[1] IIT, Nano Carbon Mat, Via Livorno 60, I-10144 Turin, Italy
[2] IIT, Nanoscopy, Via Morego 30, I-16163 Genoa, Italy
[3] Univ Genoa, Dept Chem, Via Dodecaneso 31, I-16145 Genoa, Italy
[4] IIT, NIC IIT, Via Morego 30, I-16163 Genoa, Italy
[5] Univ Genoa, Dept Phys, Via Dodecaneso 33, I-16145 Genoa, Italy
[6] Univ Turin, Dept Chem, Via Giuria 7, I-10125 Turin, Italy