Efficient formation of au nanoparticles and Fe2O3/Au@SiO2 nanocomposite: Effect of functional alkoxysilanes

Glycidoxypropyltrimethoxysilane (GPTMS) was employed, for the first time, as a new sonochemical promoter for the synthesis of gold nanoparticles (NPs) as well as γ-Fe₂O₃/Au@SiO₂ nanocomposites. In either case, GPTMS shows higher efficiency at reduction rate of Au(III) than conventional radial scavengers (alcohols), which is likely attributed to a cascade to generate 4-folds higher amount of alcoholic products during hydrolysis. Gold NPs were successfully attached to the surface of γ-Fe₂O₃ cores during the process of nucleation and growth of gold NPs, forming gold islands. The ratio of γ-Fe₂O₃/Au was estimated to be 4.0, which is ~3-folds higher than that obtained from a two-step conjugation procedure of γ-Fe₂O₃/thiol-silane/Au. The effect of other frequently used silane reagents was also investigated. A relatively lower ratio of Au/γ-Fe₂O₃ was obtained by using tetraethyl orthosilicate or PEG-silane, while such reduction reaction was remarkably quenched by amine- or thiol-silane reagents. The mechanism of quenching was depicted.