A rhodamine and a cyanine dye on the water surface as studied by laser induced fluorescence microscopy

The properties and behavior of cyanine and rhodamine dyes on the water surface were investigated using a laser-induced fluorescence microscope. The band peaks of the absorption and fluorescence spectra and their Stokes shift of the rhodamine dye on the water surface indicated that the polarity on the water surface is lower than that of bulk water. The rhodamine and cyanine dye molecules formed domains on the water surface. Although RhC18 formed no aggregate on the water surface below Γ=0.7, DiD aggregated significantly even at Γ=0.2 and showed two kinds of domains on the water surface. DiD, however, did not aggregate in the LB film below Γ=0.7 and showed aggregation only at multilayers.