With the use of a modified plasma arc gas condensation technique and control of the processing parameters, namely, plasma current and chamber pressure, we synthesized tungsten oxide nanomaterials with aspect ratios ranging from 1.1 (for equiaxed particles with the length and width of 48 nm and 44 nm, respectively) to 12.7 (for rods with the length and width of 266 nm and 21 nm, respectively). The plasma current and chamber pressure, respectively, ranged from 70 to 90 A and from 200 to 600 Torr. We then characterized the tungsten oxide nanomaterials by means of X-ray diffraction, high-resolution transmission electron microscope, UV–visible spectroscope, and photoluminescence (PL) spectroscope. Experimental results show that equiaxed tungsten oxide nanoparticles were produced at a relatively low plasma current of 70 A, whereas nanorods were produced when plasma currents or chamber pressures were increased. All of the as-prepared tungsten oxide nanomaterials exhibited a WO2.8 phase. Compared to the nanoparticles, the nanorods exhibited unique properties, such as a redshift in the UV–visible spectrum, a blue emission in PL spectrum, and a good performance in field emission. With respect to the field emission, the turn-on voltage for WO2.8 nanorods was found to be as low as 1.7 V/μm.
This is a preview of subscription content, log in to check access.
This study was supported by the National Science Council of Taiwan under contract no. NSC94-2216-E-027-008 and NSC95-2216-E-027-009. The authors would like to thank Ms. Ying-Mei Chang and Ms. Liang-Chu Wang for their technical assistance on transmission electron microscope.
Chen CH, Wang SJ, Ko RM, Kuo YC, Uang KM, Chen TM, Liou BW, Tsai HY (2006) The influence of oxygen content in the sputtering gas on the self-synthesis of tungsten oxide nanowires on sputter-deposited tungsten films. Nanotechnology 17:217–223. doi:10.1088/0957-4484/17/1/036CrossRefADSGoogle Scholar
Cross WB, Parkin IP (2003) Aerosol assisted chemical vapour deposition of tungsten oxide films from polyoxotungstate precursors: active photocatalysts. Chem Commun 9:1696–1697. doi:10.1039/b303800aCrossRefGoogle Scholar
Feng M, Pan AL, Zhang HR, Li ZA, Liu F, Liu W, Shi DX, Zou BS, Gao HJ (2005) Strong photoluminescence of nanostructured crystalline tungsten oxide thin films. Appl Phys Lett 86:141901–141901-3. doi:10.1063/1.1898434Google Scholar
Kojima Y, Kasuya K, Ooi T, Nagato K, Takayama K, Nakao M (2007) Effects of oxidation during synthesis on structure and field-emission property of tungsten oxide nanowires. Jpn J Appl Phys 46:6250–6253. doi:10.1143/JJAP.46.6250CrossRefADSGoogle Scholar
Lu DY, Chen J, Zhou J, Deng SZ, Xu NS, Xu JB (2007) Raman spectroscopic study of oxidation and phase transition in W18O49 nanowires. J Raman Spectrosc 38:176–180. doi:10.1002/jrs.1620CrossRefADSGoogle Scholar
Nilasson GA, Granqvist CG (2007) Electrochromics for smart windows: thin films of tungsten oxide and nickel oxide, and devices based on these. J Mater Chem 17:127–156. doi:10.1039/b612174hCrossRefGoogle Scholar
Polleux J, Gurlo A, Barsan N, Weimar U, Antonietti M, Niederberger M (2005) Template-free synthesis and assembly of single-crystalline tungsten oxide nanowires and their gas-sensing properties. Angew Chem Int Ed Engl 45:261–265. doi:10.1002/anie.200502823CrossRefPubMedGoogle Scholar
Su CY, Lin CK, Yang TK, Lin HC, Pan CT (2008) Oxygen partial pressure effect on the preparation of nanocrystalline tungsten oxide powders by a plasma arc gas condensation technique. Int J Refract Met Hard Mater 26:423–428. doi:10.1016/j.ijrmhm.2007.09.006CrossRefGoogle Scholar
Thangala J, Vaddiraju S, Bogale R, Thurman R, Powers T, Deb B, Sunkara MK (2007) Large-scale, hot-filament-assisted synthesis of tungsten oxide and related transition metal oxide nanowires. Small 3:890–896. doi:10.1002/smll.200600689CrossRefPubMedGoogle Scholar
Zhang Y, Chen Y, Liu H, Zhou Y, Li R, Cai M, Sun X (2009) Three-dimensional hierarchical structure of single crystalline tungsten oxide nanowires: construction, phase transition, and voltammetric behavior. J Phys Chem C 113:1746–1750. doi:10.1021/jp808774mCrossRefGoogle Scholar
Zheng Y, Chen C, Zha Y, Lin X, Zheng Q, Wei K, Zhu J, Zhu Y (2007) Luminescence and photocatalytic activity of ZnO nanocrystals: correlation between structure and property. Inorg Chem 46:6675–6682. doi:10.1021/ic062394mCrossRefPubMedGoogle Scholar
Zhou J, Gong L, Deng SZ, Chen J, She JC, Xu NS, Yang R, Wang ZL (2005) Growth and field-emission property of tungsten oxide nanotip arrays. Appl Phys Lett 87:223108. doi:10.1063/1.2136006CrossRefADSGoogle Scholar