Characteristics, mechanisms and bacteria behavior of photocatalysis with a solid Z-scheme Ag/AgBr/g-C3N4 nanosheet in water disinfection

In this study, a series of Ag/AgBr/g-C3N4 nanosheet (CNNS) photocatalysts were prepared by a more environmental-friendly method. The prepared material was characterized and then applied in photocatalytic disinfection of Escherichia coli (E. coli) under mild visible light for the first time. Results showed that all E. coli (108 CFU/mL) could be eliminated under irradiation at 20 mW·cm−2 within 120 min. Based on the energy band determination and electron spin resonance analysis, the Z-scheme in the photocatalyst was responsible for the enhanced disinfection effects where Ag nanoparticles acting as the electron mediator. Scavenger experiments demonstrated that photogenerated holes and superoxide radicals were the main reactive species. The variations in cell membrane permeability, cell membrane structure, enzyme activities and ATP concentration were monitored, and results indicated that the reactive species overwhelmed the bacterial defense mechanism, leading to the penetration of bacterial membranes, release of ions, protein fragmentation, and eventually, inactivation.