1. Department of Chemistry Philipps-Universität Marburg Hans-Meerwein-Strasse 4 35032 Marburg Germany
2. Institute for Applied Materials (IAM) Institute of Nanotechnology (INT), and Karlsruhe Nano Micro Facility (KNMF) Karlsruhe Institute of Technology 76344 Eggenstein-Leopoldshafen Germany
3. Department of Mathematics TU Kaiserslautern Gottlieb-Daimler-Strasse 67663 Kaiserslautern Germany