1. Institute of Nanoscience and Nanotechnology; School of Physical Science and Technology; Lanzhou University; Lanzhou 730000 China
2. Institute of Pathogenic Biology; School of Basic Medical Sciences; Lanzhou University; 730000 China
3. The Research Institute of Biomedical Nanotechnology; School of Basic Medical Sciences; Lanzhou University; Lanzhou 730000 China
4. Beijing Institute of Nanoenergy and Nanosystems; Chinese Academy of Sciences; Beijing 100085 China
5. School of Materials Science and Engineering; Georgia Institute of Technology; Atlanta Georgia 30332-0245 USA