The sonochemical preparation of tungsten oxide nanoparticles

Amorphous tungsten oxide has been prepared by ultrasound irradiation of a solution of tungsten hexacarbonyl W(CO)(6) in diphenylmethane (DPhM) in the presence of an Ar (80%)-O-2 (20%) gaseous mixture at 90 degreesC. Heating this amorphous powder at 550 degreesC under Ar yields snowflake-like dendritic particles consisting of a mixture of monoclinic and orthorhombic WO2 crystals. Annealing of the as-prepared product in Ar at 1000 degreesC causes the formation of a WO2-WO3 mixture containing nanorods (around 50 nm in diameter) and packs of these nanorods. Heating the product in air for 3 hours leads to triclinic WO3 crystal formation, with a basic size of 50-70 nm. The prepared oxides have been characterized by elemental analysis, X-ray powder diffraction measurements, FTIR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX).