Preparation Of Light-Responsive Nano Antibacterial Materials And Research On Environmental Disinfection And Anti-Infection Treatment

Pathogens,fungi and other microorganisms in the environment seriously affect environmental sanitation and public health.Every year,17 million people worldwide die from infectious diseases caused by pathogens in the environment,and this number is increasing.For a long time,the discovery of chemical treatments such as antibiotics has largely alleviated the adverse effects caused by bacterial infections.However,people’s abuse of antibiotics promotes the rapid development and spread of bacterial resistance to antibiotics.For this reason,people urgently need to develop an antibacterial therapy that is safe,reliable and can replace traditional antibiotic treatment to deal with the problem of bacterial infection.At present,photoactive antibacterial strategies,such as photocatalysis and photothermal sterilization,are expected to become a new alternative to traditional antibiotic therapy due to their excellent bactericidal ability,lower risk of bacterial resistance and low biological toxicity.Photocatalytic antibacterial uses harmless sunlight or near-infrared light sources to excite photosensitive materials and induce the production of reactive oxygen species,including¹O₂,·OH etc.Photothermal agents convert light energy into heat,which not only causes bacteria to undergo a series of inactivation reactions and eventually die,but the heat also increases the susceptibility of bacteria,so that bactericidal substances such as reactive oxygen species can better act on bacteria and enhance the bactericidal effect.In this thesis,single-phase degradable material was modified and a new type of heterojunction was constructed are used as means,which enhanced the photocatalytic and photothermal properties of the material.Subsequently,we conducted an in-depth study on the enhancement mechanism of the material properties.In addition,the antibacterial properties and antibacterial mechanism of the materials were systematically investigated through in vitro and in vivo experiments,and their biocompatibility was also evaluated.The research work in this thesis consists of the following:1.Environmentally friendly degradable red phosphorus nanoparticles for rapid visible light sterilization.We developed red phosphorus nanoparticles（RPNPs）,a safe and degradable photosensitive material with good photocatalytic and photothermal properties.The red phosphorus nanoparticles were prepared by the template method and sonicated.Under the condition of simulated sunlight irradiation for 20 min,RPNPs had good photocatalytic and photothermal performance,and the killing rate of Staphylococcus aureus could reach 99.98%.Transmission electron microscopy and UV-Vis spectroscopy analysis showed that RPNPs can be degraded within 8 weeks.Both RPNPs and their degradation products are non-toxic to fibroblasts.Therefore,these RPNPs are expected to be a new type of low-cost,efficient,degradable,biocompatible and eco-friendly environmentally disinfected photosensitive material.2.Construction of 0-dimensional/2-dimensional Schottky heterojunctions and study of the enhancement mechanism of photocatalytic and photothermal properties.Ti₃AlC₂ was first etched,intercalated and ultrasonically exfoliated to obtain Ti₃C₂nanosheets,followed by a simple wet chemical method to grow Ag₂S nanoparticles uniformly in situ on the surface of Ti₃C₂ nanosheets.Ag₂S/Ti₃C₂ Schottky heterojunctions with different components were synthesized by controlling the mass ratio of Ti₃C₂ to Ag₂S.We investigated the detailed mechanism of the photocatalytic process of heterojunctions by density flooding theory calculations（DFT）.The excellent photocatalytic properties of the material effectively promote the reaction of reactive oxygen species generation.In addition,more photogenerated hot carriers generated by the heterojunction can not only heat up the lattice by generating phonons in the deep defects of Ag₂S,but also transfer more to the Ti₃C₂ surface to enhance the LSPR effect to generate more heat.Thus,the heterostructure greatly enhances the photocatalytic and photothermal performance of the material.3.Study of antibacterial properties and biocompatibility assessment of Ag₂S/Ti₃C₂ Schottky heterojunction in vivo and in vitro.The enhanced photocatalytic and photothermal conversion properties of Ag₂S/Ti₃C₂Schottky heterojunctions were effective in the killing of S.aureus.In vitro antimicrobial experiments showed that the composite material with the best mass ratio exhibited a synergistic antimicrobial rate of 99.99%between photodynamic and photothermal effects under 808 nm NIR light irradiation for 20 min.The material has also shown superior therapeutic efficacy to commercial 3M dressings in the evaluation of in vivo wound infection treatment.In addition,the material showed good biocompatibility in vivo and in vitro.Therefore,this novel heterojunction is expected to be a promising platform for NIR treatment of bacterial infections.