1. Beijing Graphene Institute Beijing 100095 P. R. China
2. Center for Nanochemistry Beijing Science and Engineering Center for Nanocarbons Beijing National Laboratory for Molecular Science College of Chemistry and Molecular Engineering Peking University Beijing 100871 P. R. China
3. College of Science University of Petroleum Beijing 102249 P. R. China
4. Academy for Advanced Interdisciplinary Studies Peking University Beijing 100871 China
5. CAS Key Laboratory of Standardization and Measurement for Nanotechnology CAS Center for Excellence in Nanoscience National Center for Nanoscience and Technology Beijing 100190 China
6. University of Chinese Academy of Sciences Beijing 100049 China
7. School of Materials Science and Engineering Peking University Beijing 100871 P. R. China