The metal ion binding properties of the perfluorosulfonate membrane Nafion® have been investigated in this study. The experiments involve laser-induced fluorescence measurements of europium (III) ions which are bound to the membrane. By the exploitation of the hypersensitivity of the <i>D → F</i> transitions of europium (III) to the ligand binding environment, the properties of the metal binding sites have been analyzed as a function of various experimental parameters. The spectra and fluorescence lifetime measurements provide evidence for distinct metal binding sites within the polymer, each of which is sensitive to the conditions of the membrane preparation.
E. K. L. Wong and G. L. Richmond, "Metal Ion Binding Properties of Perfluorosulfonate Membranes by Laser Excitation Spectroscopy," Appl. Spectrosc. 42, 293-295 (1988)