1. Institute of Solid State Physics, NAWI Graz, Graz University of Technology, Graz 8010, Austria
2. Department of Physical Chemistry, Institute of Chemistry, NAWI Graz, University Graz, Graz 8010, Austria
3. Departments of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
4. Departments of Chemistry and Materials Science and NanoEngineering, and the Smalley-Curl Institute and NanoCarbon Center, Rice University, Houston, Texas 77005, United States