1. Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542
2. NanoCore, National University of Singapore, 4 Engineering Drive 3, Singapore 117576
3. Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546
4. SKKU Advanced Institute of Nanotechnology (SAINT) and Center for Human Interface Nano Technology (HINT), Sungkyunkwan University, Suwon 440-746, Korea
5. Department of Chemistry, Seoul National University, Seoul, 151-747, Korea
6. Institute of Material Research and Engineering (IMRE), A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602
7. NUS Graduate School for Integrative Sciences and Engineering (NGS), National University of Singapore, Singapore 117456