Hydrothermal preparation and optical properties of orientation-controlled WO3 nanorod arrays on ITO substrates

The orientation controlled synthesis of h-WO3 nanostructures on ITO substrates has been successfully realized in large scale via a simple hydrothermal method. The influences of pH value and growth time on the orientation and morphology of WO3 nanostructures were investigated by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The nanorod bundles parallel to ITO substrate and nanorod arrays vertical to ITO substrate can be selectively prepared by adjusting the final pH value just to 2.0 and 2.4, respectively. The morphology evolution and the growth mechanism of well aligned WO3 nanorod arrays were intensively studied. Moreover, the optical properties of the WO3 with different oriented alignment were also examined.