1. Contribution from the Departments of Materials Science and Engineering and Physics, University of Ioannina, 45110 Ioannina, Greece, Institute of Materials Science, NCSR “DEMOKRITOS”, Ag. Paraskevi-Attikis, 15310 Athens, Greece, Dipartimento di Scienze Farmaceutiche, Università di Trieste, Piazzale Europa 1, 34127, Trieste, Italy, and Dipartimento di Chimica “G. Ciamician”, Università di Bologna, V. F. Selmi 2, 40126 Bologna, Italy