FLUORESCENCE STUDIES ON THE ADSORPTION OF OCTADECYLRHODAMINE B ONTO A LATEX SURFACE

Abstract— The interaction of octadecylrhodamine B (ORB), a lipid-conjugated dye, with polystyrene latex in aqueous dispersions has been investigated by fluorescence techniques. The dependence of the fluorescence intensity of ORB on the latex concentration indicates that the dye is effectively adsorbed onto the latex surface from the aqueous phase and that deaggregation to fluorescent monomers from the nonfluorescent multimers takes place cooperatively when the surface coverage of the dye is reduced to a critical value. The fluorescence lifetime increases on going from a homogeneous methanolic solution to the latex dispersion, showing that the mobility of the probe is suppressed on the latex surface. From the results of polarization measurements, it is proposed that ORB molecules are adsorbed on the latex surface by a side-on geometry. The influence of a nonionic surfactant, triton X-100, on the fluorescence intensities of ORB and rhodamine B in the latex dispersion is also investigated.