Solid-Matrix Luminescence Polarization of p-Aminobenzoate Adsorbed on Sodium Acetate and Sodium Acetate/Sodium Chloride Mixtures

Abstract

Luminescence polarization values for the anion of p-aminobenzoic acid adsorbed on sodium acetate were obtained over a wide temperature range. Also, luminescence polarization values were obtained for p-aminobenzoate on a variety of sodium acetate/NaCl mixtures at 296 and 93 K. For the anion of p-aminobenzoic acid adsorbed on sodium acetate, the fluorescence and phosphorescence polarization values were essentially constant with temperature. The phosphorescence polarization data indicated that the anion of p-aminobenzoic acid did not undergo rotational relaxation over the temperature range investigated; thus rotational processes did not contribute to nonradiative deactivation. Vibrational processes were primarily responsible for the decrease in phosphorescence quantum yields as the temperature increased. For the luminescence polarization data with the sodium acetate/NaCl mixtures, little change was observed for both the fluorescence polarization data and phosphorescence polarization data at the two different temperatures. These data indicated, along with earlier luminescence quantum yield data, that the three-dimensional bonding characteristics of the solid-matrix are very important in obtaining a high luminescence yield.