Visible-Light-Driven Enzymatic Reaction of Peroxidase Adsorbed on Doped Hematite Thin Films

The present study proposes a novel technique to control a catalytic activity of redox enzyme (horseradish peroxidase; HRP) bound to n-type oxide semiconductor by photoirradiation. The resting HRP is transformed into activated state as a result of oxidation with holes generated in valence band of the irradiated oxide semiconductor. Subsequently, the activated HRP leads to the enzymatic conversion of organic substrates accompanied by two-electron reduction to regenerate the resting state. Because the HRP is supported with a narrow band gap semiconductor (Pt-doped α-Fe₂O₃ thin film), which is prepared by means of photoelectroless deposition, gentle energy of visible light is sufficient to trigger the reaction cycle. Accordingly, the enzymatic reaction continues for longer duration than related systems operated by ultraviolet light accounting for photodenaturation of HRP. The reaction rate depends on wavelength and intensity of the incident light and intermittent light irradiation causes a clear photoswitching behavior. At the beginning, we present the formation of Pt-doped α-Fe₂O₃ thin films via the photoelectroless deposition, and then the mechanism and advantages of the proposed reaction system are clarified in detail.