Osmium Redox Polymer Film Electrode and Its Electrocatalytic Properties towards the Oxidation of Epinephrine: Electrochemical Quartz-Crystal Microbalance and Voltametric Characterization

An osmium redox polymer PVI-PAA-dmeOs is electrodeposited onto a gold electrode by using repetitive double potential step chronoamperometry. The resulting film is permeable to the substrates and products of the catalyzed reaction, and permits fast electron transfer. The frequency variation during the potential step process is recorded using electrochemical quartz-crystal microbalance (EQCM). A reaction mechanism for electrochemical deposition of the osmium redox polymer is proposed. The characteristics of the PVI-PAA-dmeOs film are investigated by EQCM and cyclic voltametry. The results show the hydrated osmium PVI-PAA-dmeOs film to exhibit excellent electrocatalytic activity towards the oxidation of epinephrine. At a bare gold electrode, the epinephrine oxidation current increases greatly and the oxidation peak potential negatively shifts to about 0.16 V (Ag/AgCl) at the film-modified electrode. Under optimal conditions, amperometric measurements are performed at 0.18 V and the current response of epinephrine changes linearly with its concentration from 5 × 10^?7 to 1 × 10^?4 mol l^?1. A detection limit of 1.5 × 10^?7 mol l^?1 (S/N = 3) is obtained.