1. Department of Physics and Astronomy, University of California, Irvine, CA 92697, USA
2. Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland, USA
3. Institute for Physical Science and Technology, University of Maryland, College Park, Maryland, USA
4. Department of Chemistry, University of California, Irvine, CA 92697, USA
5. Department of Biomedical Engineering, University of California, Irvine, CA 92697, USA