1. Center for NanochemistryBeijing Science and Engineering Center for NanocarbonsBeijing National Laboratory for Molecular SciencesCollege of Chemistry and Molecular EngineeringPeking University Beijing 100871 P. R. China
2. Academy for Advanced Interdisciplinary StudiesPeking University Beijing 100871 P. R. China
3. Beijing Graphene Institute Beijing 100095 P. R. China