TiO 2 thin films were grown by pulsed laser deposition on a wide variety of oxide single-crystal substrates and characterized in detail by four-circle X-ray diffraction. Films grown at 873 K on (100)-oriented SrTiO 3 and LaAlO 3 were (001)-oriented anatase, while on (100) MgO they were (100)-oriented. On (110) SrTiO 3 and MgO, (102) anatase was observed. On M-plane and R-plane sapphire, (001)-and (101)-oriented rutile films were obtained, respectively. On C-plane sapphire, the coexistence of (001) anatase, (112) anatase and (100) rutile was found; increasing the deposition temperature tended to increase the rutile proportion. Similarly, films grown at 973 K on (100) and (110) MgO showed the emergence, besides anatase, of (110) rutile. All these films were epitaxically grown, as shown by ' scans and/or pole figures, and the various observed orientations were explained on the basis of misfit considerations and interface arrangement.

Zn x Ti y O z layers were prepared by sol–gel method and nitridated yielding photoactivity in the visible wavelength region. The condensation process of these nanostructures and their subsequent sintering was followed by using XRD-, UV/Vis-, micro-Raman-, FTIR- and thermal analysis measurements. The oxynitride formation during the nitridation process was confirmed by XPS and UV-Vis spectroscopy. The photocatalytical studies of methylene blue (MB) degradation revealed the activity of coloured oxynitride layers under the visible light irradiation. Furthermore, a metachromasy of MB infiltrated within the nanostructured films was observed for the first time. This blue shift in the optical absorption spectrum of MB became even more pronounced during the photodegradation process of this dye.

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