Visible-light-induced bactericidal activity of a nitrogen-doped titanium photocatalyst against human pathogens

The antibacterial activity of photocatalytic titanium dioxide (TiO ₂) substrates is induced primarily by UV light irradiation. Recently, nitrogen- and carbon-doped TiO₂ substrates were shown to exhibit photocatalytic activities under visible-light illumination. Their antibacterial activity, however, remains to be quantified. In this study, we demonstrated that nitrogen-doped TiO₂ substrates have superior visible-light-induced bactericidal activity against Escherichia coli compared to pure TiO₂ and carbon-doped TiO₂ substrates. We also found that protein- and light-absorbing contaminants partially reduce the bactericidal activity of nitrogen-doped TiO₂ substrates due to their light-shielding effects. In the pathogen-killing experiment, a significantly higher proportion of all tested pathogens, including Shigella flexneri, Listeria monocytogenes, Vibrio parahaemolyticus, Staphylococcus aureus, Streptococcus pyogenes, and Acinetobacter baumannii, were killed by visible-light-illuminated nitrogen-doped TiO₂ substrates than by pure TiO₂ substrates. These findings suggest that nitrogen-doped TiO₂ has potential application in the development of alternative disinfectants for environmental and medical usages.