1. Department of Chemistry; University of Connecticut; Storrs Connecticut 06269
2. College of Pharmacy; Ningxia Medical University, 750004; Yinchuan Ningxia People's Republic of China
3. Department of Applied Chemistry, School of Sciences; Xi'an University of Technology, 710048; Xi'an Shaanxi People's Republic of China
4. Polymer Program, Institute of Materials Science, University of Connecticut; Storrs Connecticut 06269