Papers by Vedagiri Lakshminarayanan
Journal of Electroanalytical Chemistry, 1994
ABSTRACT
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1991
A two-parameter (potential V,, and time constant r) potential controlled relaxation technique is ... more A two-parameter (potential V,, and time constant r) potential controlled relaxation technique is described in this paper. The method consists in applying an exponentially increasing potential input &(I-exp(-t/T)) to the system under activation control and measuring the current-time response. The shape of the current-time transient changes in an interesting manner when r is varied. A theoretical analysis of the transient has been carried out and it is shown that the method can be applied for the measurement of kinetic parameters of electrochemical reactions. The utility of the method for the measurement of polarisation resistance and double layer capacitance of corrosion systems is demonstrated in this paper. The method is applicable only to systems with slow electron transfer where mass transfer effects can be neglected. This, and the problem of eliminating noise in systems with low corrosion rate, are the two chief limitations of this technique.
Fuel, 2015
h i g h l i g h t s Ultra-low, binder free casting of Pt based nano-ink for fuel electrooxidation... more h i g h l i g h t s Ultra-low, binder free casting of Pt based nano-ink for fuel electrooxidation. Electrooxidation of industrial by-product such as glycerol and ethylene glycol. Catalyst has shown 33 fold increased current density than commercial Pt on carbon. Low onset potentials and high current densities for a facile electrooxidation. Synergy between platinum nanoparticles & carbon nanotubes during electrooxidation.
Thin Solid Films, 2014
ABSTRACT The present study is an attempt to understand the properties of an interesting self-asse... more ABSTRACT The present study is an attempt to understand the properties of an interesting self-assembled monolayer system composed of inclusion complexes of thiocholesterol and cyclodextrins. Cyclodextrins were used as host compound while thiocholesterol was used as the entrant molecule into the cavity of cyclodextrins. The improved electron transfer barrier property towards a redox couple indicates a sturdy inclusion complex monolayer. A very large R-ct value, 64.6 k Omega.cm(2) for a redox system was obtained in the case of methyl-beta-cyclodextrin and thiocholesterol inclusion complex self-assembledmonolayer. A rather low value of capacitance 1.2 mu F cm(-2) measured in supporting electrolyte further signifies the fact that inclusion complex monolayer is quite impermeable for ionic species. In addition lateral force microscopy combined with force-distance analysis revealed the presence of an interesting mixed hydrophilic/hydrophobic surface.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2004
... References. 1. MM Nayak, N. Gunasekaran, AE Muthunayagam, K. Rajanna and S. Mohan. Measuremen... more ... References. 1. MM Nayak, N. Gunasekaran, AE Muthunayagam, K. Rajanna and S. Mohan. Measurement Sci. Technol. 4 (1993), p. 1319. 2. JL Menendez, P. Caro and A. Cebollada. J. Cryst. Growth 192 (1998), p. 164. Abstract ...
Materials Research Bulletin, 2014
Langmuir, 2008
We have synthesized for the first time thiol-monolayer-protected gold nanoparticles (MPCs) by the... more We have synthesized for the first time thiol-monolayer-protected gold nanoparticles (MPCs) by the process of electrochemical dissolution of gold in an ethanol-water mixture. The MPCs have been formed both with and without NaBH 4 as a reducing agent. The well-dispersed thiol-capped MPCs were characterized by UV-visible absorption and transmission electron microscopy (TEM) studies.
Langmuir, 2007
We have studied the electron-transfer properties of some redox systems on a gold electrode in a l... more We have studied the electron-transfer properties of some redox systems on a gold electrode in a lyotropic hexagonal columnar liquid crystalline phase (H1 phase) using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The liquid crystalline medium consists of the nonionic surfactant Triton X-100 and water. The redox reactions that have been studied are ferrocene/ferricenium, [Fe(CN) 6 ] 3-/4-, and [Ru(NH 3) 6 ] 3+/2+. We have confirmed by polarizing optical microscopy that the liquid crystalline nature of the medium is maintained even after the addition of the redox species and the supporting electrolyte. The CV studies show a significant shift in the half-peak potentials of these redox reactions in the liquid crystalline medium. From the EIS studies, we have measured the diffusion coefficients and the kinetic parameters for the redox species. These results are discussed and compared with the values obtained in the conventional solvent medium. The CV and impedance studies demonstrate that the hexagonal columnar phase provides a novel controlled environment for the study of electron-transfer reactions in biological and physiological media.
Journal of Colloid and Interface Science, 2002
The highly hydrophobic neat alkanethiol-coated SAM on evaporated gold shows an unusually low inte... more The highly hydrophobic neat alkanethiol-coated SAM on evaporated gold shows an unusually low interfacial capacitance in aqueous media. This result cannot be explained by a simple parallel plate model of the double layer with the alkanethiol monolayer as a sole dielectric separator. Interestingly, a hydrophilic SAM prepared from a neat hydroxy thiol does not show any such capacitance lowering in aqueous media. Our results suggest the existence of a "hydrophobic gap" between the alkanethiol SAM-water interface. Such a model is also very much consistent with the predictions of Lum, Chandler, and Weeks theory of length scale dependent hydrophobicity.
Journal of Colloid and Interface Science, 2003
We have studied the orientation and barrier properties of self-assembled monolayers (SAMs) of two... more We have studied the orientation and barrier properties of self-assembled monolayers (SAMs) of two alkanedithiols, hexanedithiol, octanedithiol, and an aromatic dithiol, 1,4-benzene dimethanethiol (BDMT), on gold in acetonitrile. From our studies, we conclude that BDMT molecules can form more organized monolayers on gold than aliphatic dithiol SAMs due to extremely strong lateral van der Waals interaction among the phenyl rings in the former. A study of the adsorption kinetics of octanedithiol in ethanol indicates that the adsorption rate law is concentration dependent just as for alkanethiols. However, the rate of adsorption is considerably faster than for simple alkanethiols.
Electrochimica Acta, 2000
The growth kinetics of self assembled monolayer of alkanethiols of different chain lengths and co... more The growth kinetics of self assembled monolayer of alkanethiols of different chain lengths and concentrations on an evaporated gold surface on mica has been studied in situ and in real time using electrochemical impedance spectroscopy. The interfacial capacitance obtained from the measurement of the imaginary component of impedance is used to calculate the surface coverage as a function of time. From this data, rate constants of adsorption of alkanethiols have been measured in 0.1 M LiClO 4 in ethanol solution. The results show that the adsorption follows Langmuir kinetics at higher thiol concentration of 20 mM and partial diffusion controlled kinetics at 5 mM and lower. The adsorption at a concentration of 1 mM is so rapid that 40% of the full monolayer is covered within the first 500 ms.
Corrosion Science, 2002
We have studied the adsorption properties and the eect of some azoles such as benzotriazole (BTA)... more We have studied the adsorption properties and the eect of some azoles such as benzotriazole (BTA), mercaptobenzothiazole (MBT), benzimidazole (BIMD), mercaptobenzimidazole (MBIMD), imidazole (IMD) and tetrazole on the growth of oxide ®lm on copper in 0.1 M NaOH. Cyclic voltammetry and electrochemical impedance spectroscopy are used to characterise the passivation process. The relative inhibition eciencies of the azoles in controlling the oxide ®lm formation is found to be in the order MBT > BIMD % MBIMD > BTA % IMD. We ®nd that the azoles follow the Langmuir adsorption isotherm. Study of coverage by the measurement of capacitance obtained from the imaginary component of impedance Z HH as a function of time indicates that in about 800 s more than 95% of the coverage is complete in all the cases of inhibitor adsorption.
Catalysis Letters, 2014
ABSTRACT The present study describes the outcome of the electrocatalysis of small organic molecul... more ABSTRACT The present study describes the outcome of the electrocatalysis of small organic molecules methanol, ethanol and formic acid on palladium nanodendritic film on graphite electrode. Higher oxidation currents than commercial Pd/C catalyst and low activation energies are obtained for electro-oxidation of organic molecules, indicating that the nanodendrites are highly effective for the electro-oxidation of these molecules. The nanocomposite film is effective in alkaline medium for alcohols oxidation, and in acidic media for formic acid oxidation.
Applied Catalysis B: Environmental, 2012
The study attempts to compare the electrocatalytic effect of gold nanoparticles dispersed conjuga... more The study attempts to compare the electrocatalytic effect of gold nanoparticles dispersed conjugated polymers using activation energy, Tafel slopes and reaction orders for the evaluation of their performance. A simple and rapid in situ chemical and electrochemical method was adopted for the synthesis of gold and different conducting polymers nanocomposites on electrode surfaces. The method involves the polymerization of the monomer to yield the polymer nanocomposite film with dispersed gold nanoparticles. Polyaniline, polypyrrole, polythiophene and poly(3,4-ethylenedioxythiophene) are the four polymers studied in this work. A systematic comparison among the nanocomposites reveals that although all the conducting polymers have good catalytic activity in alkaline medium however polyaniline dispersed with gold nanoparticles has the best catalytic properties among them as evidenced by its very low activation energy, low onset potential and reproducible currents.
The Journal of Physical Chemistry B, 2009
Proceedings / Indian Academy of Sciences, 1986
Investigations on the use of an exponential relaxation technique for studying corrosion systems a... more Investigations on the use of an exponential relaxation technique for studying corrosion systems are reported. It is shown that the polarisation resistance and the double layer capacitance of corrosion systems can be obtained by the small amplitude exponential relaxation technique (SAERT). It is demonstrated, that the rate of corrosion can be measured by the large amplitude exponential relaxation technique (LAERT). This technique yields 'accelerated Tafel plot' only when the charging current is negligible, which is seldom so. Methods for correcting for double layer charging are described. Double layer capacitance as a function of potential is obtained from LAERT. Therefore it can be used for studies on inhibitors. The utility of LAERT for corrosion systems with only one of the conjugate reactions under activation control is established. The effect of series resistance (Re) is discussed and an in situ method for its determination is described. A procedure for correcting the experimental data for errors due to Re is given.
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1986
Application d'une methode electrochimique d'analyse a la determination des vitesses de co... more Application d'une methode electrochimique d'analyse a la determination des vitesses de corrosion de l'acier doux et du fer Armco en milieux de H 2 SO 4 , HCl et NaCl
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Papers by Vedagiri Lakshminarayanan