@article { ISI:000245870400056, title = {Energy analysis of field emitted electrons from a ZnO tetrapod}, journal = {Applied Physics Letters}, volume = {90}, number = {16}, year = {2007}, month = {APR}, pages = {Article No. 162102}, publisher = {AMER INST PHYSICS}, type = {Article}, address = {CIRCULATION \& FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA}, abstract = {

The experimental total energy distribution (TED) of the field emitted electrons from a single pod of a ZnO tetrapod has been obtained, exhibiting a two-peak feature. The energy difference between the two peaks in the TED is found to be nearly equal to the band gap of the bulk ZnO. The results show that field emitted electrons originate from both the conduction and valence bands. The peak position dependence on the applied voltage has also been observed. In the present case, the size of the ZnO tetrapod is not small enough to reflect the quantum confinement effects.

}, issn = {0003-6951}, doi = {10.1063/1.2723199}, author = {Al-Tabbakh, Ahmed A. and More, Mahendra A. and Joag, Dilip S. and Ramgir, Niranjan S. and Mulla, Imtiaz S. and Pillai, Vijayamohanan K.} } @article { ISI:000255728500004, title = {Efficient route towards the covalent functionalization of single walled carbon nanotubes}, journal = {Applied Surface Science}, volume = {254}, number = {16}, year = {2008}, month = {JUN}, pages = {4936-4943}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

A simple and efficient method of chemical functionalization of both single and multiwalled carbon nanotubes has been discussed to give enhanced water solubility by rapidly and efficiently generating an appreciable amount of hydrophilic functional groups using microwave radiation. Surface functionalization containing more than 30 wt\% of oxygen has been achieved, resulting into solubility of 2-5 mg/mL. Further covalent functionalization of such soluble SWNTs provides a remarkable degree of aniline functionalization through amidation, where the formation of polyaniline has been avoided. Functionalization of SWNTs is confirmed by techniques like electron microscopy, Fourier transform infrared spectroscopy, thermogravimetry, Raman spectroscopy, cyclic voltammetry and impedance spectroscopy. Electrochemical analysis suggests an enhanced double layer capacitance (similar to 110 F/g) of nanotubes after microwave treatment. Aniline functionalization of SWNTs shows possible variations on the nanotube topography with concomitant formation of a dynamic polymer layer on the nanotube surface. (C) 2008 Elsevier B.V. All rights reserved.

}, keywords = {Carbon nanotubes, Functionalization, Microwave, solubility}, issn = {0169-4332}, doi = {10.1016/j.apsusc.2008.01.148}, author = {Kakade, Bhalchandra A. and Pillai, Vijayamohanan K.} } @article { ISI:000257271600056, title = {Electrochemical sensing of sulphur dioxide: a comparison using dodecanethiol and citrate capped gold nanoclusters}, journal = {Journal of Nanoscience and Nanotechnology}, volume = {8}, number = {6}, year = {2008}, month = {JUN}, pages = {3184-3190}, publisher = {AMER SCIENTIFIC PUBLISHERS}, type = {Article}, address = {26650 THE OLD RD, STE 208, VALENCIA, CA 91381-0751 USA}, abstract = {

A comparison of cyclic voltammograms of dodecanethiol (DDT) capped Au nanoclusters (5.0 +/- 0.5 nm) and trisodium citrate (Cit) capped Au nanoclusters (similar to 10-15 nm) modified glassy carbon electrode shows a dramatic variation in the current when exposed to a small amount of sulphur dioxide. This is explained using the electrocatalytic properties of Au nanoclusters towards the oxidation of SO2, thus facilitating the fabrication of electrochemical sensors for the detection of SO2. The intrinsic redox changes observed for gold nanocluster-modified glassy carbon electrodes disappear on passing SO2, despite a dramatic current increase, which indeed scales up with the amount of dissolved SO2. Interestingly, a complete rejuvenation of the redox behavior of gold is also observed on subsequent removal of SO2 from the solution by passing pure nitrogen for 15 minutes. Further, these nanoclusters when characterized with X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) after SO2 passage reveal a variety of SO2 adsorption modes on gold surface. XP spectra also show a shift of 1.03 eV towards higher binding energy indicating a strong adsorption of SO2 gas, while FTIR gives conclusive evidence for the interaction of SO2 with gold nanoparticles.

}, keywords = {cyclic voltammetry, Fourier transform infrared spectroscopy, monolayer protected gold nanoclusters (Au-MPCs), SO2 sensor, X-ray photoelectron spectra}, issn = {1533-4880}, doi = {10.1166/jnn.2008.094}, author = {Sathe, Bhaskar R. and Risbud, Mandar S. and Mulla, Imtiaz S. and Pillai, Vijayamohanan K.} } @article { ISI:000257231200057, title = {Enhanced field emission from hexagonal rhodium nanostructures}, journal = {Applied Physics Letters}, volume = {92}, number = {25}, year = {2008}, month = {JUN}, pages = {253106}, publisher = {AMER INST PHYSICS}, type = {Article}, address = {CIRCULATION \& FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA}, abstract = {

Shape selective synthesis of nanostructured Rh hexagons has been demonstrated with the help of a modified chemical vapor deposition using rhodium acetate. An ultralow threshold field of 0.72 V/mu m is observed to generate a field emission current density of 4 x 10(-3) mu A/cm(2). The high enhancement factor (9325) indicates that the origin of electron emission is from nanostructured features. The smaller size of emitting area, excellent current density, and stability over a period of more than 3 h are promising characteristics for the development of electron sources. (C) 2008 American Institute of Physics.

}, issn = {0003-6951}, doi = {10.1063/1.2943657}, author = {Sathe, Bhaskar R. and Kakade, Bhalchandra A. and Mulla, Imtiaz S. and Pillai, Vijayamohanan K. and Late, Dattatray J. and More, Mahendra A. and Joag, Dilip S.} } @article { ISI:000278592400024, title = {Effect of Fe3O4 on morphology of Fe-SnO2 hyperbranched heterostructures}, journal = {Chemical Physics Letters}, volume = {493}, number = {1-3}, year = {2010}, month = {JUN}, pages = {121-125}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

A simple modified thermal evaporation technique is employed for the synthesis of microstructured Fe:SnO2 system and their plausible growth mechanism has been proposed based on the results from various characterization techniques. Such structures grow in two steps; initially, growth of Fe core takes place from Fe3O4 source which acts as nucleating site for SnO2 growth on its surface as per the vapor-liquid- solid progression. Moreover, the composition of Fe/Sn source and temperature are found to have key roles in governing their morphology. XPS studies clearly demonstrate the presence of Fe species, which acts as a catalyst along with source for hetero-structure growth with SnO2. (C) 2010 Published by Elsevier B.V.

}, issn = {0009-2614}, doi = {10.1016/j.cplett.2010.05.019}, author = {Sathe, Bhaskar R. and Walke, Pravin S. and Mulla, Imtiaz S. and Pillai, Vijayamohanan K.} } @article { ISI:000291715300005, title = {Electrochemical unzipping of multi-walled carbon nanotubes for facile synthesis of high-quality graphene nanoribbons}, journal = {Journal of the American Chemical Society}, volume = {133}, number = {12}, year = {2011}, month = {MAR}, pages = {4168-4171}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Here we report a remarkable transformation of carbon nanotubes (CNTs) to nanoribbons composed of a few layers of graphene by a two-step electrochemical approach. This consists of the oxidation of CNTs at controlled potential, followed by reduction to form graphene nanoribbons (GNRs) having smooth edges and fewer defects, as evidenced by multiple characterization techniques, including Raman spectroscopy, atomic force microscopy, and transmission electron microscopy. This type of {\textquoteleft}{\textquoteleft}unzipping{\textquoteright}{\textquoteright} of CNTs (single-walled, multi-walled) in the presence of an interfacial electric field provides unique advantages with respect to the orientation of CNTs, which might make possible the production of GNRs with controlled widths and fewer defects.

}, issn = {0002-7863}, doi = {10.1021/ja1101739}, author = {Shinde, Dhanraj B. and Debgupta, Joyashish and Kushwaha, Ajay and Aslam, Mohammed and Pillai, Vijayamohanan K.} } @article { ISI:000290732000044, title = {Enhanced electrocatalytic performance of functionalized carbon nanotube electrodes for oxygen reduction in proton exchange membrane fuel cells}, journal = {Physical Chemistry Chemical Physics}, volume = {13}, number = {21}, year = {2011}, month = {APR}, pages = {10312-10317}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Although nitrogen doped CNTs (N-CNTs) are considered as a promising alternative to platinized carbon for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells (PEMFCs), the origin of the enhanced ORR activity with N-CNTs is not clear at present. Among several plausible reasons, the exposure of edge plane and creation of impurity band/surface states near the Fermi level are considered as major causes behind the catalytic activity. However, CNTs without nitrogen doping are not known to catalyze the ORR. In this work, we study the ORR activity of functionalized carbon nanotubes with different functional groups, such as sulfonic acid and phosphonic acid, in order to understand the role of surface functionalities in catalyzing the reaction. Functionalized CNTs show significantly enhanced activity towards the ORR, while CNTs without such surface functional groups do not reveal any such special ORR activity. Linear sweep voltammetry experiments with different rotation rates show diffusion controlled limiting current values for functionalized CNTs, and the {\textquoteleft}n{\textquoteright} values derived from Koutecky-Levich plots are 3.3 and 1.7 for S-MWCNTs and P-MWCNTs, respectively. This work demonstrates the ORR activity of functionalized MWCNTs, which opens up new strategies for electrocatalyst design in PEMFCs.

}, issn = {1463-9076}, doi = {10.1039/c0cp02853c}, author = {Kannan, Ramaiyan and Bipinlal, Unni and Kurungot, Sreekumar and Pillai, Vijayamohanan K.} } @article { ISI:000287924700049, title = {Enhanced electrocatalytic performance of interconnected Rh nano-chains towards formic acid oxidation}, journal = {Energy \& Environmental Science}, volume = {4}, number = {3}, year = {2011}, month = {MAR}, pages = {1029-1036}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A chain-like assembly of rhodium nanoparticles (5-7 nm mean diameter) has been synthesized from rhodium chloride with the help of polydentate molecules like tartaric and ascorbic acids (1 : 3 in mM scale) as capping agents at room temperature. Subsequent characterization using transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy reveals a unique inter-connected network like features, while their electrochemical behavior using cyclic voltammetry and current-time transient suggests potential applications as electrocatalysts in fuel cells. A significant negative shift in the onset potential as well as higher anodic peak current density for formic acid oxidation on Rh-tartaric acid (Rh-TA) as compared to that of bulk Rh metal confirms their higher electrocatalytic activity. Interestingly, the enhancement factor (R) with respect to that of bulk metallic Rh towards formic acid oxidation ranges up to 2000\% for Rh-TA and 1200\% for Rh-AA (Rh-ascorbic acid) respectively. The composition of Rh nano-chains has been further analyzed with thermogravimetry and Fourier transform infra-red spectroscopy to demonstrate the importance of controlling the chain topology using polyfunctional organic molecules. These findings open up new possibilities for tailoring nanostructured electrodes with potential benefits since the development of a better electrocatalysts for many fuel cell reactions continues to be an important challenge.

}, issn = {1754-5692}, doi = {10.1039/c0ee00219d}, author = {Sathe, Bhaskar R. and Balan, Beena K. and Pillai, Vijayamohanan K.} } @article { ISI:000288386600076, title = {Ex-situ dispersion of core-shell nanoparticles of Cu-Pt on an in situ modified carbon surface and their enhanced electrocatalytic activities}, journal = {Chemical Communications}, volume = {47}, number = {13}, year = {2011}, month = {FEB}, pages = {3951-3953}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Direct dispersion of core-shell nanoparticles on a carbon support (Cu@ Pt/C) has been achieved while retaining the essential core-shell features of the nanoparticles by adopting an in situ surface modification-cum-anchoring strategy.

}, issn = {1359-7345}, doi = {10.1039/c0cc05645f}, author = {Dhavale, Vishal M. and Unni, SreeKuttan M. and Kagalwala, Husain N. and Pillai, Vijayamohanan K. and Kurungot, Sreekumar} } @article { ISI:000308879000041, title = {Electrochemical preparation of luminescent graphene quantum dots from multiwalled carbon nanotubes}, journal = {Chemistry-A European Journal}, volume = {18}, number = {39}, year = {2012}, month = {SEP}, pages = {12522-12528}, publisher = {WILEY-V C H VERLAG GMBH}, address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY}, abstract = {

Green luminescent, graphene quantum dots (GQDs) with a uniform size of 3, 5, and 8.2(+/- 0.3) nm in diameter were prepared electrochemically from MWCNTs in propylene carbonate by using LiClO4 at 90?degrees C, whereas similar particles of 23(+/- 2) nm were obtained at 30?degrees C under identical conditions. Both these sets of GQDs displayed a remarkable quantum efficiency of 6.3 and 5.1?\%, respectively. This method offers a novel strategy to synthesise size-tunable GQDs as evidenced by multiple characterisation techniques like transmission and scanning electron microscopy, atomic force microscopy, Raman spectroscopy and X-ray diffraction (XRD). Photoluminescence of these GQDs can be tailored by size variation through a systematic change in key process parameters, like diameter of carbon nanotube, electric field, concentration of supporting electrolyte and temperature. GQDs are promising candidates for a variety of applications, such as biomarkers, nanoelectronic devices and chemosensors due to their unique features, like high photostability, biocompatibility, nontoxicity and tunable solubility in water.

}, keywords = {electrochemical synthesis, graphene, Nanostructures, photoluminescence, quantum dots}, issn = {0947-6539}, doi = {10.1002/chem.201201043}, author = {Shinde, Dhanraj B. and Pillai, Vijayamohanan K.} } @article { ISI:000315209900016, title = {Electrochemical resolution of multiple redox events for graphene quantum dots}, journal = {Angewandte Chemie-International Edition}, volume = {52}, number = {9}, year = {2013}, month = {JAN}, pages = {2482-2485}, publisher = {WILEY-V C H VERLAG GMBH}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, keywords = {charging energy, differential pulse voltammetry, graphene, quantum dots, single-electron transfer}, issn = {1433-7851}, doi = {10.1002/anie.201208904}, author = {Shinde, Dhanraj B. and Pillai, Vijayamohanan K.} } @article { ISI:000339861500096, title = {Electrochemical preparation of vertically aligned, hollow CdSe nanotubes and their p-n junction hybrids with electrodeposited Cu2O}, journal = {Nanoscale}, volume = {6}, number = {15}, year = {2014}, month = {AUG}, pages = {9148-9156}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Vertically aligned, hollow nanotubes of CdSe are grown on fluorine doped tin oxide (FTO) coated glass substrates by ZnO nanowire template-assisted electrodeposition technique, followed by selective removal of the ZnO core using NH4OH. A detailed mechanism of nucleation and anisotropic growth kinetics of nanotubes have been studied by a combination of characterization tools such as chronoamperometry, SEM and TEM. Interestingly, {\textquoteleft}{\textquoteleft}as grown{\textquoteright}{\textquoteright} CdSe nanotubes (CdSe NTs) on FTO coated glass plates behave as n-type semiconductors exhibiting an excellent photo-response (with a generated photocurrent density value of similar to 470 mu A cm(-2)) white in contact with p-type Cu2O (p-type semiconductor, grown separately on FTO plates) because of the formation of a n-p heterojunction (type II). The observed photoresponse is 3 times higher than that of a similar device prepared with electrodeposited CdSe films (not nanotubes) and Cu2P on FTO. This has been attributed to the hollow 1-D nature of CdSe NTs, which provides enhanced inner and outer surface areas for better absorption of light and also assists faster transport of photogenerated charge carriers.

}, issn = {2040-3364}, doi = {10.1039/c3nr06917f}, author = {Debgupta, Joyashish and Devarapalli, Rami Reddy and Rahman, Shakeelur and Shelke, Manjusha V. and Pillai, Vijayamohanan K.} } @article { ISI:000353831200020, title = {Electrochemical preparation of nitrogen-doped graphene quantum dots and their size-dependent electrocatalytic activity for oxygen reduction}, journal = {Bulletin of Materials Science}, volume = {38}, number = {2}, year = {2015}, month = {APR}, pages = {435-442}, publisher = {INDIAN ACAD SCIENCES}, address = {C V RAMAN AVENUE, SADASHIVANAGAR, P B \#8005, BANGALORE 560 080, INDIA}, abstract = {

Here we report a remarkable transformation of nitrogen-doped multiwalled carbon nanotubes (MWCNTs) to size selective nitrogen-doped graphene quantum dots (N-GQDs) by a two-step electrochemical method. The sizes of the N-GQDs strongly depend on the applied anodic potential, moreover increasing potential resulted in a smaller size of N-GQDs. These N-GQDs display many unusual size-dependant optoelectronic (blue emission) and electrocatalytic (oxygen reduction) properties. The presence of N dopants in the carbon framework not only causes faster unzipping of MWCNTs but also provides more low activation energy site for enhancing the electrocatalytic activity for technologically daunting reactions like oxygen reduction. The smaller size of N-GQDs has shown better performance as compared to the large N-GQDs. Interestingly, N-GQDs-3 (size = 2.5 +/- 0.3 nm, onset potential = 0.75 V) show a 30-mV higher positive onset potential shift compared to that of N-GQDs-2 (size = 4.7 +/- 0.3 nm, onset potential = 0.72 V) and 70 mV than that of N-GQDs-1 (size = 7.2 +/- 0.3, onset potential = 0.68 V) for oxygen reduction reaction (ORR) in a liquid phase. These result in the size-dependent electrocatalytic activity of N-GQDs for ORR as illustrated by the smaller sized N-GQDs (2.5 +/- 0.3 nm) undoubtedly promising metal-free electrocatalysts for fuel cell applications.

}, keywords = {fuel cells, MWCNTs, N-GQDs, oxygen reduction reaction, unzipping}, issn = {0250-4707}, doi = {10.1007/s12034-014-0834-3}, author = {Shinde, Dhanraj B. and Dhavale, Vishal M. and Kurungot, Sreekumar and Pillai, Vijayamohanan K.} } @article { ISI:000368191100026, title = {Enhanced nucleation of polypropylene by metal-organic frameworks (MOFs) based on aluminium dicarboxylates: influence of structural features}, journal = {RSC Advances}, volume = {6}, number = {3}, year = {2016}, month = {DEC}, pages = {1907-1912}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Metal-organic frameworks (MOFs) based on aluminium dicarboxylates provide a new platform for the enhanced nucleation of isotactic polypropylene (iPP). For instance, aluminium dicarboxylates exhibit a unique butterfly-like structure similar to that of carboxylate-alumoxanes and correlates well with the nucleation characteristics of iPP. A subtle change in the structure of the ligand backbone (fumarate/succinate) does not alter the framework structure despite changing the hydrophilic/hydrophobic character and its subsequent nucleation characteristics. This suggests that the nucleating agent should facilitate favourable interaction with hydrophobic iPP for efficient nucleation. Further, a systematic variation of the alkyl chain length in the Al-dicarboxylate does not change the nucleation efficiency considerably, even though it increases the distance between the octahedral alumina chains in the metal-organic framework, suggesting that the butterfly-like structure present in the framework is a key aspect for nucleation. Finally, the significance of the orientational conformation of the dicarboxylate around the metal centre for the nucleation is confirmed by the poor nucleation efficiency of chromium and zirconium suberate MOFs where the orientation of suberate would be different from that of aluminium suberate due to the difference in the ligation of the carboxylate group. The present work thus provides valuable pathways for developing new nucleating agents based on MOFs with appropriate selection and orientation of the organic linkers around the metal centre.

}, issn = {2046-2069}, doi = {10.1039/c5ra22764j}, author = {Mani, Mohan Raj and Chellaswamy, Ramesh and Marathe, Yogesh N. and Pillai, Vijayamohanan K.} }