1. School of Arts and Sciences, Shanghai Dianji University, Shanghai 201306, P. R. China
2. Shanghai Applied Radiation Institute, Shanghai University, Shanghai 200444, P. R. China
3. School of Materials Science, Shanghai Dianji University, Shanghai 201306, P. R. China
4. Key Laboratory of Silk Engineering of Jiangsu Province, Soochow University, Suzhou 215123, P. R. China