Moisture Quenching of Solid-Matrix Phosphorescence on Hydrophilic and Partially Hydrophobic Filter Papers

Abstract

A detailed investigation was undertaken to determine the important parameters that were responsible for the solid-matrix phosphorescence (SMP) moisture quenching of phosphors adsorbed in Whatman No. 1 (hydrophilic) and Whatman 1PS (partially hydrophobic) papers. The three phosphors used were phenanthrene, perdeuterated phenanthrene, and benzo[ e]pyrene. Both SMP lifetime and SMP intensity data were obtained over a wide range of adsorbed moisture. In addition, moisture isotherms were obtained for the No. 1 and 1PS papers. The SMP lifetimes of phenanthrene and benzo[ e]pyrene were independent of the amount of adsorbed moisture on both the No. 1 and 1PS papers. However, the SMP lifetimes of perdeuterated phenanthrene on No. 1 and 1PS papers were dependent on the extent of the adsorbed moisture. The changes in the SMP intensities as a function of adsorbed moisture for phenanthrene, benzo[ e]pyrene, and perdeuterated phenanthrene on No. 1 paper could be modeled by a simple exponential function with phenanthrene and benzo[ e]pyrene giving better correlations compared to perdeuterated phenanthrene. The change in the modulus of filter paper samples with moisture adsorption was a major factor in causing the SMP intensity to decrease. The decrease in the SMP intensities with moisture adsorption for the three phosphors adsorbed on 1PS paper did not correlate with the simple Stern–Volmer model and several other quenching models discussed in the literature. Thus, these data were fit to a relatively simple empirical equation. The results showed that the SMP quenching phenomena for the three phosphors on No. 1 paper and on 1PS paper were considerably different.