Synthesis of mesoporous silica hollow spheres in supercritical CO2/water systems

Abstract

The synthesis of hollow silica spheres with mesopore wall structures via CO₂-in-water emulsion templating in the presence of non-ionic PEO-PPO-PEO block copolymer surfactants as mesostructure-directing templates has been investigated under various conditions. The successful synthesis of hollow spheres strongly depends on the pressure and density of CO₂. The mesoporosity (pore size) and morphology of the silica hollow spheres can be controlled by varying the operating CO₂ pressure. Other types of surfactants, such as long chain alkylammonium ions, may also be used to template the porosity of the shells.