Preparation of core-shell structured Au@SiO2 nanocomposite catalyst with Au core size below 2 nm without high-temperature calcination procedure

Preparing dispersed cores-shell structured Au@SiO2 nanocomposites with an active Au core size below 2 nm that exhibit excellent catalytic performance still remains a major challenge in catalytic synthesis. In this work, we report a novel preparation method for a one-pot system fabrication of an ultrafine core-shell structured Au@SiO2 intestine-shaped nanocomposite. The preparation is used to fabricate catalysts with an Au core size of about 1.4 nm and requires neither prefabricated Au cores nor special reducing agents. Upon extraction of cetyltrimethylammonium bromide, abundant pores with a size of around 1.9 nm are formed in the silica shell. During the catalytic reduction of 4-nitrophenol to 4-aminophenolate, the catalyst unambiguously exhibits superior catalytic activity. Despite having a low 1.7% Au content in catalyst, the nanocomposites achieve an activity of ES = 19.1 x 10(-3) s(-1) mg(-1). This is due to the fact that the polyvinylpyrrolidone coating is transformed into discrete particles in an alkaline solution, which exposes large active areas on the Au.