[1] Alexandru Ioan Cuza Univ, Dept Solid State & Theoret Phys, Iasi 700506, Romania
[2] Univ Genoa, Dept Chem & Proc Engn, I-16129 Genoa, Italy
[3] CNR, Inst Energet & Interphases, I-16149 Genoa, Italy
[4] Univ Genoa, Dept Phys, I-16146 Genoa, Italy
[5] Univ Genoa, INFM, I-16146 Genoa, Italy
[6] Univ Quebec, INRS EMT, Varennes, PQ J3X 1S2, Canada
[7] Univ Milan, Dept Mat Sci, I-20126 Milan, Italy
[8] CNR, Inst Macromol Mat, I-16149 Genoa, Italy