Preparation of Hybrid Hollow Silica Particles without Templates

Abstract

Monodisperse hollow organically modified silica (ORMOSIL) particles having precisely controlled sizes were synthesized without using templates via a two-step method in an aqueous alcoholic solution. In the first step, ORMOSIL particles with sizes from 70 to 230 nm were prepared using phenyltrimethoxysilane (PTMS) as a silane source using two step acid-base processes based on sol-gel reaction. Subsequent mild etching of the less condensed core part, made with silsesquioxane networks, in ORMOSIL particles with ethanol produced hollow ORMOSIL particles with controlled size and distribution. The precise control in the size of hollow ORMOSIL particles can be accomplished with the adjustment of the concentration of PTMS in a co-solvent of alcohol and water. Monodisperse size distribution of hollow ORMOSIL particles also can be obtained by manipulating the hydrolysis time, the concentration of acid/base catalysts, and reaction temperature. Composite hollow particles with vinyltrimethoxysilane (VTMS) and 3-mercaptopropyltrimethoxysilane (MPTMS) were produced by changing the various experimental conditions. The size and morphology of hollow ORMOSIL particles were characterized by electron microscopic methods.