1. The Key Laboratory
of Rare Earth Functional Materials and Applications, Zhoukou Normal University, Zhoukou 466001, P. R. China
2. School of Mechanical & Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore
3. International Joint Research Laboratory for Biomedical Nanomaterials of Henan, Zhoukou 466001, P. R. China