1. Key Laboratory of Synthetic and Natural Functional Molecule Chemistry Ministry of Education College of Chemistry and Materials Science Northwest University Xi'an 710127 P. R. China
2. Gaoxin No. 1 High School Xi'an 710065 P. R. China
3. Key Laboratory of Applied Surface and Colloid Chemistry Ministry of Education School of Chemistry and Chemical Engineering Shaanxi Normal University Xi'an 710199 P. R. China