1. CAS Key Laboratory of Standardization and Measurement for Nanotechnology CAS Key Laboratory of Biological Effects of Nanomaterials and Nanosafety 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
4. Translational Medicine Center Chinese Institute for Brain Research (CIBR) Beijing 102206 P. R. China