ELECTRONIC ABSORPTION AND FLUORESCENCE-SPECTRA OF XANTHENE DYES IN POLYMERS

The electronic absorption and fluorescence spectra of fluorescein, fluorescein disodium, erythrosine B and rose bengal in different polymers (poly(vinyl alcohol), poly(vinyl acetate) and polyethylene glycol 600) were studied. It has been noted that fluorescein displays very complex dissociation and ionization equilibria in polymers, depending on the polymer-dye interactions. Its fluorescence emission may be assigned to the neutral zwitterion form in aprotic polymers and solvents. The photophysical properties of fluorescein disodium, erythrosine B and rose bengal are strongly dependent on the polymer-dye interactions and on the internal heavy atom effect. These results are very similar to those obtained for liquid solvents.