Formation of hollow silica spheres from molecular silica sols

Hollow silica microspheres have been obtained in a surfactantfree templating process at neutral pH from silica sol of 2–10nm globular organic–inorganic silica particles with exposed hydrophobic siloxane part as well as hydrophilic reactive silanol groups. Due to small diffusion coefficient and amphiphilic nature, the sol particles stabilize an oil–water interface quickly. Initially they assemble via noncovalent interaction into a stable shell and then condense covalently, with fast initial stabilization/dispersion of oil–water emulsion improving the control and simplifying the microsphere formation process.