1. Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
2. Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 GJ Delft, The Netherlands
3. Institute of Physics, University of Augsburg, Universitätsstraße 1, 86159 Augsburg, Germany
4. Institute for Nanotechnology, Karlsruhe Institute of Technology (KIT), P. O. Box 3640, 76021 Karlsruhe, Germany
5. Lehn Institute of Functional Materials, School of Chemistry, Sun Yat-Sen University, Guangzhou 510274, P. R. China