1. Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States
2. Department of Physics and Astronomy, Purdue University, 525 Northwestern Avenue, West Lafayette, Indiana 47907, United States
3. Nanoscience Center and Department of Chemistry, University of Jyväskylä, P.O. Box 35, 40014 Jyväskylä, Finland