Synthesis of tungsten oxide nanowires Zongwen Liu * , Yoshio Bando, Chengchun Tang Advanced Materials Laboratory, National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan Received 27 November 2002; in final form 2 March 2003 Abstract Tungsten oxide nanowires have been prepared by heating a tiny tungsten wire partly wrapped with melted born oxide (B 2 O 3 ) vitreous powder at 1600 °C in nitrogen atmosphere. The nanowires exhibit a well crystallized one-di- mensional structure with 10–30 nm in diameter and 2–5 lm in length. A monoclinic crystalline structure could be established by high-resolution transmission electron microscopy study. Ó 2003 Elsevier Science B.V. All rights reserved. 1. Introduction Various tungsten oxides (WO 3 ; WO 2 and WO 3x )havelongbeenstudiedandwidelyusedin manyapplications.WO 3 hasbeenusedtoconstruct electrochromic windows [1–3], optical devises [4], gassensors[5–7]andasphotocatalyst[8].Theox- ygen reduced sub-stoichiometric tungsten oxides also display promising physical and chemical properties,suchasthesuperconductivityofWO 3v plate-like sheet particles [9] and the catalytic ac- tivityofWO 2 crystal[10,11].Manymethods,such as laser vaporization [12,13], chemical vapor de- position [14], and electrochemical deposition [15], have been successfully used to prepare various tungstenoxideswithfineparticlesorthinlayers. Since tungsten oxide nanomaterials exhibit su- perior properties in some promising applications compared with those of bulk materials, the syn- thesis of one-dimensional tungsten oxide nano- structures is of special interest and of great importance. By heating a tungsten foil partly cov- eredwithaSiO 2 plateinAratmosphereat1600 °C, Zhu et al. [16] synthesized micrometer-size tung- sten oxide structures with a tree-like morphology. Themicro-size ÔtreesÕ canbebrokenintosegments of nano-size one-dimensional needles. Using a so- nochemicalapproach,Koltypinetal.[17]prepared amorphous tungsten oxide nanoparticles, and then, a WO 2 –WO 3 mixture with nanorod-like structure was obtained by heating the amorphous powder under Ar at 1000 °C. Tungsten trioxide (WO 3 ) nanorods have also been prepared by car- bonnanotubetemplatesynthesis[18]andthrough physical vapor deposition [19]. By heating WS 2 in oxygen, hollow fibres of crystalline W 18 O 49 arranged in a pine-tree-like structure were also reported [20]. In this Letter, we report the preparation of tungstenoxidenanowiresthroughthevapor–solid Chemical Physics Letters 372 (2003) 179–182 www.elsevier.com/locate/cplett * Corresponding author. Fax: +81-298-516280. E-mail address: Liu.zongwen@nims.go.jp (Z. Liu). 0009-2614/03/$ - see front matter Ó 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0009-2614(03)00397-X