| Metal-doped titanium dioxide nanoparticles can be employed in various applications, including dye-sensitized solar cells and gas sensors. Metal-doping is able to enhance the performance of titanium dioxide as photocatalysts by the dispersion of metal ions into the TiO2 matrix. In this work, tungsten-doped titanium dioxide nanoparticles are synthesized by a multiple diffusion flames burner using TTIP as the precursor (for titania) and tungsten mesh as the metal source (for doping). This novel method of using a metal mesh as precursor for doping is especially advantageous for low-vapor-pressure precursors and the entire nanoparticle synthesis process to be gas-phase based. The effect of varying the tungsten loading rate is studied for synthesizing doped titanium dioxide with different tungsten amount. The results show that high loading rate of tungsten can trigger homogenous nucleation of WO3 prior to reaching the TTIP precursor loaded region, thereby leaving less tungsten ions to be doped into TiO2, when compared to the relatively lower tungsten loading rate configuration. Heat treatment at 973 K in an Ar atmosphere moves some of the tungsten out of the TiO 2 structure, thus making a new WOx-TiO2 solid solution, while tungsten ions are reduced to lower oxidation states. Moreover the annealing process also increases the unit cell volume of W-doped TiO 2, making the value closer to that of the un-doped TiO2. XRD, SEM, TEM, and XPS results are to prove the theory presented. UV Vis results show tungsten doping and heat treatment improve the absorbing ability of titanium dioxide in the visible light wavelength range significantly. |
