1. Department of Chemistry and Biochemistry, University of California, Los Angeles (UCLA), Los Angeles, California 90095, USA
2. Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, Virginia 23284, USA
3. Department of Materials Science and Engineering, University of California, Los Angeles (UCLA), Los Angeles, California 90095, USA
4. California NanoSystems Institute (CNSI), University of California, Los Angeles (UCLA), Los Angeles, California 90095, USA