Flame-made Nb- and Cu-doped TiO2 sensors for CO and ethanol

Nb- and Cu-doped TiO2 nanoparticles were produced by flame spray pyrolysis (FSP) and tested for sensing of CO and ethanol at 400 degrees C in dry air. The as-prepared powders were characterized by transmission electron microscopy, X-ray diffraction, Raman spectroscopy and nitrogen adsorption. Niobium stabilized the anatase phase and retarded grain growth up to 600 degrees C. Copper promoted rutile formation and an anatase to rutile transformation was already observed just above 400 degrees C during post-synthesis calcination. This was accompanied by a segregation of large (>100 nm) CuO crystals which were initially small (<5 nm) asperities on the titania surface. Pure as well as doped TiO2 showed an n-type signal to CO and ethanol. Both dopants improved the sensitivity towards CO over that of pure TiO2- In contrast, for ethanol a high increase in sensitivity was observed. only for Nb/TiO2. (C) 2007 Elsevier B.V All rights reserved.