1. Inorganic Chemistry Laboratory, Chemistry Department, National and Kapodistrian University of Athens, Panepistimiopolis, Zografou 157 71, Greece
2. NCSR “Demokritos”, Sol-Gel Laboratory, Institute of Nanoscience and Nanotechnology, 153 10 Aghia Paraskevi Attikis, Greece
3. Department of Materials Science & Engineering, University of Ioannina, 45110 Ioannina, Greece