Bactericidal activity and mechanism of AgI/AgBr/BiOBr0.75I0.25 under visible light irradiation

The Agl/AgBr/BiOBr0.75I0.25 nanocomposites were synthesized by a solvothermal process, followed by an in-situ ion exchange reaction. The disinfection activities of the as-synthesized photocatalyst to model cell type, Gram-negative Escherichia coli (E. coli), were investigated under visible light irradiation condition lambda >= 400 nm). Results showed that 80 mg/L AgI/AgBr/BiOBr0.75I0.25 could completely inactivate 3 x 10(7) CFU mL(-1) E. coli cells within 30 mm under visible light irradiation. Moreover, the bactericidal mechanisms involved in the photocatalytic disinfection process were systematically investigated. Ag+ ions released from the nanocomposites negligibly contributed to the bactericidal activity, while active species including h(+), e(-) and O-center dot(2)- played important roles in the disinfection system. Direct contact of bacterial cells and nanoparticles was found to be the prerequisite for both the generation of O-center dot(2)- and the disinfection processes. The disruption of cell membrane and emission of cytoplasm directly inactivated E. coil cells. In addition, AgI/AgBr/BiOBr0.75I0.25 exhibited strong antibacterial activity toward E. coli even in four consecutive reused cycles. (C) 2015 Elsevier B.V. All rights reserved.