Effect of NaCl on the spectral and kinetic properties of cresyl violet (CV)-sodium dodecyl sulphate (SDS) complex

Effect of added NaCl on the spectral and kinetic properties of cationically charged dye (cresyl violet) and anionically charged surfactant (sodium dodecyl sulphate) were studied in the pre-micellar and micellar regions. Addition of 0.2 M NaCl to dye-surfactant solution decreased the critical micellar concentration for the micellization of the dye in sodium dodecyl sulphate to 1.2 × 10⁻³ M. Time-resolved studies using a stopped-flow spectrometer showed that NaCl influences the dynamics of micellisation. Addition of NaCl during the dye-surfactant complex formation converted the complex into micellized form at NaCl concentration of 0.01 to 0.05 M. In contrast, much higher concentration of NaCl (2 M) is required for the salting-out effect of the dye-surfactant complex for conversion to the micellized form