1. Key Laboratory of Optoelectronic Technology of Jiangsu Province; School of Physical Science and Technology; Nanjing Normal University; Nanjing 210023 P.R. China
2. School of Optoelectronic Engineering and Grüenberg Research Centre; Nanjing University of Posts and Telecommunications; Nanjing 210023 P.R. China
3. Institute of Applied Chemistry; Taizhou University; Taizhou 318000 P.R. China