TAILORING THE STRUCTURE AND MORPHOLOGY OF WO3 NANOSTRUCTURES BY HYDROTHERMAL METHOD

Tungsten oxide nanostructures were synthesized by hydrothermal and acid precipitation (hydrothermal at room temperature) methods without using any supporting agent or structure-directing reactant. The morphology and crystalline structure of nanostructures strongly depended on pH of the precursor solution and synthesis method. With pH = -1.0, using acid precipitation method, orthorhombic nanoplate was observed. Using hydrothermal method, with the pH = - 1.0, we obtained directly stable monoclinic nanoparticle WO3. With pH = 1.1, the mixing of nanoparticle and nanorod with the hexagonal frame was acquired. When pH reaches to 1.7, only bundle of hexagonal nanorods was observed. To characterize the morphology and structure of tungsten nanostructures, we used Field Emission Scanning Electron Microscopy, X-ray diffraction, and micro Raman spectroscopy. The micro Raman spectroscopy was used to support the X-ray diffraction analysis. These results imply that adjusting pH is an efficient and promising method to manipulate both morphology and crystal structure of WO3 nanostructure for selective applications.