Study Of Synthesis And Structural Control Of Nano-sized Au Catalysts And Its Properties

Gold nanoparticles have attracted extensive attention because of their high catalytic reactivity and selectivity. In this paper, gold nanocatalysts were prepared by using hydrothermal synthesis method, self-assembly method and template method. And their catalytic activity and electrocatalytic activity have also been studied. The main contents are listed as follows:1) A facile, two-step strategy has been utilized for anchoring gold nanoparticles (AuNPs) onto the surface of graphene oxide (GO) nanosheets by simply adding some specific electrolyte solution into GO suspension in the presence of gold colloid. And then we could get a relative "clean" Au/GO with different NP aggregates. The results showed that the immobilized Au NPs display a maximum number of exposed "active-sites" due to the absence of any other surfactants or protecting ligands on their surfaces and therefore superb catalytic activities for the reduction. Interestingly the reduction rate catalyzed by Au/GO nanocomposites in small aggregates is faster than that in large ones, suggesting the aggregate size has a significant impact on catalytic activity.2) Seed-induced method was used to hydrothermal synthesis of a series of gold nanoparticles with the controllable size, different morphology. The morphologies include the triangle, square, hexagon and quadrangle. The size and morphology of samples were examined by transmission electron microscope. Our studies mainly focus on the effect of size and morphology on catalytic properties. The catalytic activity as follows:triangle Au>cubic Au>hexagon Au>quadrangular Au. The results showed that the small size and anisotropy effect all have a great impact on the catalytic activity of Au nanoparticles.3) Sol-gel derived silica was used to be coated onto gold colloidal materials to form core-shell structures. And then we chose the "surface-protected etching" process to etch of material from the interior of the particles. The surface-protected etching process allows the precise control of the openings of the silica shells, therefore, the permeability and time of the reagents through the shells, and eventually the kinetics of the catalytic reactions. In addition, the catalytic activity of porous core-shell Au@SiO2spheres was still very high after placing a long time because the porous shells continue to act as effective barriers against aggregation and loss of activity of the core particles. The decrease of catalytic activity of uncoated Au nanoparticles after placing a long time, which can be naturally attributed to the significantly reduced surface area as the result of aggregation of catalyst particles reaction.4) Polyhedral gold nanoparticles was synthesis by a modified polyol process in the presence of poly(vinyl pyrrolidone)(PVP). The use of1,4-butanediol (BD) as a solvent is very effective for the shape evolution of gold nanocrystals at high temperature. In this paper, we studied the electrocatalytic activity of polyhedral gold nanoparticles, Au/GO and Au-Ag/GO nanocomposites. The results showed the Au-Ag/GO nanocomposites modified electrodes exhibited more active than Au/GO nanocomposites toward p-nitrophenol electrochemical reduction reaction and polyhedral gold nanoparticles modified electrodes also have electrocatalytic activity toward p-nitrophenol. The signal intensity of different concentrations of p-nitrophenol was not the same and it can be used as an electrochemical sensor for detection of nitro phenol.