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.

Carbon dots represent a rapidly advancing and expanding research field, with a large number of literature reports on their potential technological applications including those relevant to food safety. In this article, the dot samples prepared by the deliberate chemical functionalization of preexisting small carbon nanoparticles or by thermal carbonization of various organic precursors under different processing conditions are highlighted and critiqued for their similarities and differences in sample structure-morphology and properties, especially antimicrobial properties for their food safety–related uses. Also highlighted and discussed are representative recent examples for the use of dot samples to inactivate foodborne pathogens, disrupt biofilms or prevent their formation, and extend the shelf life of food products, which involve different antibacterial mechanisms. Some perspectives on the further development of the carbon dots–based/derived antimicrobial platform and related excellent application opportunities in food safety are provided.

Carbon–semiconductor hybrid quantum dots are classical carbon dots with core carbon nanoparticles doped with a selected nanoscale semiconductor. Specifically, on those with the nanoscale TiO₂ doping, denoted as C_TiO2-Dots, their synthesis and thorough characterization were reported previously. In this work, the C_TiO2-Dots were evaluated for their visible light-activated antibacterial function, with the results showing the effective killing of not only Gram-positive but also the generally more resistant Gram-negative bacteria. The hybrid dots are clearly more potent antibacterial agents than their neat carbon dot counterparts. Mechanistically, the higher antibacterial performance of the C_TiO2-Dots is attributed to their superior photoexcited state properties, which are reflected by the observed much brighter fluorescence emissions. Also considered and discussed is the possibility of additional contributions to the antibacterial activities due to the photosensitization of the nanoscale TiO₂ by its doped core carbon nanoparticles.

A quantitative approach was developed to systematically evaluate the antimicrobial activity of CuWO ₄ /CuS hybrid composites. This approach offers a new way to search for effective combinations of two or more semiconductors for pathogen disinfection.

Combating antibiotic-resistant bacteria has been a long-lasting challenge. This study investigated the photoactivated antibacterial function of carbon dots (CDots) in combination with antibiotics and membrane destabilizing agents as co-agents against drug resistant bacteria E. faecalis and L. monocytogenes. The results of the study demonstrated that CDots in combination with the membrane destabilizing agent poly-L-lysine as co-agent exhibited significant enhancement in the overall antibacterial activity, especially with the longer poly-L-lysine, achieving complete inactivation of cells in the samples with ~ 8 log viable cell reduction. The combination of CDots with bacterial resistant antibiotics streptomycin, erythromycin, or tetracycline, did not expectedly enhance the overall antibacterial activity of photoactive CDots to E. faecalis, in contrast, the combination with streptomycin significantly reduced the antibacterial activity of CDots. Implications of these experimental results toward the understanding of mechanistical action of photoexcited CDots were discussed. The study demonstrated that appropriately selected co-agents could effectively enhance the photoactivated antibacterial function of CDots and its potential to combat drug resistant pathogens.