1. Department of Physics, University of Ioannina, P.O. Box 1186, 451 10 Ioannina, Greece
2. Department of Chemistry, Johannes Gutenberg—University of Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
3. University Research Center of Ioannina (URCI), Institute of Materials Science and Computing, 451 10 Ioannina, Greece
4. Max Planck Institute for Polymer Research, 55128 Mainz, Germany