1. Department of Chemistry; The Hong Kong University of Science and Technology; Clear Water Bay Kowloon Hong Kong
2. Nano Science and Technology Program; The Hong Kong University of Science and Technology; Clear Water Bay Kowloon Hong Kong
3. Institute of Polymer Optoelectronic Materials and Devices; State Key Laboratory of Luminescent Materials and Devices; South China University of Technology; Guangzhou 510640 P. R. China
4. Department of Physics; The Hong Kong University of Science and Technology; Clear Water Bay Kowloon Hong Kong