1. Department of Physics, University of Ioannina, Ioannina 45110, Greece
2. Department of Chemistry, University of Massachusetts Lowell, Cambridge, Massachusetts, Lowell Massachusetts 01854, United States
3. CNR-IPCF, Università di Pisa, Largo Bruno Pontecorvo 3, Pisa I-56127, Italy
4. Institute of Materials Science and Computing, University Research Center of Ioannina (URCI), Ioannina 45110, Greece