The Controllable Synthesis Of Nanosilver And Its Catalytic Properties

As a kind of noble metal nanoparticles, silver nanoparticles have attracted more and more attention. Due to its unique physical and chemical properties, it has been widely used in optical materials, battery electrode materials, antibacterial materials, catalyst materials, and other fields. However, the various properties of the nano-silver are mainly dependent on its morphology and size. So, currently, controllable preparation of the morphology of nano-silver has become a hot research topic. At present, the success in preparation of nanomaterial controllably is limited. In this presentation, we controlled synthesis of silver nanoparticles with different morphologies successfully by reduction in solvent or in microemulsion respectively. And we designed a simple method to synthesize the silver nanowires by one step.In which, the reagents are dissolved without the control of dropping speed, making the operation more convenient. That is different from the previous reports in which the silver nanowires were synthesized by dropping the reaction solution into another drop by drop. In addition, the optical properties and antibacterial performance of semiconductor such as ZnO will be greatly optimized after being loaded some nano-silver particles according to the reports. In view of all of this, we also synthesized the Ag nanopartical-ZnO porous prism array composite structure by a photoreduction method. The main points could be summarized as follows:Monodisperse spherical silver nanoparticles were prepared by reduction of aqueous AgNO3 in iso-octane/AOT/water system. In which, ascorbic acid was used as reducing agent. Silver nanoparticles prepared by this method with uniform sizes have no agglomeration.Different shapes of silver nanoparticles such as the mixture of triangle, hexagon nanosheet and decanedron; the polyhedron; the hexagon; the chains and the wires of nano-silver were synthesized by reduced AgNO3 in DMF which was as solvent and reducing agent containing the surfactant (PVP) by adjusting the experimental conditions. The results show that the key factor effecting the final morphology of Ag is the ratio of the concentration of AgNO3 and PVP in solution. Furthermore, we used ethylene glycol (EG) instead of DMF as the solvent and reducing agent in order to study the influence of the reducing agent on the morphology of silver nanoparticles. Polyhedron and wires of nano-silver were also obtained by changing the experimental conditions in this solvent. A simple method to fabricate silver nanowires by one step was achieved.The catalysis of silver nanoparticles with different morphologies synthesized above were investigated. The catalytic performance for the reduction of methylene blue (MB) was evaluated. The results show that all the morphologies of silver nanoparticles synthesized by reduction in liquid phase exhibit excellent catalytic efficiency. Among which, the polyhedron is the best one. We further explored the effects of different dosage of nanosilver for the reduction effect of methylene blue and the possible mechanism of catalytic reaction. On the other hand, the silver nanoparticles prepared in microemulsion did not show obvious catalytic effect.Hiercrchical structure Ag-ZnO prism array were prepared by photosynthesis approach in which the ZnO was initially dipped in aqueous solution of AgNO3 and then illuminated by UV. The quantity and the size of silver nanoparticles deposited on ZnO sprism arrays can be controlled in this method and the operation is simple.