1. Department
of Physics, National University of Singapore, 2 Science Drive 3, 117542, Singapore
2. State
Key Laboratory of Luminescence and Applications, Changchun Institute
of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, No. 3888 Dongnanhu Road, Changchun, 130033, People’s Republic of China
3. Department
of Chemistry, National University of Singapore, 3 Science Drive 3, 117543, Singapore