ZnO And Ag/ZnO Nanocomposites: Design,Preparation And Application

In recent years,environment pollution has been an important issue in our everday’s life.The application of semiconductor nanomaterials in photocatalysis,especially in solving einviroment pollution,has attracted wide attention in the research field.Nano-ZnO is a kind of semiconductor material,successfully used in solar cells,photocatalysis and antibacterial fields because of its simple preparation method,low cost and tunalbe structure.In this paper,firsly the ZnO nanomaterials with controlled morphologies were prepared by a feasible method.Then,the Ag /ZnO nanocomposites were fabricated by the typical wetness impregnation method.Finally,their photocatalytic and antimicrobial properties were investigated as follows:(1)The preparation methods of ZnO nanomaterials with different morphologies and Ag/ZnO nanocomposites were studied.The tetrapod-like ZnO was prepared by chemical vapor deposition with Zinc powder as raw materials.The flower and rod-shaped nano-ZnO were prepared by hydrothermal method using zinc acetate as precusors.The silver nanoparticles were prepared by the seed growth and in situ reduction method.The silver nanoparticles prepared by the reduction method were uniform in size about 20-30 nm.The as-prepared Ag nanoparticles were supported on nano-ZnO by simple wetness impregnation method.Their detailed structures and morphologies were characterized by SEM,TEM and XRD.(2)The photocatalytic degradation of methyl orange solution in tetrapod-like ZnO was studied,including the optimum photocatalyst concentration and catalyst recycling.The results showed that the optimum photocatalytic concentration of tetrapod ZnO was 0.300 g·L-1,and the degradation rate of ZnO was not obviously changed after 2 cycles,indicating that tetrapod-like ZnO had very good photocatalytic stability.The photocatalytic performance of tetrapod-like ZnO,Ag and Ag/ZnO was evaluated.The results showed that the silver nanoparticles had no obvious catalytic performance on the photocatalytic degradation of methyl orange.The photocatalytic performance of Ag/ZnO nanocomposite is not significantlyimproved comparing with that of pure tetrapod-like ZnO.It was found that the tetrapod-like ZnO with branched structure reduces the intermolecular agglomeration,the surface of the existence of more reactive sites and oxygen defects,which can capture more light electrons make it have high photocatalytic activity.After supporting Ag nanoparticles,the Ag nanoparticels take-up parts of the active ZnO suface,resulting in the reduction of the photocatalytic performance of tetrapod-like ZnO.(3)The antibacterial properties of ZnO,Ag and Ag/ZnO under non-light conditions and under light conditions were studied.The antibacterial results showed that Ag/ZnO> Ag> ZnO was observed under non-light conditions and under light conditions.This may be mainly due to Ag nanoparticles with smaller size,large surface area,active sites and more easily adsorbed to the bacterial cell wall and damaged cell wall,so as to achieve the purpose of inhibiting or killing bacteria.