Electrochemical studies of cytochrome c on gold electrodes with promotor of humic acid and 4-aminothiophenol

p-Aminothiophenol ( PATP) and humic acids (HA or HAs) were applied jointly as the electron transfer accelerants of redox reactions of cytochrome c (Cyt c) on gold electrodes. The electrochemical properties of the modified electrodes were studied by field emission scanning electron microscope, ultraviolet-visible spectroscopy, electrochemical impedance spectroscopy, Raman spectroscopy and cyclic voltammetry. The immobilized Cyt c displayed a couple of stable and well-defined redox peaks with a formal potential of - 0.101V ( vs. SCE) in pH 7.0 phosphate buffer solution. Cyt c adsorption is in the form of a monolayer with average surface coverage of 5.28 pmol cm(-2). The electron transfer rate constant was calculated to be 2.14 s(-1). It indicate that the HA film acted as a good adsorption matrix for Cyt c and an excellent accelerant for the redox of Cyt c. The Cyt c-HA modified gold electrode showed a new couple of well-marked redox peaks when 2,4-dichlorophenol was added to the test solution.