1. College of Chemistry and Environmental ScienceHebei University Baoding 071002 Hebei China
2. Department of Materials Science and Engineering & Centre for Functional Photonics (CFP)City University of Hong Kong 83 Tat Chee Avenue Kowloon Hong Kong S.A.R. China
3. Shenzhen Research InstituteCity University of Hong Kong Shenzhen 518057 China