1. Institute for Nanostructures, Nanomodelling and Nanofabrication and Department of Physics, University of Aveiro, 3810-193 Aveiro, Portugal
2. Walter Schottky Institut, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
3. Institut für Verbrennung und Gasdynamik and CeNIDE, Universität Duisburg-Essen, 47048 Duisburg, Germany
4. Department of Chemistry and CICECO, University of Aveiro, 3810-193 Aveiro, Portugal