Role of Hydroxyl Radicals and Mechanism of Escherichia coli Inactivation on Ag/AgBr/TiO2 Nanotube Array Electrode under Visible Light Irradiation

• Published in: Environmental science & technology 2012-04, Vol.46 (7), p.4042-4050
• Main Authors: Hou, Yang, Li, Xinyong, Zhao, Qidong, Chen, Guohua, Raston, Colin L
• Format: Article
• Language: English
• Subjects: Applied microbiology; Applied sciences; Biological and medical sciences; Bromides - chemistry; Catalysis - drug effects; Catalysis - radiation effects; Electrodes; Electron Spin Resonance Spectroscopy; Escherichia coli - drug effects; Escherichia coli - radiation effects; Escherichia coli - ultrastructure; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Hydroxyl Radical - pharmacology; Light; Microbial Viability - drug effects; Microbial Viability - radiation effects; Microbiology; Nanotubes - chemistry; Nanotubes - ultrastructure; Pollution; Potassium - metabolism; Silver - chemistry; Silver Compounds - chemistry; Spin Labels; Sterilization methods; Temperature; Titanium - chemistry; Water treatment and pollution
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es204079d

A ternary Ag/AgBr/TiO2 nanotube array electrode with enhanced visible-light activity was synthesized by a two-step approach including electrochemical process of anodization and an in situ photoassisted deposition strategy. The dramatically enhanced photoelectrocatalytic activity of the composite electrode was evaluated via the inactivation of Escherichia coli under visible light irradiation (λ>420 nm), whose performance of complete sterilization was much superior to other reference photocatalysts. PL, ESR, and radicals trapping studies revealed hydroxyl radicals were involved as the main active oxygen species in the photoelectrocatalytic reaction. The process of the damage of the cell wall and the cell membrane was directly observed by ESEM, TEM, and FTIR, as well as further confirmed by determination of potassium ion leakage from the killed bacteria. The present results pointed to oxidative attack from the exterior to the interior of the Escherichia coli by OH•, O2 •–, holes and Br0, causing the cell to die as the primary mechanism of photoelectrocatalytic inactivation.