Novel and simple synthesis of hollow porous silica fibers with hierarchical structure using silk as template

A novel and simple approach to synthesize the hollow porous silica fibers with hierarchical structure had been proposed, in which natural silk fiber was used as template with the aid of supercritical CO2. Supercritical CO2 can be used to proceed with coating, during which silica precursor (TEOS) dissolved in supercritical CO2 and the supercritical CO2 was in contact with the silk templates. After removal of silk templates by calcinations, the final silica fiber materials replicate not only macroscopic alignment structure along the silk direction, but also microscopic porous structure on the surface of silk. We have shown that it is possible to tune the diameter, wall thickness, and the porous structure of the tube-like silica fibers by varying the pressure and temperature of the supercritical CO2.