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

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.