1. Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, P. R. China
2. College of Chemistry and Molecular Engineering, Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences, Peking University, Beijing 100871, P. R. China
3. Institute of Information Photonics Technology, Faculty of Science, Beijing University of Technology, Beijing 100124, P. R. China