1. Institute for the Study of the Nanostructured Materials; National Research Council (CNR-ISMN); Via Gobetti 101 40129 Bologna Italy
2. Center for Nano Science and Technology; Italian Institute of Technology; Via Pascoli 70/3 (IIT-CNST) 20133 Milano Italy
3. Dipartimento di Fisica; Politecnico di Milano; Piazza Leonardo da Vinci 32 20133 Milano Italy
4. Institute for Microelectronics and Microsystems; National Research Council (CNR-IMM); Via Gobetti 101 40129 Bologna Italy
5. Institute of Organic Synthesis and Photoreactivity; National Research Council (CNR-ISOF); Via Gobetti 101 40129 Bologna Italy