1. Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095, United States
2. California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California 90095, United States
3. Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98185, United States
4. Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, California 90095, United States