ABSTRACT
PURPOSE: We examined the inactivation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by a nitrogen-doped titanium dioxide (N-TiO2) visible-light photocatalyst that was activated via light irradiation in the natural environment and was safe for human use as a coating material. METHODS: The photocatalytic activity of glass slides coated with three types of N-TiO2 without metal or loaded with copper or silver and copper was investigated by measuring acetaldehyde degradation. The titer levels of infectious SARS-CoV-2 were measured using cell culture after exposing photocatalytically active coated glass slides to visible light for up to 60 min. RESULTS: N-TiO2 photoirradiation inactivated the SARS-CoV-2 Wuhan strain and this effect was enhanced by copper loading and further by the addition of silver. Hence, visible-light irradiation using silver and copper-loaded N-TiO2 inactivated the Delta, Omicron, and Wuhan strains. CONCLUSION: N-TiO2 could be used to inactivate SARS-CoV-2 variants, including emerging variants, in the environment.