1. School of Materials Science and Engineering, Shanghai University, Shanghai 200444, P. R. China
2. School of Environmental Chemistry, Shanghai University, Shanghai 200444, P. R. China
3. Department of Physics, Dongguk University, Pildong-ro, Choong-gu, Seoul 04620, South Korea
4. School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, P. R. China