Enhanced virucidal activity of facet-engineered Cu-doped TiO₂ nanorods under visible light illumination

Crystal facet engineering has emerged as a promising approach to enhance photocatalytic activity of semiconductors by preferentially accumulating charge carriers (electrons and holes) on specific facets. This facilitates efficient electron and hole transfer across the semiconductor/cocatalyst interface, enabling their transport to the cocatalyst surface for redox reactions. In this study, three Cu-doped TiO₂ nanorods with small, medium, and large ratios of reductive {110} to oxidative {111} facets were synthesized (namely Cu-TiO₂-SR, Cu-TiO₂-MR, and Cu-TiO₂-LR, respectively). These materials were comparatively evaluated for the inactivation of phiX174 bacteriophage under visible light illumination. Notably, Cu-TiO₂-LR demonstrated an outstanding inactivation rate of phiX174 (0.42 log inactivation/min), approximately 11.8 times higher than that of Cu-TiO₂-SR. Photo- and electrochemical analyses revealed that Cu-TiO₂-LR exhibited superior electron/hole separation efficiency, leading to enhanced Cu redox reactions. Various experiments, encompassing viral inactivation tests with different additives, protein oxidation assays, and DNA damage assessments, indicated that Cu(III) is the major virucidal species responsible for the phiX174 inactivation by illuminated Cu-TiO₂-LR. Under visible light illumination, Cu-TiO₂-LR also showed excellent reusability and minimal activity loss in the presence of humic acid and inorganic anions, as well as general microbicidal effects on other viral and bacterial species.