Facile fabrication of Ag/C-TiO2 nanoparticles with enhanced visible light photocatalytic activity for disinfection of Escherichia coli and Enterococcus faecalis

This work aimed to investigate the promotive effect of Ag modification on C-TiO2 for visible light photocatalytic disinfection of microorganisms. Ag/C-TiO2 was prepared by a facile one-step synthesis approach through thermal oxidation of AgNO3-impregnated TiC precursor. The self-doped carbon exists as both interstitial and substitutional carbon to collectively enhance the visible light photocatalytic absorption. The loaded silver nanoparticles were uniformly distributed on the TiO2 surface in the Ag-0 metallic state, further enhancing the visible light absorption due to surface plasmon resonance yet inhibiting the charge carrier recombination by conduction band electron trapping. The band structure and a tentative visible light photocatalytic disinfection mechanism of Ag/C-TiO2 with four pathways were thus proposed, and the enhanced visible light photocatalytic performance was demonstrated for disinfection of Escherichia coli (E. coli) and Enterococcus faecalis (E. faecalis) in comparison with C-TiO2. This improvement was more pronounced with increasing Ag loading in the range of 0.5-5.0 wt%, which can be attributed to the improved visible light absorption and good charge carrier separation due to Ag modification as well as to the inherent bactericidal effect of metallic Ag.