The Preparation, Mechanism Of Noble Metal Nanoparticles And Theie Catalytic Performance Study

Noble metal nanostructures have promising applications in industrial catalysis, biology, medical, energy and environment. Because their properties are closely related to the structure, morphology and size, the controllable preparation attracted much attention. In this paper, based on colloid chemical synthesis, a variety of precious metal nanoparticles with different structures were prepared and growth mechanism was studied. Moreover, their optical and catalytic properties were investigated.Pt-Sn bimetallic nanoparticles were prepared by colloidal synthesis method. Through controlling the reaction conditions (the amount of precursor, reaction temperature and the kinds of organic ligands), various structured and sized bimetallic Pt-Sn nanoparticles could be prepared.Further, the prepared Pt-Sn bimetallic nanoparticles were used as seeds for synthesizing size controlled Pt-Sn@Pt core-shell structure. Above prepared bimetallic nanostructures were applied to the catalytic oxidation of methanol.The preparation of Au nanostructures with controlled size and morphology through using polyol reduction. By adjusting the reaction conditions (the amount of silver nitrate, reaction temperature, reaction time), Au nanostructures with various shapes (octahedron, decahedra, nanobipyramids, nanorods) were synthesized. Further, the possible growth mechanism was investigated. It was found that the AgNO3could hinder the growth of gold nanorods along [110]. With the increaseing of the amount of AgNO3, Au nanorods became short. An excess of AgNO3could even completely prevent the growth of Au nanorods, resulting in the formation of decahedra. For the reduction of nitro phenol, results showed that the catalytic performance had strong dependence on shape and size.The effect of AgX (X=Cl-、Br-、I-) on the growth of Au nanostructures. When PDDA without X ions was used for preparation of Au nanostrucutre, we found that the growth of Au nanostructures was affected strongly. As well as Cl ion, Br ion favors the formation of Au decahedra. However, because I ion has strong etching effect on twinned face and affinity with Au, both polycrystalline and single crystalline Au nanostructures were observed when I ion was present.A possible mechanism was figured out. The effect of AgNO3on the growth of Au nanostructures very possibly is due to the selective absorption of AgX on specific facet instead of Ag-under-potential-deposition.