1. State Key Laboratory of Urban Water Resource and EnvironmentSchool of Chemistry and Chemical EngineeringHarbin Institute of Technology Harbin 150001 China
2. Condensed Matter Science and Technology InstituteHarbin Institute of Technology Harbin 150001 China
3. School of Mathematics and PhysicsUniversity of Lincoln Brayford Pool LN6 7TS UK
4. Department of PhysicsKing's College London The Strand London WC2R 2LS UK
5. H. H. Wills Physics LaboratoryUniversity of Bristol Bristol BS8 1TL UK
6. Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and AstronomyAarhus University Aarhus 8000 Denmark