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/SiO2 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/SiO2 NCs were systematically investigated. The role of these synthesis parameters in the formation of SiO2 nanosupports and Au nanoparticles (NPs) was discovered. The RR-like SiO2 nanosupports could only be formed in the systems within the range of 20-80 mol% of APTES content, at reaction temperatures above 60 degrees C, and with more than 0.72 mg of urea. The AuCl4- ions could be immobilized onto the aminopropyl-functionalized SiO2 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/SiO2 NCs depends significantly on the APTES content. The RR-like Au/SiO2 NCs with smaller immobilized Au NPs and higher specific surface area display higher catalytic activity towards hydrogenation of p-nitrophenol.