02580nas a2200169   4500008004100000022001400041245014400055210006900199260007100268300001400339490000700353520184400360100002502204700003002229700003002259856012102289       2006                        eng d  a0897-475600aAutoreduction of cyanoferrate(III) ions in a polymer electrolyte membrane: all solid state electrochemical and spectroscopic investigations0 aAutoreduction of cyanoferrateIII ions in a polymer electrolyte m  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcOCT  a5244-52520 v183 a<p>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 ``all-solid-state'' 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).</p>1 aParthasarathy, Meera1 aGopinath, Chinnakonda, S.1 aPillai, Vijayamohanan, K.  uhttps://library.ncl.res.in/content/autoreduction-cyanoferrateiii-ions-polymer-electrolyte-membrane-all-solid-state-102379nas a2200265   4500008004100000022001400041245008500055210006900140260009500209300001000304490000800314520144900322653002001771653002301791653001501814653001401829653001101843653001901854100002501873700003001898700002201928700002101950700002601971856011601997       2007                        eng d  a0006-291X00aAll-solid-state' electrochemistry of a protein-confined polymer electrolyte film0 aAllsolidstate electrochemistry of a proteinconfined polymer elec  a525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USAbACADEMIC PRESS INC ELSEVIER SCIENCEcDEC  a86-910 v3643 a<p>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 `all-solid-state' 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 `all-solid-state' 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.</p>10aall-solid-state10acyclic voltammetry10ahemoglobin10aImpedance10aNafion10aredox behavior1 aParthasarathy, Meera1 aPillai, Vijayamohanan, K.1 aMulla, Imtiaz, S.1 aShabab, Mohammed1 aKhan, Mohammad, Islam  uhttps://library.ncl.res.in/content/all-solid-state-electrochemistry-protein-confined-polymer-electrolyte-film-002649nas a2200193   4500008004100000022001400041245009900055210006900154260007100223300001600294490000800310520188000318100002502198700002502223700002302248700002202271700003002293856013202323       2007                        eng d  a1932-744700aSurface-state-mediated electron transfer at nanostructured ZnO multipod/electrolyte interfaces0 aSurfacestatemediated electron transfer at nanostructured ZnO mul  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcSEP  a13092-131020 v1113 a<p>Redox kinetics of cyanoferrate(III) species adsorbed at an n-type ZnO multipod/electrolyte interface is explored using electrochemical techniques like cyclic voltammetry and impedance spectroscopy. The electrochemical impedance results are analyzed using a fluctuating energy level model, assuming isoenergetic tunneling of majority carriers through the Helmholtz layer. A shift in the slope of Mott-Schottky plots (C-sc(-2) versus E) together with evidence from cyclic voltammetry shows that the electron-transfer process is mediated by surface states formed because of the adsorption of ferricyanide ions (as evident from the results of Fourier transform infrared spectroscopy). More significantly, the pH of zero charge (point of zero zeta potential, pzzp) of ZnO multipods is found to be 4.5 (from capacitance vs pH plots) compared to that of bulk ZnO (pH 9.5), which could be explained on the basis of a lowering in the work function of the nanostructured semiconductor and its consequent susceptibility to the formation of surface states. This is in excellent agreement with our earlier observation of ultralow threshold field emission with this material in the light of the linear dependence of pzzp with work function of the electrode material. The flat-band potential of the nanostructures is found to be 200 mV more negative than that reported for bulk n-type ZnO electrodes, indicating a higher doping density in the former. A three-dimensional mapping of charge distribution in the surface states is attempted by correlating the capacitance response of the system subjected to a sinusoidal potential modulation to the semiconductor electrode with that resulting from a systematic variation of the redox potential of the dissolved acceptor (achieved by varying the pH of the electrolyte) which further reveals the polyenergetic nature of the surface states.</p>1 aParthasarathy, Meera1 aRamgir, Niranjan, S.1 aSathe, Bhaskar, R.1 aMulla, Imtiaz, S.1 aPillai, Vijayamohanan, K.  uhttps://library.ncl.res.in/content/surface-state-mediated-electron-transfer-nanostructured-zno-multipodelectrolyte-interfaces-002175nas a2200253   4500008004100000022001400041245011500055210006900170260008000239300001400319490000800333520125000341653002001591653002101611653001901632653000901651653002601660653001201686100002501698700001801723700001901741700003001760856013101790       2008                        eng d  a1618-264200aImaging the stomatal physiology of somatic embryo-derived peanut leaves by scanning electrochemical microscopy0 aImaging the stomatal physiology of somatic embryoderived peanut   aTIERGARTENSTRASSE 17, D-69121 HEIDELBERG, GERMANYbSPRINGER HEIDELBERGcJUL  a2227-22330 v3913 a<p>The stomatal physiology, chlorophyll distribution and photosynthetic activity of somatic embryo (SE)- and seedling-derived peanut plants grown in vitro (test tube-grown) and extra vitrum (soil-grown) are investigated using scanning electrochemical microscopy (SECM). This SECM imaging is performed in two different feedback modes, corresponding to oxygen evolution and chlorophyll distribution. More specifically, the oxygen evolution profiles of the in vitro leaves indicate important differences in leaf anatomy between the SE- and seedling-derived leaves. On the other hand, the chlorophyll distribution images show individual stomata of size ca. 27 +/- 5 mu m. Further studies on senescing (aged) leaves reveal interesting voltammograms that vary widely over the stomatal complexes and the surrounding tissues, probably due to the release of electroactive metabolites during chlorophyll breakdown when the leaves turn yellow. Thus, the present investigation could open up new opportunities for characterizing botanical systems using electroanalytical techniques. In addition, it could provide further insights into various areas of current relevance, including signal transduction, cell fate/differentiation and developmental biology.</p>10aleaf senescence10aoxygen evolution10aphotosynthesis10aSECM10asomatic embryogenesis10astomata1 aParthasarathy, Meera1 aSingh, Shweta1 aHazra, Sulekha1 aPillai, Vijayamohanan, K.  uhttps://library.ncl.res.in/content/imaging-stomatal-physiology-somatic-embryo-derived-peanut-leaves-scanning-electrochemical-002473nas a2200169   4500008004100000022001400041245012700055210006900182260007100251300001400322490000700336520175100343100002502094700002802119700003002147856012602177       2008                        eng d  a0024-929700aTuning the transport properties of Poly(oxyethylene)bisamine - Nafion polyelectrolyte complexes by dielectric manipulation0 aTuning the transport properties of Polyoxyethylenebisamine Nafio  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcMAY  a3653-36580 v413 a<p>Polyelectrolyte complexes (PECs) of Nafion-H+, a perfluorosulfonic acid ionomer, and Poly(oxyethylene)bisamine (Polyox) were synthesized, and the effect of electrostatic interactions on the physicochemical properties of the individual components was studied using a combination of spectroscopic and electrochemical techniques. More specifically, the pristine PECs were extensively characterized using viscosity, surface tension, and pH measurements and diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy and their transport properties were investigated using cyclic voltammetry and electrochemical impedance spectroscopy, by employing [Fe(CN)(6)](3-) as a redox probe. Acid-base interaction between Nafion and Polyox is evident from pH measurements of the blend solutions, which indicate salt formation at a 50:50 composition, supported further by the existence of a maximum in the plot of surface tension versus blend composition. DRIFT spectra of the PEC membranes indicate subtle changes in the ionic environment and a transition from a state of medium hydration to a partially dehydrated state of the parent ionomer, Nation, after complexation with Polyox. Further evidence for polyelectrolyte-polyelectrolyte association is obtained from cyclic voltammetry, which shows that the interaction between the redox active chromophore, [Fe(CN)(6)](3-), and the pendent sulfonate groups of Nafion is minimized by complexation with the oppositely charged polyelectrolyte Polyox. The water-soluble nature of these PECs along with the tunable range of properties with blend composition could qualify them as suitable candidates for developing stimuli-responsive polymer systems for pharmaceutical and environmental applications.</p>1 aParthasarathy, Meera1 aKakade, Bhalchandra, A.1 aPillai, Vijayamohanan, K.  uhttps://library.ncl.res.in/content/tuning-transport-properties-polyoxyethylenebisamine-nafion-polyelectrolyte-complexes-002340nas a2200193   4500008004100000022001400041245014100055210006900196260007100265300001400336490000700350520152700357100002101884700002501905700003001930700002401960700003001984856013202014       2009                        eng d  a0743-746300aDomain size manipulation of perflouorinated polymer electrolytes by sulfonic acid-functionalized MWCNTs to enhance fuel cell performance0 aDomain size manipulation of perflouorinated polymer electrolytes  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcJUL  a8299-83050 v253 a<p>The application of sulfonic acid-functionalized multiwalled (s-MWNT) carbon nanotubes to manipulate the hydrophilic domain size of Nafion membranes is explored here as an option for tuning the proton conductivity of polymer electrolyte membranes for hydrogen-oxygen fuel cells. The electrochemical impedance experiments provide preliminary evidence of increased proton conductivity, while small-angle X-ray scattering measurements line. out enhanced ionic cluster domain size in these composite membranes as the central reason for higher conductivity (70 angstrom for the optimum composite membrane vs 50 angstrom for Nafion 115) values. Scanning electrochemical microscopy indicates synergistic interaction between the sulfonic acid functional groups present in the Nation membrane and those on the nanotube surface. More interestingly, the nanotube-tailored Nafion membranes ameliorate the performance of fuel cells as confirmed by measurements at a sin le-cell level, which reveal a maximum power density of 380 mW cm(-2), higher than those of Nafion 115 (250 mW cm(-2)) and recast Nafion (230 mW cm-2) membranes. Thus, in addition to providing an elegant means of controlling the ionic cluster size, the strategic approach of using CNT both as an anchoring backbone for -SO(3)H groups to enrich proton conductivity and as a blending agent to improve the mechanical characteristics of the Nafion phase might be helpful in alleviating many critical problems associated with the use of commercial Nafion membranes.</p>1 aKannan, Ramaiyan1 aParthasarathy, Meera1 aMaraveedu, Sreekuttan, U.1 aKurungot, Sreekumar1 aPillai, Vijayamohanan, K.  uhttps://library.ncl.res.in/content/domain-size-manipulation-perflouorinated-polymer-electrolytes-sulfonic-acid-functionalized-002367nas a2200217   4500008004100000022001400041245015500055210006900210260010200279300001200381490000800393520150000401653002301901653001201924653001101936653001301947653000901960100002501969700003001994856012502024       2009                        eng d  a0253-413400aImaging hydrogen oxidation activity of catalyst-coated perfluoro sulfonic acid-polymer electrolyte membranes using scanning electrochemical microscopy0 aImaging hydrogen oxidation activity of catalystcoated perfluoro   aC V RAMAN AVENUE, SADASHIVANAGAR, P B \#8005, BANGALORE 560 080, INDIAbINDIAN ACAD SCIENCEScSEP  a719-7250 v1213 a<p>Scanning Electrochemical Microscopy (SECM) is a unique technique for studying fast heterogeneous kinetics and to map reactivity gradients along the surface of an electrocatalyst, especially when it involves multiple surface sites of varying reactivity. It combines the dual advantages offered by ultramicroelectrode (UME) voltammetry in terms of reduced ohmic drop and insignificant double layer charging contribution with the advantages of imaging by rastering the UME across an electro-active surface. In this work, we demonstrate these distinctive features of SECM in evaluating reactivity gradients on catalyst (Pt/C) coated NafionA (R) films towards hydrogen oxidation activity, a reaction of immense technological relevance. Imaging has been performed in the feedback mode by allowing H(2) evolution at the tip (25 A mu m Pt UME), which is reoxidized at the substrate electrode containing Pt/C-Nafion film. Interesting distribution in H(2) oxidation activity has been observed as a function of potential applied to the Pt/C-Nafion film. In addition, a plot of normalized tip current versus the substrate electrode potential indicates the effect of potential-induced reactivity change in the catalyst-coated membranes. The results of the present investigation are believed to be useful to H(2)/O(2) PEM fuel cells with respect to evaluating reactivity gradients of catalyst-coated polymer electrolyte membranes, which is important to rectify problems related to catalyst utilization.</p>10ahydrogen oxidation10aImaging10aNafion10aplatinum10aSECM1 aParthasarathy, Meera1 aPillai, Vijayamohanan, K.  uhttps://library.ncl.res.in/content/imaging-hydrogen-oxidation-activity-catalyst-coated-perfluoro-sulfonic-acid-polymer-001595nas a2200181   4500008004100000022001400041245014400055210006900199260011000268300001400378490000700392520078800399100002501187700002101212700002401233700003001257856012601287       2010                        eng d  a0959-942800aBio-inspired catalyst compositions for enhanced oxygen reduction using nanostructured Pt electrocatalysts in polymer electrolyte fuel cells0 aBioinspired catalyst compositions for enhanced oxygen reduction   aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcSEP  a9651-96570 v203 a<p>Composites of Nafion with a class of bio-molecules viz., plant hormones, are explored as potential polymer electrolytes for improving the proton transport inside the catalyst layer of a H(2)/O(2) fuel cell. Specifically, four nitrogenous plant hormones, two each from the class of auxins and cytokinins have been investigated, following preliminary characterization of the composite dispersions and membranes. Interestingly, the use of indole-3-acetic acid (an auxin) in the catalyst layer reveals a 30% enhancement in Pt catalyst utilization and improved fuel cell performance by 150 mW cm(-2). The effect of these bio-molecules on the kinetic and mass transport parameters has been analyzed systematically using a combination of electrochemical and spectroscopic techniques.</p>1 aParthasarathy, Meera1 aKannan, Ramaiyan1 aSreekumar, Kurungot1 aPillai, Vijayamohanan, K.  uhttps://library.ncl.res.in/content/bio-inspired-catalyst-compositions-enhanced-oxygen-reduction-using-nanostructured-pt-002255nas a2200265   4500008004100000022001400041245013400055210006900189260009500258300001200353490000800365520121200373653002101585653002401606653003501630653001901665653002301684100002501707700002401732700002801756700002501784700002601809700003001835856012401865       2011                        eng d  a0003-269700aCarbon nanotube-modified sodium dodecyl sulfate-polyacrylamide gel electrophoresis for molecular weight determination of proteins0 aCarbon nanotubemodified sodium dodecyl sulfatepolyacrylamide gel  a525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USAbACADEMIC PRESS INC ELSEVIER SCIENCEcFEB  a230-2350 v4093 a<p>The effect of incorporating carbon nanotubes (CNTs) in the gel matrix on the electrophoretic mobility of proteins based on their molecular weight differences was investigated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). More specifically, a reduction in standard deviation in the molecular weight calibration plots by 55% in the case of multiwalled carbon nanotubes (MWCNTs) and by 34% in the case of single-walled carbon nanotubes (SWCNTs) compared with that of pristine polyacrylamide gels was achieved after incorporating an insignificant amount of functionalized CNTs into the gel matrix. A mechanism based on a more uniform pore size distribution in CNT modified polyacrylamide gel matrix is proposed. Furthermore, the impact of SWCNTs and MWCNTs on the mobility of proteins in different molecular weight regimes at a given acrylamide concentration offers a tunable gel matrix in terms of the selection of molecular weight ranges of proteins. The robustness and excellent reproducibility of the CNT-PAGE protocol are expected to have a significant impact on the molecular weight determination of newly isolated proteins. (C) 2010 Elsevier Inc. All rights reserved.</p>10aCarbon nanotubes10aGel electrophoresis10aMolecular weight determination10aPolyacrylamide10aProtein separation1 aParthasarathy, Meera1 aDebgupta, Joyashish1 aKakade, Bhalchandra, A.1 aAnsary, Abu, Ayoobul1 aKhan, Mohammad, Islam1 aPillai, Vijayamohanan, K.  uhttps://library.ncl.res.in/content/carbon-nanotube-modified-sodium-dodecyl-sulfate-polyacrylamide-gel-electrophoresis-0