1. Centre for Materials Science and Nanotechnology, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway
2. Department of Physics, University of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo, Norway
3. SINTEF Materials and Chemistry, Department of Hydrocarbon Process Chemistry, P.O. Box 124 Blindern, N-0314 Oslo, Norway