1. School of Material Science and Engineering; State Key Laboratory of Gansu Advanced Non-Ferrous Metal Materials, Lanzhou University of Technology; Lanzhou 730050 China
2. Department of Chemistry and Biochemistry; University of California; 1156 High Street Santa Cruz CA 95064 USA
3. College of Polymer Science and Engineering; State Key Laboratory of Polymer Materials Engineering, Sichuan University; Chengdu 610065 China
4. College of Life Science and Engineering; Lanzhou University of Technology; Lanzhou 730050 China