1. School of Physics and Electronics, State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Changsha 410082, P. R. China
2. Physics and Electronic Engineering Department, Xinxiang University, Xinxiang 453003, China
3. School of Materials Science and Engineering, Central South University, Changsha 410083, PR China
4. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083, PR China
5. College of Science, Clemson Nanomaterials Institute, Clemson University, Clemson, South Carolina 29634, United States
6. Fujian Strait Research Institute of Industrial Graphene Technologies, Quanzhou 362000, P. R. China