1. State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, P. R. China
2. Department of Chemistry, University of South Florida, Tampa, Florida 33620, United States
3. College of Chemistry, Zhengzhou University, Zhengzhou, Henan 450001, P. R. China
4. Advanced Materials Research Group, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, United Kingdom