Osmium redox polymer film electrode and its electrocatalytic properties towards the oxidation of epinephrine: Electrochemical quartz-crystal microbalance and voltametric characterization

摘要

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 pen-nits 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 x 10(-7) to 1 x 10(-4) mol l(-1). A detection limit of 1.5 x 10(-7) Mol l(-1) (S/N = 3) is obtained.