Ion-exchange selectivity of Nafion films on electrode surfaces

Szentirmay, Marilyn N.; Martin, Charles R.

doi:10.1021/ac00275a031

Cited by 317 publications

(216 citation statements)

References 39 publications

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“…4,5,18 This incorporation (or doping) process allowed dramatic improvements in detection capabilities and electrocatalytic applications of Nafion ® coated electrodes with respect to conventional uncoated electrodes. 8,9 However, it was shown that the properties of recasted Nafion ® films depend strongly on the deposition conditions, 19 6 ] 3+ solution and transferred into pure supporting electrolyte (10 -2 mol dm -3 NaNO 3 ).…”

Section: Cyclic Voltammetrymentioning

confidence: 99%

“…15 In the present work we examine in detail the charge transfer and diffusion behavior of electroactive probe based on cations such as Ru[(NH 3 ) 6 ] 3+ , incorporated by ion-exchange in Nafion ® LS films deposited on electrode surfaces in comparison with "traditional" coatings deposited by solvent evaporation of recasted Nafion ® solutions. 3,4,18 …”

Section: Introductionmentioning

confidence: 99%

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Preparation and voltammetric characterization of electrodes coated with Langmuir-Schaefer ultrathin films of Nafion®

Bertoncello¹,

Ugo²

2003

J. Braz. Chem. Soc.

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Filmes ultrafinos do polímero perfluorado Nafion ® foram depositados em eletrodos de óxido índio-titânio (ITO) usando a técnica de Langmuir-Scaefer (LS), depois da otimização das condições de composição da subfase. As características morfológicas das camadas foram obtidas por Microscopia de Força Atômica (AFM). Filmes de Nafion ® LS mostraram boa uniformidade e cobertura completa da superfície do eletrodo. No entanto, diferentes graus de organização das camadas poliméricas ficaram evidentes com respeito a filmes finos depositados por revestimento rotacional. Eletrodos ITO modificados com camadas de Nafion ® LS, pré-concentrados por cátions eletroativos de troca iônica, como o Ru[(NH 3 ) 6 ] 3+ , dissolveram-se em soluções diluídas. A espécie eletroativa foi retida pelo ITO com camada de Nafion ® LS, mesmo depois da mudança do eletrodo modificado para eletrodo de suporte purificado. Isto possibilitou o uso do complexo de rutênio como padrão voltamétrico para o teste do fenômeno de difusão nos filmes de Nafion ® LS. Os coeficientes de difusão aparentes (D app ) do Ru[(NH 3 ) 6 ] 3+ incorporado no filme de Nafion ® LS foram obtidos por medidas voltamétricas. Os valores de D app diminuíram levemente com o aumento da quantidade de complexo de rutênio incorporado no filme ultrafino e foram significativamente mais baixos do que os valores para filmes de Nafion ® recapados, em acordo com a natureza altamente condensada dos filmes de Nafion ® LS.Ultrathin films of Nafion ® perfluorinated polymer were deposited on indium-tin oxide electrodes (ITO) by using Langmuir-Schaefer (LS) technique, after optimization of the subphase composition conditions. Morphological characteristics of these coatings were obtained by Atomic Force Microscopy (AFM). Nafion ® LS films showed a good uniformity and complete coverage of the electrode surface, however a different organization degree of the polymer layer was evidenced with respect to thin films deposited by spin-coating. ITO electrodes modified with Nafion ® LS coatings preconcentrate by ion-exchange electroactive cations, such as Ru[(NH 3 ) 6 ] 3+ , dissolved in diluted solutions. The electroactive species is retained by the Nafion ® LS coated ITO also after transfer of the modified electrode into pure supporting electrolyte. This allowed the use of the ruthenium complex as voltammetric probe to test diffusion phenomena within the Nafion ® LS films. Apparent diffusion coefficients (D app ) of Ru[(NH 3 ) 6 ] 3+ incorporated in Nafion ® LS films were obtained by voltammetric measurements. D app values decrease slightly by increasing the amount of ruthenium complex incorporated in the ultrathin film. They are significantly lower than values typical for recasted Nafion ® films, in agreement with the highly condensed nature of the Nafion ® LS fims.Keywords: Langmuir-Schaefer films, Nafion ® , modified electrodes, Ru[(NH 3 ) 6 ] 3+ , diffusion coefficients IntroductionNafion ® , a copolymer of tetrafluoroethylene and sulfonyl fluoride vinyl ether, is one of the most interesting solid polyme...

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Section: Cyclic Voltammetrymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Preparation and voltammetric characterization of electrodes coated with Langmuir-Schaefer ultrathin films of Nafion®

Bertoncello¹,

Ugo²

2003

J. Braz. Chem. Soc.

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“…coated glassy carbon electrodes. Szentirmay and Martin ( 5 ) have studied the electrochemistry of methyl viologen and ruthenium complexes at the Nafion-coated glassy carbon electrode. They measured exchange constants on the order of lo4 for the hydrophobic cations.…”

Section: Introductionmentioning

confidence: 99%

Nafion-coated mercury-coated glassy carbon electrodes for metals analysis and speciation

Guy¹,

Namaratne²

1987

Can. J. Chem.

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This paper is dedicated to Professor Douglas E. Ryan on the occasion of his 65th birti~dayROBERT D. GUY and SARATH NAMARATNE. Can. J . Chem. 65, 1133 (1987). The properties of mercury-coated glassy carbon electrodes coated with a thin membrane of Nafion 1 17 were studied to evaluate the potential analytical applications in metal ion analysis. The Nafion membrane was found to contain two types of binding sites -a strong site that bound metal ions in a nonelectroactive form and cation exchange sites that were useful for preconcentrations prior to differential pulse voltammetry. The exchange constants for the weak sites ranged from 0.413 for copper to 12.5 for methyl viologen. The differential pulse currents were increased by a factor of 75 to 100 and a linear calibration curve was observed from about 25 nM to 1000 nM for copper, lead, cadmium, and zinc. The ion exchange reaction is very sensitive to ionic strength and significant enrichments occur only in solutions of ionic strength below 0.10. The Nafion-coated glassy carbon electrode in a flow cell can be used to determine the free copper ion concentration in samples by a combination of ion exchange and differential pulse voltammetry. The flow-through system required about 15 mL of sample solution and an analysis time of about 10 min. The ion exchange measurement gave a linear calibration from 40 nM to 10 p M for free copper. IntroductionVoltammetric techniques provide a sensitive method for the detection and quantification of inorganic and organic species in aqueous and organic solutions. The modification of electrodes has recently provided methods to improve both the selectivity and sensitivity of voltammetric methods. Wang and co-workers (1, 2) have coated a mercury-coated glassy carbon electrode (MCGCE) or glassy carbon electrode with a cellulose acetate membrane. The membrane was hydrolyzed with base to form a porous structure. The membrane acts like a miniature dialysis membrane and reduced the adsorption interferences from organic substances. A second approach to altering the selectivity of voltammetric methods is to form a species that adsorbs onto the mercury surface. Wang and Mahmoud (3) have used adsorptive preconcentration to determine titanium in natural waters. A third approach is to form a permanent membrane on the electrode surface that chemically reacts with metal ions in solution. Polymer-coated electrodes with attached chelating groups have been shown (4) to selectively preconcentrate iron and copper.

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“…The Ru(bpy) measurements. 30 Here, Ru(bpy) 2 and z, where z is the charge on the probe initially equilibrated into the Nafion film from solution.…”

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confidence: 99%

Electron Hopping of Tris (2,2^′-bipyridyl) Transition Metal Complexes M(bpy)^2/3₃in Nafion

Gellett

Knoche

Rathuwadu

et al. 2016

J. Electrochem. Soc.

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Voltammetric currents of transition metal complexes in films on electrodes increase with electron self exchange (hopping) rate k11. In films, diffusion coefficients Df∝k11c*f, where k11 sets frequency of electron hopping attempts and c*f film concentration sets distance between probes. Cyclic voltammetry of Nafion films on electrodes for six probes, tris(2,2′-bipyridyl) complexes, M(bpy)z +3 where Mz + is Ru2+, Os2+, Fe2+, Cr3+, Co3+, and Co2+, demonstrates Df varies linearly with kH2O11, literature k11 measured in water. From density of Ru(bpy)2 +3 exchanged Nafion 1.95 g/cm3 and nominal equivalent weight 1100, geometry establishes volume limited, z-independent c*f for all M(bpy)z +3. For concentrations of Ru(bpy)2 +3 in HNO3 where either Ru(bpy)2 +3: HNO3 ratio is fixed or Ru(bpy)2 +3 is 1 mM and HNO3 varies, c*f is statistically invariant. Based on aqueous titrations and dielectric constant sufficient to support ions, electron hopping is confined to hydrated domains of Nafion. From c*f, k11 in Nafion kNaf11 is estimated as k11Naf=0.010k11H2O, consistent with higher ion concentration in Nafion. Measured Df is 2 × 10− 9 cm2/s for Ru(bpy)2 +3 and Os(bpy)2 +3; 1 × 10− 10 cm2/s for Fe(bpy)2 +3 and Cr(bpy)3 +3; and 1.5 × 10− 12 and 5 × 10− 12 cm2/s for Co(bpy)2 +3 and Co(bpy)3 +3. For physical diffusion Dp ≲ 10− 12 cm2/s. A self consistent view of M(bpy)z +3 self exchange in Nafion is outlined. For Os(bpy)2/33, kH2O11 ≈ 4.5 × 108/Ms.

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Ion-exchange selectivity of Nafion films on electrode surfaces

Cited by 317 publications

References 39 publications

Preparation and voltammetric characterization of electrodes coated with Langmuir-Schaefer ultrathin films of Nafion®

Preparation and voltammetric characterization of electrodes coated with Langmuir-Schaefer ultrathin films of Nafion®

Nafion-coated mercury-coated glassy carbon electrodes for metals analysis and speciation

Electron Hopping of Tris (2,2^′-bipyridyl) Transition Metal Complexes M(bpy)^2/3₃in Nafion

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Ion-exchange selectivity of Nafion films on electrode surfaces

Cited by 317 publications

References 39 publications

Preparation and voltammetric characterization of electrodes coated with Langmuir-Schaefer ultrathin films of Nafion®

Preparation and voltammetric characterization of electrodes coated with Langmuir-Schaefer ultrathin films of Nafion®

Nafion-coated mercury-coated glassy carbon electrodes for metals analysis and speciation

Electron Hopping of Tris (2,2′-bipyridyl) Transition Metal Complexes M(bpy)2/33in Nafion

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Electron Hopping of Tris (2,2^′-bipyridyl) Transition Metal Complexes M(bpy)^2/3₃in Nafion