Visible-Light-Activated TiO2-Based Photocatalysts for the Inactivation of Pathogenic Bacteria

Pathogenic bacteria in the environment pose a significant threat to public health. Titanium dioxide (TiO2)-based photocatalysts have emerged as a promising solution due to their potent antimicrobial effects under visible light and their generally eco-friendly properties. This review focuses on the antibacterial properties of visible-light-activated, TiO2-based photocatalysts against pathogenic bacteria and explores the factors influencing their efficacy. Various TiO2 modification strategies are discussed, including doping with non-metals, creating structure defects, combining narrow-banded semiconductors, etc., to extend the light absorption spectrum from the UV to the visible light region. The factors affecting bacterial inactivation, and the underlying mechanisms are elucidated. Although certain modified TiO2 nanoparticles (NPs) show antibacterial activities in the dark, they exhibit much higher antibacterial efficacies under visible light, especially with higher light intensity. Doping TiO2 with elements such as N, S, Ce, Bi, etc., or introducing surface defects in TiO2 NPs without doping, can effectively inactivate various pathogenic bacteria, including multidrug-resistant bacteria, under visible light. These surface modifications are advantageous in their simplicity and cost-effectiveness in synthesis. Additionally, TiO2 can be coupled with narrow-banded semiconductors, resulting in narrower band gaps and enhanced photocatalytic efficiency and antibacterial activities under visible light. This information aids in understanding the current technologies for developing visible-light-driven, TiO2-based photocatalysts and their application in inactivating pathogenic bacteria in the environment.