Template synthesis and characterization of gold nano-wires and -particles in mesoporous channels of FSM-16

Template synthesis of gold nano-wire and -particle onto mesoporous silica FSM-16 (Au/FSM-16) has been studied. Several Au/FSM-16 samples were prepared by chemical vapor deposition (CVD) or impregnation methods with subsequent reduction procedures. Organogold complex, dimethyl(hexafluoroacetylacetoato)gold(III) AuMe2(HFA), was adsorbed on FSM-16 by CVD, then irradiated by UV light, leading to the formation of Au nano-wires (diameter, 2.5 nm; mean length, 17.1 nm) in one-dimensional channels of FSM-16 (pore diameter, 2.7 nm). On the other hand, HAuCl4 in aqueous solutions at various pH's was impregnated on FSM-16. The impregnated sample Au3+/FSM-16 prepared at pH 5 was reduced by H-2 at 673 K to give a mixture of An nano-wires and -particles. In contrast, H-2-reduction of Au3+/FSM-16 impregnated at pH 10 only gave homogeneously dispersed Au nano-particles in FSM-16 (mean diameter 1.7 nm). The size and morphology of the nanostructured Au metal is changed by pH of the aqueous HAuCl4 solutions. The Au nano-wires and -particles were characterized by physicochemical methods such as TEM, XRD, EXAFS, and diffuse-reflectance UV-visible. CO oxidation was performed as a catalytic test reaction for the Au/FSM-16 composites. (C) 2003 Elsevier Science B.V. All rights reserved.