The morphology and size of nanostructured Au in Au/SBA-15 affected by preparation conditions

Template-free mesoporous silica SBA-15 was reacted with TPTAC to generate positively charged functional groups PTA+ on the pore surface. Through ion exchange, a uniform distribution of anionic metal complexes on the intrachannel surface of host silica was achieved. In this study, ethanol and water were used as solvent for HAuCl4 precursor solutions impregnated on SBA-15 mesoporous silica. The solvent used can affect the size and location of the resulting nanoparticles. Large Au nanoparticles (15–43 nm) were found on the as-prepared Au/SBA-15 as observed by PXRD, XAS, UV–vis and TEM. This may have originated through Si–OH reduction of chloroaurate complexes generated in the aqueous solution of HAuCl4, and such particles were not present when ethanolic solution was used. After NaBH4 and H2 reduction, the average size of Au nanoparticles, which was incorporated into the channels of SBA-15, was found to be limited to ≤  7 nm.