1. State
Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, P. R. China
2. Shannxi
Key Laboratory of Phytochemistry, Baoji University of Arts and Sciences, Baoji 721013, China
3. State
Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical
Physics, Chinese Academy of Science, Lanzhou, 730000, P. R. China