Photophysical Properties of Safranine T in Aqueous Glycol Oligomer Mixtures

Abstract

The photophyscial behavior of the dye Safranine T in the ground and excited states in aqueous mixtures of glycol oligomers was investigated by absorption and fluorescence spectroscopic techniques. The formation of a 1:1 complex in the excited state was inferred from fluorescence studies. The calculated equilibrium constants of the complex are directly proportional to the molar mass of the glycol. Microviscosity values of the aqueous glycol mixtures were determined by employing Auromine O as a fluorescence probe. Stokes shift values were correlated with the bulk dielectric constant and the microviscosity of the media. Also employing Stokes shifts, solvent parameters such as the Kowoser Z values and the intramolecular charge transfer energy, E T (30), were evaluated. The fluorescence quenching of Safranine T by the inorganic ions [Fe(CN)6]3−, [Fe(CN)6]4−, and [I]− in aqueous oligomer mixtures at a fixed concentration was investigated. The ions influenced the quenching process to different extents, and the efficiency of quenching of the dye in the glycol media for [Fe(CN)6]4− and [I]− ions follows the order EG > DEG > TEG > TTEG. In the case of ferricyanide ion the reverse order was observed. The microviscosity and bulk dielectric constant of the media played a major role in the collisional quenching process.