1. Department
of Chemistry, University of Massachusetts—Amherst, 710 North Pleasant Street, Amherst, Massachusetts 01003, United States
2. Laboratory
of Controllable Nanopharmaceuticals, Chinese Academy of Sciences (CAS)
Center for Excellence in Nanoscience; and CAS Key Laboratory for Biomedical
Effects of Nanomaterials and Nanosafety, National Center for Nanoscience and Technology, First North Road, Zhongguancun, Beijing 100190, P. R. China
3. University of Chinese Academy of Sciences, Beijing 100049, P. R. China