1. Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, Hong Kong SAR 999077, P. R. China
2. Hebei Key Laboratory of Applied Chemistry, Yanshan University, Qinhuangdao, Hebei 066004, P. R. China
3. Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong SAR 518057, P. R. China
4. Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, Kowloon, Hong Kong SAR 518057, P. R. China