1. Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
2. Department of Chemistry, MOE Key Laboratory for Computational Physical Sciences, Fudan University, Shanghai 200433, People's Republic of China
3. College of Chemistry and Chemical Engineering, Fuzhou University, Fujian 350108, People's Republic of China
4. Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 3 Research Link, Singapore 117602