1. School of Materials Science and EngineeringXiangtan University Xiangtan 411105 China
2. Shenzhen Key Laboratory of NanobiomechanicsShenzhen Institutes of Advanced TechnologyChinese Academy of Sciences Shenzhen 518055 China
3. Department of Physics and Electronic ScienceHunan University of Science and Technology Xiangtan 411105 China
4. Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of EducationJilin Normal University Changchun 130103 China