1. Department of Physics, School of Physical and Mathematical Sciences, Nanjing Tech University, Nanjing, Jiangsu 211816, P. R. China
2. Key Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province, Yancheng Institute of Technology, Yancheng 224051, P. R. China
3. School of Environmental Science and Engineering, Yancheng Institute of Technology, Yancheng, Jiangsu 224051, P. R. China
4. School of Materials Science and Engineering, Yancheng Institute of Technology, Yancheng 224051, P. R. China