Electrochemical detection of L-cysteine using a glassy carbon electrode modified with a two-dimensional composite prepared from platinum and Fe3O4 nanoparticles on reduced graphene oxide

We report on an electrochemical sensor for L-cysteine that consists of a glassy carbon electrode modified with a two-dimensional ternary nanocomposite prepared from platinum, magnetite, and reduced graphene oxide (referred to as Pt-Fe3O4/rGO). It was prepared by a solvothermal method and characterized by X-ray powder diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Electrochemical detection processes were investigated by cyclic voltammetry, amperometry, double potential step chronoamperometry and differential pulse voltammetry. The diffusion coefficient (7.41 x 10(-7) cm(2) s(-1)) and reaction rate constant (9.96 x 10(7) cm(3) mol(-1) s(-1)) were calculated via the Cottrell equation. The sensor, best operated in 0.1 M NaOH solution at a working voltage of 0.65 V vs. SCE, has a 10 mu M detection limit and an analytical range that extends from 0.10 to 1.0 mM. The method is acceptably selective, stable, repeatable and reproducible due to the synergistic effect of the various components applied. The detection limit is 1.0 x 10(-5) M.