A mechanism study on the photocatalytic inactivation of: Salmonella typhimurium bacteria by Cu_xO loaded rhodium-antimony co-doped TiO₂ nanorods

This study presents the first report on the photocatalytic inactivation mechanism for a Salmonella typhimurium pathogen by visible-light active Cu_xO loaded rhodium-antimony co-doped TiO₂ nanorods (Cu_xO/Rh-Sb-TiO₂ NRs) under visible light irradiation (cutoff filter, λ ≥ 420 nm). Remarkably higher pathogenic inactivation of 4 log within 40 min by a Cu_xO supported Rh-Sb-TiO₂ NR photocatalyst was observed. The visible light active photocatalyst mainly produced reduced Cu⁺ in the lattice of Cu_xO by charge separation. By this means, photo-generated electrons at the conduction band of Rh-Sb-TiO₂ NRs play an important role in reducing Cu²⁺ to Cu⁺ through the photocatalytic reduction reaction (PRR), and at the valence band of Rh-Sb-TiO₂ NRs, photo-generated holes generate OH radicals through the photocatalytic oxidation reaction (POR). This Cu⁺ copper species is lethal to microbial pathogens. The inactivation mechanism for the Salmonella typhimurium pathogen was investigated by protein oxidation, HCHO production, and the API-ZYM system. To investigate the role of OH radicals, t-BuOH and MeOH as hole scavengers were used in photocatalytic inactivation reactions. Our experimental results confirmed that the reduced Cu⁺ species play a major role in bacterial inactivation, while ROS have a major effect on the degradation of organic pollutants.