1. State Key Laboratory of Applied Organic Chemistry Key Laboratory of Special Function Materials and Structure Design College of Chemistry and Chemical Engineering Lanzhou University Lanzhou 730000 P. R. China
2. Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education School of Physical Science and Technology Lanzhou University Lanzhou 730000 P. R. China
3. National Laboratory of Solid State Microstructures & Collaborative Innovation Center of Advanced Microstructures School of Physics Nanjing University Nanjing 210093 P. R. China
4. Tianjin Key Laboratory of Molecular Optoelectronic Sciences Collaborative Innovation Center of Chemical Science and Engineering Tianjin 300072 P. R. China