Needle-like calcium carbonate assisted self-assembly of mesostructured hollow silica nanotubes

Mesostructured hollow silica nanotubes (MHSNTs) were successfully produced via the self-assembly of C16TMABr and silica species on the surface of needle-like calcium carbonate nanoparticles in an alkaline medium at room temperature. The characterization of MHSNTs by transmission electron microscopy (TEM), scanning electron microscopy (SEM), pore size distribution (PSD) and Brunauer–Emmett–Teller (BET) indicated that MHSNTs had uniform tubular hollow structures with big openings, a length of 1.5–2.0 μm, an inner diameter of 150–200 nm at the open end and 50–60 nm at the closed end, and a wall thickness of 20–30 nm, as well as a narrow PSD around 2.3 nm in the shells and a BET surface area as high as ∼975.3 m2/g. By small-angle X-ray diffraction (XRD), BET and pore structure analysis, it was found that more uniformly structured mesopores could be formed by the method of removing the double templates simultaneously through a solvent extraction process, as compared to the separate removal of the double templates by calcinating and then etching in an acidic solution, and the amount of C16TMABr affected the mesoporous structures of MHSNTs greatly. The formation processes of MHSNTs were also studied with XRD and FTIR.