Mechanism of nanoparticle formation in hydrolysis and condensation of tetraethyl orthosilicate

To study the mechanism of nanoparticle formation in hydrolysis and condensation of tetraethyl orthosilicate (TEOS), the reaction was performed over a wide range of TEOS concentration (0.01-0.2 mol/dm ³), water concentration (5-20 mol/dm ³) and ammonia concentration (0.2-1.5 mol/dm ³) in the absence and in the presence of LiCl and KC1 as electrolytes. Nanoparticles with an average diameter of 23-100 nm were formed at the lowest ammonia concentration of 0.2 mol/dm ³ in the absence of the electrolytes. The effect of electrolyte concentration on particle diameter and the measurement of electric conductivity of the reaction system suggest that electrostatic repulsion between particles precipitated in the reaction system is the main factor determining final particle size. The formation of nanoparticles in the reaction is explained by an increase in the electrostatic repulsion due to a decrease in ionic strength.