Semiconductor photocatalyst films protecting stone cultural relics against microbial weathering

Abstract Microorganisms can colonize stone surfaces and metabolize them to produce pigments and corrosive products, thus causing the weathering of stone cultural relics. Herein, we show that weathering caused by a representative microorganism ( Scenedesmus obliquus ) can be prevented by coating stone surfaces with films comprising a semiconducting photocatalytic nanocomposite, BiVO 4 /Ti 2 NT x -TiO 2 . The compositing of BiVO 4 (a narrow-bandgap semiconductor) with Ti 2 NT x -doped TiO 2 (a two-dimensional layered semiconductor) results in an extended visible light absorption range and reduced bandgap. The incorporation of Ti 2 NT x increases the efficiency of light energy utilization and reactive oxygen species ( • OH, • O 2 − ) yield by enhancing electron conductivity and enabling the rapid transfer of photogenerated electrons (Ti 2 NT x to BiVO 4 and TiO 2 ). The reactive oxygen species produced upon the irradiation of BiVO 4 /Ti 2 NT x -TiO 2 films with visible light selectively attack and kill harmful Cyanobacteria species, which feature a cyst-like structure composed of phospholipids and proteins, and the resulting release of intracellular nutrients promotes the growth of beneficial species ( Proteobacteria , Actinobacteria , Bacteroidota , and Patescibacteria ). Thus, this work paves the way for the protection of stone objects, including those classified as cultural heritage, and inspires the further development of semiconductor photocatalysts and their engineering applications.