| Abstrakt: |
The effect of cetyltrimethylammonium bromide (CTAB) template concentration, solvent conditions, and silica source on the structure and self-assembly of mesoporous nanoscale silica/gold composites was investigated. Nanocomposites were analyzed using X-ray diffraction, transmission electron microscopy, and liquid nitrogen adsorption. The number of gold particles per silica shell, referred to as the cluster number, and the ratio of gold/silica to pure silica particles, referred to as the occupancy, varied considerably with the concentration of CTAB template. In addition, the shape of the particles and the direction of mesopore growth were found to depend highly on the solvent composition and the silica source used. The materials produced were thermally stable above 540 °C, had pore volumes greater than 0.53 cm g-1 at standard temperature and pressure, and had surface areas in excess of 690 m2 g-1. The overall particle sizes ranged in diameter from 93 to 520 nm, and the pore center-to-pore center distances of the mesochannels of calcined samples varied from 3.06 to 5.25 nm. From an analysis of the silica mesopore geometry and the position of the gold nanoparticle, a three-stage mechanism for the self-assembly process of the nanocomposites is proposed. |
