1. State Key Laboratory of Rare Earth Resource Utilization, Changch un Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China
2. Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), College of Chemistry, Nankai University, Tianjin 300071, P. R. China
3. Kekulé Institute of Organic Chemistry and Biochemistry, Rheinische-Friedrich-Wilhelms-University of Bonn, Gerhard-Domagk-Str. 1, D-53121 Bonn, Germany
4. Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, Engesserstrasse 15, 76131 Karlsruhe, Germany
5. Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, Eggensteinn-Leopoldshafen, 76344 Karlsruhe, Germany
6. University of Science and Technology of China, Hefei 230026, P. R. China