1. State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Institute of Biochemical Engineering & Environmental Technology, Lanzhou University, Lanzhou 730000, People's Republic of China.
2. College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P.R. China. Phone: 86-931-8912528; Fax: 86-931-8912113; E-mail: liyf@lzu.edu.cn