Solvation dynamics in SDS micelle revisited with femtosecond time resolution to reveal the probe and concentration dependence

The present work is devoted to understand the probe and surfactant concentration dependence of solvation dynamics in sodium dodecyl sulfate (SDS) micelle. The average solvation times are found to follow the hydrophobicity of the probe and it was concluded that the location of probe inside SDS micelle determines the solvation time. We also studied the solvation dynamics in varying concentrations of SDS in water and found a small but definite increasing trend in solvation time. Rotational diffusion time of the fluorescent probe did not change with change in SDS concentration, which hinted that distortion in the shape of micelle may be the reason behind variation of solvation time. The analysis of solvent response function in all the cases hints towards the existence of an ultrashort (∼100 fs) time component due to the libration motion of water molecules.