Comparison of doping limits among sonochemically prepared metal-doped TiO2 nanopowders in view of physicochemical properties

Abstract

According to binding energy calculations in a unit cell model of anatase TiO2, the doping limits for Cr, V, W, Mo, Zr, and Nb are predicted to increase in this order. In our experimental test of doping limits, Cr and W are considered in this series of transition metals, since their low doping limits suggest greater difficulty of doping into anatase structure than the others, thereby providing a challenging test for the prediction. Besides, noble metals such as Ag and Pt are selected for doping into TiO2 for comparison. Thus, our investigation includes twofold research activities. One is to prepare metal-doped TiO2 nanopowders of four different kinds, and the other is to determine the doping limit of each resulting powder. For the former, a sonochemical process has been used to produce metal-doped TiO2 nanoparticles. For the latter, we resorted to electron probe microanalysis. In addition, we performed analysis by X-ray diffraction, transmission electron microscopy, and diffuse reflectance spectroscopy, as well as photocatalytic reaction with methylene blue. Thus, the resulting physicochemical properties of our metal-doped nanoparticles are expected to provide a basis for comparison of doping limits among them.