1. School of Life Science and Technology Harbin Institute of Technology Harbin 150080 P. R. China
2. School of Physics Harbin Institute of Technology Harbin 150080 P. R. China
3. School of Biotechnology and Health Sciences Wuyi University Jiangmen 529020 P. R. China
4. Key Laboratory of UV Light Emitting Materials and Technology of Ministry of Education Northeast Normal University Changchun 130024 P. R. China