1. Beijing
Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials,
Key Laboratory of Cluster Science, Ministry of Education of China,
School of Chemistry, Beijing Institute of Technology, Beijing 100081, P. R. China
2. Center
of Advanced Science and Engineering for Carbon (Case4Carbon), Department
of Macromolecular Science and Engineering, Case School of Engineering, Case Western Reserve University, Cleveland, Ohio 44106, United States