Interaction of Cationic Dye and Anionic Detergent above and below the Critical Micelle Concentration as Revealed by Fluorescence Characteristics

The interaction of 3,3′-diethylthiacarbocyanine iodide, a cationic dye, with sodium dodecyl sulfate (SDS), an anionic detergent, was studied as a function of the concentration of SDS ([SDS]) above and below the critical micelle concentration (cmc). The [SDS]-dependent fluorescence spectra, quantum yield and decay measurements revealed the deaggregation of the dye above the cmc and the formation of the dye–SDS aggregate below the cmc.