1. School of Chemistry and Chemical Engineering; Chongqing University; Chongqing 401331 P. R. China
2. 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
3. Academy for Advanced Interdisciplinary Studies; Peking University; Beijing 100871 P. R. China
4. The National Center for Nanoscience and Technology; Beijing 100190 P. R. China