Structural characterization of single crystals of sodium titanate nanowires prepared by hydrothermal process

Na2Ti6O13 nanowires have been synthesized using a simple hydrothermal reaction at 130 degrees C between TiO2 particles and NaOH aqueous solution. Subsequently the samples were annealed at 500 degrees C in air for 24 h. Field emission scanning electron microscope(FEG-SEM) and low-magnification transmission electron microscope(TEM) inspection showed wire-like structures with uniform diameters and high contrast, indicating the formation of single crystals. High-resolution transmission electron microscope(HRTEM) and 2-D fast Fourier transform confirmed that the annealed structures correspond to hexatitanate single crystals with diameters between 20 and 120 nm and lengths ranging from 500 nm to 1 mu m. Structural characterization was performed by X-ray diffraction(XRD) and Raman spectroscopy. Annealed samples presented diffraction patterns and Raman vibrational spectra corresponding to the sodium hexatitanate indexed as Na2Ti6O13. FEG-SEM and TEM inspection of the synthesized samples without annealing showed belt- and tube-like structures with diameters between 10 and 60 nm and several micrometers in length. However, their crystalline structure could not be determined using the same techniques applied to the annealed samples. (C) 2008 Elsevier B.V. All rights reserved.