1. School of Chemistry and Environmental Engineering, China University of Mining and Technology-Beijing, Beijing 100085, China
2. Key Laboratory of Environmental Nano-technology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, P. R. China
3. Institute of Biological Information Processing IBI-4, Forschungszentrum Jülich, Leo-Brandt-Str, Jülich D-52425, Germany
4. Department of Physics, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, D-40225 Düsseldorf, Germany