Construction Of Antibacterial Platform Based On Two-dimensional Materials And Study On Photocatalytic Antibacterial Properties

Inorganic two-dimensional（2D）semiconductor materials exhibit special surface properties due to their unique physical properties,atomic thin geometry and high specific surface area,which provide many active sites for photocatalytic reactions.The preparation of high-crystalline atomic thin 2D materials is very essential for improving their photocatalytic properties.However,until now,there are a few studies on the preparation of 2D materials applied in photocatalytic antibacterial therapy field,and most of the reports were limited to the 2D materials with the response bands in ultraviolet and visible regions.However,ultraviolet or visible light may damage healthy tissue and has a limited depth of light penetration in the body,hindering in vivo applications as an antibacterial agent.Therefore,the preparation of the 2D materials with the high photocatalytic efficiency and near-infrared light response is a hot research topic.Hence,in this thesis,2D titanium dioxide nanosheets were doped with metal Ti³⁺ions by a self-doping process to achieve high-efficiency photocatalytic sterilization.Mixed-dimensional heterostructures of 1Dβ-Na YF₄:Yb,Er,Gd@2D 1T/2H-Mo S₂were also constructed,and the near-infrared photocatalytic antibacterial properties of the heterostructures were studied.The details are shown as follows:（1）The Ti³⁺self-doped blue two-dimensional Ti O₂ nanosheets were prepared by the solvothermal method.The prepared nanosheets with narrow band gap possess wide spectral response range.The nanosheets with（001）surface exposure ratio of 53.9%formed a heterojunction between the（001）surface and the（101）surface to promote photogenerated electron transfer,which can reduce the recombination of e^–-h⁺pairs to improve the photocatalytic properties.Under visible light irradiation,2×10⁶ CFU/m L Escherichia coli could be completely killed within 15 min with the concentration of 100μg/m L nanosheets.Our studies have proved that the two-dimensional Ti³⁺ion-doped Ti O₂ nanosheets with wide light response exhibit important application potential in photocatalytic sterilization.（In chapter two）（2）2D photocatalysts with near-infrared light region response are essential in vivo sterilization.Mixed-dimensional heterostructures of 1Dβ-Na YF₄:Yb,Er,Gd@2D1T/2H-Mo S₂ were fabricated through electrostatic interaction and used for near-infrared catalytic sterilization.Approximately 99.3%of Escherichia coli were killed effectively by 15 min irradiation of NIR light at a dose of 40μg m L^-1.And through matrix-assisted laser desorption ionization time-of-flight mass spectrometry（MALDI-TOF MS）the degradation of the strain was characterized.The effective bactericidal properties were ascribed to the high upconversion luminescence efficiency ofβ-Na YF₄:Yb,Er,Gd and the layered two-dimensional nanosheet structure of 1T/2H-Mo S₂.Under 980 nm light irradiation,β-Na YF₄:Yb,Er,Gd emits visible light,which is absorbed by Mo S₂,producing strongly oxidative holes and reductive electrons.Photogenerated electron–hole pairs were able to react with H₂O,O₂ and OH^-to produce reactive species in aqueous solution.These reactive species are strong nonselective oxidizing agents for sterilization.It shows that theβ-Na YF₄:Yb,Er,Gd@1T/2H-Mo S₂ nanocomposites can achieve excellent sterilization effect under near-infrared light in vivo sterilization.（In chapter three）...