Preparation of spherical silica particles by Stober process with high concentration of tetra-ethyl-orthosilicate

In this paper, Stober process with high concentration of tetra-ethyl-orthosilicate (TEOS) up to 1.24 M is used to prepare monodisperse and uniform-size silica particles. The reactions are carried out at [TEOS] = 0.22-1.24 M, low concentrations of ammonia ([NH3] = 0.81 [TEOS]), and [H2O] = 6.25[TEOS] in isopropanol. The solids content in the resulting suspension achieves a maximum value of 7.45% at 1.24 M TEOS. Various-sized particles in the range of 30-1000 nm are synthesized. The influences of TEOS, NH3, and H2O on the size and size distribution of the particles are discussed. A modified monomer addition model combined with aggregation model is proposed to analyze the formation mechanism of silica particles. (C) 2009 Elsevier Inc. All rights reserved.