1. Jiangsu Collaborative Innovation Center of Biomedical Functional MaterialsSchool of Chemistry and Materials ScienceNanjing Normal University Nanjing 210023 P. R. China
2. College of Information Science and EngineeringShandong Agricultural University Tai'an 271000 China
3. Beijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of Sciences Beijing 100190 China
4. School of Physics and TechnologyNanjing Normal University Nanjing 210023 P. R. China