PHOTOPHYSICS OF THE PHENOXAZINE DYES RESAZURIN

GABRIELA V. PORCAL, CARLOS M. PREVITALI AND SONIA G. BERTOLOTTI

DYES AND PIGMENTS

Elsevier

Año: 2009

0143-7208

The photophysics of the phenoxazin-3-one dyes resazurin (RZ) and resorufin (RF) have been studied in micellar solution of cetyltrimethylammonium chloride (CTAC) and in reverse micelles of 1, 4-bis (2- ethylhexyl)sulfosuccinate (AOT) and benzylhexadecyldimethylammonium chloride (BHDC). Absorption and fluorescence emission spectra, as well as fluorescence lifetimes and T-T transient absorption spectra were determined as a function of surfactant concentration. In the presence of direct micelles of the cationic surfactant CTAC both dyes present red shifts in theabsorption and fluorescence spectra at the same time that the fluorescence lifetime increases and the photophysical parameters resemble those in a medium of polarity similar to ethanol. Theelectrostatic attraction between the anionic dyes and the positive micellar interface favor thelocation of the dyes closer to the head groups of the surfactant molecules.In reverse micellar systems the spectral properties depends upon the charge of the surfactant and the water content. With AOT, at low water content both dyes are incorporated into the interface and as the water content increases their spectral properties tend to those in pure water. On the other hand, with the cationic surfactants BHDC the dyes are located in the interfacial pseudophase due to the electrostatic interactions. In the case of RF at low water content the dye senses a low polarity medium similar to benzene. With increasing the water content it remains in the interfacial region, but now in a more polar environment. The dye with the N-oxide group, RZ remains in the polar region of the interface, independent of the water content.