1. School of Physics and Optoelectronic Engineering
2. Nanjing University of Information Science & Technology
3. Nanjing 210044, China
4. Department of Chemistry
5. National University of Singapore
6. Department of Physics
7. , Singapore
8. Institute of Materials Research and Engineering (IMRE)
9. Agency of Science
10. Technology
11. and Research (A*STAR)
12. Singapore 117602, Singapore