1. Department of Materials Science and Engineering, City University of Hong Kong, Tat Chee Avenue 83, Kowloon, Hong Kong SAR 999077, P. R. China
2. School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, P. R. China
3. Advanced Membranes and Porous Materials (AMPM) Center, Physical Science and Engineering Division, King Ab-dullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
4. Department of Chemistry, City University of Hong Kong, Tat Chee Avenue 83, Kowloon, Hong Kong SAR 999077, P. R. China
5. Department of Chemistry and the N.1 Institute for Health, National University of Singapore, Singapore 117543, Singapore
6. Department of Chemistry & Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, Tat Chee Avenue 83, Kowloon, Hong Kong SAR 999077, P. R. China