1. Chongqing Key Laboratory for Advanced Materials and Technologies of Clean Energy
2. Faculty of Materials & Energy
3. Southwest University
4. Chongqing 400715
5. P. R. China
6. Department of Materials Science and Engineering
7. University of Science and Technology of China
8. Hefei
9. China
10. Department of Physics
11. The Chinese University of Hong Kong
12. N.T.