Chemical and structural analysis of solvothermal synthesized tungsten oxide nanotube without template and its hydrogen sensitive property

Tungsten oxide nanotubes were synthesized by solvothermal process without template. The steric effect and the concentration of WCl6 are the dominant factors for the formation mechanism of the nanotube. The steric effect was experimentally and systematically studied with solvents including ethanol, isopropanol, n-propanol and butylalcohol, which have different molecular configuration and length, while the effect of concentration was investigated by characterizing the nanostructured productions. The samples have been investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The surface chemistry of the nanotube is characterized by X-ray photoelectron spectroscopy (XPS). The results indicated that the solvents species and WCl6 concentration obviously diversified the morphologies of the products; the nanotubes synthesized with isopropanol composed of W18O49 phase; the crystal defects (O atom vacancy) formed during rapid crystallization could be modified by heat treatment. The DC electrical response of the nanotube thin film to hydrogen was measured the temperature range from 200 degrees C to 300 degrees C, which indicated a decline in electrical resistance with good sensitivity, and showed the mechanism that the reaction limited process works at low temperature, whereas the diffusion limited process works at higher temperature. (C) 2013 Elsevier B.V. All rights reserved.