1. Department of Chemistry Biology and Biotechnology and Center of Excellence on Innovative Nanostructured Materials (CEMIN), University of Perugia, via Elce di Sotto n.8, 06123 Perugia, Italy
2. LENS (European Laboratory for Non−Linear Spectroscopy), via N. Carrara 1, Sesto Fiorentino, 50019 Firenze, Italy
3. INO-CNR, Istituto Nazionale di Ottica—Consiglio Nazionale delle Ricerche, Largo Fermi 6, 50125 Firenze, Italy
4. Department of Chemical Sciences, University of Catania, viale Andrea Doria 6, 95125 Catania, Italy