Résumé
Second Harmonic Generation (SHG) was used to study the optical properties of molecular films formed at liquid interface (air-water or dodecane-water interfaces). The technique was applied to a two-dimensional film of hemicyanine molecules: dye (4-(4-dihexadecylaminostyryl)-N-methylpyridinium iodide) (DiA) and 4-(4-(diethylamino)styryl)-N-methylpyridinium iodide (sDiA). First, at the air-water interface, the SHG intensity was measured as a function of the incident fundamental and outgoing harmonic wave polarization. The orientation of the molecules was determined by the analysis of the polarization plots. In the case of DiA molecules, the formation of aggregates at the air-water interface was then monitored by the analysis of SHG intensity fluctuations. Finally, the adsorption of sDiA at the dodecane-water interface was characterized by the SHG technique.