[1] CNR, Ist Studio Mat Nanostrutturati, I-90146 Palermo, Italy
[2] Univ Palermo, Dipartimento Ingn Chim Proc & Mat, I-90128 Palermo, Italy
[3] Univ Poitiers, CNRS UMR 6630, Met Phys Lab, F-86962 Futuroscope, France
[4] Inst Super Tecn, Ctr Quim Fis Mol, P-1049001 Lisbon, Portugal