Mechanism of nanoparticle formation in hydrolysis and condensation of tetraethyl orthosilicate

To study the mechanism of nanoparticle formation in dydrolysis and condensa tion of tetraethyl orthosilicate (TEOS), the reaction was performed over a wide range of TEOS concentration (0.01 similar to0.2 mol/dm(3)), water conc entration (5 similar to 20 mol/dm(3)) and ammonia concentration (0.2 simila r to1.5 mol/dm(3)) ill the absence and in the presence of LiCl and KCl as e lectrolytes. Nanoparticle with in average diameter of 23 similar to 100 nm were formed at the lowest ammonia concentration of 0.2 mol/dm(3) in the abs ence of the electrolyte. The effect of electrolyte concentration on Particl e diameter and the measurement of electric conductivity of the reaction sys tem suggest that electrostatic repulsion between Particles precipitated ill the reaction system is the main factor determining final particle size. Th e formation of nanoparticles ill the reaction is explained by all increase in the electrostatic repulsion due to a decrease in ionic strength.