Electrocatalytic Activity of Electropolymerized Meldola's Blue toward Oxidation of Dopamine

Abstract

To understand the kinetics of charge transfer from chemically modified electrodes to solution species, the authors have investigated the influence of poly (Meldola’s blue) on the kinetic parameters of dopamine oxidation by rotating disc electrode voltammetry. The polymer film fixed on electrode surfaces raised the dopamine peak current by a factor of 10 in a 0.1 mM solution; this electrocatalytic effect enables one to detect dopamine at concentrations of the order of 5 µM. The polymer film increased the standard heterogeneous rate constant of dopamine oxidation more than 10-fold and favored a two-electron transfer step, thus raising the dependence of the kinetic current on the electrode potential. These effects were independent of electron self-exchange between redox-active sites in the film. They arose from the incorporation of dopamine with the polymer. This binding interaction decreased with protonation of the polymer, because of electrostatic repulsion between the positively charged species.