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 P. R. China
2. Academy for Advanced Interdisciplinary Studies; Peking University; Beijing 100871 P. R. China
3. School of Materials Science and Engineering; Shaanxi Normal University; Xi'an 710119 P. R. China