The Controlled Synthesis Of Noble Metal Nanoparticles And Their Properties In Optic And Catalytic Field

Noble metal nanoparticles have potential applications in many fields, such as catalysis, biosystem, energy and environment. The properties and applications of noble metal nanoparticles have strong dependence on their structure, shape and size. Therefore, the controlled synthesis of noble metal nanoparticles has been extensively pursued. In this dissertation, based on seeding-growth, noble metal nanoparticles with various shapes, structures and sizes were synthesized and new mechanism was proposed. Furthermore, their optic and catalytic properties were studied. The main research work is listed as following:(1) Through using seeding-growth and galvanic reaction, hollow AuAg@Au nanoparticles with alloy core (HNACs) have been prepared. Through adjusting the core size, the amount of HAuCl4, and the diameter of Au@Ag, the fabrications of various HNACs were achieved. Also a new galvanic reaction process was proposed based on careful observation. By using 2-Naphthalenethiol as a probe molecule to investigate their SERS activity and the results demonstrated their good performance.(2) The Pt nanoparticles (NPs) with controlled shape and size were synthesized by using seeding-growth. By adjusting the reactive conditions, such as the molar ratio of Pt metals from Pt(acac)₂ and seed, the seed diameter, the NPs growth could be controlled to give variously shaped NPs. A reasonable mechanism in which the NP shape is c/s-dependent (c=concentration of precursor, s=total surface area of NPs) was figured out to explain shape evolution process successfully. The prepared Pt NPs were further tested for catalytic oxidization of methanol and results demonstrated that their shapes have great impact on catalytic properties, and the branched Pt nanoparticles showed the greatest catalytic performance.(3) By using the oxide nanoparticles (Mn₃O₄) as catalyst and modifying reactive conditions, rarely-observed polycrystalline twinned Pt nanoparticles (NPs) and single crystalline nanorod could be synthesized. A possible mechanism was proposed that the Mn₃O₄ nanoparticles were not consisted in the Pt nanoparticles, instead just as a catalyst or a modifier of catalyst contributing to the form of Pt polycatalline or rod-like nanoparticles. In addition, high index facets with high density were observed on the edge of Pt nanorod, which can improve the catalytic performance in the electroxidation of methanol. Besides, such nanostructure can be further developed to be more applicable nanocatalysts with high efficiency.