1. a Department of Chemical Engineering, Lianyungang Technical College , Lianyungang , P. R. China
2. b Department of Chemistry , University of Science and Technology of China , Hefei , P. R. China
3. c Center Lab , Shantou University , Shantou , P. R. China
4. d Materials of Science and Engineering , University of Science and Technology of China , Hefei , P. R. China