1. Department of Chemistry, University of Fribourg, Chemin du Musée 9, 1700 Fribourg, Switzerland
2. Laboratory for Biointerfaces, Empa, Swiss Federal Laboratories for Material Science and Technology, Lerchenfeldstrasse 5, 9014 St. Gallen, Switzerland
3. Department of Chemistry, Umeå University, 90187 Umeå, Sweden