1. Department of Electrical and Computer Engineering, Rice University, MS 366, Houston, Texas 77005-1892, United States
2. Department of Chemistry, Rice University, MS 60, Houston, Texas 77005-1892, United States
3. Smalley-Curl Institute, Rice University, Houston, Texas 77005, United States
4. Department of Chemistry, KU Leuven, Celestijnenlaan 200G-F, B-3001 Heverlee, Belgium
5. Nano-Science Center/Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
6. Research Institute for Electronic Science, Hokkaido University, N20W10, Kita-Ward, Sapporo, 001-0020, Japan