Visible-light-driven photocatalytic inactivation of E. coli K-12 by bismuth vanadate nanotubes: bactericidal performance and mechanism.

Bismuth vanadate nanotube (BV-NT), synthesized by a template-free solvothermal method, was used as an effective visible-light-driven (VLD) photocatalyst for inactivation of Escherichia coli K-12. The mechanism of photocatalytic bacterial inactivation was investigated by employing multiple scavengers combined with a simple partition system. The VLD photocatalytic bacterial inactivation by BV-NT did not allow any bacterial regrowth. The photogenerated h(+) and reactive oxidative species derived from h(+), such as OH(ads), H(2)O(2) and HO(2)/O(2)(-), were the major reactive species for bacterial inactivation. The inactivation by h(+) and OH(ads) required close contact between the BV-NT and bacterial cells, and only a limited amount of H(2)O(2) could diffuse into the solution to inactivate bacterial cells. The direct oxidation effect of h(+) to bacterial cells was confirmed by adopting F(-) surface modification and anaerobic experiments. The bacterial cells could trap e(-) in order to minimize e(-)-h(+) recombination, especially under anaerobic condition. Transmission electron microscopic study indicated the destruction process of bacterial cell began from the cell wall to other cellular components. The OH(ads) was postulated to be more important than OH(bulk) and was not supposed to be released very easily in the BV-NT bacterial inactivation system.