1. School of Materials Science and Engineering
2. Zhengzhou University
3. Zhengzhou 450001
4. P. R. China
5. Division of Nanophotonics
6. CAS Key Laboratory of Standardization and Measurement for Nanotechnology
7. CAS Center for Excellence in Nanoscience
8. National Center for Nanoscience and Technology
9. Beijing 100190
10. Technical Institute of Physics and Chemistry
11. University of Chinese Academy of Sciences