Growth and characterisation of ceria thin films and Ce-doped y-Al2O3 nanowires using sol-gel techniques

¿-Al2O3 is a well known catalyst support. The addition of Ce to ¿-Al2O3 is known to beneficially retard the phase transformation of ¿-Al2O3 to a-Al2O3 and stabilise the ¿-pore structure. In this work, Ce-doped ¿-Al2O3 nanowires and CeO2 thin films have been prepared by a sol-gel hydrothermal ¿pore-sealing¿ of an anodic aluminium oxide (AAO) template in a 0.01M cerium nitrate solution assisted by urea hydrolysis. Calcination at 500 °C for 6 hours resulted in the crystallisation of the Ce-doped AlOOH gel to form Ce-doped ¿-Al2O3 nanowires and also a CeO2 thin film on top of the alumina template. The formation of Ce-doped ¿-Al2O3 was confirmed by transmission electron microscopy (TEM) and Electron Energy Loss Spectroscopy (EELS) showed the presence of Ce3+ ions within the nanowires at a concentration of < 1 at. %. On the template surface, XRD and XPS analysis confirmed the formation of a nanocrystalline CeO2 thin film, with a cubic fluorite structure and a crystallite size of 6-7 nm. The formation mechanism and urea hydrolysis kinetics are discussed in terms of the pH evolution during the reaction. The Ce-doped ¿-Al2O3 nanowires are likely to find useful applications in catalysis and the method can be exploited further for the deposition of nanocrystalline CeO2 films but more importantly, for doping alumina nanowires with other rare earth elements.JRC.I.4-Nanobioscience