Photo-electro-chemical properties of TiO2 mediated by the enzyme glucose oxidase

Electrochemical measurements show that the enzyme glucose oxidase (GO) is adsorbed on the surface of TiO2 without apparently changing the flat band potential of the semiconductor, indicating that it does not cause a change of the energy of conduction band electrons. On the other hand, it is observed that GO markedly increases the efficiency of the two electron reduction of O-2 to H2O2 which is accumulated in the solution phase. ESR spin trapping investigations indicate that GO favors the formation of OH• radicals, due to either the inhibition of charge recombination processes or to H2O2 reduction by conduction band electrons. Accordingly, photo-oxidation of different alcohols to the corresponding radical species is also enhanced in the presence of GO. The photo-oxidation of 1,2-propandiol on TiO2/GO is regioselective in that (i) partial oxidation to hydroxyacetone is observed and (ii) no mineralization (full combustion to CO2) of the substrate occurs. These facts are of particular interest in the field of studies concerning the design of new photocatalytic systems with enhanced activity and controllable oxidative power