The Synthesis And Growth Mechanism Of Anisotropic Noble Metal Nanoparticles

Anisotropic noble metal nanoparticles are widely used in the fields of electronics,catalysis, optics, biology and medicine because of their unique physical and chemical properties. After a long period of exploration and research, a variety of synthetic methods have achieved the controllable synthesis of anisotropic noble metal nanoparticles. Among all methods, seed mediated growth, photochemical synthesis, template assisted synthesis and adsorption-oriented synthesis were popular. In order to realize the synthesis of noble metal nanostructures with a higher degree of anisotropy or a more peculiar morphology, it is often necessary to combine several synthetic methods. In this dissertation, the controllable synthesis of Au/Ag/Pt trimetallic nanoparticles with different morphologies, silver nanoplates and Au@Pd nanorings were realized by using various methods, such as seed mediated synthesis, photochemical reduction and template assisted synthesis. Meanwhile,the related synthetic process and synthetic mechanism were studied in detail. The main research content is divided into the following three parts:(1) Anisotropic Au/Ag/Pt trimetallic nanoparticles were synthesized by using [Au decahedra@Pt/Ag alloy nanoring] nanoparticles prepared through selective growth of Pt and Ag on the edges of Au decahedra as seeds and HAuCl4 as precursor. By adjusting the amount of Pt on Au decahedra, the amount of HAuCl4, the amount of ammonia, the amount of AgCl and the reaction temperature in the growth process of Au, we not only realized the control of the morphology of the final products, but also investigated the mechanism of the synthesis of Au/Ag/Pt trimetallic nanoparticles with various morphologies. It was found that the regulation of the amount of Pt on Au decahedra can tune lattice mismatch during Au growth on [Au decahedra@Pt/Ag alloy nanoring] nanoparticles, and effectively control the growth symmetry of nanocrystals.(2) Large sized and uniform Ag nanoplates with high yield were prepared by using small sized Ag nanoplates of high quality synthesized photochemically inducing by LED light as seeds and AgNO3 as precursors under the protection of sodium citrate. Moreover,the effects of light intensity, H2O2 dosage and the amount of sodium citrate on the preparation of seeds and the effects of the amount of sodium citrate, acetonitrile and the seed dispersions on the synthesis of large sized Ag nanoplates were studied.(3) Using Ag nanoplates as templates, ultrathin Au nanorings are synthesized through selective Au epitaxial growth on the edges of Ag nanoplates and subsequent Ag oxidation etching with H2O2. Next, the Au@Pd nanorings were prepared by using Au nanorings as the seeds and H2PdCl4 as precursor. Furthermore, the effect of the reduction speed of Au3+ on the synthesis of Au nanorings and the effects of the amount of H2PdCl4, the amount of ascorbic acid and the reaction temperature on the preparation of Au@Pd nanorings were investigated.