1. Center for Nanochemistry; Beijing Science and Engineering Center for Nanocarbons; Beijing National Laboratory for Molecular Sciences (BNLMS); College of Chemistry and Molecular Engineering; Peking University; Beijing 100871 P. R. China
2. Academy for Advanced Interdisciplinary Studies; Peking University; Beijing 100871 P. R. China
3. Key Laboratory of Opto-Electronics Technology; Ministry of Education; College of Electronic Science and Technology; Faculty of Information Technology; Beijing University of Technology; Beijing 100022 P. R. China
4. Beijing Graphene Institute; Beijing 100094 P. R. China