1. Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, Massachusetts 01609
2. Nuclear Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
3. State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China
4. State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, China