Luminescence Probe Studies of Pyrene and Two Charged Derivatives in Nafion

Abstract

The luminescence and absorption properties of pyrene, trimethylbyren-1-y1)ammonium chloride (tmpa) and sodium pyrene-1-sulfonate (sps) incorporated into the perfluorosulfonate membrane Nafion have been investigated. Addition of pb²⁺ induces a redistribution of pyrene molecules from the hydrophilic domains to more hydrophobic domains of the membrane and results in phosphorescence emission. tmpa is shown to bind strongly to the negatively charged sulfonate groups and does not exhibit phosphorescence nor is it displaced by pb2+. The fluorescence emission and absorption characteristics of sps incorporated in Nafion suggest a hydrophilic microenvironment, probably the water cluster region. The electrostatically unfavourable interaction, however, results in excimer formation even at low probe concentrations. Dynamic and steady-state fluorescence quenching measurements provide further insight into the nature of the different regions of Nafion.