Controlled Synthesis And Characterization Of Noble Metal Nanoparticles

Noble metal nanoparticles are particularly important because their stability and fascinating optical properties can tuned through control over particles size, shape, composition and morphology. It is believed that large-scale size- and shape-controlled metal nanoparticles will be conveniently produced through further optimization of these synthetic processes and expected to find intriguing applications in field such as catalysis, biosensor, recording media, and optics. The main goal of this dissertation research was to synthesis various morphologies of noble metal nanoparticles and characters their structures, composition and properties.The main results of this thesis are outlined as follows:The first part of this thesis presents an electrochemical method for synthesizing triangular gold nanoplates and branched gold nanocrystals in the form of colloidal suspension. By introducing a small amount of additive, various shapes of gold nanoparticles were obtained. Herein, single crystal triangular and hexagonal gold nanoplates were easily synthesized in solution through the addition of H₂PtCl₆ to a conventional electrochemical synthesis. Similarly, branched gold nanocrystals were easily synthesized in solution through the addition of NaOH to a conventional electrochemical synthesis. We consider that H₂PtCl₆ and NaOH play an important role in the forming process of the branched structure. This electrochemical-mediated route has led to a colloid with unusual optical properties that directly relate to particle shape and size. These works provide a demonstration of the use of electrolysis as a tool to provide control over nanoparticles growth and particles size and shape.The second part of this thesis demonstrates an electrochemical method for preparing Au-Ag alloy nanoparticles in the aqueous solution. Gold-silver alloy nanoparticles with various mole ratios were synthesized in aqueous solution by an electrochemical co-reduction of HAuCl₄ and silver nitrate AgNO₃ in the presence of poly(vinyl-pyrrolidone) (PVP) used as protecting agent. The UV-vis absorption...