Preparation of silica nanoparticles: determination of the optimal synthesis conditions for small and uniform particles

Abstract

Silica nanoparticles were prepared from tetraethylortho-silicate (TEOS) dissolved in ethanol by using a semi-batch process in order to control the particle properties. In this work, the statistical experimental method was also used to compare the properties (particle size and SD) of the SiO2 particles according to the four parameters (R=[H2O]/[TEOS]), concentration of ammonia (NH3), the feed rate of reactant, reaction temperature]. We have obtained monodispersed silica particles having size ranging from 10 to 350 nm by our experiment. It was found that the optimal synthesis conditions for the preparation of SiO2 nanoparticles with narrow size distribution in semi-batch process were as follows; (R=[H2O]/[TEOS], 30–55; concentration of ammonia (NH3), 0.2–0.35 mole l−1; feed rate of reactant, 13–17 cm3 min−1; reaction temperature, 55–65°C). The above-mentioned optimal conditions were used to prepare the particles with minimum particle size (30 nm) and its SD (<±5 nm), simultaneously. Experimental results measured by using the optimal synthesis conditions were in a good agreement with simulated value and the smallest size (∼10 nm in diameter) was obtained. Also, we found that the effect of parameters on the particle size and SD in the preparation of SiO2 nanoparticles was increased in the following order; reaction temperature, (R=[H2O]/[TEOS]); concentration of ammonia (NH3), feed rate of reactant.