Self-assembly Of Gold And Platinum Particles And Studies On Their Electrocatalysis Properties

Nanometer materials have been widely used in various fields due to their unique physicochemical properties and good biocompatibility, such as information storage, medical diagnosis, catalysis and sensing. Researches on self-assembly of nanometer materials can not only reveal the interaction mechanisms between nanoparticles to further control the process of nanoparticle self-assembly, but also make for discovering new properties of nanoparticle assemblies. All these studies are necessary for the development and application of nanometer materials. This thesis involves self-assembly of gold, platinum nanoparticles and electro-catalytic properties of some assemblies. The main research contents are as follows:1. Self-assembly of gold nanoparticles.2-mercaptoethylamine serving as coupling agents was added into 3.5-nm Au colloidal solution to fabricate Au nanoparticle assemblies with different nanostructures, such as spherical, annular and valvular, expanding the structure patterns of Au nanoparticle assemblies. The formation of these nanostructures depended on coupling agents concentration, stirring speed, reaction time, ultrasonic intensity and salt concentration. Additionaly, the assembly mechanism was also simply discussed.2. In-situ self-assembly of platinum nanoparticles. Platinum nanoaprticle assemblies were assembled via the self-aggregation of～3.5 nm Pt nanoparticles directly prepared in the polyol process. The assembling process does not involve any linker reagent. Thus, the as-prepared Pt nanoparticle assemblies showed satisfactory electro-catalytic activity for methanol oxidation, which is reasonably attributed to the high activity of Pt nanoparticle surface.3. Assembly of gold and platinum nanoparticles into two-dimensional composite structures. Au nanoparticle monolayer prepared at n-butanol/water interface was used as a substrate, Pt nanoparticles was modified onto Au nanoparticle monolayer by combining under-potential deposition and redox replacement, forming two-dimensional Pt/Au composite film. What's more, (Pt/Au)n multilayer composite structures were also prepared via layer-by-layer assembly of Pt/Au units. The thickness of platinum layers in Pt/Au composite film can be controlled by repeating under-potential deposition and redox replacement procedures. Thus, Ptm/Au and (Ptm/Au)k multilayer composite films were also fabricated. All as-prepared composite films were used as anode catalysts for methanol electro-oxidation. The results showed that the catalytic efficiency and stability are closely related to the structures of catalyst films. The more interface between Au and Pt nanoparticles in catalyst films are, the better their catalytic efficiency and stability are. The structure of (Pt/Au)3 exhibits the best catalytic efficiency among all films, and its poison-resistant capability is 169% of that of commercial Pt/C catalyst.