Influence of synthesis parameters on particle properties and catalytic activity of rice roll-like Au/SiO2 nanocatalysts prepared in inverse miniemulsions

In our previous paper, we reported the synthesis of easily recyclable and highly active rice roll-like (RR-like) Au/SiO 2 nanocatalysts (NCs) in inverse miniemulsions [Colloids Surf. A 517, 2017, 52–62]. In the present contribution, the influences of three key synthesis parameters, including the 3-aminopropyltriethoxysilane (APTES) content, reaction temperature, and urea amount, on the particle properties of the Au/SiO 2 NCs were systematically investigated. The role of these synthesis parameters in the formation of SiO 2 nanosupports and Au nanoparticles (NPs) was discovered. The RR-like SiO 2 nanosupports could only be formed in the systems within the range of 20–80   mol% of APTES content, at reaction temperatures above 60   °C, and with more than 0.72   mg of urea. The AuCl 4 − ions could be immobilized onto the aminopropyl-functionalized SiO 2 nanosupports through a coordination interaction. The immobilized ions were reduced by the aminopropyl groups at elevated temperatures. The APTES content and reaction temperature play an important role in controlling the particle size and its distribution of Au NPs. The catalytic activity of Au/SiO 2 NCs depends significantly on the APTES content. The RR-like Au/SiO 2 NCs with smaller immobilized Au NPs and higher specific surface area display higher catalytic activity towards hydrogenation of p -nitrophenol.