Photodynamic antibacterial activity of CoTiO3/ZnIn2S4 Z-type heterojunction and its efficient enhancement mechanism by reactive oxygen species

The Solar-powered photocatalytic antibacterial technology has received widespread attention as a safe and efficient environmental self-cleaning technology, but its application remains a challenging task. Taking inspiration from the design of heterojunction structures in photocatalytic materials, this study employed a precipitation in-situ synthesis method to successfully construct a CoTiO₃/ZnIn₂S₄ (CTZIS) Z-scheme heterojunction with excellent photocatalytic performance by depositing layered ZnIn₂S₄ nanosheets in situ on a rod-shaped CoTiO₃ support. After visible-light irradiation for 20 min, the CTZIS antimicrobial agent (100 μg/mL) exhibited an ultra-high bacterial inactivation rate of 99.9 %, which was 10 and 11 times higher than that of ZnIn2S4 and CoTiO3 under the same conditions, using E. coli as the study object. Meanwhile, bacteria treated with CTZIS exhibited the highest degree of cell membrane lipid peroxidation and the lowest activity of intracellular respiratory chain dehydrogenase, demonstrating excellent antibacterial performance. After testing and calculation, it was found that the excellent antibacterial activity comes from the solid gap electric field between heterojunctions, which enhances the effective spatial separation of photo-generated carriers and effectively increases the quantum yield of reactive oxygen species (ROS). The synergistic antibacterial mechanism of CTZIS from bacterial surface to bacterial interior co-damage was revealed, in which the production of • $O_2^{‐}$ and •OH are a key active substance in the process of bacterial oxidative stress inactivation.