1. School of Physics and Information Technology, Shaanxi Normal University, Xi'an 710061, PR China
2. Institute of Nanomaterials, Amer International Group Co. Ltd, Weinan, 715100, PR China
3. Institute of Physics and Electronic Information, Yunnan Normal University, Kunming 650500, P.R. China
4. Key Laboratory of Aerosol Chemistry and Physics, State Key Laboratory of Loess and Quaternary Geology (SKLLQG), Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, 710061, China