The Effects of Fluorescent Brightening Agents of Pyrazoline Type on the Photofading of Acid Azo Dyes in the Aqueous Solutions

Abstract

Azo dyes [1]∼[4] fade in aqueous solution on irradiation with the light of the wavelength shorter than 300 nm. A fluorescent brightener of pyrazoline type (F_wo) accelerates the photofading of the dyes in the presence of the dissolved oxygen (Fig. 3). The acceleration is particularly marked with the wavelengths corresponding to the excitation maximum of the fluorescent brightener. On the other hand the dyes quench the photoreaction of the fluorescent brightener. The paper-chromatographic analyses of the photoproducts (Fig. 6) and the sensitization studies with biacetyl reveal that the fluorescent brightener sensitizes the inherent photoreactions of the dyes through the triplet energy transfer.