1. College of Chemistry Sichuan University Key Laboratory of Radiation Physics & Technology Ministry of Education No. 29 Wangjiang Road Chengdu 610064 P. R. China
2. Hefei National Laboratory for Physical Sciences at the Microscale University of Science and Technology of China Hefei Anhui 230026 P. R. China
3. Electron Microscopy of Materials Science, Central Facility for Electron Microscopy Ulm University Albert-Einstein-Allee 11 89081 Ulm Germany
4. School of Pharmacy Chengdu University of Traditional Chinese Medicine Chengdu 611137 P. R. China