Synthesis And Modification Of Nano ZnO For Antibacterial Application

High thermal and chemical stability,excellent antibacterial properties,and Zn as an essential element required for growth make ZnO NPs attractive for potential use in biomedical fields.In this dissertation,the antibacterial properties of ZnO samples with different morphologies obtained by different zinc oxide synthesis methods were compared.Through the doping of cerium(Ce)elements in the zinc oxide lattice and the surface modification of sodium alginate organic compounds were designed to improving the antibacterial property of ZnO samples.Then the possible antibacterial mechanism was speculated.This paper mainly includes the following parts:(1)Using thermal decomposition method,precipitation method,solvothermal method and sol-gel method to synthesize"leaf-shaped","rice-shaped","hexagonal flower-shaped",and self-assembled"spherical"ZnO micro-nano particles.Zone of inhibition method was used to qualitatively assess the antibacterial effectiveness of four ZnO particles with different morphologies.The results of antibacterial properties showed that the spherical ZnO samples synthesized by solvothermal method had better antibacterial properties.In the solvothermal method,the influence of different solvent types,material ratios,and sodium acetate addition on the morphology of the product were intensively explored.The results showed that when the solvent was pure DEG and reactant Zn(CH₃COO)₂·2H₂O,the ratio is 43.9 g·cm^-3,also when the solvothermal time and solvothermal temperature were kept at 12 h and 200?,respectively,self-assembled spheres with good dispersibility and uniform particle size can be obtained.Well-dispersible ZnO particles was conducive to the improvement of antibacterial performance.(2)Based on the above solvothermal method,the paper studied the effect of Ce doping on the antibacterial properties of ZnO samples,and characterized the micro crystal structure of the samples.The results showed that Ce doping had no significant effect on the microscopic morphology and dispersibility of ZnO particles.However,through zeta potential,specific surface area and XPS analysis,it was found that Ce doping could increase the zeta potential of ZnO particles.When the Ce doping ratio reaches 5 at.%,the specific surface area were increased19.8%,and the oxygen vacancy concentration increased from 14.0%to 22.6%.The plate count method showed that the number of colonies treated with pure ZnO was more than that of the ZnO sample with 5 at.%Ce doped.The SEM of image bacteria directly reflects the shrinkage and distortion of the bacterial cell membrane.The introduction of Ce element,the larger specific surface area and higher zeta potential of the ZnO sample improved the attraction to the bacterial membrane,and the synergistic effect of metal ions and oxygen vacancies improved the antibacterial properties of the sample.(3)The antibacterial properties of ZnO nanoparticles obtained by precipitation method which coating with well-biocompatible sodium alginate(SA)and further high temperature calcination to obtain amorphous C@ZnO samples with different carbonization degrees were investigated.The results showed that the amorphous C@ZnO calcined at 250?had better antibacterial properties than ZnO samples.SEM,EDS,FTIR,Raman and TG/DTA techniques were used to analyze the micromorphology and elemental composition of the samples before and after calcination.It was confirmed that SA gradually broke from the polymer of high polymer polysaccharide into small molecule block polymer and finally formed amorphous C,after high temperature calcination in an inert environment.Amorphous C groups were enriched in the presence of O-containing groups,and the presence of such amorphous C could promote the antibacterial effect of the particles.The analysis showed that with the further increase of calcination temperature,the graphitization degree of the products calcined by SA will increase,and the disorder of the carbon coating will be weakened.Meanwhile,the high temperature calcination will reduce the defects of the ZnO lattice and the carbon structure,affect the generation of oxygen vacancy and form large particle aggregates,thus affecting the antibacterial properties of the particles.The C@ZnO sample obtained by calcination at 250?had the synergistic antibacterial effect of amorphous carbon and zinc oxide,which improved the antibacterial effect of the sample.