CHEMICAL MODIFICATION OF PLATINUM AND GOLD ELECTRODES BY NAPHTHOQUINONES USING AMINES CONTAINING SULFHYDRYL OR DISULFIDE GROUPS

To develop a photobioelectrode on the basis of bacterial photosynthetic reaction centres, the modification of Pt and Au electrodes by naphthoquinones as electron transfer mediators has been studied. Cysteamine and cystamine were used as bifunctional spacers. Thiol and disulphide groups of these molecules are anchors at the surface of the metallic electrodes, whereas the amino groups bind naphthoquinones covalently in the form of their amino derivatives. The stability and electrochemical reversibility (the rate constant of the redox process is ca. 10 s-1) are shown to be increased considerably as compared with similar electrodes where aminosilane is used as a bifunctional spacer. The immobilization processes of sulphur-containing amino compounds are found to be reversible. This allows a covalently bound quinone to be displaced easily by the excess of thiolic compound and then a new naphthoquinone is immobilized with another redox potential. It has been shown that the length of the spacer between the immobilized quinone and the metallic surface can be increased due to carbodiimide coupling of the carboxyl group of the amino acid-quinone derivative with the amino group of the immobilized thiolic compound. © 1990.