Preparation And Antibacterial Properties Of Photocatalytic Materials Based On Bi₄O₅I₂

In recent years,with the rapid development of industry and the change in climate environment,bacteria,mold,and other harmful microorganisms continue to threaten human health,which has become a worldwide urgent problem to be solved.At present,the research on antibacterial technology mainly focuses on ultraviolet irradiation,ozone oxidation,chlorination and photocatalysis.Among them,photocatalytic antibacterial technology has become a research hotspot due to the advantages of simple materials,easy preparation,durable and efficient antibacterial,safety,green and environmental protection.In this paper,Bi₄O₅I₂/Bi OCl,Sn O_2-x/Bi₄O₅I₂,Ag/Sn O_2-x/Bi₄O₅I₂composites were prepared by using Bi₄O₅I₂ as matrix and compounding with Bi OCl,Sn O_2-x and Ag.The materials’microstructure,specific surface area,oxygen vacancy,energy band structure,photoelectric properties,and antibacterial properties were systematically characterized.Combining the band structure and capture experiment results,the antibacterial mechanism of the photocatalyst was revealed.The specific research contents of this paper are as follows:（1）A new Bi₄O₅I₂/Bi OCl（ICl）heterojunction was constructed by selecting narrow-band gap Bi₄O₅I₂ and wide-bandgap Bi OCl.X-ray diffraction（XRD）,transmission electron microscopy（TEM）and X-ray photoelectron spectroscopy（XPS）confirmed the successful construction of Bi₄O₅I₂/Bi OCl heterojunction.The optimal sample was 30%Bi₄O₅I₂/Bi OCl inactivated Escherichia coli（E.coli）within 30 min and Staphylococcus aureus（S.aureus）within 75 min.The process of bacterial death was observed by scanning electron microscopy（SEM）and laser confocal fluorescence electron microscopy（LSCM）.Photocurrent（PT）and electrochemical impedance（EIS）test results confirm that the composite material has higher electron-hole separation efficiency.The antibacterial mechanism of the photocatalyst was verified by the trapping experiment.（2）A new type of Sn O_2-x/Bi₄O₅I₂（SOI）heterojunction containing oxygen vacancy was synthesized by thermal decomposition of Sn O_2-x/Bi OI composites using Sn O_2-xwith a narrow bandgap that can be excited by visible light instead of Bi OCl.TEM,HRTEM and XPS characterization confirmed the point-plane structure of the Sn O_2-x/Bi₄O₅I₂ heterojunction.Compared with pure Sn O_2-x and Bi₄O₅I₂,SOI catalyst has better performance in removing E.coli and S.aureus.PT and EIS results confirm the efficient separation of electrons and holes in the composites.The capture experiment confirmed that the active species were mainly holes,and combined with the band structure of Sn O_2-x and Bi₄O₅I₂,it was inferred that the Sn O_2-x/Bi₄O₅I₂ photocatalytic system followed the double transfer mechanism.（3）To further improve the photocatalytic antibacterial performance,Ag/Sn O_2-x/Bi₄O₅I₂ ternary composites were prepared by an in-situ composite of Ag nanoparticles on Sn O_2-x/Bi₄O₅I₂ binary composites.XRD,TEM,XPS and other characterization methods proved that the ternary composites were successfully synthesized,and PT and EIS confirmed the excellent photoelectric properties of Ag/Sn O_2-x/Bi₄O₅I₂.Under an LED lamp,Ag/Sn O_2-x/Bi₄O₅I₂ can inactivate E.coil in 15 minutes and kill S.aureus in20 minutes.Compared with Bi₄O₅I₂/Bi OCl,Sn O_2-x/Bi₄O₅I₂,Bi₄O₅I₂ and Sn O_2-x,the antibacterial effect is more outstanding.Moreover,SEM and LSCM images directly show the death process of E.Coil caused by the photocatalytic reaction.The trapping experiments showed that the holes（h⁺）,electrons（e^-）and hydroxyl groups（·OH）were active substances,and the h⁺were the main active substances.The Ag/Sn O_2-x/Bi₄O₅I₂system followed the Z-type charge transfer mechanism.