1. Department of Chemistry, University of California, Berkeley, California 94720, USA
2. Kavli Energy Nanoscience Institute at Berkeley, Berkeley, California 94720, USA
3. Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
4. Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
5. Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA