1. Department
of Chemistry, National University of Singapore, Singapore 117543, Singapore
2. NUS
Graduate School for Integrative Sciences and Engineering, Centre for
Life Sciences, National University of Singapore, #05-01, 28 Medical Drive, Singapore 117456, Singapore
3. SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China
4. Department
of Physics, National University of Singapore, Singapore 117551, Singapore
5. Centre
for Micro-Photonics, Faculty of Science Engineering and Technology, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia
6. Centre
for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546, Singapore
7. Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States