Fluorescence dynamics of dye probes in micelles

Abstract

The fluorescence depolarization dynamics of organic fluorescent dye probes (nile red, cresyl violet, DODCI, rhodamine B, and rhodamine DPPE) were studied in cationic, anionic, and neutral micelles by picosecond time-resolved single-photon-counting technique. The fluorescence anisotropy decay of the dye intercalated inside the micelle is a two-exponential function. The anisotropy decay was interpreted by using a model of rotational (wobbling) and translational diffusion of the dye in the micelle coupled with the rotational motion of the micelle as a whole. The rotational and translational diffusion coefficients of the dye, the order parameter, and the semicone angle for the wobbling diffusion in the micelle were determined. The concept of "microviscosity" in the micelle was critically discussed in the light of the rotational and translational diffusion coefficients and their temperature dependence.