Preparation And Antibacterial Performance Of Self-doped TiO₂ Composite Photocatalytic Materials

In recent years,with the increasingly prominent problems of air and water pollution,a variety of harmful microorganisms continue to breed and mutate,which has a huge impact on people's healthy life.Semiconductor photocatalysis has become a new green sterilization method because it can inhibit the growth of microorganisms by using reactive oxygen species.At present,the most studied photocatalytic antibacterial material is TiO₂.However,the wide band gap,low visible light response and fast recombination of photogenerated electron-hole pairs restrict the practical application of TiO₂ materials in the field of antibacterial.In order to overcome the defects of TiO₂,the introduction of Ti³⁺into TiO₂ lattice is an efficient route to obtain good visible light photocatalytic activity.In addition,constructing Ti³⁺self-doped TiO₂(Ti³⁺-TiO₂)-based heterogeneous composite materials by means of metal loading and semiconductor composite can further increase the absorption of visible light and improve the separation efficiency of photogenerated carriers,thus contributing to the improvement of photocatalytic performance.In this paper,various Ti³⁺-TiO₂/Ni,Ti³⁺-TiO₂/AgI and Ti³⁺-TiO₂/Cu₂O-Cu were prepared successively on the basis of Ti³⁺-TiO₂materials.The morphology,structure and optical properties of the composite materials were investigated by a series of characterization?XRD,TEM,XPS,EPR,UV-vis and PL?.The antimicrobial activities of the composites under visible light were studied with E.coli and Fusarium gramineae as the test objects,and the antimicrobial mechanism was further discussed.?1?The Ti³⁺-TiO₂/Ni composite materials were prepared by loading different Ni metals on Ti³⁺-TiO₂ materials synthesized via solvothermal method.From XRD,TEM and XPS characterizations,it can be seen that Ni nanoparticles are loaded on the surface of Ti³⁺-TiO₂nanosheets and form a heterostructure.The photocatalytic performances were evaluated by degrating tetracycline?TC?and killing Escherichia coli?E.coli?under visible light.The photodegradation experiment showed that 5%Ti³⁺-TiO₂/Ni composite had the best degradation effect of TC,82%TC could be degraded in 80 min.In the antibacterial experiment,2.5 log of E.coli could be killed in 5 h with the 5%Ti³⁺-TiO₂/Ni composite,which was better than that of Ti³⁺-TiO₂.The steady-state fluorescence spectrum analysis revealed that the loading of Ni could improve the separation of photogenerated electron-hole pairs and inhibit the recombination,thus increasing the photocatalytic performances.ESR test showed that the composite could produce superoxide radicals and hydroxyl radicals with strong redox ability during the antibacterial process,which resulted in the inactivation of E.coli.?2?The Ti³⁺-TiO₂/AgI composite materials with different proportions?5%,10%,20%,40%?of AgI were prepared via chemical precipitation.The XRD,TEM and XPS results showed that AgI and Ti³⁺-TiO₂ have successfully formed heterojunction composites.The photocatalytic performances were evaluated by degrating Rhodamine B?RhB?and killing Escherichia coli?E.coli?as well as Fusarium graminearum?F.graminearum?under visible light.It was found that 20%Ti³⁺-TiO₂/AgI composite had the best degradation effect on RhB,and could completely degrade RhB in 40 minutes.The antibacterial effect of E.coli and F.graminearum was studied with 20%Ti³⁺-TiO₂/AgI composite,it can kill 8 log of E.coli in 40minutes and it has better killing ability of F.graminearum in 100 minutes.The steady-state fluorescence spectrum analysis revealed that the formation of heterojunction can improve the separation of photogenerated electron-hole pairs and inhibit their recombination,thus increasing the photocatalytic activities.The active species trapping experiments showed that the photogenerated electrons,holes,superoxide radicals and hydroxyl radicals of Ti³⁺-TiO₂/AgI composite were all involved in the inactivation process of E.coli.?3?The Ti³⁺-TiO₂/Cu₂O-Cu composite materials with different proportions?2.5%,5%,10%,15%?were prepared by in situ chemical reduction method.From XRD,TEM and XPS analysis,it can be seen that Cu₂O and Cu nanoparticles were depostied on the surface of Ti³⁺-TiO₂ materials.E.coli and F.graminearum were used to evaluate of photocatalytic antimicrobial activities.It was found that different proportion of Ti³⁺-TiO₂/Cu₂O-Cu composite materials had good antimicrobial efficiencies in killing E.coli and F.graminearum,15%Ti³⁺-TiO₂/Cu₂O-Cu composite material can inactivate all 8 log E.coli and kill 2.4 log F.graminearum within 100 minutes.Through steady-state fluorescence spectroscopy,it can be seen that the loading of Cu₂O and Cu improved the separation of photogenerated electron-hole pairs and inhibits their renewal recombination,thus increasing the photocatalytic antimicrobial activities.The active species trapping experiment revealed that the photogenerated electrons,superoxide radicals and hydroxyl radicals produced by Ti³⁺-TiO₂/Cu₂O-Cu composite were the main active species to inactivate E.coli during the process of photocatalysis.