1. Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
2. Institut de Ciéncia de Materials de Barcelona (ICMAB-CSIC)/CIBER-BBN, Campus de la UAB, Bellaterra 08193, Spain
3. Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, Mons 7000, Belgium
4. Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603, Singapore
5. Centre for Advanced 2D Materials and Graphene Research Center, National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore