Synthesis of Titanate-Based Nanotubes for One-Dimensionally Confined Electrical Properties

Structural tailoring for dimensionally confined electrical properties is fundamentally important for nanodevices and the relevant technologies. Titanate-based nanotubes were taken as a prototype one-dimensional material to study. First, Na0.96H1.04Ti3O7·3.42H2O nanotubes were prepared by a simple hydrothermal condition, which converted into Na0.036H1.964Ti3O7·3.52H2O nanotubes by a subsequent acidic rinsing. Systematic sample characterization using combined techniques of X-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, electron paramagnetic resonance, Fourier transform infrared spectroscopy, elemental analyses, and alternative current impedance indicated that both nanotubes possessed a scrolled trititanate-type structure with the (200) crystal face predominant on the tube surface. With increasing temperature, both nanotubes underwent a continuous dehydration process, which however imposed different impacts on the structures and electrical properties, depending on the types of the nanotubes: (1) the Na0.036H1.964Ti3O7·3.52H2O nanotube converted into anatase-type structure TiO2 nanotubes, while the Na0.96H1.04Ti3O7·3.42H2O nanotube kept the trititanate-type tube structure after calcination at 300 °C; (2) both nanotubes exhibited a maximum conductivity at high temperatures, in which Na0.96H1.04Ti3O7·3.42H2O nanotubes are relatively highly conductive, showing a grain conductivity approximately 2 orders of magnitude larger than that of Na0.036H1.964Ti3O7·3.52H2O nanotubes. These observations were interpreted in terms of the defect chemistry, hydration, and the triple conductive species that were confined in the one-dimensional nanostructures. The findings reported in this work may pave the way for titanate-based nanotubes to find a broad class of technological uses for nanodevices.