1. College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai 201620, P. R. China
2. National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, 199 Ren-ai Road, Suzhou 215123, P. R. China
3. College of Mathematics and Statistics, Qujing Normal University, Sanjiang Street, Qujing 655011, P. R. China