1. Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
2. Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
3. Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
4. Department of Chemistry, Boston University, Boston, Massachusetts 02215, USA
5. Integrated Sciences Cleanroom Facility, Boston College, Chestnut Hill, Massachusetts 02467, USA
6. Division of Materials Science and Engineering, Boston University, Boston, Massachusetts 02215, USA
7. The Photonics Center, Boston University, Boston, Massachusetts 02215, USA