Nafion

About: Nafion is a research topic. Over the lifetime, 9110 publications have been published within this topic receiving 320865 citations.

High-Resolution Imaging of Ionic Domains and Crystal Morphology in Ionomers Using AFM Techniques

Abstract: AFM methods were applied to resolve the surface and near-surface morphology of the ionic domains in Nafion membranes, Surlyn ionomers, and other ionomers. The ionic clusters were resolved by a new tapping AFM method where low oscillation amplitudes were used, and tip−ionic domain interactions were apparently able to dominate the signal allowing nanometer-level resolution of the domains. In other operating modes, the fluoropolymer crystal or aggregate domains were imaged using tapping AFM by the normal “stiffness” contrast. By sequential images taken under different AFM conditions, the “softer” fluorine-depleted regions were found to contain ionic domains in the same topographical areas, and the changes due to swelling by water were examined in one case. A third AFM operating mode was used to examine the composition in the outermost few angstroms of the surface. Data proving the existence of a very thin fluorine-rich “barrier” layer covering the entire surface of Nafion are obtained, and its relevance to v...

Photocatalytic reactivities of Nafion-coated TiO2 for the degradation of charged organic compounds under UV or visible light.

Abstract: Nafion (perfluorinated polymer with sulfonate groups)-coated TiO2 particles (Nf/TiO2) were prepared and their reactivities for the photocatalytic degradation (PCD) of charged organic substrates were investigated. The presence of Nafion adlayers drastically changed the positive TiO2 surface charge to a negative one over the entire pH range and significantly influenced the PCD kinetics and mechanisms. The UV-induced PCD of tetramethylammonium (TMA; cationic substrate) was greatly enhanced in the presence of Nafion adlayers on TiO2 because the ion-exchange sites within the Nafion can hold cationic substrates. On the other hand, despite the unfavorable electrostatic interaction between the Nf/TiO2 and anionic substrates, the PCD of dichloroacetate (DCA) and acid orange 7 (AO7) with Nf/TiO2 was not significantly inhibited. The visible-light-sensitized degradation of dyes was enhanced with Nf/TiO2 not only for cationic dyes (methylene blue (MB) and rhodamine B (RhB)) whose uptake on Nf/TiO2 is enhanced, but als...

Interpretation of the Small-Angle X-ray Scattering from Swollen and Oriented Perfluorinated Ionomer Membranes

Abstract: Small-angle X-ray scattering (SAXS) and bulk volumetric measurements were performed on the perfluorinated ionomer membrane “Nafion”. The swelling experiments were conducted using controlled environments of different relative humidities. The membranes were oriented using uniaxial draw, both before and after conversion of the precursor material, as well as both sequential and simultaneous biaxial draw. Using a novel model-independent maximum entropy method, it is shown that the most statistically probable scattering model for Nafion is an ion clustered morphology with a hierarchical scale of structure. The smallest scale is comprised of arrays of roughly spherical ionic clusters. The clusters are agglomerated into higher-order structures, whose shape is determined by the spatial coherence of the clusters, as inferred from the SAXS measurements. Anomalies in the magnitudes of the microscopic and macroscopic swellings are shown to be caused by the rearrangement of ionic material, producing changes in the numb...

Electrogenerated chemiluminescence from tris(2,2'-bipyridyl)ruthenium(II) immobilized in titania-perfluorosulfonated ionomer composite films

Abstract: Electrochemical behavior and electrogenerated chemiluminescence (ECL) of tris(2,2‘-bipyridyl)ruthenium(II) (Ru(bpy)32+) immobilized in sol−gel-derived titania (TiO2)−Nafion composite films coated on a glassy carbon electrode have been investigated. The electroactivity of Ru(bpy)32+ ion exchanged into the composite films and its ECL behavior were strongly dependent upon the amount of Nafion incorporated into the TiO2−Nafion composite films. The ECL sensor of Ru(bpy)32+ immobilized in a TiO2−Nafion composite with 50% Nafion content showed the maximum ECL intensities for both tripropylamine (TPA) and sodium oxalate in 0.05 M phosphate buffer solution at pH 7. Detection limits were 0.1 μM for TPA and 1.0 μM for oxalate (S/N = 3) with a linear range of 3 orders of magnitude in concentration. The present ECL sensor showed improved ECL sensitivity and long-term stability, as compared to the ECL sensors based on pure Nafion films. The present Ru(bpy)32+ ECL sensor based on TiO2−Nafion (50%) composite films was ap...

Biocompatible PEDOT:Nafion composite electrode coatings for selective detection of neurotransmitters in vivo.

Abstract: A Nafion and poly(3,4-ethylenedioxythiophene) (PEDOT) containing composite polymer has been electropolymerized on carbon-fiber microelectrodes with the goal of creating a mechanically stable, robust, and controllable electrode coating that increases the selectivity and sensitivity of in vivo electrochemical measurements. The coating is deposited on carbon-fiber microelectrodes by applying a triangle waveform from +1.5 V to −0.8 V and back in a dilute solution of ethylenedioxythiophene (EDOT) and Nafion in acetonitrile. Scanning electron microscopy demonstrated that the coating is uniform and ∼100 nm thick. Energy-dispersive X-ray spectroscopy demonstrated that both sulfur and fluorine are present in the coating, indicating the incorporation of PEDOT (poly(3,4-ethylenedioxythiophene) and Nafion. Two types of PEDOT:Nafion coated electrodes were then analyzed electrochemically. PEDOT:Nafion-coated electrodes made using 200 μM EDOT exhibit a 10–90 response time of 0.46 ± 0.09 s versus 0.45 ± 0.11 s for an unc...