Photophysical properties of the phenoxazin dyes resazurin and resorufin in soybean lecithin microemulsions

Photophysical properties of resazurin and resorufin were investigated in a homogeneous solution of binary solvent mixtures (isooctane/1-propanol) and in soybean lecithin microemulsions. Resorufin does not show any important changes in the position of either absorption or fluorescence bands when lecithin is added to the mixture isooctane-1-propanol; when microemulsions are formed by the addition of water, a new band appears in the absorption and fluorescence spectra of the dye with an isosbestic or isoemissive point. In contrast, resazurin presents a clear dependence in the absorption and emission spectra with the concentration of lecithin in the isooctane-1-propanol mixture and with the water content. Triplet state properties were also investigated. The results are discussed in terms of the localization of the dyes in the microheterogeneous systems.