1. Department
of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
2. Materials
and Surface Science Institute and Department of Physics and Energy, University of Limerick, Co. Limerick, Ireland
3. Solar Energy Research
Institute of Singapore (SERIS), 7 Engineering
Drive 1, National University of Singapore, Singapore 117574, Singapore
4. Centre
for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore