1. Key
Laboratory of Luminescence and Optical Information, Ministry of Education,
Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044, P. R. China
2. School
of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, United Kingdom
3. College
of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China