Wei Shen1, Ke Li1, Yangyang Lv1, Tao Xu1, Di Wei1,* and Zhongfan Liu1,2,*
1 Beijing Graphene Institute, Beijing, 100094 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