1. Department of Biological, Chemical and Pharmaceutical Sciences and Technologies (STEBICEF)University of Palermo V.le delle Scienze pad. 17 - 90128 Palermo Italy
2. Istituto per lo Studio deiMateriali Nanostrutturati (ISMN) CNR Palermo Via Ugo La Malfa 153 - 90146 Palermo Italy
3. Department of Physics and ChemistryUniversity of Palermo V.le delle Scienze pad. 17 - 90128 Palermo Italy
4. Dip. di Sc. Chimiche, BiologicheFarmaceutiche ed AmbientaliUniversity of Messina,Viale Ferdinando Stagno d'Alcontres, 31 98166 Messina Italy