1. College of Physics and Energy
2. Shenzhen University
3. Shenzhen 518060
4. P. R. China
5. Department of Physics
6. The Hong Kong University of Science fand Technology
7. Kowloon
8. Hong Kong
9. HKUST Shenzhen Research Institute
10. Department of Materials Science and NanoEngineering
11. Department of Chemistry, and the Smalley Institute for Nanoscale Science and Technology
12. Rice University
13. Houston
14. USA