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 SiO 2 particles according to the four parameters ( R=[H 2O]/[TEOS]), concentration of ammonia (NH 3), 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 SiO 2 nanoparticles with narrow size distribution in semi-batch process were as follows; ( R=[H 2O]/[TEOS], 30–55; concentration of ammonia (NH 3), 0.2–0.35 mole l −1; feed rate of reactant, 13–17 cm 3 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 SiO 2 nanoparticles was increased in the following order; reaction temperature, ( R=[H 2O]/[TEOS]); concentration of ammonia (NH 3), feed rate of reactant.