1. Department of Physics “E. Pancini”, University of Naples Federico II, Napoli, Italy
2. INSTM-GISEL, National Interuniversity Consortium of Materials Science and Technology (INSTM), Florence, Italy
3. Department of Chemical Sciences, University of Naples Federico II, Napoli, Italy
4. Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), Portici (NA), Italy