1. Department
of Chemistry, National University of Singapore, 3 Science Drive 3, Lower Kent Ridge
Road, Singapore 117543, Singapore
2. Singapore-Peking
University Research Centre for a Sustainable Low-Carbon Future, 1 CREATE Way, #15-01, CREATE Tower, Singapore 138602, Singapore
3. College
of Chemistry, Chemical Engineering and Materials Science, Collaborative
Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215123, P. R. China
4. Department
of Physics, National University of Singapore, 2 Science Drive 3, Lower Kent Ridge
Road, Singapore 117542, Singapore
5. BNLMS,
College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China
6. National University of Singapore (Suzhou) Research Institute, 377 Lin Quan Street, Suzhou Industrial Park, Jiang Su 215123, P. R. China