1. Molecular Photonics Group, Van’t Hoff Institute for Molecular Sciences, Universiteit van Amsterdam, Science Park 904, P.O. Box 94157, 1090 GD Amsterdam, The Netherlands
2. Department of Chemistry, University of Fribourg, Chemin du Musée 9, 1700 Fribourg, Switzerland
3. Kavli Institute of Nanoscience, National Centre HREM, Lorentzweg 1, 2628 CJ Delft, The Netherlands
4. Physikalisches Institut, Westfälische Wilhelms-Universität Münster, Mendelstrasse 10, D-48149 Münster, Germany