Hydrothermal Conversion of Self-Assembled Titanate Nanotubes into Nanowires in a Revolving Autoclave

Titanate nanowires were synthesized through the hydrothermal synthesis route (10 M NaOH, 130 °C) from anatase in a rotating autoclave. A combined TEM, SEM, XRD, FT−Raman, and N 2 adsorption investigation of the reaction products as a function of time revealed that the 60−150 nm wide and ∼5 μm long nanowires are in fact formed by the merging of self-assembled nanotube bundles. The nanowires are able to further self-assemble into ∼5 μm wide and longer than 30 μm long, dense “superbundles” if the reaction is allowed to run long enough. We propose that the spontaneous nanotube arrangement could be caused by the rotation-assisted oriented attachment of the tubes.