Synthesis of tungsten oxide (W18O49) nanosheets utilizing EDTA salt by microwave irradiation method

We report the synthesis of crystalline W18O49 with nanosheet like morphology by low cost microwave irradiation method without employing hydrothermal process for the first time. Initially, WO3 center dot H2O was synthesized using ethylenediaminetetraacetic acid (EDTA) as surface modulator. The product was annealed at 600 degrees C for 6 h in ambient atmosphere in order to obtain anhydrous tungsten oxide W18O49. Powder X-ray diffraction results confirmed the as prepared WO3 center dot H2O to be orthorhombic and W18O49 to be monoclinic phase, respectively. Transmission electron micrographs (TEM) revealed that the W18O49 nanosheets have the average dimensions of the order of 250nm in length and around 150nm in width. UV-visible diffusion reflectance spectroscopic (DRS) studies revealed the band gap energies to be 3.28 and 3.47 eV for WO3 center dot H2O and W18O49 samples, respectively. The growth mechanism of two dimensional W18O49 nanosheets is discussed. (C) 2011 Published by Elsevier B.V.