1. Key Laboratory of Materials Physics
2. Anhui Key Laboratory of Nanomaterials and Nanostructures
3. Institute of Solid State Physics
4. Chinese Academy of Sciences
5. Hefei 230031
6. Department of Pharmacy
7. Anhui Medical College
8. Hefei 230601
9. P. R. China
10. Department of Physics
11. The Chinese University of Hong Kong
12. Hong Kong