1. Theory Modelling and Design Centre, Tyndall National Institute, University College Cork, Cork, Ireland
2. Department of Chemistry, University of Basel, St. Johanns-Ring 19, CH-4056 Basel, Switzerland
3. Micro/Nanoelectronics Centre, Tyndall National Institute, University College Cork, Cork, Ireland
4. Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), P.O. Box 3640, D-76021 Karlsruhe, Germany