A facile method to fabricate silica-coated carbon nanotubes and silica nanotubes from carbon nanotubes templates

Silica-coated multiwalled carbon nanotubes (MWCNTs) have been prepared by the sol-gel polymerization of tetraethoxysilane (TEOS) in the presence of the acid-oxidized MWCNTs at room temperature, followed by oxidizing the MWCNTs templates at high temperature in air to produce hollow silica nanotubes. The thickness and architectures of silica shell were well controlled by rationally adjusting the concentration of TEOS, and by adding cationic surfactant as a structure-directing agent. These results also give a clear answer to prove the fact that the structures of spherical silica particles can be fully "copied" to the coating shell and the wall of silica nanotubes when prepared by the same method as the synthesis of silica particles in the presence of templates.