1. School of Physics and Electronics, Hunan University, Changsha 410082, China
2. College of Materials Science and Engineering, Hunan University, Yuelu, Changsha, Hunan 410082, China
3. Hunan Province Key Laboratory for Advanced Carbon Materials and Applied Technology, Hunan University, Yuelu, Changsha, Hunan 410082, China
4. State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Changsha 410082, China