* Corresponding authors

^a Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore 117576
E-mail: cheliub@nus.edu.sg

^b Department of Pharmaceutical Analysis, China Pharmaceutical University, Nanjing 210009, China

^c Department of Chemistry, Division of Biomedical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China

^d Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore

^e National Laboratory of Solid-State Microstructure, Department of Material Science and Engineering, Nanjing University, Nanjing 210093, China

^f SCUT-HKUST Joint Research Laboratory, Guangdong Innovative Research Team, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China

^g Institute of Materials Research Engineering, 3 Research Link, Singapore