1. Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province; State Key Laboratory of Applied Organic Chemistry and The Research Center of Biomedical Nanotechnology; Lanzhou University; Lanzhou 730000 P. R. China
2. Wuhan National Laboratory for Optoelectronics; School of Optical and Electronic Information; Huazhong University of Science and Technology; Wuhan 430074 P. R. China