1. Department of Physics, Graduate Center, City University of New York, New York, New York 10016, USA
2. Photonics Initiative, Advanced Science Research Center, City University of New York, New York, New York 10031, USA
3. Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA
4. Department of Chemistry, Columbia University, New York, New York 10027, USA
5. Department of Physics, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
6. School of Chemistry, Chemical Engineering and Life Science; State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China