A very low potential electrochemical detection of l-cysteine based on a glassy carbon electrode modified with multi-walled carbon nanotubes/gold nanorods

A nanohybrid platform built with multi-walled carbon nanotubes and gold nanorods, prepared via a cationic surfactant-containing seed-mediated sequential growth process, in aqueous solution, on a glassy carbon substrate has been successfully developed to be used in the electrocatalytic oxidation of l-cysteine (Cys). The nanohybrid was characterized by transmission electron microscopy, Raman spectroscopy and electrochemical measurements. Cyclic voltammetry results had shown that the modified electrode allows the oxidation of Cys at a very low anodic potential (0.00 V vs. Ag/AgCl). The kinetic constant kcat for the catalytic oxidation of Cys was evaluated by chronoamperometry and provided a value of 5.6×104 L mol−1 s−1. The sensor presents a linear response range from 5.0 up to 200.0 µmol L−1, detection limit of 8.25 nmol L−1 and a sensitivity of 120 nA L µmol−1.