1. Department of Materials Science and INSTM, University of Milano—Bicocca, Via Cozzi 55, 20125 Milano, Italy
2. Department of Chemistry and INSTM, University of Pavia, Via Taramelli 12, 27100 Pavia, Italy
3. Helmholtz Institute Ulm (HIU), Helmholtzstr. 11, 89081 Ulm, Germany
4. Department of Physics, University of Pavia, Via Bassi 6, 27100 Pavia, Italy
5. Karlsruhe Institute of Technology (KIT), P.O. Box
3640, Karlsruhe 76021, Germany