Yeast-TiO2 interfacial complexation enabling ligand-to-metal charge transfer-driven photocatalysis under visible light

Although yeast has often been employed as a target pollutant or structural bio-template in TiO 2 -based photocatalysis, its application as a ligand-to-metal charge transfer (LMCT) sensitizer remains largely unexplored. Here, we demonstrate that coupling yeast with TiO 2 forms a surface complex that enables efficient photocatalysis under visible light irradiation (λ > 420 nm). Spectroscopic analysis verified the interfacial binding of yeast to TiO 2 , leading to a red-shifted absorption edge and enhanced photoresponse in the visible region. Photoelectrochemical measurements implied that the yeast-TiO 2 complex promotes efficient interfacial electron transfer with low charge-transfer resistance under visible light excitation. The yeast-TiO 2 complex exhibited high activity for the reduction of Cr(VI) to Cr(III), whereas fluorinated TiO 2 surfaces suppressed this process by preventing complex formation. Thermal treatment at 80 °C also diminished the photocatalytic activity, consistent with yeast degradation and the resulting loss of LMCT functionality. Systematic variation of key parameters, including yeast loading, irradiation wavelength, and reaction pH, revealed their critical influence on photocatalytic performance. Repeated Cr(VI) reduction tests showed that the activity loss of the yeast-TiO 2 complex under visible light arises from surface fouling by reaction by-products rather than yeast degradation, while replenishing yeast every cycle restores LMCT-mediated photocatalysis. This work represents the first demonstration of yeast as an LMCT sensitizer, establishing a new bio-derived strategy for designing visible light-active photocatalytic systems.