We are grateful to the National Natural Science Foundation of China (Grant Nos. 21602070, 21472056) and the Fundamental Research Funds for the Central Universities (CCNU15ZX002 and CCNU16 A05002) for financial support. We acknowledge the graduate student educational innovation grant from Central China Normal University (2016CXZZ66). We also thank Dr. Chuanqi Zhou, Hebei University, for analytical support.