1. Center for Nanochemistry, Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, People's Republic of China
2. Beijing Graphene Institute, Beijing 100095, People's Republic of China
3. Department of Engineering, University of Cambridge, Cambridge CB3 0FA, United Kingdom
4. Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, People's Republic of China
5. Materials Science and Engineering, National University of Singapore, Singapore