Tailored macro/micro structural properties of colloidal silica nanoparticles via microemulsion preparation

Silica nanoparticles were prepared in water in oil microemulsion media using non-ionic surfactant. The mean of reactants incorporation and microemulsion composition were varied in order to study their influence on the macro/microstructure characteristics of the colloids. In particular, different preparations have been performed involving low or high control of the ammonia-catalyzed tetraethoxysilane (TEOS) hydrolysis and condensation reactions. The particles were characterized by electron microscopy, dynamic light scattering and nitrogen sorption. The results showed that monodisperse mesoporous silica colloids can be obtained by controlling the TEOS hydrolysis prior to its introduction in the microemulsion while a direct alkoxysilane monomer addition in the microemulsion leads to bigger silica nanoparticles with no accessible porosity. The hydrolysis controlled preparation procedure gives silica particles which size variation is dependent on the co-surfactant concentration in the microemulsion rather than the water concentration. However, the water concentration in the microemulsion has to be low since it has a dramatic influence on the particles polydispersity. (C) 2005 Elsevier Ltd. All rights reserved.