Combined quartz crystal impedance and electrochemical impedance measurements during adsorption of bovine serum albumin onto bare and cysteine- or thiophenol-modified gold electrodes

摘要

Combined piezoelectric quartz crystal (PQC) impedance and electrochemical impedance measurements as a novel technique were reported for monitoring adsorption of bovine serum albumin (BSA) onto bare and cysteine- or thiophenol-modified gold electrodes. Equivalent circuit parameters and resonant frequencies for PQC resonance as well as the electrical double layer capacitance were obtained and discussed. A scheme of two consecutive reactions occurring at the interface was used to analyze the adsorption kinetics, showing that the double layer capacitance is more sensitive to the re-arrangement of the adsorbed protein molecules compared with the resonant frequency. The standard heterogeneous rate constants of ferricyanide/ferrocyanide before and after the BSA adsorption were determined. Since the present technique provides not only electrochemical impedance information but also multidimensional piezoelectric information simultaneously, it is highly recommended for wider applications in electrochemical studies.