1. Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Binhai New City, Fuzhou350207, P. R. China
2. Department of Chemistry, National University of Singapore, 117543, Singapore
3. Beihang Hangzhou Innovation Institute Yuhang, Hangzhou310023, P. R. China
4. School of Physics, Beihang University, Beijing100191, P. R. China
5. Department of Physics, National University of Singapore, 117542, Singapore
6. National University of Singapore (Suzhou) Research Institute, 377 Lin Quan Street, Suzhou Industrial Park, Suzhou215123, P. R. China