Solvation dynamics of DCM in micelles

The solvation dynamics of 4-(dicyanomethylene)-2-methyl-6(p-dimethylaminostyryl) 4H-pyran (DCM) have been studied in neutral (Triton X-100, TX), cationic (cetyl trimethyl ammonium bromide, CTAB) and anionic (sodium dodecyl sulfate, SDS) micelles using picosecond time-resolved Stokes shift. Above the critical micellar concentration for all three micelles, DCM exhibits wavelength-dependent fluorescence decays. At short wavelengths, a fast decay is observed while, at long wavelengths, a distinct growth precedes the decay. The time-dependent Stokes shift indicates that the water molecules in the Stern layer of the micelles relax on a timescale which is markedly slower than the sub-picosecond relaxation dynamics in pure water.