Growth of rutile TiO2 nanorods on anatase TiO2 thin films on Si-based substrates

Synthesis of titania (TiO2) nanorods on various substrates has recently attracted attention for energy and environmental applications. Herein, we report growth of nanostructured TiO2 on Si(111) and glass borosilicate substrates by a two-step method. A thin film of anatase TiO2 was first laid down by spin coating and annealing, followed by the growth of rutile TiO2 nanorods with a hydrothermal method. To understand the role of the polycrystalline anatase TiO2 seed layer, we selected a relatively high temperature for the hydrothermal reaction, e. g., 175 degrees C at which no rutile TiO2 nanorods could grow without the precoated anatase TiO2 layer. The morphology and microstructure of both the polycrystalline anatase and rutile nanorod layers were characterized by electron microscopy and x-ray powder diffraction. Such a two-step fabrication method makes it possible to grow TiO2 nanorods on almost any substrate.