Interaction of ketocyanine dyes with cationic, anionic and neutral micelles

Interaction of ketocyanine dyes with cationic (CTAB), anionic (SDS) and neutral (Triton X-100) micelles has been studied by monitoring the polarity-sensitive absorption and fluorescence band of the solute. The position of equilibrium between the bare form of the dye (S 0 state) and its hydrogen-bonded complex with water is modified by the micellar medium, the percentage of the hydrogen-bonded species being maximum is SDS, while it is minimum in CTAB. The negative carbonyl centre of the dye avoids the anionic micelle (SDS) and is effectively hydrogen bonded by water. Fluorescence band maximum provides the micropolarity of the micelle-water interface and the local dielectric constant and E T (30) value determined agree well with the value for the micellar medium reported in the literature. The possible orientation of the dye in the proximity of the micelle has also been discussed.