Improvement of photocatalytic antibacterial action of Mn, Sv-co-doped ZnIn2S4 prepared by a novel Ov-rich α-MnO2 decomposition approach

Abstract

This study introduces a novel solid-state decomposition method to incorporate Mn from α-MnO₂ into ZnIn₂S₄ (ZIS), enhancing its photocatalytic antibacterial properties. Under 6 h of visible light irradiation, the antibacterial efficiency of ZnIn₂S₄/α-MnO₂ = 4 : 1 (ZM-0.25, mass ratio) against Pseudomonas aeruginosa (83.64%) is 1.31 times higher than that of pure ZIS (63.93%), with 9.64% and 23.53% improvements against Escherichia coli and Staphylococcus aureus, respectively. Scanning and transmission electron microscopy analyses confirm the complete decomposition of α-MnO₂. Meanwhile, inductively coupled plasma optical emission spectroscopy verifies the presence of Mn in ZM-0.25. Photoelectrochemical and photoluminescence results indicate that Mn doping promotes charge carrier separation, while the increased sulfur vacancies enhance electron trapping. Electron paramagnetic resonance (EPR) measurements also reveal elevated ˙OH and ˙O₂⁻ radical generation in ZM-0.25, linking directly to its improved photocatalytic activity. Density functional theory and Kelvin probe force microscopy demonstrate that ZM-0.25 has a reduced work function, lowering the potential barrier for the escape of photogenerated electrons, while S–Mn covalent bonds as an ‘electron bridge’ facilitate the transfer of electrons. The solid-state decomposition method incorporates more Mn into ZnIn₂S₄, improving its degradation efficiency, thereby offering an advantage over traditional ionic doping. This work provides valuable insights for the optimization of photocatalytic antibacterial activity and the selection of doping methods for future studies.