Amperometric sensor for hydrogen peroxide based on immobilized cytochrome c on binary self-assembled monolayers.

A sensitive sensor for the determination of hydrogen peroxide (H(2)O(2)) was fabricated by immobilizing cytochrome c (cyt c) on binary self-assembled monolayers (SAMs) of 5-(1,2-dithiolan-3-yl)valeric acid (thioctic acid, T-COOH) and 5-(1,2-dithiolan-3-yl)valeramide (thioctic acid amide, T-NH(2)) on gold electrodes. The electrochemical characteristics of immobilized cyt c were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry. The modified electrode showed good electrocatalytic activity towards the reduction of H(2)O(2). The catalytic current is linear with the H(2)O(2) concentration ranging from 10.0 to 300 microM with a correlation coefficient of 0.9996. The apparent Michaelis-Menten constant (K(m)(app)) was found to be 619 microM. The sensor achieved 95% of the steady-state current within 10 s, exhibiting high sensitivity (1.7 nA microM(-1) cm(-2)).