Fast fabrication of hollow silica spheres with thermally stable nanoporous shells

Tens of micrometer-sized hollow silica spheres with thermally stable nanoporous shells were synthesized within 5 min, followed by a drying and a calcination step. Most of the nanopores could be retained up to 700 °C, and the hollow spherical morphology was remained at least until 950 °C. It is proposed that a fast hydrolysis and condensation of tetraethyl orthosilicate take place around multi-lamellar octylamine vesicles. The morphology of the vesicles is then fixed by a quick gelation process, resulting in hollow organo-silica spheres. After the removal of the template by calcination, nanopores are generated in the hollow shells.