1. Department of Chemistry “Ugo Schiff”; University of Florence; via della Lastruccia 3-13 50019 Sesto Fiorentino Italy
2. European Laboratory for Non-linear Spectroscopy; via Nello Carrara 1 50019 Sesto Fiorentino Italy
3. National Institute of Optics; National Research Council; via Nello Carrara 1 50019 Sesto Fiorentino Italy
4. Department of Physics and Astronomy; University of Florence; Via Sansone, 1 50019 Sesto Fiorentino Italy
5. Istituto Nazionale di Ricerca Metrologica INRiM; Strada delle Cacce, 91 10135 Turin Italy
6. CSGI; Center for Colloids and Interface Science; via della Lastruccia, 3 50019 Sesto Fiorentino Italy
7. Department of Biochemical; Experimental and Clinical “Mario Serio”; Viale Morgagni 50 50134 Firenze Italy