Preparation of Silica Nanoparticles using Microemulsion Techniques

Abstract

Silica nanoparticles have been prepared in this work using water in oil (W/O) emulsion system at room temperature that employs a water-soluble amine as catalyst and tetraethylorthosilicate (TEOS) as the silica source. The pH value of the aqueous phase and the water: surfactant ratio were found to be the key factors contributing to the formation and final size of stable and regular spherical silica particles. When the pH value of the aqueous phase was controlled between 8 and 9, silica particles could be synthesized. The shell thickness of the hollow particles as and when prepared was found to increase with the length of the hydrocarbon tail of the amine catalyst. The viscosity of the external oil phase determined the shape regularity of the spherical silica hollow particles. The kinetics of the formation of silica hollow particles was believed to be based on the difference between the hydrolysis rate and the condensation rate of TEOS, which can be adjusted by the pH value of the aqueous phase. After treating the core-shell particles with concentric nitric acid, the hollow silica spheres were obtained correspondingly. The particles were characterized by Scanning electron Microscope (SEM), Optical Microscope and UV Spectrophotometer. The study shows that through further processing, advanced materials could be prepared; and that the hollow silica spheres could be potentially used as a novel class of catalyst supports.