Direct electrochemistry of cytochrome c at a glassy carbon electrode covered with a microporous alumina membrane

Abstract

Electrochemistry of cytochrome c in a γ-alumina membrane with pierced micropores (diameter: 0.15 and 0.03 μm) has been examined. Reversible electrochemical reaction was observed at glassy carbon electrodes covered with either γ-alumina membrane. A slightly positively charged γ-alumina wall was considered to be effective on such an orientation of cytochrome c that enabled easy electron exchange at the γ-alumina wall/solution interface near the electrode surface. In the micropores, it was observed that cytochrome c was concentrated owing to monolayer adsorption onto the alumina wall. Macroscopically, a linear diffusion model was applicable to the present system. Thus, the γ-alumina membrane was confirmed to act as a “solid-state” promoter in the electrochemical reaction of cytochrome c. Microscopic treatment suggested that the diffusion mechanism of cytochrome c on the alumina wall is not electron hopping but physical displacement.