S. Aravamuthan

Bio: S. Aravamuthan is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Flow battery & Redox. The author has an hindex of 2, co-authored 5 publications receiving 16 citations.

Electrochemical Behaviour of 2,3′-Dinitrobenzidine in N,N-Dimethylformamide

Abstract: The electrochemical reduction of 2,3′-dinitrobenzidine (I) has been investigated in N,N-dimethylformamide solutions. Three diffusion-controlled polarographic waves were obtained. The first wave is due to a reversible single electron-transfer while the second and third waves result from irreversible processes involving one and two electron-transfers, respectively. The radical anion formed in the first step of reduction was confirmed by ESR technique. The red colour compound formed due to “ion association” after the second electron-transfer step gives rise to a polarographic “minimum” and a “dip” in the chronopotentiogram in addition to the new “peak clusters” seen in cyclic voltammograms. A mechanism is suggested for the reduction of I leading to the formation of 2,3′-dinitrosobenzidine.

Toward High Energy Density Redox Targeting Flow Batteries with a Mushroom-Derived Electrolyte

Abstract: Among several types of redox flow batteries (RFBs) under development, non-aqueous redox flow batteries (NRFBs) have the potential to approach the energy density of lithium-ion batteries, while maintaining the advantages of flow systems, including ability to decouple power and energy ratings, and thermal stability. Despite their promise, NRFBs suffer from low energy densities because the solubility limitation of redox species in non-aqueous solvents remains relatively lower compared to water. One promising concept for drastically improving the energy density of NRFBs is the utilization of solid charge storage materials, which are reversibly oxidized or reduced in the electrolyte tanks upon interaction with the redox active species (mediators) dissolved in electrolyte (i.e., redox targeting flow battery (RTFB)). Herein, we demonstrate a RTFB using a highly stable, bio-inspired mediator, vanadium(IV/V)bis-hydroxyiminodiacetate (VBH), coupled with cobalt hexacyanoferrate (CoHCF) as the solid charge storage material. Based on the charge/discharge cycling experiments, the energy capacity was found to enhance by ~5x when CoHCF pellets were added into the tank compared to the case without CoHCF. With the pellet approach, up to the ~70% of the theoretical capacity of CoHCF were utilized at 10 mA cmȡ2 current density. Sufficient evidence has indicated that this concept utilizing redox targeting reactions makes it possible to surpass the solubility limitations of the active material, allowing for unprecedented improvements to the energy density of RFBs.

Electrochemical reduction of 2,3'-dinitrobenzidine in buffered aqueous methanol

Abstract: 2,2′-dinitrobenzidine (2,3′-DNB) gives a single diffusion-limited irreversible polarographic wave in buffered aqueous methanol. Microcoulometric experiments indicate a transfer of ten electrons in the reduction and cyclic voltammetric studies show direct proof for the existence of a nitroso intermediate. Based on the results obtained, a suitable mechanism is proposed for the reduction of 2,3′-DNB in buffered methanolic solutions.

Determination of ionisation constants of nitrobenzidines

Abstract: The ionisation constants of 2-nitrobenzidine, 2,2’-dinitrobenzidine and 2,3’-dinitrobenzidine were determined spectrophotometrically in 33-3% (w/w) methanol. The low pK value obtained for 2,3’-dinitrobenzidine when compared to that of 2-nitro and 2,2’-dinitrobenzidines is explained on the basis of electron withdrawing nature of the nitrogroup and intramolecular hydrogen bonding.

Application of a Potentiometric System with Data-Analysis Computer Programs to the Quantification of Metal-Chelating Activity of Two Natural Antioxidants:Caffeic Acid and Ferulic Acid

Abstract: The quantification of metal-chelating activity of caffeic and ferulic acids( 1 and 2, resp.) was successfully performed by using a potentiometric system with data-analysis computer programs. The method was applied to two phenolic models, which have been systematically reported as antioxidants. Although a chain-breaking mechanism was proposed, several studies pointed out the possibility of complexation of transition metals that can participate in single-electron reactions and mediate the formation of oxygen-derived free radicals. In this work, the complexation propertiestowardsCu II were investigated by potentiometry with a glass electrode. Acidity constants of the ligands (phenolic acids) and the formation constants of the ligandmetal complexes were evaluated by potentiometry. The modeling of the titration curvesand the data treatment were performed with the computer programsSuperquad and Bes t. A detailed quantitative examination of the complexation species formed in the Cu II /caffeic acid (1) and Cu II /ferulic acid (2) systems is presented together with the formation constants (log ). Results have shown that the complexation properties of the two phenolic acids towardsthe trans ition metal are quite different: the activity of caffeic acid ( 1) wasfound higher than that of ferulic acid (2). The data are important to get insight into the mechanism of action of antioxidants, and, in this case, could partially explain the efficacy of caffeic acid in the protection of LDL oxidative damage. In addition, the analytical method developed could be applied to quantify the chelating activity of important biological compounds, such as allopurinol, uric acid, cinnamic acids, flavonoids, and anthocianins, and, in that way, could be a valuable tool to understand the mechanisms underlying their protective effects.

Current Oscillatory Phenomena Based on Redox Reactions at a Hanging Mercury Drop Electrode (HMDE) in Dimethyl Sulfoxide

Abstract: A systematic and comprehensive study on cyclic voltammetric anodic current oscillation (CVACO) at a hanging mercury drop electrode (HMDE) was carried out for the redox reactions of molecular oxygen (O2), nitrobenzene (NB), 1,4-dinitrobenzene (DNB), benzoquinone (BQ), 2,3,5,6-tetramethylbenzoquinone (TMBQ), benzophenone (BP), azobenzene (AB), 2,1,3-benzothiadiazole (BTD), 7,7,8,8-tetracyanoquinodimethane (TCNQ), methyl viologen dichloride (MV2+), and tris(2,2‘-bipyridine)ruthenium(II) dichloride [Ru(bpy)32+] in dimethyl sulfoxide (DMSO) solutions containing 0.1 M tetraethylammonium perchlorate (TEAP). From the electrocapillary curve (ECC) obtained using a dropping mercury electrode as well as the capacitance versus potential curves measured using electrochemical impedance technique, the value of the potential of zero charge (PZC) was estimated to be −0.27 V versus Ag|AgCl|NaCl (sat.) in a DMSO solution containing 0.1 M TEAP. CVACO was found to occur only for the redox couples (i.e., BP0/BP•-, O20/O2•-, AB0...

Nonlinear phenomena at mercury Hg electrode/room-temperature ionic liquid (RTIL) interfaces: polarographic streaming maxima and current oscillation.

Abstract: The polarographic streaming maxima and cyclic voltammetric anodic current oscillation (CVACO) at a hanging mercury drop electrode (HMDE) in room-temperature ionic liquid (RTIL) have been studied for the first time using cyclic voltammetric, potential step chronoamperometric and pulse voltammetric techniques. The reversible redox reaction of the 2,1,3-benzothiadiazole (BTD)/BTD•- (an anion radical of BTD) couple with a formal potential (E0‘) of −1.36 V versus Ag/AgCl/NaCl(saturated) in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) RTIL was typically employed for this purpose. A maximum was observed at the rising part of the normal pulse voltammogram for the reduction of BTD to BTD•- as well as of the reversed pulse voltammogram for the reoxidation of BTD•- to BTD at the HMDE. The conditions of the initiation and control of the CVACO at the HMDE in EMIBF4 were extensively investigated. Generally, the CVACO was enhanced by increasing the concentration of BTD at a given potential scan rate (υ) and wa...