Efficient Destruction of Pathogenic Bacteria with NiO/SrBi2O4 under Visible Light Irradiation

The photocatalytic inactivation of pathogenic bacteria in water was investigated systematically with NiO/SrBi2O4 under visible light (λ>420 nm) irradiation. The catalyst was found to be highly effective in killing Escherichia coli, a Gram-negative bacterium, and Staphylococcus aureus, a Gram-positive bacterium. ESR studies revealed that •OH and O2 •- were involved as the active species in the photocatalytic reaction. The decomposition process of the cell wall and the cell membrane was directly observed by TEM and further confirmed by the determination of potassium ion (K+) leakage from the killed bacteria. A possible cell damage mechanism by visible-light-driven NiO/SrBi2O4 is proposed. In addition, the effects of pH, methanol, and inorganic ions on bacterial photocatalytic inactivation were investigated. These results indicated that the electrostatic force interaction of bacteria-catalyst is crucial for high bactericidal efficiency.