The photocatalytic properties of the anatase form of nanocrystalline TiO 2 doped with lanthanide ions (Eu 3+ , Sm 3+ and Er 3+ ), obtained by a sol-gel preparation method, are studied by means of the degradation of methylene blue. It is observed that the presence of Sm 3+ ion as a dopant significantly improves the photocatalytic activity of anatase TiO 2 with respect to the Eu 3+ or Er 3+ ions.For the understanding of such a catalytic process the charge transport in these systems is studied by an appropriate Monte Carlo simulation which includes phonons, charged impurities and traps. The obtained results evidence the important role of the traps for the transit of the electrons in the systems investigated here. They decrease the diffusion coefficient by about three orders of magnitude with respect to the bulk, from which it is possible to obtain a simple estimate of the reaction rate in agreement with experimental results. 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 high disorder of the crystalline environment of the lanthanide ions in the titania host.

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The superconducting properties of the SmBa2Cu3O 6+δ superconductor change dramatically upon oxidation. The driving force for these changes is still under debate because many concomitant structural changes occur. In order to highlight the specific role of Cu-O chain ordering on the rise of superconductivity in this system, Al-doped SmBa2Cu3O 6+δ samples have been examined, having equal aluminium and oxygen concentration and nearly the same structure but different mean length of Cu-O chain fragments. For the first time, it is clearly shown that, keeping all the other structural properties unchanged, the local increase of the chain length determines a significant enhancement of the superconducting properties, i.e. TC and Meissner fraction.