1. Department of Physics, University of Ioannina, Ioannina 45110, Greece
2. Department of Chemistry, Johannes Gutenberg Universität Mainz, Mainz 55099, Germany
3. Max Planck Graduate Center Mainz, Mainz 55128, Germany
4. University Research Center of Ioannina (URCI) - Institute of Materials Science and Computing, Ioannina 45110, Greece