1. Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety; Institute of High Energy Physics and National Center for Nanosciences and Technology; Chinese Academy of Sciences; Beijing P.R. China
2. College of Chemistry; Sichuan University; Chengdu 610064 P. R. China
3. College of Materials Science and Opto-electronic Technology; University of Chinese Academy of Sciences; Beijing 100049 P. R. China