Photocatalytic, spectroscopic and transport properties of lanthanide-dopedTiO2 nanocrystals

Abstract

The photocatalytic properties of the anatase form of nanocrystallineTiO2 doped withlanthanide ions (Eu3+,Sm3+ and Er3+), obtained by a sol–gel preparation method, are studied by means ofthe degradation of methylene blue. It is observed that the presence ofSm3+ ion as a dopant significantly improves the photocatalytic activity of anataseTiO2 with respectto the Eu3+ or Er3+ ions.For the understanding of such a catalytic process the charge transport in these systems isstudied by an appropriate Monte Carlo simulation which includes phonons, chargedimpurities and traps. The obtained results evidence the important role of the traps for thetransit of the electrons in the systems investigated here. They decrease the diffusioncoefficient by about three orders of magnitude with respect to the bulk, from which it ispossible to obtain a simple estimate of the reaction rate in agreement with experimentalresults. All the lanthanide-doped samples show a strong luminescence in the visible region.The emission bands are affected by a notable inhomogeneous broadening, indicating a highdisorder of the crystalline environment of the lanthanide ions in the titania host.