M.V. Sangaranarayanan

The applicability of tin submicroparticles modified glassy carbon electrodes for sensing of nitrite ions is demonstrated. Tin submicroparticles have been electrodeposited on a glassy carbon electrode using constant potential deposition. The detection of nitrite ions is carried out with differential pulse voltammetry, amperometry and electrochemical impedance spectroscopy. The lowest detection limit of 0.5μM with a linear range of 5μM-1000μM is inferred from the differential pulse voltammetry. The interference from different compounds such as urea, glucose and nitrate ions is also analyzed.

The efficacy of silver-deposited glassy carbon electrode for the determination of lead ions at the sub-nanomolar concentration ranges is investigated. The silver nanoparticles are electrodeposited on glassy carbon electrode using chronoamperometry and the electrode surface is characterized using SEM. Lead ions are detected in the region of underpotential deposition. The analysis is performed in square wave mode in the stripping voltammetry without the removal of oxygen. The detection limit of 10 pM has been obtained with a constant potential of -0.7 V during the electrodeposition step for a period of 50 s. The interference of surfactants in the detection of lead ions is also studied. © 2011 Elsevier B.V. All rights reserved.

The progress in the field of electrochemical supercapacitors employing polyaniline and polypyrrole during the past decade is reviewed, with special emphasis on electrochemical characterization techniques. The magnitude of the specific capacitance from the galvanostatic charge-discharge studies, cyclic voltammetry and impedance spectroscopy has been compiled. The merit of the Electrochemical Impedance Spectroscopy in deducing the system parameters is pointed out. The unsolved issues pertaining to the conducting polymers based supercapacitors are highlighted. © 2012 Elsevier Ltd.

Silver polygonal nanostructures are prepared via constant potential electrodeposition on Indium Tin Oxide electrodes without employing any templates or surfactants. The Scanning Electron Microscopy (SEM) and Tunneling Electron Microscopy (TEM) images reveal the presence of polygons of various distinct shapes which are formed at the same deposition potential. As the potential becomes more negative, silver dendrites are observed, irrespective of the concentration of the precursor. The Selected Area Electron Diffraction (SAED) spot patterns indicate that all the polygonal nanostructures are predominantly bounded by a (111) plane while the X-ray diffraction studies confirm the Face Centered Cubic structure of silver deposits. The mechanism of formation of polygonal nanostructures is elucidated using the Volmer-Weber growth model. © 2013 The Royal Society of Chemistry.

Silver dendritic structures have been prepared using constant potential deposition on indium tin oxide (ITO) electrodes from an aqueous solution of AgNO3 and KNO3 without any surfactants or structure directing agents. The applied potential is shown to be a crucial factor in the formation of dendrites. Depending upon the magnitude of the applied potentials, morphologies vary from polygons to dendrites. The shape evolution of the silver dendrites has been investigated by varying the deposition time and metal precursors. The mechanism of formation of dendrites is interpreted using the diffusion limited aggregation (DLA) model. The fractal dimensions of the dendrites calculated using the box counting algorithm are in agreement with those predicted by the DLA model. The Ag dendrites coated ITO electrodes exhibit excellent electrocatalytic activity toward oxidation of hydrazine in alkaline medium. The sensing of hydrazine is carried out with amperometry, where from the limit of detection and linear calibration range is deduced as 0.5 μM and 100-1700 μM respectively. The effect of ascorbic acid, urea, ethanol, glucose, K+, Cl-, Br- and I- ions as possible interfering agents in the detection of hydrazine is analyzed.

The use of boric acid as the structure-directing agent and supporting electrolyte is shown to lead to a simple and robust strategy of obtaining hierarchical three dimensional cobalt dendrites, flower-like crystals and microspheres on stainless steel (SS) surfaces at room temperature. The phase and morphology of the dendrites are studied using Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and Energy Dispersive X-ray analysis (EDAX). The pre-dominant occurrence of cobalt(111) plane is noticed from XRD data while the magnetization studies using Vibrating Sample Magnetometer (VSM) provides a high coercivity value of ∼574.6 Oe for cobalt dendrimers. The mechanism of formation of dendrimers is discussed using the classical Diffusion-Limited Aggregation (DLA) model. © 2012 Elsevier B.V. All rights reserved.