Catalytic capability of poly(malachite green) films based electrochemical sensor for oxidation of dopamine

Catalytic reaction mechanism and catalytic efficiency of electrochemical oxidation of dopamine on a poly(malachite green) film-coated glassy carbon electrode were investigated using cyclic voltammetry, bulk electrolysis, chronocoulometry, and chronoamperometry. Two electrons and two protons participated in the diffusion-controlled electrocatalytic oxidation of dopamine with a diffusion coefficient of 6.5 × 10−5 cm2 s−1 and a rate constant of 0.7 cm s−1. The rate-determining step of electrocatalytic oxidation of dopamine was the diffusion of dopamine inside the poly(malachite green) film. Catalytic efficiency as a quantitative parameter was proposed to demonstrate the catalytic ability of poly(malachite green) films towards dopamine and was expressed with the ratios of oxidation currents of dopamine on a poly(malachite green) film-coated glassy carbon electrode to those on a bare glassy carbon electrode. The catalytic efficiency of poly(malachite green) films towards dopamine to its thickness was estimated to be 1.11 mC−1. The effect of the concentration of dopamine, the thickness of poly(malachite green) films, and scan rates on catalytic efficiency was also studied.