Assembly and Characterization of Zinc Porphyrin−Hydrogenase−(Poly)Viologen Triads on Substrate Surfaces

Abstract

Two kinds of light-sensitive, electro- and enzyme-active electrodes modified by zinc porphyrins, hydrogenase, and viologen triad multilayers have been constructed. The first zinc porphyrin or viologen layer was covalently immobilized on the substrate surfaces, with the consecutive layers of hydrogenase and polyviologen or positively charged porphyrin adsorbed electrostatically. The multilayers assembled were characterized by using X-ray photoelectron, UV−vis absorption, and fluorescence spectroscopy. Electrochemical studies for the zinc porphyrin modified electrode showed a couple of redox waves centered at about −0.48 V vs Ag/AgCl, which was attributed to a bielectronic process of porphyrin. When the first layer was a viologen derivative (VIO), two couples of redox waves were recorded and centered at about −0.40 and −0.86 V, which were attributed to one-electron processes of VIO 2+ ↔ VIO +• and VIO +• ↔ VIO 0, respectively. The hydrogenase activity remained in the multilayers. It is suggested that the as-prepared zinc porphyrin−hydrogenase−(poly)viologen triad multilayers can be used for the studies on the photoinduced electron transfer, hydrogen biosensors, and biohydrogen evolution.