1. Department of Chemistry, Kanbar Laboratory for Nanomaterials, Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 52900, Israel, Department of Physics, Bar-Ilan University, Ramat-Gan 52900, Israel, and Applied Physics Department, Universitat Politecnica de Catalunya, Avenida Canal Olimpic, Castelldefels, 08860 Barcelona, Spain