A mechanism study on the photocatalytic inactivation of Salmonella typhimurium bacteria by CuO loaded rhodium-antimony co-doped TiO nanorods.

This study presents the first report on the photocatalytic inactivation mechanism for a Salmonella typhimurium pathogen by visible-light active CuxO loaded rhodium-antimony co-doped TiO2 nanorods (CuxO/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 CuxO supported Rh-Sb-TiO2 NR photocatalyst was observed. The visible light active photocatalyst mainly produced reduced Cu+ in the lattice of CuxO 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.