Modification Design And Antibacterial Mechanism Study Of Bi₅O₇NO₃ Photocatalys

Industrial progress in society is undoubtedly accompanied by problems such as energy scarcity and environmental pollution.Contamination of water sources with pathogenic microorganisms has become a serious threat to the healthy development of all mankind,and therefore there is an urgent need to develop efficient antimicrobial technologies to curb the growth of bacteria in the environment.Bi₅O₇NO₃ has shown great promise in the field of photovoltaic antibacterial applications due to its unique layered structure,suitable visible absorption energy gap and complex tunable band hybridization structure.In this paper,based on the properties of the layered structure of Bi₅O₇NO₃,we design two different modification methods,surface modification and heterostructure construction,with the objective of increasing the visible light absorption capacity and decreasing the efficiency of the recombination of electron-hole states in the material.1)A simple hydrothermal synthesis method was used to control the morphological size and the concentration of surface defects by adjusting the p H value in the initial solution of the reaction to obtain surface-modified Bi₅O₇NO₃with high photovoltaic antibacterial activity.Experimental results show that controlling the morphological size,the concentration of oxygen vacan cy defects,and the relative content of multivalent bismuth in Bi₅O₇NO₃ by regulating the OH-concentration is a good way to improve the photocatalytic activity of Bi₅O₇NO₃.The key to increasing the photocatalytic activity of Bi₅O₇NO₃.The effect of the sample on the removal of organic dyes under visible light irradiation was investigated.In particular,B-p8 shows optimal performance at a controlled initial solution p H of 8.0 due to its smaller grain size,higher concentration of oxygen vacancies and synergistic effect of multivalent Bi.The adsorption rate of 20 mg/L of MO within 30 min of visible light irradiation in the simulation was as high as 92%;The degradation rate of 20 mg/L Rh B after 7h of irradiation is more than 90%.2)To investigate the photocatalytic antibacterial activity of the surface modified Bi₅O₇NO₃ on E.coli and S.aureus.The antimicrobial effect was found to be proportional to the photocatalytic activity.The B-p8 sample with the best antimicrobial performance achieved more than 99%antimicrobial resistance against E.coli and S.aureus at concentrations of 0.5 mg/m L and 0.8 mg/m L,respectively.In addition,the antibacterial mechanism of surface modification of Bi₅O₇NO₃ was revealed to be photovoltaic generation of ROS,with the dominant active material being·OH,·O₂^-.3)A series of ZnO/Bi₅O₇NO₃ composite photocatalysts with S-type heterojunctions were synthesized by combining two synthetic methods,hydrothermal and co-precipitation,by quantitatively depositing ZnO nanoparticles on the surface of flake Bi₅O₇NO₃,further enhancing the antibacterial performance of the material.The analytical results show that the successful coupling of Bi₅O₇NO₃ to ZnO can effectively enhance the interfacial charge transfer efficiency and the separation efficiency of the joint charge carriers of the material.At the same time,the loading of ZnO may introduce new band levels,resulting in a narrowing of the band gap and a significant shift of the optical absorption edge towards the visible region,which significantly enhances the visible light utilization of the material.4)The photocatalytic performance of the heterojunction ZnO/Bi₅O₇NO₃composites was investigated by antibacterial experiments.The antibacterial efficiency was 12.2 and 13.3 times higher than that of the surface-modified Bi₅O₇NO₃,respectively.In addition,the antibacterial mechanism shows that ROS generated by heterojunction ZnO/Bi₅O₇NO₃ under light conditions remains the dominant antibacterial mode,and the excellent antibacterial performance is a result of the combination of the three active species·OH,·O₂^-and H₂O₂.