Synthesis and characterization of one-dimensional WO2 nanorods

Abstract

One-dimensional (1D) WO 2 nanorods were synthesized by hot-filament metal vapor deposition at high-pressure Ar flow without using any catalyst. The 1D WO 2 nanorods grew on the roots and were a few micrometers long and 50 – 100 nm wide. The x-ray diffractionpattern shows that the as-synthesized 1D WO 2 nanorods are the monoclinic structure in space group P 2 1 ∕ c , and the roots are the β tungsten crystal of the cubic structure in space group Im 3 m . Field-emission-gun transmission electron microscopy images and selected-area electron diffractionpatterns further confirm that the monoclinic 1D WO 2 nanorods consist of the (011) planes and preferentially grow along the ⟨ 0 1 ¯ 1 ⟩ direction. According to these results, an uncatalyzed vapor-solid process is suggested to be the mechanism of growth of the as-synthesized 1D WO 2 nanorods. In comparison with the Raman scattering of three-dimensional WO 2 bulk powders, the Raman bands of the 1D WO 2 nanorod are blueshifted and narrower, indicating phonon confinement associated with the 1D WO 2 nanorod.