1. Department of Chemical and Biomolecular Engineering, Department of Chemistry, Department of Materials Science and NanoEngineering, and The Smalley-Curl Institute, Rice University, Houston, Texas 77005, USA
2. Dipartimento di Ingegneria Industriale, Università di Roma “Tor Vergata,” 00133 Roma, Italy
3. Dipartimento di Fisica and Minas Lab, Università di Roma “Tor Vergata,” 00133 Roma, Italy