1. Department of Chemistry and Center of Super-Diamond & Advanced Films (COSDAF), City University of Hong Kong, Kowloon, Hong Kong 999077, P. R. China
2. City University of Hong Kong Shenzhen Research Institute, Shenzhen 518057, P. R. China
3. Department of Applied Physics, The Hong Kong Polytechnic University, Kowloon, Hong Kong 999077, P. R. China
4. The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen 518057, P. R. China
5. Department of Chemistry and State Key Laboratory of Marine Pollution, City University of Hong Kong, Kowloon, Hong Kong 999077, P. R. China