title: Filling double-walled carbon nanotubes with WO3 and W nanowires via confined chemical reactions.
abstract: Carbon nanotubes filled with metals and semiconductors have been regarded as one of the most promising materials for nanodevices. Here, we demonstrate a simple and effective method to produce tungsten trioxide (WO3) and tungsten (W) nanowires with diameters of below 4 nm inside double-walled carbon nanotubes (DWCNTs). First, the precursors, i.e., phosphotungstic acid (HPW, H3PW12O40) molecules, are successfully introduced into DWCNTs. Subsequent decomposition and reduction lead to the formation of WO3 and W nanowires inside DWCNTs. The products were carefully characterized by high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. FTIR spectra provide a direct proof that the HPW molecules enter the DWCNTs as an ionic state, i.e., PW12O40(3-) and H+, instead of the molecular state. HRTEM analysis shows that the diameter of the WO3 nanowires inside DWCNTs is 1.1-2.4 nm with the average length of 16-18 nm, and that for W nanowires is 1.2-3.4 nm with the average length of 15-17 nm. Meanwhile, DWCNTs are doped by the encapsulated WO3 and W nanowires. Tangential band shift in Raman spectra revealed the charge transfer between the nanowires and carbon nanotubes.
authors: Department of Chemistry, Renmin University of China, Beijing 100872, China.
authors: Keke
authors: K
authors: Zhao
authors: Zhiyong
authors: Z
authors: Wang
authors: Zujin
authors: Z
authors: Shi
authors: Zhennan
authors: Z
authors: Gu
authors: Zhaoxia
authors: Z
authors: Jinj
mesh_terms: D003460:Crystallization / Q000379:methods*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000648:ultrastructure*; D010087:Oxides / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties; D014414:Tungsten / Q000737:chemistry*
chemical_list: D046911:Macromolecular Substances; D037742:Nanotubes, Carbon; D010087:Oxides; C511604:tungsten oxide; D014414:Tungsten