Easily recyclable and highly active rice roll-like Au/SiO2 nanocatalysts from inverse miniemulsion

Rice roll-like (RR-like) Au/SiO 2 nanocatalysts (NCs) were synthesized through simultaneous sol–gel process of tetramethoxysilane and 3-aminopropyltriethoxysilane (APTES) and in situ reduction of gold salt in inverse miniemulsions. APTES played an important role in formation of RR-like SiO 2 nano-supports, reduction of gold salts to narrowly size-distributed sub–10   nm Au nanoparticles (NPs), and improved attachment of Au NPs to the SiO 2 nano-supports. The prepared RR-like Au/SiO 2 NCs displayed a pH-dependent, reversible colloidal stability in water, which facilitated to recycle them through tuning the pH value of the dispersion. Most importantly, the catalytic activity of the RR-like Au/SiO 2 NCs towards reduction of p -nitrophenol was about 7–9 times higher than that of the raspberry-like Au/SiO 2 NCs reported in our previous paper (Colloids Surf. A, 489, 2016, 223–233). The formation mechanism of the RR-like Au/SiO 2 NCs was also discussed.