Nonradiative energy transfer in carbocyanine dye compositions inside surfactant micelles

Abstract

Utilizing forced concentration of carbocyanine dye molecules DiI and DiD within a surfactant micelle, we have detected nonradiative transfer of electronic excitation energy for low initial dye concentrations in the aqueous micellar solution. Luminescence and fluorescence anisotropy decay studies allowed us to establish that in the micelles, the hydrophilic head of the dye is in contact with the water while the C18H37 groups are located in the hydrocarbon core of the micelle. We show that due to the structural features of the DiD acceptor molecule, rotational diffusion of the acceptor in the micelle is more free than for the donor DiI, the motion of which is constrained in the micelle.