient of protons and 9.1 x 10(-6) cm/s for the standard rate constant for hydrogen oxidation. The similarity in mass-transfer coefficients calculated for protons and [Fe(CN)(6)](4-) ions suggests a proton-coupled electron-transfer mechanism for the [Fe(CN)(6)](4-)/[Fe(CN)(6)](3-) couple. The results of the above investigations could have direct technological relevance for deciding catalyst materials having redox compatibility with the polymer electrolyte, especially in the preparation of catalyst-coated membranes (wherein the fuel-cell catalyst is directly coated onto the polymer membrane instead of on the carbon support).

}, issn = {0897-4756}, doi = {10.1021/cm061444i}, author = {Parthasarathy, Meera and Gopinath, Chinnakonda S. and Pillai, Vijayamohanan K.} } @article { ISI:000236523100094, title = {Comment on {\textquoteleft}{\textquoteleft}Photoelectron spectroscopic investigation of nitrogen-doped titania nanoparticles{\textquoteright}{\textquoteright}}, journal = {Journal of Physical Chemistry B}, volume = {110}, number = {13}, year = {2006}, month = {APR}, pages = {7079-7080}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, issn = {1520-6106}, doi = {10.1021/jp054495w {\textperiodcentered}}, author = {Gopinath, Chinnakonda S.} } @article { ISI:000240781100009, title = {Effect of spacer groups on the performance of MCM-41-supported platinum cluster-derived hydrogenation catalysts}, journal = {Journal of Catalysis}, volume = {242}, number = {2}, year = {2006}, month = {SEP}, pages = {332-339}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

MCM-41 was functionalized with (EtO)(3)SiCH2Cl, (MeO)(3)SiCH2CH2CH2Cl, and (CH3)Cl2SiCH2Cl. The functionalized materials were characterized by solid-state NMR (CPMAS, Si-29 and C-13) and XPS. The NMR data indicate that three new silicon environments were created by(EtO)(3)SiCH2Cl and (MeO)(3)SiCH2CH2CH2Cl, whereas with (CH3)Cl2SiCH2Cl, two new silicon environments were obtained. XPS results from Si 2p core level and the valence band from the material functionalized by (MeO)(3)Si(CH2)(3)Cl was found to be the same as that of the corresponding fresh catalyst (1a), in contrast to that of the materials functionalized by the other two silane reagents. After further functionalization with triethylamine, these materials were used as inorganic anion exchangers to support the cluster anion [Pt-12(CO)(24)](2-). Solid-state NMR (29Si, C-13, N-15) was used to establish the presence of the quaternary ammonium group in the cluster-supported species. Analogous materials were also created using fumed silica as the support, and all of the cluster-supported materials were tested as catalysts for the hydrogenation of methyl pyruvate, acetophenone, nitrobenzene, benzonitrile, ethylacetoacetate, 4-nitrotoluene, cyclohexanone, allyl alcohol, and styrene. The best activity was obtained for the catalyst that had MCM-41 as the support and chloropropyl as the spacer group. TEM showed that the supports and the spacer groups had observable effects on the platinum crystallite size of the catalysts. (c) 2006 Elsevier Inc. All rights reserved.

}, keywords = {functionalized inorganic oxides, hydrogenation catalysts, MCM-41, platinum carbonyl cluster, Solid-state NMR, spacer groups, XPS}, issn = {0021-9517}, doi = {10.1016/j.jcat.2006.06.016}, author = {Maity, Niladri and Basu, Susmit and Mapa, Maitri and Rajamohanan, Pattuparambil R. and Ganapathy, Subramanian and Gopinath, Chinnakonda S. and Bhaduri, Sumit and Lahiri, Goutam Kumar} } @article { ISI:000238412100062, title = {Exfoliation-induced nanoribbon formation of poly(3,4-ethylene dioxythiophene) PEDOT between MoS2 layers as cathode material for lithium batteries}, journal = {Journal of Power Sources}, volume = {156}, number = {2}, year = {2006}, month = {JUN}, pages = {615-619}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

A new type of layered nanocomposite synthesized by delaminated MoS2 nanosheets and poly(3,4-ethylenedioxythiophene) (PEDOT) are restacked to produce alternate polymer nanoribbons between layers Of MoS2 with an interlayer distance of similar to 1.38 nm. The unique properties of resulting nanocomposite are investigated by powder XRD, XPS, SEM, TEM, and four-probe conductivity measurements. The obtained nanocomposite can be used as a cathode material for a small power rechargeable lithium battery as demonstrated by the electrochemical insertion of lithium into the PEDOT/MoS2 nanocomposite. A significant enhancement in the discharge capacity (100 mAh g(-1)) is observed compared with that (40 mAh g(-1)) for MoS2. (c) 2005 Elsevier B.V All rights reserved.

}, keywords = {cathode material, lithium batteries, MoS2, organic-inorganic nanocomposite, PEDOT-nanoribbons}, issn = {0378-7753}, doi = {10.1016/j.jpowsour.2005.06.022}, author = {Murugan, A. Vadivel and Quintin, M. and Delville, M. H. and Campet, Guy and Gopinath, Chinnakonda S. and Vijayamohanan, K.} } @article { ISI:000241248000088, title = {Highly efficient organic-inorganic poly(3,4-ethylenedioxythiophene)-molybdenum trioxide nanocomposite electrodes for electrochemical supercapacitor}, journal = {Journal of Applied Physics}, volume = {100}, number = {7}, year = {2006}, month = {OCT}, pages = {Article No. 074319}, publisher = {AMER INST PHYSICS}, type = {Article}, address = {CIRCULATION \& FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA}, abstract = {

In this paper, we report a highly efficient organic-inorganic nanocomposite electrode with enhanced double layer capacitance, which has been synthesized using 3,4-ethylenedioxythiophene and crystalline molybdenum trioxide (MoO3) in the presence of an external oxidizing agent. The interlayer spacing of MoO3 upon intercalation expands from 6.93 to 13.46 A and is followed by an exfoliation and restacking process. The resulting nanocomposite is characterized by powder x-ray diffraction, scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy, and four probe conductivity measurements. The application potential of this nanocomposite as an electrode material for electrochemical supercapacitors has been investigated, highlighting the unusual enhancement of double layer capacitance of poly(3,4-ethylenedioxythiphene) (PEDOT-MoO3) nanocomposites (similar to 300 F g(-1)) compared to that of pristine MoO3 (similar to 40 mF g(-1)). The improved electrochemical performance is attributed to the intercalation of electronically conducting PEDOT between MoO3 layers with enhanced bidimensionality and an increase in the surface area. (c) 2006 American Institute of Physics.

}, issn = {0021-8979}, doi = {10.1063/1.2356788}, author = {Murugan, A. Vadivel and Viswanath, Annamraju Kasi and Gopinath, Chinnakonda S. and Vijayamohanan, K.} } @article { ISI:000236419800016, title = {MCM-41-supported platinum carbonyl cluster-derived catalysts for asymmetric and nonasymmetric hydrogenation reactions}, journal = {Journal of Catalysis}, volume = {239}, number = {1}, year = {2006}, month = {APR}, pages = {154-161}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

Anionic platinum carbonyl Cluster ([Pt-12(CO)(24)](2-)) was ion-paired with the 3-chloropropyltrimethoxysilyl-ammonium group chemically bound to the surface of MCM-41. The materials undergo quick decarbonylation and have been characterized before decarbonylation by IR and UV-vis spectroscopy and after decarbonylation by XPS and TEM. They have been used as catalysts for the hydrogenations of methyl pyruvate, acetophenone, nitrobenzene, benzonitrile, and ethylacetoacetate. The support and the quaternary ammonium groups have significant effects on surface platinum concentration, crystallite size, and observed activity. In the hydrogenation of the prochiral substrates methyl pyruvate or acetophenone, the cinchonidine-based catalyst gives significant enantioselectivity under optimum conditions. A kinetic model that includes an enantioselective product-formation step and a hydrogen pressure-dependent step for the deactivation of the enantioselective sites gives reasonable agreement between predicted and observed enantioselectivity. The model is also in accordance with the XPS and TEM data. (c) 2006 Elsevier Inc. All rights reserved.

}, keywords = {asymmetric/non-asymmetric catalysis, Enantioselectivity, functionalized MCM-41, hydrogenation catalysts, platinum carbonyl cluster}, issn = {0021-9517}, doi = {10.1016/j.jcat.2006.01.032}, author = {Basu, Susmit and Mapa, Maitri and Gopinath, Chinnakonda S. and Doble, Mukesh and Bhaduri, Sumit and Lahiri, Goutam Kumar} } @article { ISI:000241591900007, title = {Selective ortho-methylation of phenol with methanol over copper manganese mixed-oxide spinel catalysts}, journal = {Journal of Catalysis}, volume = {243}, number = {2}, year = {2006}, month = {OCT}, pages = {278-291}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

Methylation of phenol with methanol as an alkylating agent to produce 2,6-xylenol was investigated over copper manganese mixed oxide spinels, CuxMn3-xO4 (x = 0, 0.25, 0.5, 0.75, and 1) prepared through co-precipitation. The catalytic activity strongly depends on the composition, acid-base properties, and structural stability. Various parameters, including catalyst composition, reaction temperature, feed composition, and durability of the catalyst during methylation, were investigated. Mainly o-cresol and 2,6-xylenol, along with small amounts of mesitol, were found in the product. A high ortho-selectivity of 100\%, with 2,6-xylenol selectivity of 74\%, was observed over Cu0.25Mn2.75O4 at 673 K. These catalysts were investigated using various techniques, including BET surface area, XRD, DRS UV-vis, TPD of NH3 and CO2, TPR, and X-ray photoemission spectroscopy (XPS). Powder XRD of the catalysts revealed the formation of copper-manganese spinels with hausmannite (Mn3O4) tetragonal structure, for x = 0-0.5, whereas an increase in copper content (x \> 0.5) led to the formation of cubic Cu1.5Mn1.5O4 phase. DRS UV-vis, and FTIR further supported the changes in structural phases observed by XRD. Temperature-programmed desorption Of CO2 and NH3 showed that the catalysts have strong basicity along with weak acidity when x = 0 and 0.25. XPS and XAES analysis revealed the presence of only Cu2+ ions in fresh sample with x = 0.25, whereas for x = 1.0, both Cu1+ and Cu2+ were observed. The deactivation of the catalysts is attributed to structural changes occurring during the reaction. Catalytic activity is correlated with structure, as well as with acid-base properties. (c) 2006 Elsevier Inc. All rights reserved.

}, keywords = {2, 6-xylenol, acidity-basicity, copper-manganese oxides, ortho-alkylation, phenol methylation, Spinels}, issn = {0021-9517}, doi = {10.1016/j.jcat.2006.07.014}, author = {Reddy, A. Satyanarayana and Gopinath, Chinnakonda S. and Chilukuri, Satyanarayana V.} } @article { ISI:000241591900017, title = {Selective production of methoxyphenols from dihydroxybenzenes on alkali metal ion-loaded MgO}, journal = {Journal of Catalysis}, volume = {243}, number = {2}, year = {2006}, month = {OCT}, pages = {376-388}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

Selective O-methylation of dihydroxybenzenes (DHBs; catechol, resorcinol, and hydroquinone) to methoxyphenols (MPs) was carried out with dimethylcarbonate on MgO and alkali metal ion (Li, K, and Cs)-loaded MgO between 523 and 603 K. Catalytic activity and product selectivity varied with respect to DHB substrates. Selectivity for O-methylated products increased with increasing basicity of alkali ions; however, K-MgO showed high and stable activity toward MPs. Selectivity for MPs obtained from three substrates increased in the following order: catechol \< resorcinol \< hydroquinone. The mode of interaction of substrates on the catalysts surface influenced reactivity and product selectivity. It is likely that the low reaction temperatures used (\< 603 K) kinetically control and favor high MP selectivity from DHBs. Calcined and spent catalysts were characterized by XRD, surface area, SEM, thermal analysis, NMR, and XPS. XRD analysis revealed the formation of alkali oxide phases on alkali-loaded MgO. Crystallite size and surface area of the catalysts decreased after methylation reactions, except on K-MgO. TGA showed 4060 wt\% coke deposition on spent catalysts. TGA in N-2 followed by air and C-13 CP-MAS NMR measurements indicated the nature of deposited carbon to be molecular species, graphite, MgCO3 and polyaromatics. XPS revealed the nature and availability of active sites on the spent catalysts, as well as the same changes with reaction conditions and correlated with catalytic activity. (c) 2006 Elsevier Inc. All rights reserved.

}, keywords = {alkali-loaded MgO, dihydroxybenzene, K-MgO, methoxyphenol, MgO, O-methylation, thermal analysis, XPS}, issn = {0021-9517}, doi = {10.1016/j.jcat.2006.08.009}, author = {Vijayaraj, Munusamy and Gopinath, Chinnakonda S.} } @article { ISI:000241912700017, title = {Electrochromic device (ECD) cell characterization on electron beam evaporated MoO3 films by intercalating/deintercalating the H+ ions}, journal = {Current Applied Physics}, volume = {7}, number = {1}, year = {2007}, month = {JAN}, pages = {76-86}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Thin films of molybdenum oxide (MoO3) is one of the most interesting layered intercalation materials because of its excellent application in solid state batteries, large-area window and display systems. In recent years there has been considerable interest in variable transmittance electrochromic devices (ECD) based on Li+, H+ and K+ intercalation in transition metal oxide (MoO3) thin films. In the present investigation, thin films of MoO3 were prepared by electron beam evaporation technique on microscopic glass and fluorine doped tin oxide (FTO) coated glass substrates for the application in electrochromic device cells. The compositional stoichiometry of the films was studied by X-ray photoelectron spectroscopy (XPS). The electrochromic nature of the films has been analyzed by inserting H+ ions from the H2SO4 electrolyte solution using the cyclic-voltammetry (CV) technique. We studied the electrochromic device cells (ECD) incorporating an evaporated MoO3 thin films as electrochromic layers. The devices exhibit good optical properties with low transmittance values in the colored state, which make them suitable for large-area window applications. The maximum coloration efficiency of the cell was observed at about 70 cm(2)/c. (c) 2005 Published by Elsevier B.V.

}, keywords = {coloration efficiency, electrochromic device cells, molybdenum oxide thin films, optical density, stoichiometry}, issn = {1567-1739}, doi = {10.1016/j.cap.2005.12.001}, author = {Sivakumar, R. and Gopinath, Chinnakonda S. and Jayachandran, M. and Sanjeeviraja, C.} } @article { ISI:000250234900007, title = {Fabrication of an effusive molecular beam instrument for surface reaction kinetics - CO oxidation and NO reduction on Pd(111) surfaces}, journal = {Catalysis Letters}, volume = {119}, number = {1-2}, year = {2007}, month = {NOV}, pages = {50-58}, publisher = {SPRINGER}, type = {Article}, address = {233 SPRING STREET, NEW YORK, NY 10013 USA}, abstract = {

A simple molecular beam instrument (MBI) was fabricated for measuring the fundamental parameters in catalysis such as, sticking coefficient, transient and steady state kinetics and reaction mechanism of gas/vapor phase reactions on metal surfaces. Important aspects of MBI fabrication are given in detail. Nitric oxide (NO) decomposition and NO reduction with carbon monoxide (CO) on Pd(111) surfaces were studied. Interesting results were observed for the above reactions and they support the efficiency of the MBI to derive the fundamental parameters of adsorption and catalysis. Sustenance of CO oxidation at 400 K is dependent mostly on the absence of CO-poisoning; apparently, CO + O recombination is the rate determining step \<= 400 K. NO adsorption measurements on Pd(111) surface clearly indicating a typical precursor kinetics. Displacement of the chemisorbed CO by NO on Pd(111) surfaces was observed directly with NO + CO beams in the transient kinetics. It is also relatively easy to identify the rate-determining step directly from the MBI data and the same was demonstrated for the above reactions.

}, keywords = {carbon monoxide, catalysis, kinetics, molecular beam, nitric oxide, Pd(111)}, issn = {1011-372X}, doi = {10.1007/s10562-007-9184-8}, author = {Thirunavukkarasu, Kandasamy and Gopinath, Chinnakonda S.} } @article { ISI:000245534900008, title = {Selective mono-N-methylation of aniline substrates on Cu1-xZnxFe2O4}, journal = {Applied Catalysis A-General}, volume = {320}, year = {2007}, month = {MAR}, pages = {64-68}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Selective mono-N-methylation of substituted anilines (o-, m- and p-toluidines, 2,6-xylidine, p-anisidine and p-aminoacetophenone) was carried out with methanol as methylating agent under vapor phase reaction conditions on Cu1-xZnxFe2O4 systems. The catalytic reactions with each aniline substrate were carried out at optimum reaction conditions (MeOH:anilines:water = 3: 1: 1, space velocity = 3.58 h(-1)) between 543 and 603 K. The presence of a ring-directing group did not have any significant influence on the N-methylaniline(s) selectivity, which remains very high; the same initial conversion/yield was observed for at least 11 h. Electronic effects due to different groups in the above aniline substrates influence the reactivity of the substrates in terms of conversion and yield. Toluidine reactivity varies with respect to the position (ortho, meta and para) of the methyl group on the phenyl ring. Para-substituted anilines (p-toluidine and p-anisidine) exhibit comparable catalytic activity, while p-aminoacetophenone shows higher conversion. The perpendicular orientation of toluidine substrates on catalyst surfaces influences the conversion and N-methyltoluidine yield. Increased crowding at ortho-position and hence steric hindrance (aniline \> o-toluidine \> 2,6-xylidine) restrict the substrates interaction with the catalyst surface, and 2,6-xylidine shows no reactivity. The best catalytic activity observed with Cu0.5Zn0.5Fe2O4 was due to a heterogeneous distribution of metal ions on the surface with Zn serving as active spacer group as well as methyl species source. (c) 2007 Elsevier B.V. All rights reserved.

}, keywords = {mono-N-methylation, N-methylaniline, N-methylation, selective N-methvlation, spinel}, issn = {0926-860X}, doi = {10.1016/j.apcata.2006.12.016}, author = {Vijayaraj, Munusamy and Gopinath, Chinnakonda S.} } @article { ISI:000255305200006, title = {Effect of fuel and its concentration on the nature of Mn in Mn/CeO2 solid solutions prepared by solution combustion synthesis}, journal = {Acta Materialia}, volume = {56}, number = {7}, year = {2008}, month = {APR}, pages = {1461-1472}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, type = {Article}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

Nano and microcrystalline, Mn/CeO2 solid solutions (5 mol.\% Mn) have been prepared by solution combustion synthesis using urea, glycine or polyethylene glycol (PEG) as fuel. The nature of the fuel and its concentration (fuel to metal mole ratio, F/M have a strong influence on the physical and chemical characteristics of the resulting Mn/CeO2 solid solutions. The variations in the physicochemical properties are attributed to differences in (i) the adiabatic/real flame temperature realized with these fuels at different F/M ratios; (ii) the sustenance of the temperature or the quenching effect of the fuel at higher F/M ratios; (iii) combustion or decomposition of the precursors as the main course of the reaction; and (iv) the generation of gaseous products during combustion. Since the addition of the fuel to the initial precursor solution does not change the pH of the medium, the differences in the type of Mn species formed are mainly attributed to the combustion process. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

}, keywords = {Combustion synthesis, Mn-ceria, Nanocomposites, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS)}, issn = {1359-6454}, doi = {10.1016/j.actamat.2007.11.035}, author = {Murugan, B. and Ramaswamy, A. V. and Srinivas, D. and Gopinath, Chinnakonda S. and Ramaswamy, Veda} } @article { ISI:000256920000046, title = {MCM-41-supported organometallic-derived nanopalladium as a selective hydrogenation catalyst}, journal = {Journal of Physical Chemistry C}, volume = {112}, number = {25}, year = {2008}, month = {JUN}, pages = {9428-9433}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Palladium nanocatalysts have been prepared by anchoring (eta(3)-C(3)H(5))(2)Pd(2)Cl(2) onto dian-tine-functionalized MCM-41 supports followed by reaction with hydrogen under catalytic conditions. The catalyst precursor and used catalyst have been studied by solid-state NMR ((13)C, (29)Si), XPS, and TEM. The organometallic-derived catalyst exhibits the best performance (activity and selectivity) to date toward the selective hydrogenation of industrially relevant o- and m-chloronitrobenzene to the corresponding chloroaniline derivatives and is distinctly superior to 5\% Pd/C. Grazing angle XPS studies reveal that conversion of the tethered molecular species to the nanoparticles of palladium produces a core-shell nanostructure.

}, issn = {1932-7447}, doi = {10.1021/jp8007656}, author = {Maity, Niladri and Rajamohanan, Pattuparambil R. and Ganapathy, Subramanian and Gopinath, Chinnakonda S. and Bhaduri, Sumit and Lahiri, Goutam Kumar} } @article { ISI:000257904900015, title = {MCM-41-supported ruthenium carbonyl cluster-derived catalysts for asymmetric hydrogenation reactions}, journal = {Applied Catalysis A-General}, volume = {344}, number = {1-2}, year = {2008}, month = {JUL}, pages = {124-130}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

{The anionic ruthenium carbonyl cluster [Ru-4(mu-H)(3)(CO)(12)](-) has been ion-paired with (3-chloropropyl)-trimethoxysilyl-cinchonidium or sparteinium groups chemically bound to the surfaces of MCM-41 [(MCM-41-)(-O)(3)SiCH2CH2CH2NR3+Cl-

}, keywords = {asymmetric catalysis, functionalized MCM-41, hydrogenation catalysts, nanocatalyst, ruthenium carbonyl cluster}, issn = {0926-860X}, doi = {10.1016/j.apcata.2008.04.009}, author = {Indra, Arindam and Basu, Susmit and Kulkarni, Dhanashree G. and Gopinath, Chinnakonda S. and Bhaduri, Sumit and Lahiri, Goutam Kumar} } @article { ISI:000264978500019, title = {Applications of a high performance platinum nanocatalyst for the oxidation of alcohols in water}, journal = {Green Chemistry}, volume = {11}, number = {4}, year = {2009}, month = {FEB}, pages = {554-561}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Nanoparticles of platinum (NP-Pt), have been synthesized by supporting high nuclearity anionic carbonyl cluster (Chini cluster) on a water soluble anion exchanger, and the performance of this material, 1, as an oxidation catalyst for alcohols in water has been studied. The E-factor for the synthesis of NP-Pt by this method has been calculated and compared with that of other NP-Pt recently reported in the literature. With 1 as a catalyst, oxidations of a variety of primary and secondary alcohols by dioxygen are achieved and high turnover numbers and selectivities are obtained. The performances of 1 in the oxidation of benzyl alcohol and 1-phenylethanol are compared with those of three other platinum catalysts. These are platinum nanoparticles 2 prepared by the hydrogen reduction of [PtCl6](2-) supported on the same water soluble polymer, 5\% Pt on carbon, and 5\% Pt on alumina, designated as 3 and 4, respectively. 1 has been found to be considerably more active than 2- 4 and also other reported water soluble platinum nanocatalysts. After many turnovers (similar to 1000 and similar to 165 for benzyl alcohol and 1-phenyl ethanol, respectively) partial deactivation (similar to 40\%) is observed, but the deactivated catalyst can be fully regenerated by treatment with dihydrogen. The TEM data of fresh, deactivated and regenerated 1 show a correlation between the particle size and activity. A mechanism consistent with this and other experimental observations including XPS data is proposed.

}, issn = {1463-9262}, doi = {10.1039/b815948c}, author = {Maity, Prasenjit and Gopinath, Chinnakonda S. and Bhaduri, Sumit and Lahiri, Goutam Kumar} } @article { ISI:000262605200024, title = {Combustion synthesis of triangular and multifunctional ZnO1-xNx (x <= 0.15) materials}, journal = {Chemistry of Materials}, volume = {21}, number = {2}, year = {2009}, month = {JAN}, pages = {351-359}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

The preparation and characterization of multifunctional ZnO1-xNx (x \<= 0.15) via a simple solution combustion method is reported. ZnO1-xNx exhibits visible light absorption, thermal stability, nanometer-/ micrometer-sized triangular particles, and catalytic properties. X-ray diffraction studies of ZnO1-xNx, demonstrate that the lattice oxygen in ZnO is replaced by nitrogen without any major change in the wurtzite structure; however, charge compensation occurs, because of interstitial Zn atoms, as well as oxygen vacancies. Microscopic studies reveal the dominance of nanometer- and micrometer-sized triangles of ZnO1-xNx. UV-visible and Raman spectra indicate a midgap state, derived from N 2p states, and direct Zn-N interaction, respectively. Secondary ion mass spectrometry studies show the presence of N and ZnN species in the bulk and support the direct Zn-N interaction. Electron paramagnetic resonance (EPR) studies indicate the presence of a small amount of defects. Photocatalytic decomposition of rhodamine B, and anisole acylation at room temperature, highlights the effectiveness of ZnO1-xNx to catalysis applications. The aforementioned multifunctional characteristics suggest that ZnO1-xNx might be used in place of conventional ZnO for better control and that it might be explored for further applications in catalysis and optoelectronics.

}, issn = {0897-4756}, doi = {10.1021/cm803048h}, author = {Mapa, Maitri and Gopinath, Chinnakonda S.} } @article { ISI:000271756700023, title = {Electronic decoupling of surface layers from bulk and its influence in oxidation catalysis: a molecular beam study}, journal = {Applied Surface Science}, volume = {256}, number = {2}, year = {2009}, note = {2nd International Conference on Physics at Surfaces and Interfaces (PSI2009), Puri, INDIA, FEB 23-27, 2009}, month = {OCT}, pages = {443-448}, publisher = {Inst Phys; Indian Assoc Cutivat Sci}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Interactions between oxygen and Pd-surfaces have important implications, especially towards oxidation reactions, and influence of subsurface oxygen to oxidation reactions is the focus of the present study. In our efforts to understand the above aspects, CO oxidation reactions have been carried out with mixed molecular beam (MB), consisting CO and O(2), on Pd(1 1 1) surfaces under a wide variety of conditions (T = 400-900 K, CO: O(2) = 7: 1 to 1: 10). A new aspect of the above reaction observed in the transient kinetics regime is the evidence for oxygen diffusion into Pd subsurface layers, and its significant influence towards CO oxidation at high temperatures (\>= 600 K). Interesting information derived from the above studies is the necessity to fill up the subsurface layers with oxygen atoms to a threshold coverage (theta(O-sub)), above which the reactive CO adsorption occurs on the surface and simultaneous CO(2) production begins. There is also a significant time delay (G) observed between the onset of oxygen adsorption and CO adsorption (and CO(2) production). Above studies suggest an electronic decoupling of oxygen covered surface and subsurface layers, which is slightly oxidized, from the metallic bulk, which induces CO adsorption at high temperatures and simultaneous oxidation to CO(2). (C) 2009 Elsevier B.V. All rights reserved.

}, keywords = {Electronic decoupling, heterogeneous catalysis, molecular beam, Oxidation, Pd(111), Subsurface diffusion}, issn = {0169-4332}, doi = {10.1016/j.apsusc.2009.06.107}, author = {Thirunavukkarasu, Kandasamy and Nagarajan, Sankaranarayanan and Gopinath, Chinnakonda S.} } @article { ISI:000268138200061, title = {Electronic structure and catalytic study of solid solution of GaN in ZnO}, journal = {Chemistry of Materials}, volume = {21}, number = {13}, year = {2009}, month = {JUL}, pages = {2973-2979}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Solid solutions of GaN in ZnO (Zn1-zGaz)(O1-xNx) (x and z \<= 0.15) have been prepared by simple solution combustion method, Except for minor changes in the lattice contraction, no significant change in the Wurtzite structure was observed. Raman and secondary ion mass spectrometry results show the direct Zn-N and Ga-N bonds in (Zn1-zGaz)(O1-xNx). Visible light absorption and XPS results demonstrate that N 2p states of nitride occupy the states above the O 2p valence band, and hence a change in optical band gap reduction occurs to similar to 2.5 eV from 3.37 eV for ZnO. Significant nitrogen fixation catalytic activity through NH3 formation has been observed at ambient pressure oil virgin (Zn1-zGaz)(O1-xNx) material, indicating its potential as a catalyst.

}, issn = {0897-4756}, doi = {10.1021/cm900682q}, author = {Mapa, Maitri and Thushara, K. S. and Saha, Biswajit and Chakraborty, Purushottam and Janet, C. M. and Viswanath, R. P. and Nair, C. Madhavan and Murty, K. V. G. K. and Gopinath, Chinnakonda S.} } @article { ISI:000262582400008, title = {Kinetic evidence for the influence of subsurface oxygen on palladium surfaces towards CO oxidation at high temperatures}, journal = {Chemistry-an Asian Journal}, volume = {4}, number = {1}, year = {2009}, month = {OCT}, pages = {74-80}, publisher = {WILEY-V C H VERLAG GMBH}, address = {PO BOX 10 11 61, D-69451 WEINHEIM, GERMANY}, abstract = {

Transient state kinetics of the catalytic oxidation of CO with 0, on Pd-surfaces has been measured under isothermal conditions by using a molecular beam approach. Systematic studies were carried out as a function of reaction temperature and CO+O(2) composition. With sufficient kinetic evidence, we have demonstrated the positive influence of subsurface oxygen towards CO-adsorption and oxidation to CO, at high temperatures (600-900 K) on Pd-surfaces, and the likely electronic nature of the surface changes with oxygen in the subsurface. These studies also provide a direct proof for CO-adsorption with a significantly reactive sticking coefficient at high temperatures on Pd-surfaces exhibiting a significant subsurface O-coverage.

}, keywords = {Adsorption, kinetics, Oxidation, Palladium, surface analysis}, issn = {1861-4728}, doi = {10.1002/asia.200800278}, author = {Gopinath, Chinnakonda S. and Thirunavukkarasu, Kandasamy and Nagarajan, Sankaranarayanan} } @article { ISI:000266093800005, title = {MgCl2 center dot 4(CH3)(2)CHOH: a new molecular adduct and super active polymerization catalyst support}, journal = {Journal of Physical Chemistry C}, volume = {113}, number = {20}, year = {2009}, month = {MAY}, pages = {8556-8559}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

A new molecular adduct, MgCl(2 center dot)4(CH3)(2)CHOH, has been synthesized and characterized for structural aspects and demonstrated for super active ethylene polymerization activity with TiCl4 to ultrahigh molecular weight polyethylene in high yield.

}, issn = {1932-7447}, doi = {10.1021/jp9026546}, author = {Thushara, K. S. and Mathew, Renny and Ajithkumar, Thalasseril G. and Rajamohanan, P. R. and Bhaduri, Sumit and Gopinath, Chinnakonda S.} } @article { ISI:000266447600055, title = {Nitric oxide reduction with ethanol on palladium surfaces: a molecular beam study}, journal = {Journal of Physical Chemistry C}, volume = {113}, number = {22}, year = {2009}, month = {JUN}, pages = {9814-9819}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Nitric oxide (NO) reduction with ethanol has been carried out with molecular beam instruments in order to understand the influence of ethanol blended gasoline on NO reduction. Maximum NO reduction and nitrogen production was observed between 500 and 600 K. Oxidation products, CO, CO(2), and H(2)O were also observed. Beam switching experiments have been performed between fuel-rich and fuel-lean compositions to demonstrate that the NO reduction can be managed under net oxidizing conditions on Pd surfaces. Nitrogen production only occurs transiently on the relatively clean Pd surface in the oxygen-rich condition due to slow build up and blockage of the reaction by surface oxygen atoms. This shows the need to maintain relatively oxygen free surfaces to manage NO reduction under net-oxidizing conditions by beam oscillation between fuel-rich and fuel-lean compositions.

}, issn = {1932-7447}, doi = {10.1021/jp902017c}, author = {Nagarajan, Sankaranarayanan and Thirunavukkarasu, Kandasamy and Gopinath, Chinnakonda S. and Counsell, Jonathan and Gilbert, Lee and Bowker, Michael} } @article { ISI:000263073800056, title = {N,S-Co-doped TiO2 Nanophotocatalyst: synthesis, electronic structure and photocatalysis}, journal = {Journal of Nanoscience and Nanotechnology}, volume = {9}, number = {1, SI}, year = {2009}, month = {JAN}, pages = {423-432}, publisher = {AMER SCIENTIFIC PUBLISHERS}, address = {26650 THE OLD RD, STE 208, VALENCIA, CA 91381-0751 USA}, abstract = {

N,S-co-doped anatase-phase TiO2 (N,S-TiO2) nanophotocatalysts were prepared from either benzothiazoline or aminothiol with titanium isopropoxide followed by a systematic thermal decomposition. The chemical nature of S and N in N,S-TiO2 have been identified by XPS to be sulfate and NO-like, respectively. A significant band broadening and red-shift in the UV-visible absorption spectrum of N,S-TiO2 suggests a band gap reduction compared to TiO2. A maximum band-gap narrowing of 0.22 +/- 0.02 eV was observed on N,S-TiO2. Higher energy width observed on N,S-TiO2 is in contrast to 0.13 eV from N-doped TiO2 indicating the sulfate-like species might play a major role in narrowing the band-gap to a Higher level. It is confirmed that the oxidation of N and S to NO and SO42- occurs in the final stage of preparation of N,S-TiO2, during calcination in air. It is predicted that the oxygen associated with sulfate and NO structural features could be crucial in bringing down the energy gap and red shift in optical absorption and the role of sulfur is to facilitate the above. Photocatalytic decomposition of methylene blue has been carried out on N,S-TiO2 shows higher activity than the commercial TiO2 in the visible region. However, sulfate species seems to enhance the activity of N,S-TiO2 marginally compared to N-TiO2, and possible suggestions are given to improve the same.

}, keywords = {nitrogen, Photocatalyst, Sulfur, TiO2, Visible Light Absorption}, issn = {1533-4880}, doi = {10.1166/jnn.2009.J095}, author = {Sathish, M. and Viswanath, R. P. and Gopinath, Chinnakonda S.} } @article { ISI:000265529700071, title = {Revisit to carbon monoxide oxidation on Pd(111) surfaces}, journal = {Journal of Physical Chemistry C}, volume = {113}, number = {17}, year = {2009}, month = {APR}, pages = {7385-7397}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Carbon monoxide (CO) oxidation on Pd(111) surfaces has been studied by molecular beam methods with mixed molecular beams (CO + O(2)) between 400 and 900 K and a CO:O(2) ratio of 7:1 to 1:10. A new aspect of the above reaction observed in the transient kinetics regime is the evidence for oxygen diffusion into Pd(111) subsurface layers and its significant influence toward CO oxidation at high temperatures (\>= 600 K). An overall influence of subsurface oxygen on the kinetics of the CO oxidation reaction is addressed. Interesting information derived from the above studies is the necessity to fill up the subsurface layers with oxygen atoms to a threshold coverage (theta(Osub)), above which the reactive CO adsorption occurs on the surface with subsequent CO(2) production. The above observation Was demonstrated with CO-rich reactant compositions (CO + O(2)) above 600 K via instant oxygen adsorption on Pd surfaces; however, onset of CO adsorption as well as CO(2) production occurs after a time delay. theta(Osub) and the time delay in CO adsorption (and CO(2) production) increase with increasing temperature and with CO-rich compositions. theta(Osub) was measured up to 0.3 monlayer (ML) between 500 and 850 K before the onset of CO adsorption; however, theta(Osub) increases from an insignificant value at \<500 K to 0.4 ML at 900 K with a pure O(2) beam. Onset of CO adsorption with a significant sticking coefficient on the Pd surfaces, that is, covered with significant subsurface oxygen, underscores a change in the electronic state of Pd surfaces toward mildly oxidized (or Pd(delta+)), and an electronic decoupling occurs between the bulk and the surface. The jellium model is invoked to demonstrate the changes observed. A similar observation with polycrystalline Pd surfaces suggests the defect sites is one of the channels for oxygen diffusion into subsurfaces. Initial sticking coefficient (s(0)) measurements demonstrate that there is no significant competition between CO and O(2) adsorption from the CO + O(2) mixture between 400 and 600 K, and indeed they are largely independent of each other. The maximum steady-state CO(2) formation rate was observed for a 1:1 CO/O(2) beam composition between 500 and 550 K. However, with a significant theta(Osub) the rate of CO(2) Production in the steady state is considerable even at high temperatures (700-850 K), and a broadening of the active CO oxidation regime to high temperature is observed with O(2)-rich compositions.

}, issn = {1932-7447}, doi = {10.1021/jp900890w}, author = {Nagarajan, Sankaranarayanan and Thirunavukkarasu, Kandasamy and Gopinath, Chinnakonda S.} } @article { ISI:000263073800048, title = {Template free synthesis of mesoporous TiO2 with high wall thickness and nanocrystalline framework}, journal = {Journal of Nanoscience and Nanotechnology}, volume = {9}, number = {1, SI}, year = {2009}, month = {JAN}, pages = {371-377}, publisher = {AMER SCIENTIFIC PUBLISHERS}, address = {26650 THE OLD RD, STE 208, VALENCIA, CA 91381-0751 USA}, abstract = {

A simple procedure to prepare nanocrystalline mesoporous titania (meso-TiO2) is reported without any templating agent and it possesses a high BET surface area and a large pore wall thickness (11.3 nm) than that of meso-TiO2 prepared by other methods. Nanocrystalline meso-TiO2 also has been synthesized with hexadecylamine template for comparison through known procedure. The meso-TiO2 materials were characterized by X-ray diffraction, FT-IR, UV-Vis absorbance spectra, thermal analysis, SEM, HRTEM and textural properties through N-2 adsorption-desorption isotherms. Spherical shape particles in a range of few hundred nanometers are obtained in the template free method. Above systematic characterization provides direct indications toward the mechanism of formation of meso-TiO2 in the template free method. A comparison of the physical and textural properties indicates a possibility of coarse-tuning of the textural characteristics of mesoporous TiO2 by adopting different preparation methods.

}, keywords = {Mesopore, Mesopore Formation, Template-Free, Thick Wall, titania}, issn = {1533-4880}, doi = {10.1166/jnn.2009.J019}, author = {Kulkarni, Dhanashree G. and Murugan, A. Vadivel and Viswanath, Annamraju Kasi and Gopinath, Chinnakonda S.} } @article { ISI:000275708600041, title = {Carbon dissolution and segregation in Pd(110)}, journal = {Journal of Physical Chemistry C}, volume = {114}, number = {11}, year = {2010}, month = {MAR}, pages = {5060-5067}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

The bulk-surface diffusion of carbon in Pd(110) has been investigated using Molecular beams to examine the clean-off of carbon with gas-phase oxygen. The dominant product of the reaction above 600 K is CO CO, is only produced at much lower temperatures where the lifetime of adsorbed CO is significant. The segregation from the bulk Only Occurs at a measurable rate at \>750 K, while loss of carbon into the bulk call occur at much lower temperatures. The reaction of carbon at high temperatures shows two regimes: (i) a non steady-state evolution of CO due to the clean-off of surface carbon already present on the surface, followed by (ii) a near steady-state reaction due to the continuous diffusion of carbon to the surface.

}, issn = {1932-7447}, doi = {10.1021/jp9108046}, author = {Bowker, Michael and Counsell, Jonathan and El-Abiary, Kareem and Gilbert, Lee and Morgan, Chris and Nagarajan, Sankaranarayanan and Gopinath, Chinnakonda S.} } @article { ISI:000284238000010, title = {Fabrication of homogeneous nanoparticle/nanoneedle BaTiO3 and Ba0.8Sr0.2TiO3 smooth thin films by simple dip coating}, journal = {International Journal of Nanotechnology}, volume = {7}, number = {9-12, SI}, year = {2010}, month = {DEC}, pages = {919-931}, publisher = {INDERSCIENCE ENTERPRISES LTD}, address = {WORLD TRADE CENTER BLDG, 29 ROUTE DE PRE-BOIS, CASE POSTALE 896, CH-1215 GENEVA, SWITZERLAND}, abstract = {

Ferroelectric BaTiO3 (BTO) and Ba0.8Sr0.2TiO3 (BSTO) thin film materials have been successfully prepared by sol-gel processing and simple dip coating on glass and silicon supports. Above thin films were characterised by x-ray diffraction (XRD), Raman spectroscopy, photoelectron spectroscopy, thermal analysis, atomic force microscopy (AFM) and spectroscopic ellipsometry. Phase identification of BaTiO3 and Ba0.8Sr0.2TiO3 was performed by XRD. XRD and Raman spectroscopy investigations demonstrate that thc Ba0.8Sr0.2TiO3 film exhibits tetragonal structure. AFM analysis demonstrates the elongated nanospherical particles on glass substrate and nanowires on silicon substrate, which represent a strong influence of the crystallinity of underlying substrate on the grain morphology in this technique. The thin films on both the substrates are uniformly coated without any pinhole to significant area (similar to 2.5 cm(2)), and this method might be extended to large area uniform coating. Spectroscopic ellipsometric measurements reveal the exact thickness, refractive index and extinction coefficient of the thin films.

}, keywords = {barium strontium titanate, barium titanate, dip coating, fabrication, ferroelectric material, large area coating, nanotechnology, thin film}, issn = {1475-7435}, author = {Saini, Mamta and Vivekanand, K. and Poddar, Pankaj and Murty, K. V. G. K. and Thushara, K. S. and Gopinath, Chinnakonda S.} } @article { ISI:000284018100044, title = {Facile synthesis of N- and S-incorporated nanocrystalline TiO2 and direct solar-light-driven photocatalytic activity}, journal = {Journal of Physical Chemistry C}, volume = {114}, number = {45}, year = {2010}, month = {NOV}, pages = {19473-19482}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Sulfur- and nitrogen-incorporated mesoporous TiO2 (SNT) nanocomposites have been synthesized by a template-free homogeneous coprecipitation technique. The above nanocomposites have been thoroughly characterized by physicochemical and spectroscopy methods to explore the structural, electronic, and optical properties. The photocatalytic activities of the catalysts were evaluated for the degradation of methyl orange and phenol under direct solar light. SNT shows about a 2-fold higher photocatalytic activity than singly N-doped or S-doped mesoporous TiO2 and 3-fold higher than Degussa P25. The higher activity might be attributed to the synergetic interaction of sulfate and nitrogen with the TiO2 lattice. N-Ti-O and O-Ti-N-O environments are responsible for a red shift, and the sulfate group on TiO2 acts as a cocatalyst, for increasing surface acidity as well as for sustaining the redox cycles for high stability.

}, issn = {1932-7447}, doi = {10.1021/jp1083345}, author = {Naik, Brundabana and Parida, K. M. and Gopinath, Chinnakonda S.} } @article { ISI:000273580700038, title = {Structure, electronic structure, optical, and dehydrogenation catalytic study of (Zn1-zInz)(O1-xNx) solid solution}, journal = {Chemistry of Materials}, volume = {22}, number = {2}, year = {2010}, month = {JAN}, pages = {565-578}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Indium and nitrogen codoping in ZnO leads to a solid solution of InN in ZnO with I composition of(Zn1-zInz)(O1-xNx). A simple solution combustion method has been adopted to prepare the above materials in less than 10 min with metal nitrates as the metal loll source and urea as fuel. With reference to ZnO, significant increase in lattice parameters was observed with increasing In-content. However, the In2O3 phase was Observed along with InN for]it content \>= 10\%. Optical absorption extended into the Visible region, at least LIP to 550 nm, demonstrates an effective reduction of optical band gap due to the formation of solid Solution. A new feature observed just above O2p valence band in X-ray photoelectron spectroscopy (XPS) suggests the creation of N 2p states from InN; the N Is core level XPS result too confirms nitride contribution. Raman spectroscopy and secondary ion mass spectrometry results show direct In-N, Zn-N. and In-N-Zn fragments in (Zn1-zInz)(O1-x,N-x). Catalytic activity explored for Oxidation of 2-butanol to ethyl methyl ketone demonstrates a high selectivity at 350 and 400 degrees C. All of the above characteristics suggest the multifunctional nature of (Zn1-zInz)(O1-xNx) and its potential for other applications.

}, issn = {0897-4756}, doi = {10.1021/cm903368r}, author = {Mapa, Maitri and Sivaranjani, Kumarsrinivasan and Bhange, Deu S. and Saha, Biswajit and Chakraborty, Purushottam and Viswanath, Annamraju Kasi and Gopinath, Chinnakonda S.} } @article { ISI:000293419700048, title = {Kinetics of nitric oxide adsorption on Pd(111) surfaces through molecular beam experiments: a quantitative study}, journal = {Journal of Physical Chemistry C}, volume = {115}, number = {31}, year = {2011}, month = {AUG}, pages = {15487-15495}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

A detailed kinetic picture derived by molecular beam studies of the adsorption-desorption of the NO/Pd(111) system is presented. Numerical simulations and detailed kinetic analysis show that the precursor state model of adsorption provides a valid picture of the sticking coefficient variation with surface coverage, especially at low temperatures. At higher temperatures, the precursor model gives way to the Langmuir molecular model of adsorption. All the parameters of the precursor state model have been quantified. Temperature programmed desorption (TPD) studies further show that there is a slight repulsive interaction between adsorbed NO molecules and there is only a negligible fraction of dissociated molecules on the surface for temperatures less than 500 K, as the Pd(111) surface is defect free. A Bragg-Williams (BW) lattice gas model with repulsive interactions, within the framework of mean field approach (MFA), is shown to describe the TPD spectra reasonably well.

}, issn = {1932-7447}, doi = {10.1021/jp203992r}, author = {Nagarajan, Sankaranarayanan and Thirunavukkarasu, Kandasamy and Gopinath, Chinnakonda S. and Prasad, Sudarsan D.} } @article { ISI:000292962900073, title = {Ligand dynamics controlled reverse spin cross over in bis pyrazolyl pyridine based Fe(II) complex cation with metallodithiolato anions with an example of a ferromagnetic 2:1 cocrystal of mixed Ni(III)/Ni(II) oxidation states}, journal = {Inorganica Chimica Acta}, volume = {374}, number = {1, SI}, year = {2011}, month = {AUG}, pages = {586-600}, publisher = {ELSEVIER SCIENCE SA}, address = {PO BOX 564, 1001 LAUSANNE, SWITZERLAND}, abstract = {

We report here the crystal and molecular structures of three compounds [FeL(2)] [Ni(mnt)(2)] (1), [FeL(2)](2) [Ni(mnt)(2)](3)center dot 2H(2)O (2) and [FeL(2)] [Cu(mnt)(2)]center dot 2CH(3)CN (3) where L = 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl) pyridine and mnt = maleonitriledithiolate, and their detailed spectroscopic and magnetic properties using variable temperature Mssbauer, EPR, susceptibility studies, along with room temperature electron spectroscopy for chemical analysis (ESCA) studies. The observed temperature dependant high spin/low spin (HS/LS) ratios of [FeL(2)](2+) cations in these lattices, exhibiting {\textquoteleft}reverse spin cross-over{\textquoteright} measured unequivocally by Mssbauer, have been interpreted as resulting from differing amount of {\textquoteleft}void space{\textquoteright} in the lattice, a measure of the ease of lattice dynamics originating from ligand L. Differential scanning calorimetric data points this HS/LS transition to order-disorder type of second order phase transitions. While trying to test this lattice dynamics controlled property of [FeL(2)](2+) cations an unusual behavior of cocrystallization of two planar complex anions of the same type in two different oxidation states, viz. [Ni(mnt)(2)](2) and [Ni(mnt)(2)] , was observed in [FeL(2)](2+) [Ni(mnt(2))](3), supported by crystallography, ESCA chemical shifts of Ni 2p(3/2) and EPR. The susceptibility data in combination with ESCA chemical shifts of S 2p(3/2) and Ni 2p(3/2) on all the compounds reveal the importance of charge transfer between the two counter ions. (C) 2011 Elsevier B.V. All rights reserved.

}, keywords = {Iron complexes, Magnetism, Reverse-spin crossover, X-ray crystal structures}, issn = {0020-1693}, doi = {10.1016/j.ica.2011.02.081}, author = {Manoharan, Periakaruppan T. and Sambandam, Balaji and Amsarani, Ramamoorthy and Varghese, Babu and Gopinath, Chinnakonda S. and Nomura, Kiyoshi} } @article { ISI:000295843900024, title = {MgCl2 center dot 6PhCH(2)OH - a new molecular adduct as support material for ziegler-natta catalyst: synthesis, characterization and catalytic activity}, journal = {Dalton Transactions}, volume = {40}, number = {41}, year = {2011}, month = {SEP}, pages = {10936-10944}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Benzyl alcohol has been used to prepare a single phase MgCl2 center dot 6BzOH molecular adduct as a support for an ethylene polymerization catalyst (Ziegler catalyst). The structural, spectroscopic and morphological aspects of the MgCl2 center dot 6BzOH molecular adduct and the Ziegler catalyst have been thoroughly studied by various physicochemical characterization techniques. The presence of MgO6 octahedrons due to the interaction of Mg2+ with six -OH groups of the benzyl alcohol is confirmed from a Raman feature at 703 cm(-1), and structural studies. The supported catalyst activity has been evaluated for the ethylene polymerization reaction. The lower polymerization activity of the titanated Ziegler-Natta catalyst compared with a standard catalyst is attributed to the strong interaction of titanium chloride with the support and associated electronic factors.

}, issn = {1477-9226}, doi = {10.1039/c1dt10786k}, author = {Gnanakumar, Edwin S. and Thushara, K. S. and Bhange, Deu S. and Mathew, Renny and Ajithkumar, Thalasseril G. and Rajamohanan, P. R. and Bhaduri, Sumit and Gopinath, Chinnakonda S.} } @article { ISI:000287092000035, title = {Porosity driven photocatalytic activity of wormhole mesoporous TiO2-xNx in direct sunlight}, journal = {Journal of Materials Chemistry}, volume = {21}, number = {8}, year = {2011}, month = {JAN}, pages = {2639-2647}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Results obtained by combining four important factors simultaneously, namely, wormhole mesoporosity with low diffusion length for charge carriers, high surface area, nanoparticles with high crystallinity, and visible light absorption due to N-doping, in titania (meso-TiO2-xNx) are reported. Meso-TiO2-xNx materials have been prepared by a combustion method within 10 min and by varying urea : Ti(NO3)(4) between 1 (UT1) and 10 (UT10). All of the prepared materials have been thoroughly characterised. Nanocrystalline anatase phase with high surface area (234 m(2) g(-1)), and type-IV H-3-mesoporosity is observed with UT10. Photocatalytic rhodamine-B degradation was employed to screen for the activity of the materials, and p-anisyl alcohol oxidation to p-anisaldehyde was carried out successfully in aqueous solution under direct sunlight. High photocatalytic activity of UT10 in direct sunlight, in spite of high band gap (3.24 eV), is attributed to the better utilization of holes due to the low charge diffusion barrier associated with wormhole mesoporosity along with highly crystalline, however, nanoparticulate TiO2-xNx.

}, issn = {0959-9428}, doi = {10.1039/c0jm03825c}, author = {Sivaranjani, Kumarsrinivasan and Gopinath, Chinnakonda S.} } @article { ISI:000296172800062, title = {Possible deNO(x) management under net oxidizing conditions: a molecular beam study of (NO)-N-15+CO+O-2 reaction on Pd(111) surfaces}, journal = {Journal of Physical Chemistry C}, volume = {115}, number = {43}, year = {2011}, month = {NOV}, pages = {21299-21310}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Isothermal kinetic measurements of (NO)-N-15 reduction with CO on Pd(111) surfaces were carried out under net-oxidizing conditions with (NO)-N-15 + CO + O-2, using a molecular beam instrument (MBI). Transient state (TS) and steady state (SS) kinetic details of the above reaction were obtained for a wide range of temperature and beam compositions, especially with O-2-rich compositions. Increasing O-2 content, generally, suppresses (NO)-N-15 reduction in the SS; nonetheless, irrespective of O-2 content, N-15(2) was produced in TS, and to a significant extent under SS conditions too. Sustainable N-2 production between 450 and 600 K and with low to moderate amount of oxygen was observed, and the extent of NO decomposition was also quantified. The ratio of N-15(2): (N2O)-N-15 was generally found to be around 8:1 under most of the reaction conditions. Maxima in the SS reaction rates of all products were observed between 500 and 600 K. Compared to other elementary reaction steps, a slow decay observed with N + N -\> N-2 step under SS beam oscillation conditions demonstrates its contribution to the rate limiting nature of the overall reaction. Fast beam switching experiments have been performed alternately between O-2-lean and -rich conditions, thus highlighting the effectiveness of (NO)-N-15 reduction in TS, irrespective of the beam composition. Possibly in a future technology initiative, this aspect could be exploited to manage more (NO)-N-15 reduction on Pd-based catalysts.

}, issn = {1932-7447}, doi = {10.1021/jp207092s}, author = {Nagarajan, Sankaranarayanan and Thirunavukkarasu, Kandasamy and Gopinath, Chinnakonda S.} } @article { ISI:000291421400015, title = {Selective hydrogenation of chloronitrobenzenes with an MCM-41 supported platinum allyl complex derived catalyst}, journal = {Applied Catalysis A-General}, volume = {399}, number = {1-2}, year = {2011}, month = {MAY}, pages = {117-125}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

A platinuin precatalyst (1) has been prepared by reacting [(eta(3)-C3H5)(4)Pt4Cl4] with surface functionalized MCM-41 with pendant -(CH2)(3)NH(CH2)(2)NH2 groups. For the hydrogenation of o-, m- and p-chloronitrobenzenes to the corresponding chloroanilines, 1 is found to be a highly active catalyst with good selectivities for them-and p-isomers. Its performance is superior to that of its palladium analogue and far superior to that of commercial (5\%) Pt/C or (5\%) Pt/Al2O3. Comparison of solid state and solution NMR data and other evidences indicate that on treatment with the functionalized MCM-41 support; [(eta(3)-C3H5)(4)Pt4Cl4] loses the ally! ligand. XPS data show that in the fresh catalyst Pt is present in the 2+ oxidation state. Based on these and analytical data, co-ordination by surface diamine and hydroxo groups to Pt2+ in 1 is suggested. In the used catalyst both Pt2+ and Pt are present but the amount of metallic platinum is similar to 16\% of the total. (C) 2011 Elsevier B.V. All rights reserved.

}, keywords = {Chloronitrobenzenes, Dehydrohalogenation, heterogeneous catalyst, MCM-41, Selective hydrogenation}, issn = {0926-860X}, doi = {10.1016/j.apcata.2011.03.044}, author = {Indra, Arindam and Rajamohanan, Pattuparambil R. and Gopinath, Chinnakonda S. and Bhaduri, Sumit and Lahiri, Goutam Kumar} } @article { ISI:000286868600075, title = {Toward an understanding of the molecular level properties of ziegler-natta catalyst support with and without the internal electron donor}, journal = {Journal of Physical Chemistry C}, volume = {115}, number = {5}, year = {2011}, month = {FEB}, pages = {1952-1960}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Two Ziegler-Natta catalysts supported on molecular adducts, namely, MgCl2 center dot 6EtOH (ME) and MgCl2 center dot 5EtOH center dot EtOOCPh (Est-ME), have been prepared. A systematic effort has been made to unravel the molecular level structure property relationships of the catalysts and adducts. Ethylbenzoate is an internal electron donor, and its in situ formation through EtOH+PhCOCl coupling is successfully achieved. The above adduct has been treated with TiCl4, and the resultant catalyst (Ti/Est-ME) is evaluated for ethylene polymerization activity. Rand C-13 CP/MAS NMR of Est-ME (Ti/Est-ME) show carbonyl features at 1730 (1680) cm(-1) and 169 (170) delta, respectively, providing direct support for the presence of ester as an integral part. In spite of low surface area, Ti/Est-ME gives higher yield for ethylene polymerization than the one derived from ME. The results indicate that electronic environment is more important than surface area or any other single factor in determining the polymerization activity.

}, issn = {1932-7447}, doi = {10.1021/jp1078289}, author = {Thushara, K. S. and Gnanakumar, Edwin S. and Mathew, Renny and Jha, Ratnesh Kumar and Ajithkumar, Thalasseril G. and Rajamohanan, P. R. and Sarma, Krishna and Padmanabhan, Sudhakar and Bhaduri, Sumit and Gopinath, Chinnakonda S.} } @article { ISI:000303426500018, title = {Evidence of cationic Pt active for water-gas shift reaction: Pt-doped BaCeO3 perovskite}, journal = {Journal of Physical Chemistry C}, volume = {116}, number = {17}, year = {2012}, month = {MAY}, pages = {9526-9532}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Precious metal incorporated into stable lattices like perovskites can be envisaged as an alternative catalysts to address deactivation problems. Here we report the barium cerate perovskite doped with varying amounts of Pt as catalysts for the water-gas shift reaction whereby ionic Pt is evidenced to be active. It is found that maximum CO conversion occurs above 325 degrees C and increases more than 2-fold after the first cycle. XPS analysis shows that after the first cycle, more ionic Pt species are present on the surface of the catalyst. X-ray and neutron diffraction studies also indicate the presence of oxygen vacancies that increases with increasing Pt substitution.

}, issn = {1932-7447}, doi = {10.1021/jp212211d}, author = {Rajesh, Thattarathody and Rajarajan, Anakot K. and Gopinath, Chinnakonda S. and Devi, R. Nandini} } @article { ISI:000305419900012, title = {Gamma-Al2-xMxO3 +/- y (M = Ti4+ through Ga3+): potential pseudo-3D mesoporous materials with tunable acidity and electronic structure}, journal = {Journal of Materials Chemistry}, volume = {22}, number = {27}, year = {2012}, month = {APR}, pages = {13484-13493}, publisher = {ROYAL SOC CHEMISTRY}, type = {Article}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A simple and highly efficient surfactant-free sol-gel process has been developed to obtain nanocrystalline mesoporous gamma-Al2O3 and metal ion incorporated mesoporous gamma-Al2O3 with general formula gamma-Al2-xMxO3 +/- y (where M = Ti4+ through Ga3+). Any one of the first row transition metal (TM) ions along with Ga3+ could be introduced into the gamma-Al2O3 framework in a direct one-pot synthesis process. The generality of the present synthesis recipe for metal ion incorporation in gamma-Al2O3 was demonstrated by preparation of an Al-Ga-M ternary oxide system with the metal ion composition of general formula Al9GaTM (TM = Ti4+ to Zn2+) and their characterization through various physicochemical and spectroscopic techniques. The mesoporous gamma-Al2-xMxO3 +/- y materials showed a BET surface area in the range of 200-400 m(2) g(-1) with a narrow pore size distribution. Wormhole mesoporosity makes the material pseudo-3D (p3D) with a small pore depth of few nm (\<10 nm). Metal ions in gamma-Al2O3 lead to changes in the acidity and electronic environment. XRD, TEM, and Al-27 MAS NMR studies demonstrate that the sol-gel process and the disordered mesoporous structure allow Ga and TM ions to be highly distributed and integrated in the gamma-Al2O3 framework. The efficacy of these materials in catalysis has been successfully evaluated for steam reforming of dimethylether: Ni, Cu and Zn containing Al9GaTM oxides showed high activity and stability. The smaller mesochannel depth (\<10 nm) and pseudo-3D characteristics that arise due to the wormhole-type disordered mesoporous framework of these alumina materials facilitate mass transport through them without any leaching of metal ions out of the lattice and pore blocking during the reaction, which makes them attractive in catalysis. This preparation method is versatile enough to be used for a reproducible synthesis of metal ion incorporated mesoporous gamma-Al2O3 by varying the metal content and their combinations, and it is expected that many other metal ions could be introduced into the lattice framework for a variety of applications by tuning acidity and electronic structure.

}, issn = {0959-9428}, doi = {10.1039/c2jm31184d}, author = {Mathew, Thomas and Sivaranjani, Kumarsrinivasan and Gnanakumar, Edwin S. and Yamada, Yusuke and Kobayashi, Tetsuhiko and Gopinath, Chinnakonda S.} } @article { ISI:000308361400011, title = {MgCl2 center dot 4((CH3)(2)CHCH2OH): a new molecular adduct for the preparation of TiClx/MgCl2 catalyst for olefin polymerization}, journal = {Dalton Transactions}, volume = {41}, number = {37}, year = {2012}, month = {JUL}, pages = {11311-11318}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A new molecular adduct of MgCl2 with isobutanol, namely MgCl2 center dot 4((CH3)(2)CHCH2OH) (MgiBOH), has been prepared as a precursor to the supporting material for an olefin polymerization catalyst. The MgiBOH adduct and final titanated Ziegler-Natta catalysts have been thoroughly characterized by powder XRD, thermal analysis, Raman spectroscopy and solid-state NMR for structural and spectroscopy aspects. A peak observed at 712 cm(-1) in the Raman spectra of MgiBOH indicates the characteristic Mg-O-6 breathing mode and the formation of the adduct. The diffraction feature at 2 theta = 7.8 degrees (d = 11.223 angstrom) in the XRD confirms the adduct formation and the layered structure. The aim of the present article is to study how the insertion of a bulky isobutanol moiety affects the structural and electronic properties of the MgCl2 isobutanol molecular adduct. Indeed, the focus of the present study is to explore how the presence of isobutanol, in the initial molecular adduct, influences the final Z-N catalyst properties and its activity.

}, issn = {1477-9226}, doi = {10.1039/c2dt31211e}, author = {Thushara, K. S. and Gnanakumar, Edwin S. and Mathew, Renny and Ajithkumar, Thalasseril G. and Rajamohanan, P. R. and Bhaduri, Sumit and Gopinath, Chinnakonda S.} } @article { ISI:000311190800033, title = {MgCl2 center dot 6C(6)H(11)OH: a high mileage porous support for ziegler-natta catalyst}, journal = {Journal of Physical Chemistry C}, volume = {116}, number = {45}, year = {2012}, month = {NOV}, pages = {24115-24122}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

A new and single phase molecular adduct of MgCl2 with six cyclohexanol molecules MgCl2 center dot 6C(6)H(11)OH (MgCyOH) has been synthesized. Structural insight to this adduct was obtained by a variety of physicochemical methods. C-13 CPMAS spectrum and single pulse MAS spectra with high power proton decoupling recorded at different relaxation time showed the presence of two different sets of magnetically unequal cylcohexanol molecules present around Mg2+. A Raman feature of MgCyOH at 712 cm(-1) confirms that cylcohexanol molecules are present around Mg2+ in an octahedral environment. MgCyOH has been used as support material to prepare Ziegler-Natta (Z-N) active catalyst. Textural property of above Z-N catalyst exhibits high surface area (236 m(2)/g) with high porosity. Above active catalyst has been screened for ethylene polymerization. Depending on the cocatalyst employed (Me3Al, Et3Al, and iso-Bu3Al) and ethylene pressure, polyethylene yield varies an order of magnitude, from 378 to 3570 g/g catalyst, indicating a possible creation of different active sites and different interaction between cocatalyst and catalyst.

}, issn = {1932-7447}, doi = {10.1021/jp3074078}, author = {Gnanakumar, Edwin S. and Thushara, K. S. and Gowda, Ravikumar R. and Raman, Sumesh K. and Ajithkumar, Thalasseril G. and Rajamohanan, P. R. and Chakraborty, Debashis and Gopinath, Chinnakonda S.} } @article { ISI:000300041700030, title = {Molecular oxygen-assisted oxidative dehydrogenation of ethylbenzene to styrene with nanocrystalline Ti1-xVxO2}, journal = {Green Chemistry}, volume = {14}, number = {2}, year = {2012}, month = {DEC}, pages = {461-471}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Oxidative dehydrogenation of ethylbenzene to styrene has been studied with vanadium-incorporated mesoporous nanocrystalline titania (Ti1-xVxO2) and molecular oxygen between 440 and 530 degrees C. Incorporation of V in TiO2 lattice framework has been achieved by simple solution combustion method. Incorporation of V in TiO2 lattice has been confirmed by X-ray diffraction, XPS and Raman spectra and other physicochemical analysis. High ethyl benzene conversion and stable styrene yield has been observed with 10\% V-containing rutile phase titania at 500 degrees C. However, stable but relatively lower styrene yield has been observed with 2 and 5\% V-containing catalysts between 440 and 500 degrees C. Highest selectivity is observed with lower vanadium content. Comparable activity has been observed under similar experimental conditions with four times higher air-flow than that of O-2. In order to understand the structure activity relationship, spent catalysts were analyzed by all physico-chemical methods. Although there is a phase change from anatase to rutile Ti1-xVxO2 within 1 h of reaction, higher activity is primarily attributed to the ionic V5+ in Ti1-xVxO2 lattice, which prevents agglomeration to V2O5. It is to be underscored the reactivity is retained at the cost of textural properties and phase change from anatase to rutile, which is essential for the reaction.

}, issn = {1463-9262}, doi = {10.1039/c1gc15907k}, author = {Sivaranjani, Kumarsrinivasan and Verma, Akrati and Gopinath, Chinnakonda S.} } @article { ISI:000311350000013, title = {Simple one pot synthesis of nano gold-mesoporous silica and its oxidation catalysis}, journal = {Catalysis Today}, volume = {198}, number = {1, SI}, year = {2012}, month = {DEC}, pages = {92-97}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

A simple one pot synthesis strategy using a non ionic triblock copolymer P123 as reducing as well as templating agent has been employed to prepare nano gold particles incorporated in the pores of mesoporous silica catalyst. The catalyst is characterized by XRD, nitrogen adsorption desorption isotherms at 77 K and TEM. The presence of small gold nanopartilces (similar to 2-4 nm) clearly demonstrated that this strategy can be effective in incorporating Au inside mesochannels. The catalyst reduced at 300 degrees C in H-2 was found to be active for oxidation reactions, such as CO oxidation, and benzyl alcohol. (C) 2012 Elsevier B. V. All rights reserved.

}, keywords = {Alcohol oxidation, CO oxidation, Gold catalysis, Mesoporous silica}, issn = {0920-5861}, doi = {10.1016/j.cattod.2012.05.053}, author = {Sekhar, A. C. Sunil and Sivaranjani, Kumarsrinivasan and Gopinath, Chinnakonda S. and Vinod, C. P.} } @article { ISI:000299584400070, title = {Toward a quantitative correlation between microstructure and DSSC efficiency: a case study of TiO2-xNx nanoparticles in a disordered mesoporous framework}, journal = {Journal of Physical Chemistry C}, volume = {116}, number = {3, SI}, year = {2012}, month = {JAN}, pages = {2581-2587}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

The efficiency (eta) of a dye-sensitized solar cell (DSSC) depends on various parameters, the critical factors being a fast charge carrier transport and a slow rate of electron-hole recombination. The present article describes a simple combustion synthesis method to prepare TiO2-xNx with following four important features that directly influences eta: (1) a disordered mesoporous structural framework with high surface area to give high dye-loading and a small diffusion length for charge carriers allowing rapid movement to the surface; (2) electrically interconnected nanocrystalline TiO2-xNx particles with good necking and predominant (101) anatase facets to minimize electron-hole recombination; (3) low charge storage capacity in the titania framework; and (4) surface unsaturation assisting all the above factors. The pseudo-three-dimensional nature of mesoporous TiO2-xNx with the above features demonstrates the importance of textural features, and porosity allows faster diffusion of charge carriers to surface and their utilization to generate power. A quantitative correlation between interconnected nanoparticles over larger distances in a mesoporous framework and eta is demonstrated. This study also demonstrates an inexpensive and rapid method of producing the photoanode material with high eta in about 10 min.

}, issn = {1932-7447}, doi = {10.1021/jp210677d}, author = {Sivaranjani, Kumarsrinivasan and Agarkar, Shruti A. and Ogale, Satishchandra B. and Gopinath, Chinnakonda S.} } @article { ISI:000322068400048, title = {Aminosilicate sol-gel stabilized N-doped TiO2-Au nanocomposite materials and their potential environmental remediation applications}, journal = {RSC Advances}, volume = {3}, number = {32}, year = {2013}, month = {MAY}, pages = {13390-13398}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A facile chemical reduction method to synthesize amine functionalized silicate sol-gel-supported gold-deposited nitrogen-doped Degussa-TiO2 nanocomposite materials (APS/(N-P25-Au)(NCM)) is reported and the materials are characterized by DRS, PL, XRD, TEM, Raman, XPS and BET surface area analysis. The application of the synthesized APS/(N-P25-Au)(N)CM towards environmental remediation processes are investigated by studying the catalytic oxidation of carbon monoxide (CO) and photocatalytic reduction of toxic mercuric (Hg(II)) ions. The catalytic and photocatalytic activity of the prepared catalysts are found to be in the order of APS/(N-P25-Au)(NCM) \>\> APS/(P25-Au)(NCM) \> N-P25 \> P25. The enhanced catalytic and photocatalytic activities of the APS/(N-P25-Au)(NCM) can be attributed to the synergistic effect of Au-nps and N-doped P25. The catalytic activities of the APS/(N-P25-Au)(NCM) are very promising in the field of green technology for the environmental cleaning applications.

}, issn = {2046-2069}, doi = {10.1039/c3ra40573g}, author = {Pandikumar, Alagarsamy and Sivaranjani, Kumarsrinivasan and Gopinath, Chinnakonda S. and Ramaraj, Ramasamy} } @article { ISI:000315707600041, title = {Design and performance aspects of a custom-built ambient pressure photoelectron spectrometer toward bridging the pressure gap: oxidation of Cu, Ag, and Au surfaces at 1 mbar O-2 pressure}, journal = {Journal of Physical Chemistry C}, volume = {117}, number = {9}, year = {2013}, month = {MAR}, pages = {4717-4726}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

The critical features of a custom-built laboratory version ambient pressure photoelectron spectrometer (Lab-APPES) are presented. A double front cone differential pumping arrangement and an aperture free design employed in the electrostatic lens regime improve the data collection and data quality. In contrast to the conventional X-ray photoelectron spectrometers (XPS) operating at ultrahigh vacuum (UHV), it is possible to explore the electronic structure of solid surfaces under working conditions or closer to working conditions with Lab-APPES. Especially surface-dependent phenomena can be explored up to 1 mbar pressure and up to 873 K by conventional heating methods and at least up to 1273 K by a laser heating method. Simultaneous XPS and reaction kinetic measurements on solid surfaces make the Lab-APPES an important tool to measure the dynamic electronic structure changes on material surfaces under reaction conditions. The interaction of O-2 with polycrystalline foils of Cu, Ag, and Au from UHV to 1 mbar and up to 773 K has been studied.

}, issn = {1932-7447}, doi = {10.1021/jp312706s}, author = {Roy, Kanak and Vinod, C. P. and Gopinath, Chinnakonda S.} } @article { ISI:000315013200017, title = {Disordered mesoporous V/TiO2 system for ambient oxidation of sulfides to sulfoxides}, journal = {Applied Catalysis A-General}, volume = {452}, year = {2013}, month = {FEB}, pages = {132-138}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

High sulfide conversion and predominant sulfoxide yield has been observed with 0.1\% vanadium doped disordered mesoporous Ti1-xVxO2 material at ambient and sub ambient temperatures using environmentally green H2O2 oxidant. Ti1-xVxO2 materials were prepared by one-pot solution combustion method in less than 15 min and thoroughly characterized by X-ray diffraction, HRTEM, Raman spectra and other physicochemical techniques. Different sulfides, such as, phenylsulfide, methyl-p-tolylsulfide, ethylsulfide, thioanisole, were converted into the corresponding sulfoxide. Isolated V5+ incorporated in the TiO2 lattice is likely to be the active species for the sulfide oxidation reaction. Catalyst recycling studies indicates the robustness of the catalyst. (c) 2012 Elsevier B.V. All rights reserved.

}, keywords = {Ambient oxidation, Combustion synthesis, heterogeneous catalysis, Hydrogen peroxide, Mesoporous TiO2, Sulfoxidation, Sulfoxide}, issn = {0926-860X}, doi = {10.1016/j.apcata.2012.11.035}, author = {Negi, Sanjay Singh and Sivaranjani, Kumarsrinivasan and Singh, Anand Pal and Gopinath, Chinnakonda S.} } @article { ISI:000319027400029, title = {Functional and disordered meso-macroporous gamma-Al2-xMxO3 +/- y (M = Cu and/or Ce)}, journal = {Journal of Nanoscience and Nanotechnology}, volume = {13}, number = {4, SI}, year = {2013}, month = {APR}, pages = {2682-2688}, publisher = {AMER SCIENTIFIC PUBLISHERS}, address = {26650 THE OLD RD, STE 208, VALENCIA, CA 91381-0751 USA}, abstract = {Disordered meso-macro porous Cu-Ce-Al2O3 nanocomposite (gamma-Al2-xMxO3 +/- y, M = Cu and or Ce) with different compositions has been synthesized. In situ templated sol-gel method has been adopted with simple EDTA ethylenediamine tetra aceticacid and ethylenediamine molecules to prepare gamma-Al2-xMxO3 +/- y, (M = Cu and or Ce). Above meso-macro porous materials were characterized by structural, spectroscopy, microscopy and textural techniques. Detailed characterization indicates that Cu2+ ions are introduced into the ceria and alumina lattice positions. Nano composite nature of the gamma-Al2-xMxO3 +/- y has been confirmed by detailed microscopy investigations. Catalytic activity of the above nanocomposite materials have been screened for environmentally important CO oxidation reaction. 30\% Ce-60\% Al and 10\% Cu containing material shows the best activity among other meso-nnacroporous material with (50\%) 100\% CO oxidation at (107 degrees C) 145 degrees C.}, keywords = {Alumina, CO oxidation, heterogeneous catalysis, Meso-Macroporous Material, Nanocomposite, Sol-gel synthesis}, issn = {1533-4880}, doi = {10.1166/jnn.2013.7384}, author = {Gnanakumar, Edwin S. and John, Jino C. and Raja, Thirumalaiswamy and Gopinath, Chinnakonda S.} } @article { ISI:000318939700024, title = {Hydroxyapatite supported palladium catalysts for suzuki-miyaura cross-coupling reaction in aqueous medium}, journal = {Catalysis Science \& Technology}, volume = {3}, number = {6}, year = {2013}, month = {MAR}, pages = {1625-1633}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Supported palladium catalyst 1 has been prepared by the immobilisation of [Pd(COD)Cl-2] (COD = 1,5-cyclooctadiene) on hydroxyapatite. Catalyst 2 has been prepared by subsequent reduction of catalyst 1 with sodium borohydride in ethanol. Under similar reaction conditions, catalyst 1 with Pd2+, is found to be almost five times more active than 2. Using 1 as the catalyst and water as the solvent, reaction conditions for Suzuki-Miyaura cross-coupling reactions have been optimised under aerobic conditions. The best catalytic activities are observed in the presence of potassium carbonate as the base and tetrabutylammonium bromide as a promoter. Catalyst 1 has been tested for catalytic cross-coupling reactions with sixteen different, electronically neutral, electron rich, electron poor and sterically hindered aryl boronic acids, and several different aryl halides including aryl chlorides. More than thousand turnovers and high selectivities to the hetero-coupled products have been observed in most cases. For many substrates the turnovers with 1 are notably more than what has been reported with other supported catalysts in water. The recyclability and scale-up potential of catalyst 1 have been tested and found to be satisfactory. A negligible drop in activity is observed over ten recycles with an accumulated turnover number of similar to 30000.

}, issn = {2044-4753}, doi = {10.1039/c3cy00160a}, author = {Indra, Arindam and Gopinath, Chinnakonda S. and Bhaduri, Sumit and Lahiri, Goutam Kumar} } @article { ISI:000315707700003, title = {MgCl2 center dot 6CH(3)OH: a simple molecular adduct and its influence as a porous support for olefin polymerization}, journal = {ACS Catalysis}, volume = {3}, number = {3}, year = {2013}, month = {MAR}, pages = {303-311}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

A single phase molecular adduct, MgCl2 center dot 6CH(3)OH has been synthesized using MgCl2 and the simplest alcohol, methanol. Structural, spectroscopic, and morphological studies have been carried out for a better understanding of the single phase MgCl2 center dot 6CH(3)OH adduct. C-13 CPMAS solid state NMR studies show all six methanol molecules are magnetically equivalent and present in a single environment around the Mg2+ center. Raman spectral analysis of the characteristic peak at 708 cm(-1) substantiates octahedral coordination of six CH3OH molecules around Mg2+. Solid state C-13 NMR measurements, made after heat treatment at different temperatures, have been utilized to understand the variations in CH3OH stoichiometry and coordination around Mg2+ with temperature. A titanated active catalyst, TiCl4 on MgCl2 center dot 6CH(3)OH, has also been synthesized and subjected to detailed characterizations. The active catalyst shows high surface area (102 m(2)/g) and mesoporosity. The titanated catalyst has been screened for ethylene polymerization reactions using different cocatalysts (R3Al; R= -CH3, -CH2CH3, and -CH2CH(CH3)(2)). A total of 7.25 kg of polyethylene per gram of catalyst has been obtained with Me3Al cocatalyst, which is six times higher in activity compared with commercial Me3Al/TiCl4/MgCl2 center dot 6EtOH-supported orted catalystAlthough porosity influences the catalytic activity, other factors also seem to contribute to the total catalytic activity.

}, keywords = {heterogeneous catalysis, MgCl2, Molecular adduct, olefin polymerization, Ziegler-Natta catalyst}, issn = {2155-5435}, doi = {10.1021/cs300730j}, author = {Gnanakumar, Edwin S. and Gowda, Ravikumar R. and Kunjir, Shrikant and Ajithkumar, Thalasseril G. and Rajamohanan, P. R. and Chakraborty, Debashis and Gopinath, Chinnakonda S.} } @article { ISI:000321434500006, title = {Palladium chloride catalyzed photochemical heck reaction}, journal = {Canadian Journal of Chemistry-Revue Canadienne De Chimie}, volume = {91}, number = {5}, year = {2013}, month = {MAY}, pages = {348-351}, publisher = {CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS}, address = {65 AURIGA DR, SUITE 203, OTTAWA, ON K2E 7W6, CANADA}, abstract = {

PdCl2 catalyzed carbon-carbon bond formation (Heck reaction) between substituted aryl halides and olefins was carried out without a ligand, under irradiation with UV-visible light. The results demonstrated that UV-visible light accelerated the rate of the reaction, leading to an excellent yield of corresponding products. The recovered palladium nanoparticles could be thermally recycled several times. PdCl2 gave excellent conversion up to the fifth addition of substrate.

}, keywords = {C-C coupling, Heck reaction, iodobenzene, photochemical reaction}, issn = {0008-4042}, doi = {10.1139/cjc-2012-0377}, author = {Waghmode, Suresh B. and Arbuj, Sudhir S. and Wani, Bina N. and Gopinath, Chinnakonda S.} } @article { ISI:000326946900004, title = {Rationally designed CuFe2O4-mesoporous Al2O3 composite towards stable performance of high temperature water-gas shift reaction}, journal = {Chemical Communications}, volume = {49}, number = {96}, year = {2013}, month = {JUL}, pages = {11257-11259}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

High temperature water-gas shift reaction was demonstrated for the first time on a CuFe2O4-mesoporous alumina nanocomposite between 350 and 550 degrees C with 70-80\% CO-conversion using simulated waste derived syngas under realistic conditions. Despite high Al-content, the catalyst exhibited stable activity, which was attributed to the nano-architectured robust porous nature of alumina integrated with surrounding CuFe2O4.

}, issn = {1359-7345}, doi = {10.1039/c3cc43699c}, author = {Subramanian, Vijayanand and Gnanakumar, Edwin S. and Jeong, Dae-Woon and Han, Won-Bi and Gopinath, Chinnakonda S. and Roh, Hyun-Seog} } @article { ISI:000317596800004, title = {Synthesis and catalytic activity of monodisperse gold-mesoporous silica core-shell nanocatalysts}, journal = {Catalysis Science \& Technology}, volume = {3}, number = {5}, year = {2013}, month = {FEB}, pages = {1190-1193}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Core-shell nanostructures, where gold nanoparticles of sub 10 nm size are successfully encapsulated inside porous silica spheres, have been prepared. The detailed characterization of the catalyst shows a high surface area and good mesoporosity. The sinter resistance of the catalyst under repeated cycles of the CO oxidation reaction is observed.

}, issn = {2044-4753}, doi = {10.1039/c3cy20772b}, author = {Sekhar, A. C. Sunil and Meera, C. J. and Kottavarithottil Ziyad and Gopinath, Chinnakonda S. and Vinod, C. P.} } @article { ISI:000336840900022, title = {9-Fluorenemethanol: an internal electron donor to fine tune olefin polymerization activity}, journal = {Dalton Transactions}, volume = {43}, number = {24}, year = {2014}, month = {MAR}, pages = {9143-9151}, publisher = {ROYAL SOC CHEMISTRY}, type = {Article}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A new MgCl2 based molecular adduct has been synthesized with 9-fluorenemethanol (9FM) as a novel internal electron donor (IED), along with ethanol (EtOH) (MgCl2 center dot n9FM center dot xEtOH). The above molecular adduct has been subjected to a variety of structural, spectroscopic and morphological characterization techniques. The results of the solid state C-13 CPMAS NMR technique suggests the coordination of 9FM to MgCl2. Observation of a low angle diffraction peak at 2 theta = 5.7 degrees (d = 15.5 angstrom) underscores the coordination of 9FM along the z-axis, and ethanol in the molecular adduct. Active Ziegler-Natta catalysts were prepared by two different synthesis methods; the conventional method to obtain a high surface area active catalyst, and other one with 9FM as an integral part of the active catalyst in order to study the influence of 9FM as an IED over the active sites. The active catalysts were also characterized thoroughly with different analytical tools. The XRD results show (003) facets of delta-MgCl2 (alpha-MgCl2) for the conventional (non-conventional) titanated catalyst. Results of the ethylene polymerization activity study reveals that the conventionally prepared highly porous active catalyst shows 1.7-2.5 times higher activity than the non-conventional prepared catalyst; however, the latter shows a low molecular weight distribution and confirms the role of the Lewis base as an IED.

}, issn = {1477-9226}, doi = {10.1039/c4dt00793j}, author = {Gnanakumar, Edwin S. and Chokkapu, Eswara Rao and Kunjir, Shrikant and Ajithkumar, Thalasseril G. and Rajamohanan, P. R. and Chakraborty, Debashis and Gopinath, Chinnakonda S.} } @article { ISI:000341405600003, title = {Ambient oxidation of benzene to phenol by photocatalysis on Au/Ti0.98V0.02O2: role of holes}, journal = {ACS Catalysis}, volume = {4}, number = {9}, year = {2014}, month = {SEP}, pages = {2844-2853}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

A potential photocatalyst with 2 atom \% vanadium incorporated into the 1 lattice of disordered mesoporous titania, Ti0.98V0.02O2, (TV2) was synthesized. Au was deposited on TV2 (Au/TV2) through a photodeposition method. Structural, microscopy, and spectroscopy techniques support the incorporation of vanadium into the TiO2 lattice, and Au was deposited on the surfaces of TV2. Photocatalytic oxidation of benzene was conducted at ambient temperature under UV and/or visible light to demonstrate the catalytic activity of the Au/TV2 catalyst. The TV2 lattice exhibits a quantum jump in benzene to phenol oxidation compared to that of TiO2, highlighting the importance of V for oxidation. Introduction of Au onto TV2 further increases the benzene to phenol oxidation and phenol yield by a factor of 2 under UV light compared to those of bare TV2. No significant phenol production was observed in visible light with or without gold, indicating the role of gold is indirect toward charge separation and electron storage. Nano gold clusters on TV2 selectively store photoexcited electrons and in turn maximize holes utilization on TiO2. The high photocatalytic activity of Au/TV2 is mainly attributed to the presence of Schottky junctions, disordered mesoporosity, and short diffusion lengths for charge carriers.

}, keywords = {nano gold, phenol, Photocatalysis, Schottky junction, titania, Vanadium}, issn = {2155-5435}, doi = {10.1021/cs500724z}, author = {Devaraji, Perumal and Sathu, Naveen K. and Gopinath, Chinnakonda S.} } @article { ISI:000337637100017, title = {Disordered mesoporous TiO2-xNx+Nano-Au: an electronically integrated nanocomposite for solar H-2 generation}, journal = {ChemCatChem}, volume = {6}, number = {2}, year = {2014}, month = {FEB}, pages = {522-530}, publisher = {WILEY-V C H VERLAG GMBH}, type = {Article}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

We report on H-2 generation by photocatalysis driven by simulated white light by electronically integrated Au nanoparticles with multifunctional, disordered mesoporous TiO2-xNx (Au-NT) nanocomposites. Solar H-2 generation (1.5 mmolh(-1)g(-1)) from aqueous methanol has been demonstrated with Au-NT nanocomposites. The water splitting activity of Au-NT is attributed to the 21.1 ps lifetime of charge carriers observed from fluorescence lifetime measurements, which indicates a high electron-injection efficiency from nano-Au to the conduction band of TiO2, and hence charge separation as well as utilization. This is directly supported by the observation of a high photoluminescence emission intensity with Au-NT that highlights the energy transfer from nano-Au to TiO2. The p-n heterojunction observed between the Au (001) and TiO2 (101) facets helps to-wards the higher charge separation and their utilization. A low mesochannel depth (\< 10 nm) associated with disordered mesoporous TiO2-xNx helps the charge carriers to move towards the surface for redox reactions and hence charge utilization. Visible-light absorption, as a result of the surface plasmon resonance of nano-Au, is observed in a broad range between 500 and 750 nm, which helps in harvesting visible-light photons. Finally, electronically integrated nano-Au with TiO2-xNx in Au-NT is evident from Raman and X-ray photoelectron spectroscopy measurements. All of these factors help to achieve a high rate of H-2 production. It is likely that a higher rate of H-2 production than that reported here is feasible by strategically locating Au clusters in porous TiO2 to generate hot spots through electronic integration.

}, keywords = {heterogeneous catalysis, Hydrogen, mesoporous materials, photochemistry, water splitting}, issn = {1867-3880}, doi = {10.1002/cctc.201300715}, author = {Sivaranjani, Kumarsrinivasan and Rajaambal, Sivaraman and Das, Tanmay and Roy, Kanak and Bhattacharyya, Somnath and Gopinath, Chinnakonda S.} } @article { ISI:000334895800014, title = {Effect of method of preparation on hydrodesulphurization activity of Co- or Ni-promoted MoS2/SBA-15 catalysts}, journal = {Journal of Chemical Sciences}, volume = {126}, number = {2, SI}, year = {2014}, note = {21st National Symposium on Catalysis (CATSYMP), CSIR Indian Inst Chem Technol, Hyderabad, INDIA, FEB 11-13, 2013}, month = {MAR}, pages = {437-444}, publisher = {Catalysis Soc India}, type = {Article}, address = {C V RAMAN AVENUE, SADASHIVANAGAR, P B \#8005, BANGALORE 560 080, INDIA}, abstract = {

Ordered mesoporous material SBA-15 was synthesized and used as a support for the preparation of molybdenum sulphide catalysts through precipitation from homogeneous solution (PFHS) technique with the Mo content varying from 2-12 wt\%. The prepared catalysts were evaluated for thiophene hydrodesulphurizadon catalytic activities at 400 degrees C. Catalysts prepared through PFHS method resulted in highly dispersed MoS2 catalysts, which were inferred from powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), low temperature oxygen chemisorptions (LTOC) and BET surface area analysis. The relationship between XPS intensity ratio, oxygen chemisorption and catalytic activities is discussed in terms of highly dispersed nano particles of MoS2 and its consequence in accommodating more promoted atoms at the edge sites.

}, keywords = {HDS, MoS2, PFHS method, promotional effects, SBA-15}, issn = {0974-3626}, author = {Garg, Shelu and Soni, Kapil and Prasad, V. V. D. N. and Kumar, Manoj and Bhaskar, Thallada and Gupta, J. K. and Dhar, G. Murali and Gopinath, Chinnakonda S.} } @article { ISI:000343974100018, title = {Electronic structure-sunlight driven water splitting activity correlation of (Zn1-yGay)(O1-zNz)}, journal = {Physical Chemistry Chemical Physics}, volume = {16}, number = {43}, year = {2014}, month = {SEP}, pages = {23654-23662}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

(Zn1-yGay)(O1-zNz) (y \<= 0.10; z \<= 0.15) solid solutions have been investigated for their electronic structure and visible light photocatalytic activity, and a correlation was found between them. (Zn1-yGay)(O1-zNz) with ZnO as the major component have been synthesized by a solution combustion method in 10 minutes using simple raw materials. The local structures of Zn K edge and Ga K edge, and changes in the chemical environment with the incorporation of Ga and N in ZnO were determined by EXAFS study. EXAFS and XRD results suggested the dissolution of GaN in the ZnO lattice. The homogeneity of the solid solution was demonstrated from HRTEM studies. Photoluminescence studies revealed the creation of a new band at the top of the ZnO valence band (VB), and thus the broadening of the VB of (Zn1-yGay)(O1-zNz) or a decrease in the band gap was attributed to the origin of visible light absorption. UV-Vis spectral studies showed light absorption up to 550 nm, which directly supports the VB broadening. Predominant oxygen vacancies and high photocorrosion observed for ZnO were fully suppressed for (Zn1-yGay)(O1-zNz) , indicating the minimization of defects, and thus more sustainability under irradiation conditions. The bare solid solution exhibited reasonable and promising activity for solar hydrogen evolution and photoelectrochemical current generation at 0 V. The present work explained factors such as the preparation method, single phase structure with the stabilization of integral parts, homogeneity in the structure, compensation of oxygen vacancies, and suppression of the density of recombination centres that play a pivotal role in realizing solar energy harvesting.

}, issn = {1463-9076}, doi = {10.1039/c4cp03640a}, author = {Rajaambal, Sivaraman and Yadav, A. K. and Jha, Shambhu Nath and Bhattacharyya, Dibyendu and Gopinath, Chinnakonda S.} } @article { ISI:000341065800011, title = {Facile method for the synthesis of Co-core Au-shell nanohybrid}, journal = {New Journal Of Chemistry}, volume = {38}, number = {9}, year = {2014}, month = {SEP}, pages = {4107-4114}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Heterostructured Co-Au core-shell nanoparticles have been synthesized by reducing AuCl4- ions on cobalt nanoparticles after a minor but effective modification of cobalt surface by an amine. The core shell morphology is emphatically confirmed by thorough investigation through UV-Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopic analysis (TEM). The chemical composition and topography were determined using STEM-HAADF analysis and EFTEM imaging. Fourier transform infrared (FTIR) spectroscopy confirms the surface modification of Co nanoparticles and the interactions involved between the ligands and the core and shell metals at various steps of the synthetic process. The magnetic properties confirm the material to be superparamagnetic in nature.

}, issn = {1144-0546}, doi = {10.1039/c4nj00733f}, author = {Sardar, Debasmita and Neogi, S. K. and Bandyopadhyay, Sanjoy and Satpati, Biswarup and Jain, Ruchi and Gopinath, Chinnakonda S. and Bala, Tanushree} } @article { ISI:000332144600065, title = {Facile single-step synthesis of nitrogen-doped reduced graphene oxide-Mn3O4 hybrid functional material for the electrocatalytic reduction of oxygen}, journal = {ACS Applied Materials \& Interfaces}, volume = {6}, number = {4}, year = {2014}, month = {FEB}, pages = {2692-2699}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Development of efficient electrocatalyst based on non-precious metal that favors the four-electron pathway for the reduction of oxygen in alkaline fuel cell is a challenging task. Herein, we demonstrate a new facile route for the synthesis of hybrid functional electrocatalyst based on nitrogen-doped reduced graphene oxide (N-rGO) and Mn3O4 with pronounced electrocatalytic activity towards oxygen reduction reaction (ORR) in alkaline solution. The synthesis involves one-step in situ reduction of both graphene oxide (GO) and Mn(VII), growth of Mn3O4 nanocrystals and nitrogen doping onto the carbon framework using a single reducing agent, hydrazine. The X-ray photoelectron (XPS), Raman and FTIR spectral, and X-ray diffraction measurements confirm the reduction of GO and growth of nanosized Mn3O4. The XPS profile reveals that N-rGO has pyridinic (40\%), pyrrolic (53\%), and pyridine N oxide (7\%) types of nitrogen. The Mn3O4 nanoparticles are single crystalline and randomly distributed over the wrinkled N-rGO sheets. The hybrid material has excellent ORR activity and it favors the 4-electron pathway for the reduction of oxygen. The electrocatalytic performance of the hybrid catalyst is superior to the N-rGO, free Mn3O4 and their physical mixture. The hybrid material shows an onset potential of -0.075 V, which is 60-225 mV less negative than that of the other catalyst tested. It has excellent methanol tolerance and high durability. The catalytic current density achieved with the hybrid material at 0.1 mg cm(-2) is almost equivalent to that of the commercial Pt/C (10\%). The synergistic effect of N-rGO and Mn3O4 enhances the overall performance of the hybrid catalyst. The nitrogen in N-rGO is considered to be at the interface to bridge the rGO framework and Mn3O4 nanoparticles and facilitates the electron transfer.

}, keywords = {electrocatalysis, hybrid material, Mn3O4, nitrogen-doped graphene, oxygen reduction, synergistic effect}, issn = {1944-8244}, doi = {10.1021/am405213z}, author = {Bag, Sourav and Roy, Kanak and Gopinath, Chinnakonda S. and Raj, C. Retna} } @article { ISI:000344998100063, title = {Green chemistry approach to styrene from ethylbenzene and air on MnxTi1-xO2 catalyst}, journal = {RSC Advances}, volume = {4}, number = {100}, year = {2014}, month = {OCT}, pages = {57087-57097}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Styrene (ST) is an industrially important commodity chemical, and design of a suitable catalyst, which provides high ethyl benzene (EB) conversion and styrene selectivity at Lower temperature with sustainable activity, is one of the major challenges in the field of heterogeneous catalysis. Manganese incorporated in titania (MnxT1-xO2) anatase Lattice, prepared via the solution combustion method, was evaluated for oxidative dehydrogenation (ODH) of EB with O-2 or air. MnxTi1-xO2 catalysts were characterized by different physiochemical methods. Up to 15\% Mn could be introduced into the TiO2 Lattice. TEM and XRD indicate disordered mesoporosity, further confirmed by adsorption isotherm analysis. MnxTi1-xO2 catalysts were evaluated for ST synthesis from EB using air or oxygen as oxidant between 440 and 570 degrees C. Reaction conditions have been varied systematically, such as catalyst composition, and EB/air/O-2 flow. MnxTi1-xO2 shows sustainable 55\% styrene yield for 45 h without deactivation under optimum conditions. A thorough analysis of spent catalysts demonstrates the conversion of initial anatase phase MnxTi1-xO2 to Mn3O4 supported on the rutile (R) phase of TiO2. The above change occurs in the first few hours of reaction and the Mn3O4 on R-TiO2 phase is the active phase of the catalyst and responsible for sustainable activity for Longer duration.

}, issn = {2046-2069}, doi = {10.1039/c4ra11814f}, author = {Negi, Sanjay Singh and Venugopalan, Aswathy Thareparambil and Raja, Thirumalaiswamy and Singh, Anand Pal and Gopinath, Chinnakonda S.} } @article { ISI:000340353100013, title = {In1-XGaXN@ZnO: a rationally designed and quantum dot integrated material for water splitting and solar harvesting applications}, journal = {Dalton Transactions}, volume = {43}, number = {33}, year = {2014}, month = {SEP}, pages = {12546-12554}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

The highly desirable combination of the visible light absorption properties of In1-xGaxN Quantum dots (QD) along with the multifunctionality of ZnO into a single integrated material was prepared for solar harvesting. This is the first report on InGaN QD integrated with ZnO (InGaN@ZnO), synthesized by a highly reproducible, simple combustion method in 15 min. Structural, microstructural and electronic integration of the nitride and oxide components of InGaN@ZnO was demonstrated by appropriate characterization methods. Self-assembly of InGaN QD is induced in growing nascent zinc oxo nanoclusters taking advantage of the common wurtzite structure and nitrogen incorporation at the expense of oxygen vacancies. Direct integration brings about a single phase structure exhibiting extensive visible tight absorption and high photostability. InGaN@ZnO suggests synergistic operation of tight harvesting and charge conducting components for solar H-2 generation without using any co-catalyst or sacrificial agent, and a promising photocurrent generation at 0 V under visible light illumination. The present study suggests a direct integration of QD with the host matrix and is a potential method to realize the advantages of QDs.

}, issn = {1477-9226}, doi = {10.1039/c4dt01268b}, author = {Rajaambal, Sivaraman and Mapa, Maitri and Gopinath, Chinnakonda S.} } @article { ISI:000339830200050, title = {Mapping of copper oxidation state using high pressure x-ray photoelectron spectroscopy}, journal = {Acta Physica Polonica A}, volume = {125}, number = {4}, year = {2014}, month = {APR}, pages = {1065-1066}, publisher = {POLISH ACAD SCIENCES INST PHYSICS}, address = {AL LOTNIKOW 32-46, PL-02-668 WARSAW, POLAND}, abstract = {

The interaction of O-2 with polycrystalline foil of Cu, from ultra high vacuum to 1 mbar and up to 773 K has been investigated. The study were performed by using the high pressure X-ray photoelectron spectroscopy (electron spectroscopy for chemical analysis) ultraviolet photoelectron spectroscopy system. In this work the results of mapping copper oxidation states as a function of temperature at 1 mbar O-2 have been presented.

}, issn = {0587-4246}, author = {Kowalska, J. and Gopinath, Chinnakonda S.} } @article { ISI:000332061300050, title = {Nanocomposite of silver and thermo-associating polymer by a green route: a potential soft-hard material for controlled drug release}, journal = {RSC Advances}, volume = {4}, number = {20}, year = {2014}, month = {JAN}, pages = {10261-10268}, publisher = {ROYAL SOC CHEMISTRY}, type = {Article}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Major research efforts are continuously being made to look for alternative, environment friendly green chemicals for the synthesis of nanoparticles in place of conventional and hazardous reducing agents such as sodium borohydride and hydrazine. We report here on the synthesis and characterization of AgNPs using a thermo-associating polymer namely, carboxymethyl guar grafted poly(ethylene oxide-co-propylene oxide) [CMG-g-PEPO]. The polymer acts as both reducing agent as well as stabilizing/capping agent. The formation of AgNPs with polymer was confirmed by UV/Vis spectroscopy and the TEM images indicated the size of nanoparticles to be in the range of 10-20 nm. We also demonstrated the use of these nanoparticles in the controlled release of doxorubicin hydrochloride (Dox), an anticancer drug. The binding of Dox onto the polymer and AgNPs was investigated by XPS and Raman spectroscopy which indicates that a charge-transfer mechanism is operative between the Dox and polymer holding both the entities together. The first synthesis of AgNPs using non-toxic thermo-associating polymer and subsequent release of Dox with body temperature (37 degrees C) as a trigger is the highlight of the present work.

}, issn = {2046-2069}, doi = {10.1039/c3ra45022h}, author = {Gupta, Nivika R. and Bhagavatula L. V. Prasad and Gopinath, Chinnakonda S. and Badiger, Manohar V.} } @article { ISI:000337637100018, title = {NOx reduction at near ambient temperatures and under lean-burn conditions on modified pd surfaces}, journal = {ChemCatChem}, volume = {6}, number = {2}, year = {2014}, month = {FEB}, pages = {531-537}, publisher = {WILEY-V C H VERLAG GMBH}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

Palladium surfaces that are modified with O atoms in the subsurface broaden the NO reduction temperature regime up to 325 K with O-2-rich NO+H-2+O-2 compositions. Compared to virgin Pd surfaces, up to 150\% higher deNO(x) catalytic activity was observed with modified Pd surfaces at the reaction maximum. Molecular beam instrument and ambient-pressure photoelectron spectroscopy were employed to follow the kinetic and surface changes. These results open up a possibility to realize the cold-start reduction of NOx (deNO(x)). DeNO(x) activity reported in the literature with supported Pd catalysts after a simple calcination in air compares well with our present observations. Surface modification is likely to demonstrate a high potential for other catalytic reactions at relatively low temperatures.

}, keywords = {heterogeneous catalysis, nitrogen, oxygen, Palladium, surface chemistry}, issn = {1867-3880}, doi = {10.1002/cctc.201301033}, author = {Roy, Kanak and Gopinath, Chinnakonda S.} } @article { ISI:000345826100018, title = {Preferential growth of Au on CdSe quantum dots using langmuir-blodgett technique}, journal = {RSC Advances}, volume = {4}, number = {110}, year = {2014}, month = {NOV}, pages = {64535-64541}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Oleyl amine capped CdSe quantum dots (QD) were synthesised by hot injection technique. These QDs formed a self-assembled monolayer on an aqueous subphase of a Langmuir-Blodgett (LB) trough. Here, in this report we introduced a simple but very efficient route to form a metal (Au)-QD hybrid nanostructure via the LB technique. In this method, the metal counterpart of the hybrid nanostructure could be deposited exclusively on one side of the QDs. The formation of stable monolayer of QDs was evidenced from a surface pressure-area (P-A) isotherm. The development of gold tip was confirmed and monitored by detailed TEM study on the monolayer deposited on TEM grids from the LB trough. Other characterizations like UV-Vis spectroscopy, FTIR, XPS and EDX also suggested the same. Oleyl amine was shown to act both as a reducing agent as well as a capping agent in this strategy.

}, issn = {2046-2069}, doi = {10.1039/c4ra11715h}, author = {Das, Subhasis and Satpati, Biswarup and Chauhan, Himani and Deka, Sasanka and Gopinath, Chinnakonda S. and Bala, Tanushree} } @article { ISI:000344330800015, title = {Role of nanointerfaces in Cu- and Cu plus Au-based near-ambient-temperature CO oxidation catalysts}, journal = {ChemCatChem}, volume = {6}, number = {11}, year = {2014}, month = {NOV}, pages = {3116-3124}, publisher = {WILEY-V C H VERLAG GMBH}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

Disordered mesoporous Cu-doped ceria-zirconia (Cu0.1Ce0.85Zr0.05O2), and gold deposited (Au/Cu0.1Ce0.85Zr0.05O2) catalysts were synthesized and evaluated for CO oxidation. Onset of CO oxidation activity, and 50\% (100\%) CO2 formation occurs at room temperature (RT), and 77 (120)degrees C, respectively, with Cu0.1Ce0.85Zr0.05O2. A small amount of gold on Cu0.1Ce0.85Zr0.05O2 induces the sustainable oxidation catalysis around RT. Onset of copper reduction temperature decreases from 110 degrees C on Cu0.1Ce0.85Zr0.05O2 to 48 degrees C with Au/Cu0.1Ce0.85Zr0.05O2, highlighting the direct interaction between Cu and Au through a Cu-Au interface. Au particles with a (00 1) facet deposit on an oxygen-deficient site of (111) facet of CeO2-ZrO2. Any decrease in surface Cu-content with increasing Au-content further supports the Au-Cu-Ce/Zr interface interactions. Nanointerfaces of Au clusters on Cu next to oxygen-deficient sites of CeO2-ZrO2 facilitate all the elementary steps of the CO + O-2 reaction to occur in close proximity at ambient conditions.

}, keywords = {carbon monoxide, Gold, heterogeneous catalysis, Oxidation, redox}, issn = {1867-3880}, doi = {10.1002/cctc.201402581}, author = {Gnanakumar, Edwin S. and Naik, Jarpla Madhusudhan and Manikandan, Marimuthu and Raja, Thirumalaiswamy and Gopinath, Chinnakonda S.} } @article { ISI:000331861300008, title = {Solid-state NMR investigations of a MgCl2 center dot 4(CH3)(2)CHCH2OH molecular adduct: a peculiar case of reversible equilibrium between two phases}, journal = {Journal of Physical Chemistry A}, volume = {118}, number = {7}, year = {2014}, month = {FEB}, pages = {1213-1219}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

MgCl2 center dot xROH molecular adducts are extensively employed as a support material for Ziegler-Natta polyolefin catalysis. However, their structural properties are not well understood. Recently, we reported on the preparation of an isobutanol adduct, MgCl2 center dot 4(CH3)(2)CHCH2OH (MgiBuOH) (Dalton Trans. 2012, 41, 11311), which is very sensitive to the preparation conditions, such as the temperature and refluxing time. For the present study, the structural properties of MgiBuOH adducts prepared under different conditions have been investigated thoroughly by solid-state NMR and nonambient XRD. Formation of two phases has been confirmed, and in situ variable temperature solid-state NMR measurements confirm the coexistence of two phases as well as the oscillation from one to another phase. It is expected that such molecular adducts could have a significant role in organic transformation reactions due to an oscillating structural component. An understanding of phase oscillation with the Mg2+ ion as the central metal ion might shed some light toward understanding various biological and structural functions.

}, issn = {1089-5639}, doi = {10.1021/jp412331s}, author = {Thushara, K. S. and Ajithkumar, Thalasseril G. and Rajamohanan, P. R. and Gopinath, Chinnakonda S.} } @article { ISI:000329266500032, title = {Structural investigations of porous MgCl2-2-butanol molecular adduct as support for olefin polymerization}, journal = {Applied Catalysis A-General}, volume = {469}, year = {2014}, month = {JAN}, pages = {267-274}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

A new heterogeneous Ziegler-Natta (Z-N) catalyst support material, MgCl2 center dot 4(CH3CH(OH)CH2CH3) (Mg2BuOH) has been synthesized. 2-Butanol, a linear, secondary alcohol was chosen for the generation of an active MgCl2 support which results in a Z-N catalyst with TiCl4. Significant feature of this work is the formation of rod shaped molecular adduct with highly porous character. Adduct material is characterized by XRD, TG-DTA, Raman spectroscopy, solid-state NMR and SEM. Activity of the Z-N catalyst supported on Mg2BuOH for ethylene polymerization is comparable with that of commercially available heterogeneous Z-N catalyst. However, there is scope to improve the activity by optimizing textural properties. (C) 2013 Elsevier B.V. All rights reserved.

}, keywords = {heterogeneous catalysis, MgCl2, Molecular adduct, NMR, Polyolefin, Ziegler-Natta catalyst}, issn = {0926-860X}, doi = {10.1016/j.apcata.2013.10.002}, author = {Thushara, K. S. and Ajithkumar, Thalasseril G. and Rajamohanan, P. R. and Gopinath, Chinnakonda S.} } @article { ISI:000337074700019, title = {Towards a sustainable and near ambient DeNO(x) under lean burn conditions: a revisit to no reduction on virgin and modified pd(111) surfaces}, journal = {ACS Catalysis}, volume = {4}, number = {6}, year = {2014}, month = {JUN}, pages = {1801-1811}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Catalytic conversion of NO in the presence of H-2 and O-2 has been studied on Pd(111) surfaces, by using a molecular beam instrument with mass spectrometry detection, as a function of temperature and reactants composition. N-2 and H2O are the major products observed, along with NH3 and N2O minor products under all conditions studied. Particular attention has been paid to the influence of O-2 addition toward NO dissociation. Although O-2-rich compositions were found to inhibit the deNO(x) activity of the Pd catalyst, some enhancement in NO reduction to N-2 was also observed up to a certain O-2 content. The reason for this behavior was determined to be the effective consumption of the H-2 in the mixture by the added O-2 and O atoms from NO dissociation. NO was proven to compete favorably against O-2 for the consumption of H-2, especially \<= 550 K, to produce N-2 and H2O. Compared with other elementary reaction steps, a slow decay observed with the 2H + 0 -\> H2O step under SS beam oscillation conditions demonstrates its contribution to the rate-limiting nature of the overall reaction. Pd(111) surfaces modified with O atoms in the subsurface (Md-Pd(111)) induces steady-state NO reduction at near-ambient temperatures (325 K) and opens up a possibility to achieve room temperature emission control. A 50\% increase in the reaction rates was observed at the reaction maximum on Md-Pd(111), as compared with virgin surfaces. Oxygen adsorption is severely limited below 400 K, and effective NO + H-2 reaction occurs on Md-Pd(111) surfaces. Valence band photoemission with a UV light source (He I) under different oxygen pressures with APPES clearly identified the characteristics of the Md-Pd(111) surfaces and PdO. The electron-deficient or cationic nature of Md-Pd(111) surfaces enhances the NO dissociation and inhibits oxygen chemisorption \<= 400 K under lean-burn conditions.

}, keywords = {deNO(x), heterogeneous catalysis, Hydrogen, lean burn, molecular beam, nitric oxide, Palladium, surface modification}, issn = {2155-5435}, doi = {10.1021/cs500342a}, author = {Roy, Kanak and Jain, Ruchi and Gopinath, Chinnakonda S.} } @article { ISI:000334658000001, title = {UV photoelectron spectroscopy at near ambient pressures: mapping valence band electronic structure changes from Cu to CuO}, journal = {Analytical Chemistry}, volume = {86}, number = {8}, year = {2014}, month = {APR}, pages = {3683-3687}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Valence band (VB) changes and hence electronic structure evolution was directly observed with low kinetic energy (KE) electrons at near ambient pressure (NAP) conditions with He I photon source in a custom built laboratory ambient pressure photoelectron spectrometer (Lab-APPES). Polycrystalline Cu surfaces were gradually oxidized in O-2 to Cu2O, to a mixture of Cu2O + CuO, and finally to CuO between 300 and 625 K and at NAP. Typical VB features for Cu, Cu2O, and CuO were observed, and the results corroborate well with core level and Auger spectral changes. High mean free path associated with low KE electrons, very low or no inelastic scattering, and effective pumping and the design of electrostatic lens regime help to minimize the electron attenuation at NAP conditions. The present results extend the capabilities of the APPES tool to explore the in situ evolution of electronic structure of materials at NAP and high temperatures.

}, issn = {0003-2700}, doi = {10.1021/ac4041026}, author = {Roy, Kanak and Gopinath, Chinnakonda S.} } @article { ISI:000349917900007, title = {Can we shift and/or broaden the catalysis regime towards ambient temperature?}, journal = {ChemCatChem}, volume = {7}, number = {4}, year = {2015}, month = {FEB}, pages = {588-594}, publisher = {WILEY-V C H VERLAG GMBH}, type = {Article}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

An attempt was made to shift the temperature regime of oxidation catalysis towards ambient temperatures by employing surface modification (SM) as a handle. Systematic SM of Pd(111) was performed by O-atom diffusion into the subsurfaces. Virgin and modified Pd(111) catalysts were evaluated for CO oxidation. Typical CO poisoning observed on virgin surfaces was partially lifted, and ambient CO oxidation was observed on the modified surfaces. CO oxidation was followed by the molecular beam method and near-ambient pressure (NAP) photoelectron spectroscopy under different pressure regimes. UV valence band spectral analysis of the SM and the CO+O-2 reaction on modified Pd(111) surfaces under NAP conditions demonstrated changes in the electronic structures of the surfaces with a change in surface potential by 0.35eV and directly probed CO2 formation under the reaction conditions. Supported metal catalysts may be subjected to SM and evaluated for a shift in the catalysis regime for many different reactions.

}, keywords = {heterogeneous catalysis, Oxidation, photoelectron spectroscopy, surface chemistry, surface modification}, issn = {1867-3880}, doi = {10.1002/cctc.201402979}, author = {Gopinath, Chinnakonda S. and Roy, Kanak and Nagarajan, Sankaranarayanan} } @article { ISI:000347609400069, title = {Efficient Ag-nanoparticle embedded semi-IPN hydrogel for catalytic applications}, journal = {RSC Advances}, volume = {5}, number = {10}, year = {2015}, month = {DEC}, pages = {7567-7574}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Silver nanoparticle embedded semi-IPN hydrogels based on a combination of poly(acrylamide) and poly(aspartic acid) were synthesized. These semi-IPN hydrogel networks can potentially serve as micro or nano reactors for entrapment of metal nanoparticles. Current methodology allows us to entrap metal nanoparticles throughout hydrogel networks via poly(aspartic acid) chains which are dispersed homogeneously in the gel matrix. The Ag-NPs were characterized by UV-vis absorption spectroscopy, transmission electronic microscopy (TEM), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDAX). The Ag embedded hydrogels catalyze the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH4 very efficiently at room temperature with good recyclability upto 3 cycles.

}, issn = {2046-2069}, doi = {10.1039/c4ra14594a}, author = {Patwadkar, Manjusha V. and Gopinath, Chinnakonda S. and Badiger, Manohar V.} } @article { ISI:000359234100023, title = {M-Au/TiO2 (M = Ag, Pd, and Pt) nanophotocatalyst for overall solar water splitting: role of interfaces}, journal = {Nanoscale}, volume = {7}, number = {32}, year = {2015}, month = {JUL}, pages = {13477-13488}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

M-Au/TiO2 (M = Ag, Pd, Pt) composites were prepared through a facile one-pot photodeposition synthesis and evaluated for solar water splitting (SWS) with and without a sacrificial agent. The M-Au combination exhibits a dominant role in augmenting the H2 generation activity by forming a bi-metallic system. Degussa P25 was used as a TiO2 substrate to photodeposit Au followed by Au + M (M = Ag/Pd/Pt). The SWS activity of the M-Au/TiO2 was determined through photocatalytic H-2 production in the presence of methanol as a sacrificial agent under one sun conditions with an AM1.5 filter. The highest H-2 yield was observed for Pt-0.5-Au-1/TiO2 and was around 1.3 +/- 0.07 mmol h(-1) g(-1), with an apparent quantum yield (AQY) of 6.4\%. Pt-0.5-Au-1/TiO2 also demonstrated the same activity for 25 cycles of five hours each for 125 h. Critically, the same Pt-0.5-Au-1/TiO2 catalyst was active in overall SWS (OSWS) without any sacrificial agent, with an AQY = 0.8\%. The amount of Au and/or Pt was varied to obtain the optimum composition and it was found that the Pt0.5-Au1/TiO2 composition exhibits the best activity. Detailed characterization by physico-chemical, spectral and microscopy measurements was carried out to obtain an in-depth understanding of the origin of the photocatalytic activity of Pt-0.5-Au-1/TiO2. These in-depth studies show that gold interacts predominantly with oxygen vacancies present on titania surfaces, and Pt preferentially interacts with gold for an effective electron-hole pair separation at Pt-Au interfaces and electron storage in metal particles. The Pt in Pt-0.5-Au-1/TiO2 is electronically and catalytically different from the Pt in Pt/TiO2 and it is predicted that the former suppresses the oxygen reduction reaction.

}, issn = {2040-3364}, doi = {10.1039/c5nr03735b}, author = {Melvin, Ambrose A. and Illath, Kavya and Das, Tanmay and Raja, Thirumalaiswamy and Bhattacharyya, Somnath and Gopinath, Chinnakonda S.} } @article { ISI:000363668200036, title = {Multifaceted core-shell nanoparticles: superparamagnetism and biocompatibility}, journal = {New Journal of Chemistry}, volume = {39}, number = {11}, year = {2015}, month = {AUG}, pages = {8513-8521}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

NicoreAgshell nanoparticles were synthesized by redox transmetallation reaction. Reduction potential match was encouraging to attempt the synthesis of the NicoreAushell system too. However, it could be achieved only after an effective surface modification on the Ni-core. Thorough characterization (UV-Vis spectroscopy, fluorescence spectroscopy, XRD, XPS, FTIR, TEM, and EDX) proved the necessity of surface modification and the success of synthesis of both types of core-shell structures. The chemical composition and topography were determined using STEM-HAADF analysis and EFTEM imaging. Fourier transform infrared (FTIR) spectroscopy confirmed the surface modification of Ni nanoparticles and the interactions involved between the ligands and metals (in the core and/or the shell) at various steps of the synthetic process. Even after the formation of the noble metal shell, the magnetic core was found to retain its superparamagnetic nature. In addition, the Au-shell protected the core from aerial oxidation and decreased toxicity as compared to pristine Ni nanoparticles as observed by MTT assay on normal cells (PBMCs).

}, issn = {1144-0546}, doi = {10.1039/c5nj01481f}, author = {Sardar, Debasmita and Neogi, S. K. and Bandyopadhyay, Sanjoy and Satpati, Biswarup and Ahir, Manisha and Adhikary, Arghya and Jain, Ruchi and Gopinath, Chinnakonda S. and Bala, Tanushree} } @article { ISI:000356515900042, title = {Rational approach towards enhancing solar water splitting: a case study of Au-RGO/N-RGO-TiO2}, journal = {Nanoscale}, volume = {7}, number = {25}, year = {2015}, month = {MAY}, pages = {11206-11215}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A rational approach was employed to enhance the solar water splitting (SWS) efficiency by systematically combining various important factors that helps to increase the photocatalytic activity. The rational approach includes four important parameters, namely, charge generation through simulated sunlight absorption, charge separation and diffusion, charge utilization through redox reaction, and the electronic integration of all of the above three factors. The complexity of the TiO2 based catalyst and its SWS activity was increased systematically by adding reduced graphene oxide (RGO) or N-doped RGO and/or nanogold. Au-N-RGO-TiO2 shows the maximum apparent quantum yield (AQY) of 2.46\% with a H-2 yield (525 mu mol g(-1) h(-1)) from aqueous methanol, and overall water splitting activity (22 mu mol g(-1) h(-1); AQY = 0.1\%) without any sacrificial agent under one sun conditions. This exercise helps to understand the factors which help to enhance the SWS activity. Activity enhancement was observed when there is synergy among the components, especially the simulated sunlight absorption (or one sun conditions), charge separation/conduction and charge utilization. Electronic integration among the components provides the synergy for efficient solar light harvesting. In our opinion, the above synergy helps to increase the overall utilization of charge carriers towards the higher activity.

}, issn = {2040-3364}, doi = {10.1039/c5nr02613j}, author = {Bharad, Pradnya A. and Sivaranjani, Kumarsrinivasan and Gopinath, Chinnakonda S.} } @article { ISI:000350842300005, title = {Recent developments in solar H-2 generation from water splitting}, journal = {Journal of Chemical Sciences}, volume = {127}, number = {1}, year = {2015}, month = {JAN}, pages = {33-47}, publisher = {INDIAN ACAD SCIENCES}, address = {C V RAMAN AVENUE, SADASHIVANAGAR, P B \#8005, BANGALORE 560 080, INDIA}, abstract = {

Hydrogen production from water and sunlight through photocatalysis could become one of the channels, in the not-so-distant future, to meet a part of ever growing energy demands. However, accomplishing solar water splitting through semiconductor particulate photocatalysis seems to be the {\textquoteleft}Holy Grail{\textquoteright} problem of science. In the present mini-review, some of the critical strategies of semiconductor photocatalysis are focused with the aim of enumerating underlying critical factors such as visible light harvesting, charge carrier separation, conduction and their utilization that determine the quantum efficiency. We attempted to bring out the essential requirements expected in a material for facile water splitting by explaining important and new designs contributed in the last decade. The newly emerged designs in semiconductor architecture employing nanoscience towards meeting the critical factors of facile photocatalysis are elucidated. The importance of band gap engineering is emphasized to utilize potential wide band gap semiconductors. Assistance of metal nanostructures and quantum dots to semiconductors attains vital importance as they are exuberant visible light harvesters and charge carrier amplifiers. Benevolent use of quantum dots in solar water splitting and photoelectrochemical water splitting provides scope to revolutionize the quantum efficiency by its multiple exciton generation features. A list of drawbacks and issues that hamper the much needed breakthrough in photocatalysis of water splitting is provided to invite attention to address them and move towards sustainable water splitting.

}, keywords = {Hydrogen, nanomaterial, Photocatalysis, quantum dot, Semiconductor, visible light, water splitting}, issn = {0974-3626}, doi = {10.1007/s12039-014-0747-0}, author = {Rajaambal, Sivaraman and Sivaranjani, Kumarsrinivasan and Gopinath, Chinnakonda S.} } @article { ISI:000354255400032, title = {SBA-15-oxynitrides as a solid-base catalyst: effect of nitridation temperature on catalytic activity}, journal = {Angewandte Chemie-International Edition}, volume = {54}, number = {20}, year = {2015}, month = {MAY}, pages = {5985-5989}, publisher = {WILEY-V C H VERLAG GMBH}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

Solid bases, such as SBA-15-oxynitrides, have attracted considerable interest for potential applications as catalysts in important industrial processes. Reported herein is that by simply tuning the temperature of nitridation (ammonolysis), the catalytic activity of these solid bases can be enhanced. Solid-state NMR spectroscopy and XPS studies provided the reasoning behind this change in activity.

}, keywords = {heterogeneous catalysis, Nanostructures, NMR spectroscopy, photoelectron spectroscopy, solid-state structures}, issn = {1433-7851}, doi = {10.1002/anie.201501015}, author = {Singh, Baljeet and Mote, Kaustubh R. and Gopinath, Chinnakonda S. and Madhu, Perunthiruthy K. and Polshettiwar, Vivek} } @article {42830, title = {Attempt to correlate surface physics and chemical properties : molecular beam and Kelvin probe investigations of Ce 1-x Zr x O 2 thin films}, journal = {Physical Chemistry Chemical Physics}, volume = {18}, year = {2016}, month = {SEP}, pages = {27594-27602}, type = {Article}, abstract = {

What is the correlation between physical properties of the surfaces (such as surface potential, electronic nature of the surface), and chemical and catalysis properties (such as chemisorption, sticking probability of surface)? An attempt has been made to explore any correlation that might exist between the physical and chemical properties of thin film surfaces. Kelvin probe microscopy (KPM) and the molecular beam (MB) methods were employed to carry out the surface potential, and oxygen adsorption and oxygen storage capacity (OSC) measurements on Ce1-xZrxO2 thin films. A sol{\textendash}gel synthesis procedure and spin-coating deposition method have been applied to make continuous nanocrystalline Ce1-xZrxO2 (x = 0{\textendash}1) (CZ) thin films with uniform thickness (35{\textendash}50 nm); however, surface roughness and porosity inherently changes with CZ composition. MB studies of O2 adsorption on CZ reveal high OSC for Ce0.9Zr0.1O2, which also exhibits highly porous and significantly rough surface characteristics. The surface potential observed from KPM studies varied between 30 and 80 mV, with Ce-rich compositions exhibiting the highest surface potential. Surface potential shows large changes after reduction or oxidation of the CZ film demonstrating the influence of Ce3+/Ce4+ on surface potential, which is also a key to catalytic activity for ceria-based catalysts. The surface potential measured from KPM and the OSC measured from MB vary linearly and they depend on the Ce3+/Ce4+ ratio. More and detailed studies are suggested to arrive at a correlation between the physical and chemical properties of the surfaces.

}, issn = {1463-9076}, doi = {10.1039/C6CP04700A}, author = {Kolekar, Sadhu K. and Dubey, Anjani and Date, Kalyani S. and Datar, Suwarna and Gopinath, Chinnakonda S.} } @article {42832, title = {Bimetallic and plasmonic Ag-Au on TiO2 for solar water splitting : an active nanocomposite for entire visible light region absorption}, journal = {Chemcatchem}, volume = {8}, year = {2016}, month = {OCT}, pages = {3294-3301}, abstract = {

The current study demonstrates a potential method for maximum utilization of the entire visible light region of the solar spectrum by designing a plasmonic-metals semiconductor composite. A combination of Ag+Au nanoclusters would broaden the visible-light absorption at least between 400 and 650nm. This hypothesis was evaluated through solar water splitting (SWS) activity of Au-TiO2, Ag-TiO2, and Ag on Au-TiO2 (AgAuT) composites. AgAuT bimetallic nanocomposite shows the maximum apparent quantum yield of 3.3\% with hydrogen generation (718molh.g(-1)) from aqueous methanol, and overall water splitting activity (7molg.h(-1), AQY=0.04\%) under one sun conditions. Enhanced photocatalytic activity of AgAuT is partly attributed to the formation of hot electrons. A thin layer of Ag coating on Au particles leads to a core-shell morphology with Au in the core. Fermi level equilibration between metal and titania, and Schottky junction formation are directly demonstrated. The strong electronic interaction between Ag and Au, and with TiO2 is evident from its electron rich character and confirmed by Raman spectroscopy, X-ray photoelectron spectroscopy, photoluminescence, and high-resolution TEM measurements. Electronic factors seem to be responsible for the high rate of hydrogen production.

}, doi = {10.1002/cctc.201600937}, author = {Patra, Kshirodra K. and Gopinath, Chinnakonda S.} } @article {42828, title = {C-H activation of methane to formaldehyde on Ce1-xZrxO2 thin films: a step to bridge the material gap}, journal = {ChemCatChem}, volume = {8}, year = {2016}, month = {DEC}, pages = {3650{\textendash}3656}, type = {Article}, abstract = {

Ce1-xZrxO2 (CZ) thin films were prepared by a combination of sol{\textendash}gel and spin-coating methods and were evaluated for the C-H activation of methane by using a molecular beam set-up with the aim to bridge the material gap. The C-H activation of methane begins at 950 K, and a Ce-rich CZ composition displays a high selectivity (4{\textendash}12 \%) to the partially oxidised product, formaldehyde. A 10{\textendash}12 \% selectivity towards HCHO with 1.6 \% methane conversion was observed with methane-rich CH4/O2 reactant compositions at 1050 K. Short contact times, prevalent under molecular beam conditions, could be a possible reason for HCHO formation. Although combustion products were observed instantly upon shining the mixture of reactants on CZ surfaces, up to 20 s delay was observed before formaldehyde generation, which indicates that the oxygen vacancy migration contributes to the rate-determining step and the diffusion-controlled nature of the reaction. A burst in HCHO generation at the point of molecular beam opening, after beam-closed conditions, suggests that the diffusion of oxygen vacancies to the surface is the reason for HCHO formation. Kinetics results also indicate the necessity of reduction sites for HCHO generation.

}, doi = {10.1002/cctc.201600670}, author = {Dubey, Anjani and Kolekar, Sadhu K. and Gopinath, Chinnakonda S.} } @article {42856, title = {C-H activation of methane to syngas on MnxCe1-x-yZryO2 - a molecular beam study}, journal = {Chemcatchem}, volume = {8}, year = {2016}, month = {JUL}, pages = {2296-2306}, type = {Article}, abstract = {

Mn-doped ceria zirconia thin films (MnxCe1-x-yZryO2, MCZ) were employed as flat model catalyst surfaces for CH4 activation. MCZ films exhibit characteristics of single crystal and powder materials, such as smooth surfaces and porosity. From molecular-beam studies, it has been identified that the oxygen storage capacity increases with Mn content. Mutually exclusive observation of H2O or a mixture of products (CO2+ CO + H-2) occurs, when the reactants was allowed to react directly on MCZ, underscoring their formation or prevention (and consumption), respectively. The results suggest that there is competition and cooperation among different elementary reactions under complementary conditions. From a significant partial oxidation of CH4 through C-H activation, it is found that formation of syngas begins at 700 K and the reaction rate increases with increasing temperature. Kinetic evidences indicate that the reaction proceeds through a combustion-reformation pathway.

}, doi = {10.1002/cctc.201600365}, author = {Dubey, Anjani and Kolekar, Sadhu K. and Gopinath, Chinnakonda S.} } @article {42853, title = {Effective and selective oxidation of 2-butanol over Mn supported catalyst systems}, journal = {Applied Catalysis A-General}, volume = {525}, year = {2016}, month = {SEP}, pages = {237-246}, abstract = {

Oxidation of alcohols to their corresponding aldehydes/ketones is an important reaction in industries as well as in academic perspective. Selective oxidation (Selox) of alcohols like methanol, ethanol and propanol are well studied in literature; however, alcohols like butanol, pentanol, octanol is a challenging task. Selective oxidation of 2-butanol to methyl ethyl ketone (MEK) is an important reaction due to its wide range of applications. Herein, we demonstrated the selective oxidation of 2-butanol to MEK over Mn supported on different oxide supports. A series of MnxOy-Al2O3 (MA), MnxOy-CeO2 (MC), MnxOy-ZrO2 (MZ) and MnxOy-SiO2 (MS) catalysts were prepared by co-precipitation followed by hydrothermal method. As synthesised catalysts were characterised by various physico-chemical characterisation techniques. It was found that the presence of Mn3O4 species in MA and MZ catalysts is responsible for maximum catalytic activity towards 2-butanol oxidation. MA catalyst conferred a maximum 2-butanol conversion of 51\% and 88\% selectivity towards MEK. XPS analysis revealed that Mn in MA catalyst exists in +2 and +3 oxidation states and responsible for 2-butanol oxidation. Moreover it was found that the acidity of the catalyst also plays an important role in catalytic activity. (C) 2016 Published by Elsevier B.V.

}, doi = {10.1016/j.apcata.2016.08.005}, author = {Prabu, Kandasamy and Prabu, Marimuthu and Venugopal, Ashok Kumar and Venugopalan, Aswathy Thareparambil and Sandilya, W. V. Y. Sai and Gopinath, Chinnakonda S. and Raja, Thirumalaiswamy} } @article {42831, title = {Enhancement in rate of photocatalysis upon catalyst recycling}, journal = {Scientific Reports}, volume = {6}, year = {2016}, month = {OCT}, pages = {Article Number: 35075}, abstract = {

Recyclability is an important aspect for heterogeneous photo-catalysts. Ease of recovery and stability of the photo-catalyst in terms of efficiency over the number of cycles are highly desired and in fact it is ideal if the efficiency is constant and it should not decrease marginally with each cycle. Presented here is a seminal observation in which the photocatalytic activity is shown to improve with increasing number of catalytic cycles (it is 1.7 times better after the 1st cycle and 3.1 times better after the 2nd cycle). Specifically, nanorods of pure TiO2 and TiO2 doped with controlled amount of tungsten have been used to degrade two model pollutants: Phenol and Rhodamine B under exclusive visible light illumination. It was found that, in case of 1 mol.\% W incorporation, rate of photocatalysis and also the range of visible light absorption of the photocatalyst increased after the photocatalysis as compared to before photocatalysis. This aspect is unique for doped TiO2 and hence provides an intriguing way to mitigate low photoactivity.

}, doi = {10.1038/srep35075}, author = {Sorathiya, Kalpesh and Mishra, Biswajit and Kalarikkal, Abhishek and Reddy, Kasala Prabhakar and Gopinath, Chinnakonda S. and Khushalani, Deepa} } @article { ISI:000379484200023, title = {Exploration of magnetically separable Ag@AgxNiy core/graded-alloy-shell nanostructures}, journal = {Chemical Communications}, volume = {52}, number = {56}, year = {2016}, month = {JUN}, pages = {8737-8740}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

We report novel bimetallic Ag@AgxNiy core@graded-alloy-shell nanoparticles (CGAS NPs), i.e. single Ag core NPs shelled by an AgxNiy graded alloy and stabilized by the CTAB surfactant employing a novel synthesis method. These Ag@AgxNiy CGAS NPs demonstrated superior catalytic performance in the synthesis of biologically active 3-amino alkylated indoles under green conditions.

}, issn = {1359-7345}, doi = {10.1039/c6cc04087j}, author = {Kumar, Mukesh and Soni, Kiran and Satpati, Biswarup and Gopinath, Chinnakonda S. and Deka, Sasanka} } @article { ISI:000372172800019, title = {Gas-solid interaction of H-2-Ce0.95Zr0.05O2: new insights into surface participation in heterogeneous catalysis}, journal = {Catalysis Science \& Technology}, volume = {6}, number = {6}, year = {2016}, month = {OCT}, pages = {1746-1756}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A direct interaction between a reduction medium (H-2) and a Ce0.95Zr0.05O2 (CZ) solid surface was explored through ambient pressure photoelectron spectroscopy (APPES), with conventional X-ray and He-I photon sources, in H-2 atmosphere up to 0.1 mbar pressure and 773 K. A porous CZ thin film was prepared by a combination of sol-gel and spin-coating methods, and was employed to understand the redox nature of ceria under reduction conditions. The maximum of 45\% Ce3+ along with the corresponding oxygen vacancy was observed due to reduction. An unprecedented decrease in the valence band (VB) energy up to 1.4 eV was observed on reduction along with a narrowing of VB. The highest occupied energy band derived from Ce 4f also shifts closer to E-F. H-2 molecular vibration observed in VB-APPES was employed as a probe to explore the surface potential changes along with the dynamic change in the nature of the surface under reduction conditions. The surface potential decreases by 0.27 eV up to 673 K, and then it reverts by 0.24 eV on further reduction at 773 K for different reasons. Further, an enhancement in the Ce 5d-O 2p interaction occurs at the expense of the Ce 4f-O 2p interaction under the above reduction conditions. Vacuum annealing and H-2 reduction after that show significantly more VB shift and enhanced reduction than H-2 reduction alone. Although Ce reduction occurs on high temperature vacuum annealing of CZ, a significantly lower amount of oxygen vacancies appears. This study shows the dynamic changes in the nature of the surface due to a gas (H-2)-solid (CZ) interaction and ensuing electronic structure changes that influence heterogeneous catalysis. It also underscores the necessity to study the catalytic materials under in situ conditions or closer to that.

}, issn = {2044-4753}, doi = {10.1039/c5cy01428j}, author = {Jain, Ruchi and Dubey, Anjani and Ghosalya, Manoj Kumar and Gopinath, Chinnakonda S.} } @article {42855, title = {Green leaf to inorganic leaf: a case study of ZnO}, journal = {Journal of Nanoscienceand Nanotechnology}, volume = {16}, year = {2016}, month = {SEP}, pages = {9203-9208}, abstract = {

Can we use green leaves, available freely in our gardens, as a template for making inorganic leaf, while retaining the nanospace available within the leaf architecture. The answer is {\textquoteright}yes{\textquoteright}, and it is demonstrated with inorganic leaf made up of ZnO, by intercalating Zn2+ ions into the porous channels of the champa (Plumeria, Magnolia champaca) tree leaves. TEM studies reveal a variety of macro-micro-nanospace available in the inorganic leaf ZnO (IL-ZnO), and suggest the possibility of exploiting the same to produce natural nano-architecture for various applications. A speciality of the present work is the maximum suppression of defects in photoluminescence of IL-ZnO leaf, compared to the commercial ZnO, which is exploited for light harvesting through chemical conversion. Benzene to phenol conversion was studied in UV light and IL-ZnO show significant conversion and yield demonstrating C-H activation at ambient temperature.

}, doi = {10.1166/jnn.2016.12912}, author = {Sathu, Naveen K. and Devaraji, Perumal and Gopinath, Chinnakonda S.} } @article {42854, title = {Palladium supported on fluorite structured redox CeZrO4-δ for heterogeneous suzuki coupling in water: a green protocol}, journal = {Chemistry Select}, volume = {1}, year = {2016}, month = {JUL}, pages = {2673{\textendash}2681}, abstract = {

Pd on redox CeZrO4-δ catalysts was prepared, characterized and their activity was evaluated for Suzuki coupling reaction in water under reflux condition. Fresh and reduced form of 5 \% Pd (R-Pd5) on CeZrO4-δ catalyst exhibited 100 \% conversion in 2.5 and 1 h, respectively. R-Pd5 shows significant activity for wide range of substrate compatibility and for less reactive aryl bromides too. The mechanistic investigations proved the important role of redox CeZrO4-δ support on the catalytic activity. It was observed that the presence of oxygen vacancy along with Ce3+ enhances the activity. 1 wt \% Pd photodeposited on pre-reduced CeZrO4-δ support requires a mere 20 min. for 100 \% conversion of Suzuki coupling. Effect of metal dispersion and particle size on catalytic activity is also discussed. High Pd dispersion with small particle size (4{\textpm}1 nm), particle size preservation after reaction, strong metal-support interaction and no leaching fully suggest the heterogeneous mechanism is operative for Suzuki coupling on 1 wt \% Pd photodeposited on reduced CeZrO4-δ support. Present work hints the possibility of achieving high conversion for Suzuki reaction with very small amount of Pd through better dispersion by taking advantage of redox support and in water.

}, doi = {10.1002/slct.201600655}, author = {Burange, Anand S. and Shukla, Rakesh and Tyagi, Avesh Kumar and Gopinath, Chinnakonda S.} } @article {42861, title = {Porous thin films towards bridging the material gap in heterogeneous catalysis}, journal = {Catalysis, Structure \& Reactivity}, volume = {2}, year = {2016}, month = {MAR}, pages = {1-12}, type = {Article}, abstract = {

An attempt has been made to bridge the material gap, existing between ideal single crystals and real-world powder nanocatalyst employed in surface science and heterogeneous catalysis, respectively. Simple wet chemical method (sol{\textendash}gel and spin-coating deposition) has been applied to make continuous Ce1 - xZrxO2 (x = 0{\textendash}1) (CZ) thin films with uniform thickness (~40 nm) and smooth surface characteristics. Uniform thickness and surface smoothness of the films over a large area was supported by a variety of measurements. Molecular beam (MB) studies of O2 adsorption on CZ surfaces reveals the oxygen storage capacity (OSC), and sticking coefficient increases from 400 to 800 K. Porous nature of Ce-rich CZ compositions enhances O2 adsorption and OSC, predominantly due to O-diffusion and redox nature, even at 400 K. A good correlation exists between MB measurements made on CZ films for oxygen adsorption, and OSC, and ambient pressure CO oxidation on powder form of CZ; this demonstrates the large potential to bridge the material gap. CZ was particularly chosen as a model system for the present studies, since it has been well-studied and a correlation between surface science properties made on thin films and catalysis on powder CZ materials could be a litmus test. Ambient catalysis on ceria-zirconia nanocatalyst correlates well with surface properties measured through molecular beam on thinfilm and close the material gap.

}, doi = {10.1080/2055074X.2015.1133269}, author = {Dubey, Anjani and Kolekar, Sadhu K. and Gnanakumar, Edwin S. and Roy, Kanak and Vinod, C. P. and Gopinath, Chinnakonda S.} } @article { ISI:000369658100031, title = {Seeding of Au on CdSe/CdS nanoplates using Langmuir-Blodgett technique}, journal = {RSC Advances}, volume = {6}, number = {18}, year = {2016}, month = {JAN}, pages = {14658-14665}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Oleyl amine capped CdSe/CdS nanoplates were synthesized by hot injection technique which formed a stable monolayer over both a water subphase and an aqueous HAuCl4 subphase using a Langmuir-Blodgett trough. Au islands were generated at the edge as well as on one specific surface of the flat nanoplates by exploiting the reducing capacity of oleyl amine to form Au nanoseeds from AuCl4- ions. The initial Au nanoseeds changed to a shell surrounding these nanoplates on prolonged exposure to the subphase containing the Au precursor. Monolayer of the hybrid structures was deposited onto suitable substrates for characterization by a number of different techniques and to study the photocatalytic activity. The same substrate with the monolayers could be re-used in several cycles of photocatalysis.

}, issn = {2046-2069}, doi = {10.1039/c5ra26018c}, author = {Das, Subhasis and Satpati, Biswarup and Chauhan, Himani and Deka, Sasanka and Ghosalya, Manoj Kumar and Gopinath, Chinnakonda S. and Bala, Tanushree} } @article {42857, title = {Is there any real effect of low dimensional morphologies towards light harvesting? a case study of Au-rGO-TiO2 nanocomposites}, journal = {Chemistry Select }, volume = {1}, year = {2016}, month = {APR}, pages = {917{\textendash}923}, abstract = {

Nanotube and nanosheet morphologies have been celebrated for their electron transport properties. Present work has been explored to exploit the same by combining 1D TiO2 nanotube (1D-TN) with 2D reduced graphene oxide (rGO) along with nano gold for visible light sensitization for photocatalytic H2 generation under one sun condition and visible light (λ>= 400 nm). Vertical and horizontal electron transport in 1D-TN and rGO, respectively, is combined with the visible light absorption capability of Au nanoparticle. H2 yield (HY) varies between 100 and 655 {\textmu}mol/g.h with an apparent quantum yield between 0.45 and 3.2 \%, respectively, depending on Au/rGO/1D-TN preparation method and reaction conditions. It has been demonstrated that interfacial contact between rGO/1D-TN and Au is crucial for high photocatalytic HY. Preparation method influences charge utilization, and hence HY, to a large extent. Nonetheless, the maximum HY reported in the present work is just comparable to HY reported in literature with the most commonly found spherical morphology, and this leads to a question of, is there any real influence of 1D and/or 2D materials, particularly, towards light harvesting applications?

}, doi = {10.1002/slct.201600182}, author = {Melvin, Ambrose A. and Bharad, Pradnya A. and Illath, Kavya and Lawrence, Meenu P. and Gopinath, Chinnakonda S.} } @article {42858, title = {Three way catalytic converter reactions aspects at near ambient temperatures on modified pd-surfaces}, journal = {Comptes Rendus Chimie}, volume = {19}, year = {2016}, month = {OCT}, pages = {1363-1369}, abstract = {

The dissolution of oxygen in palladium plays an important role in palladium catalysis. The present study shows that the surface modification (SM) due to the dissolution of atomic oxygen into the subsurfaces of palladium can be used as a control to tune its catalytic activity. CO oxidation and NO + H-2 + O-2 reaction was separately carried out on metallic Pd and on surface modified Pd using a molecular beam instrument and the results were compared. The metallic Pd does not show activity below 400 K for both reactions, whereas the SM-Pd shows activity at near-ambient temperatures. The electronic change due to SM was investigated using ambient pressure photoelectron spectroscopy, and the investigation clearly shows the effect of subsurface oxygen in the ambient temperature activity of palladium. (C) 2016 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

}, doi = {10.1016/j.crci.2015.11.019}, author = {Roy, Kanak and Jain, Ruchi and Ghosalya, Manoj Kumar and Reddy, Kasala Prabhakar and Gopinath, Chinnakonda S.} } @article {42892, title = {Ambient CO oxidation on in-situ generated Co3O4 spinel surfaces with random morphology}, journal = {ChemistrySelect}, year = {2017}, month = {JAN}, pages = {431{\textendash}432}, abstract = {

The influence of the Co3O4 morphology on its redox behavior and catalytic performance in the CO oxidation reaction is studied. Three different Co3O4 morphologies were synthesized by precipitation and hydrothermal methods. TEM and SEM observations clearly show the different obtained morphologies: rods, wires and a mixture of plates and cubes. The textural properties depend on the morphology and the redox ones on the particle size. XRD analysis reveals a spinel structure in all solids but a preferential exposition of the [110] plane is presented in the Co3O4 rods. This preferential exposition, along with its higher specific surface area provides the rods with more efficient oxygen storage capacity resulting in an excellent catalytic performance compared to the other two morphologies.

}, doi = {10.1002/slct.201602010}, author = {Dubey, Anjani and Reddy, Kasala Prabhakar and Gopinath, Chinnakonda S.} } @article {43899, title = {Copper Cobalt Sulfide Nanosheets Realizing a Promising Electrocatalytic Oxygen Evolution Reaction}, journal = {ACS Catalysis}, volume = {7}, year = {2017}, month = {SEP}, chapter = {5871-5879}, abstract = {

Nanostructured CuCo2S4, a mixed metal thiospinel, is found to be a benchmark electrocatalyst for oxygen evolution reaction (OER) in this study with a low overpotential, a low Tafel slope, a high durability, and a high turnover frequency (TOF) at lower mass loadings. Nanosheets of CuCo2S4 are realized from a hydrothermal synthesis method in which the average thickness of the sheets is found to be in the range of 815 nm. Aggregated nanosheets form a highly open hierarchical structure. When used as an electrocatalyst, CuCo2S4 nanosheets offer an overpotential value of 310 mV at a 10 mA cm(2) current density, which remains consistent for 10000 measured cycles in a 1 M KOH electrolyte. A chronoamperometric study reveals constant oxygen evolution for 12 h at a 10 mV s(-1) scan rate without any degradation of the activity. Furthermore, the calculated mass activity of the CuCo2S4 electrocatalyst is found to be 14.29 A/g and to afford a TOF value of 0.1431 s(-1) at 310 mV at a mass loading of 0.7 mg cm(-2). For comparison, nanostructures of Co3S4 and Cu0.5Co2.5S4 have been synthesized using a similar method followed for CuCo2S4. When compared to the OER activities among these three thiospinels and standard IrO2, CuCo2S4 nanosheets offered the highest OER activities at the same mass loading (0.7 mg/cm(-2)). Extensive X-ray photoelectron spectroscopy and electron paramagnetic resonance analyses for a mechanistic study reveal that introduction of Cu into the Co3S4 lattice enhances the oxygen evolution and kinetics by offering Cu2+ sites for utilitarian adsorption of OH, O, and OOH reactive species and also by offering a highly active high-spin state of octahedral Co3+ for OER catalysis.

}, keywords = {Bifunctional Electrocatalyst, Catalyst, Cuco2s4, Efficient Electrocatalyst, electrocatalyst, Electronic-structure, Nanoparticles, Nanosheet, oxide, oxygen evolution, performance, Recent Progress, Water oxidation, Water Splitting Hydrogen Evolution}, doi = { 10.1021/acscatal.7b01831}, author = {Chauhan, Meenakshi and Reddy, Kasala Prabhakar and Gopinath, Chinnakonda S. and Deka, Sasanka} } @article {44167, title = {Diverse reactivity trends of Ni surfaces in Au@Ni core-shell nanoparticles probed by near ambient pressure (NAP) XPS}, journal = {Catalysis Science \& Technology}, volume = {7}, year = {2017}, month = {OCT }, pages = {4489-4498}, type = {Article}, abstract = {A mild temperature sequential reduction method in aqueous medium is reported for the synthesis of Au@Ni nanoparticles with a core-shell morphology. The nickel shell thickness with a gold core in the nanostructure can be tuned from 2 nm up to about 10 nm. Near ambient pressure XPS (NAPXPS) studies under oxygen atmosphere show that Au-80@Ni-20 with an extremely thin nickel shell (similar to 2 nm) follows a distinctly different decomposition pathway of metastable Ni(OOH) species compared to those with larger shell thickness which behave more like individual nickel surfaces. Thus, Ni(OOH) on Au-80@Ni-20 decomposes to metallic Ni at 100 degrees C and is found to resist oxidation at 0.1 mbar oxygen at this temperature. Those with a larger nickel shell thickness behave more like monometallic Ni in terms of their decomposition and oxidation properties. The Au@Ni system with an ultra thin metallic nickel overlayer (2 nm) shows high catalytic activity and selectivity for phenylacetylene hydrogenation under mild conditions which outweighs their monometallic counterparts and those with higher nickel shell thickness.}, issn = {2044-4753}, doi = {10.1039/c7cy01070b}, author = {Bharathan, Vysakh A. and Jain, Ruchi and Gopinath, Chinnakonda S. and Vinod, C. P.} } @article {45767, title = {Efficient organic photovoltaics with improved charge extraction and high short-circuit current}, journal = {Journal of Physical Chemistry C}, volume = {121}, year = {2017}, month = {MAR }, pages = {5523-5530}, type = {Article}, abstract = {

Exciton generation, dissociation, free carrier transport, and charge extraction play an important role in the short-circuit current (J(sc)) and power conversion efficiency of an organic bulk heterojunction (BHJ) solar cell (SC). Here we study the impact of band offset at the interfacial layer and the morphology of active layer on the extraction of free carriers. The effects are evaluated on an inverted BHJ SC using zinc oxide (ZnO) as a buffer layer, prepared via two different methods: ZnO nanoparticle dispersed in mixed solvents (ZnO A) and sol-gel method (ZnO B). The device with ZnO A buffer layer improves the charge extraction and J(sc),. The improvement is due to the better band offset and morphology of the blend near the ZnO A/active layer interface. Further, the numerical analysis of current-voltage characteristics illustrates that the morphology at the ZnO A/active layer interface has a more dominant role in improving the performance of the organic photovoltaic than the band offset.

}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.7b01314}, author = {Mohan, Minu and Nandal, Vikas and Paramadam, Sanish and Reddy, Kasala Prabhakar and Ramkumar, Sekar and Agarwal, Sumanshu and Gopinath, Chinnakonda S. and Nair, Pradeep R. and Namboothiry, Manoj A. G.} } @article {44138, title = {Facile synthesis of Al2O3-Pt nanocomposite and its catalytic activity}, journal = {Materials Research Express}, volume = {4}, year = {2017}, month = {NOV}, pages = {Article Number: 115002}, type = {Article}, abstract = {Pt nanoparticles were synthesized on gamma-alumina support in presence of oleic acid which was found to prevent clustering of Pt nanoparticles on the support. Various percentage of Pt loading on the alumina changed the catalytic activity for preferential oxidation of CO at relatively low temperature in H-2 rich stream. Pt nanoparticles when synthesized in absence of oleic acid, were all clustered and did not have any catalytic activity. The presence of oleic acid promoted stability preventing agglomeration of Pt nanoparticles. The catalyst thus prepared was characterized thoroughly and their catalytic activity was studied in details.}, doi = {10.1088/2053-1591/aa9441}, author = {Das, Subhasis and Bordoloi, Ankur and Ghosalya, Manoj Kumar and Gopinath, Chinnakonda S. and Bala, Tanushree} } @article {43705, title = {Facile synthesis of ZnO-Ag nanocomposite and its photocatalytic activity}, journal = {Materials Research Express}, volume = {4}, year = {2017}, month = {MAY}, pages = {Article Number: 055011}, type = {Article}, abstract = {

The evolution of photoactive hybrid materials (e.g. noble metal-semiconductor) has resulted in heterogeneous photocatalysis. We report a facile route for the synthesis of ZnO-Ag nanocomposites with varying percentage of loading of the noble metal, expecting a great boost in the photocatalytic behavior of ZnO. The as prepared material was thoroughly characterized by UV-Vis, FTIR, TEM, FESEM, XRD, XPS analyses. The photocatalytic activities of the nanocomposites have been assessed from the ability to degrade methylene blue dye in aqueous solution. The results suggest that incorporation of Ag nanoparticles on the surface of ZnO particles can enhance catalytic activity in comparison to pure ZnO particles under visible light by minimizing the recombination of photogenerated electron-hole pairs.

}, doi = {10.1088/2053-1591/aa6df1}, author = {Sardar, Debasmita and Maity, Jayeta and Ghosalya, Manoj Kumar and Gopinath, Chinnakonda S. and Bala, Tanushree} } @article {43358, title = {Mechanistic aspects of wet and dry CO oxidation on Co3O4 nanorod surfaces: a NAP-UPS study}, journal = {ACS Omega}, volume = {2}, year = {2017}, month = {MAR}, pages = {828-834}, type = {Jouranl Article}, abstract = {

Catalytic activity, electronic structure, and the mechanistic aspects of Co3O4 nanorod (NR) surfaces have been explored for CO oxidation in dry and wet atmosphere using near-ambient pressure ultraviolet photoelectron spectroscopy. Presence of water with CO + O2 plummets the catalytic activity because of the change in the electronic nature from predominantly oxide (without water in feed) to a Co3O4 surface covered by a few intermediates. However, at >=375 K, the Co3O4 surface recovers and regains the oxidation activity, at least partially, even in the presence of water. This is fully supported by the changes observed in the work function of Co3O4 under wet (H2O + CO + O2) conditions compared with dry (CO + O2) conditions. This study focuses on the comparative CO oxidation rate on Co3O4 NR surfaces and highlights the changes in the electronic structure that occur in the catalyst during the CO oxidation reaction.

}, keywords = {Catalyst, Nano Structures, Power X-Ray Diffraction, spectra, Water Vapor}, doi = {10.1021/acsomega.6b00471}, author = {Ruchi Jain and Gnanakumar, Edwin S. and Gopinath, Chinnakonda S.} } @article {44169, title = {Metallic cobalt to spinel Co3O4-electronic structure evolution by near-ambient pressure photoelectron spectroscopy}, journal = {Journal of Physical Chemistry C}, volume = {121}, year = {2017}, month = {OCT}, pages = {21472-21481}, type = {Article}, abstract = {

In the present study, valence band (VB) and core level photoelectron spectroscopy was carried out to investigate the electronic structural changes from polycrystalline Co to spinel Co3O4, via CoO at near ambient pressures (NAP; similar to 0.1). O-2 Co and H-2-CoOx gas solid oxidative and reductive interactions, respectively, have been explored with UV photons (He I) or low kinetic energy electrons (\<= 16 eV) under NAP conditions. Typical VB features of Co metal, CoOx Co3O4, and a mixed phase between any two adjacent features were observed and well corroborated with core level changes. Very significant and characteristic changes were observed with Co 3d features in the VB for each stage from Co oxidation to Co3O4 as well as Co3O4 reduction to CoOx Co(3O)4 and CoO can be reversibly obtained by alternating the conditions between 0.1 mbar of H-2 at 650 K and 0.1 mbar of O 2 at 400 K, respectively. A meaningful correlation is observed between the changes in work function with cation oxidation state; small changes in the stoichiometry can strongly influence the shift in Fermi level and changes in work function under NAP conditions. Reversible work function changes are observed at a constant BE (similar to 5 ev) between oxidation and reduction conditions. While the O 2 p derived feature for CoOx was observed at throughout the redox conditions, the Co 3d band and molecular oxygen or hydrogen vibration feature shifts significantly underscoring the physicochemical changes, such as charge transfer energy and hence changes in satellite intensity. The peak close to E-F originated from the 3d(6)L final state of the octahedral Co3+ 3d band of Co3O4.

}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.7b06661}, author = {Reddy, Kasala Prabhakar and Jain, Ruchi and Ghosalya, Manoj Kumar and Gopinath, Chinnakonda S.} } @article {43171, title = {Multiple functionalities of Ni nanoparticles embedded in carboxymethyl guar gum polymer: catalytic activity and superparamagnetism}, journal = {Applied Surface Science}, year = {2017}, month = {JAN}, abstract = {Composites comprising of metallic nanoparticles in polymer matrices have allured significant importance due to multifunctionalities. Here a simple protocol has been described to embed Ni nanoparticles in carboxymethyl guar gum (CMGG) polymer. The composite formation helps in the stabilization of Ni nanoparticles which are otherwise prone towards aerial oxidation. Further the nanoparticles retain their superparamagnetic nature and catalytic capacity. Ni-Polymer composite catalyses the reduction of 4-Nitrophenol to 4-Aminophenol very efficiently in presence of NaBH4, attaining a complete conversion under some experimental conditions. Ni-Polymer composite is well characterized using UV{\textendash}vis spectroscopy, FTIR, XPS, powder XRD, TGA, SEM and TEM. A detailed magnetic measurement using superconducting quantum interference device-vibrating sample magnetometer (SQUID-VSM) reveals superparamagnetic behaviour of the composite.}, author = {Sardar, Debasmita and Sengupta, Manideepa and Bordoloi, Ankur and Ahmed, Md. A. and Neogi, S. K. and Bandyopadhyay, Sanjoy and Jain, Ruchi and Gopinath, Chinnakonda S. and Bala, Tanushree} } @article {43827, title = {Possibly scalable solar hydrogen generation with quasi-artificial leaf approach}, journal = {Scientific Reports}, volume = {7}, year = {2017}, month = {JUL}, pages = {Article Number: 6515}, type = {Article}, abstract = {Any solar energy harvesting technology must provide a net positive energy balance, and artificial leaf concept provided a platform for solar water splitting (SWS) towards that. However, device stability, high photocurrent generation, and scalability are the major challenges. A wireless device based on quasi-artificial leaf concept (QuAL), comprising Au on porous TiO2 electrode sensitized by PbS and CdS quantum dots (QD), was demonstrated to show sustainable solar hydrogen (490 +/- 25 mu mol/h (corresponds to 12 ml H-2 h(-1)) from similar to 2mg of photoanode material coated over 1 cm(2) area with aqueous hole (S2-/SO32-) scavenger. A linear extrapolation of the above results could lead to hydrogen production of 6 L/h.g over an area of similar to 23 x 23 cm(2). Under one sun conditions, 4.3 mA/cm(2) photocurrent generation, 5.6\% power conversion efficiency, and spontaneous H-2 generation were observed at no applied potential (see S1). A direct coupling of all components within themselves enhances the light absorption in the entire visible and NIR region and charge utilization. Thin film approach, as in DSSC, combined with porous titania enables networking of all the components of the device, and efficiently converts solar to chemical energy in a sustainable manner.}, doi = {10.1038/s41598-017-06849-x}, author = {Patra, Kshirodra Kumar and Bhuskute, Bela D. and Gopinath, Chinnakonda S.} } @article {44142, title = {Study on doped heterojunctions in TiO2 nanotubes: an efficient photocatalyst for solar water splitting}, journal = {Scientific Reports}, volume = {7}, year = {2017}, month = {OCT}, pages = {Article Number: 14314}, type = {Article}, abstract = {The two important factors that affect sunlight assisted water splitting ability of TiO2 are its charge recombination and large band gap. We report the first demonstration of nitrogen doped triphase (anatase-rutile-brookite) TiO2 nanotubes as sun light active photocatalyst for water splitting with high quantum efficiency. Nitrogen doped triphase TiO2 nanotubes, corresponding to different nitrogen concentrations, are synthesized electrochemically. Increase in nitrogen concentration in triphase TiO2 nanotubes is found to induce brookite to anatase phase transformation. The variation in density of intra-band states (Ti3+ and N 2p states) with increase in nitrogen doping are found to be critical in tuning the photocatalytic activity of TiO2 nanotubes. The presence of bulk heterojunctions in single nanotube of different nitrogen doped TiO2 samples is confirmed from HRTEM analysis. The most active nitrogen doped triphase TiO2 nanotubes are found to be 12 times efficient compared to pristine triphase TiO2, for solar hydrogen generation. The band alignment and charge transfer pathways in nitrogen doped TiO2 with triphase heterojunctions are delineated. Bulk heterojunctions among the three phases present in the nanotubes with intra-band defect states is shown to enhance the photocatalytic activity tremendously. Our study also confirms the theory that three phase system is efficient in photocatalysis compared to two phase system.}, doi = {10.1038/s41598-017-14463-0}, author = {Preethi, L. K. and Antony, Rajini P. and Mathews, Tom and Walczak, Lukasz and Gopinath, Chinnakonda S.} } @article {43814, title = {Water mediated deactivation of Co3O4 naonrods catalyst for CO oxidation and resumption of activity at and above 373 K: electronic structural aspects by NAPPES}, journal = {Journal of Physical Chemistry C}, volume = {121}, year = {2017}, month = {SEP}, pages = {20296{\textendash}20305}, type = {Journal Article}, chapter = {20296-20305}, abstract = {

The catalytic activity of the Co3O4 nanorods (NRs) for the CO oxidation reaction and the effect of water on the catalytic reaction have been explored with near-ambient pressure photoelectron spectroscopy (NAPPES) and mass spectral analysis. Comparative NAPPES studies have been employed to understand the elucidation of the catalytic reaction pathway and the evolution of various surface species. The results confirm the suppression of the CO oxidation activity on the Co3O4 NRs in the presence of water vapor. Various type of surface species, such as CO(ads), hydroxyl, carbonate, formate, are found to be present on the catalyst surface depending on the reaction conditions. Vibrational features of CO, O-2, and CO, were observed and shift in binding energy of these features under the reaction conditions directly suggests a change in work function of the catalyst surface. Under dry conditions, CO couples with labile 0 atoms to form CO2; however, under wet conditions, CO predominantly interacts with surface OH groups resulting in the formation of carbonate and formate intermediates. In situ studies of oxidation of CO on Co3O4 shows that CO oxidation depends not only on surface Co3+ concentration but also influenced by Co-3/Co{\textquoteright} ratio on the catalyst surface. The carbonate was found to be a reaction inhibitor at room temperature; however, it acts as an active intermediate at 375 K and above. Above the boiling point of water, Co3O4 NR surfaces begin to show the oxidation activity even in the presence of water vapor. The intrinsic role of intermediate species was used to derive a possible reaction mechanism under different reaction conditions.

}, keywords = {Ambinent-temprature, carbon monoxide, Gas Shift, H Activation, In-situ, Low-temprature oxidation, Molecular-beam, Performance enhancement, Ray Photoelectron-Spectroscopyu, Thin-films}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.7b05480}, author = {Jain, Ruchi and Reddy, Kasala Prabhakar and Ghosalya, Manoj Kumar and Gopinath, Chinnakonda S.} } @article {45470, title = {CuOx-TiO2 composites: electronically integrated nanocomposites for solar hydrogen generation}, journal = {ChemistrySelect }, volume = {3}, year = {2018}, month = {NOV}, pages = {12022-12030}, type = {Article }, abstract = {

CuOx-TiO2 (CT) composites were prepared by different methods (impregnation, microwave and photodeposition methods) and evaluated for solar water splitting (SWS) with aqueous methanol. CT composites prepared by three different methods were characterized by relevant methods to understand the correlation between synthesis method and activity, and the mechanism of water splitting. A comparison of photocatalytic activity of CT composite materials indicates that the photocatalyst prepared by photodeposition method shows significantly improved activity for hydrogen production from aqueous methanol as well as with water (overall water splitting) under one sun conditions. Cu is present in Cu/Cu+1 form in photodeposition method prepared CT, which is more effective and helpful for solar light absorption as well as charge carrier separation due to the formation of bulk p-n (Cu2O-TiO2) heterojunctions. However, CuO formation seems to decrease the activity with other preparation methods.

}, issn = { 2365-6549}, doi = { 10.1002/slct.201802047}, author = {Bharad, Pradnya A. and Nikam, Arun, V. and Thomas, Femi and Gopinath, Chinnakonda S.} } @article {44211, title = {Deposition of Au nanoparticles inside porous CeO2 nanocubes using Langmuir-Blodgett technique}, journal = {New Journal of Chemistry}, volume = {42}, year = {2018}, month = {JAN }, pages = {1379-1386}, type = {Article}, abstract = {

Porous 3D CeO2 nanocubes were synthesized using hot injection technique. These nanocubes were able to form a stable monolayer over water and HAuCl4 subphase in Langmuir-Blodgett (LB) trough due to the presence of surface capped oleic acid and oleylamine. CeO2-Au nanocomposites were synthesized exploiting the ability of oleylamine to reduce AuCl4 ions to Au-0, via LB method. CeO2 nanocubes gave rise to excellent long-range assembly at air/water interface and gold nanoparticles were formed inside these porous nanocubes without disturbing this arrangement. The formation of a stable monolayer was evidenced from the surface pressure-area (P-A) isotherm. The development of Au nanoparticles was confirmed with great effort from a comprehensive study using UV-Vis spectroscopy, XRD, XPS, FTIR, TEM, STEM, EDX, tomography and chemical mapping.

}, issn = {1144-0546}, doi = {10.1039/c7nj03948d}, author = {Das, Subhasis and Bhattacharjee, Gourab and Satpati, Biswarup and Kumar, Mukesh and Deka, Sasanka and Ghosalya, Manoj Kumar and Gopinath, Chinnakonda S. and Bala, Tanushree} } @article {45439, title = { Enhanced microwave absorption property of reduced graphene oxide (RGO)-strontium hexaferrite (SF)/poly (vinylidene) fluoride (PVDF)}, journal = {Dimond and Related Materials}, volume = {89}, year = {2018}, month = {OCT}, pages = {28-34}, type = {Article}, abstract = {Enormous growth in the use of electronic gadgets presents a challenge to develop efficient electromagnetic interference (EMI) shielding materials specifically using composites with properties such as light weight and high shielding due to absorption. In the present work we have synthesized a composite material with three components; Reduced Graphene Oxide (RGO) and Strontium Hexaferrite (SrFe12O19) (SF) bound together by polymer Poly (Vinylidene) Fluoride (PVDF). Composite RGO/SF (RGOSF) was prepared by facile one port chemical reduction method. Surface anchoring of similar to 500 nm of magnetic particles over the graphene sheet was confirmed by Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM). Crystal structure of SF particles was analyzed before and after composite formation with RGO. Effective crystallite size was estimated from both XRD and Raman Spectroscopy which showed similar trend moving from SF to RGOSF to RGOSFPVDF. Polymer composite films of RGOSFPVDF were prepared by hot pressing. Both real and imaginary part of magnetic and dielectric parameters were studied. It was observed that enhancement of interfacial polarization and anisotropic heat loss in PVDF matrix was generated by RGOSF which ultimately created more scattering center and helped in absorption of electromagnetic radiation. Critical film thickness of 3 mm was capable to shield up to 33 dB EM energy of which > 99.9\% was due to absorption.}, issn = { 0925-9635}, doi = {10.1016/j.diamond.2018.07.024}, author = {Acharya, Sanghamitra and Gopinath, Chinnakonda S. and Alegaonkar, Prashant and Datar, Suwarna} } @article {44212, title = {Harnessing visible-light and limited near-IR photons through plasmon effect of gold nanorod with AgTiO2}, journal = {Journal of Physical Chemistry C}, volume = {122}, year = {2018}, month = {JAN }, pages = {1206-1214}, type = {Article}, abstract = {

The utilization of the red-green-blue (RGB) and limited near-IR photons for solar hydrogen evolution (SHE) has been reported in a single plasmonic nanocomposite. Present study describes the use of AgTiO2 (AgT) decorated with Au nanorods (AgT-AuNR) to enhance the absorption of entire visible-light and limited near-IR wavelength range in the sunlight for SHE from photocatalytic water splitting reaction. It is demonstrated that the longitudinal plasmon resonance of AuNR in AgT-AuNR induces SHE between 550 and 800 nm, whereas TiO2-AuNR or AgT shows no activity in this wavelength range. The key aspect of achieving the high photocatalytic activity of AgT-AuNR in the solar spectrum is the electronic integration among metal NPs as well as with TiO2, and the heterojunctions among them. Presence of such heterojunctions has been supported by different characterization studies. However, gold nanorod exhibits field effect and further enhances light harvesting. Although the absolute amount of energy harvested only from near-IR photons is low, when combined with high-energy visible-light photons within one sun conditions, it shows a multiplier effect rather than a simple additive effect. Likely, this is the first report, where SHE has been achieved with significant amount of light absorption at lambda \>= 550 nm with a plasmonic nanocomposite.

}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.7b10289}, author = {Patra, Kshirodra Kumar and Gopinath, Chinnakonda S.} } @article {45423, title = {Mapping valence band and interface electronic structure changes during the oxidation of Mo to MoO3 via MoO2 and MoO3 reduction to MoO2: A NAPPES study}, journal = {Journal of Physical Chemistry C}, volume = {122}, year = {2018}, month = {OCT}, pages = {23034-23044}, type = {Article}, abstract = {

Tuning the surface energetics, especially work function (phi) of the materials, is of a great deal of interest for a wide range of surface- and interface-based devices and applications. How the phi of a solid surface changes under the reaction conditions is of paramount interest to the chemists, particularly in the areas of surface dependent phenomena such as, catalysis and electrochemistry. In the present study, by using the valence band and core-level photoelectron spectroscopy, surface-electronic changes from Mo to MoO3 via MoO2 was studied under relevant near-ambient pressure (NAP) and high temperature conditions. A very significant change in phi from Mo to MoO3 was observed and it is well corroborated with the changes in gas-phase vibrational features of O-2 in both near-ambient pressure ultraviolet photoelectron spectra (NAPUPS) as well in NAP X-ray photoelectron spectroscopy. Reversible changes in the electronic structure is observed when MoO3 was reduced in H-2 to MoO2. On the basis of the extent of oxidation/reduction of MoOx NAPUPS has shown, one or two additional peaks in the band gap at 0.6 and 1.6 eV below the Fermi level. Mo5+ features are identified in the VB and in the Mo 3d core levels with distinct features. Mo5+ features are also stable and essential to bridge MoO2 and MoO3 layers, and their co-existence. In addition, characteristic changes in Mo 4d and O 2p features observed from Mo to MoO3 and well corelated to the band gap of MoO3. Oxidation and reduction propagate from the surface to bulk; indeed, this has significant implications in surface-dependent phenomena. The present study demonstrates (a) the uniqueness of NAPUPS in identifying the subtle to large changes in the electronic structure on solid surfaces under common oxidation and reduction (in general, under reaction) conditions, and (b) relevance of NAPUPS to all surface dependent phenomena, such as catalysis and electrochemistry.

}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.8b07024}, author = {Reddy, Kasala Prabhakar and Mhamane, Nitin B. and Ghosalya, Manoj Kumar and Gopinath, Chinnakonda S.} } @article {44194, title = {Marginally hydrogenated triphasic titania nanotubes for effective visible-light photocatalytic hydrogen generation}, journal = {Energy Technology}, volume = {6}, year = {2018}, month = {FEB}, pages = {280-288}, type = {Article}, abstract = {

We report the first demonstration of hydrogen-annealed triphase TiO nanotubes (anatase-rutile-brookite) (T-ARB) as a visible-light-active photocatalyst for water splitting with high quantum efficiency. As-synthesized T-ARB was annealed under hydrogen atmosphere at 250 and 4508 degrees C for 2 h. We found that the tubular structures were retained in the hydrogenated TiO2 samples. It was observed that the concentrations of Ti3+ and the oxygen vacancies and their distribution significantly increased with respect to the hydrogen annealing temperature. Such changes in defects were found to be critical in enhancing the photocatalytic activity of the hydrogen-annealed triphase TiO2 nanotubes. The triphase TiO2 nanotubes hydrogen annealed at 450 degrees C were 16 times more efficient than pristine TiO2. Such an increase in the photocatalytic activity was explained by a triphase band diagram with defect states below the conduction band of each phase, which facilitated visible-light activity and easy transfer of charge carriers from one phase to another. Our study showed that the well-designed multiphase construction with oxygen vacancies enhanced the photocatalytic activity tremendously owing to the presence of a higher number of phase junctions.

}, keywords = {charge transfer, Defects, Hydrogenation, titania, water splitting}, issn = {2194-4288}, doi = {10.1002/ente.201700406}, author = {Preethi, Laguduva K. and Mathews, Tom and Walczak, Lukasz and Gopinath, Chinnakonda S.} } @article {45395, title = {New strategy toward a dual functional nanocatalyst at ambient conditions: influence of the Pd-Co interface in the catalytic activity of Pd@Co core-shell nanoparticles}, journal = { ACS Applied Materials \& Interfaces }, volume = {10}, year = {2018}, month = {DEC }, pages = {41268-41278}, type = {Article}, abstract = {

Bimetallic nanostructures with a combination of noble and nonnoble metals hold promise for improving catalyst activity and selectivity. Here, we report the synthesis of Pd@Co (PC) core shell morphology nanoparticles with three different ratios of palladium (Pd) and cobalt (Co), and a possibility to fine tune the ratio of core and shell thickness. PC exhibits superior and selective hydrogenation as well as oxidation catalytic activity at ambient or near-ambient conditions. Various characterization techniques have been employed to confirm the core shell morphology. Without any pre-treatment or activation, fresh catalysts with different Pd to Co ratios, that is, 2:1, 1:1, and 1:2, were subjected to olefin (phenylacetylene) hydrogenation and oxidation (styrene to styrene oxide) reaction. The catalytic activity results demonstrate that the 1:1 ratio of Pd/Co is the most active composition for controlled and stepwise reduction of phenyl acetylene to styrene and then to ethyl benzene; 1:1 Pd/Co shows 100\% styrene conversion in 30 min. with an order of magnitude higher turnover frequency than other catalysts. The 1:1 PC ratio is also the most active composition for selective oxidation of styrene to styrene oxide. NAPXPS (near-ambient pressure XPS) results show that the active sites for catalytic hydrogenation and oxidation reaction are Co and Co3+, respectively. However, the superior catalytic performance can be attributed to Co (for reduction) or Co3+ (for oxidation), and the Pd Co interface plays a critical role in stabilizing the required functional character. NAPXPS results confirm that the superior catalytic performance can be attributed not only to Co or Co3+, but also to the Pd Co interface. The electronic effect and synergism between Co and Pd helps Co to stabilize in different oxidation states depending on the reaction conditions, and making it a dual functional catalyst.

}, issn = {1944-8244}, doi = {10.1021/acsami.8b12940}, author = {Jain, Ruchi and Gopinath, Chinnakonda S.} } @article {44215, title = {Pt - g-C3N4 - (Au/TiO2): electronically integrated nanocomposite for solar hydrogen generation}, journal = {International Journal of Hydrogen Energy}, volume = {43}, year = {2018}, month = {JAN}, pages = {601-613}, type = {Article}, abstract = {

A potential nanocomposite photocatalyst was designed by integrating Pt nanoclusters (co catalyst and electron sink) with graphitic carbon nitride (g-C3N4 (gcn)) (charge diffusion) and 0.5 wt \% Au containing Au-TiO2 (AuT) (plasmonic on semiconductor) for solar water splitting (SWS). Variety of Pt-gcn-AuTiO2 compositions has been evaluated for SWS under one sun conditions. Complexity of the photocatalyst was increased systematically from Au-TiO2, gcn-TiO2 to Pt-gcn-Au-TiO2 to explore the influence of different combinations. Electronic integration of charge separation/diffusion component (gcn) with light absorbing sensitizer components (Au and gcn), and co-catalyst (Pt) seems to be the critical factor to improve hydrogen yield (HY) or overall efficiency. Although addition of gcn increase the HY of composites, there is no SWS activity observed on bare TiO2 or gcn. Au or Pt on gcn enhances the charge separation effectively and interface between Au and/or Pt with gcn works as the Schottky barrier. A monodispersion of Au over TiO2 and Pt nanoclusters over gcn/AuTiO2 composite lead to the maximum solar hydrogen yield (1.52 mmol/h g) with an apparent quantum yield (AQY) of 7.5\%. Photoelectron and photoluminescence spectral studies confirm the electron transfer from Au to gcn, and Au and/or gcn to titania. A thorough physico-chemical investigation of various composites underscores the electronic integration aspects of the nanocomposite towards storage of electrons in the Pt co-catalyst and hence an effective charge separation and an increase in AQY. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

}, keywords = {Electronic integration, Photocatalysis, Schottky barrier, Solar hydrogen, water splitting}, issn = {0360-3199}, doi = {10.1016/j.ijhydene.2017.11.057}, author = {Devaraji, Perumal and Gopinath, Chinnakonda S.} } @article {44569, title = {Silicon oxidation by NAPPES: From dangling bonds to oxygen islands to 2D SiOx layer to the onset of bulk SiO2 formation}, journal = {Journal of Physical Chemistry C}, volume = {122}, year = {2018}, month = {MAR }, pages = {4331-4338}, abstract = {

Valence band and core level photoelectron spectral measurements at near-ambient pressures (NAP; up to 0.5 mbar) were made in the presence of molecular oxygen to explore the various oxidation stages of silicon surfaces. Dangling bonds feature observed on clean Si-surfaces in the valence band at ultrahigh vacuum decreases dramatically due to oxygen adsorption between ambient temperature and up to 400 K at 0.1 mbar of O-2 pressure. The adsorption of oxygen on dangling bonds appears to be localized as islands; this reflects in the surface heterogeneous character and also responsible for the broadening in the oxygen gas phase vibrational features. This is further supported by an increase in the work function and can be correlated to the presence of Hofer (molecular) precursor. When the temperature was increased to 500 K, molecular precursor species dissociates to form Si-=-0 species. This is fully supported by the change in the Si work function as well as from the observation of oxidized Si species from Si 2p core level spectra. At \>= 600 K, the Si-=-0 species dissociates to form a uniform 2D oxide layer on the silicon surface, which is characterized by the reappearance of sharp vibration features for gas-phase O-2 molecules. This layer is also quite stable up to 800 K and without any further oxidation in the bulk. On increasing the temperature to 850 K at 0.2 mbar oxygen pressure, bulk Si oxidation begins and the work function increases drastically by 1 eV. An angle-dependent Si 2p spectra recorded map out the presence of elemental Si to Si4+ from bulk to the surface, respectively. A simple model is proposed to show the various stage of silicon oxidation. A continuous change in the work function and electronic states observed due to gas-lattice (O-2-Si) interaction indicates the implications for surface-dependent phenomena, such as heterogeneous catalysis, electrochemistry, 2D layered materials.

}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.7b11956}, author = {Ghosalya, Manoj Kumar and Jain, Ruchi and Reddy, Kasala Prabhakar and Gopinath, Chinnakonda S.} } @article {44536, title = {Subtle interaction between Ag and O 2 : a near ambient pressure UV photoelectron spectroscopy (NAP-UPS) investigations}, journal = {Journal of Chemical Sciences}, volume = {130}, year = {2018}, month = {MAR}, pages = {30}, type = {Journal Article}, abstract = {The Ag-O2 interaction, which is at the center-stage of Ag-catalyzed partial oxidation reactions, is studied with NAP-UPS up to 0.2 mbar O2 pressure between 295 and 550 K. Three temperature regimes were identified for distinct Ag-O2 interaction, which are (a) 295{\textendash}390 K, where mainly dissociative chemisorption of O2 happens, (b) 390{\textendash}450 K, where diffusion of O-atoms into the sub-surfaces of Ag is prominent, and (c) >450 K, where metastable oxide forms on polycrystalline Ag surfaces. The work function (WF) of Ag changed from 4.95 (<=390 K) to 5.30 eV (390{\textendash}450 K), and then to 5.7 eV (>=450 K) at 0.1 mbar O2 pressure. Oxygen population in the sub-surfaces imparts crucial modifications to Ag at 390{\textendash}450 K; it makes the surface to be electron-deficient that relates to the change in the WF of Ag and facilitates the formation of space charge layer on Ag surface. Oxygen adsorbed on such modified Ag-surfaces is electrophilic in nature, and this appears at a higher binding energy in core level XPS than the chemisorbed oxygen on metallic Ag. This is supported by angle-dependent NAP-XPS studies. The subsurface population of oxygen in Ag no longer persists at >410 K when the O2 supply is removed. A high ratio of antibonding/bonding O 2p bands suggests the unique silver-oxygen interaction under the measurement conditions.}, keywords = {Electronic Structure, epoxidation, heterogeneous catalysis, Surface Science}, issn = {9743626}, doi = {10.1007/s12039-018-1434-3}, author = {Ghosalya, Manoj Kumar}, editor = {Reddy, Kasala Prabhakar} } @article {46051, title = {Cadmium sulfide nanostructures: influence of morphology on the photocatalytic degradation of erioglaucine and hydrogen generation}, journal = {Applied Surface Science}, volume = {483}, year = {2019}, month = {JUL}, pages = {696-705}, type = {Article}, abstract = {

Size and shape of inorganic materials are known to have great effects on their physical and chemical properties. Here, for the first time we report the visible light driven photocatalytic degradation of erioglaucine - a stable organic dye molecule in the presence of chemically synthesized nanoscale CdS with 1D (nanorods), 2D (nanosheets) and 3D (hierarchical) morphology. Visible light driven photocatalytic degradation efficiency of both 1D and 3D CdS in the removal of erioglaucine are identical. Surprisingly, with 5 min of sonication, the highly crystalline 3D CdS stacked with many thin nanowires containing numerous active surface sites exhibited fourfold enhanced photodegradation efficiency in comparison to 1D and 2D CdS. Scavenger studies revealed that electrons and superoxide radicals are primary reactive species involved in the photodegradation of erioglaucine, while cyclic photodegradation studies revealed the good stability of 3D CdS against photocorrosion. Further, the photocatalytic hydrogen evolution studies also revealed the excellent activity of 3D CdS in comparison to 1D and 2D CdS. Thus, we find that the morphology indeed influences the photocatalytic activity. These results reveal that 3D CdS nanostructures investigated in the present work are efficient photocatalysts that could be fine-tuned for both environmental remediation and hydrogen generation applications.

}, keywords = {Cadmium sulfide, Erioglaucine, Hydrogen evolution, Nanostructures, Photocatalysis}, issn = {0169-4332}, doi = {10.1016/j.apsusc.2019.04.018}, author = {Shenoy, Sulakshana and Jang, Eunyong and Park, Tae Joo and Gopinath, Chinnakonda S. and Sridharan, Kishore} } @article {46190, title = {Direct solar-to-hydrogen generation by quasi-artificial leaf approach: possibly scalable and economical device}, journal = {Journal of Materials Chemistry A}, volume = {7}, year = {2019}, month = {FEB}, pages = {3179-3189}, type = {Article}, abstract = {

Often, a disadvantage in one area of science may become an advantage in another area. In contrast, a successful concept in one area could work for a complementary area of research too. These two philosophies have been successfully used for solar hydrogen generation and they underscore the necessity to connect relevant concepts. We, herein, report a quasi-artificial leaf (QuAL) device in a wireless configuration with a TiO2/Mn-CdS composite and NiCu as a co-catalyst for possibly scalable as well as commercially viable solar hydrogen production under one sun conditions. The device works at no applied potential and generates 10.5 mL h(-1) (16 mL h(-1)) H-2 with Ni5Cu2.5 alloy (Pt) as a co-catalyst, which corresponds to a power conversion efficiency (PCE) of 4.8\% (7.3\%). The significant resemblance of NiCu alloy to Pt in terms of its electrochemical activity and electronic structure makes the device more economical. While the millisecond lifetime of electrons in Mn-CdS is known to help for white light emission, the same factor helps to greatly improve charge utilization for H-2 production in the QuAL device. In contrast, the reabsorption of emitted light is a vexing problem in emission applications; however in the present work, reabsorption is successfully utilized to enhance hydrogen yield. Spectroscopy techniques combined with electrocatalytic studies were employed and the results correlated with solar hydrogen generation, demonstrating this as a new pathway to design better solar-light-harvesting architectures.

}, issn = {2050-7488}, doi = {10.1039/c8ta11307f}, author = {Patra, Kshirodra Kumar and Bharad, Pradnya Arunrao and Jain, Vanshika and Gopinath, Chinnakonda S.} } @article {46350, title = {Electronic integration and thin film aspects of Au-Pd/rGO/TiO2 for improved solar hydrogen generation}, journal = {ACS Applied Materials \& Interfaces}, volume = {11}, year = {2019}, month = {SEP}, pages = {32869-32878}, type = {Article}, abstract = {

In the present work, we have synthesized noble bimetallic nanoparticles (Au-Pd NPs) on a carbon-based support and integrated with titania to obtain Au-Pd/C/TiO2 and Au-Pd/rGO/TiO2 nanocomposites using an ecofriendly hydrothermal method. Here, a 1:1 (w/w) Au-Pd bimetallic composition was dispersed on (a) high-surface-area (3000 m(2) g(-1)) activated carbon (Au-Pd/C), prepared from a locally available plant source (in Assam, India), and (b) reduced graphene oxide (rGO) (Au-Pd/rGO); subsequently, they were integrated with TiO2. The shift observed in Raman spectroscopy demonstrates the electronic integration of the bimetal with titania. The photocatalytic activity of the above materials for the hydrogen evolution reaction was studied under 1 sun conditions using methanol as a sacrificial agent in a powder form. The photocatalysts were also employed to prepare a thin film by the drop-casting method. Au-Pd/rGO/TiO2 exhibits 43 times higher hydrogen (H-2) yield in the thin film form (21.50 mmol h(-1) g(-1)) compared to the powder form (0.50 mmol h(-1) g(-1)). On the other hand, Au-Pd/C/TiO2 shows 13 times higher hydrogen (H-2) yield in the thin film form (6.42 mmol h(-1) g(-1)) compared to the powder form (0.48 mmol h(-1) g(-1)). While powder forms of both catalysts show comparable activity, the Au-Pd/rGO/TiO2 thin film shows 3.4 times higher activity than that of Au-Pd/C/TiO2. This can be ascribed to (a) an effective separation of photogenerated electron-hole pairs at the interface of Au-Pd/rGO/TiO2 and (b) the better field effect due to plasmon resonance of the bimetal in the thin film form. The catalytic influence of the carbon-based support is highly pronounced due to synergistic binding interaction of bimetallic nanoparticles. Further, a large amount of hydrogen evolution in the film form with both catalysts (Au-Pd/C/TiO2 and Au-Pd/rGO/TiO2) reiterates that charge utilization should be better compared to that in powder catalysts.

}, keywords = {bimetal, Photocatalysis, surface plasmon resonance, TiO2, water splitting}, issn = {1944-8244}, doi = {10.1021/acsami.9b07070}, author = {Tudu, Bijoy and Nalajala, Naresh and Reddy, Kasala P. and Saikia, Pranjal and Gopinath, Chinnakonda S.} } @article {46250, title = { Molybdenum carbide catalyst for the reduction of CO2 to CO: surface science aspects by NAPPES and catalysis studies }, journal = {Dalton Transactions}, volume = {48}, year = {2019}, month = {AUG}, pages = {12199-12209}, type = {Article}, abstract = {

Carbon dioxide is a greenhouse gas, and needs to be converted into one of the useful feedstocks, such as carbon monoxide and methanol. We demonstrate the reduction of CO2 with H-2 as a reducing agent, via a reverse water gas shift (RWGS) reaction, by using a potential and low cost Mo2C catalyst. Mo2C was evaluated for CO2 hydrogenation at ambient pressure as a function of temperature, and CO2 : H-2 ratio at a gas hourly space velocity (GHSV) of 20 000 h(-1). It is demonstrated that the Mo2C catalyst with 1 : 3 ratio of CO2 : H-2 is highly active (58\% CO2 conversion) and selective (62\%) towards CO at 723 K at ambient pressure. Both properties (basicity and redox properties) and high catalytic activity observed with Mo2C around 700 K correlate well and indicate a strong synergy among them towards CO2 activation. X-ray diffraction and Raman analysis show that the Mo2C catalyst remains in the beta-Mo2C form before and after the reaction. The mechanistic aspects of the RWGS reaction were determined by near-ambient pressure X-ray photoelectron spectroscopy (NAPXPS) with in situ generated Mo2C from carburization of Mo-metal foil. NAPXPS measurements were carried out at near ambient pressure (0.1 mbar) and various temperatures. Throughout the reaction, no significant changes in the Mo2+ oxidation state (of Mo2C) were observed indicating that the catalyst is highly stable; C and O 1s spectral results indicate the oxycarbide species as an active intermediate for RWGS. A good correlation is observed between catalytic activity from atmospheric pressure reactors and the electronic structure details derived from NAPXPS results, which establishes the structure-activity correlation.

}, doi = {10.1039/c9dt01774g}, author = {Reddy, Kasala Prabhakar and Dama, Srikanth and Mhamane, Nitin B. and Ghosalya, Manoj K. and Raja, Thirumalaiswamy and Satyanarayana, Chilukuri V. and Gopinath, Chinnakonda S.} } @article {46135, title = {Morphology-dependent, green, and selective catalytic styrene oxidation on Co3O4}, journal = {Dalton Transactions}, volume = {48}, year = {2019}, month = {APR }, pages = {4574-4581}, type = {Article}, abstract = {

Despite the great successes in the controlled fabrication of nanomaterials with specific composition and morphology, it is still challenging to have the desired control on the defect sites of catalyst materials. For unfolding the mystery of this aspect, catalytic styrene epoxidation was attempted on spinel Co3O4 with two different morphologies, namely, SNR (nanorods prepared by the solvothermal method with the (110) facet), HNR (nanorods prepared by the hydrothermal methodwith the (111) facet) and NC (nanocubes with the (110) facet) were synthesized and subjected to olefin oxidation with O-2. Even without any catalyst pretreatment, all three Co3O4 catalyst systems were found to be active for selective epoxidation of styrene with O-2 at ambient pressure in the liquid phase. The correlation between catalytic activity and selectivity trend suggests that the reaction is highly structure-sensitive and facile on the (110) facet. Temperature-dependent near ambient pressure X-ray photoelectron spectroscopy (NAPXPS) was carried out at 0.1 mbar O-2 pressure to understand the mechanistic aspects. The distinct catalytic activity of NC (110) and SNR (110) can be attributed to the population of defect sites on the catalyst surface. NC morphology with comparatively fewer defect sites shows high activity and selectivity, suggesting that styrene oxidation on Co3O4 is structure-sensitive; however, unlike metal surfaces, fewer defects are more favourable for catalytic styrene epoxidation due to facile adsorption and activation of the substrate and O-2 on Co3+ sites. The present investigations suggest that surface defects need not necessarily increase catalytic activity.

}, issn = {1477-9226}, doi = {10.1039/c8dt05154b}, author = {Jain, Ruchi and Gopinath, Chinnakonda S.} } @article {46237, title = {Oxidative disproportionation of MoS2/GO to MoS2/MoO3-x/RGO : integrated and plasmonic 2D-multifunctional nanocomposites for solar hydrogen generation from near-infrared and visible regions}, journal = {Journal of Physical Chemistry C}, volume = {123}, year = {2019}, month = {SEP}, pages = { 21685-21693}, type = {Article}, abstract = {

Two dimensional (2D) semiconductor materials have been recently demonstrated to be effective plasmonic materials and alternatives to costly noble metals. However, tuning the plasmon resonance of 2D semiconductors and integrating with another material or semiconductor for various applications, such as solar light harvesting, remains a challenge. Herein, we designed a simple and attractive method, which facilitates the diffusion of oxygen from the graphene oxide (GO) layers of the MoS2/GO (MG) composite to oxidize the MoS2 layers significantly due to thermal treatment under inert atmosphere. This is the key step in the formation of MoS2/MoO3-x/RGO (MMR) (x = 0, 0.5, and 1, and all stoichiometries co-exist), due to disproportionation of MoS2/GO, with bulk heterojunctions among the components. The observed behavior is attributed to the oxidation of Mo4+ cations (of MoS2) to higher oxidation states in MMR (Mo(5+ )and Mo6+ of MoO3-x), which also alters the valence-band electronic structure and work function of the resulting composite. The 2D MoO3-x layers with a large amount of Mo5+ oxidation states enables facile charge carrier generation due to plasmonic effect, whereas MoS2 provides active sites for catalysis. The solar H-2 generation was demonstrated in the visible and near-infrared region by combining both the plasmonic and catalytic effects in one composite. These results demonstrate the important role of RGO to provide energy-level alignment, charge carrier diffusion, and help to generate plasmonic effect in the composite.

}, author = {Patra, Kshirodra Kumar and Ghosalya, Manoj Kumar and Bajpai, Himanshu and Raj, Sreeya and Gopinath, Chinnakonda S.} } @article {46343, title = {Phase transfer ceria-supported nanocatalyst for nitrile hydration reaction}, journal = {ACS Omega}, volume = {4}, year = {2019}, month = {OCT }, pages = {16037-16044}, type = {Article}, abstract = {

The present study elaborates the catalytic effect of rare-earth metal oxides (Sm2O3 and La2O3) over ceria as a support phase transfer catalyst. The synthesized catalysts have been subjected to different characterization techniques, such as field-emission scanning electron microscopy, high-resolution transmission electron microscopy, powder X-ray diffraction, N-2 adsorption-desorption (BET surface analysis), temperature-programmed desorption study (NH3/CO2-TPD), Fourier transform infrared, Raman analysis, and X-ray photoelectron spectroscopy to get better insights into the catalytic activity of the catalysts for hydration of nitrile.

}, issn = {2470-1343}, doi = {10.1021/acsomega.9b02173}, author = {Gupta, Nikitra N. and Punekar, Amrin S. and Raj, Karthik Raja E. K. and Ghodekar, Medha M. and Patil, Vipul S. and Gopinath, Chinnakonda S. and Raja, Thirumalaiswamy} } @article {46158, title = {Promising visible-light driven hydrogen production from water on a highly efficient CuCo2S4 nanosheet photocatalyst}, journal = {Journal of Materials Chemistry A}, volume = {7}, year = {2019}, month = {MAR }, pages = {6985-6994}, type = {Article}, abstract = {

Here we report the development of CuCo2S4 nanosheets (NSs) as a promising semiconductor photocatalyst for the first time for water splitting reactions under visible light ( 420 nm) conditions, without the support of any noble metal co-catalyst. These NSs were produced via a simple hydrothermal route and have desirable properties with a band gap of 2.24 eV, and are photo-catalytically active under visible light with an apparent quantum yield (AQY) of 2.48\%. Under visible light, CuCo2S4 NSs exhibit excellent weight-normalized photoactivity that generates approximate to 25900 mol h(-1) H-2 for 1 g of material with sulphide + sulphite as the sacrificial agent under 7.68 mW cm(-2) illumination, which is the best evolution reported for any chalcogenide semiconductor material without any co-catalyst to date with unprecedented long-term operational stability (up to 12 h study time). The rate and number of hydrogen gas molecules produced are 8.2855 x 10(15) s(-1) cm(-2) which remained constant for three catalytic cycles with a turnover frequency (TOF) value of 0.017 s(-1). The effect of Cu substitution on photoactivity was also investigated for comparative studies and it was found that CuCo2S4 NSs show superior activity to Cu0.5Co2.5S4 and Co3S4. These CuCo2S4 NSs absorb the entire visible range of the spectrum from 420 to 800 nm, and have a highly populated density of states at the Fermi level and a high donor concentration of 7.22 x 10(18) cm(-3) which have been evaluated by Mott-Schottky analysis and favourable adsorption of H+ on S-sites and conversion to H-2 corroborate their efficient photocatalytic activity.

}, issn = {2050-7488}, doi = {10.1039/c9ta00391f}, author = {Chauhan, Meenakshi and Soni, Kiran and Karthik, P. E. and Reddy, Kasala Prabhakar and Gopinath, Chinnakonda S. and Deka, Sasanka} } @article {46143, title = {Surfactant free synthesis of Au@Ni core-shell nanochains in aqueous medium as efficient transfer hydrogenation catalyst}, journal = {Applied Catalysis A-General}, volume = {575}, year = {2019}, month = {APR }, pages = {93-100}, type = {Article}, abstract = {

A surfactant free aqueous phase synthesis method is reported for the generation of highly lattice mismatched Au@Ni core-shell nanochains without using any expensive and hazardous organic ligands. As synthesised Au@Ni nanochain structures showed high thermal stability and bulk oxidation resistance up to 300 degrees C. In situ near ambient pressure XPS (NAPXPS) analysis has been done for the bare Au@Ni nanochain surfaces under oxygen atmosphere and at different temperatures which showed evidence for the surface oxidation resistance of naked Au@Ni nanochains up to 200 degrees C. Ligand or capping agent free Au@Ni nanochain surfaces are found to be highly active for transfer hydrogenation of acetophenone to 1-phenyl ethanol an important commodity in perfumery industry.

}, keywords = {Au@Ni nanochains, core-shell, NAPXPS, Surfactant free, synergistic effects, transfer hydrogenation}, issn = {0926-860X}, doi = {10.1016/j.apcata.2019.01.017}, author = {Vysakh, A. B. and Shebin, K. J. and Jain, Ruchi and Sumanta, P. and Gopinath, Chinnakonda S. and Vinod, C. P.} } @article {46189, title = {Why the thin film form of a photocatalyst is better than the particulate form for direct solar-to-hydrogen conversion: a poor man{\textquoteright}s approach}, journal = {RSC Advances}, volume = {9}, year = {2019}, month = {FEB}, pages = {6094-6100}, type = {Article}, abstract = {

We demonstrated an easy method to improve the efficiency of photocatalysts by an order of magnitude by maximizing light absorption and charge carrier diffusion. Degussa titania (P25) and Pd/P25 composite photocatalyst thin films coated over regular glass plates were prepared and evaluated for solar hydrogen production in direct sunlight with aqueous methanol. It is worth noting that only UV light present in direct sunlight (similar to 4\%) was absorbed by the catalysts. The hydrogen production activities of catalysts were compared for thin film and particulate forms at 1 and 25 mg levels. The hydrogen yield values suggested that 1 mg thin film form of Pd/P25 provided 11-12 times higher activity than 25 mg powder form. Comparable light absorption throughout the entire thickness of photocatalyst device and better contact of nanostructures that enabled the charge diffusion and charge utilization at redox sites are the reasons for high efficiency. While solar cells require charge carriers to diffuse through long distances of microns, they are utilized locally in an ensemble of particles (of nanometres) for hydrogen generation in photocatalyst thin films; this concept was used effectively in the present work.

}, issn = {2046-2069}, doi = {10.1039/c8ra09982k}, author = {Nalajala, Naresh and Patra, Kshirodra Kumar and Bharad, Pradnya A. and Gopinath, Chinnakonda S.} } @article {46792, title = {Can half-a-monolayer of pt simulate activity like that of bulk pt? solar hydrogen activity demonstration with quasi-artificial leaf device}, journal = {ACS Applied Materials \& Interfaces}, volume = {12}, year = {2020}, month = {JUL }, pages = {30420-30430}, type = {Article}, abstract = {

Pt is the best cocatalyst for hydrogen production. It is also well-known that the surface atomic layer is critical for catalysis. To minimize the Pt content as cocatalyst, herein we report on half-a-monolayer of Pt (0.5 theta(Pt)) decorated on earth-abundant Ni-Cu cocatalyst, which is integrated with a quasiartificial leaf (QuAL) device (TiO2/ZnS/CdS) and demonstrated for efficient solar hydrogen production. For the QuAL, TiO2 is sensitized with ZnS and CdS quantum dots by the SILAR method. The 0.5 theta(Pt)-decorated Ni-Cu shows an onset potential of 0.05 V vs reversible hydrogen electrode for the hydrogen evolution reaction, which is almost similar to that of commercial Pt/C. Photoactivity of the present QuAL device with either bulk Pt or 0.5 theta(Pt)-coated Ni-Cu cocatalyst is, surprisingly, equal. Our findings underscore that a fraction of a monolayer of Pt can enhance the activity of the cocatalyst, and it is worth exploring further for the high activity associated with atomic Pt and other noble metals.

}, keywords = {artificial leaf, nickel-copper, Photocatalysis, platinum, Solar hydrogen}, issn = {1944-8244}, doi = {10.1021/acsami.0c07431}, author = {Bajpai, Himanshu and Patra, Kshirodra Kumar and Ranjan, Ravi and Nalajala, Naresh and Reddy, Kasala Prabhakar and Gopinath, Chinnakonda S.} } @article {46876, title = {Cu-Ni bimetal integrated TiO2 thin film for enhanced solar hydrogen generation}, journal = {Solar RRL}, volume = {4}, year = {2020}, month = {MAY}, pages = {1900557}, type = {Article}, abstract = {

A series of non-noble Cu-Ni bimetallic catalysts is prepared with different molar proportions of metals. Of these bimetallic catalysts, 1 wt\% is subsequently integrated with titania P25. The catalysts are evaluated for solar hydrogen generation under 1 sun condition in both the powder and thin film forms. All the photocatalysts in the thin film exhibit an 8-24 times higher hydrogen yield (HY) compared with the corresponding particulate counterpart. The highest HY (41.7 mmol h(-1) g(-1)) is demonstrated for the photocatalyst Cu-Ni/TiO2 (CNT; 1:1 = Cu:Ni) in the thin film form, which is 24 times higher than that with its powder counterpart (1.75 mmol h(-1) g(-1)) and exceeds the performance of other Cu-Ni/TiO2 compositions. This enhanced activity in the thin film can be ascribed to improved absorption of visible light and an effective separation of photogenerated charge carriers at the interface of Cu-Ni/TiO2 leading to better charge carrier utilization.

}, keywords = {bimetals, energy conversion, Hydrogen, Photocatalysis, solar energy}, issn = {2367-198X}, doi = {10.1002/solr.201900557}, author = {Tudu, Bijoy and Nalajala, Naresh and Saikia, Pranjal and Gopinath, Chinnakonda S.} } @article {46787, title = {Directed holey and ordered g-C(3)N(4.5)nanosheets by a hard template nanocasting approach for sustainable visible-light hydrogen evolution with prominent quantum efficiency}, journal = {Journal of Materials Chemistry A}, volume = {8}, year = {2020}, month = {JUL}, pages = {13328-13339}, type = {Article}, abstract = {

It is desirable yet challenging to synthesize a highly ordered holey carbon nitride material with excess nitrogen atoms for a sustainable solar H(2)evolution. Herein, we report the development of directed highly ordered nitrogen-rich honeycomb-like mesoporous carbon nitride nanosheets by using a novel synthetic approach for this purpose. The unique formation route, surface structure and charge carrier dynamics of the two dimensional holey nanosheets are comprehensively monitored and confirmed by SAXS, HRTEM, AFM, BET, XPS and TRPL analyses. Non-stoichiometric high nitrogen content mesoporous nanosheets with the final stoichiometry of g-C(3)N(4.5)acquiring a high specific surface area (382 m(2)g(-1)), remarkable pore size (7.2 nm) and sheet thickness similar to 5-6 nm are realized in this first report. This elegant material possesses unique low band-gap energy (2.42 eV). Remarkably, the as-synthesized g-C(3)N(4.5)NSs exhibit a record high photocatalytic H(2)evolution rate of 8180 mu mol g(-1)h(-1)under the present light irradiation (420 \<=lambda \<= 510 nm) condition. The apparent quantum efficiency is found to be as high as 27.14\% at 420 nm and retains its photocatalytic activity for longer consecutive catalytic cycles. Bigger pore size and pore volume, and thin walls leading to shortening of the path length of exciton pairs, efficient charge separation and the prolonged average life time of the charge carriers, and lone electron pairs associated with the excess nitrogen content are found to be the reasons behind the excellent visible light driven water splitting reaction.

}, issn = {2050-7488}, doi = {10.1039/d0ta02734k}, author = {Antil, Bindu and Ranjan, Ravi and Gopinath, Chinnakonda S. and Deka, Sasanka} } @article {46813, title = {Electronic structure evolution of Pd@Co nanocatalysts under oxidation and reduction conditions and preferential CO oxidation}, journal = {ChemCatChem}, volume = {12}, year = {2020}, month = {AUG }, pages = {4176-4184}, type = {Article}, abstract = {

Herein, we present the surface electronic structure and morphological evolution under reduction and oxidation conditions for Pd@Co (PC) core-shell nanoparticles with different Pd : Co ratio (PC=2 : 1, 1 : 1 and 1 : 2). Extensive measurements have been made with NAPXPS (near ambient pressure x-ray photoelectron spectroscopy) under oxidising and reducing conditions, and ex-situ HRTEM. It has been demonstrated that PC catalysts are thermally stable towards morphological changes, at least up to 575 K. Nonetheless, it shows a significant surface electronic structure changes under reaction environments, which are highly relevant to heterogeneous catalysis. As expected, high (low) population of metallic (oxidised) Co was observed, while retaining core shell structure under reduction (H(2)and vacuum annealing) environment. Interestingly, the Pd-Co metallic interface helps to overcome the pyrophoric nature of cobalt and stabilised a significant amount of metallic Co at Pd-Co interface even in the presence of 0.1 mbar O(2)up to 575 K. The presence of Pd-Co and Pd-Co@Co(3)O(4)interfaces in reaction environment makes the catalyst dual functional. The proof of concept has been explored in terms of oxidation of CO in the presence of H(2)or O-2.

}, keywords = {Core-Shell morphology, Electronic Structure, heterogeneous catalysis, interface, XPS}, issn = {1867-3880}, doi = {10.1002/cctc.202000644, Early Access Date = JUN 2020}, author = {Jain, Ruchi and Gopinath, Chinnakonda S.} } @article {46778, title = {Gas-solid interactions with reactive and inert gas molecules by NAPUPS: can work function be a better descriptor of chemical reactivity?}, journal = {Physical Chemistry Chemical Physics}, volume = {22}, year = {2020}, month = {JUL}, pages = {15528-15540}, type = {Article}, abstract = {

The gas-phase vibrational spectra of reactive (H(2)and O-2) and inert gases (N(2)and Ar) have been studied by near-ambient pressure (NAP) ultraviolet photoelectron spectroscopy (NAPUPS) up to 0.3 mbar pressure. The results obtained are divided into two parts and discussed. In the first part, the photoelectron spectra of monoatomic Ar and some homonuclear diatomic molecules, such as H-2, O-2, and N-2, have been recorded by NAPUPS and the effect of pressure on their energy position has been studied. It has been demonstrated that NAPUPS could be an essential tool to determine the intermolecular or interatomic interactions. In the second part, we have evaluated the influence of different solid surfaces on the binding energy (BE) position, the pattern of the vibrational features of diatomic N(2)molecules, and the first atomic levels (3p(3/2)and 3p(1/2)) of monoatomic Ar. It has been observed that with a change in the (electronic/chemical) nature of the surface, the BE of the above features also changes and reflects the change in the work function (phi) of the material. It is to be noted that Ar is an inert/noble gas and N(2)is the most stable molecule, and the above changes observed underscore that they can be employed as probe atoms/molecules to explore even the minor changes that occur on a solid surface due to a variety of reasons. Further, if the solid surface undergoes any chemical/electronic changes due to gas-solid interaction, such as oxidation/reduction, the phi of the surface changes again; this highlights the precise identification of the changes that occur under the reaction/measurement conditions. Therefore, the change in the BE of the gas-phase features can be used to determine even the minor changes in the phi of solid surfaces during the reaction or due to the reaction. The present findings have implications in probing the surface changes that occur in any surface-dependent phenomena, such as heterogeneous catalysis, electrochemistry, and materials that are predominantly controlled by surface contribution, such as layered (2D) materials, nanomaterials.

}, issn = {1463-9076}, doi = {10.1039/d0cp02456b}, author = {Ghosalya, Manoj Kumar and Reddy, Kasala Prabhakar and Mhamane, Nitin B. and Ranjan, Ravi and Gopinath, Chinnakonda S.} } @article {47600, title = {Aqueous methanol to formaldehyde and hydrogen on Pd/TiO2 by photocatalysis in direct sunlight: structure dependent activity of nano-Pd and atomic Pt-coated counterparts}, journal = {ACS Applied Energy Materials}, volume = {4}, year = {2021}, month = {NOV }, pages = {13347-13360}, type = {Article}, abstract = {In the present investigation, facet-controlled Pd nanoparticles with nanocube (Pd-NC) and truncated octahedron (Pd-TO) morphologies, and their counterparts with half-a-monolayer of atomic Pt coated (0.5 theta(Pt)-Pd-NC and 0.5 theta(Pt)-Pd-TO) surfaces were prepared. All of them were characterized and evaluated as cocatalyst after supporting them on commercial titania (P25) (Pd-NC/P25, Pd-TO/P25, 0.5 theta(Pt)-Pd-NC/P25, and 0.5 theta(Pt)-Pd-TO/P25) under direct sunlight and/or one sun conditions for the oxidation of methanol to formaldehyde along with solar hydrogen production. Pd-NC/P25 shows higher activity for hydrogen generation compared to Pd-TO/P25; however, activity reversal occurs with the above cocatalysts, but, after Pt-coating with further enhanced activity. The highest conversion of methanol (0.2 mu mol/h.mg) to 100\% selective formaldehyde was observed with 0.5 theta(Pt)-Pd-TO/P25, while other catalysts show significantly lower methanol conversion in the following order: 0.5 theta(Pt)-Pd-TO/P25 > 0.5 theta(Pt)-Pd-NC/P25 > Pd-NC/P25 > Pd-TO/P25. Pt-coated on (111) facets of Pd-TO simulates the activity associated as that of Pt(111) facets and demonstrating the highest and facet dependent activity. The present study is truly in resonance with exploiting the surface properties for heterogeneous catalysis, and highlights that less than a monolayer of Pt is sufficient to simulate the activity as that of bulk Pt. It is worth exploring this concept to other metals and substrates too.}, keywords = {heterogeneous catalysis, Nanomaterials, Oxidation, Photocatalysis, surface modification}, issn = {2574-0962}, doi = {10.1021/acsaem.1c03080}, author = {Nalajala, Naresh and Salgaonkar, Kranti N. and Chauhan, Inderjeet and Mekala, Siva Prasad and Gopinath, Chinnakonda S.} } @article {47582, title = {Catalytic applications of hydrotalcite and related materials in multi -component reactions: concepts, challenges and future scope}, journal = {Sustainable Chemistry and Pharmacy}, volume = {22}, year = {2021}, month = {SEP}, pages = {100458}, type = {Article}, abstract = {Hydrotalcites (HTs) are the potential substitute to conventional base catalysts. HTs are useful in efficient syntheses of various heterocycles, such as chromenes, pyrans, pyrazoles, triazoles, using multi-component reactions. This review focuses on the chemistry of HTs and particularly hydrotalcites and related materials in the synthesis of heterocycles. The effects of preparation method and, physico-chemical parameters, such as calcination, molar ratio of metals, role of intercalated ions, surface area, on the catalytic activities are discussed. Along with technical aspects, this review also unlocks various untouched areas in developing sustainable catalyst for syntheses of heterocycles, drugs, etc. for the future.}, keywords = {green chemistry, green synthesis, heterocycles, heterogeneous catalysis, hydrotalcite, Metal Oxide}, doi = {10.1016/j.scp.2021.100458}, author = {Burange, Anand S. and Gopinath, Chinnakonda S.} } @article {47589, title = {Electronically integrated mesoporous Ag-TiO2 nanocomposite thin films for efficient solar hydrogen production in direct sunlight}, journal = {Energy Technology}, volume = {10}, year = {2021}, month = {AUG}, pages = {2100356}, type = {Article}, abstract = {

The synthesis of mesoporous TiO2 by a solution-based assembly process and Ag/TiO2 nanocomposites is provided. The efficacy of Ag/TiO2 nanocomposite as photocatalyst in thin-film form is demonstrated for solar hydrogen generation in sunlight. Integration of Ag with TiO2 dramatically enhanced the H-2 production: with 1 wt\% Ag on TiO2 (TiAg-1), the H-2 yield was observed to be 4.59 mmol h(-1) g(-1), which is 2.3 (30) times larger than 0.5 wt\% Ag on TiO2. TiAg-1 shows 4.3 times higher activity in film form compared with its powder counterpart. High photocatalytic efficiency is attributed to the surface plasmon resonance effect of Ag, electronic integration of Ag with TiO2, and subsequent valence band broadening, large distribution of Ag nanoparticles and abundant Ag-TiO2 Schottky junctions, and the later minimizes electron-hole recombination. Interparticle mesoporous network increases necking and the high surface area offers easy accessibility of the reactants to a large number of active sites.

}, keywords = {heterogeneous catalysis, heterojunctions, plasmon effect, Silver, solar energy conversion, Solar hydrogen}, issn = {2194-4288}, doi = {10.1002/ente.202100356}, author = {Mani, Sunesh S. and Rajendran, Sivaraj and Nalajala, Naresh and Mathew, Thomas and Gopinath, Chinnakonda S.} } @article {47440, title = {Green route for carbonylation of amines by CO2 using Sn-Ni-O bifunctional catalyst and theoretical study for finding best suited active sites}, journal = {Chemical Engineering Journal }, volume = {419}, year = {2021}, month = {SEP}, pages = {129439}, type = {Article}, abstract = {

Reaction between n-alkylamine and CO2\ has gained interest due to the demand for the dialkylurea for various applications. For the first time, the tool\ Mathematica\ was used to analyze the experimental data with an idea to derive an equation which determines the best suited active sites for any given input set of dependent parameters. The equation can further be used to predict the product yield with the known values of active sites for a reaction. Among several Sn containing mixed oxides, Sn-Ni oxide (Sn-Ni-O) was found to be the better performing catalyst. The studies indicate that the formation of new defect sites when NiO and SnO2\ are in the mixed state and possibly a solid solution enhances the catalytic efficiency. There are two main reasons for improved catalytic performance; one, mixing of SnO2\ into NiO which reduces the number of holes (h+) localized on lattice oxygen (O2-+ h+{\textrightarrow} O{\textbullet}-) and two, smaller SnO2\ particles are dispersed on the bigger particle NiO which alters the acidic and basic active sites in the catalyst. FT-IR adsorption study with amine and CO2\ helped in deriving a plausible mechanism for this reaction. Under optimized reaction condition, Sn1.1-Ni-O-600 gave 77.3\% of n-butylamine conversion and 75.7\% of yield for 1,3-dibutylurea. The versatility of the catalyst was tested for carbonylation of different aliphatic and aromatic amines, diamine and hydroxy amine with CO2.

}, keywords = {amines, CO2, Mixed oxide catalyst and bi-functional catalyst, Substituted urea}, issn = {1385-8947}, doi = {10.1016/j.cej.2021.129439}, author = {Kulal, Nagendra and Vetrivel, Rajappan and Gopinath, Chinnakonda S. and Ravindran, Rahul K. and Rao, Vinod N. and Shetty, Manjunath and Shrikanth, R. and Rangappa, Dinesh and Shanbhag, Ganapati V.} } @article {47413, title = {Green synthesis of xanthene and acridine-based heterocycles of pharmaceutical importance: a review}, journal = {Environmental Chemistry Letters}, year = {2021}, month = {MAR}, type = {Review; Early Access}, abstract = {

Xanthene and acridine-based heterocyclic compounds find applications in cancer chemotherapy, biological staining and laser dyes and are known for their antibacterial and anti-tumor properties. Here we review green catalytic routes for the synthesis of 1,8-dioxo-octahydroxanthenes, 1,8-dioxo-decahydroacridines and related heterocyclic molecules with catalysts such as metal oxides, mixed metal oxides, resins, supported organocatalysts, heteropolyacids, carbon-based materials, zeolites, sulfides and ionic liquids. We compare protocols for their catalytic activities, and proposed mechanisms are discussed.

}, keywords = {green chemistry, heterocycles, heterogeneous catalysis, Metal oxides, nanocatalysis}, issn = {1610-3653}, doi = {10.1007/s10311-021-01223-w, Early Access Date = MAR 2021}, author = {Burange, Anand S. and Gadam, Komal G. and Tugaonkar, Prajyot S. and Thakur, Seema D. and Soni, Ravish K. and Khan, Rubej R. and Tai, Mubashira S. and Gopinath, Chinnakonda S.} } @article {47754, title = {In-situ experimental and computational approach to investigate the nature of active site in low-temperature CO-PROX over CuOx-CeO2 catalyst}, journal = {Applied Catalysis A-General}, volume = {624}, year = {2021}, month = {AUG }, pages = {118305}, type = {Article}, abstract = {Preferential oxidation (PROX) of carbon monoxide (CO) in presence of excess hydrogen is a necessity to prevent poisoning of the Pt-anode by CO in PEMFCs (Polymer Electrolyte Membrane Fuel Cell). A highly active catalyst, 5 wt\% Cu-CeO2 showed 100 \% CO conversion at 65 degrees C without any undesirable oxidation of H-2. The catalyst showed no deactivation even after 100 h on stream, making it viable for practical fuel cell application. Operando EPR in the PROX reaction condition revealed highly dispersed mixed valent cations with oxygen vacancies, responsible for the low-temperature PROX activity. At the active site, both Cu and Ce ions were shown to reversibly change their valence states to facilitate the abstraction of bridging lattice oxygen for CO oxidation to CO2. This surface oxygen mediated CO oxidation was found to be much faster than that of H-2 to H2O, which could explain the complete selectivity of oxygen for CO2 formation.}, keywords = {CuOx-CeO2, interface, Oxygen vacancy, PROX, Synergistic}, issn = {0926-860X}, doi = {10.1016/j.apcata.2021.118305}, author = {Adak, Shubhadeep and Rabeah, Jabor and Ranjan, Ravi and Khan, Tuhin Suvra and Poddar, Mukesh Kumar and Gupta, Rishi Kumar and Sasaki, Takehiko and Kumar, Sagar and Bordoloi, Ankur and Gopinath, Chinnakonda S. and Bruckner, Angelika and Bal, Rajaram} } @article {47380, title = {One-dimensional multichannel g-C3N4.7 nanostructure realizing an efficient photocatalytic hydrogen evolution reaction and its theoretical investigations}, journal = {ACS Applied Energy Materials}, volume = {4}, year = {2021}, month = {APR }, pages = {3118-3129}, type = {Article}, abstract = {

The emerging metal-free carbon nitride (C3N4) offers prominent possibilities for realizing the highly effective hydrogen evolution reaction (HER). However, its poor surface conductivity and insufficient catalytic sites hinder the HER performance. Herein, a one-dimensional vermicular rope-like graphitic carbon nitride nanostructure is demonstrated that consists of multichannel tubular pores and high nitrogen content, which is fabricated through a cost-effective approach having the final stoichiometry g-C3N4.7 for HER application. The present g-C3N4.7 is unique owing to the presence of abundant channels for the diffusion process, modulated surface chemistry with rich- electroactive sites from N-electron lone pairs, greatly reduced recombination rate of photoexcited exciton pairs, and a high donor concentration (4.26 x 10(17) cm(3)). The catalyst offers a visible-light-driven photocatalytic H-2 evolution rate as high as 4910 mu mol h(-1)g(-1) with an apparent quantum yield of 14.07\% at band gap absorption (2.59 eV, 479 nm) under 7.68 mW cm(-2) illumination. The number of hydrogen gas molecules produced is 1.307 x 10(15) s(-1) cm(-2), which remained constant for a minimum of 18 h of repeated cycling in the HER without any degradation of the catalyst. In density functional theory calculations, a significant change in the band offset is observed due to N doping into the system in favor of electron catalysis. The theoretical band gap of a monolayer of g-C3N4.7 was enormously reduced because of the presence of additional densities of states from the doped N atom inside the band gap. These impurity or donor bands are formed inside the band gap region, which ultimately enhance the hydrogen ion reduction reaction enormously.

}, keywords = {carbon nitride, Density functional theory, hydrogen evolution reaction, nitrogen-rich, Photocatalyst}, issn = {2574-0962}, doi = {10.1021/acsaem.0c02858}, author = {Antil, Bindu and Kumar, Lakshya and Ranjan, Ravi and Shenoy, Sulakshana and Tarafder, Kartick and Gopinath, Chinnakonda S. and Deka, Sasanka} } @article {47702, title = {Rationally designed, efficient, and earth-abundant Ni-Fe cocatalysts for solar hydrogen generation}, journal = {ACS Sustainable Chemistry \& Engineering}, volume = {9}, year = {2021}, month = {OCT }, pages = {13915-13925}, type = {Article}, abstract = {Developing highly efficient and affordable catalysts for solar hydrogen (H-2) generation is crucial, and employing a cocatalyst from earth-abundant elements has a critical role to play. In this context, different compositions of earth-abundant Ni-Fe alloy (1:1, 1:3, and 3:1) have been prepared by hydrothermal method; subsequently, 1 wt \% of these Ni-Fe cocatalysts were integrated with TiO2-P25 and thoroughly characterized. The resultant catalysts have been evaluated for solar H-2 production, in powder and thin film forms, under one sun condition and in direct sunlight. Interestingly, all the catalysts in the thin film form exhibit superior hydrogen yield (HY), up to 27 times higher activity than its powder counterpart. Among the photocatalysts, Ni-Fe/TiO2 (3:1 = Ni/Fe; NFT31) composition exhibits the best HY in thin film (8.27 mmol.h(-1).g(-1)) and exceeds all other compositions of catalyst. It is also to be reported that HY measured for the powder form with 1 mg shows 3-17 times higher activity than that measured with 25 mg. This is mainly attributed to effective solar light absorption with a smaller amount of photocatalyst either spread over large area in a thin film form or well-dispersed in suspension forms. Furthermore, the enhanced activity obtained with Ni-Fe/TiO2 photocatalysts is also ascribed to strong electronic integration of Ni-Fe cocatalyst with TiO2 and higher performance obtained with a thin film is attributed to increased charge carrier generation and subsequent charge separation and effective utilization. A decrease in work function of TiO2 by 0.6 eV was observed after its integration with cocatalyst in NFT31.}, keywords = {Cocatalyst, Hydrogen, Ni-Fe alloy, solar energy, TiO2, water splitting}, issn = {2168-0485}, doi = {10.1021/acssuschemeng.1c05158}, author = {Tudu, Bijoy and Nalajala, Naresh and Reddy, Kasala Prabhakar and Saikia, Pranjal and Gopinath, Chinnakonda S.} } @article {47101, title = {Scalable and thin film approach for solar hydrogen generation: a review on enhanced photocatalytic water splitting}, journal = {Journal of Materials Chemistry A}, volume = {9}, year = {2021}, month = {JAN}, pages = {1353-1371}, type = {Review}, abstract = {

Although nearly five decades of efforts have gone into solar water splitting (SWS), still success eludes and there is no big breakthrough till date. While huge importance is given either individually or concurrently to the three fundamental steps, namely, light absorption, charge carrier separation and diffusion and charge utilization at redox sites, many aspects that are practically helpful to improve the efficiency are not widely discussed and practised. Nonetheless, by adopting a number of small, but significant changes, solar hydrogen production can be enhanced. The present review discusses such different approaches employed for photocatalytic water splitting reported in the literature. For example, an increase of up to two orders of magnitude in solar hydrogen generation was observed with a film form compared to the particulate form of the same catalyst. Discussion on various approaches of enhanced hydrogen production under sunlight and one sun conditions is the main focus of this review, in particular with thin-film forms. The merits and demerits of thin film and particulate methods, respectively, are addressed in detail. Potential methods and successful stories on scalability are also discussed in the present review. In contrast to charge collection over a long distance in solar cell-based methods, a film-based method discussed shows that the local charge utilisation at a zero applied potential is an attractive feature for SWS. A comparison is provided between the PEC-WS and SWS for solar hydrogen generation, and how far we are from the reality to produce solar hydrogen on an industrial scale. We believe the presently practised diverse evaluation efforts may be truncated to fewer methods such as film-based evaluation and in a focussed manner to tackle the SWS issue towards sustainable production of solar hydrogen.

}, issn = {2050-7488}, doi = {10.1039/d0ta09619a}, author = {Gopinath, Chinnakonda S. and Nalajala, Naresh} } @article {48213, title = {Concerted effect of Ni-in and S-out on ReS2 nanostructures towards high-efficiency oxygen evolution reaction}, journal = {Chemical Communications}, volume = {58}, year = {2022}, month = {MAR}, pages = {3689-3692}, type = {Article}, abstract = {

Herein, a one-step hydrothermal reaction is developed to synthesize a Ni-doped ReS2 nanostructure with sulphur defects. The material exhibited excellent OER activity with a current density of 10 mA cm(-2) at an overpotential of 270 mV, a low Tafel slope of 31 mV dec(-1), and good long-term durability of 10 h in 1 M KOH. It shows high faradaic efficiency of 96\%, benefiting from the rapid charge transfer caused by the concerted effect of Ni-in and S-out on the ReS2 nanostructure.

}, issn = {1359-7345}, doi = {10.1039/d1cc07030d}, author = {Das, Tapas K. and Ping, Tapan and Mohapatra, Manoj and Anwar, Shahid and Gopinath, Chinnakonda S. and Jena, Bikash Kumar} } @article {48359, title = {Electronic structure evolution from metallic vanadium to metallic VxOy: a nappes study for o2+v gas-solid interaction}, journal = {Journal of Physical Chemistry C}, volume = {126}, year = {2022}, month = {NOV}, pages = {19136-19146}, type = {Article}, abstract = {

Gas-solid interactions between molecular oxygen and metallic vanadium surfaces and the systematic evolution in the electronic structure of vanadium oxide (VOx) surfaces have been explored in the present work by near-ambient pressure photo-electron spectroscopy (NAPPES). The current article studies the evolution of various oxides of vanadium as a function of partial pressure of O2 (ultrahigh vacuum to 1 mbar), temperature (298- 875 K), and the exposure time to oxygen (up to 18 h). Valence -band (VB) and core-level spectral measurements recorded with UV (He-I = 21.2 eV) and Al K alpha (1486.6 eV) photons, respectively, show interesting changes. (1) Oxidation is limited to the top layers of vanadium at 298 K and up to a partial pressure of 1 mbar O2. About 50\% of vanadium gets oxidized, and the remaining amount exists as metal within the top 10 nm. (2) Metallic vanadium disappears above 625 K, and it is predominantly oxidized to a mixture of V4+ and V5+ oxidation states at a 0.1 mbar partial pressure of O2. Points 1 and 2 suggest the predominantly thermodynamically controlled nature of vanadium oxidation through oxygen diffusion into the subsurface and bulk layers. (3) The Fermi-level (EF) feature observed first at \>= 725 K at a 0.1 mbar O2 pressure demonstrates the formation of metallic VO2; however, its metallic nature is preserved even at ambient temperature due to interweaving nanodomains of VOx with VO2. (4) Only partial conversion of surface layers to V5+ (V2O5) along with VO2 and V2O3 (within the probing depth of 8-10 nm by near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS)) was observed even after prolonged heating (18 h) in 1 mbar O2 pressure. (5) The nature of the surface changes between metal and semiconducting/ insulator oxides is substantiated by the observation of changes in work function (phi) and EF features. Typical VB features and Fermi intensity of V-metal and vanadium oxides were observed, and the results were corroborated with core-level and VB spectra. The present results extend the capabilities of NAPPES to explore the electronic structure evolution as a function of reaction conditions and underscore its relevance to areas such as heterogeneous catalysis and sensing.

}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.2c05212}, author = {Ranjan, Ravi and Mhamane, Nitin B. and Kolekar, Sadhu K. and Gopinath, Chinnakonda S.} } @article {48225, title = {Enhanced hydrogen fuel production using synergistic combination of solar radiation and TiO2 photocatalyst coupled with Burkholderia cepacia lipase}, journal = {International Journal of Hydrogen Energy}, volume = {47}, year = {2022}, month = {APR }, pages = {14483-14492}, type = {Article}, abstract = {

Promising and sustainable alternatives for hydrogen production have been investigated. Among these, the use of enzymes may represent an efficient alternative. In this work, an increase in hydrogen production under simulated sunlight by combining TiO2 and TiO2/MgCl2 with Burkholderia cepacia lipase (BCL) was reported. The samples (TiO2, TiO2/MgCl2, and TiO2 /MgCl2/BCL) were characterized by X-ray diffraction (XRD), thermo-gravimetric (TGA), N-2 adsorption-desorption isotherms (BET), scanning electron microscopy (SEM), and UV-Visible absorption spectra. Hydrogen production tests were performed in aqueous methanol solutions under simulated sunlight. The results demonstrated that 130-times greater increase in hydrogen production rate was observed by the addition of BCL than individual TiO2. This better hydrogen production rate can be attributed to the increase in the amount of reduction equivalent of the system due to the oxidation of protein peptides caused by TiO2. In conclusion, the results indicate that hydrogen production efficiency can be significantly improved when integrating TiO2/MgCl2 with BCL. (C) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

}, keywords = {hydrogen production, Lipase, Nano-conjugated enzymes, Photocatalyst, Solar radiation, Titanium dioxide}, issn = {0360-3199}, doi = {10.1016/j.ijhydene.2022.02.220}, author = {de Souza Brandao, Luma Mirely and Barbosa, Milson dos Santos and de Jesus, Roberta Anjos and Bharad, Pradnya Arunrao and Lima, Alvaro Silva and Faria Soares, Cleide Mara and Navarro Yerga, Rufino Manuel and Bilal, Muhammad and Romanholo Ferreira, Luiz Fernando and Iqbal, Hafiz M. N. and Gopinath, Chinnakonda S. and Figueiredo, Renan Tavares} } @article {48077, title = {Facile, sustainable and unassisted plain water oxidation on Au/Ce0.9Ti0.1O2 nanorods in direct sunlight}, journal = {Journal of Chemical Sciences}, volume = {134}, year = {2022}, month = {JUN}, pages = {61}, type = {Article}, abstract = {

Impressive rate of solar water oxidation to molecular oxygen (O-2) has been demonstrated on nanorods (NRs) of Ce0.9Ti0.1O2 (CT-NR) and Au-deposited CT-NR (Au-CT-NR) photocatalysts with a sacrificial agent (Fe3+) and in plain water in one sun condition, direct sunlight and with lambda \>= 455 nm. Probably the highest 0 2 yield of 11 mmol/h.g was observed with Au-CT-NR thin film in plain water in direct sunlight, with no sacrificial agent or applied potential. Photoelectrochemical measurements demonstrate a marked reduction in oxidation onset potential of Au-CT-NR by 150 mV with stable photocurrent (0.75 mA/cm(2)), compared to CT-NR (0.23 mA/cm(2)), indicating the operative of plasmon-induced resonant energy transfer (PIRET) process. Effective electron quenching by nanogold and hence low recombination in the depletion region is a critical step for the observation of a high rate of oxygen evolution. In addition to this, a predominant change in the nature of the valence band from O-2p dominated on CeO2 to Ce-4f dominated with CT-NR (due to Ti4+ introduction in CeO2), the efficient light absorption of photocatalysts in thin-film form, functional and effective PIRET process, and facile E-F alignment, enhances the oxygen evolution with Au-CT-NR in direct sunlight and make it highly sustainable. A possible mechanism of water oxidation is proposed from the observed experimental findings.

}, keywords = {ceria, Electronic integration, Photocatalysis, thin film, water splitting}, issn = {0974-3626}, doi = {10.1007/s12039-022-02055-z}, author = {Dubey, Anjani and Mishra, Abhaya Kumar and Negi, Sanjay Singh and Gopinath, Chinnakonda S.} } @article {48345, title = {Possible fine-tuning of methane activation toward C2 oxygenates by 3d-transition metal-ions doped nano-ceria-zirconia}, journal = {Inorganic Chemistry}, volume = {61}, year = {2022}, month = {DEC }, pages = {19577-19587}, type = {Article}, abstract = {

In this work, we demonstrate a simple sol-gel technique to prepare metal-ion(s)-doped ceria-zirconia solid solution for efficient catalytic methane activation. The cation -depicting formula units are Ce0.80Zr0.20 (CZ), Ce0.79Zr0.20M0.01 (CZM), and Ce0.79Zr0.20M0.005M10.005 (CZMM1) (M and M1 = V, Mn, Fe, Co, and Cu), employed for undoped, mono-metal-ion -doped, and bi-metal-ion-doped solid solutions, respectively. Methane activation with Mn, Fe, Cu mono-metal-ion-doped CZ favors the C1 product, while CZCo assists C-C coupling with the formation of acetaldehyde. On the other hand, the Co-and Fe -doped bi-metal-ion combination catalyst (CZCoFe) shows significant ethanol but predominant formic acid formation. This is further promoted by the Co + V bi-metal-ion combination (CZCoV) catalyst, and it shows ethanol as the major product along with methyl hydrogen peroxide, methanol, and formic acid as minor products. An impressive ethanol yield of 93 mu mol/g h with 76\% selectivity obtained with the CZCoV catalyst is at par with that obtained with noble-metal-based catalysts under comparable reaction conditions. When Co and V content was increased two and four times from 0.005 to 0.01 and 0.02, ethanol yield increased at the expense of formic acid. The 213 mu mol/g h ethanol yield (86\% selectivity) observed with Ce0.76Zr0.20Co0.02V0.02 is probably the highest observed. The partial oxidation of CH4 in Co-based bi-metal combinations (Co + V or Co + Fe) suggests the synergistic effect of doped metal ions owing to the heterogeneous near -neighbor environment. The present results are attributed to the surface heterogeneity between the host and the dopants, which selectively promotes methane activation as well as C-C coupling. This indicates a large scope to tune the activity of partial oxidation of methane and product selectivity with different metal-ion(s) combinations.

}, issn = {0020-1669}, doi = {10.1021/acs.inorgchem.2c03493}, author = {Kanungo, Subhashree S. and Mishra, Abhaya Kumar and Mhamane, Nitin B. and Marelli, Udaya Kiran and Kumar, Dharmesh and Gopinath, Chinnakonda S.} } @article {48380, title = {Sulfur functionalization via epoxide ring opening on a reduced graphene oxide surface to form metal (II) Organo-bis-[1,2]-oxathiin}, journal = {Inorganic Chemistry}, volume = {61}, year = {2022}, month = {JAN}, pages = {279-286}, type = {Article}, abstract = {

The epoxide ring-opening reaction in graphene oxide (GO) by nucleophiles is a very fascinating and advanced methodology to develop novel functional material. Herewith, we report an advanced strategy for opening the epoxide ring on the rGO surface via easily an available nucleophile (Na2S), which is further functionalized with O atom to obtain four-membered rings (FMRs). The Cd coordination with the S atom puts extra stress on the FMR leading to the C-C bond cleavage of the four-membered heteroatomic rings on the rGO surface. This strategic approach leads to the fabrication of an innovative metal organo-bis-[1,2]-oxathiin (MOBOT) chemical moiety (M = Cd, Zn). The MOBOT compound further shows enhanced H-2 generation activity and hence is promising as a potential photocatalyst for solar hydrogen generation. This compound might also be a potential candidate for optoelectronic applications.

}, issn = {0020-1669}, doi = {10.1021/acs.inorgchem.1c02819}, author = {Kumar, Praveen and Bajpai, Himanshu and Gopinath, Chinnakonda S. and Luwang, Meitram Niraj} } @article {48000, title = {Sustainable CO2 reduction on in (2)O(3 )with exclusive CO selectivity: catalysis and in situ valence band photoelectron spectral investigations}, journal = {ACS Sustainable Chemistry \& Engineering}, volume = {10}, year = {2022}, month = {MAR}, pages = {3521-3531}, type = {Article}, abstract = {

This study demonstrates a sustainable catalytic CO2 conversion to near 100\% CO selectivity at ambient pressure on In2O3. Critically, high CO yield could be observed at the cost of undesired methanation, using a lower than stoichiometric amount of hydrogen in the feed; 1:1 and 1:0.67 CO2:H-2 ratios exhibit 98-99.6\% CO selectivity with 25-38\% CO2 conversion between 773 and 873 K. CO2 and H-2 conversion under steady-state conditions at 773-873 K suggests a 1:1 ratio of adsorbed reactants (with 1:0.67 CO2:H-2 feed) on the catalyst surface, underscoring the presence of an ideal reactant composition for the reverse water-gas shift reaction, while H-2-rich feed compositions show the H-2-dominated surface. Surface electronic structure changes, under near-operating conditions, were explored with near ambient pressure photoelectron spectroscopy (NAPPES), and the interesting findings are as follows: (a) A shift in the valence band to lower binding energy, up to 0.6 eV, was observed because of electron filling at high temperatures. (b) An observation of heterogeneous nature of the catalyst surface under NAPPES measurement conditions is attributed to the generation of active oxygen vacancy (O-v) sites, which in turn changes the work function of In2O3. (c) The above changes are found to be reversible, when the reaction was stopped. Vibrational features of the reactant molecules were observed to be broadened in the active temperature window of the catalyst supporting the heterogeneous character of the catalyst surface because of dynamic O-v generation. By optimizing gas hourly space velocity, CO2:H-2 ratio, and reaction temperature, exclusive CO selectivity is possible with a H-2:CO2 ratio of similar to 0.67, which will avoid the product separation stage altogether, while minimizing the expensive H-2 in the reactant feed.

}, keywords = {heterogeneous catalysis, Oxygen vacancy, photoelectron spectroscopy, RWGS, Work function}, issn = {2168-0485}, doi = {10.1021/acssuschemeng.1c07897}, author = {Mhamane, Nitin B. and Chetry, Sibo and Ranjan, Ravi and Raja, Thirumalaiswamy and Gopinath, Chinnakonda S.} } @article {48704, title = {Baby step in assembling and integrating the components of an artificial photosynthesis device with forced heterojunctions towards improved efficiency}, journal = {Journal of Materials Chemistry A}, volume = {11}, year = {2023}, month = {JUL }, pages = {15168-15182}, type = {Article}, abstract = {

How to achieve unassisted, economical, scalable, and sustainable artificial photosynthesis for liquid fuels/products with improved solar-to-fuel efficiency (STFE) to address a carbon-neutral economy remains a big question. To a large degree, the extent of charge separation at heterojunction interfaces and charge utilization determine the STFE. Towards this, BiVO3 is assembled from ionic-precursors into TiO2 pores, and integrated structurally and electronically with TiO2 on calcination as BiVO4 quantum dots (BVQDs). BVQDs in TiO2 (BVT) pores lead to an all-inorganic system with a sub-quadrillion number of heterojunctions in a 1 cm(2) device (contains similar to 25 mu g of BiVO4 (similar to 2.5 wt\%) in the nanopores of similar to 975 mu g of TiO2 (similar to 97.5 wt\%)) and facilitate artificial photosynthesis. We demonstrate 31-38\% STFE with a photon to chemical conversion turn over frequency (ToF(P2C)) of 2.73 s(-1) with a 1 cm(2) wireless BiVO4-TiO2 artificial leaf (BVT-AL) device for HCHO and CH3OH. The sequential nature of CO2 reduction to HCHO and then to CH3OH is evident from the reaction results. (CO2)-C-13 isotopic labeling experiments confirm that the input CO2 is the source for product formation. A large increase in the photocurrent density and incident photon-to-current efficiency (IPCE) of BVT, over 100\% for the BiVO4 photoanode in visible light, demonstrates and supports efficient visible light absorption, charge separation and migration to the redox sites. A device has been demonstrated to show sustainable activity in direct sunlight, and addresses scalability from 1 to 9 cm(2). Assuming no change (50\% decrease) in the STFE, a 6.74 m(2) device is expected to convert 1 (0.5) kg h(-1) CO2 into C1-oxygenates in sunlight. DFT calculations carried out with anatase TiO2 (101) and BiVO4 (121) interfaces support many of the experimental findings, including electron flow from the latter to the former, and interaction of the oxygen of TiO2 with BiVO4 and vice versa at the interface towards forced heterojunctions.

}, issn = {2050-7488}, doi = {10.1039/d3ta01850d}, author = {Salgaonkar, Kranti N. and Bajpai, Himanshu and Mhamane, Nitin B. and Nalajala, Naresh and Chauhan, Inderjeet and Thakkar, Kavita and Joshi, Kavita and Gopinath, Chinnakonda S.} } @article {48459, title = {CO2 electrolysis towards large scale operation: rational catalyst and electrolyte design for efficient flow-cell}, journal = {Chemical Communications}, volume = {59}, year = {2023}, month = {JUN}, pages = {6774-6795}, type = {Article}, abstract = {

The electrochemical CO2 reduction reaction (CO2RR) to renewable fuels/chemicals is a potential approach towards addressing the carbon neutral economy. To date, a comprehensive analysis of key performance indicators, such as an intrinsic property of catalyst, reaction environment and technological advancement in the flow cell, is limited. In this study, we discuss how the design of catalyst material, electrolyte and engineering gas diffusion electrode (GDE) could affect the CO2RR in a gas-fed flow cell. Significant emphasis is given to scale-up requirements, such as promising catalysts with a partial current density of \>= 100 mA cm(-2) and high faradaic efficiency. Additional experimental hurdles and their potential solutions, as well as the best available protocols for data acquisition for catalyst activity evaluation, are listed. We believe this manuscript provides some insights into the making of catalysts and electrolytes in a rational manner along with the engineering of GDEs towards CO2RR.

}, issn = {1359-7345}, doi = {10.1039/d3cc01231j}, author = {Patra, Kshirodra Kumar and Gopinath, Chinnakonda S.} } @article {48696, title = {Co3O4 for sustainable CO2 reduction and possible fine-tuning towards selective CO production}, journal = {Chemical Engineering Journal}, volume = {471}, year = {2023}, month = {SEP}, pages = {144459}, type = {Article}, abstract = {

Two main challenges involved in heterogeneous catalytic CO2 reduction are: (a) decreasing the consumption of H2 to the minimum required level with possibly the maximum CO2 conversion, and (b) concurrently enhancing the selectivity of the desired CO, at the cost of methane. Towards meeting these two challenges, Co3O4 spinel has been identified as a potential catalyst and it exhibits predominant CO selectivity \> 673 K at atmospheric pressure. CO2 conversion begins \> 523 K, with 100\% CO selectivity observed \> 673 K with CO2:H2 = 3:2. Current work shows a sustainable catalytic CO2 conversion to 100\% CO selectivity with Co3O4-Nanocube (NC). Critically, CO selectivity and yield is observed to increase at the cost of methane with smaller amount of H2. 1:1 and 3:2 CO2:H2 ratio exhibits 88-100\% CO selectivity with 24-32.5\% CO2 conversion between 623 and 823 K. Irrespective of the input CO2:H2, ratio of CO2:H2 uptake changes from around 1:3 at 523 K to 1:1-1.5 at 823 K with concurrent production of significant methane to predominant CO, respectively. Surface electronic state changes was explored by near ambient pressure photoelectron spectroscopy, and the results suggests that Co3O4 is the active phase that promotes CO2 reduction selectively to CO. Broadening observed with the vibrational feature of the CO2 molecules at high temperature underscores the heterogeneous character of the catalyst surface, under operating conditions, due to changing electron density. By optimizing the gas hourly space velocity (GHSV), H2-lean CO2:H2 ratio, and the reaction temperature/pressure, 100\% CO selectivity could be broadened to a range of operating conditions.

}, keywords = {Carbon neutral economy, heterogeneous catalysis, RWGS, SDG, Surface Science}, issn = {1385-8947}, doi = {10.1016/j.cej.2023.144459}, author = {Ranjan, Ravi and Tekawadia, Jyoti and Jain, Ruchi and Mhamane, Nitin B. and Raja, Thirumalaiswamy and Gopinath, Chinnakonda S.} } @article {48980, title = {Facile one-pot synthesis of Cu x O/TiO2 photocatalysts by regulating Cu oxidation state for efficient solar H2 production}, journal = {ACS Applied Energy Materials }, volume = {7}, year = {2023}, month = {DEC }, pages = {104-116}, type = {Article}, abstract = {

Development of highly efficient CuxO/TiO2 photocatalysts by regulating the oxidation state of Cu exclusively in either single or mixed oxidation state(s) is desirable but difficult to achieve without employing any external reagents. The present work describes a one-pot synthesis strategy to obtain CuxO/TiO2 photocatalysts with Cu in +1 and/or +2 by using a suitable combination of ethylene diamine tetra acetic acid (EDTA) and ethylene diamine, carefully varying the Cu content, and heat treatment process. CuxO/TiO2 nanocomposite catalysts were characterized thoroughly by physicochemical methods. Textural analysis indicates a high dispersion of CuxO on porous TiO2 with p-n heterojunctions between them in CuxO/TiO2 catalysts. UV-visible spectral analysis suggests the presence of CuxO on TiO2 with significantly extended absorption from the UV to the visible region. X-ray photoelectron spectroscopy (XPS) analysis indicates a strong synergetic interaction between TiO2 and CuxO due to the comparable CB potential and p-n heterojunction at the interface among them. Photoelectrochemical studies demonstrate excellent charge-carrier separation efficiency, low charge-transfer resistance, and high double-layer capacitance with Cu2O/TiO2 photocatalysts. Photocatalytic efficacy of a CuxO/TiO2 nanocomposite in thin-film form has been demonstrated for solar hydrogen generation in sunlight. The incorporation of Cu+ in TiO2 largely improves the H-2 production, and all of the CuxO/TiO2 nanocomposites in thin-film form exhibited higher efficiency compared to their particulate/suspension counterpart. Among the composite catalysts, TiCu-1 in thin-film form, with Cu exclusively in +1 oxidation state, exhibited a high hydrogen production rate of 7.06 mmol/hg, which is 6 times higher than its suspension counterpart; also catalysts containing mixed Cu-oxidation states exhibited about 60-70\% activity as that of TiCu-1. The superior performance of Cu2O/TiO2 nanocomposites in thin-film form was due to their enhanced light harvesting ability, high mass transfer rate, and easy accessibility of the reactant species to the active sites.

}, keywords = {heterojunction, Photocatalysis, Solar hydrogen, thin film, titania}, issn = {2574-0962}, doi = {10.1021/acsaem.3c02272}, author = {Rajendran, Sivaraj and Mani, Sunesh S. and Nivedhitha, Thazhath R. and Asoka, Anantha Krishnan and Arun, Pushkaran S. and Mathew, Thomas and Gopinath, Chinnakonda S.} } @article {48272, title = {Nanostructured Co-doped BiVO4 for efficient and sustainable photoelectrochemical chlorine evolution from simulated sea-water}, journal = {Dalton Transactions}, volume = {52}, year = {2023}, month = {FEB}, pages = {2051-2061}, type = {Article}, abstract = {

The co-production of hydrogen and chlorine from sea-water splitting could be a potential, sustainable and attractive route by any method. However, challenges to overcome are many, and critically, the sustainability and operating potential of the electrocatalyst are important. In this work, we report on Co-doping in the BiVO4 (Co-BV) crystal lattice and employed the same as the photoanode; Co-BV exhibits a photocurrent of 190 mu A cm(-2) at 1.1 V vs. RHE (the reversible hydrogen electrode) in the acidic sodium chloride solution (pH 2.3) under one sun illumination. The best-performing photoanode, with 0.05 mol\% of Co doping (0.05 Co-BV), selectively produced active chlorine with 92\% faradaic efficiency at 1.1 V vs. RHE by successfully suppressing the kinetically sluggish oxygen evolution reaction (OER) and the stability of the catalyst was demonstrated for up to 20 h. This is the lowest operating potential reported for the chlorine evolution reaction (CER), thus far. The overpotential required for CER with 0.05 Co-BV is lower than that of OER, which leads to selective CER at 1.1 V (vs. RHE). Co-doping into the BiVO4 lattice decreases the charge transfer resistance and enhances the CER kinetics due to its structural and electronic integration with the BV lattice. We demonstrate that Co-doping also improves the lifetime of the charge carrier and enhances the current density of CER and sustainability of the catalyst.

}, issn = {1477-9226}, doi = {10.1039/d2dt03369k}, author = {Chauhan, Inderjeet and Patra, Kshirodra Kumar and Bajpai, Himanshu and Mhamane, Nitin B. and Salgaonkar, Kranti N. and Gopinath, Chinnakonda S.} } @article {48469, title = {Photocatalytic setup for in situ and operando ambient-pressure X-ray photoelectron spectroscopy at MAX IV Laboratory}, journal = {Journal of Synchrotron Radiation}, volume = {30}, year = {2023}, month = {MAY}, pages = {613-619}, type = {Article}, abstract = {

The Ambient-Pressure X-ray Photoelectron Spectroscopy (APXPS) endstation at the SPECIES beamline at MAX IV Laboratory has been improved. The latest upgrades help in performing photo-assisted experiments under operando conditions in the mbar pressure range using gas and vapour mixtures whilst also reducing beam damage to the sample caused by X-ray irradiation. This article reports on endstation upgrades for APXPS and examples of scientific cases of in situ photocatalysis, photoreduction and photo-assisted atomic layer deposition (photo-ALD).

}, keywords = {APXPS, photo-ALD, Photocatalysis, solar simulator}, issn = {0909-0495}, doi = {10.1107/S1600577523002801}, author = {Klyushin, Alexander and Ghosalya, Manoj and Kokkonen, Esko and Eads, Calley and Jones, Rosemary and Nalajala, Naresh and Gopinath, Chinnakonda S. and Urpelainen, Samuli} } @article {48273, title = {Selective and generic photocatalytic oxidation of alcohol with Pd-TiO2 thin films: butanols to butanal/butanone with different morphologies of Pd and 0.5 theta(Pt)-Pd counterparts}, journal = {Chemistry-An Asian Journal}, volume = {18}, year = {2023}, month = {MAR}, type = {Article}, abstract = {

The present study reports on the photocatalytic oxidation of butanols to butanal/butanone using thin film form of facet-dependent nano-Pd supported on commercial TiO2 under one-sun condition and demonstrates the generic nature. Pd-nanocube (Pd-NC(100)), Pd-truncated octahedron (Pd-TO (100) and (111)), polycrystalline (Pd-PC), and their counterparts with half-a-monolayer Pt-coated on Pd (0.5 theta(Pt)-Pd)) have been used as co-catalyst. A potentially scalable thin film form of Pd/TiO2 photocatalyst, prepared by drop-casting method, has been employed to study oxidation of n-butanol, 2-butanol, and iso-butanol to corresponding aldehyde/ketone. 100\% selectivity is demonstrated to respective aldehyde/ketone with any catalyst used in the present study with varying degree of butanols conversion by NMR. 0.5 theta(Pt)-Pd-TO/TiO2 shows the highest conversion of 2-butanol to butanone (13.6\% in 4 h). Continuous 10 h of reaction with the most active 0.5 theta(Pt)-Pd-TO/P25 catalyst demonstrates 31\% conversion of 2-butanol to butanone, and catalyst recyclability has been demonstrated. The present protocol can be scalable to large scales to maximize the conversion in direct sunlight. Due to its generic nature, the current method can also be applied to many other alcohols and substrate molecules.

}, keywords = {energy conversion, Nanomaterials, Oxidation, Photocatalysis, Sustainability}, issn = {1861-4728}, doi = {10.1002/asia.202201239}, author = {Salgaonkar, Kranti N. and Kale, Sandip R. and Nalajala, Naresh and Mansuri, Sayana and Gopinath, Chinnakonda S.} } @article {49185, title = {Aqueous glycerol to glyceric acid and green hydrogen by visible-light-driven photocatalysis with Ni/Co(PO4)2-TiO2: parallel utilization of holes and electrons}, journal = {ACS Sustainable Chemistry \& Engineering}, volume = {12}, year = {2024}, month = {SEP}, pages = {14841-14853}, type = {Article}, abstract = {

Replacing the kinetically sluggish oxygen evolution reaction (OER) with the oxidation of an abundantly available organic molecule to value-added product(s) (VAPs) at low voltage along with the hydrogen evolution reaction (HER) is a big challenge in water splitting, either by electrolysis or sunlight-driven photocatalysis. Glycerol oxidation to a VAP is kinetically fast, compared to an OER, and offers hope to enhance sunlight-driven water splitting to hydrogen by the concurrent utilization of holes and electrons. Mixed bimetal phosphates of Co and Ni (CoxNiy(PO4)(2) (CoNiP)) with different Co:Ni ratios (10:0, 7:3, 5:5, 3:7, and 0:10) were integrated with TiO2 to generate final photocatalyst composites (x wt \% CoNiP with TiO2) and employed for concurrent photocatalytic HER and glycerol oxidation. Irrespective of the weight ratios of CoNiP and TiO2, any TiO2-CoNiP composite showed better photocatalytic activity for the HER and glycerol oxidation compared to virgin TiO2. The highest HER as well as selectively generated glyceric acid yield was observed to be 54 and 67 mmol/g, respectively, after 25 h of reaction under 1 sun conditions with TiO2-CoNiP-5:5. An increase in catalytic activity can be attributed to the formation of p-n heterojunctions of the constituent component along with uniform distribution of CoNiP to effectively utilize the charge carriers for redox reactions. Highly selective oxidation of glycerol to glyceric acid (85\%), along with other minor products, is also demonstrated, which offers further scope to use solar light to generate VAPs in a sustainable manner. A simple comparison of H-2 yield and all oxidized products together indicates the better utilization of holes for the latter, and hence, there is scope to increase HER and possibly the whole photocatalytic activity.

}, keywords = {biomass component, earth-abundantmaterial, energy conversion, organicvalorisation, water splitting}, issn = {2168-0485}, doi = {10.1021/acssuschemeng.4c05853}, author = {Nivedhitha, Thazhath R. and Bajpai, Himanshu and Oommen, Jiffin Varghese and Abraham, Athira and Chauhan, Inderjeet and Gopinath, Chinnakonda S.} } @article {49419, title = {Bimetallic and plasmonic Ag and Cu integrated TiO2 thin films for enhanced solar hydrogen production in direct sunlight}, journal = {Energy Advances}, volume = {3}, year = {2024}, month = {APR}, pages = {829-840}, type = {Article}, abstract = {
Plasmonic metal nanoparticle-integrated mesoporous TiO2\ nanocomposites (Ag/TiO2, Cu/TiO2\ and Ag{\textendash}Cu/TiO2), prepared by a simple chemical reduction method, have been demonstrated to show superior activity in thin-film form for solar H2\ generation in sunlight. Integration of Ag + Cu on TiO2\ significantly enhances the solar H2\ production due to the combined SPR effect of both metal species and the possible synergistic interaction among Cu + Ag in Ag{\textendash}Cu/TiO2. TiAgCu-1 (0.75 wt\% Ag and 0.25 wt\% Cu on TiO2) showed the highest H2\ yield of 6.67 mmol h-1\ g-1\ and it is 43 times higher than that of bare TiO2. The thin-film form of TiAgCu-1 shows 5 times higher solar H2\ production than its powder counterpart. 1 wt\% of Ag or Cu on TiO2\ shows a H2\ yield of 4.6 or 2 mmol h-1\ g-1, respectively, which underscores the importance of combined or synergistic effects. The increase in solar H2\ generation in Ag{\textendash}Cu/TiO2\ is attributed to factors such as the SPR effect of Cu and Ag, and strong interaction between Ag and Cu. The high photocatalytic efficiency of the TiAgCu-1 thin film is attributed to the large dispersion of metallic species with relatively high Ag/Cu surface atomic ratio, enhanced light absorption, a heterogeneous distribution of Ag and Cu species, and high double layer capacitance. The inter particle mesoporous network increases the interfacial charge transfer and reduces the mass transfer limitations. The plausible photocatalytic reaction mechanism could involve the combination of direct electron transfer from metal (Cu/Ag) to TiO2\ as well as the significant field effect due to the Ag{\textendash}Cu alloy, which is expected to increase the electron excitation locally.
Plasmonic metal nanoparticle integrated mesoporous TiO2\ nanocomposites (Ag/TiO2, Cu/TiO2\ and Ag{\textendash}Cu/TiO2), prepared by a simple chemical reduction method, have been demonstrated to show superior activity in thin-film form for solar H2\ generation.

}, doi = {https://doi.org/10.1039/d4ya00056k}, author = {Mani, Sunesh S. and Rajendran, Sivaraj and Arun, Pushkaran S. and Vijaykumar, Aparna and Mathew, Thomas and Gopinath, Chinnakonda S.} } @article {49202, title = {Design of Bi-functional mixed oxide electrodes for selective oxidative C-C cleavage of glycerol to formate and synchronized green hydrogen production}, journal = {Sustainable Energy \& Fuels}, volume = {8}, year = {2024}, month = {JUN }, pages = {2954-2968}, type = {Article}, abstract = {

Alkaline water electrolysis is a mature method to produce green hydrogen; however, it suffers from significantly high cost as high overpotentials are required for the oxygen evolution reaction (OER). However, the OER could be avoided altogether by replacing it with kinetically favorable oxidation of abundantly available feedstock molecules at a significantly low potential to value-added product(s) together with green hydrogen generation. This is a potential method to address the high cost of green hydrogen production while converting waste to wealth. Herein, we report green, template-free hydrothermal synthesis of an electrochemically active NiCoMn mixed oxide (NCMO) electrocatalyst with multiple sites, porous structure, large surface area, and nanoneedle (NN) morphology deposited directly over Ni foam (NF). Sustainable electrocatalytic performance was demonstrated for 120 h in 0.2 M alkaline glycerol using chronoamperometry and chronopotentiometry. Highly selective formate production demonstrated an exclusive C-C cleavage with the present catalyst system. Oxides of individual metal-ions (Ni, Co, and Mn) and their bimetallic combination (NiCo, NiMn, and CoMn) exhibited lower activity and product selectivity than the trimetallic NCMO electrocatalyst. The membrane-free two-electrode electrolyzer setup with NCMO/NF at both the anode and cathode (NCMO/NF \& Vert;NCMO/NF) requires 1.63 V to accomplish 100 mA cm-2 with 0.2 M glycerol, which is 296 mV less than that of 1 M KOH solution. High faradaic efficiency was observed for hydrogen (98\%) with highly selective formate (90\%) production. Electrocatalytic formate generation from an alkaline glycerol solution with NCMO is an energy-efficient and promising approach that also supplies carbon-negative green H2. NiCoMn oxide nanoneedles with a cactus-like morphology are shown as bifunctional electrocatalysts that selectively oxidize glycerol to HCOOH and concurrently produce H2.

}, issn = {2398-4902}, doi = {10.1039/d4se00434e}, author = {Saha, Arindam and Murugiah, Vasantharadevi and Ranjan, Ravi and Chauhan, Inderjeet and Patra, Kshirodra Kumar and Bajpai, Himanshu and Saha, Avisekh and Gopinath, Chinnakonda S.} } @article {49413, title = {Electrocatalytic and selective oxidation of glycerol to formate on 2D 3d-metal phosphate nanosheets and carbon-negative hydrogen generation}, journal = {ACS Materials Au}, volume = {4}, year = {2024}, month = {JUN}, pages = {500-511}, type = {Article}, abstract = {

In the landscape of green hydrogen production, alkaline water electrolysis is a well-established, yet not-so-cost-effective, technique due to the high overpotential requirement for the oxygen evolution reaction (OER). A low-voltage approach is proposed to overcome not only the OER challenge by favorably oxidizing abundant feedstock molecules with an earth-abundant catalyst but also to reduce the energy input required for hydrogen production. This alternative process not only generates carbon-negative green H2\ but also yields concurrent value-added products (VAPs), thereby maximizing economic advantages and transforming waste into valuable resources. The essence of this study lies in a novel electrocatalyst material. In the present study, unique and two-dimensional (2D) ultrathin nanosheet phosphates featuring first-row transition metals are synthesized by a one-step solvothermal method, and evaluated for the electrocatalytic glycerol oxidation reaction (GLYOR) in an alkaline medium and simultaneous H2\ production. Co3(PO4)2\ (CoP), Cu3(PO4)2\ (CuP), and Ni3(PO4)2\ (NiP) exhibit 2D sheet morphologies, while FePO4\ (FeP) displays an entirely different snowflake-like morphology. The 2D nanosheet morphology provides a large surface area and a high density of active sites. As a GLYOR catalyst, CoP ultrathin (\~{}5 nm) nanosheets exhibit remarkably low onset potential at 1.12 V (vs RHE), outperforming that of NiP, FeP, and CuP around 1.25 V (vs RHE). CoP displays 82\% selective formate production, indicating a superior capacity for C{\textendash}C cleavage and concurrent oxidation; this property could be utilized to valorize larger molecules. CoP also exhibits highly sustainable electrochemical stability for a continuous 200 h GLYOR operation, yielding 6.5 L of H2\ production with a 4 cm2\ electrode and 98 {\textpm} 0.5\% Faradaic efficiency. The present study advances our understanding of efficient GLYOR catalysts and underscores the potential of sustainable and economically viable green hydrogen production methodologies.

}, doi = {https://doi.org/10.1021/acsmaterialsau.4c00024}, author = {Chauhan, Inderjeet and Vijay, Pothoppurathu M. and Ranjan, Ravi and Patra, Kshirodra Kumar and Gopinath, Chinnakonda S.} } @article {49079, title = {Electrocatalytic glycerol conversion: a low-voltage pathway to efficient carbon-negative green hydrogen and value-added chemical production}, journal = {ACS Applied Materials and Interfaces }, volume = {16}, year = {2024}, month = {MAY }, pages = {26130-26141}, type = {Article}, abstract = {

Electrochemical glycerol oxidation reaction (GLYOR) could be a promising way to use the abundantly available glycerol for production of value-added chemicals and fuels. Completely avoiding the oxygen evolution reaction (OER) with GLYOR is an evolving strategy to reduce the overall cell potential and generate value-added chemicals and fuels on both the anode and cathode. We demonstrate the morphology-controlled palladium nanocrystals, afforded by colloidal chemistry, and their established morphology-dependent GLYOR performance. Although it is known that controlling the morphology of an electrocatalyst can modulate the activity and selectivity of the products, still it is a relatively underexplored area for many reactions, including GLYOR. Among nanocube (Pd-NC), truncated octahedron (Pd-TO), spherical and polycrystalline (Pd-PC) morphologies, the Pd-NC electrocatalyst deposited on a Ni foam exhibits the highest glycerol conversion (85\%) along with 42\% glyceric acid selectivity at a low applied potential of 0.6 V (vs reversible hydrogen electrode (RHE)) in 0.1 M glycerol and 1 M KOH at ambient temperature. Owing to the much favorable thermodynamics of GLYOR on the Pd-NC surface, the assembled electrolyzer requires an electricity input of only similar to 3.7 kWh/m(3) of H-2 at a current density of 100 mA/cm(2), in contrast to the requirement of \>= 5 kWh/m(3) of H-2 with an alkaline/PEM electrolyzer. Sustainability has been successfully demonstrated at 10 and 50 mA/cm(2) and up to 120 h with GLYOR in water and simulated seawater.

}, keywords = {electrocatalysis, Glycerol, green hydrogen, nanocube, Palladium, SDG}, issn = {1944-8244}, doi = {10.1021/acsami.4c02392}, author = {Chauhan, Inderjeet and Bajpai, Himanshu and Ray, Bishakha and Kolekar, Sadhu K. and Datar, Suwarna and Patra, Kshirodra Kumar and Gopinath, Chinnakonda S.} } @article {49267, title = {The ex situ exsolved exsolved Ni-Ru alloy from nickel-ruthenium co-doped SrFeO perovskite as a potential catalyst for C=C and C=O hydrogenation}, journal = {SUSTAINABLE ENERGY \& FUELS}, volume = {8}, year = {2024}, month = {JUN }, type = {Journal Article}, keywords = {LIQUID-PHASE HYDROGENATION, OXIDE FUEL-CELLS}, issn = {2398-4902}, doi = {10.1039/d4se00170b}, author = {Bhavisha, Meloth and Balamurugan, Sarkarainadar and Gopinath, Chinnakonda S. and Sakthivel, Ayyamperumal} } @article {49240, title = {Exploring defect-engineered metal-organic frameworks with 1,2,4-triazolyl isophthalate and benzoate linkers}, journal = {INORGANIC CHEMISTRY}, volume = {63}, year = {2024}, month = {MAY }, pages = {10843-10853}, type = {Journal Article}, keywords = {Separation, spectroscopy, TRIAZOLYL}, issn = {0020-1669}, doi = {10.1021/acs.inorgchem.4c01589}, author = {Chetry, Sibo and Lukman, Muhammad Fernadi and Bon, Volodymyr and Warias, Rico and Fuhrmann, Daniel and Moellmer, Jens and Belder, Detlev and Gopinath, Chinnakonda S. and Kaskel, Stefan and Poeppl, Andreas and Krautscheid, Harald} } @article {49365, title = {Fuel-influenced nanorod-to-nanosphere transformation of vanadium-doped ZnO and its performance in dye-sensitized solar cells}, journal = {NEW JOURNAL OF CHEMISTRY}, volume = {48}, year = {2024}, month = {NOV }, pages = {19175-19187}, keywords = {Nanoparticles, Nanowires, Photoanode, Thin-films}, issn = {1144-0546}, doi = {10.1039/d4nj03589e}, author = {Kuppusamy, Sasikumar and Mohan, Theanmozhi and Gnana Kumar, G. and Gopinath, Chinnakonda S. and Saha, Arindam and Michael, Robin Jude Vimal} } @article {49323, title = {Oxidative and selective C-C cleavage of glycerol to glycolaldehyde with atom-like Cu on Cu-TiO2: photocatalytic water reduction with concurrent glycerol oxidation in sunlight}, journal = {Journal of Catalysis}, volume = {437}, year = {2024}, month = {SEP}, pages = {115644}, type = {Article}, abstract = {

Concurrent consumption of electrons and holes for the conversion of a biomass component to value added products represents a highly efficient and sustainable approach towards utilizing renewable energy, but difficult to achieve. The integration of hydrogen production with glycerol oxidation presents a novel and sustainable approach towards achieving a circular economy. In the current study, integration of atom-like Cu-clusters onto TiO2 substrate has been achieved using a facile photo-deposition technique (TC-PDO). Also, novel synthetic approaches have been employed to augment the surface coverage of Cu on TiO2 with atom-like clusters of Cu, either by borohydride treatment on TiO2 followed by Cu-deposition (TC-200) or oxygen-vacancy creation by UV illumination followed by Cu-deposition (TC-PDO). Increased dispersion and enhanced electronic integration of Cu with TiO2 lead to a corresponding increase in the efficiency of photocatalytic hydrogen evolution (13.8 mmol/h.g for TC-PDO at pH 9). Several atom-like Cu integrated with each TiO2 particle acts as photocatalytic reactor, and the same enhances electron-hole separation as well as activity. Sustainable aspect was also studied for TC-PDO up to 25 h at pH 9. Concurrently, glycerol oxidation displays the highest selectivity to C2 product (glycolaldehyde with 70 \%) with a C-C cleavage. The investigation of this process holds significant potential for the extensive and simultaneous exploitation of electrons and holes in order to achieve water splitting and glycerol oxidation towards selective value-added products formation.

}, keywords = {C -C Cleavage, Glycerol, nanotechnology, Photo -deposition, solar energy conversion}, issn = {0021-9517}, doi = {10.1016/j.jcat.2024.115644}, author = {Bajpai, Himanshu and Nivedhitha, Thazhath R. and Dais, Elsa and Kanungo, Subhashree S. and Gopinath, Chinnakonda S.} } @article {49535, title = {Efficient hydrogen liberation from autocatalytic wastewater treatment by green synthesized Ag2SeO3 nanocatalyst}, journal = {Inorganic Chemistry Communications}, volume = {175}, year = {2025}, month = {MAY}, pages = {114106}, type = {Article}, abstract = {

Concerns about wastewater management, secure hydrogen storage, and interest in an affordable, effective, and user-friendly technique for releasing hydrogen have grown globally. Developing sustainable synthetic processes that result in industrially significant nanocatalyst to synergistically accelerate the evolution of hydrogen from wastewater treatment is extremely desirable. This work, for the first time, demonstrates the design and green fabrication of bactericidal silver selenite nanoparticles (Ag2SeO3 NPs) using the fungus Aspergillus niger for autocatalytic hydrogen production and methylene blue dye reduction by hydrolytic dehydrogenation of NaBH4. The morphology of Ag2SeO3 nanocatalysts with an average particle size of 60 nm was assessed by FETEM, while their surface chemistry, crystal structure, and optical properties were examined using XPS, XRD, and FTIR/ UV-Visible spectrophotometers, respectively. The sigmoidal trajectory of NaBH4 dehydrogenation with turnover frequencies (TOF) of 4750 mL g- 1 min- 1 suggested good autocatalytic activity of Ag2SeO3 NPs. The mechanistic study unveiled that autocatalysis was made possible by the creation of novel, active Ag co-catalyst which works synergistically with Ag2SeO3 NPs. For in-situ, real time assessment of Ag concentration during catalysis, hydrolysis of NaBH4 was carried out in the presence of methylene blue dye. The results showed that the active cocatalyst centers have a significant influence on autocatalytic hydrogen production at room temperature, reducing 98.8 \% methylene blue (MB) dye in 6 min with a lesser hydrogen generation rate of 4174 mL g- 1 min- 1. The catalyst exhibited excellent stability and durability after fourth consecutive cycle, demonstrating its promise for long-term and recurring application in hydrogen liberation from autocatalytic MB dye reduction.

}, keywords = {Ag2SeO3 nanoparticles, Antibacterial, autocatalysis, Hydrogen generation, Wastewater treatment}, issn = {1387-7003}, doi = {10.1016/j.inoche.2025.114106}, author = {Islam, Sk Najrul and Ansari, Ifra Ilyas and Gopinath, Chinnakonda S. and Ahmad, Absar} } @article {49600, title = {Enhanced mid-visible light absorption and long-lived charge carriers in an electronically and structurally integrated BiVO4-TiO2 photoanode for efficient artificial photosynthesis applications}, journal = {Nanoscale}, volume = {17}, year = {2025}, month = {MAY}, pages = {12738-12750}, type = {Article}, abstract = {

The ever-increasing demand for sustainable solutions for eliminating environmental pollutants, solar energy harvesting, water splitting, etc. have led to the design and development of novel materials to achieve the desired result. In this regard, structurally and electronically integrated (SEI) BiVO4-TiO2 (SEI-BVT) with abundant heterojunctions has emerged as a promising entity for efficient charge separation, which in turn enhances artificial photosynthesis (APS) activity. The present work adopted a unique synthetic strategy using SILAR to fabricate SEI-BVT from ionic precursors (Bi3+ and VO43-) into the pores of TiO2, exhibiting benchmark APS efficiency compared to the individual components. This preparation results in approximately 180 trillion uniformly distributed heterojunctions in 1 mg cm-2 of the SEI-BVT photoanode material. Charge carriers in SEI-BVT and BiVO4 are similar; however, the recombination is highly hindered when SEI-BVT heterojunctions are formed in the former. Our earlier work demonstrated 31-38\% solar-to-fuel efficiency (STFE) with BiVO4-TiO2 for APS in the presence of the Pd-nanocube co-catalyst. The emphasis of the current work is to explore the dynamics of the light-induced processes in these heterojunctions to understand the interfacial charge transfer process. Femtosecond transient absorption (TA) spectroscopy has been employed to monitor the excited state dynamics. Our results show that new trap states have evolved under light illumination, which are significantly long-lived and hinder charge recombination, and consequently enhance STFE. A significantly large number of charge carriers exhibit a lifetime of \>\> 6 ns with visible light photons, at least up to 720 nm, which is higher than the band-gap absorption onset at 490 nm for SEI-BVT compared to bulk BiVO4. The rate of formation of charge carriers is significantly affected in the heterojunctions.

}, issn = {2040-3364}, doi = {10.1039/d5nr00723b}, author = {Jha, Vikas Kumar and Salgaonkar, Kranti N. and Saha, Avishek and Gopinath, Chinnakonda S. and Iyer, E. Siva Subramaniam} } @article {49621, title = {Multifunctional NiO/Ti3+-TiO2 for concurrent water reduction and glycerol oxidation to value added products by sunlight driven photocatalysis}, journal = {Journal of Materials Chemistry A}, volume = {13}, year = {2025}, month = {JAN}, pages = {2105-2120}, type = {Article}, abstract = {

The present work describes the synthesis of bifunctional-mesoporous-self-doped Ti3+ containing NiO/TiO2 photocatalysts for concurrent utilization of e- and h+ to produce H2 and value-added products (VAPs), respectively, from aqueous glycerol. UV-vis diffuse reflectance results and band gap analysis revealed an improved light absorption due to integration of Ni2+ with Ti3+/TiO2. Various electrochemical, PL and TRPL spectral analyses demonstrate p-n heterojunction formation between NiO and Ti3+-TiO2, which enhances charge separation and helps in achieving improved activity. HRTEM analysis of NiO/Ti3+-TiO2 nanocomposites revealed that NiO is highly dispersed on TiO2 with interfacial heterojunctions between them. XPS results demonstrate the partial reduction of Ti4+ to Ti3+ and Ni-Ti synergetic interaction in NiO/TiO2 to form NiO/Ti3+-TiO2 nanocomposites. EXAFS studies show that the Ni-O bond distance is similar to that of NiTiO3 suggesting electronic integration of components of the photocatalyst by forming a Ni2+-O-Ti3+/Ti4+ lattice network. Ni2+/Ti3+-TiO2 nanocomposites as a bifunctional photocatalyst exhibited significantly enhanced activity in H2 production and conversion of glycerol to VAPs, namely, glycolaldehyde, 1,3-dihydroxyacetone, and formic acid; formation of these products highlights not only oxidation, but also C-C cleavage of glycerol. The NiO/Ti3+-TiO2 photocatalysts fabricated in thin film form displayed higher photocatalytic efficiency than their powder counterpart. Among NiO/Ti3+-TiO2 nanocomposites NiT-3 exhibits the highest H2 yield at 15.62 mmol h-1 g-1, which is 38 times higher than that of bare TiO2. The enhanced photocatalytic activity is ascribed to the high charge carrier density, the synergistic interaction between Ni2+ and Ti3+-TiO2, formation of a p-n heterojunction at the interface between NiO and Ti3+-TiO2 and effective utilization of charge carriers for redox reactions.

}, issn = {2050-7488}, doi = {10.1039/d4ta06910b}, author = {Rajendran, Sivaraj and Saju, Simi and Mani, Sunesh S. and Asoka, Anantha Krishnan and Saha, Arindam and Arun, Pushkaran S. and Ghosh, Biplab and Mathew, Thomas and Gopinath, Chinnakonda S.} } @article {49446, title = {Multifunctional NiO/Ti3+{\textendash}TiO2 for concurrent water reduction and glycerol oxidation to value added products by sunlight driven photocatalysis}, journal = {Journal of Materials Chemistry A}, volume = {13}, year = {2025}, month = {JAN}, pages = {2105-2120}, type = {Article}, abstract = {

The present work describes the synthesis of bifunctional-mesoporous-self-doped Ti3+\ containing NiO/TiO2\ photocatalysts for concurrent utilization of e-\ and h+\ to produce H2\ and value-added products (VAPs), respectively, from aqueous glycerol. UV-vis diffuse reflectance results and band gap analysis revealed an improved light absorption due to integration of Ni2+\ with Ti3+/TiO2. Various electrochemical, PL and TRPL spectral analyses demonstrate p{\textendash}n heterojunction formation between NiO and Ti3+{\textendash}TiO2, which enhances charge separation and helps in achieving improved activity. HRTEM analysis of NiO/Ti3+{\textendash}TiO2\ nanocomposites revealed that NiO is highly dispersed on TiO2\ with interfacial heterojunctions between them. XPS results demonstrate the partial reduction of Ti4+\ to Ti3+\ and Ni{\textendash}Ti synergetic interaction in NiO/TiO2\ to form NiO/Ti3+{\textendash}TiO2\ nanocomposites. EXAFS studies show that the Ni{\textendash}O bond distance is similar to that of NiTiO3\ suggesting electronic integration of components of the photocatalyst by forming a Ni2+{\textendash}O{\textendash}Ti3+/Ti4+\ lattice network. Ni2+/Ti3+{\textendash}TiO2\ nanocomposites as a bifunctional photocatalyst exhibited significantly enhanced activity in H2\ production and conversion of glycerol to VAPs, namely, glycolaldehyde, 1,3-dihydroxyacetone, and formic acid; formation of these products highlights not only oxidation, but also C{\textendash}C cleavage of glycerol. The NiO/Ti3+{\textendash}TiO2\ photocatalysts fabricated in thin film form displayed higher photocatalytic efficiency than their powder counterpart. Among NiO/Ti3+{\textendash}TiO2\ nanocomposites NiT-3 exhibits the highest H2\ yield at 15.62 mmol h-1\ g-1, which is 38 times higher than that of bare TiO2. The enhanced photocatalytic activity is ascribed to the high charge carrier density, the synergistic interaction between Ni2+\ and Ti3+{\textendash}TiO2, formation of a p{\textendash}n heterojunction at the interface between NiO and Ti3+{\textendash}TiO2\ and effective utilization of charge carriers for redox reactions.

}, doi = {https://doi.org/10.1039/D4TA06910B}, author = {Rajendran, Sivaraj and Saju, Simi and Mani, Sunesh S. and Asoka, Anantha Krishnan and Saha, Arindam and Arun, Pushkaran S. and Ghosh, Biplab and Mathew, Thomas and Gopinath, Chinnakonda S.} } @article {49554, title = {Multiphasic heterojunctions: a strategic approach to enhance the charge transfer dynamics of titania for superior solar photocatalytic hydrogen production}, journal = {International Journal of Hydrogen Energy}, volume = {113}, year = {2025}, month = {MAR}, pages = {133-146}, type = {Article}, abstract = {

Multiphasic titania has been prepared to study the role of multiple heterojunctions on the charge transfer dynamics and resultant photocatalytic hydrogen production. Through an acid regulated hydrothermal method, four materials with following phase compositions were prepared viz. single phase anatase and rutile, biphasic anatase-rutile and triphasic anatase-brookite-rutile. The phase compositions of the materials were confirmed through XRD and HRTEM studies. The biphasic and triphasic materials were found to be highly nanoparticulate in nature while forming numerous and diverse heterojunctions. In the triphasic material, various binary and ternary heterojunctions were observed. These heterojunctions performed in harmony to ensure efficient charge transport as shown by the low charge transfer resistance and high electron lifetime. This subsequently ensured a high reduction capability and photocurrent response. This all culminated into the triphasic material outperforming all other materials in solar photocatalytic hydrogen production. The H2 yield from the triphasic material was 81\% and 40\% higher than the pristine anatase and the biphasic material respectively. Additionally, by using the triphasic material in thin film form, a 4-fold increase in the hydrogen yield with a high apparent quantum efficiency of 8.2 \% was achieved over the particulate form. The superior charge transport and photocurrent response due to the greater varied heterojunction formation in the anatase-rutile-brookite material as opposed to that in the biphasic material led to this superior performance. Thus, multiple heterojunctions, in this case, a triphasic heterojunction of anatase, rutile and brookite phases opens up a new avenue of research for efficient green hydrogen production.

}, keywords = {Green hydrogen production, heterojunction, Photocatalysis, Photoelectrochemical analysis, thin film, titania}, issn = {0360-3199}, doi = {10.1016/j.ijhydene.2025.02.395}, author = {Ningthoukhongjam, Pujita and Gopinath, Chinnakonda S. and Nair, Ranjith G.} }