1. School of Chemistry & Environmental Engineering, Changchun University of Science and Technology, Changchun 130022, P. R. China
2. School of Materials Science and Engineering, Harbin Institute of Technology (Weihai), Weihai 264209, P. R. China
3. School of Opto-Electronic Science, Changchun College of Electronic Technology, Changchun 130061, P. R. China