Effect of NaCl on the binding constant of styryl pyridinium dyes in anionic surfactant system

Perturbation of micelle structure by salt plays a vital role in micellar growth. Cationic alkyl styryl pyridinium dyes are found to interact differently with anionic surfactant systems according to their structural differences. In this work the binding constant of some tailor made styryl pyridinium dyes (1) in ground state and excited state has been studied in anionic sodium dodecyl sulfate (SDS) in the presence and absence of NaCl using absorption and steady state fluorescence spectroscopy. Larger binding constant of the dyes in the excited state compared to the ground state has been explained in terms of flexibility of dyes in excited state. The highest binding constant value for C12 is attributed to the compatibility of the hydrophobic chain of both the surfactant and the dye.