Probing adsorptive/desorptive redox processes and detection of cysteine: A voltammetric and scanning electrochemical microscopy study

Abstract

Electrochemical investigation of cysteine (CySH) was carried out using gold nano particles (AuNPs) modified glassy carbon electrode. Gold nano particles were electrochemically deposited over the glassy carbon electrode surface using potentiostatic deposition procedure. CySH was found to have good electrochemical activity over the AuNPs modified electrode surface which is otherwise inactive over the bare glassy carbon electrode surface. Electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) measurements were carried out to evident the adsorption/desorption behaviour of CySH and the transport of charge through the adsorbed disulphide, the dimeric oxidation product formed after the electrochemical oxidation. The positive feedback response in the probe approach curve in SECM measurements, after adsorption of the dimeric oxidation product indicated favourable transport of charge through the adsorbed layer for the oxidation of ferrocyanide. Analytical methods were developed based on the voltammetric and chrponoamperometric procedure for the determination of cysteine using the modified electrode, the detection sensitivity and detection limits of 0.03A/M and 74nM were obtained.