Bactericidal mechanisms of Ag₂O/TNBs under both dark and light conditions

Ag(2)O/TNBs were fabricated by depositing Ag(2)O nanoparticles on the surface of TiO(2) nanobelts (TNBs). The disinfection activities of Ag(2)O/TNBs on two representative bacterial types: Gram-negative Escherichia coli ATCC15597 and Gram-positive Bacillus subtilis, were examined under both dark and visible light conditions. Ag(2)O/TNBs exhibited stronger bactericidal activities than Ag(2)O nanoparticles and TNBs under both dark and light conditions. For both cell types, disinfection effects of Ag(2)O/TNBs were greater under light conditions relative to those under dark conditions. The bactericidal mechanisms of Ag(2)O/TNBs under both dark and light conditions were explored. Ag(+) ions released from Ag(2)O/TNBs did not contribute to the bactericidal activity of Ag(2)O/TNBs under dark conditions, whereas the released Ag(+) ions showed bactericidal activity under visible light irradiation conditions. Active species (H(2)O(2), O(2)(-)·, and e(-)) generated by Ag(2)O/TNBs played important roles in the disinfection processes under both dark and visible light irradiation conditions. Without the presence of active species, the direct contact of Ag(2)O/TNBs with bacterial cells had no bactericidal effect.