Silver-Metal Oxide Composite Nanostructures Synthesis And Their Application In Photoenhanced Antibacterial Properties

Bacteria are microorganisms that can cause deadly infections.Therefore,antibacterial materials are of great significance to human health and safety.Silver nanoparticles and metal oxide nanoparticles are the most widely used two inorganic antibacterial agents,which can kill bacteria by releasing silver ions and producing reactive oxygen species(ROS),respectively.However,it is the agglomeration of silver particles and low ROS production efficiency that seriously limit the further improvement of their antibacterial properties.It is urgent to effectively accelerate the release of silver ions and improve the production efficiency of ROS,so as to enhance the bactericidal performance of bactericide.In this dissertation,silver-metal oxide composite nanostructures are constructed to improve ROS production and ion release through surface plasmon resonance effect,achieving the significantly enhanced antibacterial activity under light irradiation.The main achievements are summarized as follows:(1)Using hexadecyl trimethylammonium chloride as stabilizer,Ag-ZnO core shell nanoparticles were prepared by the liquid phase method.By changing the molar ratio of Zn/Ag,Ag-ZnO core shell nanoparticles of different sizes were obtained.The antibacterial activity of Ag-ZnO nanostructure has been studied,and it was found that the minimum inhibitory concentrations(MIC)of Ag-ZnO against Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)were 9.1 mg L-1 and 18.1 mg L-1,respectively,reduced by 74%and 49%compared to those in the dark,showing a significant photo-enhanced antibacterial effect than that from individual Ag and ZnO nanoparticles.ROS species analysis and ion release study indicated that excellent antibacterial properties of Ag-ZnO core shell nanoparticles were the combined action of photoinduced singlet oxygen and hydroxyl radicals and released zinc ion.(2)Using polyvinyl pyrrolidone(PVP)as stabilizer,Ag-CuO composite nanoparticles were prepared by the liquid phase method.By adjusting the amount of PVP,the optimal synthesis conditions of composites were acquired,namely the molecular weight of PVP was 40000 and the concentration was 0.11 M.Using E.coli and S.aureus as model microorganisms,Ag-CuO nanocomposites showed enhanced antibacterial activity in the dark,when compared to the effects from individual Ag and CuO nanoparticles.Upon the simulated light irradiation for 10 min,dramatically enhanced bactericidal effects of Ag-CuO nanocomposites were achieved,with MIC reduced by 93%and 66%against E.coli and S.aureus respectively.Through the quantitatively measured photo-induced ROS generation and ion release,it was concluded that the observed remarkable photo-enhanced bactericidal performance of Ag-CuO composite nanostructures originated from the concerted action of singlet oxygen and photo accelerating silver ion release.