Synthesis of nanotubes from mesoporous nanocrystalline titanium dioxide

Mesoporous nanocrystalline TiO2 (the anatase phase with spherical crystallites smaller than 10 nm and with the pore diameter larger than 17 nm) is obtained by the sol-gel synthesis followed by a hydrothermal treatment. It is used for the fabrication of titanate nanotubes using the hydrothermal process in a concentrated aqueous NaOH solution at 130 oC. The SEM, TEM, XRD, and nitrogen adsorption-desorption methods were used to study the texture and morphology of new materials. Uniform nanotubular open-ended particles characterized by an average outer diameter of about 8 nm and a length larger than 1 μm are observed. The particles are assembled into bundles about 64 nm in diameter, and the bundles were also aggregated. The calcination of titanate nanotubes in air at 300 oC gave rise to the formation of the anatase phase (the size of crystallite was 5.7 nm), which was accompanied by a reduction of the specimen specific surface area from 255 to 190 m2/g.