Aging effect of starting solutions for spherical silica synthesis

Particular attention was paid to the "aging" of starting solution for synthesis of spherical silica by a controlled hydrolysis of alkoxide. Two starting solutions, i.e., an ethanol solution of tetraethylorthosilicate (TEOS) and an ethanol solution of ammonia water, were aged and then mixed to synthesize spheres. Sufficient aging (∼a week) of the starting solutions resulted in larger sphere size and higher monodispersibility. We infer here that solute molecules are not homogeneously dispersed in the as-dissolved solution even though they appear to be clearly dissolved.