Effective Photocatalytic Disinfection of E. coli K-12 Using AgBr−Ag−Bi2WO6 Nanojunction System Irradiated by Visible Light: The Role of Diffusing Hydroxyl Radicals

Abstract

Urgent development of effective and low-cost disinfecting technologies is needed to address the problems caused by an outbreak of harmful microorganisms. In this work, we report an effective photocatalytic disinfection of E. coli K-12 by using a AgBr−Ag−Bi₂WO₆ nanojunction system as a catalyst under visible light (λ ≥ 400 nm) irradiation. The visible-light-driven (VLD) AgBr−Ag−Bi₂WO₆ nanojunction could completely inactivate 5 × 10⁷ cfu mL⁻¹E. coli K-12 within 15 min, which was superior to other VLD photocatalysts such as Bi₂WO₆ superstructure, Ag−Bi₂WO₆ and AgBr−Ag−TiO₂ composite. Moreover, the photochemical mechanism of bactericidal action for the AgBr−Ag−Bi₂WO₆ nanojunction was investigated by using different scavengers. It was found that the diffusing hydroxyl radicals generated both by the oxidative pathway and the reductive pathway play an important role in the photocatalytic disinfection. Moreover, direct contact between the AgBr−Ag−Bi₂WO₆ nanojunction and bacterial cells was not necessary for the photocatalytic disinfection of E. coli K-12. Finally, the photocatalytic destruction of the bacterial cells was directly observed by TEM images and further confirmed by the determination of potassium ion (K⁺) leakage from the killed bacteria. This work provides a potential effective VLD photocatalyst to disinfect the bacterial cells, even to destruct the biofilm that can provide shelter and substratum for microorganisms and resist to disinfection.