1. Department of Materials Science and Engineering City University of Hong Kong 83 Tat Chee Avenue Kowloon Hong Kong 999077 China
2. Department of Chemistry University of Puerto Rico Rio Piedras Campus San Juan PR 00931 USA
3. School of Materials Science and Engineering China University of Petroleum (East China) Qingdao 266580 China
4. Centre for Functional Photonics City University of Hong Kong Kowloon Hong Kong