Dynamic fluorescence spectroscopic study on the microstructures in ion- exchange resin particles

The fluorescence dynamics of Rhodamine B (RhB) and excitation energy transfer from RhB to Malachite Green (MG) in cation-exchange resin particles were studied with special reference to elucidating effects of the cross- linking density of the resin on the fluorescence dynamics. In the cation- exchange resin, the fluorescence lifetime and rotational relaxation time of RhB were very slow compared to those determined in an aqueous solution, suggesting strong binding of the dye to the ion; exchange group of the resin. Therefore, the spatial distribution characteristics of the dye in the resin particle was used as a measure for that of the ion-exchange group. The apparent structural dimension determined by the fractal dimension analysis of energy-transfer quenching of RhB by MG, representing the distribution characteristics of the dye in the resin, was smaller than Euclidean dimension (3) and decreased from 2.8 to 2.6 with decrease in the cross-linking density of the resin from 8 to 2%. The origin of the fractal-like distribution of the dye and, thus, that of the ion-exchange group was discussed.