1. Department of Materials Science and Engineering
2. University of Science and Technology Beijing
3. Beijing 100083
4. P. R. China
5. Wuhan National Laboratory for Optoelectronics
6. Huazhong University of Science and Technology
7. Wuhan 430074
8. Department of Biomedical Engineering
9. Emory University
10. Atlanta 30322
11. USA
12. Institute for Advanced Materials and Technology