Chlorophyll-modified Au₂₅(SR)₁₈-functionalized TiO₂ for photocatalytic degradation of rhodamine B

Abstract

Solar-driven photocatalysis is a promising route toward cleaner production using sunlight as a sustainable energy source. Nanocrystalline TiO2, in the form of mixed anatase/rutile phases (P25), is often employed, but must be modified for higher activity in visible light. To improve the light harvesting properties, nano-bio hybrid photocatalysts were prepared by functionalizing P25 with Au25 clusters, Au nanoparticles, and/or chlorophyll. The most effective photocatalytic degradation of rhodamine B (RhB) was observed over P25 catalysts functionalized with both Au25 and chlorophyll. HR-TEM, UV–vis, XPS and XANES/EXAFS were applied to examine the factors influencing photocatalytic activity. A direct contact between Au25, chlorophyll, and P25, strongly improved the electron transfer from chlorophyll to P25, while still maintaining the reusability of catalysts. For chlorophyll-modified Au25(SR)18-functionalized P25 catalyst, the degradation rate of RhB was enhanced ∼16 times compared to that of P25.