1. Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA.
2. Electrical and Computer Engineering and Materials Science and Mechanics, Michigan State University, East Lansing, MI 48824, USA.
3. Department of Physics, University of Michigan, Ann Arbor, MI 48109, USA.
4. Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.