1. Center for Nanochemistry (CNC); College of Chemistry and Molecular Engineering; Peking University; Beijing 100871 P. R. China
2. State Key Laboratory of Rare Earth Materials Chemistry and Applications; College of Chemistry and Molecular Engineering; Peking University; Beijing 100871 P. R. China
3. School of Physics; Peking University; Beijing 100871 P. R. China
4. Institute of Advanced Materials; Graduate School at Shenzhen; Tsinghua University; Shenzhen 518055 P. R. China
5. Tsinghua-Berkeley Shenzhen Institute (TBSI); Tsinghua University; Shenzhen 518055 P. R. China
6. Department of Materials Science and Engineering; College of Engineering; Peking University; Beijing 100871 P. R. China