Preparation Of Bismuth Iodide Oxide Composites And Study Of Their Visible Light Photocatalytic Antibacterial Properties And Mechanis

In recent years,the quality of people’s life is gradually improved,so the requirements of the surrounding living environment are also gradually improved,which promotes the application of antibacterial materials in People’s Daily life.However,the traditional antibacterial materials are ionic antibacterial materials based on Ag,Au,Cu,etc.These materials themselves have certain cytotoxicity,but also lead to the loss of materials in the process of use.Therefore,photocatalytic antibacterial materials gradually come into people’s view.In this study,Bi OI material with relatively short band gap among bismuth halide materials was selected as the base.After further modification,its photocatalytic activity and antibacterial properties were investigated.The crystalline structure,elemental composition and appearance of the materials were studied by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,X-ray photoelectron spectroscopy and other characterization methods.Meanwhile,the photocatalytic activity of prepared samples was studied by using UV-visible diffuse reflection,ESR,PL spectroscopy,electrochemical workstation and other characterization methods.Finally,Escherichia coli was used as the strain,and the photocatalytic antibacterial performance of the new materials was evaluated.Firstly,Bi₄O₅I₂ flower-like microspheres modified with oxygen-rich vacancy Bi were prepared by solvothermal method using Bi（NO₃）₃·5H₂O and KI as raw materials.In this study,by introducing impurity states and surface defects,the band gap is reduced and the electron-hole pair separation efficiency is improved.Under visible light irradiation,the bactericidal activity of BIO-3 samples against E.coli reached more than 99%within30 minutes,which was significantly higher than that of Bi₄O₅I₂（37.99%）.Further experiments on the bacteriostatic mechanism showed that the bacteriostatic effect of BIO-3 samples mainly came from the production of reactive oxygen species（ROS）,and the experiment on reactive oxygen species showed that superoxide radical（·O₂^-）was the key active substance in the bacteriostatic process of BIO-3 materials.Lipid peroxidation test and respiratory chain dehydrogenase test confirmed that these reactive oxygen species have both internal and external effects on bacteria.These results provide important ideas for the further development of bismuth-based antimicrobials.In order to investigate the changes of photocatalytic activity,antibacterial properties and mechanism of the materials doped with non-metallic elements,Br/Bi OI composites were prepared by solvothermal method with Br as doping element.At the same time,Br and I belong to the same halogen element,which leads to the similar ionic radius of the two elements,which leads to the incorporation of Br into the Bi OI lattice and the replacement of I in it to form a solid solution.As Br is doped into Bi OI lattice,an insertion level will be formed between the conduction band and valence band of Bi OI,further shortening the band gap width of the material.In this study,the photocatalytic activity of pure Bi OI was successfully improved by controlling the addition amount of Br element,and the production of reactive oxygen species was further improved.The characterization of ESR,UV-visible diffusion reflection and antibacterial experiments also showed that the antibacterial and photocatalytic activities of Br/Bi OI materials reached the maximum when the addition amount of Br element reached 0.13%.The source of the antibacterial activity of Br/Bi OI was investigated by free radical trapping experiments.The experimental results showed that·O₂^-and h+were the main active groups that contributed the most to the antibacterial activity after adding free radical trapping agents to the distilled water dissolved with Br/Bi OI composites.