1. CAS Key Laboratory of Nanosystem and Hierarchical Fabrication
2. CAS Center for Excellence in Nanoscience
3. National Center for Nanoscience and Technology
4. Beijing 100190
5. P. R. China
6. Shaanxi Key Laboratory for Advanced Energy Devices
7. School of Materials Science and Engineering
8. Shaanxi Normal University
9. Xi'an 710119