@article { ISI:000238294800037, title = {Suppression of electron-transfer characteristics of ferrocene by OTS monolayer on a silicon/electrolyte interface}, journal = {Journal of Colloid and Interface Science}, volume = {299}, number = {2}, year = {2006}, month = {JUL}, pages = {777-784}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

The passivating behavior of self-assembled monolayers (SAMs) of octadecyltrichlorosilane (OTS) on an n-type Si(100) electrode with and without a redox species like ferrocene in a polar non-aqueous medium has been investigated using techniques like contact angle measurements, Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) to understand the role of the monolayer. The electron-transfer behavior of ferrocene is found to be drastically affected by the presence of monolayer and the reasons for these are analyzed as a function of the change in resistance, dielectric thickness and coverage of the monolayer. Electrochemical impedance analysis in the presence of ferrocene gives the monolayer coverage as 0.998 and the apparent rate constant calculated from this gives 4.85 x 10(-12) cm s(-1) in comparison with 4.4 x 10(-8) cm s(-1) for a similar electrode without any monolayer. A positive shift of 200 mV in the flat-band potential after monolayer formation also suggests the covalent coupling of the silane nionolayer offering a protective barrier. (c) 2006 Elsevier Inc. All rights reserved.

}, keywords = {cyclic voltammetry, ferrocene, impedance analysis, octadecyltrichlorosilane (OTS), rate constant, self-assembled monolayer (SAM)}, issn = {0021-9797}, doi = {10.1016/j.jcis.2006.03.013}, author = {Kulkarni, S. A. and Kakade, Bhalchandra A. and Mulla, Imtiaz S. and Pillai, V. K.} } @article { ISI:000250661500014, title = {All-solid-state{\textquoteright} electrochemistry of a protein-confined polymer electrolyte film}, journal = {Biochemical and Biophysical Research Communications}, volume = {364}, number = {1}, year = {2007}, month = {DEC}, pages = {86-91}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

Interfacial redox behavior of a heme protein (hemoglobin) confined in a solid polymer electrolyte membrane, Nafion (a perfluoro sulfonic acid ionomer) is investigated using a unique {\textquoteleft}all-solid-state{\textquoteright} electrochemical methodology. The supple phase-separated structure of the polymer electrolyte membrane, with hydrophilic pools containing solvated protons and water molecules, is found to preserve the incorporated protein in its active form even in the solid-state, using UV-visible, Fluorescence (of Tryptophan and Tyrosine residues) and DRIFT (diffuse reflectance infrared Fourier transform) spectroscopy. More specifically, solid-state cyclic voltammetry and electrochemical impedance of the protein-incorporated polymer films reveal that the Fe2+-form of the entrapped protein is found to bind molecular oxygen more strongly than the native protein. In the {\textquoteleft}all-solid-state{\textquoteright} methodology, as there is no need to dip the protein-modified electrode in a liquid electrolyte (like the conventional electrochemical methods), it offers an easier means to study a number of proteins in a variety of polymer matrices (even biomimetic assemblies). In addition, the results of the present investigation could find interesting application in a variety of research disciplines, in addition to its fundamental scientific interest, including protein biotechnology, pharmaceutical and biomimetic chemistry. (C) 2007 Elsevier Inc. All rights reserved.

}, keywords = {all-solid-state, cyclic voltammetry, hemoglobin, Impedance, Nafion, redox behavior}, issn = {0006-291X}, doi = {10.1016/j.bbrc.2007.09.118}, author = {Parthasarathy, Meera and Pillai, Vijayamohanan K. and Mulla, Imtiaz S. and Shabab, Mohammed and Khan, Mohammad Islam} } @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.} }