1. Department
of Chemistry and Graphene Research Centre, National University of Singapore, 3 Science Drive 3, Singapore 117543
2. Graduate
School for Integrative Sciences and Engineering, National University of Singapore, 28 Medical Drive #05-01, Singapore 117456
3. Pacific Northwest National Laboratory, Richland, Washington 99354, United States
4. Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 3 Research Link, S117602, Singapore