1 Center for Excellence in Nanoscience (CAS), Key Laboratory of Nanosystem and Hierarchical Fabrication (CAS), National Center for Nanoscience and Technology, Beijing, 100190, People's Republic of China.
2 University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China.
3 Center for Excellence in Nanoscience (CAS), Key Laboratory of Nanosystem and Hierarchical Fabrication (CAS), National Center for Nanoscience and Technology, Beijing, 100190, People's Republic of China. ding@nanoctr.cn.