Molten-salt synthesis of tungsten oxide nanotubes: Morphological and gas sensitivity

Abstract

A very simple molten-salt method was used to synthesize WO 3 nanotubes at moderate temperature (600 ).℃ The outer and inner diameters of the WO 3 nanotubes were about 100 nm and 30 nm,with a length of dozens of micrometers. TEM and XRD analyses showed that the WO 3 nanotubes were single crystal, and had monoclinic structure with the axes preferentially aligned along the [011] direction. The photoluminescence and the gas sensitivity of the nanotubes had been tested, showing that the products very well responded to acetone at 340 . ℃ tungsten oxide, nanotubes, photoluminescence property, gas sensitivity Nanostructured materials are expected to play a crucial role in the future technological advance in electronics, optoelectronics, and memory devices. One-dimensional nanostructures in particular offer fundamental opportunities for investigating the effect of size and dimensionality on their collective optical, magnetic, and electronic properties. Various 1-D nanostructured metal oxides have been obtained via several different synthetic approaches, including solvothermal methods, template-directed syntheses, sonochemistry, thermal evaporation, and gas-phase catalytic growth. Transition metal oxides are a large family of materials that show many interesting properties such as superconductivity, colossal magnetoresistance, and piezoelectricity. Nanosized transition metal oxides, because of their huge surface areas, are promising candidates for a vast range of applications including lithium-ion batteries, catalysts, electrochromic materials, and sensors [1] .Tungsten oxide is one kind of transition metal oxide, and nanostructured tungsten oxide can be prepared using some different approaches. Park et al. [2] synthesized WO 3 nanotubes at 270℃ by the method of thermal solvent; Hua et al. [3] synthesized WO 3 nanorods and nanowires at approximate temperature. by one of thermal solvent methods with inorganic water solution as the media; Qi et al. [4] produced WO 3 nano linearly array doped with potassium by heating tungsten plate covered by potassium halide; Rout et al. [5] produced WO 3 1D nanostructure by the method of thermal solvent, and tested the gas sensing response of the product to nitride oxide; Ponzoni et al. [6] produced the WO 3 web structure by the method of thermal evaporation, and tested response of products to the gases of H 2 S，NH 3 ; Wu et al. [7] produced the WO 3 tube structure by the method of electrochemistry deposition.In this letter, we describe a very simple method to prepare tungsten oxide nanotubes directly growing on tungsten foils in air, which has not been reported so far. photoluminescence and the gas sensitivity of the nanotubes have been tested.

Photocatalytic O2 production using WO3 nanoparticles prepared by annealing ethylenediamine tungstate/CxNy gel

“…Furthermore, as compared with photocatalytic H 2 production from water, photocatalytic water oxidation to produce O 2 is much more important and challenging because the formation of one molecular O 2 from H 2 O requires four electrons or holes while producing one molecular H 2 only requires two electrons. 9,10 In the past few decades, several photocatalysts, such as WO 3 , [11][12][13][14][15][16][17][18] d-MnO 2 , 19 calcium manganese oxides, 20 metallic complex (such as iridium complex, 10 ruthenium complexes 21 ), metal-ion substitution (such as BiCu 2 PO 6 (ref. 22) and In 1Àx Ni x -TaO 4 (ref.…”