1. School of Science, Shandong Jiaotong University, 5001 Haitang Road, Jinan 250357, P. R. China
2. Key Laboratory of UV-Emitting Materials and Technology of Chinese Ministry of Education, Northeast Normal University, 5268, Renmin Street, Changchun 130024, P. R. China
3. Xinjiang Laboratory of Phase Transitions and Microstructures in Condensed Matters, College of Physical Science and Technology, Yili Normal University, Yining 835000, P. R. China