1. Department of Chemistry, University of California, Berkeley, California 94720, United States
2. Department of Physics, University of California, Berkeley, California 94720, United States
3. Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
4. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
5. Kavli Energy NanoScience Institute, Berkeley, California 94720, United States