1. Department of Physics, University of Ioannina, Ioannina 45110, Greece
2. Department of Chemistry, National and Kapodistrian University of Athens, Athens 15771, Greece
3. Institut für Chemie neuer Materialien, Universität Osnabrück, Osnabrück D-49069, Germany
4. Institute of Materials Science and Computing, University Research Center of Ioannina (URCI), Ioannina 45110, Greece