1. Institute of Nanoscience and Nanotechnology (INN), National Center for Scientific Research Demokritos, Agia Paraskevi, 15341 Athens, Greece
2. Department of Physics, University of Patras, 26504 Rio Patra, Greece
3. Solid State Physics Section, Physics Department, National and Kapodistrian University of Athens, Panepistimioupolis, 15784 Athens, Greece
4. Department of Electrical and Computer Engineering, University of Thessaly, 38221 Volos, Greece
5. Department of Materials, Imperial College, London SW7 2AZ, UK
6. Laboratory of Bioinorganic Chemistry, Department of Chemistry, University of Crete, Voutes Campus, P.O. Box 2208, 71003 Heraklion, Greece