@article { ISI:000243251100006, title = {Conducting polymer based hybrid nano-composites for enhanced corrosion protective coatings}, journal = {Progress in Organic Coatings}, volume = {57}, number = {4}, year = {2006}, month = {DEC}, pages = {332-336}, publisher = {ELSEVIER SCIENCE SA}, type = {Article}, address = {PO BOX 564, 1001 LAUSANNE, SWITZERLAND}, abstract = {

Hybrid composite coatings containing zinc oxide (ZnO) and polyaniline (PANI) as nano-additives dispersions were prepared with poly(vinyl acetate) (PVAc) as the major matrix. The steel plates dip-coated with these formulations were tested for corrosion protection by immersion in saline water over long periods. The Tafel plots for the determination of open circuit potential (OCP) and corrosion current (I-corr) were recorded. The coatings containing both ZnO and PANI showed improved corrosion resistance as compared to the single component coating. The I-corr values of PVAc-ZnO-PANI are found to be two-order magnitude lower than that of PVAc and PVAc-ZnO coatings. The results are explained on the basis of enhancement in barrier properties due to nano-particulate additives in PVAc-ZnO-PANI film together with the redox behaviour of PANI and protective oxide layer formation near the substrate. (C) 2006 Elsevier B.V All rights reserved.

}, keywords = {Coatings, corrosion, nano-additives, polyaniline, ZnO}, issn = {0300-9440}, doi = {10.1016/j.porgcoat.2006.09.012}, author = {Patil, R. C. and Radhakrishnan, S.} } @article { ISI:000237748700007, title = {Photocatalytic degradation of organic contaminants in water by ZnO nanoparticles: revisited}, journal = {Applied Catalysis A-General}, volume = {304}, number = {1}, year = {2006}, month = {MAY}, pages = {55-61}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Nanoscale photocatalysts have attracted much attention due to their high surface area to volume ratios. This work investigates the photodegradation of organic contaminants using the fluorescence emission characteristics of ZnO nanoparticles (ZnO-nano) in aqueous solutions. This is accomplished by preparing nanocrystalline ZnO; the presence of organic contaminants in water is readily detected from the quenching of fluorescence observed from ZnO semiconductor films. Photolysis of ZnO thin films immersed into an aqueous system containing organic contaminants results in the degradation of the contaminants. A comprehensive study has been done involving several organic contaminants in water (like aliphatic and aromatic chloro compounds as well as some commonly used aromatic solvents) to check the suitability of ZnO-nano as an efficient photocatalyst. The ZnO nanoparticles not only serve as a better catalytic system compared to bulk ZnO and commercially available Degussa TiO2 in achieving degradation of the added contaminants, but unlike other semiconductor systems can also act as a non-specific sensor for the presence of these common contaminants in water. A total cleanup of a cocktail of contaminants in water was also achieved using the ZnO-nano. (c) 2006 Elsevier B.V. All rights reserved.

}, keywords = {Nanoparticles, organic contaminants and photocatalysis, Semiconductor, ZnO}, issn = {0926-860X}, doi = {10.1016/j.apcata.2006.02.020}, author = {Hariharan, C.} } @article { ISI:000244008300028, title = {Influence of surfactant on ZnO varistors}, journal = {Ceramics International}, volume = {33}, number = {2}, year = {2007}, month = {MAR}, pages = {289-291}, publisher = {ELSEVIER SCI LTD}, type = {Article}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND}, abstract = {

ZnO varistors with and without surfactant such as sodium dodecyl sulphate (SIDS) are prepared by nitrate-combustion process. The samples were identically heat treated and sintered at 1000 degrees C for 12 h to study the influence of the surfactant on the nonlinear electrical properties of polycrystalline ZnO. It is observed that the nonlinear coefficient decreases marginally (alpha = 35) for samples prepared with surfactant, whereas breakdown field (E-B = 130 V/mm) decreased significantly. The corresponding parameters for the samples synthesized without surfactant are alpha = 45 and E-B = 400 V/mm. Hence, this method can be used for the manufacture of varistors with low to moderate breakdown fields. (c) 2005 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

}, keywords = {Chemical synthesis, Semiconductors, X-ray methods, ZnO}, issn = {0272-8842}, doi = {10.1016/j.ceramint.2005.08.010}, author = {Dhage, S. R. and Navale, S. C. and Ravi, V.} } @article { ISI:000250178900006, title = {Low temperature synthesis and NOx sensing properties of nanostructured Al-doped ZnO}, journal = {Sensors and Actuators B-Chemical}, volume = {126}, number = {2}, year = {2007}, month = {OCT}, pages = {382-386}, publisher = {ELSEVIER SCIENCE SA}, type = {Article}, address = {PO BOX 564, 1001 LAUSANNE, SWITZERLAND}, abstract = {

Although ZnO is studied intensively as a sensing material, there are limited reports available on aluminum-doped ZnO (AZO) as a NO, sensor. This paper reports selective NO, sensing characteristics of M-doped ZnO synthesized in the form of porous pellets sintered at 350 degrees C. The salient feature of our experimental results is that our sensor can detect small concentrations of NO, at lower operating temperature. It is also observed that as compared to gases such as SOx HCl, LPG, H2S, H-2, ammonia, alcohol and acetone it selectively detects NOx due to Al-doping. The amount of Al in ZnO during synthesis is varied between 1 and 10 wt\%. Our sensor senses NO, concentration as low as 20ppm at 100 degrees C with a \%response of 11 and a \%response of 740 at 300 degrees C for 1 wt\% Al. Of all the compositions with Al-doping, I wt\% is found to give best results. Sensing experiments carried out at 350 C, however. do not show any significant improvement in the gas sensing properties. The phase contents and lattice parameters were determined by XRD and the average particle size was obtained using Scherrer formula. A probable mechanism for sensing NO, involving oxygen ion adsorption and desorption on the surface of sensor has been suggested. (C) 2007 Elsevier B.V. All rights reserved.

}, keywords = {aluminum doping, nanomaterial, NOx, Sensor, ZnO}, issn = {0925-4005}, doi = {10.1016/j.snb.2007.03.019}, author = {Navale, S. C. and Ravi, V. and Mulla, Imtiaz S. and Gosavi, S. W. and Kulkarni, S. K.} } @article { ISI:000256603500023, title = {Controlled synthesis of ZnO from nanospheres to micro-rods and its gas sensing studies}, journal = {Talanta}, volume = {75}, number = {5}, year = {2008}, month = {JUN}, pages = {1315-1319}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

1D ZnO rods are synthesized using less explored hydrazine method. Here we find, besides being combustible hydrazine can also be used as a structure-directing agent. The ratio of zinc nitrate (ZN) to hydrazine is found to control the morphology of ZnO. At lower concentration of ZN as compared with hydrazine the morphology of ZnO is found to be spherical. As we increase the hydrazine content the morphology changes from spherical (diameter similar to 100 nm) to the elongated structures including shapes like Y, T as well dumbbell (diameter similar to 40 nm and length similar to 150 nm). Interestingly for more than 50\% of hydrazine ZnO micro-rods are formed. Such rods are of diameter similar to 120 mn having length of about 1 mu m for ZN to hydrazine ratio of 1:9, isolated as well as bundle of rods are seen in scanning electron microscopy (SEM). The X-ray diffraction (XRD) reveals the phase formation with average particle size of 37 nm as calculated using Scherrer{\textquoteright}s formula. The high-resolution transmission electron microscopy (HRTEM) is also done to confirm the d-spacing in ZnO. Gas sensing study for these samples shows high efficiency and selectivity towards LPG at all operating temperatures. Photoluminescence (PL) study for these samples is performed at room temperature to find potential application as photoelectric material. (C) 2008 Elsevier B.V. All rights reserved.

}, keywords = {Hydrazine, LPG sensor, Nanostructures, photoluminescence, ZnO}, issn = {0039-9140}, doi = {10.1016/j.talanta.2008.01.063}, author = {Navale, Shalaka C. and Gosavi, S. W. and Mulla, Imtiaz S.} } @article { ISI:000255107700017, title = {EPR and DRS evidence for NO2 sensing in Al-doped ZnO}, journal = {Sensors and Actuators B-Chemical}, volume = {130}, number = {2}, year = {2008}, month = {MAR}, pages = {668-673}, publisher = {ELSEVIER SCIENCE SA}, type = {Article}, address = {PO BOX 564, 1001 LAUSANNE, SWITZERLAND}, abstract = {

Zinc oxide (ZnO) is a well-known semiconducting multifunctional material wherein properties right from the morphology to gas sensitivity can be tailor-made by doping or surface modification. Aluminum (Al)-incorporated porous zinc oxide (AI:ZnO) exhibits good response towards NO2 at low-operating temperature. The NO2 gas concentration as low as 20 ppm exhibits S = 17\% for 5 wt. \% Al-incorporated ZnO. The NO2 response increases with operating temperature and concentration and reaches to its maximum at 300 degrees C without any interference from other gases such as SO3, HCl, LPG and alcohol. Physico-chemical characterization likes differential thermogravimetric analysis (TG-DTA) electron paramagnetic resonance (EPR) and diffused reflectance spectroscopy (DRS) have been used to understand the sensing behavior for pure and A]-incorporated ZnO. The TG-DTA depicts formation of ZnO phase at 287 degrees C. The EPR study reveals distinct variation for O- (g=2.003) and Zn interstitial (g = 1.98) defect sites in pure and Al:ZnO. The DRS studies elucidate signature of adsorbed NO, species in aluminium-incorporated zinc oxide indicating its tendency to adsorb these species even at low temperatures. This paper is an attempt to correlate the gas sensing behavior with the physico-chemical studies such as EPR and DRS. (c) 2007 Published by Elsevier B.V.

}, keywords = {aluminum doping, DRS, EPR, NO2 sensor, ZnO}, issn = {0925-4005}, doi = {10.1016/j.snb.2007.10.055}, author = {Navale, Shalaka C. and Ravi, V. and Srinivas, D. and Mulla, Imtiaz S. and Gosavi, S. W. and Kulkarni, S. K.} } @article { ISI:000271238900027, title = {Field emission properties of Al-doped ZnO nanostructures}, journal = {Journal of Nano Research}, volume = {5}, year = {2009}, month = {JAN}, pages = {231-237}, publisher = {TRANS TECH PUBLICATIONS LTD}, address = {LAUBISRUTISTR 24, STAFA-ZUERICH, CH-8712, SWITZERLAND}, abstract = {

Field emission from Al-doped ZnO nanostrcutures has been investigated in planar diode configuration under ultra high vacuum conditions. The Al-doped ZnO nanostructures were synthesized by co-precipitation method with varying aluminium concentrations. The as- synthesized product was characterized by x-ray diffraction, scanning electron microscope and energy dispersive x-ray analysis. The threshold field required to draw a current density of similar to 1 mu A/cm(2) was observed to be similar to 2.0 V/mu m and similar to 2.3 V/mu m for Al-doped ZnO nanostructures synthesized with aluminium concentrations of 1\% and 3\%, respectively. The Fowler- Nordheim (F-N) plots for both the specimens exhibit non-linear behaviour, which is observed to be specimen dependent. The nonlinearity observed in the F-N plots has been interpreted on the basis of the theory of electron emission from semiconductor emitters. The field enhancement factors, estimated from the slope of the F-N plots, are found to be similar to 9.3 x 10(3) and 3.9 x 10(3) for 1\% and 3\% Al-doped ZnO emitters, respectively. The high values of the field enhancement factor Suggest that the emission is from the nanostructures. The emission current stability measured at the preset value of similar to 2 mu A over a period of more than three hours is found to be fairly stable. The results indicate use of Al-doped ZnO nanostructures as promising emitters for field emission based devices.

}, keywords = {field emission, Fowler-Nordheim plots, Nanostructures, ZnO}, issn = {1662-5250}, author = {Navale, Shalaka C. and Sheini, Farid Jamali and Patil, Sandip S. and Mulla, Imtiaz S. and Joag, Dilip S. and More, Mahendra A. and Gosavi, Suresh W.} } @article { ISI:000283453700016, title = {Fowler-nordheim plot behavior and mechanism of field electron emission from ZnO tetrapod structures }, journal = {ACS Nano}, volume = {4}, number = {10}, year = {2010}, month = {OCT}, pages = {5585-5590}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Field emission measurements of current-voltage characteristics are reported for tetrapod structures of ZnO. The nonlinear Fowler-Nordheim (FN) plot is analyzed according to a model of calculation based on saturation of conduction band current and predominance of valence band current at high-field values. The simulated FN plot exhibits similar features to those observed experimentally. The model of calculation suggests that the slope variation of the FN plot, in the high-field and low-field regions, does not depend on the magnitude of saturation. Instead, it is a characteristic of the energy band structure and voltage-to-barrier-field conversion factor of the emitting material.

}, keywords = {field emission, Fowler-Nordheim plot, Nanostructures, nonlinearity, ZnO}, issn = {1936-0851}, doi = {10.1021/nn1008403}, author = {Al-Tabbakh, Ahmed A. and More, Mahendra A. and Joag, Dilip S. and Mulla, Imtiaz S. and Pillai, Vijayamohanan K.} } @article { ISI:000287268900024, title = {Room temperature ferromagnetism in undoped and Fe doped ZnO nanorods: microwave-assisted synthesis}, journal = {Journal of Solid State Chemistry}, volume = {184}, number = {2}, year = {2011}, month = {FEB}, pages = {391-400}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

One-dimensional (1D) undoped and Fe doped ZnO nanorods of average length similar to 1 mu m and diameter similar to 50 nm have been obtained using a microwave-assisted synthesis. The magnetization (M) and coercivity (H-c) value obtained for undoped ZnO nanorods at room temperature is similar to 5 X 10(-3) emu/g and similar to 150 Oe, respectively. The Fe doped ZnO samples show significant changes in M -H loop with increasing doping concentration. Both undoped and Fe doped ZnO nanorods exhibit a Curie transition temperature (T-c) above 390 K. Electron spin resonance and Mossbauer spectra indicate the presence of ferric ions. The origin of ferromagnetism in undoped ZnO nanorods is attributed to localized electron spin moments resulting from surface defects/vacancies, where as in Fe doped samples is explained by F center exchange mechanism. (C) 2010 Published by Elsevier Inc.

}, keywords = {Diluted magnetic semiconductors, Nanostructures, ZnO}, issn = {0022-4596}, doi = {10.1016/j.jssc.2010.11.008}, author = {Limaye, Mukta V. and Singh, Shashi B. and Das, Raja and Poddar, Pankaj and Kulkarni, Sulabha K.} } @article { ISI:000291725100012, title = {Synthesis of Cu-ZnO and C-ZnO nanoneedle arrays on zinc foil by low temperature oxidation route: effect of buffer layers on growth, optical and field emission properties}, journal = {Applied Surface Science}, volume = {257}, number = {20}, year = {2011}, month = {AUG}, pages = {8366-8372}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Different densities of ZnO nanoneedle films have been prepared by pre-coated zinc foils with thin layer of copper and carbon followed by thermal oxidation at 400 degrees C in air. The X-ray diffraction patterns show well defined peaks, which could be indexed to the wurtzite hexagonal phase of ZnO. The scanning electron microscope images clearly reveal formation of ZnO needles on the entire substrate surface. The X-ray photoelectron spectroscopy studies indicate that Cu and C ions are incorporated into the ZnO lattice. Photoluminescence studies evaluate different emission bands originated from different defect mechanism. From the field emission studies, the threshold field, required to draw emission current density of similar to 100 mu A/cm(2), is observed to be 2.25 V/mu m and 1.57 V/mu m for annealed zinc foil pre-coated with copper and carbon, respectively. The annealed film with copper layer exhibits good emission current stability at the pre-set value of similar to 100 mu A over a duration of 4 h. The results show that buffer layer is an important factor to control the growth rate, resulting in different density of ZnO needles, which leads to field emission properties. This method may have potential in fabrication of electron sources for high current density applications. (C) 2011 Elsevier B. V. All rights reserved.

}, keywords = {Buffer layer, Carbon, Copper, field emission, Nanoneedle, ZnO}, issn = {0169-4332}, doi = {10.1016/j.apsusc.2011.04.023}, author = {Jamali-Sheini, Farid and Patil, K. R. and Joag, Dilip S. and More, Mahendra A.} } @article { ISI:000315751600033, title = {Probing interaction of Gram-positive and Gram-negative bacterial cells with ZnO nanorods}, journal = {Materials Science \& Engineering C-Materials for Biological Applications}, volume = {33}, number = {3}, year = {2013}, month = {APR}, pages = {1247-1253}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

In the present work, the physiological effects of the ZnO nanorods on the Gram positive (Staphylococcus aureus and Bacillus subtilis) and Gram-negative (Escherichia coli and Aerobacter aerogenes) bacterial cells have been studied. The analysis of bacterial growth curves for various concentrations of ZnO nanorods indicates that Gram positive and Gram negative bacterial cells show inhibition at concentrations of similar to 64 and similar to 256 mu g/mL respectively. The marked difference in susceptibility towards nanorods was also validated by spread plate and disk diffusion methods. In addition, the scanning electron micrographs show a clear damage to the cells via changed morphology of the cells from rod to coccoid etc. The confocal optical microscopy images of these cells also demonstrate the reduction in live cell count in the presence of ZnO nanorods. These, results clearly indicate that the antibacterial activity of ZnO nanorods is higher towards Gram positive bacterium than Gram negative bacterium which indicates that the structure of the cell wall might play a major role in the interaction with nanostructured materials and shows high sensitivity to the particle concentration. (C) 2012 Elsevier B.V. All rights reserved.

}, keywords = {Confocal, Growth curve, Nanorods, SEM, Zeta potential, ZnO}, issn = {0928-4931}, doi = {10.1016/j.msec.2012.12.019}, author = {Jain, Aanchal and Bhargava, Richa and Poddar, Pankaj} } @article { ISI:000334476100013, title = {Comparative study on the dye sensitized solar cell performance of solution processed ZnO}, journal = {Solar Energy}, volume = {102}, year = {2014}, month = {APR}, pages = {143-151}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, type = {Article}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

We have monitored the performance of the dye-sensitized solar cells (DSSC) using solution processed ZnO having different shapes and aspect ratios. The aspect ratio and surface area of the ZnO structures have been regulated by carefully controlling the precursor concentration and reaction conditions. The shape of the synthesized structures has been varied from larger rods to smaller rods to hexagonal prisms. The synthesized hexagonal prism shaped ZnO with an aspect ratio of around one exhibited the highest surface area of 42 m(2)/g. The ZnO rods with higher aspect ratios of 5 and 16 exhibited lower surface areas of 22 and 2 m(2)/g, respectively. The dye sensitized solar cells constructed using the as-prepared ZnO structures and N719 dye molecules, exhibited efficiencies that varied as a function of surface area of the samples, with ZnO hexagonal prism exhibiting a maximum efficiency of around 1.38 +/- 0.01\%. The results indicated a direct correlation between the surface area of the ZnO structures and the energy conversion efficiency. (C) 2014 Elsevier Ltd. All rights reserved.

}, keywords = {DSSC, Photoanode, surface area, ZnO}, issn = {0038-092X}, doi = {10.1016/j.solener.2014.01.011}, author = {Jana, Arpita and Das, Partha Pratim and Agarkar, Shruti A. and Devi, P. Sujatha} } @article { ISI:000363347800036, title = {Photochemical performance of ZnO nanostructures in dye sensitized solar cells}, journal = {Solid State Sciences}, volume = {48}, year = {2015}, month = {OCT}, pages = {237-243}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

In this work, the photoconversion efficiencies of ZnO having diverse microstructures and structural defects have been investigated. A conversion efficiency of 138\% was achieved for the DSSCs fabricated with as prepared ZnO nanorods having minimum vacancy defects and a favourable one dimensional directional pathway for electron conduction. The DSSCs fabricated with ZnO nanoparticles exhibited relatively low conversion efficiency of 1.004\% probably due to multiple trapping/detrapping phenomena within the grain boundaries and ZnO flowers though exhibited a high dye adsorption capability exhibited the lowest conversion efficiency of 0.59\% due to a high concentration of structural defects. Based on the experimental evidences, we believe that the type of defects and their concentrations are more important than shape in controlling the overall performance of ZnO based DSSCs. (C) 2015 Elsevier Masson SAS. All rights reserved.

}, keywords = {DSSC, Efficiency, Emission, Structural defects, ZnO}, issn = {1293-2558}, doi = {10.1016/j.solidstatesciences.2015.08.014}, author = {Das, Partha Pratim and Mukhopadhyay, Soumita and Agarkar, Shruti A. and Jana, Arpita and Devi, P. Sujatha} } @article {45478, title = {Evolution of ZnO nanostructures as hexagonal disk: Implementation as photoanode material and efficiency enhancement in Al: ZnO based dye sensitized solar cells}, journal = {Applied Surface Science}, volume = {470}, year = {2019}, month = {MAR}, pages = {1130-1138}, type = {Article}, abstract = {

Hexagon shaped pristine and Al doped ZnO nanodisks (NDs) with exposed +/- [0001] polar facets were successfully synthesized using modified sol-gel method without the involvement of any structural directing or capping agents. It was investigated that OH- ions in mixed solvent system is responsible for pore formation and inhibit the growth of ZnO along the direction of c-axis leading to a high percentage exposure of active +/- [0001] polar facets and encourage the formation of ZnO NDs. Crystallographic analysis revealed that crystallite size and lattice constants are decreased, with the addition of Al3+ ions. The results obtained from Raman, and XPS analysis further corroborated with the XRD results, revealed the successful incorporation of Al3+ ions into ZnO lattice. Optical study revealed the band gap tunability with the incorporation of Al ion as dopant. Enhanced power conversion efficiency (PCE) of 1.96\% (J(sc) similar to 7.69 +/- 0.23 mA/cm(2)) was observed for Al: ZnO hexagonal NDs based DSSC. The increased PCE in Al: ZnO based DSSC can be attributed to the higher inner surface area for dye anchoring by the interconnected network of the disk-like structure. The obtained results were satisfactory and most importantly the synthesis procedure proposed in present work is excellent for the synthesis of perfectly hexagonal shaped disks under precised synthesis parameters. The device interface study was further conducted using electrochemical impedance spectroscopy which revealed better charge transport process and charge storage ability with the incorporation of Al3+ ions into ZnO lattice.

}, keywords = {dye sensitized solar cells, Hexagonal disks, Sol-gel method, ZnO}, issn = {0169-4332}, doi = {10.1016/j.apsusc.2018.11.077}, author = {Parra, Mohammad Ramzan and Pandey, Padmini and Siddiqui, Hafsa and Sudhakar, Vediappan and Krishnamoorthy, Kothandam and Haque, Fozia Z.} } @article {45628, title = {Role of Li+ and Fe3+ in modified ZnO: Structural, vibrational, opto-electronic, mechanical and magnetic properties}, journal = {Ceramics International}, volume = {45}, year = {2019}, month = {JAN}, pages = {7232-7243}, type = {Article}, abstract = {When Fe is doped in ZnO, a situation of charge imbalance is created due to the higher charge of Fe3+. A charge balance may be obtained by co-doping Li+0.5Fe3+0.5 combinations. A solid solution of Zn1-x(Fe0.5Li0.5)xO (0 <= x <= 0.03125) is synthesized with this viewpoint. The crystallites belong to a wurtzite P63mc space group, with lattice parameters a, b and c increasing nominally for x = 0.0156 and thereafter remaining invariant. The size varies in the range ~ 60{\textendash}142 nm. Interstitials of Li and Zn ions are formed. Along with Fe3+ substitution these defects are reasons for O interstitials. These oxygen interstitials increase the red emission while reduction of oxygen vacancies reduces the green emission. These point defects create structural distortion and strain which can generate Zn vacancies. Bandgap reduces due to shallow defects. Mid-bandgap states due to oxygen interstitials and Fe 3d-O 2p hybridization result in NIR emission. On the other hand the crystal surface deforms due to Li addition which hardens the materials. A weak ferromagnetism appears at very low temperature which is enhanced by Li+ addition. Long range exchange mechanism between Fe3+ ions appears in the samples, mediated by magnetic polarons due to point defects.}, keywords = {hardness, NIR emission, Shallow and deep level defects, Weak ferromagnetism, ZnO}, issn = {0272-8842}, doi = {10.1016/j.ceramint.2019.01.004}, author = {Bajpai, G. and Moirangthem, I. and Sarkar, S. and Barman, S. R. and Vinod, C. P. and Bajpai, S. and Riyajuddin, S. and Ghosh, K. and Basaula, D. R. and Khan, M. and Liu, S. -W. and Biring, S. and Sen, S.} } @article {48036, title = {From molecular adsorption to decomposition of methanol on various ZnO facets: a periodic DFT study}, journal = {Applied Surface Science}, volume = {602}, year = {2022}, month = {NOV}, pages = {154150}, type = {Article}, abstract = {

Methanol is an interesting and important molecule to study because of its potential to replace existing fuels. It is also a prominent hydrogen source which can be used to generate hydrogen in-situ. ZnO is widely used as catalyst in synthesis of methanol from CO2 at industrial scale. In this work, we demonstrate that the same catalyst could be used for MeOH decomposition. We have investigated interaction of methanol with various flat and stepped facets of ZnO by employing Density Functional Theory (DFT). Two flat [(10(1)overbar 0) and (11(2)overbar 0)] and two stepped [(10(1)overbar 3) and (11(2)overbar 2)] facets are studied in detail for methanol adsorption. Chemisorption of MeOH with varying strength is common to all four facets. Most importantly spontaneous dissociation of O-H bond of methanol is observed on all facets except (11(2)overbar 0). Our DFT calculations reveal that molecular adsorption is favored on flat facets, while dissociation is favored on step facets. Also, (10(1)overbar 0) facet undergoes substantial reconstruction upon MeOH adsorption. Activation of C-H bond along with strengthening of C-O bond on ZnO facets suggest partial oxidation of methanol. With our DFT investigations, we dig deeper into the underlying electronic structure of various facets of ZnO and provide rationale for the observed facet dependent interaction of ZnO with MeOH.

}, keywords = {DFT, MeOH, Surface interactions, ZnO}, issn = {0169-4332}, doi = {10.1016/j.apsusc.2022.154150}, author = {Mehta, Shweta and Joshi, Kavita} } @article {48695, title = {Electronic fingerprints for diverse interactions of methanol with various Zn-based systems}, journal = {Surface Science}, volume = {736}, year = {2023}, month = {OCT}, pages = {122350}, type = {Article}, abstract = {

We have investigated various Zn-based catalysts for their interaction with methanol (MeOH). MeOH is one of the most critical molecules being studied extensively, and Zn-based catalysts are widely used in many industrially relevant reactions involving MeOH. We note that the same element (Zn and O, in the present study) exhibits different catalytic activity in different environments. The changing environment is captured in the underlying electronic structure of the catalysts. In the present work, we compared the electronic structure of Zn-based systems, i.e., ZnAl2O4 and ZnO along with oxygen preadsorbed Zn (O-Zn) and metallic Zn. We demonstrate the one-to-one correlation between the pDOS of the bare facet and the outcome of that facet{\textquoteright}s interaction (i.e. either adsorption or dissociation of MeOH) with MeOH. These findings would pave the way towards the in-silico design of catalysts.

}, keywords = {DFT, Electronic properties, Methanol, Zn-based systems, ZnO}, issn = {0039-6028}, doi = {10.1016/j.susc.2023.122350}, author = {Mehta, Shweta and Joshi, Kavita} } @article {48466, title = {Selective one pot multicomponent green synthesis of 3-[(aryl)(arylthio)methyl]-1H-indole derivatives utilizing enhanced Lewis acidic sites of Surfactant-assisted ZnO catalyst}, journal = {ChemistrySelect}, volume = {8}, year = {2023}, month = {MAY}, pages = {e202300736}, type = {Article}, abstract = {

Five different ZnO nanocrystallites (ZnO-1 to ZnO-5) were successfully synthesized by a surfactant-assisted hydrothermal technique using various surfactants. All the ZnO nanocrystallites are thoroughly characterized by XRD, IR, UV-DRS spectroscopy and FESEM-EDS analysis. Among the synthesized ZnO nanocrystallites, the CTAB-assisted synthesized ZnO-4 exhibited a fine disc-like morphology with a minimum crystallite size (23 nm). Subsequent to reaction optimization studies, the ZnO-4 is utilized as an efficient catalyst for one pot-three component green synthesis of 3-[(aryl)(arylthio)methyl]-1H-indoles (4a-4p) via. condensation of a variety of indoles, aromatic aldehydes and aromatic thiols at room temperature in water. The single-crystal X-ray structure of 3-[(phenyl)(phenylthio)methyl]-1H-indole (4a) is also been reported (CCDC 2170437). The Lewis acidic property of the catalyst-supported probable mechanism is well proposed subsequent to pyridine-IR studies of the ZnO catalysts. Indeed, CTAB-assisted synthesized ZnO-4 was found to be most effective and selective Lewis acid catalyst for the synthesis of a variety of 3-[(aryl)(arylthio)methyl]-1H-indole derivatives in water at ambient temperature with merits like higher yields, lower reaction time, catalyst recovery and reuse.

}, keywords = {3-[(aryl)(arylthio)methyl]-1H-indole, green synthesis, Lewis acidity, Single crystal, ZnO}, issn = {2365-6549}, doi = {10.1002/slct.202300736}, author = {Sangale, Vijay B. B. and Jagtap, Rohidas M. M. and Mali, Bhupendra P. P. and Gonnade, Rajesh G. G. and Pardeshi, Satish K. K.} } @article {49310, title = {From digital blueprint to chemical reality: methanol to formaldehyde at ambient conditions}, journal = {Applied Surface Science}, volume = {669}, year = {2024}, month = {OCT }, pages = {160527}, type = {Article}, abstract = {

Partial oxidation of methanol to value added product presents an intriguing yet challenging process. Among these products, formaldehyde is the simplest and one of the most vital aliphatic aldehydes, which has extensive application across various domains. Industrially, silver and iron-molybdenum oxides are used as catalysts for the conversion of methanol to formaldehyde at elevated temperatures (600 degrees C and 250-400 degrees C, respectively). However, in this computational and experimental study, we have demonstrated the efficacy of ZnO as a catalyst. Notably, in the presence of ZnO, methanol readily converts to formaldehyde even under ambient conditions. We employed periodic density functional theory (DFT) to explore (10 1 1) facet of ZnO to elucidate its interaction with methanol. Our comprehensive analysis identified the most active facet (10 1 1) involved in the spontaneous conversion of methanol to formaldehyde. Subsequently, experimental validation supported our theoretical findings, demonstrating the conversion of methanol to formaldehyde with 100\% selectivity at room temperature and atmospheric pressure in the presence of ZnO. This study exemplifies the pivotal role of theory in catalyst design.

}, keywords = {DFT, Formaldehyde, MeOH, ZnO}, issn = {0169-4332}, doi = {10.1016/j.apsusc.2024.160527}, author = {Mehta, Shweta and Kasabe, Mirabai and Umbarkar, Shubhangi B. and Joshi, Kavita} } @article {48999, title = {Tuning the optical properties of Ln3+-doped-Y2O3@ZnO@Au core-shell heterostructures for visible-to-NIR photon harvesting}, journal = {Surfaces and Interfaces }, volume = {44}, year = {2024}, month = {JAN}, type = {Article}, abstract = {

Here, compact Yb3+-Er3+-Tm3+ doped Y2O3 phosphor microspheres were synthesized by solvothermal method which gave emission in the entire visible region under 980 nm excitation. The effect of doping alkali ions like lithium on the upconversion emission of YYET phosphors is investigated. An epitaxial layer of ZnO is grown around the YYETL (Li+ doped YYET) microspheres by hydrothermal technique. An analysis of the influence of the ZnO shell thickness on the upconversion emission of core microspheres is done. Initial growth of a thin layer of ZnO on the YYETL microspheres causes enhancement in upconversion emission due to passivation of surface defects of core microspheres. Quenching of anti-Stokes emission occurs for thicker ZnO shell coating. Further, it is decorated with AuNPs to study the effect of plasmonics on the optical property of the developed heterostructure. The overlap between the upconversion emission spectra of core microspheres and the LSPR peak of AuNPs modulates the property of the entire structure. The optimized samples were checked for photocatalytic application by degradation of Rh6G dye under solar irradiation. YYETL@ZnO@Au core-shell samples exhibited highest rate constant of 0.00395 min(-1), which is attributed to better exploitation of the UV-Vis-NIR region of the solar spectrum by all three components of the heterostructure.

}, keywords = {AuNPs, Core-shell heterostructure, LRET, Photocatalysis, Upconversion microspheres, ZnO}, issn = {2468-0230}, doi = {10.1016/j.surfin.2023.103775}, author = {Jayswal, Shefali and Luwang, Meitram Niraj and Moirangthem, Rakesh S.} } @article {50019, title = {When facets meet impurities: Trace gas dominance over CO2 adsorption on ZnO}, journal = {Applied Surface Science}, volume = {729}, year = {2026}, month = {MAY}, pages = {166151}, type = {Article}, abstract = {

The catalytic hydrogenation of CO2 to methanol using Cu-ZnO/Al2O3 (CZA) is a key route for sustainable chemical production, when coupled with CO2-rich industrial off-gases. However, trace secondary gases, though present only at ppm levels, can poison active sites and suppress catalytic performance. In this work, we employ periodic density functional theory (DFT) to investigate interactions of H2S, SO2, NO2, NO, CO and CH4 with ZnO surfaces:(10(-)10), (10(-)11), (11(-)20), (10(-)13), and (11(-)22), and compared their adsorption pattern with CO2, the principle component of methanol synthesis. H2S dissociates on all the surfaces, SO2, and NO2 are chemisorbed, CH4 remains physisorbed, and NO, CO, and CO2 exhibit facet-dependent adsorption. Electronic structure analysis reveal that chemisorption occurs when surface energy states near the Fermi level overlap with HOMO of adsorbate, enabling charge transfer, whereas physisorption lacks such overlap. The adsorption strength follows the order: H2S SO2 NO2 NO CO CO2 CH4, suggesting that sulfur and nitrogen containing species exhibit strong chemisorption and compete with CO2 for active sites, potentially impacting the efficiency of methanol synthesis. These insights provide an atomic scale understanding of impurity-surface interactions and highlight potential role of ZnO as an efficient feed stock purifier for CO2-rich gas streams.

}, keywords = {CZA catalyst, flue gases, Valorization of CO2, ZnO}, issn = {0169-4332}, doi = {10.1016/j.apsusc.2026.166151}, author = {Bhati, Meema and Joshi, Kavita} }