1. Key Laboratory for Biological Effects of Nanomaterials and Nanosafety (Chinese Academy of Sciences) Key Laboratory of Standardization and Measurement for Nanotechnology (Chinese Academy of Sciences) and CAS Center for Excellence in Nanoscience National Center for Nanoscience and Technology Beijing 100190 P. R. China
2. University of Chinese Academy of Sciences Beijing 100049 P. R. China
3. Department of Chemistry Tsinghua University Beijing 100084 P. R. China