Fabrication of Ag quantum dot/SnIn4S8 Schottky junction with enhanced photocatalytic inactivation of E. coli under visible light excitation

A highly efficient visible light driven Ag quantum dots (QDs)/SnIn4S8 Schottky junction photocatalyst was fabricated and applied for the inactivation of E. coli cells under visible light irradiation (λ > 420 nm). The 100 Ag QDs/SnIn4S8 composite displayed the highest inactivation ability with about 7.4 log cfu ml−1 of E. coli cells completely deactivated within 5 h visible light irradiation. The photocatalytic inactivation mechanism could be explained by the broken cell membrane, leakage and damage of biomolecules (proteins and DNA) as proved by scanning electron microscopy, electrophoresis, fluorescence-based stain and reactive species trapping experiments. The reactive species h+, and e− were involved in the bactericidal process over the Ag QDs/SnIn4S8 system. Moreover, the enhanced photoinactivation activity of Ag QDs/SnIn4S8 composites could be ascribed to the enhancement of light absorption by the surface plasmon resonance effect, the formation of the Schottky junction to facilitate the separation and migration of photoinduced charge carriers and the higher number of active sites provided by the enlarged specific surface area.