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Sample records for nafion membranes modified

  1. Amino-silica modified Nafion membrane for vanadium redox flow battery

    NASA Astrophysics Data System (ADS)

    Lin, Chien-Hong; Yang, Ming-Chien; Wei, Hwa-Jou

    2015-05-01

    A hybrid membrane of Nafion/amino-silica (amino-SiO2) for vanadium redox flow battery (VRB) systems is prepared via the sol-gel method to improve the selectivity of the Nafion membrane, to reduce the crossover of vanadium ions, and to decrease water transfer across the membranes. The sulfonated pores of the pristine Nafion membrane are filled with amino-SiO2 nanoparticles localized by electrostatic interaction. The permeability of vanadium ions through the Nafion/amino-SiO2 hybrid membrane is determined by electrometric titration. The results indicate the crossover of vanadium ions through the hybrid membrane is 26.8% of the pristine Nafion membrane. The presence of amino-SiO2 in the hybrid membrane is verified by X-ray photoelectron spectroscopy (XPS). Nafion/amino-SiO2 hybrid membrane exhibits through plane conductivity about the same as the pristine Nafion membrane. The ion exchange capacity (IEC) of the hybrid membrane is 9.4% higher than that of the pristine Nafion membrane. In addition, Nafion/amino-SiO2 hybrid membrane exhibits a higher coulombic efficiency (CE), voltage efficiency (VE), and energy efficiency (EE) over a range of current densities from 20 to 80 mA cm-2. The performance of VRB with Nafion/amino-SiO2 hybrid membrane varies little around a charge-discharge current density of 80 mA cm-2 for 150 cycles. Thus, the Nafion/amino-SiO2 hybrid membrane can suppress the vanadium ions crossover in VRB.

  2. New composite membranes based on modified Nafion or Flemion for PEM fuel cell application

    NASA Astrophysics Data System (ADS)

    Tian, Huimin

    A new composite membrane based on Nafion or Flemion and Silicotungstic acid (STA) was fabricated using a simple solvent evaporation procedure. The optimum evaporation temperature and the amount of STA have been investigated. The evaporation of solvent can be divided into two steps during membrane preparation. Firstly, the solvent was evaporated at 70°C for two hours. Secondly, the evaporated membrane was kept in an vacuum oven at 135°C overnight. The optimum amount of STA in the casting electrolyte solution is in the range from 5 x 10-4 to 5 x 10-3 M. The obtained cast composite membranes exhibit good thermal and mechanical properties. Study of the ionic conductivity shows that the composite membrane with STA gives a higher ionic conductivity than that without STA. The conductivity of composite membrane increases with the increase of STA concentration. When the STA concentration in the 10mL casting electrolyte solution is 5 x 10-3M, the conductivities of the composite membranes can reach up to 0.120 ohm-1 · cm-1 for Nafion/STA membrane and 0.133 ohm -1 · cm-1 for Flemion/STA membrane. On the other hand, the water uptake measurement shows that the water content of the composite membrane with STA is higher than that of composite membrane without STA. Consequently, due to the high conductivity and the high hydrated abiliy of STA, ionic conductivity and water uptake of the composite membrane can be significantly improved by the addition of STA. The morphology of the composite membrane was studied using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The results of AFM and SEM showed that the STA was uniformly dispersed in the Nafion and Flemion composite membranes. The structure of a composite membrane with STA has been studied by X-ray diffraction (XRD), the fourier transform infrared spectroscopy (FTIR), thermoanalysis and X-ray photoelectron spectroscopy (XPS). The results indicated that STA was successfully introduced into the structure of

  3. Effectively suppressing vanadium permeation in vanadium redox flow battery application with modified Nafion membrane with nacre-like nanoarchitectures

    NASA Astrophysics Data System (ADS)

    Zhang, Lesi; Ling, Ling; Xiao, Min; Han, Dongmei; Wang, Shuanjin; Meng, Yuezhong

    2017-06-01

    A novel self-assembled composite membrane, Nafion-[PDDA/ZrP]n with nacre-like nanostructures was successfully fabricated by a layer-by-layer (LbL) method and used as proton exchange membrane for vanadium redox flow battery applications. Poly(diallyldimethylammonium chloride) (PDDA) with positive charges and zirconium phosphate (ZrP) nanosheets with negative charges can form ultra-thin nacre-like nanostructure on the surface of Nafion membrane via the ionic crosslinking of tightly folded macromolecules. The lamellar structure of ZrP nanosheets and Donnan exclusion effect of PDDA can greatly decrease the vanadium ion permeability and improve the selectivity of proton conductivity. The fabricated Nafion-[PDDA/ZrP]4 membrane shows two orders of magnitude lower vanadium ion permeability (1.05 × 10-6 cm2 min-1) and 12 times higher ion selectivity than those of pristine Nafion membrane at room temperature. Consequently, the performance of vanadium redox flow batteries (VRFBs) assembled with Nafion-[PDDA/ZrP]3 membrane achieved a highly coulombic efficiency (CE) and energy efficiency (EE) together with a very slow self-discharge rate. When comparing with pristine Nafion VRFB, the CE and EE values of Nafion-[PDDA/ZrP]3 VRFB are 10% and 7% higher at 30 mA cm-2, respectively.

  4. Proton Conductivity of Nafion/Ex-Situ Sulfonic Acid-Modified Stöber Silica Nanocomposite Membranes As a Function of Temperature, Silica Particles Size and Surface Modification

    PubMed Central

    Muriithi, Beatrice; Loy, Douglas A.

    2016-01-01

    The introduction of sulfonic acid modified silica in Nafion nanocomposite membranes is a good method of improving the Nafion performance at high temperature and low relative humidity. Sulfonic acid-modified silica is bifunctional, with silica phase expected to offer an improvement in membranes hydration while sulfonic groups enhance proton conductivity. However, as discussed in this paper, this may not always be the case. Proton conductivity enhancement of Nafion nanocomposite membranes is very dependent on silica particle size, sometimes depending on experimental conditions, and by surface modification. In this study, Sulfonated Preconcentrated Nafion Stober Silica composites (SPNSS) were prepared by modification of Stober silica particles with mercaptopropyltriethoxysilane, dispersing the particles into a preconcentrated solution of Nafion, then casting the membranes. The mercapto groups were oxidized to sulfonic acids by heating the membranes in 10 wt % hydrogen peroxide for 1 h. At 80 °C and 100% relative humidity, a 20%–30% enhancement of proton conductivity was only observed when sulfonic acid modified particle less than 50 nm in diameter were used. At 120 °C, and 100% humidity, proton conductivity increased by 22%–42% with sulfonated particles with small particles showing the greatest enhancement. At 120 °C and 50% humidity, the sulfonated particles are less efficient at keeping the membranes hydrated, and the composites underperform Nafion and silica-Nafion nanocomposite membranes. PMID:26828525

  5. Proton Conductivity of Nafion/Ex-Situ Sulfonic Acid-Modified Stöber Silica Nanocomposite Membranes As a Function of Temperature, Silica Particles Size and Surface Modification.

    PubMed

    Muriithi, Beatrice; Loy, Douglas A

    2016-01-28

    The introduction of sulfonic acid modified silica in Nafion nanocomposite membranes is a good method of improving the Nafion performance at high temperature and low relative humidity. Sulfonic acid-modified silica is bifunctional, with silica phase expected to offer an improvement in membranes hydration while sulfonic groups enhance proton conductivity. However, as discussed in this paper, this may not always be the case. Proton conductivity enhancement of Nafion nanocomposite membranes is very dependent on silica particle size, sometimes depending on experimental conditions, and by surface modification. In this study, Sulfonated Preconcentrated Nafion Stober Silica composites (SPNSS) were prepared by modification of Stober silica particles with mercaptopropyltriethoxysilane, dispersing the particles into a preconcentrated solution of Nafion, then casting the membranes. The mercapto groups were oxidized to sulfonic acids by heating the membranes in 10 wt % hydrogen peroxide for 1 h. At 80 °C and 100% relative humidity, a 20%-30% enhancement of proton conductivity was only observed when sulfonic acid modified particle less than 50 nm in diameter were used. At 120 °C, and 100% humidity, proton conductivity increased by 22%-42% with sulfonated particles with small particles showing the greatest enhancement. At 120 °C and 50% humidity, the sulfonated particles are less efficient at keeping the membranes hydrated, and the composites underperform Nafion and silica-Nafion nanocomposite membranes.

  6. Catalyst layers for proton exchange membrane fuel cells prepared by electrospray deposition on Nafion membrane

    NASA Astrophysics Data System (ADS)

    Chaparro, A. M.; Ferreira-Aparicio, P.; Folgado, M. A.; Martín, A. J.; Daza, L.

    The electrospray deposition method has been used for preparation of catalyst layers for proton exchange membrane fuel cells (PEMFC) on Nafion membrane. Deposition of Pt/C + ionomer suspensions on Nafion 212 gives rise to layers with a globular morphology, in contrast with the dendritic growth observed for the same layers when deposited on the gas diffusion layer, GDL (microporous carbon black layer on carbon cloth) or on metallic Al foils. Such a change is discussed in the light of the influence of the Nafion substrate on the electrospray deposition process. Nafion, which is a proton conductor and electronic insulator, gives rise to the discharge of particles through proton release and transport towards the counter electrode, compared with the direct electron transfer that takes place when depositing on an electronic conductor. There is also a change in the electric field distribution in the needle to counter-electrode gap due to the presence of Nafion, which may alter conditions for the electrospray effect. If discharging of particles is slow enough, for instances with a low membrane protonic conductivity, the Nafion substrate may be charged positively yielding a change in the electric field profile and, with it, in the properties of the film. Single cell characterization is carried out with Nafion 212 membranes catalyzed by electrospray on the cathode side. It is shown that the internal resistance of the cell decreases with on-membrane deposited cathodic catalyst layers, with respect to the same layers deposited on GDL, giving rise to a considerable improvement in cell performance. The lower internal resistance is due to higher proton conductivity at the catalyst layer-membrane interface resulting from on-membrane deposition. On the other hand, electroactive area and catalyst utilization appear little modified by on-membrane deposition, compared with on-GDL deposition.

  7. Correlation of Structural Differences between Nafion/Polyaniline and Nafion/Polypyrrole Composite Membranes and Observed Transport Properties

    SciTech Connect

    Schwenzer, Birgit; Kim, Soowhan; Vijayakumar, M.; Yang, Zhenguo; Liu, Jun

    2011-04-15

    Polyaniline/Nafion and polypyrrole/Nafion composite membranes, prepared by chemical polymerization, are studied by infrared and nuclear magnetic resonance spectroscopy, and scanning electron microscopy. Differences in vanadium ion diffusion through the membranes and in the membranes’ area specific resistance are linked to analytical observations that polyaniline and polypyrrole interact differently with Nafion. Polypyrrole, a weakly basic polymer, binds less strongly to the sulfonic acid groups of the Nafion membrane, and thus the hydrophobic polymer aggregates in the center of the Nafion channel rather than on the hydrophilic side chains of Nafion that contain sulfonic acid groups. This results in a drastically elevated membrane resistance and an only slightly decreased vanadium ion permeation compared to a Nafion membrane. Polyaniline on the other hand is a strongly basic polymer, which forms along the sidewalls of the Nafion pores and on the membrane surface, binding tightly to the sulfonic acid groups of Nafion. This leads to a more effective reduction in vanadium ion transport across the polyaniline/Nafion membranes and the increase in membrane resistance is less severe. The performance of selected polypyrrole/Nafion composite membranes is tested in a static vanadium redox cell. Increased coulombic efficiency, compared to a cell employing Nafion, further confirms the reduced vanadium ion transport through the composite membranes.

  8. An in-situ nano-scale swelling-filling strategy to improve overall performance of Nafion membrane for direct methanol fuel cell application

    NASA Astrophysics Data System (ADS)

    Li, Jing; Fan, Kun; Cai, Weiwei; Ma, Liying; Xu, Guoxiao; Xu, Sen; Ma, Liang; Cheng, Hansong

    2016-11-01

    A novel in-situ nano-scale swelling-filling (SF) strategy is proposed to modify commercial Nafion membranes for performance enhancement of direct methanol fuel cells (DMFCs). A Nafion membrane was filled in-situ with proton conductive macromolecules (PCMs) in the swelling process of a Nafion membrane in a PCM solution. As a result, both proton conductivity and methanol-permeation resistivity of the SF-treated Naifion membrane was substantially improved with the selectivity nearly doubled compared to the original Nafion membrane. The mechanical strength of the optimal SF treated Nafion membrane was also enforced due to the strong interaction between the PCM fillers and the Nafion molecular chains. As a result, a DMFC equipped with the SF-treated membrane yielded a 33% higher maximum power density than that offered by the DMFC with the original Nafion membrane.

  9. Origin of Toughness in Dispersion-Cast Nafion Membranes

    DOE PAGES

    Kim, Yu Seung; Welch, Cynthia F.; Hjelm, Rex Paul; ...

    2015-03-23

    In this study, the gelation behavior of Nafion dispersions was investigated using small-angle neutron scattering to better understand the mechanical toughness of dispersion-cast Nafion membranes. Three types of gelation were observed, depending on dispersing fluids: (i) homogeneous, thermally reversible gelation that was present in most aprotic polar dispersing fluids; (ii) inhomogeneous, thermally irreversible gelation as films, found in alcohols; and (iii) inhomogeneous, thermally irreversible gelation which precipitates in water/monohydric alcohol mixtures. The mechanical toughness of dispersion-cast Nafion membranes depends on the dispersing fluid, varying by more than 4 orders of magnitude. Excellent correlation between the critical gelation concentration and mechanicalmore » toughness was demonstrated with the Nafion membranes cast at 140 °C. Additional thermal effects among Nafion membranes cast at 190 °C were qualitatively related to the boiling point of dispersing fluids. Little correlation between mechanical toughness and percent crystalline area of Nafion was observed, suggesting that the origin of mechanical toughness of dispersion-cast Nafion membranes is due to chain entanglements rather than crystallinity. Finally, the correlation between critical gelation concentration and mechanical toughness is a new way of predicting mechanical behavior in dispersion-cast polymer systems in which both polymer-dispersing fluid and polymer–polymer interactions play a significant role in the formation of polymer chain entanglements.« less

  10. Aqua-vanadyl ion interaction with Nafion® membranes

    DOE PAGES

    Vijayakumar, Murugesan; Govind, Niranjan; Li, Bin; ...

    2015-03-23

    Lack of comprehensive understanding about the interactions between Nafion membrane and battery electrolytes prevents the straightforward tailoring of optimal materials for redox flow battery applications. In this work, we analyzed the interaction between aqua-vanadyl cation and sulfonic sites within the pores of Nafion membranes using combined theoretical and experimental X-ray spectroscopic methods. Molecular level interactions, namely, solvent share and contact pair mechanisms are discussed based on Vanadium and Sulfur K-edge spectroscopic analysis.

  11. Structure and Water Transport in Nafion Nanocomposite Membranes

    NASA Astrophysics Data System (ADS)

    Davis, Eric; Page, Kirt

    2014-03-01

    Perfluorinated ionomers, specifically Nafion, are the most widely used ion exchange membranes for vanadium redox flow battery applications, where an understanding of the relationship between membrane structure and transport of water/ions is critical to battery performance. In this study, the structure of Nafion/SiO2 nanocomposite membranes, synthesized using sol-gel chemistry, as well as cast directly from Nafion/SiO2 nanoparticle dispersions, was measured using both small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS). Through contrast match studies of the SiO2 nanoparticles, direct information on the change in the structure of the Nafion membranes and the ion-transport channels within was obtained, where differences in membrane structure was observed between the solution-cast membranes and the membranes synthesized using sol-gel chemistry. Additionally, water sorption and diffusion in these Nafion/SiO2 nanocomposite membranes were measured using in situ time-resolved Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy and dynamic vapor sorption (DVS).

  12. Molecular Modeling of Nafion Permselective Membranes

    DTIC Science & Technology

    2007-11-02

    Nafion type at mesoscale (>20nm); b) understanding of the mechanisms of sorption and transport of chemical agents in swollen PEM. We developed molecular...models for Nafion and nerve agent simulant DMMP and explored microphase segregation and mechanisms of DMMP sorption and transport in hydrated...was developed for DMMP diffusion in hydrated polymer including volume and surface mechanisms . Simulation results correlate with experimental

  13. Nafion/silane nanocomposite membranes for high temperature polymer electrolyte membrane fuel cell.

    PubMed

    Ghi, Lee Jin; Park, Na Ri; Kim, Moon Sung; Rhee, Hee Woo

    2011-07-01

    The polymer electrolyte membrane fuel cell (PEMFC) has been studied actively for both potable and stationary applications because it can offer high power density and be used only hydrogen and oxygen as environment-friendly fuels. Nafion which is widely used has mechanical and chemical stabilities as well as high conductivity. However, there is a drawback that it can be useless at high temperatures (> or = 90 degrees C) because proton conducting mechanism cannot work above 100 degrees C due to dehydration of membrane. Therefore, PEMFC should be operated for long-term at high temperatures continuously. In this study, we developed nanocomposite membrane using stable properties of Nafion and phosphonic acid groups which made proton conducting mechanism without water. 3-Aminopropyl triethoxysilane (APTES) was used to replace sulfonic acid groups of Nafion and then its aminopropyl group was chemically modified to phosphonic acid groups. The nanocomposite membrane showed very high conductivity (approximately 0.02 S/cm at 110 degrees C, <30% RH).

  14. Zirconium oxide nanotube-Nafion composite as high performance membrane for all vanadium redox flow battery

    NASA Astrophysics Data System (ADS)

    Aziz, Md. Abdul; Shanmugam, Sangaraju

    2017-01-01

    A high-performance composite membrane for vanadium redox flow battery (VRB) consisting of ZrO2 nanotubes (ZrNT) and perfluorosulfonic acid (Nafion) was fabricated. The VRB operated with a composite (Nafion-ZrNT) membrane showed the improved ion-selectivity (ratio of proton conductivity to permeability), low self-discharge rate, high discharge capacity and high energy efficiency in comparison with a pristine commercial Nafion-117 membrane. The incorporation of zirconium oxide nanotubes in the Nafion matrix exhibits high proton conductivity (95.2 mS cm-1) and high oxidative stability (99.9%). The Nafion-ZrNT composite membrane exhibited low vanadium ion permeability (3.2 × 10-9 cm2 min-1) and superior ion selectivity (2.95 × 107 S min cm-3). The VRB constructed with a Nafion-ZrNT composite membrane has lower self-discharge rate maintaining an open-circuit voltage of 1.3 V for 330 h relative to a pristine Nafion membrane (29 h). The discharge capacity of Nafion-ZrNT membrane (987 mAh) was 3.5-times higher than Nafion-117 membrane (280 mAh) after 100 charge-discharge cycles. These superior properties resulted in higher coulombic and voltage efficiencies with Nafion-ZrNT membranes compared to VRB with Nafion-117 membrane at a 40 mA cm-2 current density.

  15. Scattering dynamics of oxygen molecules on Nafion membrane

    NASA Astrophysics Data System (ADS)

    Nakauchi, Masataka; Mabuchi, Takuya; Kinefuchi, Ikuya; Takeuchi, Hideki; Tokumasu, Takashi

    2016-11-01

    The scattering behaviors of oxygen molecules on a Nafion membrane, which is a typical polymer electrolyte membrane used in polymer electrolyte fuel cells, have been investigated using molecular dynamics simulations. We have evaluated the probability density functions of the translational energy and scattering angle of the scattered oxygen molecules for a wide range of incident conditions and water contents. It was found that the translational energy of oxygen molecules does not accommodate with the Nafion membrane during the collision, and oxygen molecules are reflected diffusely on the surface. Two types of collision behaviors, i.e., single and multiple collisions, were observed in the simulations. Increasing the normal component of the incident energy and the water content results in the longer residence time on the ionomer surface.

  16. Spray deposition of Nafion membranes: Electrode-supported fuel cells

    NASA Astrophysics Data System (ADS)

    Bayer, Thomas; Pham, Hung Cuong; Sasaki, Kazunari; Lyth, Stephen Matthew

    2016-09-01

    Fuel cells are a key technology for the successful transition towards a hydrogen society. In order to accelerate fuel cell commercialization, improvements in performance are required. Generally, polymer electrolyte membrane fuel cells (PEFCs) are membrane-supported; the electrocatalyst layer is sprayed onto both sides of the membrane, and sandwiched between carbon-based gas diffusion layers (GDLs). In this work we redesign the membrane electrode assembly (MEA) and fabricate an electrode-supported PEFC. First the electrocatalyst layer is sprayed onto the GDL, and then Nafion dispersion is sprayed over the top of this to form a thin membrane. This method has the advantage of simplifying the fabrication process, allowing the fabrication of extremely thin electrolyte layers (down to ∼10 μm in this case), and reducing the amount of ionomer required in the cell. Electrode-supported PEFCs operate at significantly increased power density compared to conventional membrane-supported PEFCs, with a maximum of 581 mW/cm2 at 80 °C (atmospheric pressure, air at the cathode). Impedance spectroscopy confirmed that the origin of the improved performance was an 80% reduction in the membrane resistance due the thinner Nafion layer. This novel fabrication method is a step towards cheaper, thinner, fully printable PEFCs with high power density and efficiency.

  17. Observation of Photovoltaic Action from Photoacid-Modified Nafion Due to Light-Driven Ion Transport.

    PubMed

    White, William; Sanborn, Christopher D; Reiter, Ronald S; Fabian, David M; Ardo, Shane

    2017-08-30

    Replacing passive ion-exchange membranes, like Nafion, with membranes that use light to drive ion transport would allow membranes in photoelectrochemical technologies to serve in an active role. Toward this, we modified perfluorosulfonic acid ionomer membranes with organic pyrenol-based photoacid dyes to sensitize the membranes to visible light and initiate proton transport. Covalent modification of the membranes was achieved by reacting Nafion sulfonyl fluoride poly(perfluorosulfonyl fluoride) membranes with the photoacid 8-hydroxypyrene-1,3,6-tris(2-aminoethylsulfonamide). The modified membranes were strongly colored and maintained a high selectivity for cations over anions. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and ion-exchange measurements together provided strong evidence of covalent bond formation between the photoacids and the polymer membranes. Visible-light illumination of the photoacid-modified membranes resulted in a maximum power-producing ionic photoresponse of ∼100 μA/cm(2) and ∼1 mV under 40 Suns equivalent excitation with 405 nm light. In comparison, membranes that did not contain photoacids and instead contained ionically associated Ru(II)-polypyridyl coordination compound dyes, which are not photoacids, exhibited little-to-no photoeffects (∼1 μA/cm(2)). These disparate photocurrents, yet similar yields for nonradiative excited-state decay from the photoacids and the Ru(II) dyes, suggest temperature gradients were not likely the cause of the observed photovoltaic action from photoacid-modified membranes. Moreover, spectral response measurements supported that light absorption by the covalently bound photoacids was required in order to observe photoeffects. These results represent the first demonstration of photovoltaic action from an ion-exchange membrane and offer promise for supplementing the power demands of electrochemical processes with renewable sunlight-driven ion transport.

  18. Structure and acoustic properties of hydrated nafion membranes.

    PubMed

    Plazanet, M; Bartolini, P; Torre, R; Petrillo, C; Sacchetti, F

    2009-07-30

    The propagation of acoustic waves in water-hydrated Nafion membrane has been monitored using heterodyne-detected transient grating spectroscopy. At room temperature, upon increasing the water content, the speed of sound drops to a value lower than the respective velocities of sound in pure Nafion and pure water. This counterintuitive effect can be explained by a simple calculation of the sound velocity in an effective medium made of water and Nafion polymer. Upon cooling, a phase separation occurs in the sample, and the formation of ice is observed (M. Pineri et al. J. Power Sources 2007, 172, 587-596). This phase transition is characterized via a second acoustic wave observed in the signal. Sound propagation and X-ray diffraction confirm the formation of crystalline ice on the membrane surface, that reversibly melts upon heating. The amount of ice that forms in the sample is monitored as a function of temperature and represents an order parameter for the transition. This parameter follows a power law with an exponent of 0.5, indicating the critical nature of the observed process.

  19. Preparation and performance of nano silica/Nafion composite membrane for proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Wang, Keping; McDermid, Scott; Li, Jing; Kremliakova, Natalia; Kozak, Paul; Song, Chaojie; Tang, Yanghua; Zhang, Jianlu; Zhang, Jiujun

    Composite membranes made from Nafion ionomer with nano phosphonic acid-functionalised silica and colloidal silica were prepared and evaluated for proton exchange membrane fuel cells (PEMFCs) operating at elevated temperature and low relative humidity (RH). The phosphonic acid-functionalised silica additive obtained from a sol-gel process was well incorporated into Nafion membrane. The particle size determined using transmission electron microscope (TEM) had a narrow distribution with an average value of approximately 11 nm and a standard deviation of ±4 nm. The phosphonic acid-functionalised silica additive enhanced proton conductivity and water retention by introducing both acidic groups and porous silica. The proton conductivity of the composite membrane with the acid-functionalised silica was 0.026 S cm -1, 24% higher than that of the unmodified Nafion membrane at 85 °C and 50% RH. Compared with the Nafion membrane, the phosphonic acid-functionalised silica (10% loading level) composite membrane exhibited 60 mV higher fuel cell performance at 1 A cm -2, 95 °C and 35% RH, and 80 mV higher at 0.8 A cm -2, 120 °C and 35% RH. The fuel cell performance of composite membrane made with 6% colloidal silica without acidic group was also higher than unmodified Nafion membrane, however, its performance was lower than the acid-functionalised silica additive composite membrane.

  20. Sulfated Titania-Silica Reinforced Nafion Nanocomposite Membranes for Proton Exchange Membrane Fuel Cells.

    PubMed

    Abu Sayeed, M D; Kim, Hee Jin; Gopalan, A I; Kim, Young Ho; Lee, Kwang-Pill; Choi, Sang-June

    2015-09-01

    Sulfated titania-silica (SO4(2-)-/TiO2-SiO2) composites were prepared by a sol-gel method with sulfate reaction and characterized by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The nanometric diameter and geometry of the sulfated titania-silica (STS) was investigated by transmission electron microscopy (TEM). A small amount of the STS composite in the range of 0.5-3 wt% was then added as reinforcing into the Nafion membrane by water-assisted solution casting method to prepare STS reinforced Nafion nanocomposite membranes (STS-Nafion nanocomposite membranes). The additional functional groups, sulfate groups, of the nanocomposite membrane having more surface oxygenated groups enhanced the fuel cell membrane properties. The STS-Nafion nanocomposite membranes exhibited improved water uptake compared to that of neat Nafion membranes, whereas methanol uptake values were decreased dramatically improved thermal property of the prepared nanocomposite membranes were measured by thermogravimetric analysis (TGA). Furthermore, increased ion exchange capacity values were obtained by thermoacidic pretreatment of the nanocomposite membranes.

  1. Synthesis and characterization of Nafion/TiO2 nanocomposite membrane for proton exchange membrane fuel cell.

    PubMed

    Kim, Tae Young; Cho, Sung Yong

    2011-08-01

    In this study, the syntheses and characterizations of Nafion/TiO2 membranes for a proton exchange membrane fuel cell (PEMFC) were investigated. Porous TiO2 powders were synthesized using the sol-gel method; with Nafion/TiO2 nanocomposite membranes prepared using the casting method. An X-ray diffraction analysis demonstrated that the synthesized TiO2 had an anatase structure. The specific surface areas of the TiO2 and Nafion/TiO2 nanocomposite membrane were found to be 115.97 and 33.91 m2/g using a nitrogen adsorption analyzer. The energy dispersive spectra analysis indicated that the TiO2 particles were uniformly distributed in the nanocomposite membrane. The membrane electrode assembly prepared from the Nafion/TiO2 nanocomposite membrane gave the best PEMFC performance compared to the Nafion/P-25 and Nafion membranes.

  2. Structure of hydrated Na-Nafion polymer membranes.

    PubMed

    Blake, Nick P; Petersen, Matt K; Voth, Gregory A; Metiu, Horia

    2005-12-29

    We use molecular dynamics simulations to investigate the structure of the hydrated Na-Nafion membranes. The membrane is "prepared" by starting with the Nafion chains placed on a cylinder having the water inside it. Minimizing the energy of the system leads to a filamentary hydrophilic domain whose structure depends on the degree of hydration. At 5 wt % water the system does not have enough water molecules to solvate all the ions that could be formed by the dissociation of the -SO3Na groups. As a result, the -SO3Na groups aggregate with the water to form very small droplets that do not join into a continuous phase. The size of the droplets is between 5 and 8 A. As the amount of water present in the membrane is increased, the membrane swells, and SO3Na has an increasing tendency to dissociate into ions. Furthermore, a transition to a percolating hydrophilic network is observed. In the percolating structure, the water forms irregular curvilinear channels branching in all directions. The typical dimension of the cross section of these channels is about 10-20 A. Calculated neutron scattering from the simulated system is in qualitative agreement with experiment. In all simulations, the pendant sulfonated perfluorovinyl side chains of the Nafion hug the walls of the hydrophilic channel, while the sulfonate groups point toward the center of the hydrophilic phase. The expulsion of the side chains from the hydrophilic domain is favored because it allows better interaction between the water molecules. We have also examined the probability of finding water molecules around the Na+ and the -SO3(-) ions as well as the probability of finding other water molecules next to a given water molecule. These probabilities are much broader than those found in bulk water or for one ion in bulk water (calculated with the potentials used in the present simulation). This is due to the highly inhomogeneous nature of the material contained in the small hydrophilic pores.

  3. Proton conductive montmorillonite-Nafion composite membranes for direct ethanol fuel cells

    NASA Astrophysics Data System (ADS)

    Wu, Xiu-Wen; Wu, Nan; Shi, Chun-Qing; Zheng, Zhi-Yuan; Qi, Hong-Bin; Wang, Ya-Fang

    2016-12-01

    The preparation of Nafion membranes modified with montmorillonites is less studied, and most relative works mainly applied in direct methanol fuel cells, less in direct ethanol fuel cells. Organic/inorganic composite membranes are prepared with different montmorillonites (Ca-montmorillonite, Na-montmorillonite, K-montmorillonite, Mg-montmorillonite, and H-montmorillonite) and Nafion solution via casting method at 293 K in air, and with balance of their proton conductivity and ethanol permeability. The ethanol permeability and proton conductivity of the membranes are comparatively studied. The montmorillonites can well decrease the ethanol permeability of the membranes via inserted them in the membranes, while less decrease the proton conductivities of the membranes depending on the inserted amount and type of montmorillonites. The proton conductivities of the membranes are between 36.0 mS/cm and 38.5 mS/cm. The ethanol permeability of the membranes is between 0.69 × 10-6 cm2/s and 2.67 × 10-6 cm2/s.

  4. Sulfonated graphene oxide/nafion composite membrane for vanadium redox flow battery.

    PubMed

    Kim, Byung Guk; Han, Tae Hee; Cho, Chang Gi

    2014-12-01

    Nafion is the most frequently used as the membrane material due to its good proton conductivity, and excellent chemical and mechanical stabilities. But it is known to have poor barrier property due to its well-developed water channels. In order to overcome this drawback, graphene oxide (GO) derivatives were introduced for Nafion composite membranes. Sulfonated graphene oxide (sGO) was prepared from GO. Both sGO and GO were treated each with phenyl isocyanate and transformed into corresponding isGO and iGO in order to promote miscibility with Nafion. Then composite membranes were obtained, and the adaptability as a membrane for vanadium redox flow battery (VRFB) was investigated in terms of proton conductivity and vanadium permeability. Compared to a pristine Nafion, proton conductivities of both isGO/Nafion and iGO/Nafion membranes showed less temperature sensitivity. Both membranes also showed quite lower vanadium permeability at room temperature. Selectivity of the membrane was the highest for isGO/Nafion and the lowest for the pristine Nafion.

  5. Nafion-Initiated ATRP of 1-Vinylimidazole for Preparation of Proton Exchange Membranes.

    PubMed

    Feng, Kai; Liu, Lei; Tang, Beibei; Li, Nanwen; Wu, Peiyi

    2016-05-11

    Nafion is one of the most widely investigated materials applied in proton exchange membranes. Interestingly, it was found that Nafion could serve as a macroinitiator to induce atom transfer radical polymerization (ATRP) on its C-F sites. In this study, poly(1-vinylimidazole) was selectively bonded on the side chains of Nafion via the Nafion-initiated ATRP process, which was confirmed by the measurements of (1)H/(19)F nuclear magnetic resonance spectra, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, differential scanning calorimeter and matrix-assisted laser desorption ionization-time-of-flight/time-of-flight mass spectrometry. The as-prepared Nafion-co-poly(1-vinylimidazole) (Nafion-PVIm) membranes, with tunable loading amount of imidazole rings, presented greatly enhanced proton conductivity and methanol resistivity due to their well-controlled chemical structures. Especially, chemically bonding PVIm with Nafion chains endowed the Nafion-PVIm membranes with high stability in proton conductivity. For the first time, we revealed the great potentials of the Nafion-initiated ATRP process in developing high-performance proton exchange membranes.

  6. Modification of Nafion membrane with biofunctional SiO2 nanofiber for proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Wang, Hang; Li, Xiaojie; Zhuang, Xupin; Cheng, Bowen; Wang, Wei; Kang, Weimin; Shi, Lei; Li, Hongjun

    2017-02-01

    Proton currents are an integral part of the most important energy-converting structures in biology. We prepared a new type of bioinspired Nafion (Bio-Nafion) membrane composited of biofunctional SiO2 (Bio-SiO2) nanofiber and Nafion matrix. SiO2 nanofibers were prepared by electrospinning silica sol prepared from tetraethyl orthosilicate. Meanwhile, Bio-SiO2 nanofibers were synthesized by immobilizing amino acids (cysteine, serine, lysine, and glycine) on SiO2 nanofibers, which acted as efficient proton-conducting pathways that involved numerous H+ transport sites. In our study, the SiO2 nanofibers biofunctionalized with cysteine were further oxidized, and the composite membranes were designated as Nafion-Cys, Nafion-Lys, Nafion-Ser, and Nafion-Gly, respectively. We then investigated the different polar groups (sbnd SO3H, sbnd OH, and sbnd NH2) of the amino acids that contributed to membrane properties of thermal stability, water uptake (WU), dimensional stability, proton conductivity, and methanol permeability. Nafion-Cys exhibited the highest proton conductivity of 0.2424 S/cm (80 °C). Nafion-Gly showed the lowest proton conductivity and WU because glycine contains the least number of hydrophilic groups among the amino acids. Overall, the introduction of Bio-SiO2 nanofiber to composite membranes significantly improved proton conductivity, dimensional stability, and methanol permeability.

  7. Spectroscopic Investigations of the Fouling Process on Nafion Membranes in Vanadium Redox Flow Batteries

    SciTech Connect

    Vijayakumar, M.; Sivakumar, Bhuvaneswari M.; Nachimuthu, Ponnusamy; Schwenzer, Birgit; Kim, Soowhan; Yang, Zhenguo; Liu, Jun; Graff, Gordon L.; Thevuthasan, Suntharampillai; Hu, Jian Z.

    2011-01-01

    The Nafion-117 membrane used in vanadium redox flow battery (VRFB) is analyzed by X-ray photoelectron spectroscopy (XPS) and nuclear magnetic resonance (NMR) spectroscopy. The XPS study reveals the chemical identity and environment of vanadium cations accumulated at the surface due to their low diffusivity. On the other hand, the 17O NMR spectrum explores the diffused vanadium cation from the bulk part of Nafion and shows the chemical bonding of cation and the host membrane. The 19F NMR shows the basic Nafion structure is not altered due to the presence of diffused vanadium cation. Based on these spectroscopic studies, the chemical environment of diffused vanadium cation in the Nafion membrane is discussed. This study also shed light into the possible cause for the high diffusivity of certain vanadium cations inside the Nafion membranes.

  8. Insights into the Impact of the Nafion Membrane Pretreatment Process on Vanadium Flow Battery Performance.

    PubMed

    Jiang, Bo; Yu, Lihong; Wu, Lantao; Mu, Di; Liu, Le; Xi, Jingyu; Qiu, Xinping

    2016-05-18

    Nafion membranes are now the most widely used membranes for long-life vanadium flow batteries (VFBs) because of their extremely high chemical stability. Today, the type of Nafion membrane that should be selected and how to pretreat these Nafion membranes have become critical issues, which directly affects the performance and cost of VFBs. In this work, we chose the Nafion 115 membrane to investigate the effect of the pretreatment process (as received, wet, boiled, and boiled and dried) on the performance of VFBs. The relationship between the nanostructure and transport properties of Nafion 115 membranes is elucidated by wide-angle X-ray diffraction and small-angle X-ray scattering techniques. The self-discharge process, battery efficiencies, electrolyte utilization, and long-term cycling stability of VFBs with differently pretreated Nafion membranes are presented comprehensively. An online monitoring system is used to monitor the electrolyte volume that varies during the long-term charge-discharge test of VFBs. The capacity fading mechanism and electrolyte imbalance of VFBs with these Nafion 115 membranes are also discussed in detail. The optimal pretreatment processes for the benchmark membrane and practical application are synthetically selected.

  9. RADIATION STABILITY OF NAFION MEMBRANES USED FOR ISOTOPE SEPARATION BY PROTON EXCHANGE MEMBRANE ELECTROLYSIS

    SciTech Connect

    Fox, E

    2009-05-15

    Proton Exchange Membrane Electrolyzers have potential interest for use for hydrogen isotope separation from water. In order for PEME to be fully utilized, more information is needed on the stability of Nafion when exposed to radiation. This work examines Nafion 117 under varying exposure conditions, including dose rate, total dosage and atmospheric condition. Analytical tools, such as FT-IR, ion exchange capacity, DMA and TIC-TOC were used to characterize the exposed membranes. Analysis of the water from saturated membranes can provide important data on the stability of the membranes during radiation exposure. It was found that the dose rate of exposure plays an important role in membrane degradation. Potential mechanisms for membrane degradation include peroxide formation by free radicals.

  10. Vibrational and structural relaxation of hydrated protons in Nafion membranes

    NASA Astrophysics Data System (ADS)

    Liu, Liyuan; Lotze, Stephan; Bakker, Huib J.

    2017-02-01

    We study the vibrational dynamics of the bending mode at 1730 cm-1 of proton hydration structures in Nafion membranes with polarization-resolved infrared (IR) pump-probe spectroscopy. The bending mode relaxes to an intermediate state with a time constant T1 of 170 ± 30 fs. Subsequently, the dissipated energy equilibrates with Teq of 1.5 ± 0.2 ps. The transient absorption signals show a long-living anisotropy, which indicates that for part of the excited proton hydration clusters the vibrational energy dissipation results in a local structural change, e.g. the breaking of a local hydrogen bond. This structural relaxation relaxes with a time constant of 38 ± 4 ps.

  11. Performance of composite Nafion/PVA membranes for direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Mollá, Sergio; Compañ, Vicente

    2011-03-01

    This work has been focused on the characterization of the methanol permeability and fuel cell performance of composite Nafion/PVA membranes in function of their thickness, which ranged from 19 to 97 μm. The composite membranes were made up of Nafion® polymer deposited between polyvinyl alcohol (PVA) nanofibers. The resistance to methanol permeation of the Nafion/PVA membranes shows a linear variation with the thickness. The separation between apparent and true permeability permits to give an estimated value of 4.0 × 10-7 cm2 s-1 for the intrinsic or true permeability of the bulk phase at the composite membranes. The incorporation of PVA nanofibers causes a remarkable reduction of one order of magnitude in the methanol permeability as compared with pristine Nafion® membranes. The DMFC performances of membrane-electrode assemblies prepared from Nafion/PVA and pristine Nafion® membranes were tested at 45, 70 and 95 °C under various methanol concentrations, i.e., 1, 2 and 3 M. The nanocomposite membranes with thicknesses of 19 μm and 47 μm reached power densities of 211 mW cm-2 and 184 mW cm-2 at 95 °C and 2 M methanol concentration. These results are comparable to those found for Nafion® membranes with similar thickness at the same conditions, which were 210 mW cm-2 and 204 mW cm-2 respectively. Due to the lower amount of Nafion® polymer present within the composite membranes, it is suggested a high degree of utilization of Nafion® as proton conductive material within the Nafion/PVA membranes, and therefore, significant savings in the consumed amount of Nafion® are potentially able to be achieved. In addition, the reinforcement effect caused by the PVA nanofibers offers the possibility of preparing membranes with very low thickness and good mechanical properties, while on the other hand, pristine Nafion® membranes are unpractical below a thickness of 50 μm.

  12. Energy Conversion from Salinity Gradient Using Microchip with Nafion Membrane

    NASA Astrophysics Data System (ADS)

    Chang, Che-Rong; Yeh, Ching-Hua; Yeh, Hung-Chun; Yang, Ruey-Jen

    2016-06-01

    When a concentrated salt solution and a diluted salt solution are separated by an ion-selective membrane, cations and anions would diffuse at different rates depending on the ion selectivity of the membrane. The difference of positive and negative charges at both ends of the membrane would produce a potential, called the diffusion potential. Thus, electrical energy can be converted from the diffusion potential through reverse electrodialysis. This study demonstrated the fabrication of an energy conversion microchip using the standard micro-electromechanical technique, and utilizing Nafion junction as connecting membrane, which was fabricated by a surface patterned process. Through different salinity gradient of potassium chloride solutions, we experimentally investigated the diffusion potential and power generation from the microchip, and the highest value measured was 135 mV and 339 pW, respectively. Furthermore, when the electrolyte was in pH value of 3.8, 5.6, 10.3, the system exhibited best performance at pH value of 10.3; whereas, pH value of 3.8 yielded the worst.

  13. Prism-patterned Nafion membrane for enhanced water transport in polymer electrolyte membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Kim, Sang Moon; Kang, Yun Sik; Ahn, Chiyeong; Jang, Segeun; Kim, Minhyoung; Sung, Yung-Eun; Yoo, Sung Jong; Choi, Mansoo

    2016-06-01

    Here, we report a simple and effective strategy to enhance the performance of the polymer electrolyte membrane fuel cell by imprinting prism-patterned arrays onto the Nafion membrane, which provides three combined effects directly related to the device performance. First, a locally thinned membrane via imprinted micro prism-structures lead to reduced membrane resistance, which is confirmed by electrochemical impedance spectroscopy. Second, increments of the geometrical surface area of the prism-patterned Nafion membrane compared to a flat membrane result in the increase in the electrochemical active surface area. Third, the vertically asymmetric geometry of prism structures in the cathode catalyst layer lead to enhanced water transport, which is confirmed by oxygen gain calculation. To explain the enhanced water transport, we propose a simple theoretical model on removal of water droplets existing in the asymmetric catalyst layer. These three combined effects achieved via incorporating prism patterned arrays into the Nafion membrane effectively enhance the performance of the polymer electrolyte membrane fuel cell.

  14. Electrospun Nafion®/Polyphenylsulfone composite membranes for regenerative Hydrogen bromine fuel cells

    DOE PAGES

    Park, Jun; Wycisk, Ryszard; Pintauro, Peter N.; ...

    2016-02-29

    Here, the regenerative H2/Br2-HBr fuel cell, utilizing an oxidant solution of Br2 in aqueous HBr, shows a number of benefits for grid-scale electricity storage. The membrane-electrode assembly, a key component of a fuel cell, contains a proton-conducting membrane, typically based on the perfluorosulfonic acid (PFSA) ionomer. Unfortunately, the high cost of PFSA membranes and their relatively high bromine crossover are serious drawbacks. Nanofiber composite membranes can overcome these limitations. In this work, composite membranes were prepared from electrospun dual-fiber mats containing Nafion® PFSA ionomer for facile proton transport and an uncharged polymer, polyphenylsulfone (PPSU), for mechanical reinforcement, and swelling control.more » After electrospinning, Nafion/PPSU mats were converted into composite membranes by softening the PPSU fibers, through exposure to chloroform vapor, thus filling the voids between ionomer nanofibers. It was demonstrated that the relative membrane selectivity, referenced to Nafion® 115, increased with increasing PPSU content, e.g., a selectivity of 11 at 25 vol% of Nafion fibers. H2-Br2 fuel cell power output with a 65 m thick membrane containing 55 vol% Nafion fibers was somewhat better than that of a 150 m Nafion® 115 reference, but its cost advantage due to a four-fold decrease in PFSA content and a lower bromine species crossover make it an attractive candidate for use in H2/Br2-HBr systems.« less

  15. Slow solvation dynamics in the microheterogeneous water channels of nafion membranes.

    PubMed

    Burai, Tarak Nath; Datta, Anindya

    2009-12-10

    Solvation dynamics in Nafion membrane is studied using the well-known solvation probe, coumarin 102 (C102). In native Nafion membrane, the fluorescence maximum of C102 occurs at 525 nm. The decays recorded at different wavelengths are superimposable. There is no time-dependent Stokes shift (TDSS) in the time scale of the experiment. This is rationalized in light of the strongly acidic environment in Nafion membrane, which causes the C102 molecules to become protonated. The protonated molecules are bound tightly to the negatively charged sulfonate groups. In Na(+)- and Me(4)N(+)-exchanged Nafion membranes, the fluorescence gets blue-shifted by 65 nm, indicating the deprotonation of the cation and formation of neutral C102 in these membranes. TDSS is observed in the picosecond-nanosecond time scale, in the cation-exchanged Nafion membranes, although the amount of Stokes' shift is rather small, as compared to that observed in organic solvents, indicating that a significant amount of the solvation is ultrafast and is missed in the present experiment. The observed solvation dynamics is bimodal with fast ( approximately 1 ns) and slow (>10 ns) components. The ultraslow component is ascribed to the quasi-static water molecules in the Nafion membrane. The difference in the extents of apparently missing ultrafast components, between Me(4)N(+)- and Na(+)-substituted membranes is rationalized by a model involving the difference in distributions of the cations in the water channel.

  16. Electrospun Nafion(®)/Polyphenylsulfone Composite Membranes for Regenerative Hydrogen Bromine Fuel Cells.

    PubMed

    Park, Jun Woo; Wycisk, Ryszard; Pintauro, Peter N; Yarlagadda, Venkata; Van Nguyen, Trung

    2016-02-29

    The regenerative H₂/Br₂-HBr fuel cell, utilizing an oxidant solution of Br₂ in aqueous HBr, shows a number of benefits for grid-scale electricity storage. The membrane-electrode assembly, a key component of a fuel cell, contains a proton-conducting membrane, typically based on the perfluorosulfonic acid (PFSA) ionomer. Unfortunately, the high cost of PFSA membranes and their relatively high bromine crossover are serious drawbacks. Nanofiber composite membranes can overcome these limitations. In this work, composite membranes were prepared from electrospun dual-fiber mats containing Nafion(®) PFSA ionomer for facile proton transport and an uncharged polymer, polyphenylsulfone (PPSU), for mechanical reinforcement, and swelling control. After electrospinning, Nafion/PPSU mats were converted into composite membranes by softening the PPSU fibers, through exposure to chloroform vapor, thus filling the voids between ionomer nanofibers. It was demonstrated that the relative membrane selectivity, referenced to Nafion(®) 115, increased with increasing PPSU content, e.g., a selectivity of 11 at 25 vol% of Nafion fibers. H₂-Br₂ fuel cell power output with a 65 μm thick membrane containing 55 vol% Nafion fibers was somewhat better than that of a 150 μm Nafion(®) 115 reference, but its cost advantage due to a four-fold decrease in PFSA content and a lower bromine species crossover make it an attractive candidate for use in H₂/Br₂-HBr systems.

  17. Electrospun Nafion®/Polyphenylsulfone Composite Membranes for Regenerative Hydrogen Bromine Fuel Cells

    PubMed Central

    Park, Jun Woo; Wycisk, Ryszard; Pintauro, Peter N.; Yarlagadda, Venkata; Van Nguyen, Trung

    2016-01-01

    The regenerative H2/Br2-HBr fuel cell, utilizing an oxidant solution of Br2 in aqueous HBr, shows a number of benefits for grid-scale electricity storage. The membrane-electrode assembly, a key component of a fuel cell, contains a proton-conducting membrane, typically based on the perfluorosulfonic acid (PFSA) ionomer. Unfortunately, the high cost of PFSA membranes and their relatively high bromine crossover are serious drawbacks. Nanofiber composite membranes can overcome these limitations. In this work, composite membranes were prepared from electrospun dual-fiber mats containing Nafion® PFSA ionomer for facile proton transport and an uncharged polymer, polyphenylsulfone (PPSU), for mechanical reinforcement, and swelling control. After electrospinning, Nafion/PPSU mats were converted into composite membranes by softening the PPSU fibers, through exposure to chloroform vapor, thus filling the voids between ionomer nanofibers. It was demonstrated that the relative membrane selectivity, referenced to Nafion® 115, increased with increasing PPSU content, e.g., a selectivity of 11 at 25 vol% of Nafion fibers. H2-Br2 fuel cell power output with a 65 μm thick membrane containing 55 vol% Nafion fibers was somewhat better than that of a 150 μm Nafion® 115 reference, but its cost advantage due to a four-fold decrease in PFSA content and a lower bromine species crossover make it an attractive candidate for use in H2/Br2-HBr systems. PMID:28773268

  18. Influence of aminosilane precursor concentration on physicochemical properties of composite Nafion membranes for vanadium redox flow battery applications

    NASA Astrophysics Data System (ADS)

    Kondratenko, Mikhail S.; Karpushkin, Evgeny A.; Gvozdik, Nataliya A.; Gallyamov, Marat O.; Stevenson, Keith J.; Sergeyev, Vladimir G.

    2017-02-01

    A series of composite proton-exchange membranes have been prepared via sol-gel modification of commercial Nafion membranes with [N-(2-aminoethyl)-3-aminopropyl]trimethoxysilane. The structure and physico-chemical properties (water uptake, ion-exchange capacity, vanadyl ion permeability, and proton conductivity) of the prepared composite membranes have been studied as a function of the precursor loading (degree of the membrane modification). If the amount of the precursor is below 0.4/1 M ratio of the amino groups of the precursor to the sulfonic groups of Nafion, the composite membranes exhibit decreased vanadium ion permeability while having relatively high proton conductivity. With respect to the use of a non-modified Nafion membrane, the performance of the composite membrane with an optimum precursor loading in a single-cell vanadium redox flow battery demonstrates enhanced energy efficiency in 20-80 mA cm-2 current density range. The maximum efficiency increase of 8% is observed at low current densities.

  19. Graphene-based nafion nanocomposite membranes: enhanced proton transport and water retention by novel organo-functionalized graphene oxide nanosheets.

    PubMed

    Enotiadis, Apostolos; Angjeli, Kristina; Baldino, Noemi; Nicotera, Isabella; Gournis, Dimitrios

    2012-11-05

    Novel nanostructured organo-modified layered materials based on graphene oxide carrying various hydrophilic functional groups (-NH(2), -OH, -SO(3)H) are prepared and tested as nanofillers for the creation of innovative graphene-based Nafion nanocomposites. The hybrid membranes are characterized by a combination of analytical techniques, which show that highly homogeneous exfoliated nanocomposites are created. The pulsed field gradient NMR technique is used to measure the water self-diffusion coefficients. Remarkable behavior at temperatures up to 140 °C is observed for some composite membranes, thereby verifying the exceptional water retention property of these materials. Dynamic mechanical analysis shows that hybrid membranes are much stiffer and can withstand higher temperatures than pure Nafion.

  20. Nafion-porous cerium oxide nanotubes composite membrane for polymer electrolyte fuel cells operated under dry conditions

    NASA Astrophysics Data System (ADS)

    Ketpang, Kriangsak; Oh, Kwangjin; Lim, Sung-Chul; Shanmugam, Sangaraju

    2016-10-01

    A composite membrane operated in polymer electrolyte fuel cells (PEFCs) under low relative humidity (RH) is developed by incorporating cerium oxide nanotubes (CeNT) into a perfluorosulfonic acid (Nafion®) membrane. Porous CeNT is synthesized by direct heating a precursor impregnated polymer fibers at 500 °C under an air atmosphere. Compared to recast Nafion and commercial Nafion (NRE-212) membranes, the Nafion-CeNT composite membrane generates 1.1 times higher power density at 0.6 V, operated at 80 °C under 100% RH. Compared to Nafion-cerium oxide nanoparticles (Nafion-CeNP) membrane, the Nafion-CeNT provides 1.2 and 1.7 times higher PEFC performance at 0.6 V when operated at 80 °C under 100% and 18% RH, respectively. Additionally, the Nafion-CeNT composite membrane exhibits a good fuel cell operation under 18% RH at 80 °C. Specifically, the fluoride emission rate of Nafion-CeNT composite membrane is 20 times lower than that of the commercial NRE-212 membrane when operated under 18% RH at 80 °C for 96 h. The outstanding PEFC performance and durability operated under dry conditions is mainly attributed to the facile water diffusion capability as well as the effective hydroxyl radical scavenging property of the CeNT filler, resulting in significantly mitigating both the ohmic resistance and Nafion membrane degradation.

  1. Water vapor sorption thermodynamics of the Nafion ionomer membrane.

    PubMed

    Wadsö, Lars; Jannasch, Patric

    2013-07-18

    The water interactions of polymer electrolyte membranes are of significant interest when these materials are used in, for example, fuel cells. We have therefore studied the sorption thermodynamics of Nafion with a sorption calorimeter that simultaneously measures the sorption isotherm and the mixing (sorption) enthalpy. This unique method is suitable for investigating the sorption thermodynamics of ionic polymers. The measurements were made at 25 °C on a series of samples dried at different temperatures from 25 to 120 °C. The sorption isotherms indicate that the samples dried at 120 °C lost about 0.8 more water molecules per sulfonic group during the drying than did the samples dried at 25 °C, and this result was verified gravimetrically. The mixing enthalpies showed several peaks or plateaus for the samples dried at 60-120 °C. This behavior was seen up to about 2 water molecules per sulfonic group. As these peaks were not directly related to any feature in the sorption isotherm, they probably have their origin in a secondary process, such as a reorganization of the polymer.

  2. Proton conductivity and methanol permeability of Nafion-SiO2/SiWA composite membranes

    NASA Astrophysics Data System (ADS)

    Thiam, Hui San; Chia, Min Yan; Cheah, Qiao Rou; Koo, Charlene Chai Hoon; Lai, Soon Onn; Chong, Kok Chung

    2017-04-01

    Proton exchange membranes for a direct methanol fuel cell (DMFC) were prepared by incorporating silica/silicotungstic acid (SiO2/SiWA) inorganic composite into a Nafion polymer. The effects of SiO2/SiWA content on proton conductivity of membranes were investigated by using a four-probe conductivity cell. Methanol permeability of composite membrane was also determined by using a homemade diffusion cell and gas chromatography technique. It was found that proton conductivity of the composite membranes decreased with SiO2/SiWA content, however the highest proton conductivity achieved was 11% greater than the pure recast Nafion membrane. The methanol permeability of composite membrane was much lower than that of pure recast Nafion, in a reduction of 58% which indicated a better resistance to fuel crossover. Nafion-SiO2/SiWA composite membrane showed promising advantages over pure Nafion on electrochemical properties such as proton conductivity and fuel crossover and it is potentially attractive for use in DMFC.

  3. Nafion®/ODF-silica composite membranes for medium temperature proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Treekamol, Yaowapa; Schieda, Mauricio; Robitaille, Lucie; MacKinnon, Sean M.; Mokrini, Asmae; Shi, Zhiqing; Holdcroft, Steven; Schulte, Karl; Nunes, Suzana P.

    2014-01-01

    A series of composite membranes were prepared by dispersing fluorinated polyoxadiazole oligomer (ODF)-functionalized silica nanoparticles in a Nafion® matrix. Both melt-extrusion and solvent casting processes were explored. Ion exchange capacity, conductivity, water uptake and dimensional stability, thermal stability and morphology were characterized. The inclusion of functionalized nanoparticles proved advantageous, mainly due to a physical crosslinking effect and better water retention, with functionalized nanoparticles performing better than the pristine silica particles. For the same filler loading, better nanoparticle dispersion was achieved for solvent-cast membranes, resulting in higher proton conductivity. Filler agglomeration, however, was more severe for solvent-cast membranes at loadings beyond 5 wt.%. The composite membranes showed excellent thermal stability, allowing for operation in medium temperature PEM fuel cells. Fuel cell performance of the composite membranes decreases with decreasing relative humidity, but good performance values are still obtained at 34% RH and 90 °C, with the best results obtained for solvent cast membranes loaded with 10 wt.% ODF-functionalized silica. Hydrogen crossover of the composite membranes is higher than that for pure Nafion® membranes, possibly due to porosity resulting from suboptimal particle-matrix compatibility.

  4. Mechanical properties and XRD of Nafion modified by 2-hydroxyethylammonium ionic liquids

    NASA Astrophysics Data System (ADS)

    Garaev, V.; Pavlovica, S.; Reinholds, I.; Vaivars, G.

    2013-12-01

    In this work, the Nafion 112 membrane impregnated with 2-hydroxyethylammonium carboxylate ionic liquids have been investigated. The used ionic liquids were 2-hydroxyethylammonium formate [HEA]F, acetate [HEA]A and lactate [HEA]L. Prepared composite membranes Nafion/ionic liquid are characterized by mechanical testing, such as tensile test and creep test. It is found that ionic liquids decrease elastic modulus and creep compliance, but do not have significant effect on the tensile strength. Also, composite membranes were studied by wide angle X-ray diffraction. All ionic liquids shift the peak maximum to the lower angle. In this work, only biodegradable ionic liquids were used for composite preparation.

  5. A sensitive determination of dopamine in the presence of ascorbic acid using a nafion-coated clinoptilolite-modified carbon paste electrode.

    PubMed

    Alpat, Senol; Alpat, Sibel Kilinc; Telefoncu, Azmi

    2005-10-01

    A selective dopamine determination using a nafion-coated clinoptilolite-modified carbon paste electrode in the presence of ascorbic acid was studied. Both cyclic voltammetry (CV) and differential pulse anodic stripping voltammetry (DPASV) were used for measurements of dopamine. To improve the selectivity of the clinoptilolite-modified carbon paste electrode in presence of a high concentration of ascorbic acid, the electrode surface was coated with nafion membrane. Experimental parameters affecting the determination of dopamine, including the clinoptilolite ratio, nafion membrane thickness, preconcentration time, preconcentration solution pH, stripping solution pH and interferences are discussed. The developed sensor has a wide linear range, a low detection limit, and good stability and reproducibility. The sensor offers a good alternative to existing analytical methods for dopamine, permits a relatively short analysis time, and is simple, selective and inexpensive.

  6. Electrospun Nafion®/Polyphenylsulfone composite membranes for regenerative Hydrogen bromine fuel cells

    SciTech Connect

    Park, Jun; Wycisk, Ryszard; Pintauro, Peter N.; Yarlagadda, Venkata; Van Nguyen, Trung

    2016-02-29

    Here, the regenerative H2/Br2-HBr fuel cell, utilizing an oxidant solution of Br2 in aqueous HBr, shows a number of benefits for grid-scale electricity storage. The membrane-electrode assembly, a key component of a fuel cell, contains a proton-conducting membrane, typically based on the perfluorosulfonic acid (PFSA) ionomer. Unfortunately, the high cost of PFSA membranes and their relatively high bromine crossover are serious drawbacks. Nanofiber composite membranes can overcome these limitations. In this work, composite membranes were prepared from electrospun dual-fiber mats containing Nafion® PFSA ionomer for facile proton transport and an uncharged polymer, polyphenylsulfone (PPSU), for mechanical reinforcement, and swelling control. After electrospinning, Nafion/PPSU mats were converted into composite membranes by softening the PPSU fibers, through exposure to chloroform vapor, thus filling the voids between ionomer nanofibers. It was demonstrated that the relative membrane selectivity, referenced to Nafion® 115, increased with increasing PPSU content, e.g., a selectivity of 11 at 25 vol% of Nafion fibers. H2-Br2 fuel cell power output with a 65 m thick membrane containing 55 vol% Nafion fibers was somewhat better than that of a 150 m Nafion® 115 reference, but its cost advantage due to a four-fold decrease in PFSA content and a lower bromine species crossover make it an attractive candidate for use in H2/Br2-HBr systems.

  7. Bi-modal water transport behavior across a simple Nafion membrane

    NASA Astrophysics Data System (ADS)

    Zhang, Ziheng; Promislow, Keith; Martin, Jonathan; Wang, Haijiang; Balcom, Bruce J.

    2011-10-01

    The development of predictive mathematical models for water management in polymer electrolyte membrane fuel cells requires detailed understanding of water distribution and water transport across the Nafion layer. The anisotropic microstructure of Nafion suggests the measurement of water content and mass transport should be along the fuel cell functional direction, i.e. across the membrane. Non-invasive, high resolution, microscopy measurements of this type are very challenging. We report here the calibration of a minimal mathematical model for diffusive water transport in Nafion against data from high-resolution water content maps determined with a new magnetic resonance imaging methodology developed for this purpose. A mock fuel cell was designed to permit well-controlled wetting and drying boundary conditions. With no chemical potential driving force involved, we assume the water transport behavior will be dominated by diffusion. Moreover we show that, in this context, our model is mathematically equivalent to the traditional permeation models based upon saturation dependent pressure gradients via a capillary pressure ansatz. The non-linear equilibrium water distribution across the Nafion membrane measured in this work suggests a bi-modal diffusivity. The model constructed associates distinct transport behaviors to water contents above and below a critical threshold, consistent with a rearrangement of a micro-structural pore network. The experimental observation and the model prediction agree with the primary features of Weber's model of Nafion, which predicts distinct modes of transport for hydration fronts traversing the through-plane direction of the membrane.

  8. Atomistic Simulations of Perfluoro Phosphonic and Phosphinic Acid Membranes and Comparisons to Nafion

    SciTech Connect

    Idupulapati, Nagesh B.; Devanathan, Ramaswami; Dupuis, Michel

    2011-03-31

    We used classical molecular dynamics (MD) simulations to investigate the nanoscale morphology and proton transport properties of perfluoro phosphonic (FPA) and phosphinic acid (FPA-I) membranes as they are being considered for use in low temperature fuel cells. We systematically investigated these properties as a function of the hydration level. The changes in nanostructure, in transport dynamics of water and hydronium ions, and in water network percolation were extracted from MD simulations and compared with Nafion. Phosphonic and phosphinic acid moieties in FPA and FPA-I, have lower acidity than sulfonic acid in Nafion, yet the diffusion of water was observed to be faster in FPA and FPA-I than in Nafion, particularly at low hydration levels. However this did not give rise to notable differences in hydronium ion diffusion and water network percolation for these membranes over Nafion. Similar observations were also reported by our group recently in a study of perfluoro-sulfonyl imide membranes carrying stronger super-acids than sulfonic acid of Nafion. These findings together suggest no strong apparent correlation between the acidity strength of the functional acid groups and the dynamics of water and hydronium ions in hydrated polymer electrolyte membranes (PEMs) with similar fluorocarbon backbones and acidic group-carrying side chains. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  9. Composite Nafion 117-TMSP membrane for Fe-Cr redox flow battery applications

    NASA Astrophysics Data System (ADS)

    Haryadi, Gunawan, Y. B.; Mursid, S. P.; Harjogi, D.

    2016-04-01

    The modification of Nafion 117 - TMSP (trimethoxysylilprophanthiol) composite membrane has been conducted by in-situ sol-gel method followed by characterization of structural and properties of material using spectroscopic techniques. The performance of composite membrane has then been examined in the single stack module of Fe-Cr Redox Flow Battery. It was found that the introduction of silica from TMSP through sol-gel process within the Nafion 117 membrane produced composite membrane that has slightly higher proton conductivity values as compared to the pristine of Nafion 117 membrane observed by electrochemical impedance spectroscopy. The degree of swelling of water in the composite membrane demonstrated greatly reduced than a pristine Nafion 117 signifying low water cross over. The SEM-EDX measurements indicated that there was no phase separation occurred suggesting that silica nanoparticles are distributed homogeneously within the composite membrane. The composite membrane used as separator in the system of Fe-Cr Redox Flow Battery revealed no cross mixing (crossover) occurred between anolyte and catholyte in the system as observed from the total voltage measurements that closed to the theoretical value. The battery efficiency generally increased as the volume of the electrolytes enlarged.

  10. Composite Nafion 117-TMSP membrane for Fe-Cr redox flow battery applications

    SciTech Connect

    Haryadi; Gunawan, Y. B.; Harjogi, D.; Mursid, S. P.

    2016-04-19

    The modification of Nafion 117 - TMSP (trimethoxysylilprophanthiol) composite membrane has been conducted by in-situ sol-gel method followed by characterization of structural and properties of material using spectroscopic techniques. The performance of composite membrane has then been examined in the single stack module of Fe-Cr Redox Flow Battery. It was found that the introduction of silica from TMSP through sol-gel process within the Nafion 117 membrane produced composite membrane that has slightly higher proton conductivity values as compared to the pristine of Nafion 117 membrane observed by electrochemical impedance spectroscopy. The degree of swelling of water in the composite membrane demonstrated greatly reduced than a pristine Nafion 117 signifying low water cross over. The SEM-EDX measurements indicated that there was no phase separation occurred suggesting that silica nanoparticles are distributed homogeneously within the composite membrane. The composite membrane used as separator in the system of Fe-Cr Redox Flow Battery revealed no cross mixing (crossover) occurred between anolyte and catholyte in the system as observed from the total voltage measurements that closed to the theoretical value. The battery efficiency generally increased as the volume of the electrolytes enlarged.

  11. In-situ measurement of electroosmotic drag coefficient in Nafion membrane for the PEMFC.

    PubMed

    Peng, Zhe; Morin, Arnaud; Huguet, Patrice; Schott, Pascal; Pauchet, Joël

    2011-11-10

    A new method based on hydrogen pump has been developed to measure the electroosmotic drag coefficient in representative PEMFC operating conditions. It allows eliminating the back-flow of water which leads to some errors in the calculation of this coefficient with previously reported electrochemical methods. Measurements have been performed on 50 μm thick Nafion membranes both extruded and recast. Contrary to what has been described in most of previous published works, the electroosmotic drag coefficient decreases as the membrane water content increases. The same trend is observed for temperatures between 25 and 80 °C. For the same membrane water content, the electroosmotic drag coefficient increases with temperature. In the same condition, there is no difference in drag coefficient for extruded Nafion N112 and recast Nafion NRE212. These results are discussed on the basis of the two commonly accepted proton transport mechanisms, namely, Grotthus and vehicular.

  12. Properties of the Nafion membrane impregnated with hydroxyl ammonium based ionic liquids

    NASA Astrophysics Data System (ADS)

    Garaev, Valeriy; Kleperis, Janis; Pavlovica, Sanita; Vaivars, Guntars

    2012-08-01

    In this work, the Nafion 112 membrane impregnated with nine various hydroxyl ammonium based ionic liquids have been investigated. The used ionic liquids were combined from hydroxyl ammonium cations (2-hydroxyethylammonium/HEA, bis(2- hydroxyethyl)ammonium/BHEA, tris(2-hydroxyethyl)ammonium/THEA) and carboxylate anions (formate, acetate, lactate). The membranes are characterized by conductivity and thermal stability measurements. It was found, that almost all composites have 10 times higher ion conductivity than a pure Nafion 112 at 90 °C in ambient environment due to the higher thermal stability. The thermal stability of Nafion membrane was increased by all studied nine ionic liquids. In this work, only biodegradable ionic liquids were used for composite preparation.

  13. A monolayer graphene - Nafion sandwich membrane for direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Yan, X. H.; Wu, Ruizhe; Xu, J. B.; Luo, Zhengtang; Zhao, T. S.

    2016-04-01

    Methanol crossover due to the low selectivity of proton exchange membranes is a long-standing issue in direct methanol fuel cell technology. Here we attempt to address this issue by designing a composite membrane fabricated by sandwiching a monolayer graphene between two thin Nafion membranes to take advantage of monolayer graphene's selective permeability to only protons. The methanol permeability of the present membrane is demonstrated to have a 68.6% decrease in comparison to that of the pristine Nafion membrane. The test in a passive direct methanol fuel cell (DMFC) shows that the designed membrane retains high proton conductivity while substantially suppressing methanol crossover. As a result, the present membrane enables the passive DMFC to exhibit a decent performance even at a methanol concentration as high as 10.0 M.

  14. Exfoliated Pt-clay/Nafion nanocomposite membrane for self-humidifying polymer electrolyte fuel cells.

    PubMed

    Zhang, Wenjing; Li, Martin Ka Shing; Yue, Po-Lock; Gao, Ping

    2008-03-18

    Monolayers of Pt nanoparticles of diameters of 2-3 nm with a high crystallinity were successfully anchored onto exfoliated nanoclay surfaces using a novel chemical vapor deposition process. Chemical bonding of Pt to the oxygen on the clay surface ensured the stability of the Pt nanoparticles, and hence, no leaching of Pt particles was observed after a prolonged ultrasonication and a rigorous mechanical agitation of Pt-clay in the Nafion solution during the membrane casting process. Systematic analysis using WAXD and TEM showed that the recasting process produced a new self-humidifying exfoliated Pt-clay/Nafion nanocomposite membrane with a high crystallinity and proton conductivity. In situ water production for humidification of the dry membranes without any external humidification was characterized by a combined water uptake and FTIR analysis of the as-prepared membrane after a single cell testing without using electrodes. The power density at 0.5 V of a single cell made of a Pt-clay/Nafion nanocomposite membrane was 723 mW/cm2, which is 170% higher than that made of a commercial Nafion 112 membrane of similar thickness. No compromise in mechanical properties was observed.

  15. Electro-osmotic drag effect on the methanol permeation for sulfonated poly(ether ether ketone) and nafion 117 membranes.

    PubMed

    Chi, Nguyen Thi Que; Bae, Byungchan; Kim, Dukjoon

    2013-11-01

    Electro-osmotic drag effect on the methanol permeation was investigated for sulfonated poly(ether ether ketone) (sPEEK) membrane, and its result was compared with that of Nafion 117 membrane. The electro-osmotic drag coefficient was determined from the limiting current density measured at different temperature. The methanol permeability of sPEEK membrane increased with temperature but its temperature dependence was not as strong as that of Nafion 117 membrane. The methanol permeability or the total methanol flux of Nafion 117 membrane was at least twice higher than that of sPEEK70 membrane (sPEEK membrane with 70% sulfonation degree), as the methanol permeation was highly contributed by the electro-osmotic drag effect. This higher electro-osmotic drag of Nafion 117 membrane is attributed to the bigger ion cluster and waster channel in nanophase and thus more free water absorption than sPEEK membrane.

  16. PEDOT:PSS self-assembled films to methanol crossover reduction in Nafion® membranes

    NASA Astrophysics Data System (ADS)

    Almeida, Tiago P.; Miyazaki, Celina M.; Paganin, Valdecir A.; Ferreira, Marystela; Saeki, Margarida J.; Perez, Joelma; Riul, Antonio

    2014-12-01

    Alternative energy sources are on a global demand, with fuel cells as promising devices from mobile to stationary applications. Nafion® is at the heart of many of these appliances, being mostly used due to its high proton conduction and good chemical stability at ambient temperature in proton exchange membranes (PEM). Therefore, methanol permeation throughout Nafion® films reduces drastically the performance of direct methanol fuel cells (DMFC). We present here the deposition of layer-by-layer (LbL) nanostructured thin films of poly(allylamine hydrochloride) (PAH) and poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) onto commercial Nafion® 212 membranes. It was observed a good adherence of the LbL films onto Nafion® 212, with UV-vis results displaying a linear characteristic growth, indicative that the same amount of material was deposited at each deposition step during the layer-by-layer assembly. In addition, the LbL films also act as a good barrier to avoid methanol crossover, with an observed reduction in the methanol permeation from 5.5 × 10-6 cm2 s-1 to 3.2 × 10-6 cm2 s-1, respectively to pristine Nafion® 212 and a 5-bilayer PAH/PEDOT:PSS LbL film deposited on Nafion®212. The measured power density in a DMFC set-up was not significantly changed (∼12 mW cm-2) due to the LbL films, since the PAH/PEDOT:PSS nanostructure is impeding water and ion transport, consequently affecting the proton conduction throughout the membrane.

  17. Characterization of direct methanol fuel cell (DMFC) applications with H 2SO 4 modified chitosan membrane

    NASA Astrophysics Data System (ADS)

    Osifo, Peter O.; Masala, Aluwani

    Chitosan (Chs) flakes were prepared from chitin materials that were extracted from the exoskeleton of Cape rock lobsters in South Africa. The Chs flakes were prepared into membranes and the Chs membranes were modified by cross-linking with H 2SO 4. The cross-linked Chs membranes were characterized for the application in direct methanol fuel cells. The Chs membrane characteristics such as water uptake, thermal stability, proton resistance and methanol permeability were compared to that of high performance conventional Nafion 117 membranes. Under the temperature range studied 20-60 °C, the membrane water uptake for Chs was found to be higher than that of Nafion. Thermal analysis revealed that Chs membranes could withstand temperature as high as 230 °C whereas Nafion 117 membranes were stable to 320 °C under nitrogen. Nafion 117 membranes were found to exhibit high proton resistance of 284 s cm -1 than Chs membranes of 204 s cm -1. The proton fluxes across the membranes were 2.73 mol cm -2 s -1 for Chs- and 1.12 mol cm -2 s -1 Nafion membranes. Methanol (MeOH) permeability through Chs membrane was less, 1.4 × 10 -6 cm 2 s -1 for Chs membranes and 3.9 × 10 -6 cm 2 s -1 for Nafion 117 membranes at 20 °C. Chs and Nafion membranes were fabricated into membrane electrode assemblies (MAE) and their performances measure in a free-breathing commercial single cell DMFC. The Nafion membranes showed a better performance as the power density determined for Nafion membranes of 0.0075 W cm -2 was 2.7 times higher than in the case of Chs MEA.

  18. Poly (vinylidene fluoride-co-hexafluoropropylene)/polybenzimidazole blend nanofiber supported Nafion membranes for direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Wang, Shih-Hua; Lin, Hsiu-Li

    2014-07-01

    This article presents preparation of poly (vinylidene fluoride-co-hexafluoropropylene) (PVdF-co-HFP) and polybenzimidazole (PBI) blend electrospun nanofiber (PVFP-BI) films from N,N‧-dimethyl acetamide (DMAc)/acetone mixture solutions. Using the PVFP-BI nanofiber film (thickness ∼13-15 μm) as a supporting material for impregnating Nafion resin solution, Nafion/PVFP-BI composite membranes (thickness ∼50 μm) are prepared and direct methanol fuel cell (DMFC) tests are performed. Better DMFC performance of the Nafion/PVFP-BI composite membrane than the commercial Nafion-117 (thickness ∼175 μm) and Nafion-212 (thickness ∼50 μm) membranes when blending with 5-10 wt.% of PBI in the PVFP-BI nanofiber support film is demonstrated.

  19. Electrocatalytic response of poly(cobalt tetraaminophthalocyanine)/multi-walled carbon nanotubes-Nafion modified electrode toward sulfadiazine in urine.

    PubMed

    Hong, Xiao-ping; Zhu, Yan; Zhang, Yan-zhen

    2012-06-01

    A highly sensitive amperometric sulfadiazine sensor fabricated by electrochemical deposition of poly(cobalt tetraaminophthalocyanine) (poly(Co(II)TAPc)) on the surface of a multi-walled carbon nanotubes-Nafion (MWCNTs-Nafion) modified electrode is described. This electrode showed a very attractive performance by combining the advantages of Co(II)TAPc, MWCNTs, and Nafion. Compared with the bare glassy carbon electrode (GCE) and the MWCNTs-Nafion modified electrode, the electrocatalytic activity of poly(Co(II)TAPc)-coated MWCNTs-Nafion GCE generated greatly improved electrochemical detections toward sulfadiazine including low oxidation potential, high current responses, and good anti-fouling performance. The oxidation peak currents of sulfadiazine obtained on the new modified electrode increased linearly while increasing the concentration of sulfadiazine from 0.5 to 43.5 μmol/L with the detection limit of 0.17 μmol/L.

  20. Investigation of Local Environments in Nafion-SiO2 Composite Membranes used in Vanadium Redox Flow Batteries

    SciTech Connect

    Vijayakumar, M.; Schwenzer, Birgit; Kim, Soowhan; Yang, Zhenguo; Thevuthasan, Suntharampillai; Liu, Jun; Graff, Gordon L.; Hu, Jian Z.

    2012-04-01

    The proton conducting polymer composite membranes are of technological interest in many energy devices such as fuel cells and redox flow batteries. In particular, the polymer composite membranes such as SiO2 incorporated Nafion membranes are recently reported as highly promising for the redox flow batteries. However, there is conflicting reports regarding the performance of this Nafion-SiO2 composite membrane in the redox flow cell. This paper presents results of the analysis of the Nafion-SiO2 composite membrane used in a vanadium redox flow battery by nuclear magnetic resonance (NMR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier Transformed Infra Red (FTIR) spectroscopy, and ultraviolet visible spectroscopy. The XPS study reveals the chemical identity and environment of vanadium cations accumulated at the surface. On the other hand, the 19F and 29Si NMR measurement explores the nature of the interaction between the silica particles, Nafion side chains and diffused vanadium cations. The 29Si NMR shows that the silica particles interaction via hydrogen bonds to the sulfonic groups of Nafion and diffused vanadium cations. Based on these spectroscopic studies, the chemical environment of the silica particles inside the Nafion membrane and their interaction with diffusing vanadium cations during flow cell operations are discussed. This study discusses the origin of performance degradation of the Nafion-SiO2 composite membrane materials in vanadium redox flow batteries.

  1. Investigation of local environments in Nafion-SiO(2) composite membranes used in vanadium redox flow batteries.

    PubMed

    Vijayakumar, M; Schwenzer, Birgit; Kim, Soowhan; Yang, Zhenguo; Thevuthasan, S; Liu, Jun; Graff, Gordon L; Hu, Jianzhi

    2012-04-01

    Proton conducting polymer composite membranes are of technological interest in many energy devices such as fuel cells and redox flow batteries. In particular, polymer composite membranes, such as SiO(2) incorporated Nafion membranes, are recently reported as highly promising for the use in redox flow batteries. However, there is conflicting reports regarding the performance of this type of Nafion-SiO(2) composite membrane in the redox flow cell. This paper presents results of the analysis of the Nafion-SiO(2) composite membrane used in a vanadium redox flow battery by nuclear magnetic resonance (NMR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier Transform Infra Red (FTIR) spectroscopy, and ultraviolet-visible spectroscopy. The XPS study reveals the chemical identity and environment of vanadium cations accumulated at the surface. On the other hand, the (19)F and (29)Si NMR measurement explores the nature of the interaction between the silica particles, Nafion side chains and diffused vanadium cations. The (29)Si NMR shows that the silica particles interact via hydrogen bonds with the sulfonic groups of Nafion and the diffused vanadium cations. Based on these spectroscopic studies, the chemical environment of the silica particles inside the Nafion membrane and their interaction with diffusing vanadium cations during flow cell operations are discussed. This study discusses the origin of performance degradation of the Nafion-SiO(2) composite membrane materials in vanadium redox flow batteries. Copyright © 2011 Elsevier Inc. All rights reserved.

  2. Composite Nafion/sulfonated zirconia membranes: effect of the filler surface properties on proton transport characteristics

    PubMed Central

    D’Epifanio, Alessandra; Navarra, Maria Assunta; Weise, F. Christoph; Mecheri, Barbara; Farrington, Jaime; Licoccia, Silvia; Greenbaum, Steve

    2009-01-01

    Due to their strong acidity and water affinity, sulfated zirconia nanoparticles were evaluated as inorganic additives in the formation of composite Nafion-based membranes. Two types of sulfated zirconia were obtained according to the preparation experimental conditions. Sulfated zirconia-doped Nafion membranes were prepared by a casting procedure. The properties of the composite membranes were compared with those of an unfilled Nafion membrane obtained by the same preparation method. The water uptake, measured at room temperature in a wide relative humidity range, was higher for the composite membranes, this confirming the hydrophilic nature of the selected additives. The membrane doped by zirconia particles having the highest sulphate group concentration showed the highest water diffusion coefficient in the whole range of temperature and relative humidity investigated due to the presence of SO42− providing extra acid sites for water diffusion. The proton diffusivity calculated from impedance spectroscopy measurements was compared with water self diffusion coefficients measured by NMR Spectroscopy. The difference between proton and water diffusivity became significant only at high humidification levels, highlighting the role of water in the intermolecular proton transfer mechanism. Finally, great improvements were found when using the composite membrane as electrolyte in a fuel cell working at very low relative humidity. PMID:20209115

  3. Membrane crystallinity and fuel crossover in direct ethanol fuel cells with Nafion composite membranes containing phosphotungstic acid

    SciTech Connect

    Kim, Hongjun; Lee, Sunghwan; Kim, Suran; Oh, Chungik; Ryu, Jeongjae; Kim, Jaegyu; Park, Eugene; Hong, Seungbum; No, Kwangsoo

    2016-11-01

    Interest has been growing in direct ethanol fuel cells (DEFCs) due to their non-toxicity, low cost and potential contribution to energy issues in third world countries. A reduction in fuel cross-over is of key importance to enhance the performance of DEFCs that operate at low temperatures (<100 °C). We report on the effect of the addition of phosphotungstic acid (PWA) in Nafion membrane on the ethanol-crossover for DEFC application. A set of PWANafion composite membranes (PWA 0, 5, 10, 15, 20 wt%) was prepared by solution casting and their microstructures, diffraction patterns and permeability were systematically characterized. The significant reduction in ethanol-crossover was observed with increasing PWA concentration in PWA-Nafion membranes, which was mainly attributed to an improvement in crystallinity of the membrane. PWA provides additional nucleation sites during solidification leading to higher crystallinity, which is supported by the membrane permeability tests. These PWA-Nafion composites were implemented in proto-type DEFC devices as a membrane and the maximum power density achieved was 22% higher than that of commercial Nafion-117 device.

  4. Membrane crystallinity and fuel crossover in direct ethanol fuel cells with Nafion composite membranes containing phosphotungstic acid

    DOE PAGES

    Kim, Hongjun; Lee, Sunghwan; Kim, Suran; ...

    2016-11-01

    Interest has been growing in direct ethanol fuel cells (DEFCs) due to their non-toxicity, low cost and potential contribution to energy issues in third world countries. A reduction in fuel cross-over is of key importance to enhance the performance of DEFCs that operate at low temperatures (<100 °C). We report on the effect of the addition of phosphotungstic acid (PWA) in Nafion membrane on the ethanol-crossover for DEFC application. A set of PWANafion composite membranes (PWA 0, 5, 10, 15, 20 wt%) was prepared by solution casting and their microstructures, diffraction patterns and permeability were systematically characterized. The significant reductionmore » in ethanol-crossover was observed with increasing PWA concentration in PWA-Nafion membranes, which was mainly attributed to an improvement in crystallinity of the membrane. PWA provides additional nucleation sites during solidification leading to higher crystallinity, which is supported by the membrane permeability tests. These PWA-Nafion composites were implemented in proto-type DEFC devices as a membrane and the maximum power density achieved was 22% higher than that of commercial Nafion-117 device.« less

  5. Self-assembly in Nafion membranes upon hydration: water mobility and adsorption isotherms.

    PubMed

    Vishnyakov, Aleksey; Neimark, Alexander V

    2014-09-25

    By means of dissipative particle dynamics (DPD) and Monte Carlo (MC) simulations, we explored geometrical, transport, and sorption properties of hydrated Nafion-type polyelectrolyte membranes. Composed of a perfluorinated backbone with sulfonate side chains, Nafion self-assembles upon hydration and segregates into interpenetrating hydrophilic and hydrophobic subphases. This segregated morphology determines the transport properties of Nafion membranes that are widely used as compartment separators in fuel cells and other electrochemical devices, as well as permselective diffusion barriers in protective fabrics. We introduced a coarse-grained model of Nafion, which accounts explicitly for polymer rigidity and electrostatic interactions between anionic side chains and hydrated metal cations. In a series of DPD simulations with increasing content of water, a classical percolation transition from a system of isolated water clusters to a 3D network of hydrophilic channels was observed. The hydrophilic subphase connectivity and water diffusion were studied by constructing digitized replicas of self-assembled morphologies and performing random walk simulations. A non-monotonic dependence of the tracer diffusivity on the water content was found. This unexpected behavior was explained by the formation of large and mostly isolated water domains detected at high water content and high equivalent polymer weight. Using MC simulations, we calculated the chemical potential of water in the hydrated polymer and constructed the water sorption isotherms, which extended to the oversaturated conditions. We determined that the maximum diffusivity and the onset of formation of large water domains corresponded to the saturation conditions at 100% humidity. The oversaturated membrane morphologies generated in the canonical ensemble DPD simulations correspond to the metastable and unstable states of Nafion membrane that are not realized in the experiments.

  6. Low energy plasma treatment of Nafion ® membranes for PEM fuel cells

    NASA Astrophysics Data System (ADS)

    Ramdutt, Devin; Charles, Christine; Hudspeth, Jessica; Ladewig, Bradley; Gengenbach, Thomas; Boswell, Rod; Dicks, Andrew; Brault, Pascal

    Understanding the effects plasmas have on polymer electrolyte membranes such as Nafion is important if plasma technologies are to be employed in the fabrication of MEA components. An argon plasma has been used to treat the surface of Nafion membranes at several energy doses from 0 to 3.056 J cm -2. The effect of the treatment has been characterised using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS) as well as measuring water contact angles, proton conductivity and electrical performance. It was found that as energy dose is increased, hydrophobicity of the membrane decreases, as does proton conductivity. The water contact angle for untreated Nafion is around 120° while the surface treated with the maximum dose has a contact angle of 50°. Similarly the proton conductivity drops from above 200 to 35.8 mS cm -1. SEM and AFM results showed only a small change in the surface roughness of the treated samples while XPS results indicated a marked reduction in the concentration of fluorine at the surface of the membrane for increasing dose. Fuel cell electrical performance was also very poor for the treated membranes and this was attributed to the decrease in conductivity as well as an observed poor adherence between electrode and membrane in the pressed MEA.

  7. Pervaporation of Water from Aqueous Sulfuric Acid at Elevated Temperatures Using Nafion® Membranes

    SciTech Connect

    Christopher J. Orme; Frederick F. Stewart

    2009-01-01

    The concentration of sulfuric acid by pervaporation has been studied using Nafion-112® and Nafion-117® membranes, which have been characterized in terms of flux, permeability, and selectivity at 100 ºC and 120 ºC. Feed concentrations investigated ranged from 40 to over 80 weight percent. In general, water fluxes ranged from 100-8000 g/m2h, depending on feed acid concentration and separations factors as high as 104 were observed. Membrane stability was probed using Dynamic Mechanical Analysis that revealed some embrittlement of the membranes during use. Further studies showed that the embrittlement was due to an interaction with the acid and was not induced by the operating temperature.

  8. Enhanced proton conductivity of Nafion composite membrane by incorporating phosphoric acid-loaded covalent organic framework

    NASA Astrophysics Data System (ADS)

    Yin, Yongheng; Li, Zhen; Yang, Xin; Cao, Li; Wang, Chongbin; Zhang, Bei; Wu, Hong; Jiang, Zhongyi

    2016-11-01

    Design and fabrication of efficient proton transport channels within solid electrolytes is crucial and challenging to new energy-relevant devices such as proton exchange membrane fuel cells (PEMFCs). In this study, the phosphoric acid (H3PO4) molecules are impregnated into SNW-1-type covalent organic frameworks (COFs) via vacuum assisted method. High loading of H3PO4 in SNW-1 and low guest leaching rate are achieved due to the similar diameter between H3PO4 and micropores in SNW-1. Then the COF-based composite membranes are fabricated for the first time with impregnated COFs (H3PO4@SNW-1) and Nafion matrix. For the composite membranes, the acid-base pairs formed between H3PO4@SNW-1 networks and Nafion optimize the interfacial interactions and hydrophilic domains. The acidic -PO3H2 groups in pores of H3PO4@SNW-1 provide abundant proton transfer sites. As a result, the continuous proton transfer channels with low energy barrier are created. At the filler content of 15 wt%, the composite membrane exhibits a superior proton conductivity of 0.0604 S cm-1 at 51% relative humidity and 80 °C. At the same time, the maximum power density of single fuel cell is 60.3% higher than that of the recast Nafion membrane.

  9. Nafion electro-spun reinforced membranes for polymer electrolyte fuel cell.

    PubMed

    Carbone, Alessandra; Saccà, Ada; Busacca, Concetta; Frontera, Patrizia; Antonucci, Pier Luigi; Passalacqua, Enza

    2011-10-01

    The introduction of different reinforcement materials (yarns, fibrils, etc) into the membranes has been investigated with the aim of maintaining adequate membrane properties in terms of mechanical strength, good chemical stability, low swelling at critical temperatures and a stable electrochemical performance in PEFC. An innovative technique for the development of membranes is based on polymeric films containing polymeric nanofibres obtained through electrospinning. The electrospinning of Nafion blends with polyvinylpirrolidone (PVP) and polystyrene (PS) was investigated in this work. In particular, the morphology and diameter of electrospun fibres as a function of the electrospinning parameters and solution preparation have been studied and in both cases, a critical concentration of blend solution was found. Beaded fibres were obtained above such a concentration and, below it, only fibre mats were observed. Reinforced Nafion-based membranes were realised by using the obtained spun films. Preliminary proton conductivity and fuel cell results have shown the capability of operating in a fuel cell environment with a slightly higher performance than pure Nafion but having an improved stability at high temperatures.

  10. Proton transport and the water environment in nafion fuel cell membranes and AOT reverse micelles.

    PubMed

    Spry, D B; Goun, A; Glusac, K; Moilanen, David E; Fayer, M D

    2007-07-04

    The properties of confined water and diffusive proton-transfer kinetics in the nanoscopic water channels of Nafion fuel cell membranes at various hydration levels are compared to water in a series of well-characterized AOT reverse micelles with known water nanopool sizes using the photoacid pyranine as a molecular probe. The side chains of Nafion are terminated by sulfonate groups with sodium counterions that are arrayed along the water channels. AOT has sulfonate head groups with sodium counterions that form the interface with the reverse micelle's water nanopool. The extent of excited-state deprotonation is observed by steady-state fluorescence measurements. Proton-transfer kinetics and orientational relaxation are measured by time-dependent fluorescence using time-correlated single photon counting. The time dependence of deprotonation is related to diffusive proton transport away from the photoacid. The fluorescence reflecting the long time scale proton transport has an approximately t-0.8 power law decay in contrast to bulk water, which has a t-3/2 power law. For a given hydration level of Nafion, the excited-state proton transfer and the orientational relaxation are similar to those observed for a related size AOT water nanopool. The effective size of the Nafion water channels at various hydration levels are estimated by the known size of the AOT reverse micelles that display the corresponding proton-transfer kinetics and orientational relaxation.

  11. Pervaporation of Water from Aqueous Hydriodic Acid and Iodine Mixtures Using Nafion (R) Membranes

    SciTech Connect

    Christopher J. Orme; Frederick F. Stewart

    2007-11-01

    The sulfur-iodine (S-I) process for generation of hydrogen has been proposed as a thermochemical cycle for study due to its predicted high efficiencies. Improvements in the cycle that will yield the greatest gain in both operating and capital costs involve chemical separations. To date, membrane processes have been largely unexplored. In this work, a materials compatibility study into the application of Nafion-117® and Nafion-112® as membranes for the pervaporation of water from aqueous mixtures of hydriodic acid (HI) and HI/iodine at 134 ºC was conducted. Significant fluxes of water were measured with respect to feed water concentration and high separation factors were calculated. Most surprisingly, HI and HI/iodine feeds acted very differently in that HI-iodine complexes formed result in higher fluxes and separation factors than what was observed for HI alone.

  12. Passive approach for the improved dispersion of polyvinyl alcohol-based functionalized multi-walled carbon nanotubes/Nafion membranes for polymer electrolyte membrane fuel cells.

    PubMed

    Abu Sayeed, M D; Talukdar, Krishan; Kim, Hee Jin; Park, Younjin; Gopalan, A I; Kim, Young Ho; Lee, Kwang-Pill; Choi, Sang-June

    2014-12-01

    Multi-walled carbon nanotubes (MWCNTs) are regarded as ideal fillers for Nafion polymer electrolyte membranes (PEMs) for fuel cell applications. The highly aggregated properties of MWCNTs can be overcome by the successful cross-linking with polyvinyl alcohol (PVA) into the MWCNTs/Nafion membrane. In this study, a series of nanocomposite membranes were fabricated with the PVA-influenced functionalized MWCNTs reinforced into the Nafion polymer matrix by a solution casting method. Several different PVA contents were blended to f-MWCNTs/Nafion nanocomposite membranes followed by successful cross-linking by annealing. The surface morphologies and the inner structures of the resulting PVA-MWCNTs/Nafion nanocomposite membranes were then observed by optical microscopy and scanning electron microscopy (SEM) to investigate the dispersion of MWCNTs into the PVA/Nafion composite membranes. After that, the nanocomposite membranes were characterized by thermo-gravimetric analysis (TGA) to observe the thermal enhancement caused by effective cross-linking between the f-MWCNTs with the composite polymer matrixes. Improved water uptake with reduced methanol uptake revealed the successful fabrication of PVA-blended f-MWCNTs/Nafion membranes. In addition, the ion exchange capacity (IEC) was evaluated for PEM fuel cell (PEMFC) applications.

  13. Performance evaluation of microbial electrochemical systems operated with Nafion and supported ionic liquid membranes.

    PubMed

    Koók, László; Nemestóthy, Nándor; Bakonyi, Péter; Zhen, Guangyin; Kumar, Gopalakrishnan; Lu, Xueqin; Su, Lianghu; Saratale, Ganesh Dattatraya; Kim, Sang-Hyoun; Gubicza, László

    2017-05-01

    In this work, the performance of dual-chamber microbial fuel cells (MFCs) constructed either with commonly used Nafion(®) proton exchange membrane or supported ionic liquid membranes (SILMs) was assessed. The behavior of MFCs was followed and analyzed by taking the polarization curves and besides, their efficiency was characterized by measuring the electricity generation using various substrates such as acetate and glucose. By using the SILMs containing either [C6mim][PF6] or [Bmim][NTf2] ionic liquids, the energy production of these MFCs from glucose was comparable to that obtained with the MFC employing polymeric Nafion(®) and the same substrate. Furthermore, the MFC operated with [Bmim][NTf2]-based SILM demonstrated higher energy yield in case of low acetate loading (80.1 J g(-1) CODin m(-2) h(-1)) than the one with the polymeric Nafion(®) N115 (59 J g(-1) CODin m(-2) h(-1)). Significant difference was observed between the two SILM-MFCs, however, the characteristics of the system was similar based on the cell polarization measurements. The results suggest that membrane-engineering applying ionic liquids can be an interesting subject field for bioelectrochemical system research.

  14. Electrospun sulfonated poly(ether ketone) nanofibers as proton conductive reinforcement for durable Nafion composite membranes

    NASA Astrophysics Data System (ADS)

    Klose, Carolin; Breitwieser, Matthias; Vierrath, Severin; Klingele, Matthias; Cho, Hyeongrae; Büchler, Andreas; Kerres, Jochen; Thiele, Simon

    2017-09-01

    We show that the combination of direct membrane deposition with proton conductive nanofiber reinforcement yields highly durable and high power density fuel cells. Sulfonated poly(ether ketone) (SPEK) was directly electrospun onto gas diffusion electrodes and then filled with Nafion by inkjet-printing resulting in a 12 μm thin membrane. The ionic membrane resistance (30 mΩ*cm2) was well below that of a directly deposited membrane reinforced with chemically inert (PVDF-HFP) nanofibers (47 mΩ*cm2) of comparable thickness. The power density of the fuel cell with SPEK reinforced membrane (2.04 W/cm2) is 30% higher than that of the PVDF-HFP reinforced reference sample (1.57 W/cm2). During humidity cycling and open circuit voltage (OCV) hold, the SPEK reinforced Nafion membrane showed no measurable degradation in terms of H2 crossover current density, thus fulfilling the target of 2 mA/cm2 of the DOE after degradation. The chemical accelerated stress test (100 h OCV hold at 90 °C, 30% RH, H2/air, 50/50 kPa) revealed a degradation rate of about 0.8 mV/h for the fuel cell with SPEK reinforced membrane, compared to 1.0 mV/h for the PVDF-HFP reinforced membrane.

  15. Spatial and temporal mapping of water content across Nafion membranes under wetting and drying conditions.

    PubMed

    Zhang, Ziheng; Marble, Andrew E; MacMillan, Bryce; Promislow, Keith; Martin, Jonathan; Wang, Haijiang; Balcom, Bruce J

    2008-10-01

    Water transport and water management are fundamental to polymer electrolyte membrane fuel cell operation. Accurate measurements of water content within and across the Nafion layer are required to elucidate water transport behavior and validate existing numerical models. We report here a direct measurement of water content profiles across a Nafion layer under wetting and drying conditions, using a novel magnetic resonance imaging methodology developed for this purpose. This method, multi-echo double half k-space spin echo single point imaging, based on a pure phase encode spin echo, is designed for high resolution 1D depth imaging of thin film samples. The method generates high resolution (<8 microm) depth images with an SNR greater than 20, in an image acquisition time of less than 2 min. The high temporal resolution permits water content measurements in the transient states of wetting and drying, in addition to the steady state.

  16. Bacterial nanocellulose/Nafion composite membranes for low temperature polymer electrolyte fuel cells

    NASA Astrophysics Data System (ADS)

    Jiang, Gao-peng; Zhang, Jing; Qiao, Jin-li; Jiang, Yong-ming; Zarrin, Hadis; Chen, Zhongwei; Hong, Feng

    2015-01-01

    Novel nanocomposite membranes aimed for both proton-exchange membrane fuel cell (PEMFC) and direct methanol fuel cell (DMFC) are presented in this work. The membranes are based on blending bacterial nanocellulose pulp and Nafion (abbreviated as BxNy, where x and y indicates the mass ratio of bacterial cellulose to Nafion). The structure and properties of BxNy membranes are characterized by FTIR, SEM, TG, DMA and EIS, along with water uptake, swelling behavior and methanol permeability tests. It is found that the BxNy composite membranes with reinforced concrete-like structure show excellent mechanical and thermal stability regardless of annealing. The water uptake plus area and volume swelling ratios are all decreased compared to Nafion membranes. The proton conductivities of pristine and annealed B1N9 are 0.071 and 0.056 S cm-1, respectively, at 30 °C and 100% humidity. Specifically, annealed B1N1 exhibited the lowest methanol permeability of 7.21 × 10-7 cm2 s-1. Through the selectivity analysis, pristine and annealed B1N7 are selected to assemble the MEAs. The performances of annealed B1N7 in PEMFC and DMFC show the maximum power densities of 106 and 3.2 mW cm-2, respectively, which are much higher than those of pristine B1N7 at 25 °C. The performances of the pristine and annealed B1N7 reach a level as high as 21.1 and 20.4 mW cm-2 at 80 °C in DMFC, respectively.

  17. Nafion/poly(1-vinyl imidazole) composite membranes for fuel cell application

    NASA Astrophysics Data System (ADS)

    Kim, Dukjoon

    2008-03-01

    A base monomer (1-vinyl imidazole, VIDz) was polymerized in Nafion^ 112 membrane by UV irradiation in order to reduce methanol permeability of the latter. With increasing content of poly 1-vinyl imidazole (PVI), equilibrium water uptake was decreased due to reduced size of hydrated ion cluster in the composite membrane as confirmed by a small angle X-ray scattering analysis. The electrochemical properties of the membrane such as ion conductivity, methanol permeability and electro-osmotic drag were also affected by equilibrium water uptake and hydrated pore size. Even a minute incorporation of the base polymer showed a significant effect on proton conductivity and methanol permeability. Methanol transport by electro-osmotic drag was evaluated by using relating equations and methanol permeability and limiting current density data obtained in this study. Although the absolute number of electro-osmotic drag was hard to determine, the trend of change could be studied in relation to bulk-like water in composite membranes. This novel composite membrane exhibited an increased cell performance compared with a plain Nafion membrane due to reduced methanol crossover rate.

  18. Comparison of electrochemical and microbiological characterization of microbial fuel cells equipped with SPEEK and Nafion membrane electrode assemblies.

    PubMed

    Suzuki, Kei; Owen, Rubaba; Mok, Joann; Mochihara, Hiroki; Hosokawa, Takuya; Kubota, Hiroko; Sakamoto, Hisatoshi; Matsuda, Atsunori; Tashiro, Yosuke; Futamata, Hiroyuki

    2016-09-01

    Microbial fuel cells equipped with SPEEK-MEA (SPEEK-MFC) and Nafion-MEA (Nafion-MFC) were constructed with organic waste as electron donor and lake sediment as inoculum and were then evaluated comprehensively by electrochemical and microbial analyses. The proton conductivity of SPEEK was several hundreds-fold lower than that of Nafion 117, whereas the oxygen mass and diffusion transfer coefficients of SPEEK were 10-fold lower than those of Nafion 117. It was difficult to predict which was better membrane for MFC based on the feature of membrane. Analyses of polarization curves indicated that the potential of electricity production was similar in both MFCs, as the SPEEK-MFC produced 50-80% of the practical current density generated by the Nafion-MFC. Chronopotentiometry analyses indicated that the Nafion-MEA kept the performance longer than the SPEEK-MEA for long period, whereas performance of both anodes improved on time. Multidimensional scaling analyses based on DGGE profiles revealed the anolytic and biofilm communities of the SPEEK-MFC had developed differently from those of the Nafion-MFC. Clone library analyses indicated that Geobacter spp. represented 6.3% of the biofilm bacterial community in the Nafion-MFC but not detected in the SPEEK-MFC. Interestingly, the clone closely related to Acetobacterium malicum strain HAAP-1, belonging to the homoacetogens, became dominant in both anolytic and biofilm communities of the SPEEK-MFC. It was suggested that the lower proton conductivity of SPEEK-MEA allowed the bacteria closely related to strain HAAP-1 to be dominant specifically in SPEEK-MFC. These results indicated that Nafion-MFC ranked with SPEEK-MFC and that MEAs had strong selective pressure for electricity-producing bacterial community.

  19. Simultaneous determination of 2-nitrophenol and 4-nitrophenol based on the multi-wall carbon nanotubes Nafion-modified electrode.

    PubMed

    Huang, Wensheng; Yang, Chunhai; Zhang, Shenghui

    2003-03-01

    In this work, multi-wall carbon nanotubes (MWNT) were conveniently dispersed into Nafion-ethanol solution, and the MWNT-Nafion-modified glassy carbon electrode (GCE) was described for the simultaneous determination of 2-nitrophenol and 4-nitrophenol. At pH 4.0 phosphate buffer, the reduction peak currents of 2-nitrophenol (at -0.8 V) and 4-nitrophenol (at -1.0 V) increase significantly at the MWNT-Nafion-modified GCE, in comparison with that at the Nafion-modified GCE and the bare GCE. The experimental parameters, such as solution pH of phosphate buffer, accumulation potential and time, and the amounts of MWNT-Nafion onto the GCE surface, were optimized. The reduction peak currents are linear with the concentration of 2-nitrophenol from 5 x 10(-8) to 1 x 10(-5) mol L(-1) and with that of 4-nitrophenol from 1 x 10(-7) to 1 x 10(-5) mol L(-1). The detection limits after 3-min accumulation are 1 x 10(-8) mol L(-1) for 2-nitrophenol and for 4 x 10(-8) mol L(-1) for 4-nitrophenol. This modified electrode was applied to direct determination of 2-nitrophenol and 4-nitrophenol in lake water samples.

  20. Preconcentration of diluted biochemical samples using microchannel with integrated nanoscale Nafion membrane.

    PubMed

    Chao, Chen-Chiao; Chiu, Ping-Hsien; Yang, Ruey-Jen

    2015-04-01

    A microfluidic preconcentration device comprising a microchannel and a surface-patterned nanoscale Nafion membrane is proposed. Given the application of an electric field across the chip, the nanopore within Nafion membrane becomes ion selective due to an overlapping of the electric double layer. The resulting difference in flux of the co- and counter-ions within the membrane nanopore prompts the formation of a concentration gradient and leads to a gradual accumulation of the co-ions at the micro-nano junction. It is shown experimentally that the rate of concentration and the preconcentration factor both increase with an increasing electrical field intensity. The preconcentration performance in a straight microchannel is compared with that in a convergent microchannel using fluorescein disodium salt dehydrate and Fluorescein isothiocyanate (FITC)-labeled bovine serum albumin samples. The results show that the reduced cross-sectional area of the convergent microchannel increases the preconcentration factor compared to that obtained in a straight microchannel and yields a significant reduction in the preconcentration time.

  1. Large deformation ionic polymer-metal composites actuators based on porous Nafion membranes

    NASA Astrophysics Data System (ADS)

    Zhao, Dongxu; Li, Dichen; Wang, Yanjie; Luo, Meng; Chen, Hualing

    2016-04-01

    With advantages of low driving voltage, good flexibility and high electromechanical efficiency, ionic polymer-metal composites (IPMCs), which are one of the most attractive smart materials, have been research hotspot in actuators, sensors and artificial muscles. However, a serious drawback of little deformation of thick IPMC actuator limits its application. In this paper, we fabricated thick porous Nafion membranes by freeze-drying process. A series of Thermogravimetric analyses (TGA), Field emission scanning electron microscopy (FE-SEM) and Water uptake (WUP) tests were performed to examine the validity of the freeze-drying process and the pore size and the porosity. Then, the porous IPMCs were fabricated with the freeze-drying processed Nafion membranes by the solution casting and reducing plating. Finally, the IPMC actuators with the dimensions of 25× 5× 1 in millimeters were achieved and tested. The terminal deformation of the porous IPMC actuator increased by 739.7%, compared with the ordinary IPMC actuator with the same dimensions under the driving voltage of 2VDC.

  2. Coating of Nafion membranes with polyelectrolyte multilayers to achieve high monovalent/divalent cation electrodialysis selectivities.

    PubMed

    White, Nicholas; Misovich, Maria; Yaroshchuk, Andriy; Bruening, Merlin L

    2015-04-01

    Electrodialysis (ED) membranes typically exhibit modest selectivities between monovalent and divalent ions. This paper reports a dramatic enhancement of the monovalent/divalent cation selectivities of Nafion 115 membranes through coating with multilayer poly(4-styrenesulfonate) (PSS)/protonated poly(allylamine) (PAH) films. Remarkably, K(+)/Mg(2+) ED selectivities reach values >1000, and similar monovalent/divalent cation selectivities occur with feed solutions containing K(+) and Ca(2+). For comparison, the corresponding K(+)/Mg(2+) selectivity of bare Nafion 115 is only 1.8 ± 0.1. However, with 0.01 M KNO3 and 0.01 M Mg(NO3)2 in the source phase, as the applied current density increases from 1.27 to 2.54 mA cm(-2), the K(+)/Mg(2+) selectivities of coated membranes decrease from >1000 to 22. Water-splitting at strongly overlimiting current densities may lead to a local pH increase close to the membrane surface and alter film permeability or allow passage of Mg(OH)x species to decrease selectivity. When the source phase contains 0.1 M KNO3 and 0.1 M Mg(NO3)2, the K(+) transference number approaches unity and the K(+)/Mg(2+) selectivity is >20,000, presumably because the applied current is below the limiting value for K(+) and H(+) transport is negligible at this high K(+) concentration. The high selectivities of these membranes may enable electrodialysis applications such as purification of salts that contain divalent or trivalent ions.

  3. A flexible all-inorganic fuel cell membrane with conductivity above Nafion, and durable operation at 150 °C

    NASA Astrophysics Data System (ADS)

    Ansari, Y.; Tucker, T. G.; Huang, W.; Klein, I. S.; Lee, S.-Y.; Yarger, J. L.; Angell, C. A.

    2016-01-01

    The search for fuel cell membranes has focused on carbon backbone polymers, among which Nafion seems to best survive the most severe of the degradation mechanisms - attack by peroxide radicals. Less attention has been given to inorganic membranes because of their generally inflexible nature and lower conductivity, though some SiO2-Nafion composites have shown improved properties. Nafion dominates, despite needing hydration, which then restricts operation to below 100 °C (so CO poisoning problems persist). Described herein is a low cost, flexible, and all-inorganic fiberglass reinforced gel membrane with conductivity exceeding that of Nafion at any temperature above 60 °C. Using Teflon fuel cells, maximum currents > 1 Acm-2 and OCV of 1.03 V at 150 °C are demonstrated. No detectable loss of cell potential was observed over 24 h during 50 mAcm-2 constant current operation at 120 °C while, at 150 °C and maximum power, the degradation rate is intermediate among other high conductivity H3PO4-PBI type membranes. The structure of the membrane is deduced, mainly from 29Si solid state-NMR. The -115 ppm resonance, which is extreme for Q4 Si(O) structures, identifies a zeolite-like SiO2 network, which is "floppy". 31P and 1H NMR establish nano-permeating H3PO4 as the source of the exceptional conductivity.

  4. The kinetics of water sorption in Nafion membranes: a small-angle neutron scattering study.

    PubMed

    Gebel, Gérard; Lyonnard, Sandrine; Mendil-Jakani, Hakima; Morin, Arnaud

    2011-06-15

    The optimization of the water management in proton exchange membrane fuel cells is a major issue for the large-scale development of this technology. In addition to the operating conditions, the membrane water sorption and transport processes obviously control the water management. The main objective of this work is to provide new experimental evidence based on the use of the small-angle neutron scattering (SANS) technique in order to allow a better understanding of water sorption processes. SANS spectra were recorded for membranes equilibrated with either water vapor or liquid. Sorption kinetics data were determined and the SANS spectra were analyzed using the method developed for extracting water concentration profiles across the membrane in operating fuel cells. The water concentration profiles across the membrane are completely flat, which indicates that the water diffusion within the membrane is not the limiting process. This result provides new insight into the numerous data published on these properties. For the first time, the swelling kinetics of a Nafion membrane immersed in liquid water is studied and a complete swelling is obtained in less than 1 min.

  5. Electrochemical performance and transport properties of a Nafion membrane in a hydrogen-bromine cell environment

    NASA Technical Reports Server (NTRS)

    Baldwin, Richard S.

    1987-01-01

    The overall energy conversion efficiency of a hydrogen-bromine energy storage system is highly dependent upon the characteristics and performance of the ion-exchange membrane utilized as a half-cell separator. The electrochemical performance and transport properties of a duPont Nafion membrane in an aqueous HBr-Br2 environment were investigated. Membrane conductivity data are presented as a function of HBr concentration and temperature for the determination of ohmic voltage losses across the membrane in an operational cell. Diffusion-controlled bromine permeation rates and permeabilities are presented as functions of solution composition and temperature. Relationships between the degree of membrane hydration and the membrane transport characteristics are discussed. The solution chemistry of an operational hydrogen-bromine cell undergoing charge from 45% HBr to 5% HBr is discussed, and, based upon the experimentally observed bromine permeation behavior, predicted cell coulombic losses due to bromine diffusion through the membrane are presented as a function of the cell state-of-charge.

  6. Modeling of hydro-thermo-mechanical behavior of Nafion NRE212 for Polymer Electrolyte Membrane Fuel Cells using the Finite Viscoplasticity Theory Based on Overstress for Polymers (FVBOP)

    NASA Astrophysics Data System (ADS)

    Colak, Ozgen U.; Acar, Alperen

    2013-08-01

    The primary aim of this work is to present the modifications made to the Finite Viscoplasticity Theory Based on Overstress for Polymers (FVBOP). This is a unified state variable theory and the proposed changes are designed to account for humidity and temperature effects relevant to the modeling of the hydrothermal deformation behavior of ionomer membranes used in Polymer Electrolyte Membrane Fuel Cells (PEMFC). Towards that end, the flow function, which is responsible for conferring rate dependency in FVBOP, is modified. A secondary objective of this work was to investigate the feasibility of using the storage modulus obtained by Dynamic Mechanical Analysis (DMA) in place of the elasticity modulus obtained from conventional tensile/compressive tests, and find the correlation between the storage modulus and the elasticity modulus. The numerical simulations were juxtaposed against data from tensile monotonic loading and unloading experiments on perfluorosulfonic acid (PFSA) membrane Nafion NRE212 samples which are used extensively as a membrane material in PEMFC. The deformation behavior was modeled at four different temperatures (298, 323, 338, and 353 K—all values below the glass transition temperature of Nafion) and at three water content levels (3, 7 and 8 % swelling). The effects of strain rate, temperature, and hydration were captured well with the modified FVBOP model.

  7. Assembly of an unbalanced charged polyampholyte onto Nafion® to produce high-performance composite membranes.

    PubMed

    Li, Shenghai; Zhang, Suobo; Zhang, Qifeng; Qin, Guorui

    2012-12-28

    A novel SPES-NH(2)-GA-Nafion® composite membrane with higher proton conductivity and lower methanol permeability was fabricated by covalent crosslinking layer-by-layer self-assembly of an unbalanced charged polyampholyte (SPES-NH(2)) and glutaraldehyde (GA) with controllable free sulfonic acid content.

  8. Layer-by-layer self-assembly of PDDA/PWA-Nafion composite membranes for direct methanol fuel cells.

    PubMed

    Yang, Meng; Lu, Shanfu; Lu, Jinlin; Jiang, San Ping; Xiang, Yan

    2010-03-07

    A novel PDDA/PWA-Nafion composite electrolyte membrane with enhanced proton conductivity (sigma) to methanol permeability (P) ratio, sigma/P, was fabricated by layer-by-layer self-assembly of negatively charged water soluble PWA and positively charged polyelectrolyte PDDA.

  9. An acetylcholinesterase biosensor based on platinum nanoparticles-carboxylic graphene-nafion-modified electrode for detection of pesticides.

    PubMed

    Yang, Long; Wang, Guangcan; Liu, Yongjun

    2013-06-15

    A sensitive amperometric acetylcholinesterase (AChE) biosensor based on platinum nanoparticles (Pt NPs), carboxylic graphene (CGR), and nafion (NF)-modified glassy carbon electrode (GCE) has been developed. The Pt NPs-CGR-NF nanocomposites with excellent conductivity, catalysis, and biocompatibility offered an extremely hydrophilic surface for AChE adhesion. Chitosan (CS) was used as cross-linker to immobilize the AChE on Pt-CGR-NF-modified GCE. NF was used as a protective membrane of the AChE biosensors. The AChE biosensor showed favorable affinity to acetylthiocholine chloride (ATCl) and could catalyze the hydrolysis of ATCl with an apparent Michaelis-Menten constant value of 148μM. Under optimum conditions, the biosensor detected methyl parathion in the linear range from 1.0×10(-13) to 1×10(-10)M and from 1.0×10(-10) to 1×10(-8)M with a detection limit of 5×10(-14)M and detected carbofuran in the linear range from 1.0×10(-12) to 1×10(-10)M and from 1.0×10(-10) to 1×10(-8)M with a detection limit of 5×10(-13)M. The biosensor exhibited good sensitivity, acceptable stability, and reproducibility, thus providing a promising tool for analysis of enzyme inhibitors. Copyright © 2013 Elsevier Inc. All rights reserved.

  10. Self-diffusion of ions in Nafion-117 membrane having mixed ionic composition.

    PubMed

    Chaudhury, Sanhita; Agarwal, Chhavi; Pandey, A K; Goswami, A

    2012-02-09

    The self-diffusion coefficients (SDCs) of Na(+), Cs(+), and Ba(2+) have been determined in Nafion-117 membrane having mixed cationic compositions. Membranes with different proportions of Na(+)-Cs(+), Cs(+)-Ba(2+), Na(+)-Ba(2+), and Ag(+)-Ba(2+) cations have been prepared by equilibrating with solutions containing different ratios of these cations. The SDCs of the cations (D(Na), D(Cs), D(Ba)) and the ionic compositions of the membrane have been determined using a radiotracer method. For the Na-Cs and Cs-Ba systems, the SDCs of the cations have been found to be independent of the ionic compositions of the membrane. In the case of the Na-Ba system, D(Na) does not change with ionic composition, while D(Ba) has been found to be strongly dependent on the ionic composition of the membrane and decreases continuously with increasing Na(+) content in the membrane. Similar results have also been obtained for D(Ba) in the case of the Ag-Ba system. The specific conductivities (κ(imp)) of the membrane in mixed cationic forms have also been obtained from ac impedance measurement and compared with that (κ(cal)) calculated from the SDC data. For the Na-Ba system, the increment of κ(imp) with increase in the Na(+) content of the membrane has been found to be parabolic, whereas for the Na-Cs system the increment is linear. The reason behind the different behaviors for different types of ionic systems has been qualitatively explained based on different transport pathways of the cations in the membrane.

  11. Multinuclear solid state nuclear magnetic resonance investigation of water penetration in proton exchange membrane Nafion-117 by mechanical spinning.

    PubMed

    Sabarinathan, Venkatachalam; Wu, Zhen; Cheng, Ren-Hao; Ding, Shangwu

    2013-05-30

    (1)H, (17)O, and (19)F solid state NMR spectroscopies have been used to investigate water penetration in Nafion-117 under mechanical spinning. It is found that both (1)H and (17)O spectra depend on the orientation of the membrane with respect to the magnetic field. The intensities of the side chain (19)F spectra depend slightly on the orientation of membrane with respect to the magnetic field, but the backbone (19)F spectra do not exhibit orientation dependence. By analyzing the orientation dependent (1)H and (17)O spectra and time-resolved (1)H spectra, we show that the water loaded in Nafion-117, under high spinning speed, may penetrate into regions that are normally inaccessible by water. Water penetration is enhanced as the spinning speed is increased or the spinning time is increased. In the meantime, mechanical spinning accelerates water exchange. It is also found that water penetration by mechanical spinning is persistent; i.e., after spinning, water remains in those newly found regions. While water penetration changes the pores and channels in Nafion, (19)F spectra indicate that the chemical environments of the polymer backbone do not show change. These results provide new insights about the structure and dynamics of Nafion-117 and related materials. They are relevant to proton exchange membrane aging and offer enlightening points of view on antiaging and modification of this material for better proton conductivity. It is also interesting to view this phenomenon in the perspective of forced nanofiltration.

  12. Zwitterionic microcapsules as water reservoirs and proton carriers within a Nafion membrane to confer high proton conductivity under low humidity.

    PubMed

    He, Guangwei; Li, Zongyu; Li, Yifan; Li, Zhen; Wu, Hong; Yang, Xinlin; Jiang, Zhongyi

    2014-04-23

    Zwitterionic microcapsules (ZMCs) based on sulfobetaine with tunable hierarchical structures, superior water retention properties, and high proton conduction capacities are synthesized via precipitation polymerization. The incorporation of ZMCs into a Nafion matrix renders the composite membranes with significantly enhanced proton conductivity especially under low humidity. The composite membrane with 15 wt % ZMC-I displayed the highest proton conductivity of 5.8 × 10(-2) S cm(-1) at 40 °C and 20% relative humidity after 90 min of testing, about 21 times higher than that of the Nafion control membrane. The increased proton conductivity is primarily attributed to the versatile roles of ZMCs as water reservoirs and proton conductors for rendering a stable water environment and an additional proton conduction pathway within the membranes. This study may contribute to the rational design of water-retaining and proton-conducting materials.

  13. Magnetic resonance imaging of water content across the Nafion membrane in an operational PEM fuel cell

    NASA Astrophysics Data System (ADS)

    Zhang, Ziheng; Martin, Jonathan; Wu, Jinfeng; Wang, Haijiang; Promislow, Keith; Balcom, Bruce J.

    2008-08-01

    Water management is critical to optimize the operation of polymer electrolyte membrane fuel cells. At present, numerical models are employed to guide water management in such fuel cells. Accurate measurements of water content variation in polymer electrolyte membrane fuel cells are required to validate these models and to optimize fuel cell behavior. We report a direct water content measurement across the Nafion membrane in an operational polymer electrolyte membrane fuel cell, employing double half k-space spin echo single point imaging techniques. The MRI measurements with T2 mapping were undertaken with a parallel plate resonator to avoid the effects of RF screening. The parallel plate resonator employs the electrodes inherent to the fuel cell to create a resonant circuit at RF frequencies for MR excitation and detection, while still operating as a conventional fuel cell at DC. Three stages of fuel cell operation were investigated: activation, operation and dehydration. Each profile was acquired in 6 min, with 6 μm nominal resolution and a SNR of better than 15.

  14. Magnetic resonance imaging of water content across the Nafion membrane in an operational PEM fuel cell.

    PubMed

    Zhang, Ziheng; Martin, Jonathan; Wu, Jinfeng; Wang, Haijiang; Promislow, Keith; Balcom, Bruce J

    2008-08-01

    Water management is critical to optimize the operation of polymer electrolyte membrane fuel cells. At present, numerical models are employed to guide water management in such fuel cells. Accurate measurements of water content variation in polymer electrolyte membrane fuel cells are required to validate these models and to optimize fuel cell behavior. We report a direct water content measurement across the Nafion membrane in an operational polymer electrolyte membrane fuel cell, employing double half k-space spin echo single point imaging techniques. The MRI measurements with T2 mapping were undertaken with a parallel plate resonator to avoid the effects of RF screening. The parallel plate resonator employs the electrodes inherent to the fuel cell to create a resonant circuit at RF frequencies for MR excitation and detection, while still operating as a conventional fuel cell at DC. Three stages of fuel cell operation were investigated: activation, operation and dehydration. Each profile was acquired in 6 min, with 6 microm nominal resolution and a SNR of better than 15.

  15. Transport Properties of Multivalent Cations in Nafion-117 Membrane with Mixed Ionic Composition.

    PubMed

    Chaudhury, Sanhita; Agarwal, Chhavi; Goswami, A

    2015-08-20

    The transport characteristics of multivalent cations like Ba(2+) and Eu(3+) have been studied in bi-ionic form of the Nafion-117 membrane. The membranes have been prepared by loading different proportions of H(+)-Ba(2+)/Mg(2+)-Ba(2+)/Ba(2+)-Eu(3+)/H(+)-Eu(3+)/Na(+)-Eu(3+). The cationic compositions of the membranes have been determined from the measured ion exchange isotherms. Results show that the self-diffusion coefficient of Ba(2+) (D(Ba)) in H-Ba/Mg-Ba systems as well as the self-diffusion coefficient of Eu(3+) (D(Eu)) in H-Eu/Na-Eu systems are strongly dependent on the membrane ionic compositions and decreased continuously with increasing concentration of the highly hydrated ions (H(+)/Na(+)/Mg(2+)) in the membrane. Increase in the proportion of H(+)/Na(+)/Mg(2+) ions in the membrane increases the effective charge on the membrane matrix. This causes stronger electrostatic interaction of the less hydrated multivalent ions (Ba(2+)/Eu(3+)) with the membrane matrix charges, which ultimately results in their slower self-diffusion coefficients. The higher the valence, the stronger the electrostatic interaction is with the fixed ionic charges; hence, in general, D(Eu) is affected more as compared to D(Ba). On the basis of the free-volume theory for polymers, the effective interaction potential (Φ) of the Ba(2+) with the fixed ionic sites in the membrane has been calculated and found to be on the order of approximately millivolts. The higher the proportion of hydrated ion in the membrane, the higher the Φ is and the stronger the ion pair formation is with the fixed ionic sites in the membrane. However, in the Ba-Eu system, as the electrostatic interactions of the two ions with the membrane matrix are close, D(Ba) and D(Eu) are independent of the membrane ionic composition. The ionic composition dependence of D(Ba) in the H-Ba system is reflected in the transport rate of Ba(2+), showing the importance of such measurements in understanding the transport

  16. Small-angle X-ray and neutron scattering study of Nafion-SiO2 hybrid membranes prepared in different solvent media

    NASA Astrophysics Data System (ADS)

    Dresch, M. A.; Matos, B. R.; Fonseca, F. C.; Santiago, E. I.; Carmo, M.; Lanfredi, A. J. C.; Balog, S.

    2015-01-01

    Nafion-SiO2 hybrid electrolytes were synthesized by sol-gel reaction. The homogeneity, structural properties, and proton conductivity of the hybrid membranes were studied. Small-angle scattering analyses indicate that the Nafion structural matrix was preserved on the nanoscale, and the growth of silica particles occurred both in the ionic and nonionic domains of Nafion, which resulted in hybrids with characteristic morphologies. The water uptake and the weight fraction of the inorganic phase were found to be dependent on the alcohol solvent used for the sol-gel synthesis. Nafion-silica hybrids with homogeneous distribution of the inorganic phase were obtained using methanol as the solvent for the sol-gel reaction. The observed microstructural properties of the Nafion-silica membranes were related to enhanced proton conductivity at high temperatures and low relative humidity conditions.

  17. Nature of proton dynamics in a polymer electrolyte membrane, nafion: a first-principles molecular dynamics study.

    PubMed

    Choe, Yoong-Kee; Tsuchida, Eiji; Ikeshoji, Tamio; Yamakawa, Shunsuke; Hyodo, Shi-Aki

    2009-05-28

    First-principles molecular dynamics simulations have been carried out to investigate the nature of proton dynamics in Nafion, a representative polymer electrolyte membrane (PEM) widely used in PEM fuel cells. From the trajectories of the simulations, diffusion coefficients for the protonic defects were calculated to be 0.3 x 10(-5) cm(2) s(-1) and 7.1 x 10(-5) cm(2) s(-1) for lambda = 4.25 and 12.75, respectively, where lambda denotes hydration levels inside Nafion defined as a number of water molecules per sulfonic group. Our simulations show that proton hopping probability does not depend much on the water content inside Nafion. This finding indicates that the classical vehicular (or en masse) diffusion model, which has been employed to account for the slow diffusion process of protons in low water-content Nafion, is an oversimplification and does not correctly describe proton dynamics. Furthermore, it is found that difference in the value of the proton diffusion coefficient with respect to water content inside Nafion is related to the different character of proton hopping occurring in the water hydrogen bond network. When the water content is low, the proton hopping occurs in a manner that does not contribute constructively to proton mobility, while when the water content is high, it occurs in a manner which is beneficial to overall proton mobility. Such a different nature of proton hoppings arises mainly from the difference in the connectivity of water hydrogen bond network. Our results broadly support earlier simulation studies and provide the molecular level origin of properties arising from the proton dynamics in Nafion.

  18. Large-scale atomistic and quantum-mechanical simulations of a Nafion membrane: Morphology, proton solvation and charge transport

    PubMed Central

    Komarov, Pavel V; Khokhlov, Alexei R

    2013-01-01

    Summary Atomistic and first-principles molecular dynamics simulations are employed to investigate the structure formation in a hydrated Nafion membrane and the solvation and transport of protons in the water channel of the membrane. For the water/Nafion systems containing more than 4 million atoms, it is found that the observed microphase-segregated morphology can be classified as bicontinuous: both majority (hydrophobic) and minority (hydrophilic) subphases are 3D continuous and organized in an irregular ordered pattern, which is largely similar to that known for a bicontinuous double-diamond structure. The characteristic size of the connected hydrophilic channels is about 25–50 Å, depending on the water content. A thermodynamic decomposition of the potential of mean force and the calculated spectral densities of the hindered translational motions of cations reveal that ion association observed with decreasing temperature is largely an entropic effect related to the loss of low-frequency modes. Based on the results from the atomistic simulation of the morphology of Nafion, we developed a realistic model of ion-conducting hydrophilic channel within the Nafion membrane and studied it with quantum molecular dynamics. The extensive 120 ps-long density functional theory (DFT)-based simulations of charge migration in the 1200-atom model of the nanochannel consisting of Nafion chains and water molecules allowed us to observe the bimodality of the van Hove autocorrelation function, which provides the direct evidence of the Grotthuss bond-exchange (hopping) mechanism as a significant contributor to the proton conductivity. PMID:24205452

  19. Water Dynamics in Nafion Fuel Cell Membranes: the Effects of Confinement and Structural Changes on the Hydrogen Bond Network.

    PubMed

    Moilanen, David E; Piletic, Ivan R; Fayer, Michael D

    2007-01-01

    The complex environments experienced by water molecules in the hydrophilic channels of Nafion membranes are studied by ultrafast infrared pump-probe spectroscopy. A wavelength dependent study of the vibrational lifetime of the O-D stretch of dilute HOD in H(2)O confined in Nafion membranes provides evidence of two distinct ensembles of water molecules. While only two ensembles are present at each level of membrane hydration studied, the characteristics of the two ensembles change as the water content of the membrane changes. Time dependent anisotropy measurements show that the orientational motions of water molecules in Nafion membranes are significantly slower than in bulk water and that lower hydration levels result in slower orientational relaxation. Initial wavelength dependent results for the anisotropy show no clear variation in the time scale for orientational motion across a broad range of frequencies. The anisotropy decay is analyzed using a model based on restricted orientational diffusion within a hydrogen bond configuration followed by total reorientation through jump diffusion.

  20. Characterization of the thermolysis products of Nafion membrane: A potential source of perfluorinated compounds in the environment

    NASA Astrophysics Data System (ADS)

    Feng, Mingbao; Qu, Ruijuan; Wei, Zhongbo; Wang, Liansheng; Sun, Ping; Wang, Zunyao

    2015-05-01

    The thermal decomposition of Nafion N117 membrane, a typical perfluorosulfonic acid membrane that is widely used in various chemical technologies, was investigated in this study. Structural identification of thermolysis products in water and methanol was performed using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS). The fluoride release was studied using an ion-chromatography system, and the membrane thermal stability was characterized by thermogravimetric analysis. Notably, several types of perfluorinated compounds (PFCs) including perfluorocarboxylic acids were detected and identified. Based on these data, a thermolysis mechanism was proposed involving cleavage of both the polymer backbone and its side chains by attack of radical species. This is the first systematic report on the thermolysis products of Nafion by simulating its high-temperature operation and disposal process via incineration. The results of this study indicate that Nafion is a potential environmental source of PFCs, which have attracted growing interest and concern in recent years. Additionally, this study provides an analytical justification of the LC/ESI-MS/MS method for characterizing the degradation products of polymer electrolyte membranes. These identifications can substantially facilitate an understanding of their decomposition mechanisms and offer insight into the proper utilization and effective management on these membranes.

  1. Characterization of the thermolysis products of Nafion membrane: A potential source of perfluorinated compounds in the environment

    PubMed Central

    Feng, Mingbao; Qu, Ruijuan; Wei, Zhongbo; Wang, Liansheng; Sun, Ping; Wang, Zunyao

    2015-01-01

    The thermal decomposition of Nafion N117 membrane, a typical perfluorosulfonic acid membrane that is widely used in various chemical technologies, was investigated in this study. Structural identification of thermolysis products in water and methanol was performed using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS). The fluoride release was studied using an ion-chromatography system, and the membrane thermal stability was characterized by thermogravimetric analysis. Notably, several types of perfluorinated compounds (PFCs) including perfluorocarboxylic acids were detected and identified. Based on these data, a thermolysis mechanism was proposed involving cleavage of both the polymer backbone and its side chains by attack of radical species. This is the first systematic report on the thermolysis products of Nafion by simulating its high-temperature operation and disposal process via incineration. The results of this study indicate that Nafion is a potential environmental source of PFCs, which have attracted growing interest and concern in recent years. Additionally, this study provides an analytical justification of the LC/ESI-MS/MS method for characterizing the degradation products of polymer electrolyte membranes. These identifications can substantially facilitate an understanding of their decomposition mechanisms and offer insight into the proper utilization and effective management on these membranes. PMID:25947254

  2. Characterization of the thermolysis products of Nafion membrane: A potential source of perfluorinated compounds in the environment.

    PubMed

    Feng, Mingbao; Qu, Ruijuan; Wei, Zhongbo; Wang, Liansheng; Sun, Ping; Wang, Zunyao

    2015-05-07

    The thermal decomposition of Nafion N117 membrane, a typical perfluorosulfonic acid membrane that is widely used in various chemical technologies, was investigated in this study. Structural identification of thermolysis products in water and methanol was performed using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS). The fluoride release was studied using an ion-chromatography system, and the membrane thermal stability was characterized by thermogravimetric analysis. Notably, several types of perfluorinated compounds (PFCs) including perfluorocarboxylic acids were detected and identified. Based on these data, a thermolysis mechanism was proposed involving cleavage of both the polymer backbone and its side chains by attack of radical species. This is the first systematic report on the thermolysis products of Nafion by simulating its high-temperature operation and disposal process via incineration. The results of this study indicate that Nafion is a potential environmental source of PFCs, which have attracted growing interest and concern in recent years. Additionally, this study provides an analytical justification of the LC/ESI-MS/MS method for characterizing the degradation products of polymer electrolyte membranes. These identifications can substantially facilitate an understanding of their decomposition mechanisms and offer insight into the proper utilization and effective management on these membranes.

  3. Determination of morphine at gold nanoparticles/Nafion® carbon paste modified sensor electrode.

    PubMed

    Atta, Nada F; Galal, Ahmed; Azab, Shereen M

    2011-11-21

    A novel and effective electrochemical sensor for the determination of morphine (MO) in 0.04 mol L(-1) universal buffer solution (pH 7.4) is introduced using gold nanoparticles electrodeposited on a Nafion modified carbon paste electrode. The effect of various experimental parameters including pH, scan rate and accumulation time on the voltammetric response of MO was investigated. At the optimum conditions, the concentration of MO was determined using differential pulse voltammetry (DPV) in a linear range of 2.0 × 10(-7) to 2.6 × 10(-4) mol L(-1) with a correlation coefficient of 0.999, and a detection limit of 13.3 × 10(-10) mol L(-1), respectively. The effect of common interferences on the current response of morphine namely ascorbic acid (AA) and uric acid (UA) is studied. The modified electrode can be used for the determination of MO spiked into urine samples, and excellent recovery results were obtained.

  4. Hepatic Transcriptome Responses in Mice (Mus musculus) Exposed to the Nafion Membrane and Its Combustion Products

    PubMed Central

    Feng, Mingbao; Qu, Ruijuan; Habteselassie, Mussie; Wu, Jun; Yang, Shaogui; Sun, Ping; Huang, Qingguo; Wang, Zunyao

    2015-01-01

    Nafion 117 membrane (N117), an important polymer electrolyte membrane (PEM), has been widely used for numerous chemical technologies. Despite its increasing production and use, the toxicity data for N117 and its combustion products remain lacking. Toxicity studies are necessary to avoid problems related to waste disposal in landfills and incineration that may arise. In this study, we investigated the histopathological alterations, oxidative stress biomarker responses, and transcriptome profiles in the liver of male mice exposed to N117 and its combustion products for 24 days. An ion-chromatography system and liquid chromatography system coupled to a hybrid quadrupole time-of-flight mass spectrometry were used to analyze the chemical compositions of these combustion products. The transcriptomics analysis identified several significantly altered molecular pathways, including the metabolism of xenobiotics, carbohydrates and lipids; signal transduction; cellular processes; immune system; and signaling molecules and interaction. These studies provide preliminary data for the potential toxicity of N117 and its combustion products on living organisms and may fill the information gaps in the toxicity databases for the currently used PEMs. PMID:26057616

  5. Retarding of electrochemical oxidation of formate on the platinum anode by a coat of Nafion membrane

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Lv, Weixin; Li, Guanghua; Mezaal, Mohammed Adnan; Li, Xiaojing; Lei, Lixu

    2014-12-01

    It has been found that the faradaic efficiency is decreasing with the electrolysis time for electrochemical reduction of CO2 to formate on a Sn cathode with a Pt anode in an undivided electrolytic cell, because the oxidation of formed formate takes place on the Pt anode, which also limits seriously the highest concentration of formate in the system. Here, we report that a coat of Nafion membrane on the Pt anode can retard the oxidation of formate: even if the concentration of the formate in the electrolyte reaches to 0.12 mol L-1, the faradaic efficiency still maintains above 61.3%; in contrast, the oxidation reaction of the formate on the naked Pt electrode is very fast, when the concentration of the formate in the electrolyte reaches to 0.023 mol L-1, the faradaic efficiency decreases to 35.3%. This is very important because the separation of formic acid could not be economical when its concentration is not high enough, and it is also costly if the depleted solution allows too less of its concentration because the solution has to be reused in the electrochemical process.

  6. Highly selective dopamine electrochemical sensor based on electrochemically pretreated graphite and nafion composite modified screen printed carbon electrode.

    PubMed

    Ku, Shuhao; Palanisamy, Selvakumar; Chen, Shen-Ming

    2013-12-01

    Herein, we report a highly selective dopamine electrochemical sensor based on electrochemically pretreated graphite/nafion composite modified screen printed carbon (SPC) electrode. Electrochemically activated graphite/nafion composite was prepared by using a simple electrochemical method. Scanning electron microscope (SEM) used to characterize the surface morphology of the fabricated composite electrode. The SEM result clearly indicates that the graphitic basal planes were totally disturbed and leads to the formation of graphite nanosheets. The composite modified electrode showed an enhanced electrocatalytic activity toward the oxidation of DA when compared with either electrochemical pretreated graphite or nafion SPC electrodes. The fabricated composite electrode exhibits a good electrocatalytic oxidation toward DA in the linear response range from 0.5 to 70 μM with the detection limit of 0.023 μM. The proposed sensor also exhibits very good selectivity and stability, with the appreciable sensitivity. In addition, the proposed sensor showed satisfactory recovery results toward the commercial pharmaceutical DA samples. Copyright © 2013 Elsevier Inc. All rights reserved.

  7. Voltammetric determination of In3+ based on the bifunctionality of a multi-walled carbon nanotubes-nafion modified electrode.

    PubMed

    Li, Junhua; Zhang, Fuxing; Wang, Jianqiu; Xu, Zhifeng; Zeng, Rongying

    2009-05-01

    Due to the strong cation-exchange ability of Nafion and the excellent properties of multi-walled carbon nanotubes (MWCNTs), a highly sensitive and mercury-free method of determining trace levels of In(3+) has been established based on the bifunctionality of a MWCNTs/Nafion modified glassy carbon electrode (GCE). The MWCNTs/Nafion modified GCE detects In(3+) in a 0.01 M HAc-NaAc buffer solution at pH 5.0 using anodic stripping voltammetry (ASV). The experimental results suggest that a sensitive anodic stripping peak appears at -0.58 V on anodic stripping voltammograms, which can be used as an analytical signal for the determination of In(3+). A good linear relationship between the stripping peak currents and the In(3+) concentration is obtained, covering the concentration range from 5.0 x 10(-10) to 2.0 x 10(-7) M, with a correlation coefficient of 0.999; the detection limit is 1.0 x 10(-11) M. This proposed method has been applied to detect In(3+) as a new way.

  8. A comparison study of ionic polymer-metal composites (IPMCs) fabricated with Nafion and other ion exchange membranes

    NASA Astrophysics Data System (ADS)

    Park, Jiyeon; Palmre, Viljar; Kim, Kwang; Shin, Dongsuk; Kim, Daniel H.; Yim, Woosoon; Bae, Chulsung

    2013-04-01

    Ionic polymer-metal composites (IPMCs) have been and still are one of the best candidates with great potential to be used as actuators and sensors particularly in bioengineering where the environmental conditions are in an aqueous medium. Each component of an IPMC is important. However, the ion exchange membrane should be more emphasized because it is where ions migrate when electrical stimulation is applied and eventually it produces deformation of the IPMC. So far, the most commonly used ion exchange membrane is Nafion and many studies have been conducted with it for IPMC applications. There are a number of other commercially available ion exchange membranes now, but only a few studies have been done on those membranes to be used in IPMC applications. In this study, four commercially available membranes, (1) Nafion N115 (DuPont), (2) CMI7000S (Membranes International Inc.), (3) F-14100 (fumatech), (4) GEFC-700 (Golden Energy Fuel Cell) were selected and fabricated in IPMCs and their potentials as actuators were examined by conducting various characterizations such as water uptake, ion exchange capacity, SEM, DSC, blocking force and bending displacement.

  9. Preparation and characterization of water-soluble carbon nanotube reinforced Nafion membranes and so-based ionic polymer metal composite actuators

    NASA Astrophysics Data System (ADS)

    Ru, Jie; Wang, Yanjie; Chang, Longfei; Chen, Hualing; Li, Dichen

    2016-09-01

    In this paper, we developed a new kind of ionic polymer metal composite (IPMC) actuator by doping water-soluble sulfonated multi-walled carbon nanotube (sMWCNT) into Nafion matrix to overcome some major drawbacks of traditional IPMCs, such as relatively low bending deformation and carring capacity at low driving voltages. Firstly, sMWCNT was synthesized via diazotization coupling reaction, and then doped into Nafion matrix by casting method. Subsequently, the electrochemical and electromechanical properties of sMWCNT-reinforced Nafion membranes and the corresponding IPMCs were investigated. Finally, the effects of sMWCNT on the performances of IPMCs were evaluated and analyzed systematacially. The results showed that sMWCNT was homogeneously dispersed in Nafion matrix without any entangled structure or obvious agglomeration. The main factors for superior actuation performances, like water-uptake ratio, proton conductivity and elastic modulus, increased significantly. Compared to the pure Nafion IPMC and MWCNT/Nafion IPMC, much superior electrochemical and electromechanical performances were achieved in the sMWCNT/Nafion IPMC, which were attributed to the numerous insertion sites, high surface conductivity and excellent mechanical strength as well as the homogeneous dispersity of the incorporated sMWCNT. Herein, a trace amount of sMWCNT can improve the performances of IPMCs significantly for realistic applications.

  10. Controlled morphology of Nafion^ perflourinated ionomer membrane and poly(vinylidene-co-trifluoroethylene) blends for swelling suppression.

    NASA Astrophysics Data System (ADS)

    Nazir, Nadzrinahamin Ahmad; Kyu, Thein

    2009-03-01

    The major objective of the present study is concerned with the swelling suppression of Nafion^ membrane upon hydration through blending with poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) copolymer. The phase diagram of the Nafion/PVDF-TrFE blend was established by differential scanning calorimetry, cloud point measurement, and optical microscopy. A theoretical phase diagram was calculated by self-consistently solving the combined Flory-Huggins free energy for liquid-liquid demixing and the phase field free energy for crystal solidification. The resulting phase diagram is the combined LCST-UCST and/or an hour glass type. Guided by the phase diagram, the phase separated domain morphology can be controlled to exhibit bicontinuous or dispersed domains via phase separation by solvent casting or thermal quenching. The blends thus prepared not only afford suppression of water uptake, but also render dimensional stability. Fourier transform infrared spectroscopy studies and water uptake measurement showed infallible evidence that modification of Nafion^ with PVDF-TrFE reduces swelling upon hydration.

  11. Effect of cation driven loading of dibenzo-18-crown-6 in Nafion-117 membrane on the diffusion and transport behavior of alkali metal ions.

    PubMed

    Bhattacharyya, A; Goswami, A

    2009-10-01

    The possibility of enhancing the selectivity to separate the alkali metal ions was studied by loading dibenzo-18-crown-6 (DB18C6) in Li(+), Na(+), K(+), and Cs(+) form of cation exchange membrane, Nafion-117 (M-Naf-Cr where M = Li, Na, K, and Cs). DB18C6 was incorporated in Nafion-117 in corresponding ionic forms. Presence of DB18C6 in Nafion-117 was confirmed by FTIR. Self-diffusion and ion exchange kinetics of the alkali metal ions were studied in these membranes. It was observed that the diffusion in the membrane slowed down drastically from Li(+) to all other monovalent alkali metal ions. Two compartment cell experiments were done with DB18C6 loaded Cs(+)- form of Nafion-117 (Cs-Naf-Cr) membrane to study the transport of Na(+) and Cs(+) ions. No transport of ions was observed. When the same experiment were performed by replacing Li(+) of Li-Naf-Cr with Cs(+) (Cs-Li-Naf-Cr), transport of Cs(+) and H(+) were observed at much faster time scale compared to Cs-Naf-Cr. The selectivity of Cs(+) over Li(+) was enhanced by a factor of about 6 when Li-Naf-Cr was used in place Li(+) form of Nafion-117 for the transport experiments.

  12. Atomistic simulation of water percolation and proton hopping in Nafion fuel cell membrane.

    PubMed

    Devanathan, Ram; Venkatnathan, Arun; Rousseau, Roger; Dupuis, Michel; Frigato, Tomaso; Gu, Wei; Helms, Volkhard

    2010-11-04

    We have performed a detailed analysis of water clustering and percolation in hydrated Nafion configurations generated by classical molecular dynamics simulations. Our results show that at low hydration levels H(2)O molecules are isolated and a continuous hydrogen-bonded network forms as the hydration level is increased. Our quantitative analysis has established a hydration level (λ) between 5 and 6 H(2)O/SO(3)(-) as the percolation threshold of Nafion. We have also examined the effect of such a network on proton transport by studying the structural diffusion of protons using the quantum hopping molecular dynamics method. The mean residence time of the proton on a water molecule decreases by 2 orders of magnitude when the λ value is increased from 5 to 15. The proton diffusion coefficient in Nafion at a λ value of 15 is about 1.1 × 10(-5) cm(2)/s in agreement with experiment. The results provide quantitative atomic-level evidence of water network percolation in Nafion and its effect on proton conductivity.

  13. Atomistic Simulation of Water Percolation and Proton Hopping in Nafion Fuel Cell Membrane

    SciTech Connect

    Devanathan, Ramaswami; Venkatnathan, Arun; Rousseau, Roger J.; Dupuis, Michel; Frigato, Tomaso; Gu, Wei; Helms, Volkhard H.

    2010-11-04

    We have performed a detailed analysis of water clustering and percolation in hydrated Nafion configurations generated by classical molecular dynamics simulations. Our results show that at low hydration levels H2O molecules are isolated and a continuous hydrogen-bonded network forms as the hydration level is increased. Our quantitative analysis has established a hydration level (λ) between 5 and 6 H2O/SO3- as the percolation threshold of Nafion. We have also examined the effect of such a network on proton transport by studying the structural diffusion of protons using the quantum hopping molecular dynamics method. The mean residence time of the proton on a water molecule decreases by two orders of magnitude when the λ value is increased from 5 to 15. The proton diffusion coefficient in Nafion at a λ value of 15 is about 1.1x10-5 cm2/s in agreement with experiment. The results provide quantitative atomic-level evidence of water network percolation in Nafion and its effect on proton conductivity.

  14. Characterization of Polyester Cloth as an Alternative Separator to Nafion Membrane in Microbial Fuel Cells for Bioelectricity Generation Using Swine Wastewater.

    PubMed

    Kim, Taeyoung; Kang, Sukwon; Sung, Je Hoon; Kang, Youn Koo; Kim, Young Hwa; Jang, Jae Kyung

    2016-12-28

    Polyester cloth (PC) was selected as a prospective inexpensive substitute separator material for microbial fuel cells (MFCs). PC was compared with a traditional Nafion proton exchange membrane (PEM) as an MFC separator by analyzing its physical and electrochemical properties. A single layer of PC showed higher mass transfer (e.g., for O₂/H⁺/ions) than the Nafion PEM; in the case of oxygen mass transfer coefficient (ko), a rate of 50.0 × 10⁻⁵ cm·s⁻¹ was observed compared with a rate of 20.8 × 10⁻⁵ cm/s in the Nafion PEM. Increased numbers of PC layers were found to reduce the oxygen mass transfer coefficient. In addition, the diffusion coefficient of oxygen (DO) for PC (2.0-3.3 × 10⁻⁶ cm²/s) was lower than that of the Nafion PEM (3.8 × 10⁻⁶ cm²/s). The PC was found to have a low ohmic resistance (0.29-0.38 Ω) in the MFC, which was similar to that of Nafion PEM (0.31 Ω); this resulted in comparable maximum power density and maximum current density in MFCs with PC and those with Nafion PEMs. Moreover, a higher average current generation was observed in MFCs with PC (104.3 ± 15.3 A/m³) compared with MFCs with Nafion PEM (100.4 ± 17.7 A/m³), as well as showing insignificant degradation of the PC surface, during 177 days of use in swine wastewater. These results suggest that PC separators could serve as a low-cost alternative to Nafion PEMs for construction of cost-effective MFCs.

  15. Enhanced proton conductivity of Nafion hybrid membrane under different humidities by incorporating metal-organic frameworks with high phytic acid loading.

    PubMed

    Li, Zhen; He, Guangwei; Zhang, Bei; Cao, Ying; Wu, Hong; Jiang, Zhongyi; Tiantian, Zhou

    2014-06-25

    In this study, phytic acid (myo-inositol hexaphosphonic acid) was first immobilized by MIL101 via vacuum-assisted impregnation method. The obtained phytic@MIL101 was then utilized as a novel filler to incorporate into Nafion to fabricate hybrid proton exchange membrane for application in PEMFC under different relative humidities (RHs), especially under low RHs. High loading and uniform dispersion of phytic acid in MIL 101(Cr) were achieved as demonstrated by ICP, FT-IR, XPS, and EDS-mapping. The phytic@MIL101 was dispersed homogeneously in the Nafion matrix when the filler content was less than 12%. Hybrid membranes were evaluated by proton conductivity, mechanical property, thermal stability, and so forth. Remarkably, the Nafion/phytic@MIL hybrid membranes showed high proton conductivity at different RHs, especially under low RHs, which was up to 0.0608 S cm(-1) and 7.63 × 10(-4) S cm(-1) at 57.4% RH and 10.5% RH (2.8 and 11.0 times higher than that of pristine membrane), respectively. Moreover, the mechanical property of Nafion/phtic@MIL hybrid membranes was substantially enhanced and the thermal stability of membranes was well preserved.

  16. Voltammetric determination of ferulic acid by didodecyldimethylammonium bromide/nafion composite film-modified carbon paste electrode.

    PubMed

    Luo, Liqiang; Wang, Xia; Li, Qiuxia; Ding, Yaping; Jia, Jianbo; Deng, Dongmei

    2010-01-01

    A simple and rapid method for the determination of ferulic acid in pharmaceutical formulations by didodecyldimethylammonium bromide (DDAB)/Nafion composite film-modified carbon paste electrode is presented. The electrochemical behavior of ferulic acid at the proposed electrode was investigated by cyclic voltammetry and a well-defined oxidation peak was observed at +0.44 V versus saturated calomel electrode in 0.1 M acetate buffer (pH 5.5) solutions. Some experimental parameters affecting the electrochemical response of the modified electrode were optimized. Under optimal conditions, the oxidation peak currents of ferulic acid increase linearly with the concentration of ferulic acid in the range from 2.0 x 10(-6) to 1.2 x 10(-4) M with a detection limit of 3.9 x 10(-7) M (S/N = 3). The proposed method was successfully applied to the determination of ferulic acid in pharmaceutical tablets.

  17. Theoretical study on the electrochemical behavior of norepinephrine at Nafion multi-walled carbon nanotubes modified pyrolytic graphite electrode

    NASA Astrophysics Data System (ADS)

    Song, Yuanzhi

    2007-08-01

    DFT-B3LYP/6-31G (d, p) and HF/6-31G (d, p) calculations are performed for deoxidized norepinephrineat (NP (R)) and its oxidized form (NP (O)). The electrochemistry of norepinephrineat (NP) was studied by cyclic voltammetry (CV) at a pyrolytic graphite electrode modified by Nafion multi-walled carbon nanotubes (MWNTs) in phosphate buffers at pH 6.0, showing that the standard electrode potential of half reaction for NP (O), H +/NP (R) is 0.75l V. This experimental standard electrode potential of half reaction is consistent with that calculated using the energies of solvation and sum of electronic and thermal free energies of NP (R) and NP (O). The frontier orbital theory and Mülliken charges of moleculer explain the electrochemical behavior of CV at modified electrode well. The singlet vertical excited states for NP (R) and NP (O) are also discussed.

  18. Adsorption stripping voltammetry of phenol at Nafion-modified glassy carbon electrode in the presence of surfactants.

    PubMed

    Yi, H; Wu, K; Hu, S; Cui, D

    2001-12-24

    In this paper, a new voltammetric method for the determination of phenol is described. In pH 8.00 phosphate buffer and in the presence of long-chain cationic surfactant-cetyltrimethylammonium bromide-phenol has a very sensitive oxidation peak at 0.47 V (vs. SCE) on the Nafion-modified glassy carbon electrode (GCE). The experimental parameters, such as supporting electrolyte and pH values, amounts of Nafion, varieties and concentration of surfactants, accumulation potential and time, as well as scan rate were optimized. The peak current is linear with the concentration of phenol in the range from 8x10(-9) to 1x10(-5) M, and the detection limit is 1x10(-9) M after being accumulated at -0.50 V (vs. SCE) for 3 min. Trace levels of phenol in water samples were determined by using this voltammetric method, the average recovery was calculated to be 99.56%.

  19. Nafion-Modified PEDOT:PSS as a Transparent Hole-Transporting Layer for High-Performance Crystalline-Si/Organic Heterojunction Solar Cells with Improved Light Soaking Stability.

    PubMed

    Hossain, Jaker; Liu, Qiming; Miura, Takuya; Kasahara, Koji; Harada, Daisuke; Ishikawa, Ryo; Ueno, Keiji; Shirai, Hajime

    2016-11-23

    We demonstrate the chemistry of amphiphilic perfluorosulfonic copolymer Nafion-coated conductive poly(3,4-ethyelenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and its effect on the photovoltaic performance of PEDOT:PSS/crystalline Si (c-Si) heterojunction solar cells. The highly hydrophilic sulfonate group of insulating, chemically stable Nafion interacts with PSS in PEDOT:PSS, which reduce the Coulombic interaction between PEDOT and PSS. The highly hydrophobic fluorocarbon backbone of Nafion favorably interacts with hydrophobic PEDOT of PEDOT:PSS. These factors give rise to the extension of π-conjugation of PEDOT chains. Silver paste used as a top grid electrode diffused into the Nafion layer and contacted with underneath Nafion-modified PEDOT:PSS layer. As a consequent, solution-processed Nafion-coated PEDOT:PSS/c-Si heterojunction solar cells exhibited a higher power conversion efficiency of 14.0% with better stability for light soaking rather than that of the pristine PEDOT:PSS/c-Si device by adjusting the layer thickness of Nafion. These findings originate from the chemical stability of hydrophobic fluorocarbon backbone of Nafion, diffusivity of silver paste into Nafion and contact with PEDOT:PSS, and Nafion as an antireflection layer.

  20. Nafion-assisted cross-linking of sulfonated poly(arylene ether ketone) bearing carboxylic acid groups and their composite membranes for fuel cells

    NASA Astrophysics Data System (ADS)

    Lin, Haidan; Zhao, Chengji; Na, Hui

    In this study, a new type of cross-linked composite membrane is prepared and considered for its potential applications in direct methanol fuel cell. Nafion and sulfonated poly(arylene ether ketone) bearing carboxylic acid groups (SPAEK-C) are blended and subsequently cross-linked by a Friedel-Craft reaction using the carboxylic acid groups in the SPAEK-C to achieve lower methanol permeability. The perfluoroalkyl sulfonic acid groups of Nafion act as a benign solid catalyst, which assist the cross-linking of SPAEK-C. The physical and chemical characterizations of the cross-linked composite membranes are performed by varying the contents of SPAEK-C. The c-Nafion-15% membrane exhibits appropriate water uptake (10.49-25.22%), low methanol permeability (2.57 × 10 -7 cm 2 s -1), and high proton conductivity (0.179 S cm -1 at 80 °C). DSC and FTIR analyze suggest the cross-linking reaction. These results show that the self-cross-linking of SPAEK-C in the Nafion membrane can effectively reduce methanol permeability while maintaining high proton conductivity.

  1. Electrochemical behavior and voltammetric determination of 2,4,6-triaminopyrimidine at glassy carbon electrode modified with multi-walled carbon nanotubes/nafion.

    PubMed

    Yang, Baocheng; Wang, Fei; Guo, Sujuan; Ye, Baoxian

    2010-01-01

    A multi-wall carbon nanotubes (MWCNTs) composite with Nafion was modified on a glass carbon electrode. The modified electrode was then used as a voltammetric sensor in detecting 2,4,6-triaminopyrimidine (TAP). The surface morphology of the Nafion/MWCNTs composite film was characterized by atomic force microscopy (AFM), and the electrochemical behavior of TAP at this sensor was investigated in detail. The results indicated that the Nafion/MWCNTs modified electrode exhibited efficient electrocatalytic oxidation for TAP with relatively high sensitivity, stability and lifetime. Under the optimized condition using linear sweep voltammetry (LSV), the Nafion/MWCNTs modified electrode exhibited a linear voltammetric response for TAP in the concentration range of 2.0 × 10(-7) to 3.6 × 10(-5) mol L(-1), with a detection limit of 5.0 × 10(-8) mol L(-1). The electrode was applied to detect TAP added to human blood serum, with an average recovery value of 101.3%.

  2. Membrane-derived fluorinated radicals detected by electron spin resonance in UV-irradiated Nafion and Dow ionomers: effect of counterions and H2O2.

    PubMed

    Kadirov, Marsil K; Bosnjakovic, Admira; Schlick, Shulamith

    2005-04-28

    Electron spin resonance (ESR) spectroscopy was used to detect and identify radicals formed by UV irradiation of Nafion and Dow perfluorinated membranes partially or fully neutralized by Cu(II), Fe(II), and Fe(III). This method allowed the monitoring of ESR signals from the paramagnetic counterions together with the appearance of membrane-derived radical species. The most surprising aspect of this study was the formation of membrane-derived radical species only in the neutralized membranes, and even in the absence of H2O2 in the case of Nafion/Cu(II) and Nafion/Fe(III). In Nafion/Cu(II), ESR spectra from radicals exhibiting hyperfine interactions with three equivalent 19F nuclei (the "quartet") and with four equivalent 19F nuclei (the "quintet") were detected. In Nafion/Fe(II) exposed to H2O2 solutions, the formation of Fe(III) was detected. Upon UV irradiation, strong signals from the chain-end radical ROCF2CF2* were detected first, followed by the appearance, upon annealing above 200 K, of the quartet signal observed in Nafion/Cu(II). In subsequent experiments with Nafion and Dow membranes neutralized by Fe(III), the ROCF2CF2* radicals were formed even in the absence of H2O2, indicating that the role of H2O2 is oxidation of Fe(II) to Fe(III); moreover, in these systems small amounts of the chain-end radicals were detected even without UV irradiation. This result validates the method used to form the radicals: the role of UV irradiation is to accelerate the formation of a signal that is produced, albeit slowly, even in the dark, and possibly during fuel cell operation. The major conclusion is that cations are involved in degradation processes; the point of attack appears to be at or near the pendant chain of the ionomer. Therefore when studying membrane stability, it is important to consider not only the formation of oxygen radicals, such as HO*, HOO*, and O2*-, that can attack the membrane but also the specific reactivity of counterions.

  3. Electrochemical Detection of p-Aminophenol by Flexible Devices Based on Multi-Wall Carbon Nanotubes Dispersed in Electrochemically Modified Nafion

    PubMed Central

    Scandurra, Graziella; Antonella, Arena; Ciofi, Carmine; Saitta, Gaetano; Lanza, Maurizio

    2014-01-01

    A conducting composite prepared by dispersing multi-walled carbon nanotubes (MWCNTs) into a host matrix consisting of Nafion, electrochemically doped with copper, has been prepared, characterized and used to modify one of the gold electrodes of simply designed electrochemical cells having copier grade transparency sheets as substrates. Electrical measurements performed in deionized water show that the Au/Nafion/Au-MWCNTs–Nafion:Cu cells can be successfully used in order to detect the presence of p-aminophenol (PAP) in water, without the need for any supporting electrolyte. The intensity of the redox peaks arising when PAP is added to deionized water is found to be linearly related to the analyte in the range from 0.2 to 1.6 μM, with a detection limit of 90 nM and a sensitivity of 7 μA·(μM−1)·cm−2. PMID:24854357

  4. Electrochemical detection of p-aminophenol by flexible devices based on multi-wall carbon nanotubes dispersed in electrochemically modified Nafion.

    PubMed

    Scandurra, Graziella; Antonella, Arena; Ciofi, Carmine; Saitta, Gaetano; Lanza, Maurizio

    2014-05-21

    A conducting composite prepared by dispersing multi-walled carbon nanotubes (MWCNTs) into a host matrix consisting of Nafion, electrochemically doped with copper, has been prepared, characterized and used to modify one of the gold electrodes of simply designed electrochemical cells having copier grade transparency sheets as substrates. Electrical measurements performed in deionized water show that the Au/Nafion/Au-MWCNTs-Nafion:Cu cells can be successfully used in order to detect the presence of p-aminophenol (PAP) in water, without the need for any supporting electrolyte. The intensity of the redox peaks arising when PAP is added to deionized water is found to be linearly related to the analyte in the range from 0.2 to 1.6 µM, with a detection limit of 90 nM and a sensitivity of 7 µA·(µM(-1))·cm(-2).

  5. The Application of Nafion Metal Catalyst Free Carbon Nanotube Modified Gold Electrode: Voltammetric Zinc Detection in Serum

    PubMed Central

    Yue, Wei; Bange, Adam; Riehl, Bill L.; Johnson, Jay M.; Papautsky, Ian; Heineman, William R.

    2013-01-01

    Metal catalyst free carbon nanotube (MCFCNT) whiskers were first used as an electrode modification material on a gold electrode surface for zinc voltammetric measurements. A composite film of Nafion and MCFCNT whiskers was applied to a gold electrode surface to form a mechanically stable sensor. The sensor was then used for zinc detection in both acetate buffer solution and extracted bovine serum solution. A limit of detection of 53 nM was achieved for a 120 s deposition time. The zinc in bovine serum was extracted via a double extraction procedure using dithizone in chloroform as a zinc chelating ligand. The modified electrode was found to be both reliable and sensitive for zinc measurements in both matrices. PMID:24436574

  6. Optimization of a Nafion Membrane-Based System for Removal of Chloride and Fluoride from Lunar Regolith-Derived Water

    NASA Technical Reports Server (NTRS)

    Anthony, Stephen M.; Santiago-Maldonado, Edgardo; Captain, James G.; Pawate, Ashtamurthy S.; Kenis, Paul J. A.

    2012-01-01

    A long-term human presence in space will require self-sustaining systems capable of producing oxygen and potable water from extraterrestrial sources. Oxygen can be extracted from lunar regolith, and water contaminated with hydrochloric and hydrofluoric acids is produced as an intermediate in this process. We investigated the ability of Nafion proton exchange membranes to remove hydrochloric and hydrofluoric acids from water. The effect of membrane thickness, product stream flow rate, and acid solution temperature and concentration on water flux, acid rejection, and water and acid activity were studied. The conditions that maximized water transport and acid rejection while minimizing resource usage were determined by calculating a figure of merit. Water permeation is highest at high solution temperature and product stream flow rate across thin membranes, while chloride and fluoride permeation are lowest at low acid solution temperature and concentration across thin membranes. The figure of merit varies depending on the starting acid concentration; at low concentration, the figure of merit is highest across a thin membrane, while at high concentration, the figure of merit is highest at low solution temperature. In all cases, the figure of merit increases with increasing product stream flow rate.

  7. Determination of Dopamine in the Presence of Ascorbic Acid by Nafion and Single-Walled Carbon Nanotube Film Modified on Carbon Fiber Microelectrode

    PubMed Central

    Jeong, Haesang; Jeon, Seungwon

    2008-01-01

    Carbon fiber microelectrode (CFME) modified by Nafion and single-walled carbon nanotubes (SWNTs) was studied by voltammetric methods in phosphate buffer saline (PBS) solution at pH 7.4. The Nafion-SWNTs/CFME modified microelectrode exhibited strongly enhanced voltammetric sensitivity and selectivity towards dopamine (DA) determination in the presence of ascorbic acid (AA). Nafion-SWNTs film accelerated the electron transfer reaction of DA, but Nafion film as a negatively charged polymer restrained the electrochemical response of AA. Voltammetric techniques separated the anodic peaks of DA and AA, and the interference from AA was effectively excluded from DA determination. Linear calibration plots were obtained in the DA concentration range of 10 nM - 10 μM and the detection limit of the anodic current was determined to be 5 nM at a signal-to-noise ratio of 3. The study results demonstrate that DA can be determined without any interference from AA at the modified microelectrode, thereby increasing the sensitivity, selectivity, and reproducibility and stability. PMID:27873906

  8. Investigation of Free-Standing Plasmonic Mesoporous Ag/CMK-8-Nafion Composite Membrane for the Removal of Organic Pollutants with 254-nm UV Irradiation

    NASA Astrophysics Data System (ADS)

    Tseng, Chuan Ming; Chen, Hsin Liang; Lai, Sz Nian; Chen, Ming Shiung; Peng, Chien Jung; Li, Chia Jui; Hung, Wei Hsuan

    2017-05-01

    "Carbon-based material" has demonstrated a great potential on water purification due to its strong physical adsorption to organic pollutants in the water. Three-dimensional cubic ordered mesoporous carbon (CMK-8), one of the well-known ordered mesoporous carbons, was prepared by using nanocasting method with mesoporous silica (KIT-6) as the template. In this study, CMK-8 blended with Nafion polymer to form a free-standing mesoporous CMK-8-Nafion composite membrane. The synthesis of high crystallinity CMK-8 was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). More than 80% methyl orange (MO) removal efficiency was observed under 254-nm UV irradiation after 120 min. Ninety-two percent recycling performance was remained after four recycling tests, which indicated a reliable servicing lifetime for the water purification. Furthermore, an additional layer of plasmonic silver nanoparticles (Ag NPs) was integrated into this CMK-8-Nafion membrane for higher pollutant removal efficiency, attributing from the generation of plasmon-resonance hot electrons from Ag NPs. A 4-in. CMK-8-Nafion composite membrane was also fabricated for the demonstration of potential large-scale utilization.

  9. Investigation of Free-Standing Plasmonic Mesoporous Ag/CMK-8-Nafion Composite Membrane for the Removal of Organic Pollutants with 254-nm UV Irradiation.

    PubMed

    Tseng, Chuan Ming; Chen, Hsin Liang; Lai, Sz Nian; Chen, Ming Shiung; Peng, Chien Jung; Li, Chia Jui; Hung, Wei Hsuan

    2017-12-01

    "Carbon-based material" has demonstrated a great potential on water purification due to its strong physical adsorption to organic pollutants in the water. Three-dimensional cubic ordered mesoporous carbon (CMK-8), one of the well-known ordered mesoporous carbons, was prepared by using nanocasting method with mesoporous silica (KIT-6) as the template. In this study, CMK-8 blended with Nafion polymer to form a free-standing mesoporous CMK-8-Nafion composite membrane. The synthesis of high crystallinity CMK-8 was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). More than 80% methyl orange (MO) removal efficiency was observed under 254-nm UV irradiation after 120 min. Ninety-two percent recycling performance was remained after four recycling tests, which indicated a reliable servicing lifetime for the water purification. Furthermore, an additional layer of plasmonic silver nanoparticles (Ag NPs) was integrated into this CMK-8-Nafion membrane for higher pollutant removal efficiency, attributing from the generation of plasmon-resonance hot electrons from Ag NPs. A 4-in. CMK-8-Nafion composite membrane was also fabricated for the demonstration of potential large-scale utilization.

  10. Molecular modeling of the morphology and transport properties of two direct methanol fuel cell membranes: phenylated sulfonated poly(ether ether ketone ketone) versus Nafion

    SciTech Connect

    Devanathan, Ramaswami; Idupulapati, Nagesh B.; Dupuis, Michel

    2012-08-14

    We have used molecular dynamics simulations to examine membrane morphology and the transport of water, methanol and hydronium in phenylated sulfonated poly ether ether ketone ketone (Ph-SPEEKK) and Nafion membranes at 360 K for a range of hydration levels. At comparable hydration levels, the pore diameter is smaller, the sulfonate groups are more closely packed, the hydronium ions are more strongly bound to sulfonate groups, and the diffusion of water and hydronium is slower in Ph-SPEEKK relative to the corresponding properties in Nafion. The aromatic carbon backbone of Ph-SPEEKK is less hydrophobic than the fluorocarbon backbone of Nafion. Water network percolation occurs at a hydration level ({lambda}) of {approx}8 H{sub 2}O/SO{sub 3}{sup -}. At {lambda} = 20, water, methanol and hydronium diffusion coefficients were 1.4 x 10{sup -5}, 0.6 x 10{sup -5} and 0.2 x 10{sup -5} cm{sup 2}/s, respectively. The pore network in Ph-SPEEKK evolves dynamically and develops wide pores for {lambda} > 20, which leads to a jump in methanol crossover and ion transport. This study demonstrates the potential of aromatic membranes as low-cost challengers to Nafion for direct methanol fuel cell applications and the need to develop innovative strategies to combat methanol crossover at high hydration levels.

  11. Proton conductivity in Nafion{reg_sign} 117 and in a novel bis[(perfluoroalkyl)sulfonyl]imide ionomer membrane

    SciTech Connect

    Sumner, J.J.; Creager, S.E.; Ma, J.J.; DesMarteau, D.D.

    1998-01-01

    A study of proton conductivity in a commercial sample of Nafion{reg_sign} 117 and a structurally similar bis[(perfluoroalkyl)sulfonyl]imide ionomer membrane under variable temperature and humidity conditions is reported. The sulfonyl imide ionomer was synthesized using a novel redox-initiated emulsion copolymerization method, and conductivities were measured using a galvanostatic four-point-probe electrochemical impedance spectroscopy technique. Both materials exhibited a strong dependence of conductivity on temperature and humidity, with conductivity in both cases being strongly diminished with decreasing humidity (at constant temperature) and increasing temperature (at constant water partial pressure). The observed behavior is consistent with a liquid-like mechanism of proton conductivity whereby protons are transported as hydrated hydronium ions through water-filled pores and channels in the ionomer.

  12. Low-temperature synthesis of nano-TiO2 anatase on nafion membrane for using on DMFC

    NASA Astrophysics Data System (ADS)

    Tuan, Nguyen Manh; Thanh Nha, Ngo; Hoang Tuyen, Nguyen

    2009-09-01

    Low-temperature synthesis of 60-70°C of anatase nanocrystalline titanium dioxide TiO2 using sol-gel technique on Nafion membrane is investigated and characterized. Titan tetraisopropoxide (TTIP) is used as precursor and ethanol as the solvent. The best precursor to solvent weight ratio has been used for the synthesis of nano-TiO2 particles. The X-ray diffractograms and TEM images show the formation of anatase structure of nanocrystalline TiO2 at low temperatures as shown with average particle size below 12 nm. The films deposited by spin coating technique using these nanoparticles show the crystalline and porous nature of the films. The nano-TiO2 film as shown can be used to reduce the cross-over permeation of methanol through the PEM and increase electric power of the DMFC.

  13. [Electrocatalytic oxidation of SMZ at multi-wall carbon nanotubes-Nafion modified glassy carbon electrode and its electrochemical determination application].

    PubMed

    Sun, Yu-Qin; You, Wei; Gao, Zuo-Ning

    2008-04-01

    Electrochemical behaviors, electrochemical kinetics and electrochemical determination of sulfamethoxazole (SMZ) at both glassy carbon electrode (GCE) and multi-wall carbon nanotubes-Nafion modified glassy carbon electrode (MWCNTs-Nafion/GCE) were investigated by cyclic voltammetry (CV), chronocoulometry (CC), chronoamperometry (CA), linear scan voltammetry (LSV) and amperometric i-t curve. The experimental results showed that the electrochemical oxidation of SMZ was sluggish on GCE, but the oxidation peak current of SMZ increased significantly at MWCNTs-Nafion/GCE in comparison with that at the bare GCE, which indicated that MWCNTs-Nafion/GCE could catalyze the electrochemical oxidation of SMZ very well. The plot of oxidation peak currents versus the square roots of the scanning rates for the redox in the potential range of 10-1,000 mV x s(-1) showed a straight line, as expected for a diffusion-limited electrochemical process for SMZ electrochemical oxidation. At the bare GCE and MWCNTs-Nafion/GCE the oxidation peak current was linearly proportional to the concentration of SMZ over the concentration range 5.0 x 10(-5)-2.5 x 10(-3) mol x L(-1) and 1.0 x 10(-5)-6.0 x 10(-3) mol x L(-1). The detection limits were 1.0 x 10(-5) and 5.0 x 10(-7) mol x L(-1). The relative standard deviation was between 0.85% -1.98% and the recovery was in the range of 98%-101.2%. This MWCNTs-Nafion/GCE could be applied in SMZ electrochemical determination with satisfied results. The proposed method can be applied to the determination of SMZ in tablet samples with satisfied results.

  14. Caractérisation de la structure des membranes ionomères (NAFION^{tinytextregistered}) par diffusion de rayons X aux petits angles

    NASA Astrophysics Data System (ADS)

    Rubatat, L.; Rollet, A. L.; Diat, O.; Gébel, G.

    2002-07-01

    Ionomer membranes, like Nafion^{tinytextregistered} used in fuel cell, present a nano- phase separation between domains with different ionic concentrations. Up to now models describe the ionic domains as spheres of about 40 Å diameter. Small angles X-ray scattering studies over a large range of wave vectors, lead to a new assumption for the Nafion structure, describing the polymer aggregation as elongated objects surrounding by the ionic charges. Les membranes ionomères de type Nafion^{tinytextregistered} utilisées en pile à combustible, sont caractérisées par une nano-séparation de phases entre des domaines plus ou moins riches en sites ioniques. Les modèles proposés pour décrire ces domaines ioniques, les représentent généralement sous forme de sphères de 40 Å de diamètre. L'étude en diffusion de rayons X que nous avons menée récemment, sur une large gamme de vecteurs d'ondes, nous permet de proposer une vision différente de la structure du Nafion en considérant une agrégation de polymères sous formes d'objets très allongés, avec en surface les charges ioniques.

  15. Electron spin resonance probe for the solvation of ionomer membranes and other microscopically heterogeneous systems. Cu[sup 2+] in nafion, sephadex and silica gel

    SciTech Connect

    Bednarek, J.; Schlick, S. )

    1992-01-01

    Cu[sup 2+] is a sensitive electron spin resonance (ESR) probe for the penetration of various polar solvents in membranes made of Nafion and as an indicator for the replacement of one solvent by another. The ESR parameters (g and [sup 63]Cu hyperfine tensors) can be translated into a structure of the solvent around the cation. The replacement of a solvent in the membrane by another depends on the polarity of the two solvents. The solvent with the largest dielectric constant, N-methylformamide (NMF), can be replaced by water but not by methanol or acetonitrile (dielectric constants 182, 78.5, 32.7, and 37.5, respectively). Preferential solvation of the cation by water in three water/acetonitrile mixtures (9:1, 1:1, and 1:9 by volume) in contact with silica gel, Sephadex, and Nafion has been observed in various degrees. Nafion is most selective, followed by Sephadex and by silica gel. The selectivity appears to be related to electrostatic interactions which are strongest in Nafion and weakest in silica gel. 43 refs., 6 figs., 1 tab.

  16. A novel tridentate bis(phosphinic acid)phosphine oxide based europium(III)-selective Nafion membrane luminescent sensor.

    PubMed

    Sainz-Gonzalo, F J; Popovici, C; Casimiro, M; Raya-Barón, A; López-Ortiz, F; Fernández, I; Fernández-Sánchez, J F; Fernández-Gutiérrez, A

    2013-10-21

    A new europium(III) membrane luminescent sensor based on a new tridentate bis(phosphinic acid)phosphine oxide (3) system has been developed. The synthesis of this new ligand is described and its full characterization by NMR, IR and elemental analyses is provided. The luminescent complex formed between europium(III) chloride and ligand 3 was evaluated in solution, observing that its spectroscopic and chemical characteristics are excellent for measuring in polymer inclusion membranes. Included in a Nafion membrane, all the parameters (ligand and ionic additives) that can affect the sensitivity and selectivity of the sensing membrane as well as the instrumental conditions were carefully optimized. The best luminescence signal (λexc = 229.06 nm and λem = 616.02 nm) was exhibited by the sensing film having a Nafion : ligand composition of 262.3 : 0.6 mg mL(-1). The membrane sensor showed a short response time (t95 = 5.0 ± 0.2 min) and an optimum working pH of 5.0 (25 mM acetate buffer solution). The membrane sensor manifested a good selectivity toward europium(III) ions with respect to other trivalent metals (iron, chromium and aluminium) and lanthanide(III) ions (lanthanum, samarium, terbium and ytterbium), although a small positive interference of terbium(III) ions was observed. It provided a linear range from 1.9 × 10(-8) to 5.0 × 10(-6) M with a very low detection limit (5.8 × 10(-9) M) and sensitivity (8.57 × 10(-7) a.u. per M). The applicability of this sensing film has been demonstrated by analyzing different kinds of spiked water samples obtaining recovery percentages of 95-97%.

  17. Nafion-modified MoOx as effective room-temperature hole injection layer for stable, high-performance inverted organic solar cells.

    PubMed

    Qiu, Weiming; Müller, Robert; Voroshazi, Eszter; Conings, Bert; Carleer, Robert; Boyen, Hans-Gerd; Turbiez, Mathieu; Froyen, Ludo; Heremans, Paul; Hadipour, Afshin

    2015-02-18

    We present a hole injection layer processed from solution at room temperature for inverted organic solar cells. Bis(2,4-pentanedionato) molybdenum(VI) dioxide (MoO2(acac)2) is used as the precursor for MoOx. Small amounts of Nafion in the precursor solution allow it to form continuous films with good wetting onto the active layers. The hydrolysis of MoO2(acac)2 and the effects of adding Nafion to the precursor solution are studied by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The devices with solution-processed MoOx including Nafion exhibited comparable performance to the reference devices based on the commonly used hole injection layers such as poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) or evaporated MoO3. Inverted poly(3-hexylthiophene):[6,6]-phenyl C61-butyric acid methyl ester devices with Nafion-modified MoOx maintain 80% of their initial power conversion efficiency upon exposure to ambient air for ∼5000 h, outperforming devices with PEDOT:PSS or with evaporated MoO3.

  18. Novel sensor based on carbon paste/Nafion® modified with gold nanoparticles for the determination of glutathione.

    PubMed

    Atta, Nada F; Galal, Ahmed; Azab, Shereen M

    2012-10-01

    Several problems for the direct electrochemical oxidation of reduced glutathione (GSH) challenge the usage of electroanalytical techniques for its determination. In this work, the electrochemical oxidation of GSH catalyzed by gold nanoparticles electrodeposited on Nafion modified carbon paste electrode in 0.04 mol L(-1) universal buffer solution (pH 7.4) is proved successful. The effect of various experimental parameters including pH, scan rate and stability on the voltammetric response of GSH was investigated. At the optimum conditions, the concentration of GSH was determined using differential pulse voltammetry (DPV) in two concentration ranges: 0.1 × 10(-7) to 1.6 × 10(-5) mol L(-1) and 2.0 × 10(-5) to 2.0 × 10(-4) mol L(-1) with correlation coefficients 0.9988, 0.9949 and the limit of detections (LOD) are 3.9 × 10(-9) mol L(-1) and 8.2 × 10(-8) mol L(-1), respectively, which confirmed the sensitivity of the electrode. The high sensitivity, wide linear range, good stability and reproducibility, and the minimal surface fouling make this modified electrode useful for the determination of spiked GSH in urine samples and in tablet with excellent recovery results obtained.

  19. Analysis of the hydration process and rotational dynamics of water in a Nafion membrane studied by 1H NMR spectroscopy.

    PubMed

    Wakai, Chihiro; Shimoaka, Takafumi; Hasegawa, Takeshi

    2013-08-06

    (1)H NMR spectroscopy is employed to reveal the hydration process of a Nafion membrane by measuring both the chemical shift and the spin-lattice relaxation time. In a former study, the hydration process was suggested to comprise two steps: the molecular adsorption of water on the sulfonic acid groups and wetting with liquid water. The present study has revealed the first step can further be divided into two steps. By introducing a new experimental technique, the quantitatively reliable NMR measurements of protons ((1)H) of water involved in the polymer membrane are realized. In addition, a new analytical procedure is developed using a reciprocal concentration on a saturation-adsorption model, and the hydration is clearly revealed to have three individual steps. Both the chemical shift and the relaxation time plots against the reciprocal concentration exhibit three linear parts with apparently different slopes. Of great interest is that the initial hydration is divided into two stages: the first hydration is a very strong adsorption of water probably on the hydroxyl group of the sulfonic acid group, and the second one is a relatively weak adsorption on another site of the sulfonic acid group. The third hydration is readily assigned to excess bulk (liquid-like) water as expected. These adsorption processes are readily correlated with the rotational motion of water by converting the spin-lattice relaxation time to the rotational correlation time.

  20. Investigations on transfer of water and vanadium ions across Nafion membrane in an operating vanadium redox flow battery

    NASA Astrophysics Data System (ADS)

    Sun, Chenxi; Chen, Jian; Zhang, Huamin; Han, Xi; Luo, Qingtao

    Diffusion coefficients of the vanadium ions across Nafion 115 (Dupont) in a vanadium redox flow battery (VRFB) are measured and found to be in the order of V 2+ > VO 2+ > VO 2 + > V 3+. It is found that both in self-discharge process and charge-discharge cycles, the concentration difference of vanadium ions between the positive electrolyte (+ve) and negative electrolyte (-ve) is the main reason causing the transfer of vanadium ions across the membrane. In self-discharge process, the transfer of water includes the transfer of vanadium ions with the bound water and the corresponding transfer of protons with the dragged water to balance the charges, and the transfer of water driven by osmosis. In this case, about 75% of the net transfer of water is caused by osmosis. In charge-discharge cycles, except those as mentioned in the case of self-discharge, the transfer of protons with the dragged water across the membrane during the electrode reaction for the formation of internal electric circuit plays the key role in the water transfer. But in the long-term cycles of charge-discharge, the net transfer of water towards +ve is caused by the transfer of vanadium ions with the bound water and the transfer of water driven by osmosis.

  1. Water Dynamics and Proton Transport Mechanisms of Nafion® 117/Phosphotungstic Acid Composite Membrane: A Molecular Dynamics Study.

    PubMed

    Akbari, Saeed; Hamed Mosavian, Mohammad Taghi; Ahmadpour, Ali; Moosavi, Fatemeh

    2017-09-19

    Nafion®/phosphotungstic acid composite membrane and impact of varying concentration of heteropoly acid (HPA) on the well-known effective mechanisms of proton transport were investigated using classical and quantum hopping molecular dynamics simulation. Our simulations demonstrated that the HPA particles exhibited a favorable influence on Grotthuss mechanism in proton transportation at low hydration levels. From radial distribution function examinations, it was found that HPA particles were solvated with water and also exhibited stronger affinity toward hydronium ions. It can be concluded that addition of hydrophilic particles such as HPA improved proton conductivity. To address this effectiveness, lifetime and half-life of hydrogen bond (H-bond) network in formed water clusters were investigated at different HPA concentrations. The analysis of H-bond network stability revealed that the lifetime of H-bond between water molecules and protons decreased with increasing HPA concentration. Moreover, we found that H-bond network between water molecules was more stable, and the mismatch between simulated bulk water and those formed water clusters in the considered systems decreased upon HPA addition. Indeed, for HPA doped membrane, the activation energy of proton transfer process from a hydronium ion to a water molecule was lower than for the undoped system. Water diffusion coefficient decreased and that of hydronium ion enhanced with an increase in HPA doping level. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Electrochemical behavior and voltammetric determination of norfloxacin at glassy carbon electrode modified with multi walled carbon nanotubes/Nafion.

    PubMed

    Huang, Ke-Jing; Liu, Xue; Xie, Wan-Zhen; Yuan, Hong-Xia

    2008-07-15

    A simple and rapid electrochemical method is developed for the determination of trace-level norfloxacin, based on the excellent properties of multi-walled carbon nanotubes (MWCNTs). The MWCNTs/Nafion film-coated glassy carbon electrode (GCE) is constructed and the electrochemical behavior of norfloxacin at the electrode is investigated in detail. The results indicate that MWCNTs modified glassy carbon electrode exhibited efficiently electrocatalytic oxidation for norfloxacin (NFX) with relatively high sensitivity, stability and life time. Under conditions of cyclic voltammetry, the current for oxidation of selected analyte is enhanced significantly in comparison to the bare GCE. The electrocatalytic behavior is further exploited as a sensitive detection scheme for the analyte determinations by linear sweep voltammetry (LSV). Under optimized condition in voltammetric method the concentration calibration range and detection limit (S/N=3) are 0.1-100 micromol/L and 5 x 10(-8)mol/L for NFX. The proposed method was successfully applied to NFX determination in tablets. The analytical performance of this sensor has been evaluated for detection of the analyte in urine as a real sample.

  3. Design of a multiwalled carbon nanotube-Nafion-cysteamine modified tyrosinase biosensor and its adaptation of dopamine determination.

    PubMed

    Canbay, Erhan; Akyilmaz, Erol

    2014-01-01

    In this work, a multiwalled carbon nanotube (MWCNT)-Nafion-cysteamine (CA) modified tyrosinase biosensor brings a new and original perspective to biosensor technology intended for the development of dopamine determination. Dopamine measurements were done at 0.2V with the amperometric method by the developed biosensor system. In addition, in this study dopamine determination was carried out by using the differential pulse voltammetry method between potentials of 0.4 and -0.15 V. In the optimization studies of the biosensor, some parameters such as optimal pH, optimal temperature, optimal enzyme amount, and effect of MWCNT concentration were investigated. Afterward, in the characterization studies, some parameters such as linearity and reproducibility were determined. In the reproducibility experiment, an average value of 1.026 μM, a standard deviation of ±0.03975, and a coefficient of variation of 3.8% were determined for a 1-μM dopamine concentration (n=15). Determination of dopamine was carried out in drug samples by the developed biosensor.

  4. Square-wave anodic stripping voltammetric determination of thallium(I) at a Nafion/mercury film modified electrode.

    PubMed

    Lu, T H; Yang, H Y; Sun, I W

    1999-06-01

    A Nafion/mercury film electrode (NMFE) was used for the determination of trace thallium(I) in aqueous solutions. Thallium(I) was preconcentrated onto the NMFE from the sample solution containing 0.01 M ethylenediaminetetraacetate (EDTA), and determined by square-wave anodic stripping voltammetry (SWASV). Various factors influencing the determination of thallium(I) were thoroughly investigated. This modified electrode exhibits good resistance to interferences from surface-active compounds. The presence of EDTA effectively eliminated the interferences from metal ions, such as lead(II) and cadmium(II), which are generally considered as the major interferents in the determination of thallium at a mercury electrode. With 2-min preconcentration, linear calibration graphs were obtained over the range 0.05-100 ppb of thallium(I). An even lower detection limit, 0.01 ppb, were achieved with 5-min accumulation. The electrode is easy to prepare and can be readily renewed after each stripping experiment. Applicability of this procedure to various water samples is illustrated.

  5. Automated determination of glucose in soluble coffee using Prussian Blue-glucose oxidase-Nafion((R)) modified electrode.

    PubMed

    de Mattos, Ivanildo Luiz; da Cunha Areias, Madalena Carneiro

    2005-06-15

    A highly selective, fast and stable biosensor for determination of glucose in soluble coffee has been developed. The biosensor electrode consist of a thin film of ferric hexacyanoferrate (Prussian Blue or PB) electrodeposited on the glassy carbon electrode (GCE) (to provide a catalytic surface for the detection of hydrogen peroxide) glucose oxidase immobilized on top of the electrode and a Nafion((R)) polymer layer. The stability of the PB film and the biosensor was evaluated by injecting standard-solution (50muM H(2)O(2) and 0.5mM glucose) during 4h in a flow-injection system with the electrodes polarized at -50mV versus Ag/AgCl. The system is able to handle about 60 samples per hour and is very stable and suitable for industrial control. Determination of glucose in the range 2.5 and 15% (w/v) in phosphate buffer with precision (r.s.d.<1.5%) has been achieved and is in agreement with the conventional procedures. Linear calibration in the range of 0.15 and 2.50mM with detection limits of ca. 0.03mM has been obtained. The morphology of the enzyme glucose oxidase on the modified electrode has been analyzed by scanning electron microscopy (SEM) measurements.

  6. Influence of temperature on the electrokinetic properties and power generation efficiency of Nafion® 117 membranes

    NASA Astrophysics Data System (ADS)

    Catalano, Jacopo; Bentien, Anders

    2014-09-01

    In the present study we investigate the transport properties of Nafion® 117 membranes in temperatures ranging from ambient temperature up to 70 °C. The hydraulic permeability, streaming potential and ion conductivity have been measured as function of temperature in 0.03 M LiCl solutions in purposely designed, non-conductive set-ups. In particular, the apparent activation energies of the processes have been retrieved: 29.4 kJ mol-1, 9.3 kJ mol-1 and 22.9 kJ mol-1 for the hydraulic permeability, streaming potential coefficient and ion conductivity respectively. Based on the knowledge of the temperature dependence of these three independent properties the figure-of-merit of the electrokinetic energy conversion process has been calculated obtaining a monotonous increase of the efficiency with temperature. At 70 °C the electrokinetic efficiency is rather high about 26.6%:50% higher with respect to the one found at room temperature. The electrokinetic transport properties were also used to esteem the average pore size of the water channels in the polymer matrix resulting in pore diameters ranging approximately from 2.0 (25 °C) to 2.8 nm (70 °C).

  7. Multi-walled carbon nanotubes/Nafion composite film modified electrode as a sensor for simultaneous determination of ondansetron and morphine.

    PubMed

    Nigović, Biljana; Sadiković, Mirela; Sertić, Miranda

    2014-05-01

    The electrochemical behavior of ondansetron was studied on the multi-walled carbon nanotubes/Nafion polymer composite modified glassy carbon electrode (MWCNTs-Nafion/GCE). The oxidation peak potential was shifted from 1.32 V to 1.18 V compared to the bare electrode indicating excellent electrocatalytic activity of immobilized film toward drug molecule. The modified electrode exhibited a remarkable enhancement effect on voltammetric response due to the synergistic effect of nanomaterial and cation-exchange polymer on the electron transfer rate, the effective electrode area and the accumulation capability. After optimizing the experimental parameters, adsorptive stripping procedure was used for the determination of ondansetron in pharmaceutical formulation. The results were satisfactory in comparison with those obtained by high-performance liquid chromatography. In addition, the MWCNTs-Nafion/GCE exhibited high selectivity in the voltammetric measurements of ondansetron and co-administrated drug morphine with potential difference of 430 mV. The response peak currents had linear relationship with drug concentration in the range of 1.0 × 10(-7)-5.0 × 10(-6)M and 1.0 × 10(-7)-4.0 × 10(-6)M with detection limits 3.1 × 10(-8) and 3.2 × 10(-8)M for ondansetron and morphine, respectively. The electrode was successfully applied for simultaneous electrochemical sensing of both drugs in human serum samples after selective accumulation at the electrode surface.

  8. Electrochemical detection of DNA damage induced by acrylamide and its metabolite at the graphene-ionic liquid-Nafion modified pyrolytic graphite electrode.

    PubMed

    Qiu, Yanyan; Qu, Xiangjin; Dong, Jing; Ai, Shiyun; Han, Ruixia

    2011-06-15

    A new electrochemical biosensor for directly detecting DNA damage induced by acrylamide (AA) and its metabolite was presented in this work. The graphene-ionic liquid-Nafion modified pyrolytic graphite electrode (PGE) was prepared, and then horseradish peroxidase (HRP) and natural double-stranded DNA were alternately assembled on the modified electrode by the layer-by-layer method. The PGE/graphene-ionic liquid-Nafion and the construction of the (HRP/DNA)(n) film were characterized by electrochemical impedance spectroscopy. With the guanine signal in DNA as an indicator, the damage of DNA was detected by differential pulse voltammetry after PGE/graphene-ionic liquid-Nafion/(HRP/DNA)(n) was incubated in AA solution or AA+H(2)O(2) solution at 37°C. This method provides a new model to mimic and directly detect DNA damage induced by chemical pollutants and their metabolites in vitro. The results indicated that, in the presence of H(2)O(2), HRP was activated and catalyzed the transformation of AA to glycidamide, which could form DNA adducts and induce more serious damage of DNA than AA. In order to further verify these results, UV-vis spectrophotometry was also used to investigate DNA damage induced by AA and its metabolites in solution and the similar results were obtained.

  9. MWCNT-cysteamine-Nafion modified gold electrode based on myoglobin for determination of hydrogen peroxide and nitrite.

    PubMed

    Canbay, Erhan; Şahin, Berika; Kıran, Müge; Akyilmaz, Erol

    2015-02-01

    In this work, a novel amperometric biosensor of hydrogen peroxide (H2O2) was developed based on the immobilization of myoglobin (Mb) on the surface of the multi-walled carbon nanotube (MWCNT) -Nafion-cysteamine (CA) modified gold electrode (Au) and its electrocatalytic activity was used for the determination of nitrite (NO2(-)). In the optimization studies, the best MWCNT and myoglobin amount were investigated. It was discovered at the experiments for the optimization of the working conditions that the buffer at this study as 50.0mM, pH7.0 phosphate buffer (PBS) and working temperature as 30°C for the H2O2 biosensor. It was determined at the characterization studies on the biosensor that linear results are obtained between the ranges of 0.1μM to 70.0μM for H2O2 concentration and 1-250μM for NO2(-). The reproducibility of the biosensor was determined both H2O2 and nitrite. From the experiments, average value, standard deviation (SD) and coefficients of variation (CV%) were calculated to be 10.02±0.43μM, and 4.29% for 10.0μM H2O2 (n=6) and 52.0±2.1μM, and 3.89% for 50.0μM nitrite (n=8), respectively. At the same time the sample was analyzed for NO2(-) in drinking and mineral waters.

  10. Gold-nanoparticle-embedded nafion composite modified on glassy carbon electrode for highly selective detection of arsenic(III).

    PubMed

    Huang, Jing-Fang; Chen, Hsiao-Hua

    2013-11-15

    A Cu(I)-ion-mediating Au reduction is proposed for preparing an Au-nanoparticle-embedded nafion (NF(Aunano)) composite. The NF(Aunano) composite consisted of highly dense, well-dispersed, and protecting-agent-free Au nanocrystals with a narrow particle size (4.8±0.1 nm) distribution. The NF(Aunano) composite was characterized as a function of composition and particle size distribution using powder X-ray diffraction, transmission electron microscopy, and electrochemical measurements. It was demonstrated that the NF(Aunano) composite provided high activity in the redox behavior of As(III), and was used as a potential sensing material with low Au loading for As(III) detection. An NF(Aunano)-composite-modified electrode is easy to prepare and regenerate. The dynamic range of a calibration curve from 0.1 to 12.0 μg L(-1) (from 1.3 to 160 nM), y=23.98x (in μA μM(-1))+0.42 (R(2)=0.999), showed linear behavior with a slope of 23.98 μA μM(-1). The detection limit is as low as 0.047 μg L(-1) (0.63 nM). The chelating agent ethylenediaminetetraacetate (EDTA) can selectively chelate with interfering metal ions, forming bulky complexes or bulky anions that are excluded from the NF film. The presence of EDTA effectively eliminated interference from several metal ions, particularly Cu(II) and Hg(II), which are generally considered to be major interferents in the electroanalysis of As(III). This method was applicable to As(III) analysis in three real water samples, namely groundwater, lake, and drinking waters. © 2013 Elsevier B.V. All rights reserved.

  11. Sensitive HIV-1 detection in a homogeneous solution based on an electrochemical molecular beacon coupled with a nafion-graphene composite film modified screen-printed carbon electrode.

    PubMed

    Li, Bo; Li, Zhengliang; Situ, Bo; Dai, Zong; Liu, Qinlan; Wang, Qian; Gu, Dayong; Zheng, Lei

    2014-02-15

    A novel electrochemical sensing assay for sensitive determination of HIV-1 in a homogeneous solution has been developed using an electrochemical molecular beacon combined with a nafion-graphene composite film modified screen-printed carbon electrode (nafion-graphene/SPCE). The electrochemical molecular beacon (CAs-MB), comprising a special recognition sequence for the conserved region of the HIV-1 gag gene and a pair of carminic acid molecules as a marker, can indicate the presence of the HIV-1 target by its on/off electrochemical signal behavior. It is suitable for direct, electrochemical determination of HIV-1, thereby simplifying the detection procedure and improving the signal-to-noise (S/N) ratio. To further improve the sensitivity, the nafion-graphene/SPCE was used to monitor changes in the CAs-MB, which has notable advantages, such as being ultrasensitive, inexpensive, and disposable. Under optimized conditions, the peak currents showed a linear relationship with the logarithm of target oligonucleotide concentrations ranging from 40 nM to 2.56 μM, with a detection limit of 5 nM (S/N=3). This sensing assay also displays a good stability, with a recovery of 88-106.8% and RSD<7% (n=5) in real serum samples. This work may lead to the development of an effective method for early point-of-care diagnosis of HIV-1 infection. © 2013 Elsevier B.V. All rights reserved.

  12. Poly(1-vinylimidazole)/Pd-impregnated Nafion for direct methanol fuel cell applications

    NASA Astrophysics Data System (ADS)

    Tian, Ai Hua; Kim, Ji-Young; Shi, Jin Yi; Kim, Keon

    Nafion is modified by incorporating poly(1-vinylimidazole)/Pd composites into the ion cluster channels of the membrane. The poly(1-vinylimidazole)/Pd-impregnated (PVI/Pd-impregnated) membranes is characterized by means of X-ray photoelectron spectroscopy (XPS), proton conductivity and methanol permeability measurements and compared with those of the untreated Nafion. The dependence of the membrane proton conductivity and methanol permeability on the poly(1-vinylimidazole) (PVI) and palladium contents in the PVI/Pd-impregnated Nafion is studied. The performance of the cells employing the PVI/Pd-impregnated Nafion is evaluated using a direct methanol fuel cell (DMFC) unit cell. It is found that the best cell performance is obtained when Nafion is impregnated with the PVI/Pd composite solution for 20 h. This result suggests that there exists an optimum content of palladium and PVI in the modified membrane to obtain a high-proton conductivity and low-methanol permeability that result in a high-cell performance.

  13. Induced-charge electrokinetics, bipolar current, and concentration polarization in a microchannel-Nafion-membrane system.

    PubMed

    Park, Sinwook; Yossifon, Gilad

    2016-06-01

    The presence of a floating electrode array located within the depletion layer formed due to concentration polarization across a microchannel-membrane interface device may produce not only induced-charge electro-osmosis (ICEO) but also bipolar current resulting from the induced Faradaic reaction. It has been shown that there exists an optimal thickness of a thin dielectric coating that is sufficient to suppress bipolar currents but still enables ICEO vortices that stir the depletion layer, thereby affecting the system's current-voltage response. In addition, the use of alternating-current electro-osmosis by activating electrodes results in further enhancement of the fluid stirring and opens new routes for on-demand spatiotemporal control of the depletion layer length.

  14. Induced-charge electrokinetics, bipolar current, and concentration polarization in a microchannel-Nafion-membrane system

    NASA Astrophysics Data System (ADS)

    Park, Sinwook; Yossifon, Gilad

    2016-06-01

    The presence of a floating electrode array located within the depletion layer formed due to concentration polarization across a microchannel-membrane interface device may produce not only induced-charge electro-osmosis (ICEO) but also bipolar current resulting from the induced Faradaic reaction. It has been shown that there exists an optimal thickness of a thin dielectric coating that is sufficient to suppress bipolar currents but still enables ICEO vortices that stir the depletion layer, thereby affecting the system's current-voltage response. In addition, the use of alternating-current electro-osmosis by activating electrodes results in further enhancement of the fluid stirring and opens new routes for on-demand spatiotemporal control of the depletion layer length.

  15. The effect of platinum in a Nafion membrane on the durability of the membrane under fuel cell conditions

    NASA Astrophysics Data System (ADS)

    Zhao, D.; Yi, B. L.; Zhang, H. M.; Liu, Meilin

    The effect of platinum on free radical generation and membrane degradation in proton exchange membrane (PEM) fuel cells is investigated using three typical cell configurations. Examinations of the fluoride emission rates (FERs) under different testing conditions indicate that platinum deposited in the membrane plays an important role as a catalytic center for the formation of H 2O 2 and HO rad free radicals, leading to PEM degradation. The chemical durability of the membranes is tested in accelerated Fenton tests. It confirms the formation of free radicals in the presence of platinum in the decomposition of H 2O 2 by colorimetric method with dimethyl sulfoxide (DMSO) as the trapping agent. In addition, structural and morphological changes of the membranes are characterized using FT-IR spectroscopy and scanning electron microscopy (SEM).

  16. Electrocatalysis of chloroacetic acids (mono-, di- and tri-) at a C60-[dimethyl-(beta-cyclodextrin)]2 and nafion chemically modified electrode.

    PubMed

    Wei, M; Li, M; Li, N; Gu, Z; Zhou, X

    2001-01-26

    The C(60)-[dimethyl-(beta-cyclodextrin)](2) and nafion chemically modified electrode (CME) exhibits one electroreduction peak and two electro-oxidation peaks in a mixed solvent of water and acetonitrile (3:2, v/v) containing tetra-butylammonium perchlorate. The reduction of chloroacetic acids (mono-, di- and tri-) can be electrocatalyzed at this electrode, indicating that C(60)-[dimethyl-(beta-cyclodextrin)](2) is capable of mediating the electron transfer to chloroacetic acids. Values of the apparent catalytic rate constant, k, were determined by using the rotating-disk electrode (RDE).

  17. Electron Paramagnetic Resonance studies of x-ray irradiated Nafion

    NASA Astrophysics Data System (ADS)

    Fragoso, Juan; Usher, Timothy

    2007-03-01

    Fuel cells promise a bright future as power sources for a variety of electronic equipment as well as more power demanding elements. Nafion (DuPont's trademark of a sulfonated tetrafluorethylene polymer modified from Teflon) is the heart of Proton Exchange Membrane Fuel Cells (PEMFCs) as well as Direct Methanol Fuel Cells (DMFCs). Fuel cells are used to power electronic equipment on spacecraft, satellites and unpiloted high altitude aircraft, where ionizing radiation can be a concern. Electron Paramagnetic Resonance (EPR) is a spectroscopic technique that is very sensitive to free radicals such as those produced by ionizing radiation therefore EPR can give us a window into the degradation of the Nafion membranes due to the ionizing radiation. Nafion samples were irradiated using a x-ray diffractometer with a copper target operating at 40kV and 55mA for at least 3hrs. X-Band EPR spectroscopy of the irradiated nafion reveals a peak at 3400G with a width of 10G, which decays over time, completely diminishing in a couple of weeks. Preliminary results from the polarization studies on the effects of ionizing radiation will also be presented.

  18. Genistein Modified Polymer Blends for Hemodialysis Membranes

    NASA Astrophysics Data System (ADS)

    Chang, Teng; Kyu, Thein; Define, Linda; Alexander, Thomas

    2012-02-01

    A soybean-derived phytochemical called genistein was used as a modifying agent to polyether sulfone/polyvinyl pyrrolidone (PES/PVP) blends to produce multi-functional hemodialysis membranes. With the aid of phase diagrams of PES/PVP/genistein blends, asymmetric porous membranes were fabricated by coagulating in non-solvent. Both unmodified and genistein modified PES/PVP membranes were shown to be non-cytotoxic to the blood cells. Unmodified PES/PVP membranes were found to reduce reactive oxygen species (ROS) levels, whereas the genistein modified membranes exhibited suppression for ˜60% of the ROS levels. Also, the genistein modified membranes revealed significant suppression of pro-inflammatory cytokines: IL-1β, IL-6, and TNF-α. Moreover, addition of PVP to PES showed the reduced trend of platelet adhesion and then leveled off. However, the modified membranes exhibited suppression of platelet adhesion at low genistein loading, but beyond 15 wt%, the platelet adhesion level rised up.

  19. Characterization of perfluorinated cation-exchange membranes MF-4SC surface modified with halloysite nanotubes

    NASA Astrophysics Data System (ADS)

    Filippov, A.; Afonin, D.; Kononenko, N.; Shkirskaya, S.

    2015-10-01

    The electrical conductivity and diffusion permeability through perfluorinated cation-exchange membranes MF-4SC (Russian analog of the Nafion-type membrane), whose surface is modified by nanotubes of halloysite using short exposures of low temperature microwave plasma, are theoretically investigated using the Nernst-Planck approach. The method of quantitative evaluation of physicochemical parameters (individual and averaged diffusion coefficients and averaged distribution coefficients of ion pairs in the membrane) of the systems `electrolyte solution - bi-layer ion-exchange membrane - water/electrolyte solution', which was proposed by us earlier, is further developed. The aforementioned parameters of modified MF-4SC/halloysite membranes were found using the least squares method. For this purpose we used electrical conductivity as well as diffusion permeability data experimentally obtained for NaCl and HCl solutions of different concentration. A new model of bi-layer membrane system can be used for refining the calculated results by taking into account the difference between co- and counter-ion diffusivities inside the membrane layers. We showed that grafting the layer of halloysite nanotubes onto the membrane surface noticeably affects the exchange capacity as well as the structural and transport characteristics of the original perfluorinated membrane. In particular, such a membrane may show weak asymmetry of diffusion permeability when its position inside a measuring cell is changed. Hybrid MF-4SC/halloysite membranes can thus be productively used in fuel cells and catalysis.

  20. Synthesis and characterization of Nafion/SiO2 - MOx (M= Ti, Zr, W) nanocomposite membranes by sol-gel reaction for fuel cells

    NASA Astrophysics Data System (ADS)

    Shahzadi, Ambreen; Ahmed, Riaz; Siddiq, Muhammad

    2014-06-01

    Development of efficient and durable cation exchange membranes for fuel cells is important particularly a method for inhibiting the volatility of water at higher temperature is a crucial issue. Nafion composite membranes were prepared by impregnation with SiO2, SiO2 -TiO2, SiO2 - WO3, and SiO2 - ZrO2 by immersing these in-situ sol-gel solution and stirring. The sol-gel solution mixture served to swell the pores of the membrane to maximize the adsorption of the precursor solution. The composite membranes have been characterized by X-ray diffraction, scanning electron microscopy, water uptake, ion exchange capacity and conductivity. XRD studies showed the crystallinity and particle sizes of oxides. FTIR showed the bond formation in oxide mixtures. SEM provides information about the morphology of the particles. Water uptake increased gradually from pure membrane to SiO2, SiO2 - TiO2, SiO2 -WO3, and SiO2 - ZrO2 particles added membranes and was maximum for SiO2 - ZrO2 added membrane. Composite membranes exhibited higher water uptake, ion exchange capacity, conductivity and can improve the efficiency and durability of PEM fuel cells considerably.

  1. Simultaneous voltammetric determination of paracetamol and ascorbic acid using a boron-doped diamond electrode modified with Nafion and lead films.

    PubMed

    Tyszczuk-Rotko, Katarzyna; Bęczkowska, Ilona; Wójciak-Kosior, Magdalena; Sowa, Ireneusz

    2014-11-01

    The paper describes the fabrication and application of a novel sensor (a boron-doped diamond electrode modified with Nafion and lead films) for the simultaneous determination of paracetamol and ascorbic acid by differential pulse voltammetry. The main advantage of the lead film and polymer covered boron-doped diamond electrode is that the sensitivity of the stripping responses is increased and the separation of paracetamol and ascorbic acid signals is improved due to the modification of the boron-doped diamond surface by the lead layer. Additionally, the repeatability of paracetamol and ascorbic acid signals is improved by the application of the Nafion film coating. In the presence of oxygen, linear calibration curves were obtained in a wide concentration range from 5×10(-7) to 2×10(-4) mol L(-1) for paracetamol and from 1×10(-6) to 5×10(-4) mol L(-1) for ascorbic acid. The analytical utility of the differential pulse voltammetric method elaborated was tested in the assay of paracetamol and ascorbic acid in commercially available pharmaceutical formulations and the method was validated by high performance liquid chromatography coupled with diode array detector.

  2. Electrochemical detection of blood alcohol concentration using a disposable biosensor based on screen-printed electrode modified with Nafion and gold nanoparticles.

    PubMed

    Luo, Peng; Xie, Guoming; Liu, Yi; Xu, Huajian; Deng, Shixiong; Song, Fangzhou

    2008-01-01

    Blood alcohol determination plays an important role in laboratory medicine and forensic medicine. Nowadays, many methods are being used for alcohol measurement, but these methods are time-consuming and complex to perform laborious sample pre-treatment. The disposable amperometric biosensor, due to its portability, low cost and potential for fabrication, should be readily applicable for blood alcohol determination. The biosensor was fabricated by immobilizing alcohol dehydrogenase and nicotinamide adenine dinucleotide coated by Nafion combined with gold nanoparticles onto the surface of screen-printed electrode modified with Meldola's blue. Evaluations of biosensor performance were performed according to the relevant National Committee for Clinical Laboratory Standards standard. The biosensor response for serum alcohol presents good linearity, precision, stability, accuracy, and specificity. The biosensor exhibits the capability of detecting blood alcohol concentration in the clinical laboratory and in forensic medicine, unnecessarily performing laborious sample pre-treatment.

  3. Molecular catalysis of the oxygen reduction reaction by iron porphyrin catalysts tethered into Nafion layers: An electrochemical study in solution and a membrane-electrode-assembly study in fuel cells

    NASA Astrophysics Data System (ADS)

    He, Qinggang; Mugadza, Tawanda; Kang, Xiongwu; Zhu, Xiaobing; Chen, Shaowei; Kerr, John; Nyokong, Tebello

    2012-10-01

    This study was motivated by the need for improved understanding of the kinetics and transport phenomena in a homogeneous catalyst system for the oxygen reduction reaction (ORR). Direct interaction between the sulfonic groups of Nafion and an Fe(III) meso-tetra(N-methyl-4-pyridyl) porphine chloride (Fe(III)TMPyP) compound was observed using FTIR and in situ UV-Vis spectroelectrochemical characterizations. A positive shift of the half wave potential value (E1/2) for ORR on the iron porphyrin catalyst (Fe(III)TMPyP) was observed upon addition of a specific quantity of Nafion ionomer on a glassy carbon working electrode, indicating not only a faster charge transfer rate but also the role of protonation in the oxygen reduction reaction (ORR) process. A membrane electrode assembly (MEA) was made as a sandwich of a Pt-coated anode, a Nafion® 212 membrane, and a Fe(III)TMPyP + Nafion ionomer-coated cathode. This three-dimensional catalysis system has been demonstrated to be working in a H2/O2 proton exchange membrane (PEM) fuel cell test.

  4. Pervaporation of Water from Aqueous HI using Nafion®-117 Membranes for the Sulfur-Iodine Thermochemical Water Splitting Process

    SciTech Connect

    Frederick F. Stewart; Christopher J. Orme; Michael G. Jones

    2005-04-01

    Nafion®-117 membranes have been successfully used to remove water from aqueous hydriodic acid (HI) by pervaporation. HI feeds were concentrated from approximately 1.7 M to 5 M, and permeate concentrations ranged from 10-3 M to 10-4 M, regardless of the feed HI concentration. Temperatures examined were 22 °C, 50 °C, 70 °C, and 100 °C. Using 180 ìm thick films, fluxes at 22 °C were 0.43 Kg/m2h, and increased with increasing system temperature to a maximum of 1.5 Kg/m2h at 100 °C. Durability studies over a period of three months operation revealed little membrane degradation and, in all cases, the membranes retained their bulk physical properties in that they remained flexible and plastic. More intensive thermomechanical testing revealed changes in the membrane morphology upon pervaporation of the HI feed at 100 °C, however these changes were not reflected in the observed water transport behavior.

  5. A novel solid-state electrochemiluminescence sensor for melamine with Ru(bpy)3(2+)/mesoporous silica nanospheres/Nafion composite modified electrode.

    PubMed

    Cao, Hongmei; Hu, Xiaoqing; Hu, Chenyi; Zhang, Yang; Jia, Nengqin

    2013-03-15

    A novel melamine electrochemiluminescence (ECL) sensor was developed based on mesoporous SiO(2) nanospheres/Ru(bpy)(3)(2+)/Nafion modified electrodes. The homogeneous mesoporous silica nanospheres, synthesized using modified Stöber sol-gel process, were characterized by Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM) and Brunauer-Emmett-Teller (BET). The ECL and electrochemistry of the modified electrodes were investigated with tri-n-propylamine (TPA) as the coreactant. Furthermore, the mesporous SiO(2) nanospheres/Ru(bpy)(3)(2+)-based modified electrodes were used for ECL determination of melamine. The analytical performances of this ECL sensor for melamine based on its enhancement ECL emission of Ru(bpy)(3)(2+) were investigated. The results indicated that the sensor exhibited excellent performance during melamine determination with a wide linear range (7.81×10(-9)-5×10(-6) M), low detection limit (2.6×10(-9) M). The high sensitivity and stability mainly resulted from the high surface area and special structure of the mesoporous silica nanospheres. The proposed ECL approach was used to analyze the melamine content in powdered milk with satisfactory results.

  6. An electrochemiluminescent biosensor for glucose based on the electrochemiluminescence of luminol on the nafion/glucose oxidase/poly(nickel(II)tetrasulfophthalocyanine)/multi-walled carbon nanotubes modified electrode.

    PubMed

    Qiu, Bin; Lin, Zhenyu; Wang, Jian; Chen, Zhihuang; Chen, Jinhua; Chen, Guonan

    2009-04-15

    A poly(nickel(II) tetrasulfophthalocyanine)/multi-walled carbon nanotubes composite modified electrode (polyNiTSPc/MWNTs) was fabricated by electropolymerization of NiTSPc on MWNTs-modified glassy carbon electrode (GCE). The modified electrode was found to be able to greatly improve the emission of luminol electrochemiluminescence (ECL) in a solution containing hydrogen peroxide. Glucose oxidase (GOD) was immobilized on the surface of polyNiTSPc/MWNTs modified GC electrode by Nafion to establish an ECL glucose sensor. Under the optimum conditions, the linear response range of glucose was 1.0x10(-6) to 1.0x10(-4) mol L(-1) with a detection limit of 8.0x10(-8) mol L(-1) (defined as the concentration that could be detected at the signal-to-noise ratio of 3). The ECL sensor showed an outstanding well reproducibility and long-term stability. The established method has been applied to determine the glucose concentrations in real serum samples with satisfactory results.

  7. Performance of Nafion® N115, Nafion® NR-212, and Nafion® NR-211 in a 1 kW Class All Vanadium Mixed Acid Redox Flow Battery

    SciTech Connect

    Reed, David M.; Thomsen, Edwin C.; Wang, Wei; Nie, Zimin; Li, Bin; Wei, Xiaoliang; Koeppel, Brian J.; Sprenkle, Vincent L.

    2015-07-01

    Three Nafion membranes of similar composition but different thicknesses were operated in a 3-cell 1kW class all vanadium mixed acid redox flow battery. The influence of current density on the charge/discharge characteristics, coulombic and energy efficiency, capacity fade, operating temperature and pressure drop in the flow circuit will be discussed and correlated to the Nafion membrane thickness. Material costs associated with the Nafion membranes, ease of handling the membranes, and performance impacts will also be discussed.

  8. Modification for Uniform Surface of Nafion Ultrathin Film Deposited by Inkjet Printing.

    PubMed

    Guo, Yanglu; Ono, Yutaro; Nagao, Yuki

    2015-09-22

    A lack of knowledge about the features of Nafion confined to ultrathin films at the interface has motivated additional examinations to promote the performance of polymer electrolyte membrane fuel cells (PEMFCs). In this work, we demonstrated the utilization of practical film-forming technique inkjet printing to fabricate a Nafion ultrathin film less than 10 nm thickness. However, the well-known "coffee-ring" effect caused poor quality of the printed pattern, which has restricted its application. This report describes a systematic investigation of necessary parameters such as ink concentration, substrate type, pitch, and offset for printing processes. Furthermore, post-treatment in an ethanol vapor atmosphere exhibited a significant effect on flattening and homogenizing the film surface morphology. Results show that the well-distributed Nafion ultrathin film modified by ethanol vapor annealing manifested much-improved proton conductivity.

  9. Electrochemiluminescence of an electrocatalytic action of etimicin on Tris(2,2'-bipyridyl)ruthenium(II) immobilized in Nafion modified carbon paste electrode.

    PubMed

    Zhuang, Yafeng; Zhang, Jintao

    2010-01-01

    A sensitive electrochemiluminescence (ECL) detection of etimicin at Tris(2,2'-bipyridyl)ruthenium(II) [Ru(bpy)(3) (2+)]-Nafion modified carbon paste electrodes was developed. The immobilized Ru(bpy)(3) (2+) shows good electrochemical and photochemical activities. Electrochemical and electrochemiluminescence characterizations of the modified carbon electrodes were made by means of cyclic voltammetry and electrochemical impendence spectroscopy. The modified electrode showed an electrocatalytic response to the oxidation of etimicin, producing a sensitized ECL signal. The ECL sensor showed a linear response to etimicin in the range of 8.0-160.0 ng mL(-1) with a detection limit of 6.7 ng mL(-1). This method for etimicin determination possessed good sensitivity and reproducibility with a coefficient of variation of 5.1% (n = 7) at 100 ng mL(-1). The ECL sensor showed good selectivity and long-term stability. Its surface could be renewed quickly and reproducibly by a simple polish step.

  10. Property modification of nafion via polymer blending with polyimide (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Hwang, Taeseon; Nam, Jungsoo; Lee, Dong-Chan; Kim, Kwang Jin

    2017-04-01

    The blended ion exchange membrane between Nafion and Polyimide (PI) was used for fabrication of the ionic polymer-metal composite (IPMC) not only to redeem inherent drawbacks of Nafion such as high cost or environment-unfriendliness but also to enhance mechanical properties of Nafion. PI solution was blended in Nafion solution by a volume ratio and membranes were prepared through solution casting method. The prepared blended Nafion membranes can be fabricated IPMCs with electroless plating of platinum electrode onto its surface. The surface resistance of all prepared IPMCs is measured through 2-point probe. This study investigated the chemical structure and mechanical properties of prepared blended membranes. Moreover, we characterized the cross-section morphology and studied the electromechanical performances (displacement and blocking force) of prepared IPMC actuators. The prepared IPMC actuators with blended Nafion membranes were demonstrated comparable electromechanical performance by significantly reducing the content of Nafion.

  11. Mediated proton transport through Nafion 117 membranes imbibed with varying concentrations of aqueous VOSO4 (VO2+) and NH4VO3 (VO2+) in 2 M H2SO4

    NASA Astrophysics Data System (ADS)

    Suarez, Sophia; Paterno, Domenec

    2016-11-01

    We performed an extensive study on Nafion 117 membrane imbibed with various concentrations of aqueous ammonium metavanadate (NH4VO3), and vanadyl sulfate (VOSO4), in 2 M H2SO4 over the temperature range of 20-100 °C, using 1H NMR and AC Impedance spectroscopies. The objective was to determine the effect of the tetravalent (VO2+) and pentavalent (VO2+) vanadium ions on the proton transport of Nafion 117.1H NMR chemical shift and linewidth data show greater short-range proton transport for the VO2+ imbibed membranes compared with the VO2+. However, the local environments seem to differ in that while the data for VO2+ imbibed membranes seem to follow more the trends observed for water hydrated Nafion 117, those for the VO2+ followed the trend of its aqueous bulk vanadium solvents, indicating that viscosity plays a larger role for the VO2+ imbibed membranes compared to the VO2+.

  12. Antioxidant status and Na(+), K (+)-ATPase activity in freshwater fish Carassius auratus exposed to different combustion products of Nafion 117 membrane: an integrated biomarker approach.

    PubMed

    Feng, Mingbao; Wang, Xinghao; Wang, Chao; Qin, Li; Wei, Zhongbo; Wang, Zunyao

    2015-03-01

    Nafion 117 membrane (N117), an important polymer electrolyte membrane (PEM), has been widely applied in numerous chemical technologies. Its increasing production and utilization will inevitably lead to the problem of waste disposal, with incineration as an important method. However, toxicity data of its combustion products on aquatic organisms have been seldom reported. The present study was therefore conducted to investigate the antioxidant response and Na(+), K(+)-ATPase activity in liver of Carassius auratus exposed to different combustion products of N117 for 5, 15, and 30 days. The concentrations of fluorine ion (F(-)) in the aquaria among the exposure durations were analyzed using the ion chromatography system. The results showed that these treatments have the capability to induce oxidative stress and suppress Na(+), K(+)-ATPase activity, as indicated by some significant alterations on these measured toxicity end-points in fish liver. According to the integrated biomarker response (IBR) index, the toxicity intensity of these experimental treatments was tentatively ranked. Taken together, these observations provided some preliminary data on the potential toxicity of the combustion products of N117 on aquatic organisms and could fill the information gaps in the toxicity database of the current-use PEM.

  13. Enhanced electromechanical response of Ionic Polymer-Metal Composite (IPMC) actuators by various Nafion roughening levels

    NASA Astrophysics Data System (ADS)

    Wang, Yanjie; Liu, Jiayu; Chen, Hualing

    2016-04-01

    Recently, Ionic polymer metal composites (IPMCs), becoming an increasingly popular material, are used as soft actuators for its inherent properties of light weight, flexibility, softness, especial efficient transformation from electrical energy to mechanical energy with large bending strain response to low activation voltage. This paper mainly focuses on the suitable conditions for surface-roughening of Nafion 117 membrane. The surfaces of Nafion membrane were pretreated and optimized by sandblasting, mainly considering the change of sandblasting time and powder size. The modified surfaces are characterized in terms of their topography from the confocal laser scanning microscope (CLSM) and SEM. Then, the detailed change in surface and interfacial electrodes and performances for IPMC actuators prepared by the roughened membranes, were measured and discussed. The results show that an optimized roughening condition with large interface area (capacitance) can effectively increases the electromechanical responses of IPMC.

  14. Amperometric biosensor based on prussian blue and nafion modified screen-printed electrode for screening of potential xanthine oxidase inhibitors from medicinal plants.

    PubMed

    El Harrad, Loubna; Amine, Aziz

    2016-04-01

    A simple and sensitive amperometric biosensor was developed for the screening of potential xanthine oxidase inhibitors from medicinal plants. This biosensor was prepared by immobilization of xanthine oxidase on the surface of prussian blue modified screen-printed electrodes using nafion and glutaraldehyde. The developed biosensor showed a linear amperometric response at an applied potential of +0.05 V toward the detection of hypoxanthine from 5 μM to 45 μM with a detection limit of 0.4 μM (S/N=3) and its sensitivity was found to be 600 mA M(-1) cm(-2). In addition, the biosensor exhibited a good storage stability. The inhibition of xanthine oxidase by allopurinol was studied under the optimized conditions. The linear range of allopurinol concentration is obtained up to 2.5 μM with an estimated 50% of inhibitionI50=1.8 μM. The developed biosensor was successfully applied to the screening of xanthine oxidase inhibitors from 13 medicinal plants belonging to different families. Indeed, Moroccan people traditionally use these plants as infusion for the treatment of gout and its related symptoms. For this purpose, water extracts obtained from the infusion of these plants were used for the experiments. In this work, 13 extracts were assayed and several of them demonstrated xanthine oxidase inhibitory effect, with an inhibition greater than 50% compared to spectrophotometry measurements that only few extracts showed an inhibition greater than 50%.

  15. UV-spectrophotometry and square wave voltammetry at nafion-modified carbon-paste electrode for the determination of doxazosin in urine and formulations.

    PubMed

    Fdez de Betoño, S; Arranz Garcia, A; Arranz Valentín, J F

    1999-08-01

    By using several electrochemical techniques, the study of electroanalytical behaviour of antihipertensive Doxazosin at Nafion modified carbon paste electrode (NMCPE) has been carried out. The voltammetric peak is very pH dependent, reaching the maximum i(p) at pH 6.8 (Ep -0.17 V), the reduction process being quasi-reversible and fundamentally controlled by adsorption. A method based on the control of adsorptive preconcentration of the Doxazosin on the NMCPE, before its voltammetric determination, is proposed. The detection limit reached using square wave voltammetry (SWV) as redissolution technique was 2.33x10(-11) M and the variation coefficient at 2x10(-9) M level was 3.54%. A spectrophotometric study of Doxazosin has also been made and two waves at 244 and 329 nm (pH 1.7), were obtained. The wave at 329 nm changes its height and position with the pH, allowing the pKa determination (6.94+/-0.21) using different methods. The obtained detection limit was 0.5x10(-6) M, and the variation coefficient at 1.5x10(-5) M level was 0.99%. The UV spectrophotometric method is sufficiently accurate and precise to be applied in the Carduran tablets assay, while the voltammetric method (AdS-SWV) can in addition be used to determine the drug at trace level in human urine samples with good recoveries.

  16. A study on novel pulse preparation and electrocatalytic activities of Pt/C-Nafion electrodes for proton exchange membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Li, Jingjing; Ye, Feng; Chen, Ling; Wang, Tongtao; Li, Jianling; Wang, Xindong

    To aim at reducing the platinum loading and increasing the utilization of platinum in PEMFC electrode, a new pulse electrodeposition technique for preparing proton exchange membrane fuel cell (PEMFC) electrodes has been developed in this paper. This method combines coating Pt seeds on the C-Nafion substrate and introducing polyethylene glycol (PEG) into the deposition solution. SEM images of the samples show that Pt seeds and PEG take an important role in the morphology of the Pt deposit. The surface area and average particle size of Pt were determined by charge integration under the hydrogen desorption peaks of cyclic voltammetry. The electrocatalytic activities of these electrodes towards oxygen reduction reaction (ORR) were investigated by using rotating disc electrode (RDE). The Pt catalyst which was prepared by Pt seeds and PEG, its active surface area and electrocatalytic activity towards ORR were improved remarkably. And the optimized electrode displayed higher catalytic activity than a conventional electrode made from commercial Pt/C catalyst. The possible reasons for the effects of Pt seeds and PEG on the higher catalytic activity of prepared Pt catalysts have been preliminarily discussed.

  17. Property modification of Nafion via polymer blending with ethylene vinyl alcohol "polyimide" (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Hwang, Taeseon; Nam, Jungsoo; Shen, Qi; Trabia, Sarah; Suhr, Jonghwan; Lee, Dong-Chan; Kim, Kwang Jin

    2016-04-01

    The blended ion exchange membrane between Nafion and ethylene vinyl alcohol (EVOH) was used for fabrication of the ionic polymer-metal composite (IPMC) to redeem inherent drawbacks of Nafion such as high cost or environment-unfriendliness. EVOH solution was blended in Nafion solution by a volume ratio of 15 and 30 % membranes were prepared through solution casting method. The prepared blended Nafion membranes can be fabricated IPMCs with deposition of platinum electrode onto its surface without crack or delamination. The surface resistance of all prepared IPMCs is measured through 2 point probe. This study investigated the chemical structure and thermal properties of prepared membranes. Moreover, we characterized the cross-section morphology and studied the electromechanical performances (displacement and blocking force) of prepared IPMC actuators. The IPMC actuators with proposed blended Nafion membranes were demonstrated comparable electromechanical performance by significantly reducing the content of Nafion.

  18. Electrochemical sensors for the simultaneous determination of zinc, cadmium and lead using a Nafion/ionic liquid/graphene composite modified screen-printed carbon electrode.

    PubMed

    Chaiyo, Sudkate; Mehmeti, Eda; Žagar, Kristina; Siangproh, Weena; Chailapakul, Orawon; Kalcher, Kurt

    2016-04-28

    A simple, low cost, and highly sensitive electrochemical sensor, based on a Nafion/ionic liquid/graphene composite modified screen-printed carbon electrode (N/IL/G/SPCE) was developed to determine zinc (Zn(II)), cadmium (Cd(II)), and lead (Pb(II)) simultaneously. This disposable electrode shows excellent conductivity and fast electron transfer kinetics. By in situ plating with a bismuth film (BiF), the developed electrode exhibited well-defined and separate peaks for Zn(II), Cd(II), and Pb(II) by square wave anodic stripping voltammetry (SWASV). Analytical characteristics of the BiF/N/IL/G/SPCE were explored with calibration curves which were found to be linear for Zn(II), Cd(II), and Pb(II) concentrations over the range from 0.1 to 100.0 ng L(-1). With an accumulation period of 120 s detection limits of 0.09 ng mL(-1), 0.06 ng L(-1) and 0.08 ng L(-1) were obtained for Zn(II), Cd(II) and Pb(II), respectively using the BiF/N/IL/G/SPCE sensor, calculated as 3σ value of the blank. In addition, the developed electrode displayed a good repeatability and reproducibility. The interference from other common ions associated with Zn(II), Cd(II) and Pb(II) detection could be effectively avoided. Finally, the proposed analytical procedure was applied to detect the trace metal ions in drinking water samples with satisfactory results which demonstrates the suitability of the BiF/N/IL/G/SPCE to detect heavy metals in water samples and the results agreed well with those obtained by inductively coupled plasma mass spectrometry. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Preparation and properties of high performance nanocomposite proton exchange membrane for fuel cell

    NASA Astrophysics Data System (ADS)

    Lin, Yu-Feng; Yen, Chuan-Yu; Ma, Chen-Chi M.; Liao, Shu-Hang; Hung, Chih-Hung; Hsiao, Yi-Hsiu

    Various spatially enlarged organoclays were prepared by using poly(oxyproplene)-backboned quaternary ammonium salts of various molecular weights M w 230, 400 and 2000 as the intercalating agents for Na +-montmorillonite. The modified MMT was utilized to improve the compatibility with Nafion ®. Sufficient interaction of the modified MMT with Nafion ® was studied by using X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS). The performance of the Nafion ®/ m-MMT composite membranes for direct methanol fuel cell (DMFCs) was evaluated in terms of water uptake, ion exchange capacity (IEC), methanol permeability, proton conductivity, and cell performance. The methanol permeability of the composite membrane decreased with the increasing of m-MMT content. The proton conductivity of the membrane was lowered slightly from that of pristine Nafion ® membrane. These results led to an essential improvement in the single-cell performance of DMFCs.

  20. A new high-performance ionic polymer-metal composite based on Nafion/polyimide blends

    NASA Astrophysics Data System (ADS)

    Nam, Jungsoo; Hwang, Taeseon; Kim, Kwang Jin; Lee, Dong-Chan

    2017-03-01

    For the first time, we report ion-exchange membranes based on Nafion and polyimide (PI, Kapton) blends to fabricate ionic polymer-metal composites (IPMCs). Polyamic acid [PAA, poly(pyromellitic dianhydride-co-4,4‧-oxydianiline), as a precursor of PI] solution was blended with Nafion solution using physical blending method to provide PAA-Nafion blend membrane. This work demonstrates that, by simple physical blending method, the thermal and mechanical properties of Nafion can be improved while maintaining the excellent actuating performance. After thermal imidization, PAA converted into PI, resulting in PI-Nafion blend membrane. Optimum conditions to cast PAA-Nafion blends and thermal imidization have been established, and blend membranes with PI wt% of 6, 12, 18, and 30 were prepared. Fourier transform infrared spectroscopy confirmed the incorporation of PI in the Nafion matrix. Thermal decomposition unique to the PI became more noticeable as the content of PI increased, which was measured by thermogravimetric analysis. Dynamic mechanical analysis showed that the storage modulus (E‧) increased as a function of PI content while loss modulus (E″) exhibited only a minor change, which resulted in the decrease in the damping properties (tan δ). The blend membranes were fabricated into IPMCs by deposition of platinum electrode onto the membrane surface through electroless plating process. Among tested, NPI-18 IPMC actuator, which has 18 wt% of PI in Nafion, showed comparable electromechanical performance to the commercially available Nafion 117 IPMC actuator.

  1. Modified SPEEK membranes for direct ethanol fuel cell

    NASA Astrophysics Data System (ADS)

    Maab, Husnul; Nunes, Suzana Pereira

    Membranes with low ethanol crossover were prepared aiming their application for direct ethanol fuel cell (DEFC). They were based on (1) sulfonated poly(ether ether ketone) (SPEEK) coated with carbon molecular sieves (CMS) and (2) on SPEEK/PI homogeneous blends. The membranes were characterized concerning their water and ethanol solution uptake, water and ethanol permeability in pervaporation experiments and their performance in DEFC tests. The ethanol permeabilities for the CMS-coated (180 nm and 400 nm thick layers) SPEEK were 8.5 and 3.1 × 10 -10 kg m s -1 m -2 and for the homogeneous SPEEK/PI blends membranes with 10, 20 and 30 wt.% of PI were 4.4, 1.0 and 0.4 × 10 -10 kg m s -1 m -2 respectively, which is 2- to 50-fold lower than that for plain SPEEK (19 × 10 -10 kg m s -1 m -2). Particularly the SPEEK/PI membranes had substantially better performance than Nafion 117 ® membranes in DEFC tests at 60 °C and 90 °C.

  2. Biological Fuel Cells and Membranes

    PubMed Central

    Ghassemi, Zahra; Slaughter, Gymama

    2017-01-01

    Biofuel cells have been widely used to generate bioelectricity. Early biofuel cells employ a semi-permeable membrane to separate the anodic and cathodic compartments. The impact of different membrane materials and compositions has also been explored. Some membrane materials are employed strictly as membrane separators, while some have gained significant attention in the immobilization of enzymes or microorganisms within or behind the membrane at the electrode surface. The membrane material affects the transfer rate of the chemical species (e.g., fuel, oxygen molecules, and products) involved in the chemical reaction, which in turn has an impact on the performance of the biofuel cell. For enzymatic biofuel cells, Nafion, modified Nafion, and chitosan membranes have been used widely and continue to hold great promise in the long-term stability of enzymes and microorganisms encapsulated within them. This article provides a review of the most widely used membrane materials in the development of enzymatic and microbial biofuel cells. PMID:28106711

  3. Biological Fuel Cells and Membranes.

    PubMed

    Ghassemi, Zahra; Slaughter, Gymama

    2017-01-17

    Biofuel cells have been widely used to generate bioelectricity. Early biofuel cells employ a semi-permeable membrane to separate the anodic and cathodic compartments. The impact of different membrane materials and compositions has also been explored. Some membrane materials are employed strictly as membrane separators, while some have gained significant attention in the immobilization of enzymes or microorganisms within or behind the membrane at the electrode surface. The membrane material affects the transfer rate of the chemical species (e.g., fuel, oxygen molecules, and products) involved in the chemical reaction, which in turn has an impact on the performance of the biofuel cell. For enzymatic biofuel cells, Nafion, modified Nafion, and chitosan membranes have been used widely and continue to hold great promise in the long-term stability of enzymes and microorganisms encapsulated within them. This article provides a review of the most widely used membrane materials in the development of enzymatic and microbial biofuel cells.

  4. NMR and Electrochemical Investigation of the Transport Properties of Methanol and Water in Nafion and Clay-Nanocomposites Membranes for DMFCs

    PubMed Central

    Nicotera, Isabella; Angjeli, Kristina; Coppola, Luigi; Aricò, Antonino S.; Baglio, Vincenzo

    2012-01-01

    Water and methanol transport behavior, solvents adsorption and electrochemical properties of filler-free Nafion and nanocomposites based on two smectite clays, were investigated using impedance spectroscopy, DMFC tests and NMR methods, including spin-lattice relaxation and pulsed-gradient spin-echo (PGSE) diffusion under variable temperature conditions. Synthetic (Laponite) and natural (Swy-2) smectite clays, with different structural and physical parameters, were incorporated into the Nafion for the creation of exfoliated nanocomposites. Transport mechanism of water and methanol appears to be influenced from the dimensions of the dispersed platelike silicate layers as well as from their cation exchange capacity (CEC). The details of the NMR results and the effect of the methanol solution concentration are discussed. Clays particles, and in particular Swy-2, demonstrate to be a potential physical barrier for methanol cross-over, reducing the methanol diffusion with an evident blocking effect yet nevertheless ensuring a high water mobility up to 130 °C and for several hours, proving the exceptional water retention property of these materials and their possible use in the DMFCs applications. Electrochemical behavior is investigated by cell resistance and polarization measurements. From these analyses it is derived that the addition of clay materials to recast Nafion decreases the ohmic losses at high temperatures extending in this way the operating range of a direct methanol fuel cell. PMID:24958179

  5. Membrane stiffness is modified by integral membrane proteins.

    PubMed

    Fowler, Philip W; Hélie, Jean; Duncan, Anna; Chavent, Matthieu; Koldsø, Heidi; Sansom, Mark S P

    2016-09-20

    The ease with which a cell membrane can bend and deform is important for a wide range of biological functions. Peripheral proteins that induce curvature in membranes (e.g. BAR domains) have been studied for a number of years. Little is known, however, about the effect of integral membrane proteins on the stiffness of a membrane (characterised by the bending rigidity, Kc). We demonstrate by computer simulation that adding integral membrane proteins at physiological densities alters the stiffness of the membrane. First we establish that the coarse-grained MARTINI forcefield is able to accurately reproduce the bending rigidity of a small patch of 1500 phosphatidyl choline lipids by comparing the calculated value to both experiment and an atomistic simulation of the same system. This enables us to simulate the dynamics of large (ca. 50 000 lipids) patches of membrane using the MARTINI coarse-grained description. We find that altering the lipid composition changes the bending rigidity. Adding integral membrane proteins to lipid bilayers also changes the bending rigidity, whilst adding a simple peripheral membrane protein has no effect. Our results suggest that integral membrane proteins can have different effects, and in the case of the bacterial outer membrane protein, BtuB, the greater the density of protein, the larger the reduction in stiffness.

  6. Immobilization of β-galactosidase on modified polypropilene membranes.

    PubMed

    Vasileva, Nastya; Iotov, Vladislav; Ivanov, Yavor; Godjevargova, Tzonka; Kotia, Nana

    2012-12-01

    A new immobilized system: β-galactosidase-modified polypropylene membrane was created. It was obtained 13 different carriers by chemical modification of polypropylene membranes by two stages. The first stage is treatment with K(2)Cr(2)O(7) to receive carboxylic groups on membrane surface. The second stage is treatment with different modified agents ethylendiamine, hexamethylenediamine, hydrazine dihydrochloride, hydroxylamine, o-phenylenediamine, p-phenylenediamine, N,N'-dibenzyl ethylenediamine diacetate to receive amino groups. The quantity of the amino groups, carboxylic groups and the degree of hydrophilicity of unmodified and modified polypropilene membranes were determined. β-Galactosidase was chemically immobilized on the obtained carries by glutaraldehyde. The highest relative activity of immobilized enzyme was recorded at membrane modified with 10% hexamethylenediamine (Membrane 5) - 92.77%. The properties of immobilized β-galactosidase on different modified membranes - pH optimum, temperature optimum, pH stability and thermal stability were investigated and compared with those of free enzyme. The storage stability of all immobilized systems was studied. It was found that the most stable system is immobilized enzyme on Membrane 5. The system has kept 90% of its initial activity at 300th day (pH=6.8; 4°C). The stability of the free and immobilized β-galactosidase on the modified membrane 5 with 10% HMDA in aqueous solutions of alcohols - mono-, diol and triol was studied. The kinetics of enzymatic reaction of free and immobilized β-galactosidase on the modified membrane 5 at 20°C and 40°C and at the optimal pH for both forms of the enzyme were investigated. It was concluded that the modified agent - hexamethylenediamine, with long aliphatic chain ensures the best immobilized β-galactosidase system. Copyright © 2012 Elsevier B.V. All rights reserved.

  7. Effect of bound state of water on hydronium ion mobility in hydrated Nafion using molecular dynamics simulations

    SciTech Connect

    Mabuchi, Takuya; Tokumasu, Takashi

    2014-09-14

    We have performed a detailed analysis of the structural properties of the sulfonate groups in terms of isolated and overlapped solvation shells in the nanostructure of hydrated Nafion membrane using classical molecular dynamics simulations. Our simulations have demonstrated the correlation between the two different areas in bound water region, i.e., the first solvation shell, and the vehicular transport of hydronium ions at different water contents. We have employed a model of the Nafion membrane using the improved force field, which is newly modified and validated by comparing the density and water diffusivity with those obtained experimentally. The first solvation shells were classified into the two types, the isolated area and the overlapped area. The mean residence times of solvent molecules explicitly showed the different behaviors in each of those areas in terms of the vehicular transport of protons: the diffusivity of classical hydronium ions in the overlapped area dominates their total diffusion at lower water contents while that in the isolated area dominates for their diffusion at higher water contents. The results provided insights into the importance role of those areas in the solvation shells for the diffusivity of vehicular transport of hydronium ions in hydrated Nafion membrane.

  8. Immobilization of urease onto chemically modified acrylonitrile copolymer membranes.

    PubMed

    Godjevargova, T; Gabrovska, K

    2003-06-26

    Poly (acrylonitrile-methylmethacrylate-sodium vinylsulfonate) membranes were subjected to seven different chemical modifications. The amounts of new groups incorporated in the membranes with the modifications were determined. Urease was covalently immobilized on the modified membranes. Both the amount of bound protein and relative activity of immobilized urease were measured. The highest activity was found for urease bound to membranes modified with hydroxylammonium sulfate (68%) and hydrazinium sulfate (67%). Optimum pH of free urease was determined to be 5.8. For positively charged membranes, pH optimum was shifted to higher values, while for negatively charged membranes-to lower pH. The charge of the matrix affected also the rate of the enzyme reaction. The highest rate was measured with urease immobilized on membranes modified with hydroxylammonium sulfate and hydrazinium sulfate. The major part of the immobilized enzyme on different modified membranes remained stable-only ca. 20% of enzyme activity was lost for 4 h at 70 degrees C while the free enzyme was totally inactivated.

  9. Electrochemiluminescence sensor for melamine based on a Ru(bpy)₃²⁺-doped silica nanoparticles/carboxylic acid functionalized multi-walled carbon nanotubes/Nafion composite film modified electrode.

    PubMed

    Chen, Xiaomei; Lian, Sai; Ma, Ying; Peng, Aihong; Tian, Xiaotian; Huang, Zhiyong; Chen, Xi

    2016-01-01

    In this work, a sensitive electrochemiluminescence (ECL) sensor for the determination of melamine (MEL) was developed based on a Ru(bpy)3(2+)-doped silica nanoparticles (RUDS)/carboxylic acid functionalized multi-walled carbon nanotubes (CMWCNTs)/Nafion composite film modified electrode. The homogeneous spherical RUDS were synthesized by a reverse microemulsion method. As Ru(bpy)3(2+) were encapsulated in the RUDS, Ru(bpy)3(2+) dropping from the modified electrode can be greatly prevented, which is helpful for obtaining a stable ECL signal. Moreover, to improve the conductivity of the film and promote the electron transfer rate on electrode surface, CMWCNTs with excellent electrical conductivity and large surface area were applied in the construction of the sensing film. As CMWCNTs acted as electron bridges making more Ru(bpy)3(2+) participate in the reaction, the ECL intensity was greatly enhanced. Under the optimum conditions, the relative ECL signal (△IECL) was proportional to the logarithmic MEL concentration ranging from 5×10(-13) to 1×10(-7) mol L(-1) with a detection limit of 1×10(-13) mol L(-1). To verify the reliability, the thus-fabricated ECL sensor was applied to determine the concentration of MEL in milk. Based on these investigations, the proposed ECL sensor exhibited good feasibility and high sensitivity for the determination of MEL, promising the applicability of this sensor in practical analysis.

  10. Electrochemically selective determination of dopamine in the presence of ascorbic and uric acids on the surface of the modified Nafion/single wall carbon nanotube/poly(3-methylthiophene) glassy carbon electrodes.

    PubMed

    Quan, Do Phuc; Tuyen, Do Phuc; Lam, Tran Dai; Tram, Phan Thi Ngoc; Binh, Nguyen Hai; Viet, Pham Hung

    2011-12-01

    A voltammetric method based on a combination of incorporated Nafion, single-walled carbon nanotubes and poly(3-methylthiophene) film-modified glassy carbon electrode (NF/SWCNT/PMT/GCE) has been successfully developed for selective determination of dopamine (DA) in the ternary mixture of dopamine, ascorbic acid (AA) and uric acid (UA) in 0.1M phosphate buffer solution (PBS) pH 4. It was shown that to detect DA from binary DA-AA mixture, the use of NF/PMT/GCE was sufficient, but to detect DA from ternary DA-AA-UA mixture NF/SWCNT/PMT/GCE was required. The later modified electrode exhibits superior electrocatalytic activity towards AA, DA and UA thanks to synergic effect of NF/SWCNT (combining unique properties of SWCNT such as high specific surface area, electrocatalytic and adsorptive properties, with the cation selectivity of NF). On the surface of NF/SWCNT/PMT/GCE AA, DA, UA were oxidized respectively at distinguishable potentials of 0.15, 0.37 and 0.53 V (vs. Ag/AgCl), to form well-defined and sharp peaks, making possible simultaneous determination of each compound. Also, it has several advantages, such as simple preparation method, high sensitivity, low detection limit and excellent reproducibility. Thus, the proposed NF/SWCNT/PMT/GCE could be advantageously employed for the determination of DA in real pharmaceutical formulations.

  11. Correlation between structure and conductivity in stretched Nafion

    NASA Astrophysics Data System (ADS)

    Allahyarov, Elshad; Taylor, Philip

    2008-03-01

    We have used coarse-grained simulation methods to investigate the effect of stretching-induced structure orientation on the proton conductivity of Nafion-like polyelectrolyte membranes. Recent experimental data on the morphology of ionomers describe Nafion as an aggregation of polymeric backbone chains forming elongated objects embedded in a continuous ionic medium. Uniaxial stretching of a recast Nafion film causes a preferential orientation of these objects in the direction of stretching. Our simulations of humid Nafion show that this has a strong effect on the proton conductivity, which is enhanced along the stretching direction, while the conductivity perpendicular to the stretched polymer backbone is strongly reduced. Stretching also causes the perfluorinated side chains to orient perpendicular to the stretching axis. The sulphonate multiplets shrink in diameter as the stretching is increased and show a spatially periodic ordering in their distribution. This in turn affects the distribution of contained water at low water contents. The water forms a continuous network with narrow bridges between small water clusters absorbed in head-group multiplets. We find the morphological changes in the stretched Nafion to be retained upon removal of the uniaxial stress.

  12. The platinum microelectrode/Nafion interface - An electrochemical impedance spectroscopic analysis of oxygen reduction kinetics and Nafion characteristics

    NASA Technical Reports Server (NTRS)

    Parthasarathy, Arvind; Dave, Bhasker; Srinivasan, Supramaniam; Appleby, John A.; Martin, Charles R.

    1992-01-01

    The objectives of this study were to use electrochemical impedance spectroscopy (EIS) to study the oxygen-reduction reaction under lower humidification conditions than previously studied. The EIS technique permits the discrimination of electrode kinetics of oxygen reduction, mass transport of O2 in the membrane, and the electrical characteristics of the membrane. Electrode-kinetic parameters for the oxygen-reduction reaction, corrosion current densities for Pt, and double-layer capacitances were calculated. The production of water due to electrochemical reduction of oxygen greatly influenced the EIS response and the electrode kinetics at the Pt/Nafion interface. From the finite-length Warburg behavior, a measure of the diffusion coefficient of oxygen in Nafion and diffusion-layer thickness was obtained. An analysis of the EIS data in the high-frequency domain yielded membrane and interfacial characteristics such as ionic conductivity of the membrane, membrane grain-boundary capacitance and resistance, and uncompensated resistance.

  13. Chemically modified opals as thin permselective nanoporous membranes.

    PubMed

    Newton, Michael R; Bohaty, Andrew K; White, Henry S; Zharov, Ilya

    2005-05-25

    Thin-film opals comprising three layers of 440 nm diameter SiO2 spheres were assembled on Pt electrodes and modified with amino groups on the silica surface. Diffusion of anionic, cationic, and neutral redox species through the opals was studied by cyclic voltammetry. The chemically modified opal membranes demonstrate high molecular throughput and, at low pH, selectively block transport of a cationic redox species relative to that of anionic and neutral redox species. This permselective behavior is attributed to the electrostatic interactions that are enhanced by the tortuous pathway within the opal and by the high surface area of the chemically modified spheres.

  14. Tris(2,2'-bipyridyl)ruthenium(II)-Zirconia-Nafion composite modified electrode applied as solid-state electrochemiluminescence detector on electrophoretic microchip for detection of pharmaceuticals of tramadol, lidocaine and ofloxacin.

    PubMed

    Ding, Shou-Nian; Xu, Jing-Juan; Zhang, Wen-Jia; Chen, Hong-Yuan

    2006-10-15

    Tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)(3)(2+))-Zirconia-Nafion composite modified glassy carbon disk electrode as a solid-state electrochemiluminescence (ECL) detector is successfully applied to an electrophoretic microchip system with a wall-jet configuration. Pharmaceuticals such as tramadol, lidocaine and ofloxacin were selected to characterize the performance of this microchip capillary electrophoresis (CE)-ECL detection system. Voltammetric and ECL behaviors of immobilized Ru(bpy)(3)(2+) were investigated in lidocaine system. Influences of the separation electric field to cyclic voltammograms (CVs) of the immobilized Ru(bpy)(3)(2+) were also investigated. Tramadol, lidocaine and ofloxacin can be baseline separated without any additives. The detection limits (S/N=3) were 2.5x10(-5)molL(-1) for tramadol, 5.0x10(-6)molL(-1) for lidocaine, 1.0x10(-5)molL(-1) for ofloxacin under the sample injection of picoliters, and the linear ranges were from 5.0x10(-5) to 2.5x10(-3)molL(-1) for tramadol, 1.0x10(-5) to 1.0x10(-3)molL(-1) for lidocaine, and 1.0x10(-5) to 2.5x10(-3)molL(-1) for ofloxacin, respectively.

  15. Hygro-thermal mechanical behavior of Nafion during constrained swelling

    NASA Astrophysics Data System (ADS)

    Silberstein, Meredith N.; Boyce, Mary C.

    Durability is a major limitation of current proton exchange membrane fuel cells. Mechanical stress due to hygro-thermal cycling is one failure mechanism of the polymer electrolyte membrane. In previous work the cyclic rate, temperature, and hydration dependent elastic-viscoplastic mechanical behavior of Nafion has been extensively investigated in uniaxial and biaxial tension, serving as a data basis and means of validation for a three-dimensional constitutive model. Here, the important effect of loading via constrained swelling is studied. Specifically, two types of loading are investigated: partially constrained swelling via a bimaterial swelling test and hygro-thermal cycling within a fuel cell. The bimaterial swelling conditions are examined via experiments in conjunction with modeling. Nafion/GDL bimaterial strips were hydrated and observed to curl significantly with the membrane on the convex side due to the large Nafion hygro-expansion coefficient. Upon drying the bimaterial strips developed a slight reverse curvature with the membrane on the concave side due to the plastic deformation which had occurred in the membrane during hydration. Finite element simulations utilizing the Nafion constitutive model successfully predicted the behavior during hydration and drying, providing insight on the constrained swelling physics and the ability of the model to predict such events. Simulations of in situ fuel cell hygro-thermal cycling are performed via a simplified two-dimensional fuel cell model. The simulation results confirm the finding of other studies that a tensile stress develops in the membrane during drying. Further, a concentration of negative hydrostatic pressure is found to develop just inside the channel region in the dried state supporting the theory of hygro-thermal driven mechanical stresses causing pinhole formation in the channel. The amplitude of the pressure cycling is found to be large and sensitive to both hygro-thermal ramp time and hold time

  16. A fabrication method of unique Nafion® shapes by painting for ionic polymer-metal composites

    NASA Astrophysics Data System (ADS)

    Trabia, Sarah; Hwang, Taeseon; Kim, Kwang J.

    2016-08-01

    Ionic polymer-metal composites (IPMC) are useful actuators because of their ability to be fabricated in different shapes and move in various ways. However, producing unique or intricate shapes can be difficult based upon the current fabrication techniques. Presented here is a fabrication method of producing the Nafion® membrane or thin film through a painting method. Using an airbrush, a Nafion water dispersion is sprayed onto an acrylonitrile butadiene styrene surface with a stencil of the desired shape. To verify that this method of fabrication produces a Nafion membrane similar to that which is commercially available, a sample that was made using the painting method and Nafion 117 purchased from DuPont™ were tested for various characteristics and compared. The results show promising similarities. The painted Nafion sample was chemically plated with platinum and compared with a traditional IPMC for its displacement and blocking force capabilities. The painted IPMC sample showed comparable results.

  17. Urease immobilized on modified polysulphone membrane: preparation and properties.

    PubMed

    Poźniak, G; Krajewska, B; Trochimczuk, W

    1995-01-01

    Porous asymmetric membranes were formed by the phase inversion method from one-to-one blends of polysulphone and its aminated derivative. Amino groups were introduced into polysulphone UDEL P 1700 by chlorosulphonation followed by amination. Urease was immobilized on the modified polysulphone membranes. The properties of the immobilized urease were investigated and related to the free enzyme. The Michaelis constant was 4.4 times higher for the immobilized than for the free urease. Immobilization improved the pH stability of the enzyme at pH < 6.5 as well as its temperature stability. However, the immobilization did not protect the enzyme against heat inactivation at 70 degrees C; the half-times for the activity decay were equal to 120 and 50 min for the free and immobilized enzymes, respectively. The immobilized urease exhibited good storage and operational stability, and good reusability, properties that prove the applicability of the obtained system in enzymatic-membrane reactors.

  18. Nafion-stabilised bimetallic Pt–Cr nanoparticles as electrocatalysts for proton exchange membrane fuel cells (PEMFCs)† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6ra16025e Click here for additional data file.

    PubMed Central

    Gupta, G.; Sharma, S.

    2016-01-01

    The current study investigated the unique combination of alloying (Pt with Cr) and Nafion stabilisation to reap the benefits of catalyst systems with enhanced catalytic activity and improved durability in PEMFCs. Pt–Cr alloy nanoparticles stabilised with Nafion were chosen in the current study owing to their higher stability in acidic and oxidising media at high temperatures compared to other Pt-transition metal alloys (e.g. Pt–Ni, Pt–Co). Two different precursor : reducing agent (1 : 10 and 1 : 20) ratios were used in order to prepare two different alloys, denoted as Pt–Cr 10 and Pt–Cr 20. The Pt–Cr 20 alloy system (with composition Pt80Cr20) demonstrated higher electrocatalytic activity for the oxygen reduction reaction compared to commercial Pt/C (TKK) catalysts. Accelerated stress tests and single cell tests revealed that Nafion stabilised alloy catalyst systems displayed significantly enhanced durability (only ∼20% loss of ECSA) compared with Pt/C (50% loss of ECSA) due to improved catalyst–ionomer interaction. Furthermore, the Pt–Cr 20 alloy system demonstrated a current density comparable to that of Pt/C making them promising potential electrocatalysts for proton exchange membrane fuel cells. PMID:27774145

  19. Modified axonemes and ciliary membranes in three polychaete species.

    PubMed

    Pfannenstiel, H D

    1982-01-01

    In living Ophryotrocha puerilis, Polyophthalmus pictus and Dinophilus gyrociliatus no modified cilia are present. Treatment with hyper- and hypotonic magnesium chloride solutions leads to the formation of either cilia with dilated tips or discocilia (paddle cilia). Discocilia show axoneme loops within distal swellings of the ciliary membranes. Both types of modified cilia regain their normal appearance if they are allowed to recover in seawater. The total number of discocilia and the diameter of the loops are inversely related to the osmolarity of the magnesium chloride solution used. Even isotonic solutions of magnesium chloride, which are usually used to anaesthetize marine worms, readily induce modified cilia. This indicates that the effect is not merely due to osmotic conditions. Glutaraldehyde and osmium tetroxide may act in the same way to induce modified cilia, a fact which may account for the numerous TEM and SEM documentations of modified cilia in various marine invertebrates. Which cilia in a particular species are modified varies from one specimen to another.

  20. An enhanced electrochemiluminescence sensor modified with a Ru(bpy)3(2+)/Yb2O3 nanoparticle/nafion composite for the analysis of methadone samples.

    PubMed

    Hosseini, Morteza; Pur, Mohammad Reza Karimi; Norouzi, Parviz; Moghaddam, Mohammad Reza; Ganjali, Mohammad Reza

    2017-07-01

    The sensitive interaction between Ru(bpy)3(2+) and methadone was used for the modification of a solid-state electrochemiluminescence electrode, and it was also successfully applied to determine methadone in the samples. The working electrode was made of a Yb2O3-containing modified carbon paste electrode. The presence of Yb2O3 nanoparticles in the structure of the electrode, was found to enhance its sensitizing effect towards the Ru(bpy)3(2+)-methadone electrochemiluminescence system. The electrodes with the optimal make-up revealed a linear ECL-concentration behavior from 5×10(-9)-3×10(-7)M and reached method detection limit as low as 2.1×10(-10)M with a relative standard deviation of 4.4% (S/N=3). This modified ECL could present a simple yet sensitive and selective route for the determination of methadone in different samples. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Protein binding properties of surface-modified porous polyethylene membranes.

    PubMed

    Greene, George; Radhakrishna, Harish; Tannenbaum, Rina

    2005-10-01

    In this study, we quantified the adsorption of immunoglobulin G (IgG) protein onto several polyelectrolyte-modified sintered porous polyethylene (PPE) membranes. The polymer surfaces had both cationic and anionic charges obtained via the adsorption of polyethylenimine (PEI) and polyacrylic acid (PAA), respectively, onto plasma-activated PPE. The amount of IgG adsorption was determined by measuring the gamma radiation emitted by [125I]-IgG radio labeled protein. By studying the impact of pH and ionic strength on IgG adsorption, we attempted to characterize the role and nature of the electrostatic interactions involved in the adsorption process to better understand how these interactions were influenced by the charge and structure of immobilized polyelectrolyte complexes at modified membrane surfaces. We were able to show that surface modification of PPE membranes with adsorbed PEI monolayers and PEI-PAA bilayers can greatly improve the IgG binding ability of the membrane under optimized conditions. We also showed that the observed improvement in the IgG binding is derived from electrostatic interactions between IgG and the polyelectrolyte surface. In addition, we found that the greatest IgG adsorption occurred when the IgG and the surface possessed predominantly opposite charges, rather than when the surface possessed the greatest electrostatic charge. Finally, we have found that the molecular weight of the terminating polyelectrolyte has a noticeable effect upon the electrostatic interactions between IgG and the PEI-PAA bilayer-modified PPE surfaces.

  2. Visualization of ion transport in Nafion using electrochemical strain microscopy

    SciTech Connect

    Kim, Suran; No, Kwangsoo; Hong, Seungbum

    2015-12-24

    The electromechanical response of a Nafion membrane immersed in water was probed using electrochemical strain microscopy (ESM) to redistribute protons and measure the resulting local strain that is caused by the movement of protons. We also measured the relaxation of protons from the surface resulting from proton diffusion. Using this technique, we can visualize and analyze the local strain change resulting from the redistribution and relaxation of hydrated protons.

  3. Electrospun fiber membranes enable proliferation of genetically modified cells

    PubMed Central

    Borjigin, Mandula; Eskridge, Chris; Niamat, Rohina; Strouse, Bryan; Bialk, Pawel; Kmiec, Eric B

    2013-01-01

    Polycaprolactone (PCL) and its blended composites (chitosan, gelatin, and lecithin) are well-established biomaterials that can enrich cell growth and enable tissue engineering. However, their application in the recovery and proliferation of genetically modified cells has not been studied. In the study reported here, we fabricated PCL-biomaterial blended fiber membranes, characterized them using physicochemical techniques, and used them as templates for the growth of genetically modified HCT116-19 colon cancer cells. Our data show that the blended polymers are highly miscible and form homogenous electrospun fiber membranes of uniform texture. The aligned PCL nanofibers support robust cell growth, yielding a 2.5-fold higher proliferation rate than cells plated on standard plastic plate surfaces. PCL-lecithin fiber membranes yielded a 2.7-fold higher rate of proliferation, while PCL-chitosan supported a more modest growth rate (1.5-fold higher). Surprisingly, PCL-gelatin did not enhance cell proliferation when compared to the rate of cell growth on plastic surfaces. PMID:23467983

  4. Effects of Nafion loading in anode catalyst inks on the miniature direct formic acid fuel cell

    NASA Astrophysics Data System (ADS)

    Morgan, Robert D.; Haan, John L.; Masel, Richard I.

    Nafion, within the anode and cathode catalyst layers, plays a large role in the performance of fuel cells, especially during the operation of the direct formic acid fuel cell (DFAFC). Nafion affects the proton transfer in the catalyst layers of the fuel cell, and studies presented here show the effects of three different Nafion loadings, 10 wt.%, 30 wt.% and 50 wt.%. Short term voltage-current measurements using the three different loadings show that 30 wt.% Nafion loading in the anode shows the best performance in the miniature, passive DFAFC. Nafion also serves as a binder to help hold the catalyst nanoparticles onto the proton exchange membrane (PEM). The DFAFC anode temporarily needs to be regenerated by raising the anode potential to around 0.8 V vs. RHE to oxidize CO bound to the surface, but the Pourbaix diagram predicts that Pd will corrode at these potentials. We found that an anode loading of 30 wt.% Nafion showed the best stability, of the three Nafion loadings chosen, for reducing the amount of loss of electrochemically active area due to high regeneration potentials. Only 58% of the area was lost after 600 potential cycles in formic acid compared to 96 and 99% for 10 wt.% and 50 wt.% loadings, respectively. Lastly we present cyclic voltammetry data that suggest that the Nafion adds to the production of CO during oxidation of formic acid for 12 h at 0.3 V vs. RHE. The resulting data showed that an increase in CO coverage was observed with increasing Nafion content in the anode catalyst layer.

  5. Preparation and characterization of sulfonated carbon nanotube/Nafion IPMC actuators

    NASA Astrophysics Data System (ADS)

    Ru, Jie; Wang, Yanjie; Chang, Longfei; Chen, Hualing; Li, Bo; Jia, Shuhai

    2016-04-01

    In this paper, we developed a new kind of ionic polymer metal composite (IPMC) actuator by doping sulfonated carbon nanotube (SCNT) into Nafion matrix to overcome some major drawbacks, such as low output force and short air-operation time, which restrict applications of conventional Nafion IPMC actuators. Firstly, SCNT was synthesized by coupled reaction of multi-walled carbon nanotubes and azo compounds and then doped into Nafion matrix by casting method. Subsequently, several key parameters of the SCNT-reinforced Nation matrix, water uptake ratio and equivalent stiffness, were revealed and the inner morphology of the membranes were observed by scanning electron microscopy. Finally, the effects of the SCNT on the electromechanical properties of IPMC actuators, especially the actuating performance, were evaluated experimentally and analyzed systematically. The results showed that SCNT was evenly dispersed in Nafion matrix and a small amount of SCNT could improve the performance of IPMC actuators significantly.

  6. Novel ACNT arrays based MEA structure-nano-Pt loaded ACNT/Nafion/ACNT for fuel cell applications.

    PubMed

    Zhang, Weimin; Chen, Jun; Minett, Andrew I; Swiegers, Gerhard F; Too, Chee O; Wallace, Gordon G

    2010-07-14

    A novel designed free-standing, sandwich-structured membrane electrode assembly (MEA), nano-Pt loaded (0.142 mg cm(-2)) ACNT/Nafion/ACNT via the attachment of two sets of aligned CNT array electrode structures to opposite sides of a Nafion PEM membrane exhibits significantly improved performance compared to commercially available Pt/CB catalysts used in PEM fuel cell applications.

  7. Transport of Zn(OH4)(2-) Ions Across a Polyolefin Microporous Membrane

    DTIC Science & Technology

    1992-12-22

    O_____I___-_-- A UL "OdYAI ULmfo 13. ABSTRACT (Maximum 200 words) Transport of Zn(OH)2- ions through modified microporous polypropylene membranes was...ion exclusion and good conductivity. Polypropylene membranes were chosen as suitable microporous separators which were then coated with Nafion to...NUMBERS Transport of Zn(OH)2- ions across a polyolefin microporous membrane C _______________________________________________ N00014-91-J1058 6

  8. Solubilization of carbon nanotubes by Nafion toward the preparation of amperometric biosensors.

    PubMed

    Wang, Joseph; Musameh, Mustafa; Lin, Yuehe

    2003-03-05

    The ability to solubilize single-wall and multiwall carbon nanotubes (CNT) in the presence of the perfluorinated polymer Nafion is described. Such use of Nafion as a solubilizing agent for CNT overcomes a major obstacle for creating CNT-based biosensing devices. Their association with Nafion does not impair the electrocatalytic properties of CNT. The resulting CNT/Nafion modified glassy-carbon electrodes exhibit a strong and stable electrocatalytic response toward hydrogen peroxide. The marked acceleration of the hydrogen peroxide redox process is very attractive for the operation of oxidase-based amperometric biosensors, as illustrated for the highly selective low-potential (-0.05 V vs Ag/AgCl) biosensing of glucose. These findings open the door for using CNT in a wide range of chemical sensors and nanoscale electronic devices.

  9. FY08 MEMBRANE CHARACTERIZATION REPORT FOR HYBRID SULFUR ELECTROLYZER

    SciTech Connect

    Hobbs, D; Hector Colon-Mercado, H; Mark Elvington, M

    2008-09-01

    This report summarizes results from all of the membrane testing completed to date at the Savannah River National Laboratory (SRNL) for the sulfur dioxide-depolarized electrolyzer (SDE). Several types of commercially-available membranes have been analyzed for ionic resistance and sulfur dioxide transport including perfluorinated sulfonic acid (PFSA), sulfonated polyether-ketone-ketone (SPEKK), and polybenzimidazole membranes (PBI). Of these membrane types, the poly-benzimidazole membrane, Celtec-L, exhibited the best combination of characteristics for use in an SDE. Several experimental membranes have also been analyzed including hydrated sulfonated Diels-Alder polyphenylenes (SDAPP) membranes from Sandia National Laboratory, perfluorosulfonimide (PFSI) and sulfonated perfluorocyclobutyl aromatic ether (S-PFCB) prepared by Clemson University, hydrated platinum-treated PFSA prepared by Giner Electrochemical Systems (GES) and Pt-Nafion{reg_sign} 115 composites prepared at SRNL. The chemical stability, SO{sub 2} transport and ionic conductivity characteristics have been measured for several commercially available and experimental proton-conducting membranes. Commercially available PFSA membranes such as the Nafion{reg_sign} series exhibited excellent chemical stability and ionic conductivity in sulfur dioxide saturated sulfuric acid solutions. Sulfur dioxide transport in the Nafion{reg_sign} membranes varied proportionally with the thickness and equivalent weight of the membrane. Although the SO{sub 2} transport in the Nafion{reg_sign} membranes is higher than desired, the excellent chemical stability and conductivity makes this membrane the best commercially-available membrane at this time. Initial results indicated that a modified Nafion{reg_sign} membrane incorporating Pt nanoparticles exhibited significantly reduced SO{sub 2} transport. Reduced SO{sub 2} transport was also measured with commercially available PBI membrane and several experimental membranes produced

  10. Photo Induced Membrane Separation for Water Purification and Desalination Using Azobenzene Modified Anodized Alumina Membranes.

    PubMed

    Fujiwara, Masahiro; Imura, Tatsuki

    2015-06-23

    Water purification and desalination to produce end-use water are important agendas in 21st century, because the global water shortage is becoming increasingly serious. Those processes using light energy, especially solar energy, without the consumption of fossil fuels are desired for creating sustainable society. For these earth-friendly water treatments, nanoporous materials and membranes are expected to provide new technologies. We have reported before that the repetitive photo isomerization of azobenzene groups between the trans and cis isomers induced by the simultaneous irradiation of UV and visible lights accelerates the molecular movement of nearby molecules in nanoporous materials. After further studies, we recently found that the permeation of water through azobenzene modified anodized alumina membranes as a photo responsive nanoporous membrane was achieved by the simultaneous irradiation of UV and visible lights, while no water penetration occurred under no light, only single UV or visible light. The photo induced permeation of water was promoted by the vaporization of water with the repetitive photo isomerization of azobenzene. This membrane permeation achieved the purification of water solutions, because dye molecules and a protein dissolved in aqueous solutions were not involved in the photo induced penetrated water. When 3.5% of sodium chloride solution as model seawater was employed for this membrane separation, the salt content of the permeated water was less than 0.01% to accomplish the complete desalination of seawater.

  11. Azobenzene Modified Polymer Electrolyte Membrane for Ion Gating

    NASA Astrophysics Data System (ADS)

    Piedrahita, Camilo; Mballa, Mireille; He, Ruixuan; Kyu, Thein

    By virtue of ion concentration gradient across cell membranes, neuron cells are highly polarized driving electrical potential difference (e.g., Gibbs law). To regulate and control ion movement, living cells have specific channels with gates that are permeable to cations, enabling or excluding them via charge polarity and size. This mechanism for generating and transmitting signals from one neuron to another controls body movement via brain function. By virtue of trans-cis isomerization, azobenzene derivative (AZO) has been heavily sought for ion-gating in biological cells as a means of signal generation and transmission through nervous systems. In this work, PEM consisted of PEGDA/SCN/LiTFSI was modified with AZO derivatives for gating of lithium ions. At low concentrations of azobenzene of 3 wt Supported by NSF-DMR 1502543.

  12. Purification and proteomics of pathogen-modified vacuoles and membranes

    PubMed Central

    Herweg, Jo-Ana; Hansmeier, Nicole; Otto, Andreas; Geffken, Anna C.; Subbarayal, Prema; Prusty, Bhupesh K.; Becher, Dörte; Hensel, Michael; Schaible, Ulrich E.; Rudel, Thomas; Hilbi, Hubert

    2015-01-01

    Certain pathogenic bacteria adopt an intracellular lifestyle and proliferate in eukaryotic host cells. The intracellular niche protects the bacteria from cellular and humoral components of the mammalian immune system, and at the same time, allows the bacteria to gain access to otherwise restricted nutrient sources. Yet, intracellular protection and access to nutrients comes with a price, i.e., the bacteria need to overcome cell-autonomous defense mechanisms, such as the bactericidal endocytic pathway. While a few bacteria rupture the early phagosome and escape into the host cytoplasm, most intracellular pathogens form a distinct, degradation-resistant and replication-permissive membranous compartment. Intracellular bacteria that form unique pathogen vacuoles include Legionella, Mycobacterium, Chlamydia, Simkania, and Salmonella species. In order to understand the formation of these pathogen niches on a global scale and in a comprehensive and quantitative manner, an inventory of compartment-associated host factors is required. To this end, the intact pathogen compartments need to be isolated, purified and biochemically characterized. Here, we review recent progress on the isolation and purification of pathogen-modified vacuoles and membranes, as well as their proteomic characterization by mass spectrometry and different validation approaches. These studies provide the basis for further investigations on the specific mechanisms of pathogen-driven compartment formation. PMID:26082896

  13. Three-dimensional analysis of Nafion layers in fuel cell electrodes.

    PubMed

    Lopez-Haro, M; Guétaz, L; Printemps, T; Morin, A; Escribano, S; Jouneau, P-H; Bayle-Guillemaud, P; Chandezon, F; Gebel, G

    2014-10-30

    Proton exchange membrane fuel cell is one of the most promising zero-emission power sources for automotive or stationary applications. However, their cost and lifetime remain the two major key issues for a widespread commercialization. Consequently, much attention has been devoted to optimizing the membrane/electrode assembly that constitute the fuel cell core. The electrodes consist of carbon black supporting Pt nanoparticles and Nafion as the ionomer binder. Although the ionomer plays a crucial role as ionic conductor through the electrode, little is known about its distribution inside the electrode. Here we report the three-dimensional morphology of the Nafion thin layer surrounding the carbon particles, which is imaged using electron tomography. The analyses reveal that doubling the amount of Nafion in the electrode leads to a twofold increase in its degree of coverage of the carbon, while the thickness of the layer, around 7 nm, is unchanged.

  14. Nonequilibrium molecular dynamics simulation of pressure-driven water transport through modified CNT membranes.

    PubMed

    Wang, Luying; Dumont, Randall S; Dickson, James M

    2013-03-28

    Nonequilibrium molecular dynamics (NEMD) simulations are presented to investigate the effect of water-membrane interactions on the transport properties of pressure-driven water flow passing through carbon nanotube (CNT) membranes. The CNT membrane is modified with different physical properties to alter the van der Waals interactions or the electrostatic interactions between water molecules and the CNT membranes. The unmodified and modified CNT membranes are models of simplified nanofiltration (NF) membranes at operating conditions consistent with real NF systems. All NEMD simulations are run with constant pressure difference (8.0 MPa) temperature (300 K), constant pore size (0.643 nm radius for CNT (12, 12)), and membrane thickness (6.0 nm). The water flow rate, density, and velocity (in flow direction) distributions are obtained by analyzing the NEMD simulation results to compare transport through the modified and unmodified CNT membranes. The pressure-driven water flow through CNT membranes is from 11 to 21 times faster than predicted by the Navier-Stokes equations. For water passing through the modified membrane with stronger van der Waals or electrostatic interactions, the fast flow is reduced giving lower flow rates and velocities. These investigations show the effect of water-CNT membrane interactions on water transport under NF operating conditions. This work can help provide and improve the understanding of how these membrane characteristics affect membrane performance for real NF processes.

  15. Nonequilibrium molecular dynamics simulation of pressure-driven water transport through modified CNT membranes

    NASA Astrophysics Data System (ADS)

    Wang, Luying; Dumont, Randall S.; Dickson, James M.

    2013-03-01

    Nonequilibrium molecular dynamics (NEMD) simulations are presented to investigate the effect of water-membrane interactions on the transport properties of pressure-driven water flow passing through carbon nanotube (CNT) membranes. The CNT membrane is modified with different physical properties to alter the van der Waals interactions or the electrostatic interactions between water molecules and the CNT membranes. The unmodified and modified CNT membranes are models of simplified nanofiltration (NF) membranes at operating conditions consistent with real NF systems. All NEMD simulations are run with constant pressure difference (8.0 MPa) temperature (300 K), constant pore size (0.643 nm radius for CNT (12, 12)), and membrane thickness (6.0 nm). The water flow rate, density, and velocity (in flow direction) distributions are obtained by analyzing the NEMD simulation results to compare transport through the modified and unmodified CNT membranes. The pressure-driven water flow through CNT membranes is from 11 to 21 times faster than predicted by the Navier-Stokes equations. For water passing through the modified membrane with stronger van der Waals or electrostatic interactions, the fast flow is reduced giving lower flow rates and velocities. These investigations show the effect of water-CNT membrane interactions on water transport under NF operating conditions. This work can help provide and improve the understanding of how these membrane characteristics affect membrane performance for real NF processes.

  16. Preparation of catalyst coated membrane by modified decal transfer method for proton exchange membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Indriyati; Irmawati, Y.; Prihandoko, B.

    2017-07-01

    A new catalyst coated membrane (CCM) was prepared by modified decal transfer method. A structure of ionomer/catalyst/carbon/substrate was used to facilitate the transfer of catalyst layer from decal substrate to the membrane at quite low hot-pressing temperature (120 °C) for 8 min. Several decal substrates were tested to select a proper substrate, namely PTFE cloth, PTFE film, aluminium foil, and OHP transparent sheet. The transfer degree of catalyst layer was estimated. Elemental analysis and SEM-mapping were performed to evaluate the residue, whereas contact angle measurement was conducted to characterize the hydrophobicity of decal substrates. The results showed that PTFE cloth and PFTE film transferred approximately 90% of catalyst layer onto the membrane, while the other two substrates were around 70%. Furthermore, the elemental analysis of the residue on the substrate revealed that it was mainly composed of carbon and fluorine for PTFE cloth and PTFE film. This result supports other findings that PTFE cloth and PTFE film are suitable as decal substrate at low temperature hot pressing for fabricating CCM.

  17. A Mechanistic Study of Chemically Modified Inorganic Membranes for Gas and Liquid Separations

    SciTech Connect

    Way, J Douglas

    2011-01-21

    This final report will summarize the progress made during the period August 1, 1993 - October 31, 2010 with support from DOE grant number DE-FG03-93ER14363. The objectives of the research have been to investigate the transport mechanisms in micro- and mesoporous, metal oxide membranes and to examine the relationship between the microstructure of the membrane, the membrane surface chemistry, and the separation performance of the membrane. Examples of the membrane materials under investigation are the microporous silica hollow fiber membrane manufactured by PPG Industries, chemically modified mesoporous oxide membranes, and polymer membranes containing microporous oxides (mixed matrix membranes). Analytical techniques such as NMR, FTIR and Raman spectroscopy, thermal analysis, and gas adsorption were used to investigate membrane microstructure and to probe the chemical interactions occurring at the gas-membrane interface.

  18. Enhanced biofouling resistance of polyethersulfone membrane surface modified with capsaicin derivative and itaconic acid

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Gao, Xueli; Wang, Qun; Sun, Haijing; Wang, Xiaojuan; Gao, Congjie

    2015-11-01

    The culprit of biofouling is the reproduction of viable microorganisms on the membrane surface. Recently, functionalization of membrane surface with natural antibacterial agents has drawn great attention. This work presents the fabrication of antibiofouling polyethersulfone (PES) ultrafiltration (UF) membranes by UV-assisted photo grafting of capsaicin derivative (N-(4-hydroxy-3-methoxy-benzyl)-acrylamide, HMBA) and itaconic acid (IA) on the surface of PES membrane. Results of FTIR-ATR, water static contact angle (WSCA) and atomic force microscopy (AFM) analysis confirmed the successful grafting of HMBA and IA on the membrane surface. We investigated the antifouling and antibacterial properties of these membranes using BSA and Escherichia coli as the test model, respectively. During a 150-min test, the modified membranes show much lower flux decline (42.7% for PES-g-1H0I, 22.2% for PES-g-1H1I and 7.7% for PES-g-1H5I) when compared with the pristine membrane (flux declined by 77%). The modified membranes exhibit excellent antibacterial activity (nearly 100%) when UV irradiation time was 6 min. The morphological study suggested that the E. coli on the pristine membrane showed a regular and smooth surface while that on the modified membrane was disrupted, which validated the antibacterial activity of the modified membranes.

  19. Donnan dialysis of transition metal ions using anion exchange membrane modified with Xylenol Orange

    SciTech Connect

    Sawicka, B.; Brajter, K.; Trojanowicz, M.; Kado, B. )

    1991-01-01

    A chelating ion-exchange membrane was obtained by modification of a PTFE-based anion-exchange membrane with Xylenol Orange. Its utility for dialysis of Cu(II), Ni(II), Mn(II), and Zn(II) was investigated by using receiver solutions without and with iminodiacetate. 1,2-diaminocyclohexanetetraacetic acid, and tetraethylenepentamine. In comparison to commercial PTFE cation-exchange membranes, modified chelating membranes exhibit for the metal ions investigated a larger differentiation of retention in the membrane phase and transport-to-receiver solution depending on the modifier used and the composition of the receiver solution.

  20. Characterization of modified PVDF membrane by gamma irradiation for non-potable water reuse.

    PubMed

    Lim, Seung Joo; Kim, Tak-Hyun; Shin, In Hwan

    2015-01-01

    Poly(vinylidene fluorine) (PVDF) membranes were grafted by gamma-ray irradiation and were sulfonated by sodium sulfite to modify the surface of the membranes. The characteristics of the modified PVDF membranes were evaluated by the data of Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscope (FE-SEM), the contact angle of the membrane surface and the water permeability. From the results of FT-IR, XPS and FE-SEM, it was shown that the modified membranes were successfully grafted by gamma-ray irradiation and were sulfonated. The content of oxygen and sulfur increased with the monomer concentration, while the content of fluorine sharply decreased. The pore size of the modified membranes decreased after gamma-ray irradiation. The contact angle and the water permeability showed that the hydrophilicity of the modified membranes played a role in determining the membrane performance. The feasibility study of the modified PVDF membranes for using non-potable water reuse were carried out using a laboratory-scale microfiltration system. Grey wastewater was used as the influent in the filtration unit, and permeate quality satisfied non-potable water reuse guidelines in the Republic of Korea.

  1. Peptide-modified PELCL electrospun membranes for regulation of vascular endothelial cells.

    PubMed

    Zhou, Fang; Jia, Xiaoling; Yang, Yang; Yang, Qingmao; Gao, Chao; Zhao, Yunhui; Fan, Yubo; Yuan, Xiaoyan

    2016-11-01

    The efficiency of biomaterials used in small vascular repair depends greatly on their ability to interact with vascular endothelial cells (VECs). Rapid endothelialization of the vascular grafts is a promising way to prevent thrombosis and intimal hyperplasia. In this work, modification of electrospun membranes of poly(ethylene glycol)-b-poly(l-lactide-co-ε-caprolactone) (PELCL) by three different peptides for regulation of VECs were studied in order to obtain ideal bioactive biomaterials as small diameter vascular grafts. QK (a mimetic peptide to vascular endothelial growth factor), Arg-Glu-Asp-Val (REDV, a specific adhesive peptide to VECs) and Val-Ala-Pro-Gly (VAPG, a specific adhesive peptide to vascular smooth muscle cells) were investigated. Surface properties of the modified membranes and the response of VECs were verified. It was found that protein adsorption and platelet adhesion were effectively suppressed with the introduction of QK, REDV or VAPG peptides on the PELCL electrospun membranes. Both QK- and REDV-modified electrospun membranes could accelerate the proliferation of VECs in the first 9days, and the QK-modified electrospun membrane promoted cell proliferation more significantly than the REDV-modified one. The REDV-modified PELCL membrane was the most favorable for VECs adhesion than QK- and VAPG-modified membranes. It was suggested that QK- or REDV-modified PELCL electrospun membranes may have great potential applications in cardiovascular biomaterials for rapid endothelialization in situ. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Molecular Composite Coatings on Nafion Using Layer-by-Layer Self-Assembly.

    PubMed

    Lefaux, Christophe J; Kim, Byoung-Suhk; Venkat, Narayanan; Mather, Patrick T

    2015-05-20

    Controlled growth of nanometer-scale multilayered coatings of negatively charged sulfonated poly(benzobisimidazole) (SPBI), complexed with positively charged poly(2-vinylpyridine) (P2VP) on quartz, and Nafion membrane as substrates has been explored. Both polymers, SPBI and P2VP, possess a net charge in methanol as a result of the dissolution of SPBI by complexation with triethylamine (TEA) and the protonation of P2VP with HCl, respectively, and thereby can form a multilayered molecular composite of alternating anionic SPBI and cationic P2VP via an electrostatic layer-by-layer (LbL) self-assembly. UV-vis absorption spectrophotometry was used to monitor the buildup and growth rate of such SPBI/P2VP multilayer films. Atomic force microscopy (AFM) was used to determine the roughness and thickness of the resulting SPBI/P2VP multilayers. As a result, it was found that a steady-state linear growth regime for the LbL self-assembled SPBI/P2VP multilayer films and coatings onto quartz and Nafion membranes was observed after completion of the first few deposition cycles, indicating the successful formation of the SPBI/P2VP multilayered assembly in methanol solutions. In addition, the SPBI/P2VP multilayer films in the perpendicular direction (flat view) demonstrated isotropic orientation distribution on the Nafion membrane, while the SPBI/P2VP multilayer films examined by X-ray scattering in the parallel direction (edge view) revealed anisotropic orientation, the combined observations indicating confinement of SPBI rods to the plane of the coating. We further found that the SPBI/P2VP multilayer coated Nafion possesses good thermal stability, as indicated by isothermal gravimetric analysis at 310 °C, and it was further observed that SPBI/P2VP multilayer coatings using the LbL self-assembly technique on Nafion membrane significantly increased the membrane stiffness, despite the small coating thickness employed.

  3. Role of the Fast Kinetics of Pyroglutamate-Modified Amyloid-β Oligomers in Membrane Binding and Membrane Permeability

    PubMed Central

    2015-01-01

    Membrane permeability to ions and small molecules is believed to be a critical step in the pathology of Alzheimer’s disease (AD). Interactions of oligomers formed by amyloid-β (Aβ) peptides with the plasma cell membrane are believed to play a fundamental role in the processes leading to membrane permeability. Among the family of Aβs, pyroglutamate (pE)-modified Aβ peptides constitute the most abundant oligomeric species in the brains of AD patients. Although membrane permeability mechanisms have been studied for full-length Aβ1–40/42 peptides, these have not been sufficiently characterized for the more abundant AβpE3–42 fragment. Here we have compared the adsorbed and membrane-inserted oligomeric species of AβpE3–42 and Aβ1–42 peptides. We find lower concentrations and larger dimensions for both species of membrane-associated AβpE3–42 oligomers. The larger dimensions are attributed to the faster self-assembly kinetics of AβpE3–42, and the lower concentrations are attributed to weaker interactions with zwitterionic lipid headgroups. While adsorbed oligomers produced little or no significant membrane structural damage, increased membrane permeabilization to ionic species is understood in terms of enlarged membrane-inserted oligomers. Membrane-inserted AβpE3–42 oligomers were also found to modify the mechanical properties of the membrane. Taken together, our results suggest that membrane-inserted oligomers are the primary species responsible for membrane permeability. PMID:24950761

  4. An atomic force microscopy study on fouling characteristics of modified PES membrane in submerged membrane bioreactor for domestic wastewater treatment

    NASA Astrophysics Data System (ADS)

    Liu, Shuo; Han, Hongjun; Liu, Yanping; Wang, Baozhen

    2008-10-01

    To investigate the fouling characteristics of modified PES membrane in submerged Membrane Bioreactor (MBR) for domestic wastewater treatment, Atomic Force Microscope (AFM) study was conducted to analyze the microstructure characteristics of PES membrane. Surface roughness and section analysis of both virgin and fouled membrane were achieved by software of NanoScope 6.12. Compared to the virgin membrane, the average roughness (Ra), square average roughness (Rms) and ten points average roughness (Rz) of fouled membrane were increased by 100.6nm, 133.7nm and 330.7nm respectively. The section analysis results indicated that the cake layer formed and membrane pore blocked were the main causes for the increase of TMP. Micro-filtration resistance analysis was conducted to support the results of AFM analysis. It is showed that membrane resistance, cake resistance, pore blocking and irreversible fouling resistance is 0.755, 1.721 and 1.386 respectively, which contributed 20%, 44%, and 36%, respectively, to total resistance of submerged MBR (at MLSS 6000mg/L and flux 21.9L/m2Â.h). The results proved that AFM could be used to properly describe the fouling characteristics of modified PES membrane in submerged MBR through roughness and section analysis.

  5. Ion-Transporting Composite Membranes. 3. Selectivity and Rate of Ion Transport in Nafion- (trade name) Impregnated Gore-Tex Membranes Prepared by a High Temperature Solution-Casting Method

    DTIC Science & Technology

    1990-08-02

    filtration membranes (20 nm and 200 nm mean pore diameter) were donated by W.L. Gore and Associates. Ru(NHO)OC13 was purchased from Johnson Mathey. Purified...the other terms have their usual meanings (15). According to Equation 2, a plot of Q(t) vs. t 0 ’ 5 will be linear; the product De.o𔃿a can be...6 3+ in the contacting solution phase, and the other terms have their usual meanings (7-9). According to Equation 3, a plot of i,,ŕ vs W-0. 5 will be

  6. Phosphoric acid doped polybenzimidazole/imidazolium-modified silsesquioxane hybrid proton conducting membranes for anhydrous proton exchange membrane application

    NASA Astrophysics Data System (ADS)

    Lin, Bencai; Chu, Fuqiang; Yuan, Ningyi; Shang, Hui; Ren, Yurong; Gu, Zongzong; Ding, Jianning; Wei, Yingqiang; Yu, Xiaomin

    2014-04-01

    Phosphoric acid doped polybenzimidazole (PBI)/imidazolium-modified silsesquioxane (Im-SiO3/2) hybrid membranes with high proton conductivity at high temperature under anhydrous conditions are synthesized and characterized. The presence of Im-SiO3/2 is confirmed by FT-IR and energy-dispersive X-ray spectroscopy (EDS) mapping of silicon element. The phosphoric acid uptake and proton conductivity of the hybrid membranes increase with the Im-SiO3/2 content, and the conductivity of PBI/Im-SiO3/2-20 reaching 6.3 × 10-2 S cm-1 at 180 °C. Compared with pure PBI membranes, the introduction of Im-SiO3/2 is effective in preventing the release of the phosphoric acid component from the hybrid membranes. The properties of the prepared hybrid membranes indicate their promising prospects in anhydrous proton exchange membrane applications.

  7. In situ thermal performance of APP modified bitumen roof membranes coated with reflective coatings

    SciTech Connect

    Carlson, J.D.; Smith, T.L. ); Christian, J.E. )

    1992-01-01

    A multi-faceted field research program regarding seven atactic polypropylene (APP) modified bitumen membrane roof systems and four reflective coatings began in 1991. This long-term project is evaluating the performance of various APP modified bitumen membranes (both coated and uncoated), the comparative performance of coating application soon after membrane installation versus preweathering, coating performance, and aspects of recoating. This paper is a progress report on the in situ thermal performance of the various types of coatings compared to the thermal performance of the exposed membrane. The thermal performance of an adjacent ballasted ethylene propylene diene terpolymer (EPDM) roofing system is also described.

  8. In situ thermal performance of APP modified bitumen roof membranes coated with reflective coatings

    SciTech Connect

    Carlson, J.D.; Smith, T.L.; Christian, J.E.

    1992-10-01

    A multi-faceted field research program regarding seven atactic polypropylene (APP) modified bitumen membrane roof systems and four reflective coatings began in 1991. This long-term project is evaluating the performance of various APP modified bitumen membranes (both coated and uncoated), the comparative performance of coating application soon after membrane installation versus preweathering, coating performance, and aspects of recoating. This paper is a progress report on the in situ thermal performance of the various types of coatings compared to the thermal performance of the exposed membrane. The thermal performance of an adjacent ballasted ethylene propylene diene terpolymer (EPDM) roofing system is also described.

  9. Development of a stable cation modified graphene oxide membrane for water treatment

    NASA Astrophysics Data System (ADS)

    Yu, Wenzheng; (Yet Yu, Tong; Graham, Nigel

    2017-12-01

    Membranes prepared from layers of graphene oxide (GO) offer substantial advantages over conventional materials for water treatment (e.g. greater flux), but the stability of GO membranes in water has not been achieved until now. In this study the behavior of GO membranes prepared with different quantities and species of cations has been investigated to establish the feasibility of their application in water treatment. A range of cation-modified GO membranes were prepared and exposed to aqueous solutions containing specific chemical constituents. In pure water, unmodified and Na-modified GO membranes were highly unstable, while GO membranes modified with multivalent cations were stable provided there were sufficient quantities of cations present; their relative capability to achieve GO stability was as follows: Al3+  >  Ca2+  >  Mg2+  >  Na+. It is believed that the mechanism of cross-linking, and membrane stability, is via metal-carboxylate chelates and cation-graphite surface interactions (cation-π interaction), and that the latter appears to increase with increasing cation valency. The instability of cation (Ca or Al)-modified GO membranes by NaCl solutions during permeation occurred as Na+ exchanged with the incorporated multivalent cations, but a high content of Al3+ in the GO membrane impeded Al3+/Na+ exchange and thus retained membrane stability. In solutions containing biopolymers representative of surface waters or seawater (protein and polysaccharide solutions), Ca-GO membranes (even with high Ca2+ content) were not stable, while Al-GO membranes were stable if the Al3+ content was sufficiently high; Al-formed membranes also had a greater flux than Ca-GO membranes.

  10. A method to modify PVDF microfiltration membrane via ATRP with low-temperature plasma pretreatment

    NASA Astrophysics Data System (ADS)

    Han, Yu; Song, Shuijun; Lu, Yin; Zhu, Dongfa

    2016-08-01

    The hydrophilic modification of a polyvinylidene fluoride (PVDF) microfiltration membrane via pretreatment with argon plasma and direct surface-initiated atom transfer radical polymerization (ATRP) was studied. Both modified and unmodified PVDF membranes were characterized by Fourier transform infrared spectroscopy (FTIR), water contact angle, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and pore size distribution measurements. FTIR and XPS spectra confirmed that sulfobetaine methacrylate (SBMA) had been grafted onto the membrane surface. The initial contact angle decreased from 87.0° to 29.8° and a water drop penetrated into the modified membrane completely in 8 s. The pore size distribution of the modified membrane exhibited a smaller mean value than that of the original membrane. The antifouling properties of the modified PVDF membrane were evaluated by a filtration test using bovine serum albumin (BSA) solution. The results showed that the initial flux of the modified membrane increased from 2140.1 L/m2 h to 2812.7 L/m2 h and the equilibrium flux of BSA solution increased from 31 L/m2 h to 53 L/m2 h.

  11. Performance of diatomite/iron oxide modified nonwoven membrane used in membrane bioreactor process for wastewater reclamation.

    PubMed

    He, Yueling; Zhang, Wenqi; Rao, Pinhua; Jin, Peng

    2014-01-01

    This study describes an approach for surface modification of a nonwoven membrane by diatomite/iron oxide to examine its filterability. Analysis results showed that nonwoven hydrophilicity is enhanced. Static contact angle decreases dramatically from 122.66° to 39.33°. Scanning electron micrograph images show that diatomite/iron oxide is attached on nonwoven fiber. X-ray diffraction analysis further proves that the compound is mostly magnetite. Fourier transformed infrared spectra results reveal that two new absorption peaks might be attributed to Si-O and Fe-O, respectively. Modified and original membranes were used in double nonwoven membrane bioreactors (MBRs) for synthetic wastewater treatment. High critical flux, long filtration time, slow trans-membrane pressure rise and stable sludge volume index confirmed the advantages of modified nonwoven. Comparing with original nonwoven, similar effluent qualities are achieved, meeting the requirements for wastewater reclamation.

  12. Zwitterionic glycosyl modified polyethersulfone membranes with enhanced anti-fouling property and blood compatibility.

    PubMed

    Xie, Yi; Li, Shuang-Si; Jiang, Xin; Xiang, Tao; Wang, Rui; Zhao, Chang-Sheng

    2015-04-01

    In this study, novel zwitterionic glycosyl modified polyethersulfone (PES) ultrafiltration membranes were prepared via in-situ cross-linking polymerization coupled with phase inversion technique, and the following reactions. The membranes were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), (1)HNMR spectrum, and static water contact angles (WCAs) measurements. The modified membranes showed excellent anti-fouling property, and the flux recovery ratio could reach almost 100%. Meanwhile, the blood compatibility of the membranes was measured by protein adsorption, platelet adhesion, activated partial thromboplastin time (APTT), and thrombin time (TT). The results implied that the zwitterionic glycosyl modified PES membranes had good anti-fouling property and blood compatibility.

  13. Development of a Nafion/MWCNT-SPCE-Based Portable Sensor for the Voltammetric Analysis of the Anti-Tuberculosis Drug Ethambutol

    PubMed Central

    Couto, Rosa A. S.; Quinaz, Maria Beatriz

    2016-01-01

    Herein we describe the development, characterization and application of an electrochemical sensor based on the use of Nafion/MWCNT-modified screen-printed carbon electrodes (SPCEs) for the voltammetric detection of the anti-tuberculosis (anti-TB) drug ethambutol (ETB). The electrochemical behaviour of the drug at the surface of the developed Nafion/MWCNT-SPCEs was studied through cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. Electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) were employed to characterize the modified surface of the electrodes. Results showed that, compared to both unmodified and MWCNTs-modified SPCEs, negatively charged Nafion/MWCNT-SPCEs remarkably enhanced the electrochemical sensitivity and selectivity for ETB due to the synergistic effect of the electrostatic interaction between cationic ETB molecules and negatively charged Nafion polymer and the inherent electrocatalytic properties of both MWCNTs and Nafion. Nafion/MWCNT-SPCEs provided excellent biocompatibility, good electrical conductivity, low electrochemical interferences and a high signal-to-noise ratio, providing excellent performance towards ETB quantification in microvolumes of human urine and human blood serum samples. The outcomes of this paper confirm that the Nafion/MWCNT-SPCE-based device could be a potential candidate for the development of a low-cost, yet reliable and efficient electrochemical portable sensor for the low-level detection of this antimycobacterial drug in biological samples. PMID:27376291

  14. Drug Delivery via Cell Membrane Fusion Using Lipopeptide Modified Liposomes

    PubMed Central

    2016-01-01

    Efficient delivery of drugs to living cells is still a major challenge. Currently, most methods rely on the endocytotic pathway resulting in low delivery efficiency due to limited endosomal escape and/or degradation in lysosomes. Here, we report a new method for direct drug delivery into the cytosol of live cells in vitro and invivo utilizing targeted membrane fusion between liposomes and live cells. A pair of complementary coiled-coil lipopeptides was embedded in the lipid bilayer of liposomes and cell membranes respectively, resulting in targeted membrane fusion with concomitant release of liposome encapsulated cargo including fluorescent dyes and the cytotoxic drug doxorubicin. Using a wide spectrum of endocytosis inhibitors and endosome trackers, we demonstrate that the major site of cargo release is at the plasma membrane. This method thus allows for the quick and efficient delivery of drugs and is expected to have many invitro, ex vivo, and invivo applications. PMID:27725960

  15. Absorption behavior of vanadium in Nafion®

    NASA Astrophysics Data System (ADS)

    Cho, Hyun-Seok; Ohashi, Masato; Van Zee, J. W.

    2014-12-01

    The absorption of vanadium to Nafion® was investigated through ex-situ isotherm and conductivity measurements at 23 °C. The data show a maximum loss of ion exchange capacity (IEC) of 30% for all four oxidation states of vanadium. The affinity of vanadium for N115 was measured by back titration and atomic absorption (AA) and characterized by isotherms at 23 °C, and the affinity is highest for the divalent species and lowest for the pentavalent species in the following order: VO2+ (V5+) < VO2+ (V4+) < V3+ < V2+. Steric hindrance from the associated water complex may explain the lower absorption of vanadium compared to alkali metals. The conductivity for the VO2+ (minimum affinity)-exchanged membrane was 2-3× lower than the sodium-exchanged membrane at an approximate RH = 100%.

  16. Enhancing the performance of nanofiltration membranes by modifying the active layer with aramide dendrimers.

    PubMed

    de Jubera, Ana M Saenz; Gao, Yuan; Moore, Jeffrey S; Cahill, David G; Mariñas, Benito J

    2012-09-04

    The fully aromatic polyamide active layer of a commercial nanofiltration membrane was modified with three generations (G1, G2, and G3) of aramide dendrimers, all with oligoethylene glycol chains on their peripheries. Permeation experiments revealed that the rejection of Rhodamine WT, used as a surrogate for organic contaminants, improved 1-2 orders of magnitude for membranes modified with G2 and G3 dendrimers at loadings of 0.7-3.5 μg/cm(2) (dendrimer layer thicknesses of ~1-6 nm) compared to the performance of unmodified membranes. In contrast, the corresponding water permeability of dendrimer-modified membranes decreased by only ~30%. Although an enhancement in the rejection of H(3)AsO(3), NaCl, and BaCl(2) was also observed for dendritic membranes, the effect was less pronounced than that for rhodamine WT. Characterization of membranes modified with 3.5 μg/cm(2) dendrimers G2 and G3 by Rutherford backscattering spectrometry with the aid of heavy ion probes (Ag(+) and Ba(2+)) revealed that accessibility of the larger Ba(2+) probe to carboxylate groups on the active layer decreased for the membranes modified with dendrimers.

  17. SEPARATION PROPERTIES OF SURFACE MODIFIED SILICA SUPPORTED LIQUID MEMBRANES FOR DIVALENT METAL REMOVAL/RECOVERY

    EPA Science Inventory

    The synthesis and separation properties of a mesoporous silica supported liquid membrane (SLM) were studied. The membranes consisted of a silica layer, from dip-coated colloidal silica, on a a-alumina support, modified with DCDMS (dichlorodimethyl silane) to add surface methyl g...

  18. Visualizing and quantifying the nanoscale hydrophobicity and chemical distribution of surface modified polyethersulfone (PES) membranes.

    PubMed

    Fu, Wanyi; Carbrello, Christina; Wu, Xiaosong; Zhang, Wen

    2017-10-06

    Chemical modifications bring unique properties into polymeric membranes that may have enhanced filtration or separation efficiencies, antifouling, antimicrobial activity and selectivity. However, there is a lack of nanoscale characterization of the chemical additive distribution and the impacts of chemical modifiers or additives on membrane surface properties, especially those at the nanoscale. In this study, a series of industrially relevant polyethersulfone (PES) membranes modified with poly (ethylene glycol) (PEG) and polyvinylpyrrolidone (PVP) were analysed systematically. Particularly, hydrophobicity and chemical distribution were scrutinized by atomic force microscopy (AFM) and AFM coupled with infrared analysis capability (AFM-IR) for the first time that successfully resolved nanoscale structural and chemical properties of the chemically modified PES membranes. Our results indicated the heterogeneous spatial distribution of PVP and PEG based on their characteristic IR bands and the resulting hydrophobicity distribution on modified membrane surfaces at the nanoscale. Particularly, we established a linear correlation (R(2) = 0.9449) between the measured adhesion force and water contact angles, which enabled the examination of local surface hydrophobicity. The PES membranes became more hydrophilic with the increasing blend of PVP and PEG. With AFM-IR, trace amounts (1-4%) of PVP could be identified sensitively on PES membranes based on their unique characteristic IR bands, which were not achieved by FTIR or IR mapping. Overall, these novel characterization approaches hold paramount importance for the design and quality control of polymer membrane modification and manufacturing.

  19. Polypiperazine-amide Nanofiltration Membrane Modified by Different Functionalized Multiwalled Carbon Nanotubes (MWCNTs).

    PubMed

    Xue, Shuang-Mei; Xu, Zhen-Liang; Tang, Yong-Jian; Ji, Chen-Hao

    2016-07-27

    In this work, three modified multiwalled carbon nanotubes (MWCNTs) with carboxyl (MWCNT-COOH), hydroxyl (MWCNT-OH) and amino groups (MWCNT-NH), respectively, were added into the aqueous phase containing piperazine (PIP) to fabricate the nanocomposite nanofiltration (NF) membranes via interfacial polymerization. The influences of functional groups of MWCNTs on the performance of modified NF membrane were investigated. The MWCNTs were characterized by TEM, FT-IR and TGA; meanwhile, the properties of the membranes were evaluated by XPS, TEM, AFM and contact angle. The XPS results proved the successful incorporation of MWCNT in the active layer of modified NF membrane. When the MWCNT concentration is 0.01% (w/v), all the nanocomposite membranes possessed the optimal separation properties, among which the membrane incorporated with MWCNT-OH demonstrated the highest water flux of 41.4 L·m(-2)·h(-1) and the Na2SO4 rejection of 97.6% whereas the one with MWCNT-COOH had the relative lowest rejection of 96.6%. Furthermore, the increased hydrophilicity of functional groups in modified MWCNTs resulted in different nodular surface morphologies, thicknesses and hydrophilicities of the nanocomposite membranes. All the membranes possessed a molecular weight cutoff (MWCO) within 300 Da and good operation stability.

  20. Vitamin E as a functional and biocompatibility modifier of synthetic hemodialyzer membranes: an overview of the literature on vitamin E-modified hemodialyzer membranes.

    PubMed

    Piroddi, Marta; Pilolli, Francesca; Aritomi, Masaharu; Galli, Francesco

    2012-01-01

    Along with one century of history, research has provided many solutions for hemodialysis (HD) biomaterials, encompassing several generations of copolymers that have found wide application in the development of hollow-fiber dialyzer membranes. Polysulfone-based biomaterials have gained increasing consideration and are now the gold standard in the production of biocompatible hemodialyzers. However, even the highest biocompatibility now available cannot exclude that dialyzer membranes and the overall extracorporeal circulation may produce at the subclinical level immunoinflammatory reactions and thus an increased cardiovascular risk of patients on regular HD therapy. The lipophilic antioxidant and radical scavenger vitamin E has been used (as α-tocopherol) to modify cellulosic and synthetic hollow-fiber membranes with the ultimate goal to neutralize harmful reactive species and to mimic lipid structures of blood cell plasmalemma and lipoprotein particles. Besides filtration and biocompatibility, this modifier has introduced a third function of dialyzer membranes, namely 'antioxidant bioactivity'. Vitamin E can also serve as a template molecule to produce synthetic redox-active and -silent (non-antioxidant) modifiers for future generations of dialyzer membranes. This mini-review article describes the evolution of vitamin E-derived copolymers as a generation of biomaterials that has offered a clinical challenge and still represents a chance to further improving the quality of HD therapy. Copyright © 2012 S. Karger AG, Basel.

  1. Evaluation of the oleophilicity of different alkoxysilane modified ceramic membranes through wetting dynamic measurements

    NASA Astrophysics Data System (ADS)

    Gao, Nengwen; Ke, Wei; Fan, Yiqun; Xu, Nanping

    2013-10-01

    Wettability has been recognized as one of the most important properties of porous materials for both fundamental and practical applications. In this study, the oleophilicity of Al2O3 membranes modified by four alkoxysilanes with different length of alkyl group was investigated through oil wetting dynamic test. Fourier transform infrared spectroscopy (FTIR), thermogravimertric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were measured to confirm that ceramic membrane surfaces have been grafted with alkoxysilanes without changing the membrane morphology. A high speed video camera was used to record the spreading and imbibition process of oil on the modified membrane surface. The value of oil contact angle and its change during the wetting process were used to characterize the membrane oleophilicity. Characterization results showed that the oleophilicity of the modified membranes increased along with the increasing of the silane alkyl group. The influence of oleophilicity on the filtration performance of water-in-oil (W/O) emulsions was experimentally studied. A higher oil flux was obtained for membranes grafted with a longer alkyl group, indicating that increase oleophilicity can increase the membrane antifouling property. This work presents a valuable route to the surface oleophilicity control and testing of ceramic membranes in the filtration of non-polar organic solvents.

  2. Polyrhodanine modified anodic aluminum oxide membrane for heavy metal ions removal.

    PubMed

    Song, Jooyoung; Oh, Hyuntaek; Kong, Hyeyoung; Jang, Jyongsik

    2011-03-15

    Polyrhodanine was immobilized onto the inner surface of anodic aluminum oxide (AAO) membrane via vapor deposition polymerization method. The polyrhodanine modified membrane was applied to remove heavy metal ions from aqueous solution because polyrhodanine could be coordinated with specific metal ions. Several parameters such as initial metal concentration, contact time and metal species were evaluated systematically for uptake efficiencies of the fabricated membrane under continuous flow condition. Adsorption isotherms of Hg(II) ion on the AAO-polyrhodanine membrane were analyzed with Langmuir and Freundlich isotherm models. The adsorption rate of Hg(II) ion on the membrane was obeyed by a pseudo-second order equation, indicating the chemical adsorption. The maximum removal capacity of Hg(II) ion onto the fabricated membrane was measured to be 4.2 mmol/g polymer. The AAO-polyrhodanine membrane had also remarkable uptake performance toward Ag(I) and Pb(II) ions. Furthermore, the polyrhodanine modified membrane could be recycled after recovery process. These results demonstrated that the polyrhodanine modified AAO membrane provided potential applications for removing the hazardous heavy metal ions from wastewater.

  3. Separation of macromolecular proteins and removal of humic acid by cellulose acetate modified UF membranes.

    PubMed

    Kanagaraj, P; Nagendran, A; Rana, D; Matsuura, T

    2016-08-01

    Surface modifying macromolecules (SMMs) were synthesized with various polyurethane pre polymers end-capped with different groups and blended into the casting solution of cellulose acetate (CA) to prepare surface modified ultra-filtration (UF) membranes for water filtration applications. The surface modification of the CA membranes was confirmed by the FTIR and static contact angle (SCA) measurements. The membranes so prepared had the typical characteristics of UF membranes as confirmed by scanning electron microscopy (SEM). Membrane properties were studied in terms of membrane compaction, percentage water content (%WC), pure water flux (PWF), membrane hydraulic resistance (Rm), molecular weight cut-off (MWCO), average pore size and porosity. The result showed that PWF, %WC, MWCO and pore size increased whereas the Rm decreased by the addition of SMMs. The significant effect of SMMs on the fouling by humic acid (HA) was also observed. It was found that the cSMM-3 membrane, in which SMM was synthesized with diethylene glycol (DEG) and hydroxyl benzene sulfonate (HBS) was blended, had the highest flux recovery ratio FRR (84.6%), as well as the lowest irreversible fouling (15.4%), confirming their improved antifouling properties. Thus, the SMM modified CA membranes had proven, to play an important role in the water treatment by UF.

  4. Comparing Nafion and ceramic separators used in electrochemical purification of spent chromium plating solutions: cationic impurity removal and transport.

    PubMed

    Huang, Kuo-Lin; Holsen, Thomas M; Chou, Tse-Chuan; Selman, J Robert

    2003-05-01

    This study focuses on the electrolytic regeneration of spent chromium plating solutions. These solutions contain a significant amount of chromium and a lesser amount of other heavy metals, which makes them a significant environmental concern and an obvious target for recycling and reuse. The type of separator used is extremely critical to the performance of the process because they are the major resistance in the transport-related impurity (Cu(II), Ni(II), and Fe(III)) removals from contaminated chromic acid solutions. A Nafion 117 membrane and a ceramic diaphragm separator traditionally used in the industry were tested for comparison. It was found that the mobilities of Cu(II) and Ni(II) were similar and higher than that of Fe(III) using both separators. The mobility of each cation was smaller in the Nafion membrane than in the ceramic diaphragm. The measured conductivity of the ceramic diaphragm was slightly higher than that of Nafion membrane. However, the Nafion membrane was much thinner than the ceramic diaphragm resulting in the system using the Nafion membrane having higher impurity removal rates than the system using the ceramic diaphragm. The removal rates were approximately equal for Cu(II) and Ni(II) and lowest for Fe(III). Both current and initial concentration affected the removal rates of the impurities. Modeling results indicated that a system using a Nafion separator and a small catholyte/anolyte volume ratio was better than a system using a ceramic separator for removing impurities from concentrated plating solutions if the impurities transported into the catholyte are deposited or precipitated.

  5. A Study of the Effect of Heat-Treatment on the Morphology of Nafion Ionomer Dispersion for Use in the Passive Direct Methanol Fuel Cell (DMFC)

    PubMed Central

    Yuan, Ting; Zhang, Haifeng; Zou, Zhiqing; Khatun, Sufia; Akins, Daniel; Adam, Yara; Suarez, Sophia

    2012-01-01

    Aggregation in heat-treated Nafion ionomer dispersion and 117 membrane are investigated by 1H and 19F Nuclear Magnetic Resonance (NMR) spectra, spin-lattice relaxation time, and self-diffusion coefficient measurements. Results demonstrate that heat-treatment affects the average Nafion particle size in aqueous dispersions. Measurements on heat-treated Nafion 117 membrane show changes in the 1H isotropic chemical shift and no significant changes in ionic conductivity. Scanning electron microscopy (SEM) analysis of prepared cathode catalyst layer containing the heat-treated dispersions reveals that the surface of the electrode with the catalyst ink that has been pretreated at ca. 80 °C exhibits a compact and uniform morphology. The decrease of Nafion ionomer’s size results in better contact between catalyst particles and electrolyte, higher electrochemically active surface area, as well as significant improvement in the DMFC’s performance, as verified by electrochemical analysis and single cell evaluation. PMID:24958431

  6. Surface-modified anodic aluminum oxide membrane with hydroxyethyl celluloses as a matrix for bilirubin removal.

    PubMed

    Xue, Maoqiang; Ling, Yisheng; Wu, Guisen; Liu, Xin; Ge, Dongtao; Shi, Wei

    2013-01-01

    Microporous anodic aluminum oxide (AAO) membranes were modified by 3-glycidoxypropyltrimethoxysilane to produce terminal epoxy groups. These were used to covalently link hydroxyethyl celluloses (HEC) to amplify reactive groups of AAO membrane. The hydroxyl groups of HEC-AAO composite membrane were further modified with 1,4-butanediol diglycidyl ether to link arginine as an affinity ligand. The contents of HEC and arginine of arginine-immobilized HEC-AAO membrane were 52.1 and 19.7mg/g membrane, respectively. As biomedical adsorbents, the arginine-immobilized HEC-AAO membranes were tested for bilirubin removal. The non-specific bilirubin adsorption on the unmodified HEC-AAO composite membranes was 0.8mg/g membrane. Higher bilirubin adsorption values, up to 52.6mg/g membrane, were obtained with the arginine-immobilized HEC-AAO membranes. Elution of bilirubin showed desorption ratio was up to 85% using 0.3M NaSCN solution as the desorption agent. Comparisons equilibrium and dynamic capacities showed that dynamic capacities were lower than the equilibrium capacities. In addition, the adsorption mechanism of bilirubin and the effects of temperature, initial concentration of bilirubin, albumin concentration and ionic strength on adsorption were also investigated.

  7. Modified cationic membranes for water purification, and their selective permeability

    NASA Astrophysics Data System (ADS)

    Mavrin, G. V.; Fasullin, D. D.; Melkolvan, R. G.

    2014-12-01

    Wastewater containing heavy metal ions pose a significant toxicological risk to aquatic ecosystems and humans. The common problem of modern engineering technology is the development of environmentally friendly systems with a closed-circuit and a minimum waste. The ion exchange membrane can significantly reduce the cost of wastewater treatment and provide a high degree of purification.

  8. Surface-modified zeolite-filled chitosan membranes for pervaporation dehydration of ethanol

    NASA Astrophysics Data System (ADS)

    Sun, Honglei; Lu, Lianyu; Chen, Xue; Jiang, Zhongyi

    2008-06-01

    Surface-modified zeolite-filled chitosan (CS) membranes were prepared by incorporating 3-mercaptopropyltrimethoxysilane (MPTMS)-modified H-ZSM-5 zeolite into chitosan for pervaporation dehydration of aqueous ethanol solution. The physicochemical characterization by XPS, FT-IR, XRD, DMA and SEM showed that -SO 3H group was readily grafted on the surface of H-ZSM-5 with the mediation of MPTMS and hydrogen peroxide, and the accompanying ion-ion interaction between -SO 3H group on surface-modified H-ZSM-5 and -NH 3+ group on chitosan substantially eliminated the nonselective voids at the chitosan-H-ZSM-5 interface of the filled membranes. The experimental results also revealed that H-ZSM-5 exhibited desirable size-selective and preferential adsorption effects for aqueous ethanol solution. As a result, modified H-ZSM-5 filled membranes showed higher swelling degree and permeation flux, and improved selectivity for aqueous ethanol solution. In comparison between chitosan control membrane (permeation flux 54.18 g/(m 2 h) and separation factor 158.02 for 90 wt.% aqueous ethanol solution at 80 °C), the modified H-ZSM-5 filled membrane with 8 wt.% filling content exhibited a remarkably improved pervaporation performance with permeation flux 278.54 g/(m 2 h) and separation factor 274.46 under the identical experimental condition.

  9. Deposition of polymeric perfluored thin films in proton ionic membranes by plasma processes

    NASA Astrophysics Data System (ADS)

    Polak, Peter Lubomir; Mousinho, Ana Paula; Ordonez, Nelson; da Silva Zambom, Luis; Mansano, Ronaldo Domingues

    2007-10-01

    In this work the surfaces of polymeric membranes based on Nafion (proton conducting material), used in proton exchange membranes fuel cells (PEMFC) had been modified by plasma deposition of perfluored polymers, in order to improve its functioning in systems of energy generation (fuel cells). The deposition increases the chemical resistance of the proton ionic polymers without losing the electrical properties. The processing of the membranes also reduces the permeability of the membranes to the alcohols (methanol and ethanol), thus preventing poisoning of the fuel cell. The processing of the membranes of Nafion was carried through in a system of plasma deposition using a mixture of CF 4 and H 2 gases. The plasma processing was made mainly to increase the chemical resistance and result in hydrophobic surfaces. The Fourier transformed infrared (FTIR) technique supplies a spectrum with information about the CF n bond formation. Through the Rutherford back scattering (RBS) technique it was possible to verify the deposition rate of the polymeric layer. The plasma process with composition of 60% of CF 4 and 40% of H 2 presented the best deposition rate. By the spectrum analysis for the optimized configuration, it was possible to verify that the film deposition occurred with a thickness of 90 nm, and fluorine concentration was nearly 30%. Voltammetry made possible to verify that the fluorination increases the membranes chemical resistance, improving the stability of Nafion, becoming an attractive process for construction of fuel cells.

  10. Improved antifouling properties of PVDF membranes modified with oppositely charged copolymer.

    PubMed

    Shen, Xiang; Zhao, Yiping; Feng, Xia; Bi, Sixin; Ding, Wenbin; Chen, Li

    2013-01-01

    Biofouling resulting from the attachment of microorganisms communities to the membrane surface is the major obstacle for the widespread application of membrane technology. This work develops a feasible approach to prepare an anti-biofouling poly(vinylidene fluoride) (PVDF) membrane. A copolymer that possessed oppositely charged groups was first synthesized via radical copolymerization with methyl methacrylate, 2-methacryloxy ethyltrimethyl ammonium chloride and 2-acrylamide-2-methyl propane sulphonic acid as monomers. The copolymer was blended with the PVDF powder to prepare the antifouling membrane via the immersed phase inversion method. The antifouling properties of the modified PVDF membrane were studied by X-ray photoelectron spectroscopy, field emission scanning electron microscopy, water contact angle measurement, zeta-potential measurement, protein adsorption, microbial adhesion and filtration experiments. The modified PVDF membrane showed limited adsorption and adhesion of protein bovine serum albumin and microbes (Escherichia coli and Saccharomyces cerevisiae) with increasing copolymer concentration in the casting solution. The modified PVDF membrane exhibited excellent antibiofouling properties.

  11. Do membrane lipids modify the ouabain-sensitivity of cardiac (Na,K)ATPase?

    PubMed

    Hegyvary, C; Chigurupati, R; Mahoney, D

    1981-02-01

    We investigated whether membrane lipids can alter the affinity of cardiac (Na,K)ATPase (ATP phosphohydrolase, EC 3.6.1.6) for ouabain. We recombined partially (80-95%) delipidated membrane proteins from a digitalis-sensitive species (dog) with membrane lipids from a relatively digitalis-insensitive species (rat) or vice versa, and estimated the affinity of (Na,K)ATPase for ouabain in these hybrid membranes by measuring the half-maximal inhibitory concentration (I50). Delipidation reduced the enzyme activity by 90-95%, but 40-60% of the original activity could be restored with lipids from the same or from the other species and distribution of [14C]phosphatidylcholine showed complete mixing between the native and foreign lipids. In these hybrid cardiac membranes affinity (I50) for ouabain was determined by the origin of the (Na,K)ATPase protein and was not modified by the change in membrane lipids.

  12. Reverse osmosis performance of modified polyvinyl alcohol thin-film composite membranes

    SciTech Connect

    Lang, K.; Chowdhury, G.; Matsuura, T.; Sourirajan, S. )

    1994-08-01

    Membrane separation characteristics in the nanofiltration (NF) and reverse osmosis (RO) regions of the filtration spectrum are governed by a complex combination of both steric hindrance and surface force interactions. NF and RO membranes having surface charges show unusual selectivity behavior not predicted on the basis of physical pore size alone. Hence, practical characterizations should employ techniques to gain insight on membrane function. In this work, the separation characteristics of an anionically charged modified polyvinyl alcohol (PVA) thin-film composite membrane under different operating pressures were investigated. A qualitative measurement of the surface force interactions between solutes and membrane polymer was conducted using liquid chromatography technique. An attempt was also made to study the chlorine resistance of the composite membrane.

  13. Fundamental studies into zirconium modified phosphonic acid based ionic membranes

    NASA Astrophysics Data System (ADS)

    Schlichting, Gregory Joseph

    The demand for a sustainable energy economy requires the development of new solid stare electrochemical energy conversion devices. Ionic membranes are the bases for most of these devices. Solid super acids based on zirconium phosphonates show great promise for development into these membranes. Copolymers of vinyl phosphonic acid with zirconium vinyl phosphonate have been synthesized via UV free radical polymerization from immiscible mixtures into amorphous, transparent, water stable, flexible membranes. Ion exchange capacities range from 6 to 10 meq/g corresponding to equivalent weights well below 200 g/mol. A 20wt% loading of the VZP co-monomer is XRD amorphous. It is shown that 1.5 of the 2 protons in the beginning acidic groups are dissociated in the 20wt% VZP loaded ionomer allowing these materials to have high proton conductivities, up to and exceeding 0.1 S cm^-1 at 80°C and 80%RH. Water uptake measurementsshow very little swelling of the material below 70%RH and ca. 1 water per proton at low RH. Proton conductivity under dry conditions, roughly 0.05 S cm-1 with a lambda < 1, indicates that the material conducts protons under limiting hydration conditions and strongly implicates transport by a pure Grotthuss mechanism. Through this work, it has been demonstrated that zirconium vinyl phosphonate can, in fact, be dispersed and incorporated into a polymer to create new, hybrid organic-inorganic ionomers. High conductivities over 0.15 S/cm have been shown for multiple formulations of these ionomers, which is approaching conductivities that are comparable to liquid and molten phosphoric and phosphonic acids. Phosphonic acid functionalization yielded high proton conductivities, however the increased ionic character rendered the ionomer vulnerable to attack from water. Annealing provides a rise in conductivity at 150 degrees Celsius, but shows decreases after heating to 175 degrees Celsius, where the ionomer is obviously starting to degrade.

  14. [Regeneration of corneal epithelium using keratin modified chitosan membranes].

    PubMed

    Grolik, Maria; Kopeć, Maciej; Szczubiałka, Krzysztof; Wowra, Bogumił; Dobrowolski, Dariusz; Wylegała, Edward; Nowakowska, Maria

    2012-01-01

    The cornea is a transparent front layer of the eye. It functions like a window that controls and focuses the light entering into the eye. The cornea contributes to 65-75% of the eye's total focusing power and it acts as a physical barrier against pathogenic microorganisms, dirt and other noxious physical factors. The corneal tissue is arranged in five basic layers. The outermost layer (epithelium) is made up of highly regenerative cells that allow for quick healing of superficial injuries. Eye infections, diseases, or mechanical injury can harm corneal epithelium and cause blindness. Under certain circumstances, to prevent that, it is recommended to perform complete corneal transplantation. However, due to lack of sufficient number of donors, researchers are searching for alternative solutions.. Regeneration of epidermal tissue can restore and ensure normal functioning of cornea. For that purpose proper grafts are needed. The goal of current research was to develop the material for scaffold preparation providing optimal conditions for the epithelium cornea cell culturing and to determine its chemical, physical, and biological properties. The scaffolds, which could be applied in ophthalmology should fulfill a lot of requirements, among them such as biocompatibility, biodegradability, restorability, non-toxicity. They should also have adequate mechanical strength, flexibility and porosity. The aim of this work was to synthesize and to determine the properties of polymeric material for ophthalmic surgery applications. A hydrogel scaffold in the form of membrane was obtained from chitosan - natural, biocompatible, biologically inert, stable in the natural environmental and antibacterial polysaccharide derived from chitin. Biodegradable chitosan films containing keratin were crosslinked with genipin - a naturally occurring and nontoxic agent. In this study we present physicochemical characterization of the scaffolds. Porosity, contact angle and swelling ratio (at

  15. Characterization of cellulose membranes modified with luminescent silicon quantum dots nanoparticles.

    PubMed

    Campos, B B; Gelde, L; Algarra, M; Esteves da Silva, J C G; Vázquez, M I; Benavente, J

    2016-10-20

    A highly hydrophilic planar membrane fabricated with regenerated cellulose (RC-4 membrane), a biocompatible polymer, was modified by inclusion of water-soluble silicon quantum dot nanoparticles (SiQDs). Both bare SiQDs and SiQDs coated with a PAMAM-OH dendrimer were employed in order to obtain luminescent and thermally stable membrane systems (RC-4/SiQDs and RC-4/SiQDs-PAMAM-OH membranes). Original and SiQDs-modified membranes were characterized by fluorescence spectroscopy (steady and confocal), derivative thermogravimetric analysis and impedance spectroscopy measurements. According to these results, both SiQDs-regenerated cellulose composite membranes present luminescent character as well as higher thermal resistance and conductivity than the original sample, although the dendrimer coverage of the SiQDs might partially shield such effects. Moreover, the permanence of SiQDs nanoparticles in the structure of the cellulosic support in aqueous environments and their effect on diffusive transport were determined by water uptake as well as by membrane potential measurements at different concentrations of a model electrolyte (KCl). These results demonstrate the possible use of these stable nano-engineered membranes, which are based on SiQDs nanoparticles, in electrochemical devices under flow conditions.

  16. The heat-modifiable outer membrane protein of Actinobacillus actinomycetemcomitans: relationship to OmpA proteins.

    PubMed Central

    Wilson, M E

    1991-01-01

    The outer membrane of Actinobacillus actinomycetemcomitans contains a 29-kDa protein which exhibits heat modifiability on sodium dodecyl sulfate-polyacrylamide gels and represents a major target for immunoglobulin G antibody in sera of periodontitis patients colonized by this organism. In the present study, the N-terminal amino acid sequence of the 29-kDa outer membrane protein was determined and compared with reported sequences for other known proteins. The heat-modifiable outer membrane protein of A. actinomycetemcomitans was found to exhibit significant N-terminal homology with the OmpA proteins of other gram-negative bacteria. Moreover, this protein reacted with antiserum raised against the purified OmpA protein of Escherichia coli K-12. Whether the heat-modifiable OMP of A. actinomycetemcomitans also shares functional properties of OmpA proteins, particularly with respect to bacteriophage receptor activity, is presently under investigation. Images PMID:2050416

  17. Effects of fluid flow on elution of hydrophilic modifier from dialysis membrane surfaces.

    PubMed

    Matsuda, Masato; Sato, Mika; Sakata, Hiroki; Ogawa, Takahisa; Yamamoto, Ken-ichiro; Yakushiji, Taiji; Fukuda, Makoto; Miyasaka, Takehiro; Sakai, Kiyotaka

    2008-01-01

    When uremic blood flows through dialyzers during hemodialysis, dialysis membrane surfaces are exposed to shear stress and internal filtration, which may affect the surface characteristics of the dialysis membranes. In the present study, we evaluated changes in the characteristics of membrane surfaces caused by shear stress and internal filtration using blood substitutes: water purified by reverse osmosis and 6.7 wt% dextran70 solution. We focused on the levels of a hydrophilic modifier, polyvinylpyrrolidone (PVP), on the membrane surface measured by attenuated total reflectance Fourier transform infrared spectroscopy. Experiments involving 4 h dialysis, 0-144 h shear-stress loading, and 4 h dead-end filtration were performed using polyester-polymer alloy (PEPA) and polysulfone (PS) membranes. After the dialysis experiments with accompanying internal filtration, average PVP retention on the PEPA membrane surface was 93.7% in all areas, whereas that on the PS membrane surface was 98.9% in all areas. After the shear-stress loading experiments, PVP retention on the PEPA membrane surface decreased as shear-stress loading time and the magnitude of shear stress increased. However, with the PS membrane, PVP retention scarcely changed. After the dead-end filtration experiments, PVP retention decreased in all areas for both PEPA and PS membranes, but PVP retention on the PEPA membrane surface was lower than that on the PS membrane surface. PVP on the PEPA membrane surface was eluted by both shear stress and internal filtration, while that on the PS membrane surface was eluted only by internal filtration.

  18. Effect of Modified Phospholipid Bilayers on the Electrochemical Activity of a Membrane-Spanning Conjugated Oligoelectrolyte.

    PubMed

    Jahnke, Justin P; Bazan, Guillermo C; Sumner, James J

    2015-10-27

    The incorporation and electrochemical activity of a conjugated oligoelectrolyte (COE) in model phospholipid bilayers have been characterized using cyclic voltammetry and UV-vis absorption measurements. Several other modifiers were also incorporated into the phospholipid membranes to alter properties such as charge and alkyl chain disorder. Using potassium ferricyanide to measure charge transport, it was observed that bilayers that contained cholic acid, a negatively charged additive that also promotes alkyl chain disorder, had higher COE uptake and charge permeability than unmodified bilayers. In contrast, when the positively charged choline was incorporated, charge permeability decreased and COE uptake was similar to that of unmodified bilayers. The incorporation of cholesterol at low concentrations within the phospholipid membranes was shown to enhance the COE's effectiveness at increasing membrane charge permeability without increasing the COE concentration in the bilayer. Higher concentrations of cholesterol reduce membrane fluidity and membrane charge permeability. Collectively, these results demonstrate that changes in phospholipid membrane charge permeability upon COE incorporation depend not only on the concentration in the membrane but also on interactions with the phospholipid bilayer and other additives present in the membranes. This approach of manipulating the properties of phospholipid membranes to understand COE interactions is applicable to understanding the behavior of a wide range of molecules that impart useful properties to phospholipid membranes.

  19. Local anesthetics structure-dependently interact with anionic phospholipid membranes to modify the fluidity.

    PubMed

    Tsuchiya, Hironori; Ueno, Takahiro; Mizogami, Maki; Takakura, Ko

    2010-01-05

    While bupivacaine is more cardiotoxic than other local anesthetics, the mechanistic background for different toxic effects remains unclear. Several cardiotoxic compounds act on lipid bilayers to change the physicochemical properties of membranes. We comparatively studied the interaction of local anesthetics with lipid membranous systems which might be related to their structure-selective cardiotoxicity. Amide local anesthetics (10-300 microM) were reacted with unilamellar vesicles which were prepared with different phospholipids and cholesterol of varying lipid compositions. They were compared on the potencies to modify membrane fluidity by measuring fluorescence polarization. Local anesthetics interacted with liposomal membranes to increase the fluidity. Increasing anionic phospholipids in membranes enhanced the membrane-fluidizing effects of local anesthetics with the potency being cardiolipin>phosphatidic acid>phosphatidylglycerol>phosphatidylserine. Cardiolipin was most effective on bupivacaine, followed by ropivacaine. Local anesthetics interacted differently with biomimetic membranes consisting of 10mol% cardiolipin, 50mol% other phospholipids and 40mol% cholesterol with the potency being bupivacaine>ropivacaine>lidocaine>prilocaine, which agreed with the rank order of cardiotoxicity. Bupivacaine significantly fluidized 2.5-12.5mol% cardiolipin-containing membranes at cardiotoxicologically relevant concentrations. Bupivacaine is considered to affect lipid bilayers by interacting electrostatically with negatively charged cardiolipin head groups and hydrophobically with phospholipid acyl chains. The structure-dependent interaction with lipid membranes containing cardiolipin, which is preferentially localized in cardiomyocyte mitochondrial membranes, may be a mechanistic clue to explain the structure-selective cardiotoxicity of local anesthetics.

  20. Morphology Effect on Proton Dynamics in Nafion® 117 and Sulfonated Polyether Ether Ketone

    NASA Astrophysics Data System (ADS)

    Leong, Jun Xing; Diño, Wilson Agerico; Ahmad, Azizan; Daud, Wan Ramli Wan; Kasai, Hideaki

    2016-09-01

    We report results of our experimental and theoretical studies on the dynamics of proton conductivity in Nafion® 117 and self-fabricated sulfonated polyether ether ketone (SPEEK) membranes. Knowing that the presence of water molecules in the diffusion process results in a lower energy barrier, we determined the diffusion barriers and corresponding tunneling probabilities of Nafion® 117 and SPEEK system using a simple theoretical model that excludes the medium (water molecules) in the initial calculations. We then propose an equation that relates the membrane conductivity to the tunneling probability. We recover the effect of the medium by introducing a correction term into the proposed equation, which takes into account the effect of the proton diffusion distance and the hydration level. We have also experimentally verified that the proposed equation correctly explain the difference in conductivity between Nafion® 117 and SPEEK. We found that membranes that are to be operated in low hydration environments (high temperatures) need to be designed with short diffusion distances to enhance and maintain high conductivity.

  1. Boehmite particle coating modified microporous polyethylene membrane: A promising separator for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Yang, Chongwen; Tong, Hua; Luo, Chuanpeng; Yuan, Shuanglong; Chen, Guorong; Yang, Yunxia

    2017-04-01

    To exploit high-quality separators for lithium ion batteries, current research activities are mainly focused on the modification of microporous polyolefin membranes by coating them with inorganic particles to achieve comprehensive improvements in their thermal stability, electrochemical compatibility, and overcharge protection. Here, we report a separator made by coating boehmite (AlOOH) particles on microporous polyethylene (PE) membranes. Compared to the commercially applied coating materials, e.g., aluminum oxide (Al2O3), AlOOH allows for a substantial reduction in the coating thickness, while ensuring excellent thermal stability of the modified PE membrane. Our study shows that this is due to the formation of an interlocking interface structure that interconnects the PE membrane and AlOOH coating layer as soon as PE melts at about 140 °C, preventing the modified PE membrane from shrinking at subsequently elevated temperatures. The modified PE membrane exhibits suitable electrolyte wettability to facilitate ion transport through it. Thus, the lithium ion batteries employing it as a separator could attain substantially improved electrochemical performance. Furthermore, the AlOOH-coated PE separator was also found to provide an excellent overcharge protection.

  2. a Novel Method to Synthesize N-DOPED CNTs Arrays via Chemical Modifying Porous Alumina Membrane

    NASA Astrophysics Data System (ADS)

    Li, Chengyong; He, Lei

    2014-01-01

    N-doped carbon nanotubes (CNTs) arrays were fabricated via simply chemical modifying porous alumina membrane (PAM) with dopamine. The diameter of N-doped CNTs is about 60-70 nm. The N/C atomic ratio is calculated to be 0.05 and the main functionality is pyridone/pyrrole N. This chemical modifying method can be used to fabricate mass of N-doped CNTs arrays in one step with single raw material.

  3. Proteomes of Host Cell Membranes Modified by Intracellular Activities of Salmonella enterica*

    PubMed Central

    Vorwerk, Stephanie; Krieger, Viktoria; Deiwick, Jörg; Hensel, Michael; Hansmeier, Nicole

    2015-01-01

    Intracellular pathogens need to establish a growth-stimulating host niche for survival and replication. A unique feature of the gastrointestinal pathogen Salmonella enterica serovar Typhimurium is the creation of extensive membrane networks within its host. An understanding of the origin and function of these membranes is crucial for the development of new treatment strategies. However, the characterization of this compartment is very challenging, and only fragmentary knowledge of its composition and biogenesis exists. Here, we describe a new proteome-based approach to enrich and characterize Salmonella-modified membranes. Using a Salmonella mutant strain that does not form this unique membrane network as a reference, we identified a high-confidence set of host proteins associated with Salmonella-modified membranes. This comprehensive analysis allowed us to reconstruct the interactions of Salmonella with host membranes. For example, we noted that Salmonella redirects endoplasmic reticulum (ER) membrane trafficking to its intracellular niche, a finding that has not been described for Salmonella previously. Our system-wide approach therefore has the potential to rapidly close gaps in our knowledge of the infection process of intracellular pathogens and demonstrates a hitherto unrecognized complexity in the formation of Salmonella host niches. PMID:25348832

  4. Temperature dependence of the electrode kinetics of oxygen reduction at the platinum/Nafion interface - A microelectrode investigation

    NASA Technical Reports Server (NTRS)

    Parthasarathy, Arvind; Srinivasan, Supramanian; Appleby, A. J.; Martin, Charles R.

    1992-01-01

    Results of a study of the temperature dependence of the oxygen reduction kinetics at the Pt/Nafion interface are presented. This study was carried out in the temperature range of 30-80 C and at 5 atm of oxygen pressure. The results showed a linear increase of the Tafel slope with temperature in the low current density region, but the Tafel slope was found to be independent of temperature in the high current density region. The values of the activation energy for oxygen reduction at the platinum/Nafion interface are nearly the same as those obtained at the platinum/trifluoromethane sulfonic acid interface but less than values obtained at the Pt/H3PO4 and Pt/HClO4 interfaces. The diffusion coefficient of oxygen in Nafion increases with temperature while its solubility decreases with temperature. These temperatures also depend on the water content of the membrane.

  5. Pressure dependence of the oxygen reduction reaction at the platinum microelectrode/nafion interface - Electrode kinetics and mass transport

    NASA Technical Reports Server (NTRS)

    Parthasarathy, Arvind; Srinivasan, Supramaniam; Appleby, A. J.; Martin, Charles R.

    1992-01-01

    The investigation of oxygen reduction kinetics at the platinum/Nafion interface is of great importance in the advancement of proton-exchange-membrane (PEM) fuel-cell technology. This study focuses on the dependence of the oxygen reduction kinetics on oxygen pressure. Conventional Tafel analysis of the data shows that the reaction order with respect to oxygen is unity at both high and low current densities. Chronoamperometric measurements of the transport parameters for oxygen in Nafion show that oxygen dissolution follows Henry's isotherm. The diffusion coefficient of oxygen is invariant with pressure; however, the diffusion coefficient for oxygen is lower when air is used as the equilibrating gas as compared to when oxygen is used for equilibration. These results are of value in understanding the influence of O2 partial pressure on the performance of PEM fuel cells and also in elucidating the mechanism of oxygen reduction at the platinum/Nafion interface.

  6. Preparation of poly(acrylic acid) modified polyurethane membrane for biomaterial by UV radiation without degassing.

    PubMed

    Yang, J M; Huang, M J; Yeh, T S

    1999-05-01

    Poly(acrylic acid) modified polyurethane (AA/PU) membranes were prepared by UV radiation without degassing. The chemical composition of the AA/PU membrane was studied by IR spectroscopy. In addition to those absorption peaks associated with pure PU, the absorption peak at 2400 cm-1 of poly(AA) was also found. The morphology of AA/PU membrane was studied by optical polarizing microscopy. We also measured the glass transition temperature and the decomposition temperature of the AA/PU membrane by differential scanning calorimetry and thermogravimetric analysis. A significant domain was found in the AA/PU membrane, which resulted in different glass transition temperature and decomposition temperature between AA/PU and pure PU membrane. The effect of AA content on the contact angle and water absorption of the AA/PU membrane was determined. It was found that the water content of AA/PU membrane increased with increasing AA content, whereas the contact angle decreased. By using Kaeble's equation and the contact angle data, the surface free energy of AA/PU membrane was determined. The increase of surface free energy resulted from the increase of the dispersion (gammad) term and polar (gammap) term. In order to evaluate the biocompatibility of these membranes, a cytotoxicity test and a cell adhesion and proliferation assay were conducted in cell culture. Immortal cells and primary lymphocytes were both used in this study. The results showed that these AA/PU membranes exhibited very low cytotoxicity and could support cell adhesion and growth. An animal primary test was also done in this study. It was found that the AA/PU membrane could possibly be employed in the treatment of bowel defect. Copyright 1999 John Wiley & Sons, Inc.

  7. Modified by air plasma polymer tack membranes as drainage material for antiglaucomatous operations

    NASA Astrophysics Data System (ADS)

    Ryazantseva, T. V.; Kravets, L. I.; Elinson, V. M.

    2014-06-01

    The morphological and clinical studies of poly(ethylene terephthalate) track membranes modified by air plasma as drainage materials for antiglaucomatous operations were performed. It was demonstrated their compatibility with eye tissues. Moreover, it was shown that a new drainage has a good lasting hypotensive effect and can be used as operation for refractory glaucoma surgery.

  8. Production of bacterial cellulose membranes in a modified airlift bioreactor by Gluconacetobacter xylinus.

    PubMed

    Wu, Sheng-Chi; Li, Meng-Hsun

    2015-10-01

    In this study, a novel bioreactor for producing bacterial cellulose (BC) is proposed. Traditional BC production uses static culture conditions and produces a gelatinous membrane. The potential for using various types of bioreactor, including a stirred tank, conventional airlift, and modified airlift with a rectangular wire-mesh draft tube, in large-scale production has been investigated. The BC obtained from these bioreactors is fibrous or in pellet form. Our proposed airlift bioreactor produces a membrane-type BC from Gluconacetobacter xylinus, the water-holding capacity of which is greater than that of cellulose types produced using static cultivation methods. The Young's modulus of the product can be manipulated by varying the number of net plates in the modified airlift bioreactor. The BC membrane produced using the proposed bioreactor exhibits potential for practical application. Copyright © 2015 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  9. Study of antifouling modified ultrafiltration membrane based on the secondary treated water of urban sewage.

    PubMed

    Meng, Xiao-rong; Zhao, Liang; Wang, Lei; Wang, Xu-dong; Huang, Dan-xi; Miao, Rui

    2012-01-01

    Mixtures of polyvinylidene fluoride (PVDF) and polyvinyl alcohol (PVA) containing hydrophilic ultrafiltration membranes were prepared by adding PVA (5 to 30%) to PVDF by the phase inversion method. The hydrophilic contact angle (CA), equilibrium water content, pure water flux and bovine serum albumin retention were studied to assess the membrane performance. The anti-fouling performance of modified membrane to the secondary treated water was evaluated by flux decline, washing recovery rate and fouling resistance analysis. Scanning electron microscopy showed that the cross-section structure of the membranes had finger-like pores, which were well developed and uniformly distributed, and the sub-layer structure was looser and more porous with the increasing content of PVA. The CA gradually decreased. The steady flux was 800 L/m(2) h from P15 to P30, and the BSA retention sharply declined. The ultrafiltration tests for secondary treated water indicated that the main fouling source of the modified membrane was the concentration polarization and cake layer resistance. After physical flushing, the flux recovery ratio of the membrane could reach 100% when the PVA content was 5-15%, which shows excellent anti-pollution performance and good prospects for use in processing wastewater from urban sewage.

  10. In vitro evaluation of antioxidant and anti-inflammatory properties of genistein-modified hemodialysis membranes.

    PubMed

    Neelakandan, Chandrasekaran; Chang, Teng; Alexander, Thomas; Define, Linda; Evancho-Chapman, Michelle; Kyu, Thein

    2011-07-11

    Genistein-modified poly(amide):poly(vinyl pyrrolidone) (PA:PVP/G) hemodialysis membranes have been fabricated by coagulation via solvent (dimethyl sulfoxide, DMSO)/nonsolvent (water) exchange. The antioxidant and anti-inflammatory properties of the unmodified PA:PVP membranes were evaluated in vitro using human blood. It was found that these unmodified PA:PVP membranes were noncytotoxic to peripheral blood mononuclear cells (PBMC) but raised intracellular reactive oxygen species (ROS) levels. Pure genistein (in DMSO solution) was not only nontoxic to PBMC, but also suppressed the ROS levels in a manner dependent on genistein dosage. A similar dose-dependent suppression of ROS was found in genistein-modified PA (i.e., PA/G) membranes. However, the PVP addition had little or no effect in the suppression of ROS levels for the ternary PA:PVP/G system; the membrane ROS suppression was largely controlled by the genistein dosage. The levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin (IL-6) in whole blood were measured by ex vivo stimulation with lipopolysaccharide (LPS). The unmodified PA:PVP membranes drastically increased the level of TNF-α; however, the concentration of IL-1β and IL-6 remained almost the same. The PA/G membranes reduced the concentration of IL-1β and TNF-α even at very low genistein loadings, but it required a higher genistein loading to realize a similar effect in the case of IL-6. Of particular importance is that the genistein-modified blend membranes (PA:PVP/G) showed greater suppression of the concentrations of all three cytokines (TNF-α, IL-1β, and IL-6) in comparison with those of the PA/G membranes, signifying the role of PVP in the enhanced anti-inflammatory properties of these genistein-modified membranes. Ultraviolet-visible (UV-vis) spectroscopy was employed to quantify any genistein leaching during the in vitro testing.

  11. Preparation and Characterization of Hydrophilically Modified PVDF Membranes by a Novel Nonsolvent Thermally Induced Phase Separation Method.

    PubMed

    Hu, Ningen; Xiao, Tonghu; Cai, Xinhai; Ding, Lining; Fu, Yuhua; Yang, Xing

    2016-11-18

    In this study, a nonsolvent thermally-induced phase separation (NTIPS) method was first proposed to fabricate hydrophilically-modified poly(vinylidene fluoride) (PVDF) membranes to overcome the drawbacks of conventional thermally-induced phase separation (TIPS) and nonsolvent-induced phase separation (NIPS) methods. Hydrophilically-modified PVDF membranes were successfully prepared by blending in hydrophilic polymer polyvinyl alcohol (PVA) at 140 °C. A series of PVDF/PVA blend membranes was prepared at different total polymer concentrations and blend ratios. The morphological analysis via SEM indicated that the formation mechanism of these hydrophilically-modified membranes was a combined NIPS and TIPS process. As the total polymer concentration increased, the tensile strength of the membranes increased; meanwhile, the membrane pore size, porosity and water flux decreased. With the PVDF/PVA blend ratio increased from 10:0 to 8:2, the membrane pore size and water flux increased. The dynamic water contact angle of these membranes showed that the hydrophilic properties of PVDF/PVA blend membranes were prominently improved. The higher hydrophilicity of the membranes resulted in reduced membrane resistance and, hence, higher permeability. The total resistance Rt of the modified PVDF membranes decreased significantly as the hydrophilicity increased. The irreversible fouling related to pore blocking and adsorption fouling onto the membrane surface was minimal, indicating good antifouling properties.

  12. Preparation and Characterization of Hydrophilically Modified PVDF Membranes by a Novel Nonsolvent Thermally Induced Phase Separation Method

    PubMed Central

    Hu, Ningen; Xiao, Tonghu; Cai, Xinhai; Ding, Lining; Fu, Yuhua; Yang, Xing

    2016-01-01

    In this study, a nonsolvent thermally-induced phase separation (NTIPS) method was first proposed to fabricate hydrophilically-modified poly(vinylidene fluoride) (PVDF) membranes to overcome the drawbacks of conventional thermally-induced phase separation (TIPS) and nonsolvent-induced phase separation (NIPS) methods. Hydrophilically-modified PVDF membranes were successfully prepared by blending in hydrophilic polymer polyvinyl alcohol (PVA) at 140 °C. A series of PVDF/PVA blend membranes was prepared at different total polymer concentrations and blend ratios. The morphological analysis via SEM indicated that the formation mechanism of these hydrophilically-modified membranes was a combined NIPS and TIPS process. As the total polymer concentration increased, the tensile strength of the membranes increased; meanwhile, the membrane pore size, porosity and water flux decreased. With the PVDF/PVA blend ratio increased from 10:0 to 8:2, the membrane pore size and water flux increased. The dynamic water contact angle of these membranes showed that the hydrophilic properties of PVDF/PVA blend membranes were prominently improved. The higher hydrophilicity of the membranes resulted in reduced membrane resistance and, hence, higher permeability. The total resistance Rt of the modified PVDF membranes decreased significantly as the hydrophilicity increased. The irreversible fouling related to pore blocking and adsorption fouling onto the membrane surface was minimal, indicating good antifouling properties. PMID:27869711

  13. Welding of Nafion® - The influence of time, temperature and pressure

    NASA Astrophysics Data System (ADS)

    Froelich, Konstantin; Rauner, Helmut; Scheiba, Frieder; Roth, Christina; Ehrenberg, Helmut

    2014-12-01

    The properties of perfluorosulfonic acid ionomers (PFSIs) such as DuPont's Nafion® have been extensively characterized during the last decades. However, despite its importance for the upcoming industrialization of PFSI-based products no detailed investigation of the welding behavior of PFSIs has been performed. This paper investigates the welding behavior of Nafion® NRE-211 membranes common in both academia and industry over an industrially relevant parameter range of time, temperature and pressure. The strength evolution of the welded interface shows a linear dependence with square root of time and an Arrhenius temperature dependence. It is thus suggested that the welding behavior of Nafion® membranes can be predicted by the reptation model from polymer dynamics. Time-temperature master curves for a large range of parameters are constructed. Pressure is shown to have positive effects at very low welding times, but strongly negative effects at longer welding times, which can be explained by the model. Welding time and final strength of the fully healed interface are predicted using measurement and literature data. A short discussion on thermal transitions and on the role of crystallinity is also presented.

  14. Elevated Performance of Thin Film Nanocomposite Membranes Enabled by Modified Hydrophilic MOFs for Nanofiltration.

    PubMed

    Zhu, Junyong; Qin, Lijuan; Uliana, Adam; Hou, Jingwei; Wang, Jing; Zhang, Yatao; Li, Xin; Yuan, Shushan; Li, Jian; Tian, Miaomiao; Lin, Jiuyang; Van der Bruggen, Bart

    2017-01-18

    Metal-organic frameworks (MOFs) are studied for the design of advanced nanocomposite membranes, primarily due to their ultrahigh surface area, regular and highly tunable pore structures, and favorable polymer affinity. However, the development of engineered MOF-based membranes for water treatment lags behind. Here, thin-film nanocomposite (TFN) membranes containing poly(sodium 4-styrenesulfonate) (PSS) modified ZIF-8 (mZIF) in a polyamide (PA) layer were constructed via a facile interfacial polymerization (IP) method. The modified hydrophilic mZIF nanoparticles were evenly dispersed into an aqueous solution comprising piperazine (PIP) monomers, followed by polymerizing with trimesoyl chloride (TMC) to form a composite PA film. FT-IR spectroscopy and XPS analyses confirm the presence of mZIF nanoparticles on the top layer of the membranes. SEM and AFM images evince a retiform morphology of the TFN-mZIF membrane surface, which is intimately linked to the hydrophilicity and adsorption capacity of mZIF nanoparticles. Furthermore, the effect of different ZIF-8 loadings on the overall membrane performance was studied. Introducing the hydrophilizing mZIF nanoparticles not only furnishes the PA layer with a better surface hydrophilicity and more negative charge but also more than doubles the original water permeability, while maintaining a high retention of Na2SO4. The ultrahigh retentions of reactive dyes (e.g., reactive black 5 and reactive blue 2, >99.0%) for mZIF-functionalized PA membranes ensure their superior nanofiltration performance. This facile, cost-effective strategy will provide a useful guideline to integrate with other modified hydrophilic MOFs to design nanofiltration for water treatment.

  15. FTIR spectroscopic study of the complex formation between H(+) and DMSO in Nafion.

    PubMed

    Karelin, A I; Kayumov, R R; Sanginov, E A; Dobrovolsky, Yu A

    2017-05-05

    Nafion membranes plasticized with dimethyl sulfoxide (DMSO) have been examined at room temperature using the vacuum ATR - FTIR spectroscopic technique in the range 50-4000cm(-1). The amount of the plasticizer corresponds to the molecular ratio n=DMSO/H(+)=1.2, 2.3, 4.8, 7.0, 9.7 and 13.3. The medium intensity band with two maxima at 780 and 853cm(-1) have been assigned to the ν(SO) stretching vibrations of the H(+)(DMSO)2 complex. The possible reason of ν(SO) splitting is symmetry decrease of hydrogen bond under the influence of the anion group SO3(-) electric field. Whereas the mutual association of free DMSO molecules in Nafion leads to appearance of weak band at 86cm(-1) assigned to the dipole-dipole interactions.

  16. FTIR spectroscopic study of the complex formation between H+ and DMSO in Nafion

    NASA Astrophysics Data System (ADS)

    Karelin, A. I.; Kayumov, R. R.; Sanginov, E. A.; Dobrovolsky, Yu. A.

    2017-05-01

    Nafion membranes plasticized with dimethyl sulfoxide (DMSO) have been examined at room temperature using the vacuum ATR - FTIR spectroscopic technique in the range 50-4000 cm- 1. The amount of the plasticizer corresponds to the molecular ratio n = DMSO/H+ = 1.2, 2.3, 4.8, 7.0, 9.7 and 13.3. The medium intensity band with two maxima at 780 and 853 cm- 1 have been assigned to the ν(SO) stretching vibrations of the H+(DMSO)2 complex. The possible reason of ν(SO) splitting is symmetry decrease of hydrogen bond under the influence of the anion group sbnd SO3- electric field. Whereas the mutual association of free DMSO molecules in Nafion leads to appearance of weak band at 86 cm- 1 assigned to the dipole-dipole interactions.

  17. Enhancement of dopamine sensing by layer-by-layer assembly of PVI-dmeOs and Nafion on carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Cui, Hui-Fang; Cui, Yu-Han; Sun, Yu-Long; Zhang, Kuan; Zhang, Wei-De

    2010-05-01

    In this study, carbon nanotubes (CNTs) were modified to further improve their performance in electrochemical sensing of dopamine (DA) levels. After a redox polymer, poly(vinylimidazole) complexed with Os(4, 4'-dimethyl- 2, 2-bipyridine)2Cl (termed PVI-dmeOs) was electrodeposited on multi-wall CNTs (MWCNTs), Nafion and PVI-dmeOs films were successfully layer-by-layer (LBL) assembled on the hydrophilic surface of the as-prepared PVI-dmeOs/CNTs nanocomposites through electrostatic interactions. The LBL assembly was proved by scanning electron microscopy (SEM), electrochemistry and UV-vis spectroscopy measurements. LBL assembly of Nafion/PVI-dmeOs films on CNTs significantly enhanced their linear sweep voltammetry (LSV) response sensitivity to DA, with a maximum enhancement for three Nafion/PVI-dmeOs film-modified MWCNTs. The LSV peak current density of (Nafion/PV I-dmeOs)3/CNT electrodes in response to 10 and 50 µM DA solutions was about 7.3 and 3.9 times those for bare CNTs. At the (Nafion/PV I-dmeOs)3/CNT electrodes, the limit of detection (LOD) (signal-to-noise ratio: 3) was 0.05 µM DA, the linear range was 0.1-10 µM DA (with a linear regression coefficient of 0.97) and the DA-sensing sensitivity was 8.15 µA cm - 2 µM - 1. The newly fabricated (Nafion/PV I-dmeOs)3/CNT electrodes may be developed as an ideal biosensor for direct and in situ measurement of DA levels.

  18. Enhancement of dopamine sensing by layer-by-layer assembly of PVI-dmeOs and Nafion on carbon nanotubes.

    PubMed

    Cui, Hui-Fang; Cui, Yu-Han; Sun, Yu-Long; Zhang, Kuan; Zhang, Wei-De

    2010-05-28

    In this study, carbon nanotubes (CNTs) were modified to further improve their performance in electrochemical sensing of dopamine (DA) levels. After a redox polymer, poly(vinylimidazole) complexed with Os(4, 4'-dimethyl- 2, 2-bipyridine)(2)Cl (termed PVI-dmeOs) was electrodeposited on multi-wall CNTs (MWCNTs), Nafion and PVI-dmeOs films were successfully layer-by-layer (LBL) assembled on the hydrophilic surface of the as-prepared PVI-dmeOs/CNTs nanocomposites through electrostatic interactions. The LBL assembly was proved by scanning electron microscopy (SEM), electrochemistry and UV-vis spectroscopy measurements. LBL assembly of Nafion/PVI-dmeOs films on CNTs significantly enhanced their linear sweep voltammetry (LSV) response sensitivity to DA, with a maximum enhancement for three Nafion/PVI-dmeOs film-modified MWCNTs. The LSV peak current density of (Nafion/PV I-dmeOs)(3)/CNT electrodes in response to 10 and 50 microM DA solutions was about 7.3 and 3.9 times those for bare CNTs. At the (Nafion/PV I-dmeOs)(3)/CNT electrodes, the limit of detection (LOD) (signal-to-noise ratio: 3) was 0.05 microM DA, the linear range was 0.1-10 microM DA (with a linear regression coefficient of 0.97) and the DA-sensing sensitivity was 8.15 microA cm( - 2) microM( - 1). The newly fabricated (Nafion/PV I-dmeOs)(3)/CNT electrodes may be developed as an ideal biosensor for direct and in situ measurement of DA levels.

  19. NMR and pulsed field gradient NMR approach of water sorption properties in Nafion at low temperature.

    PubMed

    Guillermo, Armel; Gebel, Gérard; Mendil-Jakani, Hakima; Pinton, Eric

    2009-05-14

    The water uptake and the water self-diffusion coefficient were measured in Nafion membranes at subzero temperatures. NMR spectroscopy was used to precisely quantify the actual concentration of water in membranes as a function of the temperature and their hydration rates at room temperature. We find that below 273 K the water concentration decreases with temperature to reach, at around 220 K, a limit value independent of the initial concentration. This regime is observed if the concentration at room temperature is higher than 10%. Below this concentration no membrane deswelling was observed. The water self-diffusion coefficient, measured by pulsed field gradient NMR in function of the temperature, is determined by the actual concentration C(T) whatever the concentration at room temperature. The concentration variation is attributed to a decrease in the relative humidity RH(T) of the water vapor surrounding the membrane induced by the simultaneous presence of supercooled water inside the membrane and ice outside the membrane.

  20. Mechanism for degradation of Nafion in PEM fuel cells from quantum mechanics calculations.

    PubMed

    Yu, Ted H; Sha, Yao; Liu, Wei-Guang; Merinov, Boris V; Shirvanian, Pezhman; Goddard, William A

    2011-12-14

    We report results of quantum mechanics (QM) mechanistic studies of Nafion membrane degradation in a polymer electrolyte membrane (PEM) fuel cell. Experiments suggest that Nafion degradation is caused by generation of trace radical species (such as OH(●), H(●)) only when in the presence of H(2), O(2), and Pt. We use density functional theory (DFT) to construct the potential energy surfaces for various plausible reactions involving intermediates that might be formed when Nafion is exposed to H(2) (or H(+)) and O(2) in the presence of the Pt catalyst. We find a barrier of 0.53 eV for OH radical formation from HOOH chemisorbed on Pt(111) and of 0.76 eV from chemisorbed OOH(ad), suggesting that OH might be present during the ORR, particularly when the fuel cell is turned on and off. Based on the QM, we propose two chemical mechanisms for OH radical attack on the Nafion polymer: (1) OH attack on the S-C bond to form H(2)SO(4) plus a carbon radical (barrier: 0.96 eV) followed by decomposition of the carbon radical to form an epoxide (barrier: 1.40 eV). (2) OH attack on H(2) crossover gas to form hydrogen radical (barrier: 0.04 eV), which subsequently attacks a C-F bond to form HF plus carbon radicals (barrier as low as 1.00 eV). This carbon radical can then decompose to form a ketone plus a carbon radical with a barrier of 0.86 eV. The products (HF, OCF(2), SCF(2)) of these proposed mechanisms have all been observed by F NMR in the fuel cell exit gases along with the decrease in pH expected from our mechanism.

  1. Characterization and Evaluation of Reverse Osmosis Membranes Modified with Ag2O Nanoparticles to Improve Performance

    NASA Astrophysics Data System (ADS)

    Al-Hobaib, Abdullah S.; AL-Sheetan, Khalid M.; Shaik, Mohammed Rafi; Al-Andis, Naser M.; Al-Suhybani, M. S.

    2015-09-01

    The objective of this work was to prepare and characterize a new and highly efficient modified membrane by in situ interfacial polymerization on porous polysulfone supports. The process used m-phenylenediamine and trimesoyl chloride in hexane, incorporating silver oxide Ag2O nanoparticles of varied concentrations from 0.001 to 0.1 wt%. Ag2O nanoparticles were prepared at different sizes varying between 20 and 50 nm. The modified membranes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), transmission electron microscopy (TEM), and contact angle measurement. The results showed a smooth membrane surface and average surface roughness from 31 to 74 nm. Moreover, hydrophilicity improved and the contact angle decreased to 41° at 0.009 wt% silver oxide. The performances of the developed membranes were investigated by measuring permeate fluxes and salt rejection capability by passing NaCl solutions (2000 ppm) through the membranes at 225 psi. The results showed that the flux increased from 26 to 40.5 L/m2 h, while the salt rejection was high, at 99 %, with 0.003 wt% Ag2O nanoparticles.

  2. Characterization and Evaluation of Reverse Osmosis Membranes Modified with Ag2O Nanoparticles to Improve Performance.

    PubMed

    Al-Hobaib, Abdullah S; Al-Sheetan, Khalid M; Shaik, Mohammed Rafi; Al-Andis, Naser M; Al-Suhybani, M S

    2015-12-01

    The objective of this work was to prepare and characterize a new and highly efficient modified membrane by in situ interfacial polymerization on porous polysulfone supports. The process used m-phenylenediamine and trimesoyl chloride in hexane, incorporating silver oxide Ag2O nanoparticles of varied concentrations from 0.001 to 0.1 wt%. Ag2O nanoparticles were prepared at different sizes varying between 20 and 50 nm. The modified membranes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), transmission electron microscopy (TEM), and contact angle measurement. The results showed a smooth membrane surface and average surface roughness from 31 to 74 nm. Moreover, hydrophilicity improved and the contact angle decreased to 41° at 0.009 wt% silver oxide. The performances of the developed membranes were investigated by measuring permeate fluxes and salt rejection capability by passing NaCl solutions (2000 ppm) through the membranes at 225 psi. The results showed that the flux increased from 26 to 40.5 L/m(2) h, while the salt rejection was high, at 99 %, with 0.003 wt% Ag2O nanoparticles.

  3. Performance enhancement of polyvinyl chloride ultrafiltration membrane modified with graphene oxide.

    PubMed

    Zhao, Yuanyuan; Lu, Jiaqi; Liu, Xuyang; Wang, Yudan; Lin, Jiuyang; Peng, Na; Li, Jingchun; Zhao, Fangbo

    2016-10-15

    A novel polyvinyl chloride (PVC) membrane was modified with graphene oxide (GO) via phase inversion method to improve its hydrophilicity and mechanical properties. The GO presented a large amount of hydrophilic groups after the modification through the modified Hummers method. It was observed that with the addition of low fraction of GO powder, the GO/PVC hybrid membranes exhibited a significant enhancement in hydrophilicity, water flux, and mechanical properties. With optimal dosage (0.1wt%), the pure water flux of GO/PVC membrane increased from 232.6L/(m(2)hbar) to 430.0L/(m(2)hbar) and the tensile strength increased from 231.3cN to 305.3cN. The improved properties of the PVC/GO hybrid membranes are mainly attributed to the strong hydrophilicity of functional groups on the GO surface, indicating that GO has a promising candidate for modification of PVC ultrafiltration membranes in wastewater treatment.

  4. Surface characteristics of acrylic modified polysulfone membranes improves renal proximal tubule cell adhesion and spreading.

    PubMed

    Teo, Jeremy Choon Meng; Ng, Roderica Rui Ge; Ng, Chee Ping; Lin, Alex Wei Haw

    2011-05-01

    Current polyvinylpyrrolidone-modified polysulfone (PVP-PSU) membranes in haemodialysers do not facilitate the attachment and proliferation of renal proximal tubule cells (RPTCs). For bioartificial kidney (BAK) development expensive extracellular matrices are employed to ensure the PVP-PSU membranes can serve as a substrate for RPTCs. In this study we modified PSU using an acrylic monomer (am-PSU) and polymerization using ultraviolet irradiation. We demonstrated that on adjusting the PSU or acrylic content of the membranes the wettability and surface chemistry were altered, and this affected the amount of fibronectin (Fn) that was adsorbed onto the membranes. Using an integrin blocking assay we ascertained that Fn is an important extracellular matrix component that mediates RPTC attachment. The amount of Fn adsorbed also led to different bioresponses of RPTCs, which were evaluated using attachment and proliferation assays and qualitative quantification of vinculin, focal adhesion kinase, zonula occludens and Na(+)/K(+) ATPase. Our optimized membrane, am-PSU1 (21.4% C-O groups, 19.1% PVP-PSU; contact angle 71.5-80.80, PVP-PSU: 52.4-67.50), supports a confluent monolayer of RPTCs and prevents creatinine and inulin diffusion from the apical to the basal side, meeting the requirements for application in BAKs. However, further in vivo evaluation to assess the full functionality of RPTCs on am-PSU1 is required. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  5. Permeability of membranes to amino acids and modified amino acids: mechanisms involved in translocation

    NASA Technical Reports Server (NTRS)

    Chakrabarti, A. C.; Deamer, D. W. (Principal Investigator); Miller, S. L. (Principal Investigator)

    1994-01-01

    The amino acid permeability of membranes is of interest because they are one of the key solutes involved in cell function. Membrane permeability coefficients (P) for amino acid classes, including neutral, polar, hydrophobic, and charged species, have been measured and compared using a variety of techniques. Decreasing lipid chain length increased permeability slightly (5-fold), while variations in pH had only minor effects on the permeability coefficients of the amino acids tested in liposomes. Increasing the membrane surface charge increased the permeability of amino acids of the opposite charge, while increasing the cholesterol content decreased membrane permeability. The permeability coefficients for most amino acids tested were surprisingly similar to those previously measured for monovalent cations such as sodium and potassium (approximately 10(-12)-10(-13) cm s-1). This observation suggests that the permeation rates for the neutral, polar and charged amino acids are controlled by bilayer fluctuations and transient defects, rather than partition coefficients and Born energy barriers. Hydrophobic amino acids were 10(2) more permeable than the hydrophilic forms, reflecting their increased partition coefficient values. External pH had dramatic effects on the permeation rates for the modified amino acid lysine methyl ester in response to transmembrane pH gradients. It was established that lysine methyl ester and other modified short peptides permeate rapidly (P = 10(-2) cm s-1) as neutral (deprotonated) molecules. It was also shown that charge distributions dramatically alter permeation rates for modified di-peptides. These results may relate to the movement of peptides through membranes during protein translocation and to the origin of cellular membrane transport on the early Earth.

  6. Characterization of charge properties of an ultrafiltration membrane modified by surface grafting of poly(allylamine) hydrochloride.

    PubMed

    Dejeu, J; Lakard, B; Fievet, P; Lakard, S

    2009-05-01

    A polyethersulfone ultrafiltration membrane was functionalized by a cationic polyelectrolyte, the poly(allylamine) hydrochloride (PAH). The influence of the time of adsorption of PAH on the membrane charge properties was studied. Several characterization techniques were used to investigate the membrane modification. Tangential and transmembrane streaming potential measurements were conducted to characterize the outer and inner surfaces of the membrane, respectively. Both techniques indicated that the surface modification of the membrane was efficient. The charge of the outer surface was reversed (from negative values for the unmodified membrane to positive values for the modified membrane) and the charge of the inner surface was neutralized after adsorption of the cationic polyelectrolyte onto the pore walls. The modification of both the outer surface of the membrane and the pore walls was also put in evidence with membrane potential measurements. It was found that the charge of the PAH-modified membrane is affected by the time of immersion in PAH solution. Experimental data seem to show a fast modification of the membrane for the first 15 min; nevertheless, the modification was more pronounced after 24 h of PAH adsorption. Diffusion experiments carried out with unmodified and modified membranes for four salts (KCl, NaCl, MgCl, and CaCl(2)) showed a decrease in the salt permeability after functionalization of the membrane. The permeability decrease was greater for 2:1 salts than for 1:1 salts. This decrease was explained by electrostatic interactions.

  7. Radiation-grafted, chemically modified membranes part I - Synthesis of a selective aluminum material

    NASA Astrophysics Data System (ADS)

    Bazante-Yamaguishi, Renata; Moura, Eduardo; Manzoli, José E.; Geraldo, Aurea B. C.

    2014-01-01

    Polymeric membranes were styrene grafted by irradiation methods and the obtained material was chemically modified to become aluminum selective. For this purpose, polymeric substrates of PVC (polyvinyl chloride) and PP (polypropylene) were styrene grafted mutually by gamma and electron beam irradiation. The modification process includes three basic reaction paths: Friedel-Crafts acylation, 2-methylanisole coupling and a final oxidation to achieve aluminum selectivity. Although this specific chemical modification in derivatives of polystyrene is not new, the new challenge is to obtain a selective material where original membrane characteristics (physical shape and mechanical resistance) are minimally conserved after such an aggressive treatment.

  8. Luminescence Probe Studies of Nafion Polyelectrolytes.

    DTIC Science & Technology

    1983-10-07

    I iD-Ri33 519 LUMINESCENCE PROBE STUDIES OF NRFION FOLYELECTROLYTES i/i (U) TEXAS A AND M UNIV COLLEGE STATION DEPT OF CHEMIISTRY N E PRIETO ET AL...Task No. NR 627-838 TECHNICAL REPORT NO. 2 *Luminescence Probe Studi s of Nafion Polyelectrolytes Pby Nelson E. Prieto and Charles R. Martin 41...E. Prieto and Charles R. Martin N00014-82K-0612 9. PERFORMING ORGANIZATION NAME AND ADDRESS _%. -PROGRAM ELEMENT. PROJECT. TASK AREA & WORKC UNIT

  9. Nafion coated stainless steel for anti-biofilm application.

    PubMed

    Zhong, Li Juan; Pang, Li Qing; Che, Li Ming; Wu, Xue E; Chen, Xiao Dong

    2013-11-01

    Biofilms can adhere to most surfaces and have caused a wide range of problems in various industrial processes as well as daily life activities. In this work, the anti-biofilm ability of Nafion-coated stainless steel surface was investigated and our results showed that stainless steel discs coated with 1% Nafion can significantly reduce E. coli adhesion. Nafion has a large amount of negatively charged sulphonate groups, and the findings of this study suggest that the negative surface charge can greatly reduce bacterial adhesion through increasing the electrostatic repulsion between negatively charged bacterial cells and Nafion coated stainless steel surface. The roughness of coated and uncoated stainless steel discs made no significant differences while the hydrophobic of the discs increased after coated with Nafion.

  10. Protein adsorption capability on polyurethane and modified-polyurethane membrane for periodontal guided tissue regeneration applications.

    PubMed

    Sheikh, Zeeshan; Khan, Abdul Samad; Roohpour, Nima; Glogauer, Michael; Rehman, Ihtesham U

    2016-11-01

    Periodontal disease if left untreated can result in creation of defects within the alveolar ridge. Barrier membranes are frequently used with or without bone replacement graft materials for achieving periodontal guided tissue regeneration (GTR). Surface properties of barrier membranes play a vital role in their functionality and clinical success. In this study polyetherurethane (PEU) membranes were synthesized by using 4,4'-methylene-diphenyl diisocyanate (MDI), polytetramethylene oxide (PTMO) and 1,4-butane diol (BDO) as a chain extender via solution polymerization. Hydroxyl terminated polydimethylsiloxane (PDMS) due to having inherent surface orientation towards air was used for surface modification of PEU on one side of the membranes. This resulting membranes had one surface being PEU and the other being PDMS coated PEU. The prepared membranes were treated with solutions of bovine serum albumin (BSA) in de-ionized water at 37°C at a pH of 7.2. The surface protein adsorptive potential of PEU membranes was observed using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Raman spectroscopy and Confocal Raman spectroscopy. The contact angle measurement, tensile strength and modulus of prepared membranes were also evaluated. PEU membrane (89.86±1.62°) exhibited less hydrophobic behavior than PEU-PDMS (105.87±3.16°). The ultimate tensile strength and elastic modulus of PEU (27±1MPa and 14±2MPa) and PEU-PDMS (8±1MPa and 26±1MPa) membranes was in required range. The spectral analysis revealed adsorption of BSA proteins on the surface of non PDMS coated PEU surface. The PDMS modified PEU membranes demonstrated a lack of BSA adsorption. The non PDMS coated side of the membrane which adsorbs proteins could potentially be used facing towards the defect attracting growth factors for periodontal tissue regeneration. Whereas, the PDMS coated side could serve as an occlusive barrier for preventing gingival epithelial cells from

  11. Surface-modified silica colloidal crystals: nanoporous films and membranes with controlled ionic and molecular transport.

    PubMed

    Zharov, Ilya; Khabibullin, Amir

    2014-02-18

    Nanoporous membranes are important for the study of the transport of small molecules and macromolecules through confined spaces and in applications ranging from separation of biomacromolecules and pharmaceuticals to sensing and controlled release of drugs. For many of these applications, chemists need to gate the ionic and molecular flux through the nanopores, which in turn depends on the ability to control the nanopore geometry and surface chemistry. Most commonly used nanoporous membrane materials are based on polymers. However, the nanostructure of polymeric membranes is not well-defined, and their surface is hard to modify. Inorganic nanoporous materials are attractive alternatives for polymers in the preparation of nanoporous membranes. In this Account, we describe the preparation and surface modification of inorganic nanoporous films and membranes self-assembled from silica colloidal spheres. These spheres form colloidal crystals with close-packed face centered cubic lattices upon vertical deposition from colloidal solutions. Silica colloidal crystals contain ordered arrays of interconnected three dimensional voids, which function as nanopores. We can prepare silica colloidal crystals as supported thin films on various flat solid surfaces or obtain free-standing silica colloidal membranes by sintering the colloidal crystals above 1000 °C. Unmodified silica colloidal membranes are capable of size-selective separation of macromolecules, and we can surface-modify them in a well-defined and controlled manner with small molecules and polymers. For the surface modification with small molecules, we use silanol chemistry. We grow polymer brushes with narrow molecular weight distribution and controlled length on the colloidal nanopore surface using atom transfer radical polymerization or ring-opening polymerization. We can control the flux in the resulting surface-modified nanoporous films and membranes by pH and ionic strength, temperature, light, and small molecule

  12. Highly conductive polymer electrolyte membranes modified with polyethylene glycol-bis-carbamate

    NASA Astrophysics Data System (ADS)

    Fu, Guopeng; Dempsey, Janel; Kyu, Thein

    By virtue of its non-flammability and chemical stability, polyethylene glycol (PEG) networks have shown potential application in all solid-state polymer electrolyte membranes (PEM). However, room temperature ionic conductivity of these PEG based PEMs is inherently low. Plasticization of these PEMs is needed to improve the ionic conductivity. It was demonstrated by this group that small-molecule plasticizers such as succinonitrile, ethylene carbonate, or urea-carbamate can boost ionic conductivity of solid-state polymer electrolyte membranes. Polyethylene glycol bis-carbamate (PEGBC) was synthesized via condensation reaction of polyethylene glycol diamine and ethylene carbonate. The PEGBC modified PEM has shown higher ionic conductivity relative to the unmodified PEM. Moreover, PEGBC modified PEM has a better thermal stability relative to ethylene carbonate based liquid electrolyte with enhanced ionic conductivity. Supported by NSF-DMR 1161070, 1502543 and REU 1359321.

  13. Water permeability of polyethylene terephthalate track membranes modified in plasma of dimethylaniline

    NASA Astrophysics Data System (ADS)

    Kravets, Lyubov; Dmitriev, Serguei; Gilman, Alla; Drachev, Alexander

    2004-09-01

    The surface properties and hydrodynamic characteristics of composite membranes consisting of a porous substrate, on which a polymer layer from a direct current discharge in a mixture of air and vapours of dimethylaniline was deposited, have been investigated. As a substrate, we used poly(ethylene) terephthalate track membrane (PET TM) of the thickness of 10 μ m and the effective pore diameter of 0.215 μ m (pore density is 2\\cdot 10^8 cm-2). The performed researches show that when treating the membranes in plasma, two competing processes are observed: deposition of the polymer layer on a membrane surface, that testifies increase of the mass of sample, and etching of a polymeric matrix which causes growth of effective pore diameter. The last process is stipulated by presence of oxygen in the gas mixture. Decreasing the degree of overweight of the sample at increasing the treatment time leads us to a supposition that a dominating process in this case becomes the process of gas-discharge etching. In all cases, if treating PET TM, a drop of the water contact angle occurs, i.e. hydrophilization of the membrane surface takes place that is connected first of all with a grafting of polymer layer containing polar functional groups. The research in the hydrodynamic characteristics of the initial PET TM and the membranes modified in plasma at neutral and subacid pH value of filtrate leads to a linear dependence of their permeability upon the quantity of applied pressure. It is connected with a viscous character of the flow, that is, when the diameter of the pores of the membrane is much more than the size of the water molecules. This fact shows that the macromolecules of the deposited polymer layer in this case have a compact conformation, which does not hinder the water molecules infiltration. At a lower pH value of the filtrate, the picture cardinally changes. For modified in plasma membranes a diversion from the linear relation is observed. This means that in this case

  14. Interaction study between maltose-modified PPI dendrimers and lipidic model membranes.

    PubMed

    Wrobel, Dominika; Appelhans, Dietmar; Signorelli, Marco; Wiesner, Brigitte; Fessas, Dimitrios; Scheler, Ulrich; Voit, Brigitte; Maly, Jan

    2015-07-01

    The influence of maltose-modified poly(propylene imine) (PPI) dendrimers on dimyristoylphosphatidylcholine (DMPC) or dimyristoylphosphatidylcholine/dimyristoylphosphatidylglycerol (DMPC/DMPG) (3%) liposomes was studied. Fourth generation (G4) PPI dendrimers with primary amino surface groups were partially (open shell glycodendrimers - OS) or completely (dense shell glycodendrimers - DS) modified with maltose residues. As a model membrane, two types of 100nm diameter liposomes were used to observe differences in the interactions between neutral DMPC and negatively charged DMPC/DMPG bilayers. Interactions were studied using fluorescence spectroscopy to evaluate the membrane fluidity of both the hydrophobic and hydrophilic parts of the lipid bilayer and using differential scanning calorimetry to investigate thermodynamic parameter changes. Pulsed-filed gradient NMR experiments were carried out to evaluate common diffusion coefficient of DMPG and DS PPI in D2O when using below critical micelle concentration of DMPG. Both OS and DS PPI G4 dendrimers show interactions with liposomes. Neutral DS dendrimers exhibit stronger changes in membrane fluidity compared to OS dendrimers. The bilayer structure seems more rigid in the case of anionic DMPC/DMPG liposomes in comparison to pure and neutral DMPC liposomes. Generally, interactions of dendrimers with anionic DMPC/DMPG and neutral DMPC liposomes were at the same level. Higher concentrations of positively charged OS dendrimers induced the aggregation process with negatively charged liposomes. For all types of experiments, the presence of NaCl decreased the strength of the interactions between glycodendrimers and liposomes. Based on NMR diffusion experiments we suggest that apart from electrostatic interactions for OS PPI hydrogen bonds play a major role in maltose-modified PPI dendrimer interactions with anionic and neutral model membranes where a contact surface is needed for undergoing multiple H-bond interactions between

  15. Hemocompatibility assessment of carbonic anhydrase modified hollow fiber membranes for artificial lungs.

    PubMed

    Oh, Heung-Il; Ye, Sang-Ho; Johnson, Carl A; Woolley, Joshua R; Federspiel, William J; Wagner, William R

    2010-05-01

    Hollow fiber membrane (HFM)-based artificial lungs can require a large blood-contacting membrane surface area to provide adequate gas exchange. However, such a large surface area presents significant challenges to hemocompatibility. One method to improve carbon dioxide (CO(2)) transfer efficiency might be to immobilize carbonic anhydrase (CA) onto the surface of conventional HFMs. By catalyzing the dehydration of bicarbonate in blood, CA has been shown to facilitate diffusion of CO(2) toward the fiber membranes. This study evaluated the impact of surface modifying a commercially available microporous HFM-based artificial lung on fiber blood biocompatibility. A commercial poly(propylene) Celgard HFM surface was coated with a siloxane, grafted with amine groups, and then attached with CA which has been shown to facilitate diffusion of CO(2) toward the fiber membranes. Results following acute ovine blood contact indicated no significant reduction in platelet deposition or activation with the siloxane coating or the siloxane coating with grafted amines relative to base HFMs. However, HFMs with attached CA showed a significant reduction in both platelet deposition and activation compared with all other fiber types. These findings, along with the improved CO(2) transfer observed in CA modified fibers, suggest that its incorporation into HFM design may potentiate the design of a smaller, more biocompatible HFM-based artificial lung.

  16. Nur77 is differentially modified in PC12 cells upon membrane depolarization and growth factor treatment.

    PubMed Central

    Hazel, T G; Misra, R; Davis, I J; Greenberg, M E; Lau, L F

    1991-01-01

    The rat pheochromocytoma cell line PC12 can be induced by growth factors to undergo proliferation and neuronal differentiation. These cells also have excitable membranes that can be depolarized by neurotransmitters or elevated levels of extracellular KCl. Treatment of PC12 cells with growth factors or membrane-depolarizing agents rapidly activates the expression of specific genes whose products are thought to mediate the subsequent biological responses. One such gene, nur77, is a member of the steroid and thyroid hormone receptor gene superfamily. We have identified the Nur77 protein and shown that it is synthesized rapidly and transiently in PC12 cells following stimulation, has a short half-life of 30 to 40 min, and is located in both the nucleus and the cytoplasm. Nur77 is posttranslationally modified, primarily by phosphorylation on serine residues. Phosphopeptide analysis reveals that Nur77 is modified differently upon membrane depolarization than after treatment with growth factors. We hypothesize that the activity of Nur77 is regulated by both differential gene expression and posttranslational modification and that these modes of regulation contribute to distinct downstream responses specific to membrane depolarization and growth factor treatment. Images PMID:1645447

  17. Comparison of Physicochemical Membrane Properties of Vesicles Modified with Guanidinium Derivatives.

    PubMed

    Watanabe, Nozomi; Suga, Keishi; Umakoshi, Hiroshi

    2017-08-18

    Bilayer vesicles have garnered considerable research attention as molecular vehicles capable of noncovalent interaction with biomolecules via electrostatic and hydrophobic bonds, and van der Waals interactions. Guanidinium strongly interacts with phosphate groups. Thus, guanidinium modification of vesicles helps intensify the interaction between lipid membranes and nucleic acids. Here, two kinds of guanidinium derivatives, stearylguanidinium (SG) and myristoylarginine (MA), were synthesized and incorporated into 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) vesicles. Differences in their membrane properties were evaluated using Fourier transform infrared spectroscopy, Raman spectroscopy, and the fluorescent probes 1,6-diphenyl-1,3,5-hexatriene (DPH), 6-lauroyl-2-dimethylaminonaphthalene (Laurdan), and 2-p-toluidinylnaphthalene-6-sulfonate (TNS). The increased SG ratio increased overall hydrophobicity and lipid packing density compared to POPC vesicles, and SG-modified vesicles successfully attracted and then denatured negatively charged transfer RNAs (tRNAs). In contrast, MA-modified vesicles did not affect the stiffness of POPC membranes, wherein no conformational change in tRNAs was observed in the presence of POPC/MA vesicles. Analyses of the pH-dependent fluorescence emission of TNS suggested that SG and MA molecules render the membrane surfaces cationic and anionic, respectively, which was also revealed by zeta potential measurements. Our results enabled the construction of a model of the head group orientation of zwitterionic POPC molecules controlled by modification with guanidinium derivatives. The results also indicate the possibility to regulate the interaction and conformation of biological molecules, such as nucleic acid.

  18. Under-oil superhydrophilic wetted PVDF electrospun modified membrane for continuous gravitational oil/water separation with outstanding flux.

    PubMed

    Obaid, M; Mohamed, Hend Omar; Yasin, Ahmed S; Yassin, Mohamed A; Fadali, Olfat A; Kim, HakYong; Barakat, Nasser A M

    2017-10-15

    Water in the world is becoming an increasingly scarce commodity and the membrane technology is a most effective strategy to address this issue. However, the fouling and low flux of the polymeric membrane remains the big challenges. Novel modified Polyvinylidene fluoride (PVDF) membrane was introduced, in this work, using a novel treatment technique for an electrospun polymeric PVDF membrane to be used in oil/water separation systems. The Characterizations of the modified and pristine membranes showed distinct changes in the phase and crystal structure of the membrane material as well as the wettability. The modification process altered the surface morphology and structure of the membrane by forming hydrophilic microspheres on the membrane surface. Therefore, the proposed treatment converts the membrane from highly hydrophobic to be a superhydrophilic under-oil when wetted with water. Accordingly, in the separation of oil/water mixtures, the modified membrane can achieve an outstanding flux of 20664 L/m(2). hr under gravity, which is higher than the pristine membrane by infinite times. Moreover, in the separation of the emulsion, a high flux of 2727 L/m(2). h was achieved. The results exhibited that the modified membrane can treat a huge amount of oily water with a minimal energy consumption. The corresponding separation efficiencies of both of oil/water mixtures and emulsion are more than 99%. The achieved characteristics for the modified and pristine membranes could be exploited to design a novel continuous system for oil/water separation with an excellent efficiency. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. [Transport of large organic ions through syringomycin channels in the membranes containing dipole modifiers].

    PubMed

    Efimova, S S; Ostroumova, O S; Malev, V V; Shchagina, L V

    2011-01-01

    The effect of the membrane dipole potential (Phid) on a conductance and a steady-state number of functioning channels formed by cyclic lipodepsipeptide syringomycin E (SRE) in bilayer lipid membranes made from phosphocholine and bathed in 0.4 M solution of sodium salts of aspartate, gluconate and chloride was shown. The magnitude of Phid was varied with the introduction to membrane bathing solutions of phloretin, which reduces the Phid, and RH 421, increasing the Phid. It was established that in all studied systems the increase in the membrane dipole potential cause a decrease in the steady-state number of open channels. In the systems containing sodium salts of aspartate (Asp) or gluconate (Glc), changes in the number of functioning channels are in an order of magnitude smaller than in systems containing sodium chloride. At the same time, the conductance (g) of single SRE-channels on the membranes bathed in NaCI solution increases with the increase in Phid, and in the systems containing NaAsp or NaGlc the conductance of single channels does not depend on the Phid. The latter is due to the lack of cation/anion selectivity of the SRE-channels in these systems. The different channel-forming activity of SRE in the experimental systems is defined by the gating charge of the channel and the partition coefficient of the dipole modifiers between the lipid and aqueous phases.

  20. Wetting and absorption of water drops on Nafion films.

    PubMed

    Goswami, Sharonmoyee; Klaus, Shannon; Benziger, Jay

    2008-08-19

    Water drops on Nafion films caused the surface to switch from being hydrophobic to being hydrophilic. Contact angle hysteresis of >70 degrees between advancing and receding values were obtained by the Wilhelmy plate technique. Sessile drop measurements were consistent with the advancing contact angle; the sessile drop contact angle was 108 degrees . Water drop adhesion, as measured by the detachment angle on an inclined plane, showed much stronger water adhesion on Nafion than Teflon. Sessile water and methanol drops caused dry Nafion films to deflect. The flexure went through a maximum with time. Flexure increased with contact area of the drop, but was insensitive to the film thickness. Methanol drops spread more on Nafion and caused larger film flexure than water. The results suggest that the Nafion surface was initially hydrophobic but water and methanol drops caused hydrophilic sulfonic acid domains to be drawn to the Nafion surface. Local swelling of the film beneath the water drop caused the film to buckle. The maximum flexure is suggested to result from motion of a water swelling front through the Nafion film.

  1. Blood compatibility comparison for polysulfone membranes modified by grafting block and random zwitterionic copolymers via surface-initiated ATRP.

    PubMed

    Xiang, Tao; Zhang, Li-Sha; Wang, Rui; Xia, Yi; Su, Bai-Hai; Zhao, Chang-Sheng

    2014-10-15

    For blood-contacting materials, good blood compatibility, especially good anticoagulant property is of great importance. Zwitterionic polymers have been proved to be resistant to nonspecific protein adsorption and platelet adhesion; however, their anticoagulant property is always inadequate. In this study, two kinds of zwitterionic copolymers (sulfobetaine methacrylate and sodium p-styrene sulfonate random copolymer and block copolymer) with sulfonic groups were covalently grafted from polysulfone (PSf) membranes via surface-initiated atom transfer radical polymerization (SI-ATRP) to improve blood compatibility. Field emission scanning electron microscopy (FE-SEM), attenuated total reflectance-Fourier transform infrared spectra (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and static water contact angle (WCA) were applied to characterize the morphologies, chemical compositions and hydrophilicity of the modified membranes. All the zwitterionic copolymer modified membranes showed improved blood compatibility, especially the anticoagulant property was obviously enhanced compared to the pristine PSf and simple zwitterionic polymer modified membranes. We also found that the random copolymer modified membranes showed better resistance to platelet adhesion than the block copolymer modified membranes. The zwitterionic copolymer modified membranes with integrated antifouling property and blood compatibility provided wide choice for specific applications such as hemodialysis, hemofiltration, and plasma separation. Copyright © 2014 Elsevier Inc. All rights reserved.

  2. Fourier-transform infrared studies on cation binding to native and modified purple membranes.

    PubMed

    Duñach, M; Padrós, E; Muga, A; Arrondo, J L

    1989-10-31

    Fourier-transform infrared spectroscopy has been used to examine the structural differences in the protein moiety between the native purple and the deionized blue membranes, both at pH 5.0. The spectra demonstrate that deionization of purple membrane decreases the content of the distorted alpha II-helices in favor of the more common alpha I-helices. Changes in the signals from beta-turns are also observed. The changes corresponding to the carboxyl groups suggest that deionization leads to a decrease in the strength of the hydrogen bonds involving carboxyl groups. Most of these effects are reversed progressively upon binding of one to five Mn2+ per bacteriorhodopsin to the deionized membrane. Binding of Hg2+ to the deionized membranes does not restore the purple color but induces global changes similar to, but less intense than, those brought about by Mn2+ binding. However, the effects attributed to the carboxyl groups are opposite to those found for Mn2+. Schiff base reduction or bleaching induces a decrease of the content of the alpha II-helix in favor of the alpha I-helix and a decrease in the strength of hydrogen bonds to carboxyl groups. Deionization of these modified membranes leads to a further loss in the alpha II content. These results indicate a conformational rearrangement of the protein structure between the native purple membrane and the deionized membrane, which could arise from surface potential changes elicited by bound cations. The changes observed in the carboxyl groups suggest that some of them are located structurally close to the retinal environment and may be involved in cation binding.

  3. A new incorporation method of metallic precursors into a nafion film via a drying process for the preparation of metallic nanocatalysts/nafion.

    PubMed

    Lee, Jae-Young; Lee, Woo-Kum; Hong, Sung-Wan; Lee, Hong-Ki

    2013-12-01

    A new simple drying process was developed in order to prepare a metallic nanocatalysts/Nafion for self-humidifying membrane in a proton-exchange membrane fuel cell (PEMFC). Metallic precursors such as platinum(ll) bis(acetylacetonate) or palladium(ll) bis(acetylacetonate) was sublimed and simultaneously penetrated into the surface of a Nafion film. And then it was reduced to Pt or Pd nanoparticles beneath the film surface without a special reducing agent in a glass reactor of N2 atmosphere at 180 degrees C for 5, 10, 30 and 60 min, respectively. The morphology and distribution of the Pt or Pd nanoparticles were observed by transmission electron microscopy (TEM) and elemental analysis was carried out by an energy dispersive spectroscopy (EDS), and we found that the penetration depth of the metallic nanoparticles and the particle sizes increased with increasing exposure time to the metallic precursors, and the particle size at the surface area was larger than that at the deeper area.

  4. Polyacrylonitrile nanofiber membranes modified with ionically crosslinked polyelectrolyte multilayers for the separation of ionic impurities.

    PubMed

    Rajesh, Sahadevan; Zhao, Yong; Fong, Hao; Menkhaus, Todd J

    2016-11-03

    Nanofiltration membranes were prepared by forming multilayers of branched polyethylenimine (BPEI) and polyacrylic acid (PAA) on a polyacrylonitrile (PAN) nanofibrous mat by layer-by-layer (LbL) assembly. The degree of ionization (DI) of PAA, estimated using FTIR spectra both in the absence and presence of added salt, was shown to have a strong influence on the BPEI/PAA film growth. BPEI/PAA multilayers grew exponentially when the DI of PAA was less than 30%, or when the pH of PAA during LbL formation was less than 3.5. Subsequently, BPEI/PAA multilayers were formed on the PAN nanofiber mats by depositing the polyelectrolytes at the experimental conditions that favored maximum film growth. The separation layer formed with 15 bilayers of BPEI/PAA has a thickness of 1100 nm. PAA ionization was favored within the BPEI/PAA multilayers due to the presence of abundant amine groups in BPEI, and as a result, a strong negative charge was seen for PAN nanofibrous membranes for solution conditions above pH 4.5. Nanofiber membranes modified with 15 bilayers of BPEI/PAA multilayers at an applied pressure of 4 bar had a pure water flux of 19.7 Lm(-2) h(-1) and a MgSO4 rejection of 98.7%. This performance represents 1.6 times higher flux and 1.1 times higher salt rejection than the multilayers formed on a conventional asymmetric polymeric support. The higher separation and higher flux capabilities of BPEI/PAA multilayer modified PAN nanofiber membranes was due to the combined effect of high charge density and high porosity of the nanofiber membranes.

  5. Preparation and characterization of modified nano-porous PVDF membrane with high antifouling property using UV photo-grafting

    NASA Astrophysics Data System (ADS)

    Rahimpour, A.; Madaeni, S. S.; Zereshki, S.; Mansourpanah, Y.

    2009-05-01

    In this study, the poly(vinylidene fluoride) (PVDF) membrane was prepared via immersion precipitation technique and modified by UV photo-grafting of hydrophilic monomers on the top membrane surface. Acrylic acid (AA) and 2-hydroxyethylmethacrylate (HEMA) as acrylic monomers and 2,4-phenylenediamine (PDA) and ethylene diamine (EDA) as amino monomers were used at different concentrations to modify the membrane and improve the hydrophilicity with less fouling tendency. Moreover the presence of benzophenon as photo-initiator for grafting the hydrophilic monomers onto PVDF membrane surface was elucidated. The virgin and modified PVDF membranes were characterized by contact angle, ATR-FTIR, SEM and cross-flow filtration. The contact angle measurements demonstrated that the hydrophilicities of the membranes were significantly enhanced by UV photo-grafting of hydrophilic monomers onto the membrane surface. The ATR-FTIR confirmed the occurrence of modification on PVDF membrane by UV photo-grafting. The pure water flux of membranes was declined by UV photo-grafting but the milk water permeation and protein rejection were slightly improved. Moreover the antifouling properties and flux recovery of PVDF membrane were improved by UV photo-grafting of hydrophilic monomers.

  6. Antibacterial activities of surface modified electrospun poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) fibrous membranes

    NASA Astrophysics Data System (ADS)

    Yao, Chen; Li, Xinsong; Neoh, K. G.; Shi, Zhilong; Kang, E. T.

    2009-01-01

    Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membrane, with its excellent chemical and mechanical properties, has good potential for broad applications. However, due to its hydrophobic nature, microbial colonization is commonly encountered. In this work, electrospun PVDF-HFP fibrous membranes were surface modified by poly(4-vinyl- N-alkylpyridinium bromide) to achieve antibacterial activities. The membranes were first subjected to plasma pretreatment followed by UV-induced surface graft copolymerization of 4-vinylpyridine (4VP) and quaternization of the grafted pyridine groups with hexylbromide. The chemical composition of the surface modified PVDF-HFP electrospun membranes was studied by X-ray photoelectron spectroscopy (XPS). The morphology and mechanical properties of pristine and surface modified PVDF-HFP fibrous membranes were characterized by scanning electron microscopy (SEM) and tensile test, respectively. The antibacterial activities of the modified electrospun PVDF-HFP fibrous membranes were assessed against Gram-positive Staphylococcus aureus ( S. aureus) and Gram-negative Escherichia coli ( E. coli). The results showed that the PVDF-HFP fibrous membranes modified with quaternized pyridinium groups are highly effective against both bacteria with killing efficiency as high as 99.9999%.

  7. PVDF-HFP/ether-modified polysiloxane membranes obtained via airbrush spraying as active separators for application in lithium ion batteries.

    PubMed

    Seidel, S M; Jeschke, S; Vettikuzha, P; Wiemhöfer, H-D

    2015-08-04

    Improved hybrid polymer electrolyte membranes are introduced based on ether-modified polysiloxanes and poly(vinylidene fluoride-co-hexafluoropropylene) yielding a safe separator membrane, which is able to be sprayed directly onto lithium ion battery active materials, with an active role for enhanced ion transport.

  8. The effect of photodynamic action on leakage of ions through liposomal membranes that contain oxidatively modified lipids.

    PubMed

    Ytzhak, Shany; Ehrenberg, Benjamin

    2014-01-01

    Singlet oxygen, created in photosensitization, peroxidizes unsaturated fatty acids of the membrane's lipids. This generates alcoholic or aldehyde groups at double bonds' breakage points. In a previous study, we examined the leakage of a K(+) -induced cross-membrane electric potential of liposomes that undergo photosensitization. The question remains to what extent peroxidized lipids can compromise the stability of the membrane. In this study, we studied the effect of the oxidatively modified lipids PGPC and ALDOPC in the membrane on its stability, by monitoring the membrane electric potential with the potentiometric dye DiSC(2)(5). As the content of the modified lipids increases the membrane becomes less stable, and even at just 2% of the modified lipids the membrane's integrity is affected, in respect to the leakage of ions through it. When the liposomes that contain the modified lipids undergo photosensitization by hematoporphyrin, the lipid bilayer becomes even more unstable and passage of ions is accelerated. We conclude that the existence of lipids with a shortened fatty acid that is terminated by a carboxylic acid or an aldehyde and more so when photosensitized damage occurs to unsaturated fatty acids in lecithin, add up to a critical alteration of the membrane, which becomes leaky to ions.

  9. Nafion-tris(2-2'-bipyridyl)ruthenium(II) Ultrathin Langmuir-Schaefer films: redox catalysis and electrochemiluminescent properties.

    PubMed

    Bertoncello, Paolo; Dennany, Lynn; Forster, Robert J; Unwin, Patrick R

    2007-10-01

    A simple procedure to incorporate tris(2-2'-bipyridyl)ruthenium(II), [Ru(bpy)3]2+, into Nafion Langmuir-Schaefer (LS) films is described. Nafion LS films (tens of nanometers thick) were formed on quartz glass and indium tin oxide (ITO) directly from Nafion-[Ru(bpy)3]2+ Langmuir films assembled at the water-air interface. This procedure allowed the direct incorporation of [Ru(bpy)3]2+ into Nafion films without the need for subsequent loading. UV-vis spectroscopy confirmed the successful incorporation of [Ru(bpy)3]2+ within the LS films and showed that the amount of [Ru(bpy)3]2+ immobilized in this way scaled with film thickness. Voltammetric studies on ITO-modified electrodes confirmed the successful incorporation of [Ru(bpy)3]2+ and demonstrated that [Ru(bpy)3]2+ was retained within the ultrathin films over a long time scale. These electrodes were tested for the electrocatalytic reduction of tripropylamine. Significant catalysis was observed due to the rapid turnover of [Ru(bpy)3]2+/3+ between the electrode surface and outer boundary of the film, as a direct consequence of the ultrathin film dimensions. Concomitant electrochemiluminescence (ECL) was demonstrated highlighting the potential of this material for sensing applications.

  10. A sensitive impedimetric DNA biosensor for the determination of the HIV gene based on graphene-Nafion composite film.

    PubMed

    Gong, Qiaojuan; Wang, Yongdong; Yang, Haiying

    2017-03-15

    An impedimetric HIV-1 gene biosensor has been developed based on graphene-Nafion composite film. The biosensor was fabricated by adsorbing the single-stranded DNA (ssDNA) on graphene-Nafion modified on the surface of glassy carbon electrode via the π-π* stacking interactions. As the negative ssDNA and the steric hindrance, the electron transfer resistance of the electrodes toward the [Fe(CN)6](3-/4) redox couple was difficult, the electron transfer resistance value increased. In the measurement of HIV gene, ssDNA probe with the target DNA to form double-stranded DNA (dsDNA), the formation of helix induced dsDNA to release from the surface of the biosensor. The decrease in the electron transfer resistance was in logarithmically direct proportion to the concentration of HIV-1 gene over a range from 1.0×10(-13) to 1.0×10(-10)M. The detection limit of this sensor was 2.3×10(-14)M. It was found that Nafion could not only stabilize graphene but also increase the dispersion of graphene. The results demonstrate that this graphene-Nafion biosensor possesses good selectivity, acceptable stability and reproducibility for HIV-1 gene detection.

  11. Synthesis of modified polymer inclusion membranes for photo-electrodeposition of cadmium using polarized electrodes.

    PubMed

    Cherif, Asma Yahia; Arous, Omar; Amara, Mourad; Omeiri, Said; Kerdjoudj, Hacène; Trari, Mohamed

    2012-08-15

    In this work, we have developed a novel class of polymeric inclusion membranes (PIMs) for the cations separation. The membrane is made up of cellulose triacetate modified by poly-electrolytes (poly-phosphoric acid, polyvinyl pyrolidone, polyacrylic acid, polyvinyl alcohol and poly-anetholsulfonic acid) using 2-hydroxy-5-dodecylbenzaldehyde incorporated into the polymer as carrier and tris ethyl hexyl phosphate or glycerine as plasticizers. Different PIMs are synthesized and characterized by the Fourier transform infrared, X-ray diffraction, thermal analysis and scanning electron microscopy. The influence of the membrane nature is studied using supports with different physical characteristics (porosity, thickness, hydrophobia). As application, the transport of Cd(2+) using PIMs coupled with photo-electrodes is investigated. The photo-catalytic results indicate that the combined system p-CuFeO(2)/membrane/n-WO(3) enhances considerably the electrons transfer toward the delafossite CuFeO(2). The position of the conduction band of CuFeO(2) is looked to be the key issue for the photo electrochemical Cd(2+) reduction. Copyright © 2012 Elsevier B.V. All rights reserved.

  12. Reduction of thrombogenicity of PVC-based sodium selective membrane electrodes using heparin-modified chitosan.

    PubMed

    Badr, Ibrahim H A; Gouda, M; Abdel-Sattar, R; Sayour, Hossam E M

    2014-01-01

    Heparin-modified chitosan (H-chitosan) membrane was utilized to enhance biocompatibility of sodium selective membrane electrode based on the highly thrombogenic polyvinyl chloride (PVC). Sodium ion sensing film was prepared using PVC, sodium ionophore-X, potassium tetrakis(chlorophenyl)-borate, and o-nitrophenyloctylether. The PVC-based sensing film was sandwiched to chitosan or H-chitosan to prevent platelet adhesion on the surface of PVC. Potentiometric response characteristics of PVC-chitosan and PVC-H-chitosan membrane electrodes were found to be comparable to that of a control PVC based sodium-selective electrode. This indicates that chitosan and H-chitosan layers do not alter the response behaviour of the PVC-based sensing film. Biocompatibility of H-chitosan was confirmed by in vitro platelet adhesion study. The platelet adhesion investigations indicated that H-chitosan film is less thrombogenic compared to PVC, which could result in enhancement of biocompatibility of sodium selective membrane electrodes based on PVC, while maintaining the overall electrochemical performance of the PVC-based sensing film.

  13. Biodegradation of phenol by immobilized Aspergillus awamori NRRL 3112 on modified polyacrylonitrile membrane.

    PubMed

    Yordanova, G; Ivanova, D; Godjevargova, T; Krastanov, A

    2009-09-01

    Covalent immobilization of Aspergillus awamori NRRL 3112 was conducted onto modified polyacrylonitrile membrane with glutaraldehyde as a coupling agent. The polymer carrier was preliminarily modified in an aqueous solution of NaOH and 1,2-diaminoethane. The content of amino groups was determined to be 0.58 mgeq g(-1). Two ways of immobilization were used-in the presence of 0.2 g l(-1) phenol and without phenol. The capability of two immobilized system to degrade phenol (concentration-0.5 g l(-1)) as a sole carbon and energy source was investigated in batch experiments. Seven cycles of phenol biodegradation were conducted. Better results were obtained with the immobilized system prepared in the presence of phenol, regarding degradation time and phenol biodegradation rate. Scanning electron micrographs of the polyacrylonitrile membrane/immobilized Aspergillus awamori NRRL at the beginning of repeated batch cultivation and after the 7th cycle were compared. After the 7th cycle of cultivation the observations showed large groups of cells. The results from the batch experiments with immobilized system were compared to the results produced by the free strain. Phenol biodegradation experiments were carried out also in a bioreactor with spirally wound membrane with bound Aspergillus awamori NRRL 3112 in a regime of recirculation. 10 cycles of 0.5 g l(-1) phenol biodegradation were run consecutively to determine the degradation time and rate for each cycle. The design of the bioreactor appeared to be quite effective, providing large membrane surface to bind the strain.

  14. Mesoporous fluorocarbon-modified silica aerogel membranes enabling long-term continuous CO2 capture with large absorption flux enhancements.

    PubMed

    Lin, Yi-Feng; Chen, Chien-Hua; Tung, Kuo-Lun; Wei, Te-Yu; Lu, Shih-Yuan; Chang, Kai-Shiun

    2013-03-01

    The use of a membrane contactor combined with a hydrophobic porous membrane and an amine absorbent has attracted considerable attention for the capture of CO2 because of its extensive use, low operational costs, and low energy consumption. The hydrophobic porous membrane interface prevents the passage of the amine absorbent but allows the penetration of CO2 molecules that are captured by the amine absorbent. Herein, highly porous SiO2 aerogels modified with hydrophobic fluorocarbon functional groups (CF3 ) were successfully coated onto a macroporous Al2 O3 membrane; their performance in a membrane contactor for CO2 absorption is discussed. The SiO2 aerogel membrane modified with CF3 functional groups exhibits the highest CO2 absorption flux and can be continuously operated for CO2 absorption for extended periods of time. This study suggests that a SiO2 aerogel membrane modified with CF3 functional groups could potentially be used in a membrane contactor for CO2 absorption. Also, the resulting hydrophobic SiO2 aerogel membrane contactor is a promising technology for large-scale CO2 absorption during the post-combustion process in power plants. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Photocurrent generation from thylakoid membranes on osmium-redox-polymer-modified electrodes.

    PubMed

    Hamidi, Hassan; Hasan, Kamrul; Emek, Sinan Cem; Dilgin, Yusuf; Åkerlund, Hans-Erik; Albertsson, Per-Åke; Leech, Dónal; Gorton, Lo

    2015-03-01

    Thylakoid membranes (TMs) are uniquely suited for photosynthesis owing to their distinctive structure and composition. Substantial efforts have been directed towards use of isolated photosynthetic reaction centers (PRCs) for solar energy harvesting, however, few studies investigate the communication between whole TMs and electrode surfaces, due to their complex structure. Here we report on a promising approach to generate photosynthesis-derived bioelectricity upon illumination of TMs wired with an osmium-redox-polymer modified graphite electrode, and generate a photocurrent density of 42.4 μA cm(-2). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Poly(imide)/Organically-Modified Montmorillonite Nanocomposite as a Potential Membrane for Alkaline Fuel Cells

    PubMed Central

    Battirola, Liliane C.; Gasparotto, Luiz H. S.; Rodrigues-Filho, Ubirajara P.; Tremiliosi-Filho, Germano

    2012-01-01

    In this work we evaluated the potentiality of a poly(imide) (PI)/organically-modified montmorillonite (O-MMT) nanocomposite membrane for the use in alkaline fuel cells. Both X-ray diffraction and scanning electron microscopy revealed a good dispersion of O-MMT into the PI matrix and preservation of the O-MMT layered structure. When compared to the pure PI, the addition of O-MMT improved thermal stability and markedly increased the capability of absorbing electrolyte and ionic conductivity of the composite. The results show that the PI/O-MMT nanocomposite is a promising candidate for alkaline fuel cell applications. PMID:24958290

  17. Multifunctional Graphene/Platinum/Nafion Hybrids via Ice Templating

    SciTech Connect

    Estevez, Luis; Kelarakis, Antonios; Gong, Qianming; Da’as, Eman Husni; Giannelis, Emmanuel P.

    2011-04-27

    We report the synthesis of multifunctional hybrids in both films and bulk form, combining electrical and ionic conductivity with porosity and catalytic activity. The hybrids are synthesized by a two-step process: (a) ice templation of an aqueous suspension comprised of Nafion, graphite oxide, and chloroplatinic acid to form a microcellular porous network and (b) mild reduction in hydrazine or monosodium citrate which leads to graphene-supported Pt nanoparticles on a Nafion scaffold

  18. Comparing selected morphological models of hydrated Nafion using large scale molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Knox, Craig K.

    Experimental elucidation of the nanoscale structure of hydrated Nafion, the most popular polymer electrolyte or proton exchange membrane (PEM) to date, and its influence on macroscopic proton conductance is particularly challenging. While it is generally agreed that hydrated Nafion is organized into distinct hydrophilic domains or clusters within a hydrophobic matrix, the geometry and length scale of these domains continues to be debated. For example, at least half a dozen different domain shapes, ranging from spheres to cylinders, have been proposed based on experimental SAXS and SANS studies. Since the characteristic length scale of these domains is believed to be ˜2 to 5 nm, very large molecular dynamics (MD) simulations are needed to accurately probe the structure and morphology of these domains, especially their connectivity and percolation phenomena at varying water content. Using classical, all-atom MD with explicit hydronium ions, simulations have been performed to study the first-ever hydrated Nafion systems that are large enough (~2 million atoms in a ˜30 nm cell) to directly observe several hydrophilic domains at the molecular level. These systems consisted of six of the most significant and relevant morphological models of Nafion to-date: (1) the cluster-channel model of Gierke, (2) the parallel cylinder model of Schmidt-Rohr, (3) the local-order model of Dreyfus, (4) the lamellar model of Litt, (5) the rod network model of Kreuer, and (6) a 'random' model, commonly used in previous simulations, that does not directly assume any particular geometry, distribution, or morphology. These simulations revealed fast intercluster bridge formation and network percolation in all of the models. Sulfonates were found inside these bridges and played a significant role in percolation. Sulfonates also strongly aggregated around and inside clusters. Cluster surfaces were analyzed to study the hydrophilic-hydrophobic interface. Interfacial area and cluster volume

  19. Interfacial interactions in aprotic ionic liquid based protonic membrane and its correlation with high temperature conductivity and thermal properties.

    PubMed

    Mistry, Mayur K; Subianto, Surya; Choudhury, Namita Roy; Dutta, Naba K

    2009-08-18

    Novel supported liquid membranes (SLMs) have been developed by impregnating Nafion and Hyflon membranes with ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMI-BTSI). These supported liquid membranes were characterized in terms of their ionic liquid uptake behavior, leaching of ionic liquid by water, thermal stability, mechanical properties, glass transition temperature, ion exchange capacity, and proton conductivity. In general, modified membranes are more flexible than unmodified samples due to the plasticization effects of the ionic liquid. However, these supported liquid membranes exhibit a significant increase in their operational stability and proton conductivity over unmodified membranes. We also demonstrate that proton conductivity of these supported liquid membranes allows conduction of protons in anhydrous conditions with conductivity increasing with temperature. Conductivity of up to 3.58 mS cm(-1) has been achieved at 160 degrees C in dry conditions, making these materials promising for various electrochemical applications.

  20. Design of functional hollow fiber membranes modified with phospholipid polymers for application in total hemopurification system.

    PubMed

    Ye, Sang Ho; Watanabe, Junji; Takai, Madoka; Iwasaki, Yasuhiko; Ishihara, Kazuhiko

    2005-08-01

    In this study, we prepared cellulose acetate (CA) hollow fiber membranes (HFMs) modified with poly (2-methacryloyloxyethyl phosphorylcholine (MPC)-co-n-butyl methacrylate)(PMB30 and PMB80) by the dry-jet wet spinning process. The physical and chemical structures of the HFMs were controlled in order to design highly functional HFMs that had suitable performance to each targeting HFM device used in a total hemopurification system. The CA HFMs modified with the MPC polymer, such as CA/PMB30, CA/PMB80, and CA/PMB30-80 HFMs, were successfully prepared by controlling the spinning conditions. The modified HFMs showed an improved performance in solute and water permeability, due to the modification by the hydrophilic MPC polymers. The CA/PMB30 and CA/PMB80 showed a high potential in an application for a high performance hemocompatible plasmapheresis and hemofilter device. Furthermore, CA/PMB30-80 HFM, modified asymmetrically with PMB30 and PMB80, showed a potential for application in an advanced total hemopurification system as a highly functional scaffold for a biohybrid renal tubule, or a liver assist bioreactor device, because of their enhanced permeability, hemocompatibility, and cytocompatibility.

  1. Exploiting lipopolysaccharide-induced deformation of lipid bilayers to modify membrane composition and generate two-dimensional geometric membrane array patterns

    PubMed Central

    Adams, Peter G.; Swingle, Kirstie L.; Paxton, Walter F.; Nogan, John J.; Stromberg, Loreen R.; Firestone, Millicent A.; Mukundan, Harshini; Montaño, Gabriel A.

    2015-01-01

    Supported lipid bilayers have proven effective as model membranes for investigating biophysical processes and in development of sensor and array technologies. The ability to modify lipid bilayers after their formation and in situ could greatly advance membrane technologies, but is difficult via current state-of-the-art technologies. Here we demonstrate a novel method that allows the controlled post-formation processing and modification of complex supported lipid bilayer arrangements, under aqueous conditions. We exploit the destabilization effect of lipopolysaccharide, an amphiphilic biomolecule, interacting with lipid bilayers to generate voids that can be backfilled to introduce desired membrane components. We further demonstrate that when used in combination with a single, traditional soft lithography process, it is possible to generate hierarchically-organized membrane domains and microscale 2-D array patterns of domains. Significantly, this technique can be used to repeatedly modify membranes allowing iterative control over membrane composition. This approach expands our toolkit for functional membrane design, with potential applications for enhanced materials templating, biosensing and investigating lipid-membrane processes. PMID:26015293

  2. Exploiting lipopolysaccharide-induced deformation of lipid bilayers to modify membrane composition and generate two-dimensional geometric membrane array patterns

    DOE PAGES

    Adams, Peter G.; Swingle, Kirstie L.; Paxton, Walter F.; ...

    2015-05-27

    Supported lipid bilayers have proven effective as model membranes for investigating biophysical processes and in development of sensor and array technologies. The ability to modify lipid bilayers after their formation and in situ could greatly advance membrane technologies, but is difficult via current state-of-the-art technologies. Here we demonstrate a novel method that allows the controlled post-formation processing and modification of complex supported lipid bilayer arrangements, under aqueous conditions. We exploit the destabilization effect of lipopolysaccharide, an amphiphilic biomolecule, interacting with lipid bilayers to generate voids that can be backfilled to introduce desired membrane components. We further demonstrate that when usedmore » in combination with a single, traditional soft lithography process, it is possible to generate hierarchically-organized membrane domains and microscale 2-D array patterns of domains. Significantly, this technique can be used to repeatedly modify membranes allowing iterative control over membrane composition. This approach expands our toolkit for functional membrane design, with potential applications for enhanced materials templating, biosensing and investigating lipid-membrane processes.« less

  3. Exploiting lipopolysaccharide-induced deformation of lipid bilayers to modify membrane composition and generate two-dimensional geometric membrane array patterns

    SciTech Connect

    Adams, Peter G.; Swingle, Kirstie L.; Paxton, Walter F.; Nogan, John J.; Stromberg, Loreen R.; Firestone, Millicent A.; Mukundan, Harshini; Montaño, Gabriel A.

    2015-05-27

    Supported lipid bilayers have proven effective as model membranes for investigating biophysical processes and in development of sensor and array technologies. The ability to modify lipid bilayers after their formation and in situ could greatly advance membrane technologies, but is difficult via current state-of-the-art technologies. Here we demonstrate a novel method that allows the controlled post-formation processing and modification of complex supported lipid bilayer arrangements, under aqueous conditions. We exploit the destabilization effect of lipopolysaccharide, an amphiphilic biomolecule, interacting with lipid bilayers to generate voids that can be backfilled to introduce desired membrane components. We further demonstrate that when used in combination with a single, traditional soft lithography process, it is possible to generate hierarchically-organized membrane domains and microscale 2-D array patterns of domains. Significantly, this technique can be used to repeatedly modify membranes allowing iterative control over membrane composition. This approach expands our toolkit for functional membrane design, with potential applications for enhanced materials templating, biosensing and investigating lipid-membrane processes.

  4. Subsecond Morphological Changes in Nafion during Water Uptake Detected by Small-Angle X-ray Scattering

    SciTech Connect

    Kusoglu, Ahmet; Modestino, Miguel A.; Hexemer, Alexander; Segalman, Rachel A.; Weber, Adam Z.

    2011-11-09

    The ability of the Nafion membrane to absorb water rapidly and create a network of hydrated interconnected water domains provides this material with an unmatched ability to conduct ions through a chemically and mechanically robust membrane. The morphology and composition of these hydrated membranes significantly affects their transport properties and performance. This research demonstrates that differences in interfacial interactions between the membranes exposed to vapor or liquid water can cause significant changes in kinetics of water uptake. In situ small-angle X-ray scattering (SAXS) experiments captured the rapid swelling of the membrane in liquid water with a nanostructure rearrangement on the order of seconds. For membranes in contact with water vapor, morphological changes are four orders-of-magnitude slower than in liquid water, suggesting that interfacial resistance limits the penetration of water into the membrane. Furthermore, upon water absorption from liquid water, a structural rearrangement from a distribution of spherical and cylindrical domains to exclusively cylindrical-like domains is suggested. These differences in water-uptake kinetics and morphology provide a new perspective into Schroeder's paradox, which dictates a different water content for vapor- and liquid-equilibrated ionomers at unit activity. Lastly, the findings of this work provide critical insights into the fast kinetics of water absorption of the Nafion membrane, which can aid in the design of energy conversion devices that operate under frequent changes in environmental conditions.

  5. Blood compatibility and permeability of heparin-modified polysulfone as potential membrane for simultaneous hemodialysis and LDL removal.

    PubMed

    Huang, Xiao-Jun; Guduru, Deepak; Xu, Zhi-Kang; Vienken, Jörg; Groth, Thomas

    2011-01-10

    Heparin was covalently immobilized on PSf membranes to obtain a dialysis membrane with high affinity for LDL. WCA and streaming potential measurements were performed to investigate wettability and surface charge of the membranes. The morphology of the membranes was investigated by SEM. An ELISA was used to measure the adsorption and desorption of LDL on plain and modified PSf. Blood compatibility was studied by measurement of thrombin time, partial thromboplastin time, kallikrein activity and platelet adhesion. It was found that the blood compatibility of the membrane was improved by covalent immobilization of heparin at its surface. However, PSf-Hep membrane showed higher flux recovery after BSA solution filtration, which revealed antifouling property of PSf-Hep membranes.

  6. Enhanced antifouling behaviours of polyvinylidene fluoride membrane modified through blending with nano-TiO2/polyethylene glycol mixture

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Wang, Zhiwei; Zhang, Xingran; Zheng, Xiang; Wu, Zhichao

    2015-08-01

    Titanium dioxide (TiO2) nanoparticles/polyethylene glycol (PEG) mixture was used to modify polyvinylidene fluoride (PVDF) membranes aiming to improve their antifouling ability. The use of PEG could improve the dispersion of nanoparticles thanks to steric hindrance effects. Test results showed that compared to the original PVDF membrane, the modified membranes had higher hydrophilicity and lower negative Zeta potential, facilitating membrane fouling control. The extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) analysis indicated that the addition of TiO2 nanoparticles improved their electron donor monopolarity, i.e., enhanced electron-donating ability. The interaction energy barrier between soluble microbial products (SMP) and membrane surfaces was also improved, indicating that anti-fouling ability of the modified membrane was elevated. The optimal dosage of nano-TiO2 was found to be 0.15%, and further increase of dosage resulted in the aggregation of nanoparticles which consequently impaired the modification efficiency. Quartz crystal microbalance with dissipation (QCM-D) monitoring and SMP filtration tests confirmed the antifouling ability of the modified membrane.

  7. DEVELOPMENT OF HIGH TEMPERATURE MEMBRANES AND IMPROVED CATHODE CATALYSTS; PROJECT PERIOD JANUARY 1, 2002 - DECEMBER 31, 2005

    SciTech Connect

    Lesia Protsailo

    2006-04-20

    Polymer Electrolyte Membranes (PEMs) currently available for fuel cell development work are limited to the temperature range of 60-80°C. For mass commercialization in the transportation arena, three important disadvantages that are linked with the relatively low operating temperature range need to be addressed. These three disadvantages are: (a) sluggish cathode kinetics, (b) CO poisoning at the anode and (c) inefficient thermal characteristics. All three of the above mentioned disadvantages could be solved by increasing the operating temperature range to 100-120°C. To understand the issues associated with high temperature PEMFCs operation, UTCFC has teamed with leading research groups that possess competencies in the field of polymer chemistry. The subcontractors on the program were investigating modified Nafion® and new non-Nafion® based, reinforced and non-reinforced membrane systems. Nafion® based PEMs rely on using high temperature inorganic solid conductor fillers like phosphotungstic acid. Hydrocarbon membrane systems are based on poly (arylene ether sulfone) polymers, PEEK, PAN, etc.

  8. New modified polyetheretherketone membrane for liver cell culture in biohybrid systems: adhesion and specific functions of isolated hepatocytes.

    PubMed

    De Bartolo, L; Morelli, S; Rende, M; Gordano, A; Drioli, E

    2004-08-01

    There has been growing interest in innovative materials with physico-chemical properties that provide improved blood/cell compatibility. We propose new polymeric membranes made of modified polyetheretherketone (PEEK-WC) as materials with potential for use in biohybrid devices. PEEK-WC exhibits high chemical, thermal stability and mechanical resistance. Owing to its lack of crystallinity this polymer can be used for preparing membranes with cheap and flexible methods. We compared the properties of PEEK-WC membranes to polyurethane membranes prepared using the same phase inverse technique and commercial membranes. The physico-chemical properties of the membranes were characterised by contact angle measurements. The different parameters acid (gamma+), base (gamma-) and Lifshitz-van der Waals (gammaLW) of the surface free energy were calculated according to Good-van Oss's model. We evaluated the cytocompatibility of PEEK-WC membranes by culturing hepatocytes isolated from rat liver. Cell adhesion and metabolic behaviour in terms of ammonia elimination, urea synthesis and protein synthesis were evaluated during the first days of culture. Liver cells adhered and formed three-dimensional aggregates on the most tested membranes. PEEK-WC membranes promoted hepatocyte adhesion most effectively. Urea synthesis, ammonia elimination and protein synthesis improved significantly when cells adhered to PEEK-WC membrane. The considerable metabolic activities of cells cultured on this membrane confirmed the good structural and physico-chemical properties of the PEEK-WC membrane that could be a promising biomaterial for cell culture in biohybrid devices.

  9. Electrically driven biofouling release of a poly(tetrafluoroethylene) membrane modified with an electrically induced reversibly cross-linked polymer.

    PubMed

    Chuo, Tsai-Wei; Wei, Ta-Chin; Chang, Yung; Liu, Ying-Ling

    2013-10-23

    Electrically induced reversible reactions between ferrocene (Fc) and β-cyclodextrin (β-CD) groups have been utilized for preparation of poly(tetrafluoroethylene) (PTFE) membranes exhibiting electrically driven biofouling release properties. PTFE membrane is surface-modified with polymer chains possessing Fc pendant groups. The surface layer is then cross-linked with a difunctional β-CD compound by means of the Fc/β-CD complexation reaction. The electrically induced reversibly cross-linking and de-cross-linking behaviors of the surface layer of the modified PTFE membrane have been characterized with Fourier transform Infrared, X-ray photoelectron spectroscopy, and scanning electron microscopy. The surface-modified PTFE membrane has been fouled with protein absorption. Electrical treatment of the fouled membrane results in a protein detachment from the membrane surface driven by the surface structure change accompanied with the electrically induced de-cross-linking reaction of the Fc/β-CD linkages. A smart membrane exhibiting a novel cleaning technology for membrane fouling has been developed.

  10. Continuous hydrolysis of modified wheat gluten in an enzymatic membrane reactor.

    PubMed

    Cui, Jie; Kong, Xiangzhen; Hua, Yufei; Zhou, Huiming; Liu, Qing

    2011-12-01

    The low solubility of wheat gluten is one of the major limitations to its use in food processing, and enzymatic hydrolysis has been found to be an effective way to prepare more soluble bioactive peptides from gluten. The aim of this study was to prepare bioactive peptides from modified wheat gluten (MWG) in a continuous enzymatic membrane reactor (EMR) that allowed rapid separation of low-molecular-weight peptides from hydrolysates, thus avoiding the disadvantages of batch reaction such as inefficient use of enzymes, inconsistent products due to batch-to-batch variation, substrate-product inhibition, low productivity and excessive hydrolysis. Wheat gluten was modified to decrease its lipid and starch contents in order to prevent membrane fouling. The optimal working conditions for Alcalase to hydrolyse MWG in the EMR were a substrate concentration of 20 g L(-1) , an enzyme/substrate ratio of 0.03, an operating pressure of 0.04 MPa, a temperature of 40 °C and a pH of 9. The operating stability of the EMR (including residual enzyme activity, productivity and capacity) was high. The permeate fractions showed antioxidant activities that were mostly due to low-molecular-weight peptides. A simple theoretical kinetic model was successfully applied to the enzymatic hydrolysis of MWG in the EMR. Modification of wheat gluten made the continuous enzymatic membrane reaction more efficient and the EMR proved to be an effective means of producing peptides with particular properties and bioactivities. The permeate fractions (mainly < 1000 Da) were homogeneous and stable and also showed strong antioxidant activities. Copyright © 2011 Society of Chemical Industry.

  11. Versatile antifouling polyethersulfone filtration membranes modified via surface grafting of zwitterionic polymers from a reactive amphiphilic copolymer additive.

    PubMed

    Zhao, Yi-Fan; Zhang, Pei-Bin; Sun, Jian; Liu, Cui-Jing; Yi, Zhuan; Zhu, Li-Ping; Xu, You-Yi

    2015-06-15

    Here we describe the development of versatile antifouling polyethersulfone (PES) filtration membranes modified via surface grafting of zwitterionic polymers from a reactive amphiphilic copolymer additive. Amphiphilic polyethersulfone-block-poly(2-hydroxyethyl methacrylate) (PES-b-PHEMA) was beforehand designed and used as the blending additive of PES membranes prepared by phase inversion technique. The surface enriched PHEMA blocks on membrane surface acted as an anchor to immobilize the initiating site. Poly(sulfobetaine methacrylate) (PSBMA) were subsequently grafted onto the PES blend membranes by surface-initiated atom transfer radical polymerization (SI-ATRP). The analysis of surface chemistry confirmed the successful grafting of zwitterionic PSBMA brushes on PES membrane surface. The resulted PES-g-PSBMA membranes were capable of separating proteins from protein solution and oil from oil/water emulsion efficiently. Furthermore, the modified membranes showed high hydrophilicity and strongly antifouling properties due to the incorporation of well-defined PSBMA layer. In addition, the PES-g-PSBMA membranes exhibited excellent blood compatibility and durability during the washing process. The developed antifouling PES membranes are versatile and can find their applications in protein filtration, blood purification and oil/water separation, etc.

  12. Organosilane modified silica/polydimethylsiloxane mixed matrix membranes for enhanced propylene/nitrogen separation

    NASA Astrophysics Data System (ADS)

    Beltran, Arnel B.; Nisola, Grace M.; Cho, Eulsaeng; Lee, Erli Eros D.; Chung, Wook-Jin

    2011-10-01

    Gas transport behaviors of oxygen (O 2), nitrogen (N 2) and propylene (C 3H 6) in polydimethylsiloxane (PDMS) mixed matrix membranes (MMM) containing modified silica (SiO 2) nanoparticles are presented. Two surface modified SiO 2 nanoparticles, silica dimethyloctyl silane (Si-DMOS) and silica dimethylphenyl silane (Si-DMPS), were used as fillers. Surface modification was carried out through silanization, which was confirmed via Fourier transform infrared spectroscopy. From elemental analysis, degrees of modifications on Si-DMOS and Si-DMPS were estimated to be 29.64% and 79.89%, respectively. Field emission scanning electron microscopy showed uniform distribution of the modified SiO 2 fillers in MMMs. Both MMMs exhibited reduced O 2 and N 2 permeabilities as compared to pure PDMS, while enhanced C 3H 6 permeabilities were observed. Consequently, C 3H 6/N 2 permselectivities were increased by 35 and 44% in MMMs filled with Si-DMOS and Si-DMPS, respectively. Results revealed that permeability was dependent on penetrant diffusivities, a parameter related to the structure of MMMs. Density measurements and differential scanning calorimetry were performed to elucidate the changes in MMM properties which affected the permeation behaviors of O 2, N 2 and C 3H 6. Overall, both Si-DMOS and Si-DMPS show potential as fillers for the enhancement of PDMS permeation performance.

  13. High functional hollow fiber membrane modified with phospholipid polymers for a liver assist bioreactor.

    PubMed

    Ho Ye, Sang; Watanabe, Junji; Takai, Madoka; Iwasaki, Yasuhiko; Ishihara, Kazuhiko

    2006-03-01

    For practical application of a liver assist system with a tissue-conjugated hollow fiber membrane (HFM) bioreactor used in an extracorporeal therapy, it would require a highly sophisticated HFM which has both hemocompatibility on one side and cytocompatibility on the other side. In this study, we present a cellulose acetate (CA) HFM modified with 2-methacryloyloxyethyl phosphorylcholine (MPC) copolymers (PMB30 (MPC-co-n-butyl methacrylate) and PMA30 (MPC-co-methacrylic acid) for preparing a novel liver assist HFM bioreactor. A CA/PMB-PMA30 HFM modified asymmetrically on the inner and outer surface with the PMB30 and PMA30 was prepared successfully. Analysis with an X-ray photoelectron spectroscope showed that the intensity of the phosphorus atom attributed to the MPC units on the outer surface of the modified HFM was stronger than that of the inner surface. The PMA30 was immobilized on the outer surface of the CA/PMB30 blend HFM by a chemical condensation reaction. The CA/PMB-PMA30 HFM showed good water and solute permeability in comparison with the CA HFM. The morphologies of the adherent hepatocytes were round in shape in comparison with the cells that adhered on CA HFM. Furthermore, hepatocytes cultured on the inner surface of the CA/PMB-PMA30 HFM showed higher functional expression in terms of urea synthesis and albumin synthesis than that of the CA HFM.

  14. A Simple, Cost-Efficient Method to Separate Microalgal Lipids from Wet Biomass Using Surface Energy-Modified Membranes.

    PubMed

    Kwak, Moo Jin; Yoo, Youngmin; Lee, Han Sol; Kim, Jiyeon; Yang, Ji-Won; Han, Jong-In; Im, Sung Gap; Kwon, Jong-Hee

    2016-01-13

    For the efficient separation of lipid extracted from microalgae cells, a novel membrane was devised by introducing a functional polymer coating onto a membrane surface by means of an initiated chemical vapor deposition (iCVD) process. To this end, a steel-use-stainless (SUS) membrane was modified in a way that its surface energy was systemically modified. The surface modification by conformal coating of functional polymer film allowed for selective separation of oil-water mixture, by harnessing the tuned interfacial energy between each liquid phase and the membrane surface. The surface-modified membrane, when used with chloroform-based solvent, exhibited superb permeate flux, breakthrough pressure, and also separation yield: it allowed separation of 95.5 ± 1.2% of converted lipid (FAME) in the chloroform phase from the water/MeOH phase with microalgal debris. This result clearly supported that the membrane-based lipid separation is indeed facilitated by way of membrane being functionalized, enabling us to simplify the whole downstream process of microalgae-derived biodiesel production.

  15. Development of a virus concentration method using lanthanum-based chemical flocculation coupled with modified membrane filtration procedures.

    PubMed

    Zhang, Yanyan; Riley, Lela K; Lin, Mengshi; Purdy, Gregory A; Hu, Zhiqiang

    2013-06-01

    Direct membrane filtration is often used to concentrate viruses in water but it may suffer from severe membrane fouling and clogging. Here, a lanthanum-based flocculation method coupled with modified membrane filtration procedures was developed and evaluated to detect viruses in large volume (40 L) water samples. The lanthanum-based flocculation method could easily reduce the water sample volume by a factor of 40. Additional volume reduction was achieved by a two-step membrane filtration approach. First, selected membrane filters (including 1MDS electropositive filters and nitrocellulose electronegative filters-Millipore HATF filters) were used to reduce water sample volume further and compare their efficiencies in virus recovery. The Mg²⁺-modified HATF membrane performed better on MS2 retention with an average virus recovery of 83.4% (±4.5% [standard deviation]). After HATF membrane filtration and elution, centrifugal ultrafiltration through a 30 kDa cut-off membrane resulted in an overall concentration factor of 20,000. Results from the infectivity assay showed that the MS2 recovery efficiencies from the NanoCeram- and 1MDS-based direct filtration and the lanthanum-based concentration coupled with the modified filtration procedure were 10.1% (±1.0%), 3.3% (±0.1%), and 17.5% (±1.1%), respectively. Results from the PCR analysis showed that the virus recoveries of the lanthanum-based method were 20.6% (±2.9%) and 19.5% (±3.4%) for MS2 and adenovirus, respectively, while no adenovirus could be detected through the NanoCeram- and 1MDS-based direct filtration. The lanthanum-based concentration method coupled with modified membrane filtration procedures is therefore a promising method for detecting waterborne viruses.

  16. Improved manufacturing technology for producing porous Nafion for high-performance ionic polymer-metal composite actuators

    NASA Astrophysics Data System (ADS)

    Zhao, Dongxu; Li, Dichen; Wang, Yanjie; Chen, Hualing

    2016-07-01

    The current actuation performance of ionic polymer-metal composites (IPMCs) limits their further application in the aerospace, energy, and optics fields, among others. To overcome this issue, we developed a freeze-drying process to generate Nafion membranes with a porous structure, the characteristics of which were investigated using thermogravimetric analysis, Fourier transform infrared spectrometry, field-emission scanning electron microscopy, and water uptake tests. The pores fabricated using the developed freeze-drying process had a diameter of approximately 270 nm, and a porosity of nearly 40.45%. The displacement and the central angle were introduced as variables to evaluate the bending deformation of an IPMC actuator based on the porous Nafion membrane. Compared with conventional actuators, this IPMC actuator showed an increase in displacement of 4963.6% at 2 V, and an increase in central angle of 73.35% at 3 V. Although the blocking forces of this IPMC actuator decreased to some extent, it was confirmed that the integrated actuation performance, which was evaluated using the strain energy density increment, was improved. The performance of the IPMC actuator was enhanced as a result of the porous Nafion structure manufactured using the developed freeze-drying process.

  17. Composites of ionic liquid and amine-modified SAPO 34 improve CO2 separation of CO2-selective polymer membranes

    NASA Astrophysics Data System (ADS)

    Hu, Leiqing; Cheng, Jun; Li, Yannan; Liu, Jianzhong; Zhang, Li; Zhou, Junhu; Cen, Kefa

    2017-07-01

    Mixed matrix membranes with ionic liquids and molecular sieve particles had high CO2 permeabilities, but CO2 separation from small gas molecules such as H2 was dissatisfied because of bad interfacial interaction between ionic liquid and molecular sieve particles. To solve that, amine groups were introduced to modify surface of molecular sieve particles before loading with ionic liquid. SAPO 34 was adopted as the original filler, and four mixed matrix membranes with different fillers were prepared on the outer surface of ceramic hollow fibers. Both surface voids and hard agglomerations disappeared, and the surface became smooth after SAPO 34 was modified by amine groups and ionic liquid [P66614][2-Op]. Mixed matrix membranes with composites of amine-modified SAPO 34 and ionic liquid exhibited excellent CO2 permeability (408.9 Barrers) and CO2/H2 selectivity (22.1).

  18. Controlled actuation of Nafion-based ionic polymer-metal composites (IPMCs)with ethylene glycol as solvent

    NASA Astrophysics Data System (ADS)

    Zamani, Shahram; Nemat-Nasser, Sia

    2004-07-01

    Ionic polymer-metal composites (IPMCs) consist of a perfluorinated ionomer membrane (usually Nafion or Flemion). The ionomer is plated on both faces with a noble metal such as gold or platinum. It is neutralized with a certain amount of counterions that balance the electrical charge of anions covalently fixed to the backbone membrane. IPMCs are electroactive materials that can be used as actuators and sensors. Their electrical-chemical-mechanical response is highly dependent on the cations used, the nature and the amount of solvent uptake, the morphology of the electrodes, and other factors. When a cantilever strip of solvated Nafion-based IPMC sample is subjected to a suddenly applied and sustained (DC) electric potential of several volts (1-3 V) across its faces, it bends towards the anode. For Nafion-based IPMCs with alkali metals, actuation towards the anode is followed by a slow back relaxation towards the cathode. If the electric potential is removed and the two electrodes are shorted during this back relaxation, the sample displays a fast bending deformation towards the cathode and then slowly relaxes back towards the anode, attaining a new equilibrium position generally distinct from its initial state. One way to change various phases of IPMC actuation is achieved by changing input potential. The electric potential inputs may be used to control the actuation of IPMCs. We present the results of a series of tests on Nafion-based IPMCs with ethylene glycol as solvent, actuated under electric potential inputs other than DC electric potential. We present experimental results for increasing ramp and sinusoidal electric potential waveforms.

  19. FACTORS WHICH MODIFY THE EFFECT OF SODIUM AND POTASSIUM ON BACTERIAL CELL MEMBRANES.

    PubMed

    HENNEMAN, D H; UMBREIT, W W

    1964-06-01

    Henneman, Dorothy H. (Rutgers, The State University, New Brunswick, N.J.), and W. W. Umbreit. Factors which modify the effect of sodium and potassium on bacterial cell membranes. J. Bacteriol. 87:1266-1273. 1964.-Suspensions of Escherichia coli B, when placed in 0.2 to 0.5 m solutions of NaCl, KCl, or LiCl, show an increased turbidity. With NaCl, this increased turbidity is stable with time; with KCl and LiCl, it is gradually lost. The stability to NaCl with time is due to substances removable from the cell by incubation in phosphate buffer; these materials exist in water washings from such phosphate-incubated cells.

  20. A Three-Scale Model of Basic Mechanical Properties of Nafion

    NASA Astrophysics Data System (ADS)

    Kafka, V.; Vokoun, D.

    2015-01-01

    The mechanical properties of Nafion are explained and modeled on the basis of Kafka's general mesomechanical model and confronted with experimental results. In this approach, Nafion is looked upon as a composite consisting of three constituents: a crystalline Nafion, amorphous Nafion, and water. Taking into account the degree of hydration, its elastic, elastic-plastic, and hysteretic properties are discussed and modeled. It is shown how the interaction between the three constituents manifests itself on the macroscale.

  1. An oxalate selective electrode based on modified PVC-membrane with tetra-butylammonium--Clinoptilolite nanoparticles.

    PubMed

    Hoseini, Zohre; Nezamzadeh-Ejhieh, Alireza

    2016-03-01

    A modified PVC-membrane electrode with tetra-butylammonium bromide - Clinoptilolite nano-particles (TBA-NCP) showed good Nernstian slope (29.9±0.6 mV per decade of oxalate concentration) in concentration range of 3.1×10(-7)-8.3×10(-1) mol L(-1) with a detection limit of 1.5×10(-7) mol L(-1). The best performance was obtained with a membrane composition of 31.5% PVC, 62.5% DOP and 6% TBA-NCP in the temperature range of 20-35 °C and the pH range of 4-9. The fast response time and good reproducibility over a period of 3 months are other characteristics of the sensor. The proposed electrode was successfully used as an indicator electrode in titration of oxalate ions with CaCl2 solution. The proposed electrode was also used in direct potentiometric determination of oxalate in many real samples such as: mushroom, black and green tea, spinach and beet. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. Assessing and simulation of membrane technology for modifying starchy wastewater treatment

    NASA Astrophysics Data System (ADS)

    Hedayati Moghaddam, Amin; Hazrati, Hossein; Sargolzaei, Javad; Shayegan, Jalal

    2016-11-01

    In this study, a hydrophilic polyethersulfone membrane was used to modify the expensive and low efficient conventional treatment method of wheat starch production that would result in a cleaner starch production process. To achieve a cleaner production, the efficiency of starch production was enhanced and the organic loading rate of wastewater that was discharged into treatment system was decreased, simultaneously. To investigate the membrane performance, the dependency of rejection factor and permeate flux on operative parameters such as temperature, flow rate, concentration, and pH of feed were studied. Response surface methodology (RSM) has been applied to arrange the experimental layout which reduced the number of experiments and also the interactions between the parameters were considered. The maximum achieved rejection factor and permeate flux were 97.5% and 2.42 L min-1 m-2, respectively. Furthermore, a fuzzy inference system was selected to model the non-linear relations between input and output variable which cannot easily explained by physical models. The best agreement between the experimental and predicted data for permeate flux was denoted by correlation coefficient index (R 2) of 0.9752 and mean square error (MSE) of 0.0072 where defuzzification operator was center of rotation (centroid). Similarly, the maximum R 2 for rejection factor was 0.9711 where the defuzzification operator was mean of maxima (mom).

  3. Separation and preconcentration of cadmium ions using octadecyl silica membrane disks modified by methyltrioctylammonium chloride.

    PubMed

    Haji Shabani, Ali Mohammad; Dadfarnia, Shayesteh; Motavaselian, Fatemeh; Ahmadi, Seyyed Hamid

    2009-02-15

    A simple and selective method for the determination of cadmium in water samples by FAAS after solid phase extraction has been developed. The method is based on the sorption of cadmium as CdI(4)(2-) on octadecyl silica membrane disks modified by cationic surfactant of methyltrioctylammonium chloride in the pH range of 1-8. The sorbed cadmium is then eluted with 10ml of 1moll(-1) nitric acid in ethanol and is measured by flame atomic absorption spectrometry. The influence of flow rates of eluent and sample solution, iodide concentration and amount of surfactant in retention and elution of cadmium from disks was also investigated. A preconcentration factor of 100 was achieved by passing 1000ml of sample through the membrane disk. The limit of detection (LOD) of cadmium was found to be 0.014ngml(-1). Precision at 2.5mugl(-1) was 1.2% (n=8). The method was successfully applied to the determination of cadmium in some natural water samples. The accuracy was assessed through recovery experiment, independent analysis by graphite furnace atomic absorption spectrometry, and analysis of certified reference waters.

  4. Surface modification of a proton exchange membrane and hydrogen storage in a metal hydride for fuel cells

    NASA Astrophysics Data System (ADS)

    Andrews, Lisa

    Interest in fuel cell technology is rising as a result of the need for more affordable and available fuel sources. Proton exchange membrane fuel cells involve the catalysis of a fuel to release protons and electrons. It requires the use of a polymer electrolyte membrane to transfer protons through the cell, while the electrons pass through an external circuit, producing electricity. The surface modification of the polymer, NafionRTM, commonly researched as a proton exchange membrane, may improve efficiency of a fuel cell. Surface modification can change the chemistry of the surface of a polymer while maintaining bulk properties. Plasma modification techniques such as microwave discharge of an argon and oxygen gas mixture as well as vacuum-ultraviolet (VUV) photolysis may cause favorable chemical and physical changes on the surface of Nafion for improved fuel cell function. A possible increase in hydrophilicity as a result of microwave discharge experiments may increase proton conductivity. Grafting of acrylic acid from the surface of modified Nafion may decrease the permeation of methanol in a direct methanol fuel cell, a process which can decrease efficiency. Modification of the surface of Nafion samples were carried out using: 1) An indirect Ar/O2 gas mixture plasma investigating the reaction of oxygen radicals with the surface, 2) A direct Ar/O2 gas mixture plasma investigating the reaction of oxygen radicals and VUV radiation with the surface and, 3) VUV photolysis investigating exclusively the interaction of VUV radiation with the surface and any possible oxidation upon exposure to air. Acrylic acid was grafted from the VUV photolysed Nafion samples. All treated surfaces were analyzed using X-ray photoelectron spectroscopy (XPS). Fourier transform infrared spectroscopy (FTIR) was used to analyze the grafted Nafion samples. Scanning electron microscopy (SEM) and contact angle measurements were used to analyze experiments 2 and 3. Using hydrogen as fuel is a

  5. Catalyst for the oxidation of sulfur-containing compounds based on a polyamide membrane modified with cobalt phthalocyanine

    NASA Astrophysics Data System (ADS)

    Ziyadova, T. M.; Burmistrov, V. A.; Maizlish, V. E.; Koifman, O. I.

    2017-03-01

    The catalytic activity of phthalocyanine metal complex immobilized on the surface of a porous polyamide membrane is studied in the oxidation reaction of n-propyl mercaptan. Since noncatalytic oxidation is possible in the presence of oxygen, the kinetics of n-propyl mercaptan oxidation is analyzed as its aqueous alkaline solution passes through unmodified membranes. Characteristics of the catalyst's performance are selected to evaluate the efficiency of the catalytic process. It is shown that the modified membranes with pore diameters of 1 and 2 μm are the most effective catalysts.

  6. Plasma Membranes Modified by Plasma Treatment or Deposition as Solid Electrolytes for Potential Application in Solid Alkaline Fuel Cells

    PubMed Central

    Reinholdt, Marc; Ilie, Alina; Roualdès, Stéphanie; Frugier, Jérémy; Schieda, Mauricio; Coutanceau, Christophe; Martemianov, Serguei; Flaud, Valérie; Beche, Eric; Durand, Jean

    2012-01-01

    In the highly competitive market of fuel cells, solid alkaline fuel cells using liquid fuel (such as cheap, non-toxic and non-valorized glycerol) and not requiring noble metal as catalyst seem quite promising. One of the main hurdles for emergence of such a technology is the development of a hydroxide-conducting membrane characterized by both high conductivity and low fuel permeability. Plasma treatments can enable to positively tune the main fuel cell membrane requirements. In this work, commercial ADP-Morgane® fluorinated polymer membranes and a new brand of cross-linked poly(aryl-ether) polymer membranes, named AMELI-32®, both containing quaternary ammonium functionalities, have been modified by argon plasma treatment or triallylamine-based plasma deposit. Under the concomitant etching/cross-linking/oxidation effects inherent to the plasma modification, transport properties (ionic exchange capacity, water uptake, ionic conductivity and fuel retention) of membranes have been improved. Consequently, using plasma modified ADP-Morgane® membrane as electrolyte in a solid alkaline fuel cell operating with glycerol as fuel has allowed increasing the maximum power density by a factor 3 when compared to the untreated membrane. PMID:24958295

  7. Plasma membranes modified by plasma treatment or deposition as solid electrolytes for potential application in solid alkaline fuel cells.

    PubMed

    Reinholdt, Marc; Ilie, Alina; Roualdès, Stéphanie; Frugier, Jérémy; Schieda, Mauricio; Coutanceau, Christophe; Martemianov, Serguei; Flaud, Valérie; Beche, Eric; Durand, Jean

    2012-07-30

    In the highly competitive market of fuel cells, solid alkaline fuel cells using liquid fuel (such as cheap, non-toxic and non-valorized glycerol) and not requiring noble metal as catalyst seem quite promising. One of the main hurdles for emergence of such a technology is the development of a hydroxide-conducting membrane characterized by both high conductivity and low fuel permeability. Plasma treatments can enable to positively tune the main fuel cell membrane requirements. In this work, commercial ADP-Morgane® fluorinated polymer membranes and a new brand of cross-linked poly(aryl-ether) polymer membranes, named AMELI-32®, both containing quaternary ammonium functionalities, have been modified by argon plasma treatment or triallylamine-based plasma deposit. Under the concomitant etching/cross-linking/oxidation effects inherent to the plasma modification, transport properties (ionic exchange capacity, water uptake, ionic conductivity and fuel retention) of membranes have been improved. Consequently, using plasma modified ADP-Morgane® membrane as electrolyte in a solid alkaline fuel cell operating with glycerol as fuel has allowed increasing the maximum power density by a factor 3 when compared to the untreated membrane.

  8. New process for alleviation of membrane fouling of modified hybrid MBR system for advanced domestic wastewater treatment.

    PubMed

    Shuo, Liu; Baozhen, Wang; Hongjun, Han; Yanping, Liu

    2008-01-01

    A pilot-scale hybrid membrane bioreactor using a submerged flat panel membrane was designed and applied for advanced treatment of domestic wastewater. The new process adapted to the hybrid membrane bioreactor exhibits substantial decrease in membrane fouling and much easier cleaning. In this study, the new process configurations including the addition of anoxic/anaerobic zones, the package of synthetic fibrous fabric carrier for biofilm attached growth, activated sludge recycling and modified dosage of polished diatomite with high activity and multi-functions were investigated to select the optimal operational parameters for the hybrid membrane bioreactor system. The carrier package in the aerobic zone contributed 3.65 g/L (maximum) of fixed biomass to the system, thus reducing the suspended biomass, and has decreased the membrane cleaning cycle remarkably. The operation performance at the sludge recycle rate 0, 100%, 200% and 300% showed that, the trans-membrane pressure of flat panel membrane declined sharply with the increase of sludge recycling rate within a certain range, and 200% was decided to be optimal for in the membrane bioreactor system. EPS concentration in each sludge recycling rate was 135 mg/L, 92 mg/L, 68 mg/L and 55 mg/L respectively. The addition of anoxic and anaerobic zones degraded some large molecular organic compounds, which facilitated the biodegradation and removal of organic substances in aerobic zone. The modified dosage of polished diatomite has played a major important role for both preventing of membrane from fouling and its much easier cleaning when it formed. Copyright (c) IWA Publishing 2008.

  9. Sulfonated poly(tetramethydiphenyl ether ether ketone) membranes for vanadium redox flow battery application

    NASA Astrophysics Data System (ADS)

    Mai, Zhensheng; Zhang, Huamin; Li, Xianfeng; Bi, Cheng; Dai, Hua

    Sulfonated poly(tetramethydiphenyl ether ether ketone) (SPEEK) with various degree of sulfonation is prepared and first used as ion exchange membrane for vanadium redox flow battery (VRB) application. The vanadium ion permeability of SPEEK40 membrane is one order of magnitude lower than that of Nafion 115 membrane. The low cost SPEEK membranes exhibit a better performance than Nafion at the same operating condition. VRB single cells with SPEEK membranes show very high energy efficiency (>84%), comparable to that of the Nafion, but at much higher columbic efficiency (>97%). In the self-discharge test, the duration of the cell with the SPEEK membrane is two times longer than that with Nafion 115. The membrane keeps a stable performance after 80-cycles charge-discharge test.

  10. QAC modified PVDF membranes: Antibiofouling performance, mechanisms, and effects on microbial communities in an MBR treating municipal wastewater.

    PubMed

    Chen, Mei; Zhang, Xingran; Wang, Zhiwei; Wang, Liang; Wu, Zhichao

    2017-09-01

    Biofouling remains as a critical issue limiting the widespread applications of membrane bioreactors (MBRs). The use of antibiofouling membranes is an emerging method to tackle this issue. In this study, a polyvinylidene fluoride (PVDF) membrane was modified using a quaternary ammonium compound (QAC) to create an antibiofouling membrane. The membrane was used in an MBR and the performance, mechanisms, and effects on microbial communities of this membrane were compared to a control operated in parallel. Results showed that the membrane exhibited a significantly reduced transmembrane pressure increase rate of 0.29 kPa/d compared with 0.91 kPa/d of the control. Analysis using a confocal laser scanning microscope (CLSM) revealed almost complete lack of living microbes on the antibiofouling membrane in contrast to the control. However, specific oxygen uptake rate and dehydrogenase activity analyses demonstrated no adverse impacts on microbial viability of the bulk activated sludge. Bacterial population analysis using the Illumina Miseq platform added further evidence that the use of antibiofouling membrane did not exert negative influences on richness, diversity and structure of the bacterial community. Effluent quality of the test MBR also exhibited minimal difference from that of the control reactor. The amount of polysaccharides and proteins in the biofouling layer was also significantly reduced. Quartz crystal microbalance with dissipation monitoring suggested that the antibiofouling membrane only allowed organic matter with strong adhesion properties to attach onto the membrane surfaces. These findings highlight the potential of the antibiofouling membrane to be used in MBRs for wastewater treatment and reclamation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Measurement of apparent diffusion coefficients within ultrathin nafion Langmuir-Schaefer films: comparison of a novel scanning electrochemical microscopy approach with cyclic voltammetry.

    PubMed

    Bertoncello, Paolo; Ciani, Ilenia; Li, Fei; Unwin, Patrick R

    2006-12-05

    The use of scanning electrochemical microscopy (SECM) to evaluate the apparent diffusion coefficient, Dapp, of redox-active species in ultrathin Nafion films is described. In this technique, an ultramicroelectrode (UME) tip, positioned close to a film on a macroscopic electrode, is used to oxidize (or reduce) a species in bulk solution, causing the tip-generated oxidant (reductant) to diffuse to the film/solution interface. The oxidation (reduction) of film-confined species regenerates the reductant (oxidant) in solution, leading to feedback to the UME. A numerical model is developed that allows Dapp to be determined. For these studies, ultrathin films of Nafion were prepared using the Langmuir-Schaefer (LS) technique and loaded with an electroactive species, either the ferrocene derivative ferrocenyltrimethylammonium cation, FA+, or tris(2,2'-bipyridyl)ruthenium(II), Ru(bpy)32+. The morphology and the thickness of the Nafion LS films (1.5 +/- 0.2 nm per layer deposited) were evaluated using atomic force microscopy (AFM). For comparison with the SECM measurements, cyclic voltammetry (CV) was employed to evaluate the concentration of electroactive species within the Nafion LS films and to determine Dapp. The latter was found to be essentially invariant with film thickness, but the value for Ru(bpy)32+ was 1 order of magnitude larger than for FA+. CV and SECM measurements yield different values of Dapp, and the underlying reasons are discussed. In general, the Dapp values for these films are considerably smaller than for recast Nafion films, which can be attributed to the compactness of Nafion LS films. Nonetheless, the ultrathin nature of the films leads to fast response times, and we thus expect that these modified electrodes could find applications in sensing, electroanalysis, and electrocatalysis.

  12. Effects of surface roughening of Nafion 117 on the mechanical and physicochemical properties of ionic polymer-metal composite (IPMC) actuators

    NASA Astrophysics Data System (ADS)

    Wang, Yanjie; Zhu, Zicai; Liu, Jiayu; Chang, Longfei; Chen, Hualing

    2016-08-01

    In this paper, the surface of a Nafion membrane was roughened by the sandblasting method, mainly considering the change of sandblasting time and powder size. The roughened surfaces were characterized in terms of their topography from the confocal laser scanning microscope (CLSM) and SEM. The key surface parameters, such as Sa (the arithmetical mean deviation of the specified surface profile), SSA (the surface area ratio before and after roughening) and the area measurement on the histogram from the CLSM images, were extracted and evaluated from the roughened membranes. Also, the detailed change in surface and interfacial electrodes were measured and discussed together with the surface resistance, equivalent modulus, capacitance and performances of IPMC actuators based on the roughened membranes. The results show that a suitable sandblasting condition, resulting in the decrease in the bending stiffness and the increase in the interface area closely related to the capacitance, can effectively increase the electromechanical responses of IPMCs. Although the surface roughening by sandblasting caused a considerable lowering of mechanical strength, it was very effective for enlarging the interfacial area between Nafion membrane and the electrode layers, and for forming a penetrated electrode structure, which facilitated improvement of the surface resistance and capacitance characteristics of IPMCs. In this work, a quantitative relationship was built between the topography of Nafion membrane surface and electromechanical performance of IPMCs by means of sandblasting.

  13. Improved oxygen reduction reaction catalyzed by Pt/Clay/Nafion nanocomposite for PEM fuel cells.

    PubMed

    Narayanamoorthy, B; Datta, K K R; Eswaramoorthy, M; Balaji, S

    2012-07-25

    A novel Pt nanoparticle (Pt NP) embedded aminoclay/Nafion (Pt/AC/N) nanocomposite catalyst film was prepared for oxygen reduction reaction by sol-gel method. The prepared nanocomposite films were surface characterized using XRD and TEM and thermal stability was studied by TGA. The prepared film has firmly bound Pt NP and could exhibit an improved electro-reduction activity compared to vulcan carbon/Nafion supported Pt NP (Pt/VC/N). Moreover, the Pt/AC/N film possessed good stability in the acidic environment. The limiting current density of the Pt/AC/N film with 35.4 μg/cm(2) of Pt loading was found to be 4.2 mA/cm(2), which is 30% higher than that of the Pt/VC/N. The maximum H2O2 intermediate formation was found to be ∼1.6% and the reaction found to follow a four electron transfer mechanism. Accelerated durability test for 2000 potential cycles showed that ca. 78% of initial limiting current was retained. The results are encouraging for possible use of the Pt/AC/N as the free-standing electrocatalyst layer for polymer electrolyte membrane fuel cells.

  14. An all-aqueous route to polymer brush-modified membranes with remarkable permeabilites and protein capture rates

    PubMed Central

    Anuraj, Nishotha; Bhattacharjee, Somnath; Geiger, James H.; Baker, Gregory L.; Bruening, Merlin L.

    2011-01-01

    Microporous membranes are attractive for protein purification because convection rapidly brings proteins to binding sites. However, the low binding capacity of such membranes limits their applications. This work reports a rapid, aqueous procedure to create highly permeable, polymer brush-modified membranes that bind large amounts of protein. The synthetic method includes a 10-min adsorption of a macroinitiator in a hydroxylated nylon membrane and a subsequent 5-min aqueous atom transfer radical polymerization of 2-(methacryloyloxy)ethyl succinate from the immobilized initiator to form poly(acid) brushes. This procedure likely leads to more swollen, less dense brushes than polymerization from silane initiators, and thus requires less polymer to achieve the same binding capacity. The hydraulic permeability of the poly(acid) membranes is 4-fold higher than that of similar membranes prepared by growing brushes from immobilized silane initiators. These brush-containing nylon membranes bind 120 mg/cm3 of lysozyme using solution residence times as short as 35 ms, and when functionalized with nitrilotriacetate (NTA)-Ni2+ complexes, they capture 85 mg/cm3 of histidine6-tagged (His-tagged) Ubiquitin. Additionally the NTA-Ni2+-functionalized membranes isolate His-tagged myo-inositol-1-phosphate synthase directly from cell extracts and show >90% recovery of His-tagged proteins. PMID:22287817

  15. The plasma membrane proteome of Medicago truncatula roots as modified by arbuscular mycorrhizal symbiosis.

    PubMed

    Aloui, Achref; Recorbet, Ghislaine; Lemaître-Guillier, Christelle; Mounier, Arnaud; Balliau, Thierry; Zivy, Michel; Wipf, Daniel; Dumas-Gaudot, Eliane

    2017-07-19

    In arbuscular mycorrhizal (AM) roots, the plasma membrane (PM) of the host plant is involved in all developmental stages of the symbiotic interaction, from initial recognition to intracellular accommodation of intra-radical hyphae and arbuscules. Although the role of the PM as the agent for cellular morphogenesis and nutrient exchange is especially accentuated in endosymbiosis, very little is known regarding the PM protein composition of mycorrhizal roots. To obtain a global overview at the proteome level of the host PM proteins as modified by symbiosis, we performed a comparative protein profiling of PM fractions from Medicago truncatula roots either inoculated or not with the AM fungus Rhizophagus irregularis. PM proteins were isolated from root microsomes using an optimized discontinuous sucrose gradient; their subsequent analysis by liquid chromatography followed by mass spectrometry (MS) identified 674 proteins. Cross-species sequence homology searches combined with MS-based quantification clearly confirmed enrichment in PM-associated proteins and depletion of major microsomal contaminants. Changes in protein amounts between the PM proteomes of mycorrhizal and non-mycorrhizal roots were monitored further by spectral counting. This workflow identified a set of 82 mycorrhiza-responsive proteins that provided insights into the plant PM response to mycorrhizal symbiosis. Among them, the association of one third of the mycorrhiza-responsive proteins with detergent-resistant membranes pointed at partitioning to PM microdomains. The PM-associated proteins responsive to mycorrhization also supported host plant control of sugar uptake to limit fungal colonization, and lipid turnover events in the PM fraction of symbiotic roots. Because of the depletion upon symbiosis of proteins mediating the replacement of phospholipids by phosphorus-free lipids in the plasmalemma, we propose a role of phosphate nutrition in the PM composition of mycorrhizal roots.

  16. High-Flux Positively Charged Nanocomposite Nanofiltration Membranes Filled with Poly(dopamine) Modified Multiwall Carbon Nanotubes.

    PubMed

    Zhao, Feng-Yang; Ji, Yan-Li; Weng, Xiao-Dan; Mi, Yi-Fang; Ye, Chun-Chun; An, Quan-Fu; Gao, Cong-Jie

    2016-03-01

    The poor dispensability of pristine carbon nanotubes in water impedes their implications in thin-film nanocomposite membranes for crucial utilities such as water purification. In this work, high-flux positively charged nanocomposite nanofiltration membranes were exploited by uniformly embedding poly(dopamine) modified multiwall carbon nanotubes (PDA-MWCNTs) in polyamide thin-film composite membranes. With poly(dopamine) modification, fine dispersion of MWCNTs in polyethyleneimine (PEI) aqueous solutions was achieved, which was interracially polymerized with trimesoyl chloride (TMC) n-hexane solutions to prepare nanocomposite membranes. The compatibility and interactions between modified MWCNTs and polyamide matrix were enhanced, attributed to the poly(dopamine) coatings on MWCNT surfaces, leading to significantly improved water permeability. At optimized conditions, pure water permeability of the PEI/PDA-MWCNTs/TMC nanofiltration membrane (M-4) was 15.32 L m(-2) h(-1) bar(-1), which was ∼1.6 times increased compared with that of pristine PEI/TMC membranes. Salt rejection of M-4 to different multivalent cations decreased in the sequence ZnCl2 (93.0%) > MgCl2 (91.5%) > CuCl2 (90.5%) ≈ CaCl2, which is well-suited for water softening and heavy metal ion removal.

  17. Using Indentation to Characterize Water Transport and Structure in Nafion Thin Films

    NASA Astrophysics Data System (ADS)

    Davis, Eric; Nadermann, Nichole; Page, Kirt; Stafford, Christopher; Chan, Edwin

    Perfluorinated ionomers, specifically Nafion, are the state-of-the-art polymer used in fuel cells. For this application, Nafion is utilized in both a bulk (hundreds of microns) and confined (tens of nanometers) state. For Nafion thin films in a confined state, i.e., Nafion as thin film coatings on catalyst particles, in-plane transport may play a critical role in the movement of water and protons through this catalysis layer. In this study, water transport was measured for a series of Nafion thin film thicknesses using poroelastic relaxation indentation (PRI). Unlike traditional through-thickness diffusion measurement techniques for thin polymer films (e.g., quartz crystal microbalance), PRI can be used to probe the in-plane water transport behavior. Relative to bulk Nafion, reduced in-plane water diffusion was observed in thin film Nafion, and below approximately 1 micron, water diffusivity and Nafion film thickness exhibited a logarithmic relationship. Equilibrium swelling measurements of water saturated Nafion thin films were used in conjunction with pore network theory to develop a picture of how the molecular-scale structure of Nafion changes with confinement to nanoscale film thicknesses. Using Indentation to Characterize Water Transport and Structure in Nafion Thin Films.

  18. Pyruvate modifies metabolic flux and nutrient sensing during extracorporeal membrane oxygenation in an immature swine model

    SciTech Connect

    Ledee, Dolena R.; Kajimoto, Masaki; O'Kelly-Priddy, Colleen M.; Olson, Aaron; Isern, Nancy G.; Robillard Frayne, Isabelle; Des Rosiers, Christine; Portman, Michael A.

    2015-07-01

    Extracorporeal membrane oxygenation (ECMO) provides mechanical circulatory support for infants and children with postoperative cardiopulmonary failure. Nutritional support is mandatory during ECMO, although specific actions for substrates on the heart have not been delineated. Prior work shows that enhancing pyruvate oxidation promotes successful weaning from ECMO. Accordingly, we closely examined the role of prolonged systemic pyruvate supplementation in modifying metabolic parameters during the unique conditions of ventricular unloading provided by ECMO. Twelve male mixed breed Yorkshire piglets (age 30-49 days) received systemic infusion of either normal saline (Group C) or pyruvate (Group P) during ECMO for 8 hours. Over the final hour piglets received [2-13C] pyruvate, and [13C6]-L-leucine, as an indicator for oxidation and protein synthesis. A significant increase in lactate and pyruvate concentrations occurred, along with an increase in the absolute concentration of all measured CAC intermediates. Group P showed greater anaplerotic flux through pyruvate carboxylation although pyruvate oxidation relative to citrate synthase flux was similar to Group C. The groups demonstrated similar leucine fractional contributions to acetyl-CoA and fractional protein synthesis rates. Pyruvate also promoted an increase in the phosphorylation state of several nutrient sensitive enzymes, such as AMPK and ACC, and promoted O-GlcNAcylation through the hexosamine biosynthetic pathway (HBP). In conclusion, prolonged pyruvate supplementation during ECMO modified anaplerotic pyruvate flux and elicited changes in important nutrient and energy sensitive pathways, while preserving protein synthesis. Therefore, the observed results support the further study of nutritional supplementation and its downstream effects on cardiac adaptation during ventricular unloading.

  19. Electrode films of porous agarose: The effects of physical structure on electron transport processes. [Impregnated with Nafion; immobilized electroactive species

    SciTech Connect

    Moran, K.D.

    1988-02-01

    Potential use of chemically modified electrodes in electrocatalysis has stimulated interest in creation and characterization of electrode films for reagent immobilization. We have created two highly porous electrocatalyst support matrices, with high rates of electron transport. Both are based on immobilization of reagents in agarose gel. In one case, Nafion was impregnated into agarose gel films. Diffusion of methyl viologen in Nafionagarose matrices are higher than in Nafion. In Nafion, the diffusion coefficient decreases with increasing methyl viologen concentration, while in Nafionagarose, the opposite dependence is observed. The faster rate of electron transport in Nafionagarose films is related to the heterogeneous structure and the coupling of the diffusion pathways. In the second application of agarose gels as an electrode coating material, agarose hydroxyl groups were activated in 1,1'carbonyldiimidazole and subsequently reacted with amine derivatives of electroactive mediators. Electron transport between the electroactive sites in the gel is very rapid (on the order of 10/sup -7/ cm/sup 2/s. Interpreting the data in light of the Dahms-Ruff description of electron transport shows that the rate of electron transport through both ferrocene and viologen derivatized gels is limited by the rate of electron self-exchange of the species. 22 figs., 15 tabs

  20. Development of an amperometric ethanol biosensor based on a multiwalled carbon nanotube-Nafion-alcohol dehydrogenase nanobiocomposite.

    PubMed

    Liaw, Hong-Wei; Chen, Jie-Ming; Tsai, Yu-Chen

    2006-08-01

    An amperometric biosensor for the determination of ethanol has been constructed. It comprises a multiwalled carbon nanotubes (MWNTs) conduit, a Nafion binder, and an alcohol dehydrogenase (ADH) function. The measurement of ethanol is based on the signal produced by beta-nicotinamide adenine dinucleotide (NADH), the product of the enzymatic reaction. The MWNTs are cylindrical with an outer diameter in the range 40-60 nm, an inner diameter in the range 2-5 nm, and a length of up to several micrometers. The homogeneity of the resulting nanobiocomposite film was characterized by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The performance of the MWNTs-Nafion-ADH nanobiocomposite modified glassy carbon electrode was examined using cyclic voltammetry and amperometry in presence of NADH and in the presence of ethanol. The electrocatalytic activity of MWNTs towards the oxidation of NADH has allowed an effective low-potential amperometric determination of ethanol. In the case of 6 mgmL(-1) ADH, the MWNTs-Nafion-ADH nanobiocomposite film displayed a sensitivity of 830 nAmM(-1), a linear range up to 0.1 mM, a detection limit of 3 microM, and a response time of about 4 s.

  1. Enhanced proton conductivity by the influence of modified montmorillonite on poly (vinyl alcohol) based blend composite membranes

    NASA Astrophysics Data System (ADS)

    Palani, P. Bahavan; Abidin, K. Sainul; Kannan, R.; Rajashabala, S.; Sivakumar, M.

    2016-05-01

    The highest proton conductivity value of 0.0802 Scm-1 is obtained at 6wt% of protonated MMT added to the PVA/PEG blends. The polymer blend composite membranes are prepared with varied concentration of Poly vinyl alcohol (PVA), Poly ethylene glycol (PEG) and Montmorillonite (MMT) by solution casting method. The Na+ MMT was modified (protonated) to H+ MMT with ion exchange process. The prepared membranes were characterized by using TGA, FTIR, XRD, Ion Exchange Capacity, Water/Methanol uptake, swelling ratio and proton conductivity. The significant improvements in the hydrolytic stability were observed. In addition, thermal stability of the composite membranes were improved and controlled by the addition of MMT. All the prepared membranes are shown appreciable values of proton conductivity at room temperature with 100% relative humidity.

  2. Enhanced proton conductivity by the influence of modified montmorillonite on poly (vinyl alcohol) based blend composite membranes

    SciTech Connect

    Palani, P. Bahavan Abidin, K. Sainul; Kannan, R.; Rajashabala, S.; Sivakumar, M.

    2016-05-23

    The highest proton conductivity value of 0.0802 Scm{sup −1} is obtained at 6 wt% of protonated MMT added to the PVA/PEG blends. The polymer blend composite membranes are prepared with varied concentration of Poly vinyl alcohol (PVA), Poly ethylene glycol (PEG) and Montmorillonite (MMT) by solution casting method. The Na{sup +} MMT was modified (protonated) to H{sup +} MMT with ion exchange process. The prepared membranes were characterized by using TGA, FTIR, XRD, Ion Exchange Capacity, Water/Methanol uptake, swelling ratio and proton conductivity. The significant improvements in the hydrolytic stability were observed. In addition, thermal stability of the composite membranes were improved and controlled by the addition of MMT. All the prepared membranes are shown appreciable values of proton conductivity at room temperature with 100% relative humidity.

  3. Enhancing performance of PEM fuel cells: Using the Au nanoplatelet/Nafion interface to enable CO oxidation under ambient conditions

    SciTech Connect

    Li, Hongfei; Pan, Cheng; Zhao, Sijia; Liu, Ping; Zhu, Yimei; Rafailovich, Miriam H.

    2016-04-16

    We developed a method for fabrication of Au nanoparticle platelets which can be coated onto the Nafion membranes of polymer electrolyte membrane (PEM) fuel cells simply by Langmuir–Blodgett (LB) trough lift off from the air water interface. By incorporating the coated membranes into fuel cells with one membrane electrode assembly (MEA) we enhanced the maximum power output by more than 50% when operated under ambient conditions. An enhancement of more than 200% was observed when 0.1% CO was incorporated into the H2 input gas stream and minimal enhancement was observed when the PEM fuel cell was operated with 100% O2 gas at the cathode, or when particles were deposited on the electrodes. Density function theory (DFT) calculations were carried out to understand the origin of improved output power. Au NPs with 3-atomic layer in height and 2 nm in size were constructed to model the experimentally synthesized Au NPs. Our results indicated that the Au NPs interacted synergistically with the SO3 groups, attached at end of Nafion side chains, to reduce the energy barrier for the oxidation of CO occurring at the perimeter of the Au NPs, from 1.292 eV to 0.518 eV, enabling the reaction to occur at T<300 K.

  4. Enhancing performance of PEM fuel cells: Using the Au nanoplatelet/Nafion interface to enable CO oxidation under ambient conditions

    DOE PAGES

    Li, Hongfei; Pan, Cheng; Zhao, Sijia; ...

    2016-04-16

    We developed a method for fabrication of Au nanoparticle platelets which can be coated onto the Nafion membranes of polymer electrolyte membrane (PEM) fuel cells simply by Langmuir–Blodgett (LB) trough lift off from the air water interface. By incorporating the coated membranes into fuel cells with one membrane electrode assembly (MEA) we enhanced the maximum power output by more than 50% when operated under ambient conditions. An enhancement of more than 200% was observed when 0.1% CO was incorporated into the H2 input gas stream and minimal enhancement was observed when the PEM fuel cell was operated with 100% O2more » gas at the cathode, or when particles were deposited on the electrodes. Density function theory (DFT) calculations were carried out to understand the origin of improved output power. Au NPs with 3-atomic layer in height and 2 nm in size were constructed to model the experimentally synthesized Au NPs. Our results indicated that the Au NPs interacted synergistically with the SO3 groups, attached at end of Nafion side chains, to reduce the energy barrier for the oxidation of CO occurring at the perimeter of the Au NPs, from 1.292 eV to 0.518 eV, enabling the reaction to occur at T<300 K.« less

  5. Enhancing performance of PEM fuel cells: Using the Au nanoplatelet/Nafion interface to enable CO oxidation under ambient conditions

    SciTech Connect

    Li, Hongfei; Pan, Cheng; Zhao, Sijia; Liu, Ping; Zhu, Yimei; Rafailovich, Miriam H.

    2016-04-16

    We developed a method for fabrication of Au nanoparticle platelets which can be coated onto the Nafion membranes of polymer electrolyte membrane (PEM) fuel cells simply by Langmuir–Blodgett (LB) trough lift off from the air water interface. By incorporating the coated membranes into fuel cells with one membrane electrode assembly (MEA) we enhanced the maximum power output by more than 50% when operated under ambient conditions. An enhancement of more than 200% was observed when 0.1% CO was incorporated into the H2 input gas stream and minimal enhancement was observed when the PEM fuel cell was operated with 100% O2 gas at the cathode, or when particles were deposited on the electrodes. Density function theory (DFT) calculations were carried out to understand the origin of improved output power. Au NPs with 3-atomic layer in height and 2 nm in size were constructed to model the experimentally synthesized Au NPs. Our results indicated that the Au NPs interacted synergistically with the SO3 groups, attached at end of Nafion side chains, to reduce the energy barrier for the oxidation of CO occurring at the perimeter of the Au NPs, from 1.292 eV to 0.518 eV, enabling the reaction to occur at T<300 K.

  6. Protection from hemolytic uremic syndrome by eyedrop vaccination with modified enterohemorrhagic E. coli outer membrane vesicles.

    PubMed

    Choi, Kyoung Sub; Kim, Sang-Hyun; Kim, Eun-Do; Lee, Sang-Ho; Han, Soo Jung; Yoon, Sangchul; Chang, Kyu-Tae; Seo, Kyoung Yul

    2014-01-01

    We investigated whether eyedrop vaccination using modified outer membrane vesicles (mOMVs) is effective for protecting against hemolytic uremic syndrome (HUS) caused by enterohemorrhagic E. coli (EHEC) O157:H7 infection. Modified OMVs and waaJ-mOMVs were prepared from cultures of MsbB- and Shiga toxin A subunit (STxA)-deficient EHEC O157:H7 bacteria with or without an additional waaJ mutation. BALB/c mice were immunized by eyedrop mOMVs, waaJ-mOMVs, and mOMVs plus polymyxin B (PMB). Mice were boosted at 2 weeks, and challenged peritoneally with wild-type OMVs (wtOMVs) at 4 weeks. As parameters for evaluation of the OMV-mediated immune protection, serum and mucosal immunoglobulins, body weight change and blood urea nitrogen (BUN)/Creatinin (Cr) were tested, as well as histopathology of renal tissue. In order to confirm the safety of mOMVs for eyedrop use, body weight and ocular histopathological changes were monitored in mice. Modified OMVs having penta-acylated lipid A moiety did not contain STxA subunit proteins but retained non-toxic Shiga toxin B (STxB) subunit. Removal of the polymeric O-antigen of O157 LPS was confirmed in waaJ-mOMVs. The mice group vaccinated with mOMVs elicited greater humoral and mucosal immune responses than did the waaJ-mOMVs and PBS-treated groups. Eyedrop vaccination of mOMVs plus PMB reduced the level of humoral and mucosal immune responses, suggesting that intact O157 LPS antigen can be a critical component for enhancing the immunogenicity of the mOMVs. After challenge, mice vaccinated with mOMVs were protected from a lethal dose of wtOMVs administered intraperitoneally, conversely mice in the PBS control group were not. Collectively, for the first time, EHEC O157-derived mOMV eyedrop vaccine was experimentally evaluated as an efficient and safe means of vaccine development against EHEC O157:H7 infection-associated HUS.

  7. Photochemically modified ATO NPs as conductive support of Pt electrocatalysts for proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Ostrovsky, Stella; Larsen, Mikkel Juul; Peled, Anna; Lellouche, Jean-Paul

    2015-06-01

    Antimony-doped tin oxide (ATO) nanoparticles (NPs) were covalently modified with a benzophenone-silicate photoreactive organic molecule to enable the UV-mediated photoreduction of Pt(IV) on the surface of the ATO NPs to give Pt(0) NPs. The successfully synthesized Pt/ATO nanocomposites (NCs) that were based on these novel hybrid photoreactive ATO NPs showed a much better Pt dispersion than Pt/ATO NCs prepared by traditional methods. The size of the Pt NPs was below 2.8 nm for all the NCs. The prepared NCs were studied with respect to their properties as durable and active electrocatalysts for proton exchange membrane fuel cells. They were subjected to fuel-cell-relevant electrochemical characterization by rotating disc electrode cyclic voltammetry. The electrochemically active surface area was found to be significantly lower for the novel NCs than for the standard Pt/C catalyst, while on the other hand, their specific electrocatalytic activity towards the oxygen reduction reaction (ORR) was found to exceed that of the reference Pt/C by several times. The ORR activity in terms of the mass of Pt was comparable to, or greater than, that of the Pt/C. The stability towards electrochemical ageing was greatly improved for Pt/ATO NCs relative to Pt/C.

  8. Iron porphyrin-modified PVDF membrane as a biomimetic material and its effectiveness on nitric oxide binding

    NASA Astrophysics Data System (ADS)

    Can, Faruk; Demirci, Osman Cahit; Dumoulin, Fabienne; Erhan, Elif; Arslan, Leyla Colakerol; Ergenekon, Pınar

    2017-10-01

    Nitric oxide (NO) is a reactive gas well-known as an air pollutant causing severe environmental problems. NO is also an important signaling molecule having a strong affinity towards heme proteins in the body. Taking this specialty as a model, a biomimetic membrane was developed by modification of the membrane surface with iron-porphyrin which depicts very similar structure to heme proteins. In this study, PVDF membrane was coated with synthesized (4-carboxyphenyl)-10,15,20-triphenyl-porphyrin iron(III) chloride (FeCTPP) to promote NO fixation on the surface. The coated membrane was characterized in terms of ATR-IR spectra, contact angle measurement, chemical composition, and morphological structure. Contact angle of original PVDF first decreased sharply after plasma treatment and surface polymerization steps but after incorporation of FeCTPP, the surface acquired its hydrophobicity again. NO binding capability of modified membrane surface was evaluated on the basis of X-ray Photoelectron. Upon exposure to NO gas, a chemical shift of Fe+3 and appearance of new N peak was observed due to the electron transfer from NO ligand to Fe ion with the attachment of nitrosyl group to FeCTPP. This modification brings the functionality to the membrane for being used in biological systems such as membrane bioreactor material in biological NO removal technology.

  9. A high content in lipid-modified peripheral proteins and integral receptor kinases features in the arabidopsis plasma membrane proteome.

    PubMed

    Marmagne, Anne; Ferro, Myriam; Meinnel, Thierry; Bruley, Christophe; Kuhn, Lauriane; Garin, Jérome; Barbier-Brygoo, Hélène; Ephritikhine, Geneviève

    2007-11-01

    The proteomics of plasma membrane has brought to date only scarce and partial information on the actual protein repertoire. In this work, the plant plasma membrane proteome of Arabidopsis thaliana was investigated. A highly purified plasma membrane fraction was washed by NaCl and Na2CO3 salts, and the insoluble fractions were further analyzed by nano-LC-MS/MS. With 446 proteins identified, we hereby describe the largest plasma membrane proteome diversity reported so far. Half of the proteins were predicted to display transmembrane domains and/or to be anchored to the membrane, validating a posteriori the pertinence of the approach. A fine analysis highlighted two main specific and novel features. First, the main functional category is represented by a majority of as yet unreported signaling proteins, including 11% receptor-like kinases. Second, 16% of the identified proteins are predicted to be lipid-modified, specifically involving double lipid linkage through N-terminal myristoylation, S-palmitoylation, C-terminal prenylation, or glycosylphosphatidylinositol anchors. Thus, our approach led for the first time to the identification of a large number of peripheral proteins as part of the plasma membrane and allowed the functionality of the plasma membrane in the cell context to be reconsidered.

  10. Determination of As in tobacco by using electrochemical hydride generation at a Nafion® solid polymer electrolyte cell hyphenated with atomic fluorescence spectrometry

    NASA Astrophysics Data System (ADS)

    Yang, Qinghua; Gan, Wuer; Deng, Yun; Sun, Huihui

    2011-11-01

    In the present work, a novel solid polymer electrolyte hydride generation (SPE-HG) cell was developed. The home-made SPE-HG cell, mainly composed of three components (Nafion®117 membrane for separating and H + exchanging, a soft graphite felt cathode and a Ti mesh modified by Ir anode), was employed for detecting As by coupling to atomic fluorescence spectrometry (AFS). The H + generated by electrolysis of pure water in anode chamber transferred to cathode chamber through SPE, and immediately reacted with As 3 + to generate AsH 3. The relative mechanisms and operation conditions for hydride generation of As were investigated in detail. The developed cell employed water as an alternative of acid anolyte, with virtues of low-cost, more than 6 months lifetime and environment friendly compared with the conventional cell. Under the optimized conditions, the limit of determination of As 3 + for sample blank solution was 0.12 μg L - 1 , the RSD was 2.9% for 10 consecutive measurements of 5 μg L - 1 As 3 + standard solution. The accuracy of the method was verified by the determination of As in the reference Tea (GBW07605) and the developed method was successfully applied to determine trace amounts of As in tobacco samples with recovery from 97% to 103%.

  11. Structural and transport properties of Nafion in hydrobromic-acid solutions

    SciTech Connect

    Kusoglu, A; Cho, KT; Prato, RA; Weber, AZ

    2013-12-01

    Proton-exchange membranes are key solid-state ion carriers in many relevant energy technologies including flow batteries, fuel cells, and solar-fuel generators. In many of these systems, the membranes are in contact with electrolyte solutions. In this paper, we focus on the impact of different HBr, a flow-battery and exemplary acid electrolyte, external concentrations on the conductivity of Nafion, a perfluorosulfonic acid membrane that is commonly used in many energy-related applications. The peak and then decrease in conductivity is correlated with measured changes in the water and HBr content within the membrane. In addition, small-angle x-ray scattering is used to probe the nanostructure to correlate how the interactions of the bromide ion with the fixed sulfonic-acid sites impact conductivity and hydrophilic domain distance. It is also shown that membrane pretreatment has a large impact on the underlying structure/function relationship. The obtained data and results are useful for delineation of optimal operating regimes for flow batteries and similar technologies as well as in understanding underlying structure/function relationships of ionomers in electrolyte solutions. (C) 2013 Elsevier B.V. All rights reserved.

  12. In situ synthesis of nanocomposite membranes: comprehensive improvement strategy for direct methanol fuel cells.

    PubMed

    Rao, Siyuan; Xiu, Ruijie; Si, Jiangju; Lu, Shanfu; Yang, Meng; Xiang, Yan

    2014-03-01

    In situ synthesis is a powerful approach to control nanoparticle formation and consequently confers extraordinary properties upon composite membranes relative to conventional doping methods. Herein, uniform nanoparticles of cesium hydrogen salts of phosphotungstic acid (CsPW) are controllably synthesized in situ in Nafion to form CsPW–Nafion nanocomposite membranes with both improved proton conductivity and methanol-crossover suppression. A 101.3% increase of maximum power density has been achieved relative to pristine Nafion in a direct methanol fuel cell (DMFC), indicating a potential pathway for large-scale fabrication of DMFC alternative membranes.

  13. Integration of RAFT polymerization and click chemistry to fabricate PAMPS modified macroporous polypropylene membrane for protein fouling mitigation.

    PubMed

    Wang, Yun; Wang, Li-Li; He, Xiao-Chun; Zhang, Zi-Jun; Yu, Hai-Yin; Gu, Jia-Shan

    2014-12-01

    A copper (I)-catalyzed azide-alkyne cycloaddition (CuAAC) grafting-to method was used to tether alkyne-terminated poly(2-acrylamido-2-methyl propane sulfonic acid) (alkyne-PAMPS) to the azide functionalized macroporous polypropylene membrane (MPPM-N3). Alkyne-PAMPS was synthesized by the reversible addition-fragmentation chain transfer polymerization (RAFT) of AMPS with an alkyne-terminated trithiocarbonate served as a chain transfer agent. The combination of RAFT polymerization with click chemistry to graft polymer to the surface of polypropylene membrane produced relatively high grafting density and controllable grafting chain length. The structure and composition of the modified and unmodified MPPM surfaces were analyzed by attenuated total reflection-Fourier transform infrared spectroscopy (ATR/FT-IR), X-ray photoelectron spectroscopy (XPS); field emission scanning electron microscopy (FE-SEM) was employed to observe the morphological changes on the membrane surface. The permeation performances were tested by the filtration of protein dispersion. The experimental results show that with the grafting degree going up, the relative flux reduction decreases, while the relative flux recovery ratio increases, and the protein fouling is obviously mitigated by tethering PAMPS to the membrane surface. The modified membranes can be potentially applied for fouling reduction during the filtration of proteins. Copyright © 2014 Elsevier Inc. All rights reserved.

  14. Visible-light driven photocatalytic activity of β-indium sulfide (In2S3) quantum dots embedded in Nafion matrix

    NASA Astrophysics Data System (ADS)

    Sumi, R.; Warrier, Anita R.; Vijayan, C.

    2014-03-01

    We report on the visible-light-driven photocatalytic activity of highly stable β-indium sulfide (In2S3) quantum dots embedded in Nafion matrix. β-indium sulfide (In2S3) quantum dots (6-10 nm) embedded in Nafion matrix with strong quantum confinement were synthesized by a simple chemical route. The UV-Vis absorption spectrum shows a large blue shift (˜1 eV) which can be controlled by the reaction temperature and time. Strong broadband photoluminescence is observed in the blue, green and red regions of the emission spectrum with variation in particle size and stoichiometry of the quantum dots. Photocatalytic activity measurements show that these hybrid membranes synthesized with equimolar precursors of In and S show paramount photocatalytic activity under visible-light irradiation, with the degradation of Rhodamine-6G dyes up to 95% within 90 min. The photocatalytic membranes are tested for reusable and stable operation.

  15. PPO/PEO modified hollow fiber membranes improved sensitivity of 3D cultured hepatocytes to drug toxicity via suppressing drug adsorption on membranes.

    PubMed

    Shen, Chong; Meng, Qin; He, Wenjuan; Wang, Qichen; Zhang, Guoliang

    2014-11-01

    The three dimensional (3D) cell culture in polymer-based micro system has become a useful tool for in vitro drug discovery. Among those polymers, polysulfone hollow fiber membrane (PSf HFM) is commonly used to create a microenvironment for cells. However, the target drug may adsorb on the polymeric surface, and this elicits negative impacts on cell exposure due to the reduced effective drug concentration in culture medium. In order to reduce the drug adsorption, PSf membrane were modified with hydrophilic Pluronic (PEO-b-PPO-b-PEO) copolymers, L121, P123 and F127 (PEO contents increase from 10%, 30% to 70%), by physical adsorption. As a result, the hydrophilicity of HFMs increased at an order of PSfF127>P123>L121 HFMs. The three modified membrane all showed significant resistance to adsorption of acid/neutral drugs. More importantly, the adsorption of base drugs were largely reduced to an average value of 11% on the L121 HFM. The improved resistance to drug adsorption could be attributed to the synergy of hydrophobic/neutrally charged PPO and hydrophilic PEO. The L121 HFM was further assessed by evaluating the drug hepatotoxicity in 3D culture of hepatocytes. The base drugs, clozapine and doxorubicin, showed more sensitive hepatotoxicity on hepatocytes in L121 HFM than in PSf HFM, while the acid drug, salicylic acid, showed the similar hepatotoxicity to hepatocytes in both HFMs. Our finding suggests that PSf HFM modified by PEO-b-PPO-b-PEO copolymers can efficiently resist the drug adsorption onto polymer membrane, and consequently improve the accuracy and sensitivity of in vitro hepatotoxic drug screening. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Biodegradation of a biochar-modified waterborne polyacrylate membrane coating for controlled-release fertilizer and its effects on soil bacterial community profiles.

    PubMed

    Zhou, Zijun; Du, Changwen; Li, Ting; Shen, Yazhen; Zeng, Yin; Du, Jie; Zhou, Jianmin

    2015-06-01

    Biochar-modified polyacrylate-like polymers are promising waterborne polymer-based membrane coatings for controlled-release fertilizers. However, the effect of these membrane polymers on paddy soil is unknown. A soil incubation experiment was conducted using Fourier transform infrared photoacoustic spectroscopy to monitor the changes in the polymer-coated membranes in paddy soil, and Biolog EcoPlates and polymerase chain reaction-denaturing gradient gel electrophoresis were used to detect the effects of the membranes on soil bacterial community profiles. Compared to unmodified membranes, the biodegradation rate of the biochar-modified membrane was slower, and the membrane was more intact, which improved and guaranteed the controlled release of nutrients. Compared to the soil without membranes, the biochar-modified membranes, as well as unmodified ones, showed no significant impacts on the composition diversity of soil dominant bacterial community. The activity and functional diversity of soil culturable microbial community during the early stage of incubation were reduced by biochar-modified membranes due to the release of small amount of soluble organic materials but were both recovered in the 12(th) month of the incubation period. Therefore, the biochar-modified waterborne polyacrylate was environmentally friendly, demonstrating its potential both in the development of coated controlled-release fertilizers and in the utilization of crop residue.

  17. Use of nafion as a solid polymer electrolyte for the electroreduction of tungsten (VI) fluoride

    SciTech Connect

    Bettelheim, A.; Raven, A.; Polak, M.; Ozer, D. )

    1992-01-01

    In this paper a new method is described in which WF{sub 6} is electroreduced in a solid-state cell configuration with a Nafion membrane serving as a solid polymer electrolyte. Cyclic voltammetry indicates a behavior similar to that of metallic tungsten for coatings obtained at dry conditions and similar to that of tungsten oxide species when water vapor is not totally expelled. Surface analysis using Auger electroscope and x-ray photoelectron spectroscopy shows that solid-state electro-reduction of WF{sub 6} in dry conditions yields coatings free of fluorine, which contain much less oxygen than electrodeposits obtained from aqueous solutions. However, due to possible oxidation and reduction reactions occurring before and during the surface-analysis process, it is not possible at this state to determine the exact content of metallic and oxide species in the deposits obtained by the present method.

  18. Preparation and Characterization of Thin-Film Composite Membrane with Nanowire-Modified Support for Forward Osmosis Process

    PubMed Central

    Low, Ze-Xian; Liu, Qi; Shamsaei, Ezzatollah; Zhang, Xiwang; Wang, Huanting

    2015-01-01

    Internal concentration polarization (ICP) in forward osmosis (FO) process is a characteristic problem for asymmetric thin-film composite (TFC) FO membrane which leads to lower water flux. To mitigate the ICP effect, modification of the substrates’ properties has been one of the most effective methods. A new polyethersulfone-based ultrafiltration membrane with increased surface porosity and high water flux was recently produced by incorporating Zn2GeO4 nanowires. The composite membrane was used as a substrate for the fabrication of TFC FO membrane, by coating a thin layer of polyamide on top of the substrate. The substrate and the nanowires were characterized by a range of techniques such as SEM, XRD, and contact angle goniometry. The water permeability and molecular weight cut-offs (MWCO) of the substrate; and the FO performance of the TFC membrane were also determined. The Zn2GeO4-modified membrane showed ~45% increase in water permeability and NaCl salt rejection of 80% under RO mode. In FO mode, the ratio of water flux to reverse solute flux was also improved. However, lower FO flux was obtained which could be due to ICP. The result shows that Zn2GO4 nanowire may be used as a modifier to the substrate to improve the quality of the polyamide layer on the substrate to improve the flux and selectivity, but not as effective in reducing ICP. This work demonstrates that the incorporation of nanomaterials to the membrane substrate may be an alternative approach to improve the formation of polyamide skin layer to achieve better FO performance. PMID:25803239

  19. Preparation and characterization of thin-film composite membrane with nanowire-modified support for forward osmosis process.

    PubMed

    Low, Ze-Xian; Liu, Qi; Shamsaei, Ezzatollah; Zhang, Xiwang; Wang, Huanting

    2015-03-20

    Internal concentration polarization (ICP) in forward osmosis (FO) process is a characteristic problem for asymmetric thin-film composite (TFC) FO membrane which leads to lower water flux. To mitigate the ICP effect, modification of the substrates' properties has been one of the most effective methods. A new polyethersulfone-based ultrafiltration membrane with increased surface porosity and high water flux was recently produced by incorporating Zn2GeO4 nanowires. The composite membrane was used as a substrate for the fabrication of TFC FO membrane, by coating a thin layer of polyamide on top of the substrate. The substrate and the nanowires were characterized by a range of techniques such as SEM, XRD, and contact angle goniometry. The water permeability and molecular weight cut-offs (MWCO) of the substrate; and the FO performance of the TFC membrane were also determined. The Zn2GeO4-modified membrane showed ~45% increase in water permeability and NaCl salt rejection of 80% under RO mode. In FO mode, the ratio of water flux to reverse solute flux was also improved. However, lower FO flux was obtained which could be due to ICP. The result shows that Zn2GO4 nanowire may be used as a modifier to the substrate to improve the quality of the polyamide layer on the substrate to improve the flux and selectivity, but not as effective in reducing ICP. This work demonstrates that the incorporation of nanomaterials to the membrane substrate may be an alternative approach to improve the formation of polyamide skin layer to achieve better FO performance.

  20. Investigation of polymer membranes modified by fullerenol for dehydration of organic mixtures

    NASA Astrophysics Data System (ADS)

    Dmitrenko, Mariia E.; Penkova, Anastasia V.; Kuzminova, Anna I.; Ermakov, Sergey S.; Roizard, Denis

    2017-07-01

    This study focuses on the development of novel dense and supported mixed-matrix membranes based on chitosan and poly(2,6-dimethyl-1,4-phenylenoxide) (PPO) with low-hydroxylated fullerenol C60(OH)12. These novel membranes containing nano-carbon particles were prepared to reach high membrane performances for further integration in a dehydration process like distillation coupled with pervaporation. SEM microscopy was used to visualize the internal morphology of the membrane. It was found that all membranes were well stable and highly water-selective in spite of the different nature of polymers.

  1. Preparation, characterization and performance of poly(m-phenylene isophthalamide)/organically modified montmorillonite nanocomposite membranes in removal of perfluorooctane sulfonate.

    PubMed

    Luo, Qin; Liu, Yanxia; Liu, Guixia; Zhao, Changwei

    2016-08-01

    Nanocomposite membranes containing poly(m-phenylene isophthalamide) (PMIA) and organically modified montmorillonite (OMMT) were prepared by a combination of solution dispersion and wet-phase inversion methods, and the effects of OMMT addition on the properties and performance of fabricated nanofiltration membranes were investigated. The membranes were characterized by contact angle measurements, scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis, and zeta potential. The performance of the membranes was elucidated by the removal of perfluorooctane sulfonate (PFOS) at neutral pH. Increasing OMMT concentration improved the thermal stability and hydrophilicity of the membranes. The permeation and rejection of PFOS were significantly improved. The performance of fabricated nanofiltration membranes in removal of PFOS varied depending on the solute and membrane properties as well as solution conditions. Finally, a comparison between fabricated membranes and a commercial NF membrane (ESNA1-K1, Hydecanme) proved that the OMMT addition is a convenient procedure for producing nanocomposite membranes with superior properties and performance.

  2. Electrodialysis heterogeneous ion exchange membranes modified by SiO2 nanoparticles: fabrication and electrochemical characterization.

    PubMed

    Hosseini, S M; Ahmadi, Z; Nemati, M; Parvizian, F; Madaeni, S S

    2016-01-01

    In the current study mixed matrix heterogeneous cation exchange membranes were prepared by solution casting technique. The effect of SiO(2) nanoparticles in the polymeric solution on the physicochemical properties of prepared membranes was studied. Scanning optical microscope images showed uniform particle distribution and relatively uniform surfaces for the prepared membranes. The membrane water content was reduced by silica nanoparticles in the membranes' matrix. The membrane ion exchange capacity, membrane potential, transport number and selectivity were improved initially by an increase of SiO(2) nanoparticles concentration up to 1%wt in prepared membranes and then showed a decreasing trend with a further increase in additive ratio from 1 to 4%wt. The ionic permeability and flux were also decreased initially by an increase of silica nanoparticles concentration up to 0.5%wt in the membrane matrix and then increased again with a further increase in nanoparticles concentration from 0.5 to 4%wt. Moreover, the results exhibited that using silica nanoparticles in the membrane matrix caused an obvious decrease in areal electrical resistance. The opposite trend was found for membrane mechanical strength using SiO(2) nanoparticles.

  3. Hierarchical Nafion enhanced carbon aerogels for sensing applications

    NASA Astrophysics Data System (ADS)

    Weng, Bo; Ding, Ailing; Liu, Yuqing; Diao, Jianglin; Razal, Joselito; Lau, King Tong; Shepherd, Roderick; Li, Changming; Chen, Jun

    2016-02-01

    This work describes the fabrication of hierarchical 3D Nafion enhanced carbon aerogels (NECAGs) for sensing applications via a fast freeze drying method. Graphene oxide, multiwalled carbon nanotubes and Nafion were mixed and extruded into liquid nitrogen followed by the removal of ice crystals by freeze drying. The addition of Nafion enhanced the mechanical strength of NECAGs and effective control of the cellular morphology and pore size was achieved. The resultant NECAGs demonstrated high strength, low density, and high specific surface area and can achieve a modulus of 20 kPa, an electrical conductivity of 140 S m-1, and a specific capacity of 136.8 F g-1 after reduction. Therefore, NECAG monoliths performed well as a gas sensor and as a biosensor with high sensitivity and selectivity. The remarkable sensitivity of 8.52 × 103 μA mM-1 cm-2 was obtained in dopamine (DA) detection, which is two orders of magnitude better than the literature reported values using graphene aerogel electrodes made from a porous Ni template. These outstanding properties make the NECAG a promising electrode candidate for a wide range of applications. Further in-depth investigations are being undertaken to probe the structure-property relationship of NECAG monoliths prepared under various conditions.This work describes the fabrication of hierarchical 3D Nafion enhanced carbon aerogels (NECAGs) for sensing applications via a fast freeze drying method. Graphene oxide, multiwalled carbon nanotubes and Nafion were mixed and extruded into liquid nitrogen followed by the removal of ice crystals by freeze drying. The addition of Nafion enhanced the mechanical strength of NECAGs and effective control of the cellular morphology and pore size was achieved. The resultant NECAGs demonstrated high strength, low density, and high specific surface area and can achieve a modulus of 20 kPa, an electrical conductivity of 140 S m-1, and a specific capacity of 136.8 F g-1 after reduction. Therefore, NECAG

  4. Constructing proton-conductive highways within an ionomer membrane by embedding sulfonated polymer brush modified graphene oxide

    NASA Astrophysics Data System (ADS)

    Zhao, Liping; Li, Yifan; Zhang, Haoqin; Wu, Wenjia; Liu, Jindun; Wang, Jingtao

    2015-07-01

    Sulfonated polymer brush modified graphene oxide (SP-GO) fillers with controllable brush length are synthesized via the facile distillation-precipitation polymerization, and then incorporated into sulfonated poly(ether ether ketone) (SPEEK) matrix to fabricate composite membranes. The influences of SP-GO upon the microstructures, including thermal and mechanical properties, water uptake/swelling, proton conduction, H2 permeability and single PEMFC performances of composite membranes are intensively investigated. It is found that the SP-GO fillers are uniformly dispersed and tend to lie perpendicularly to the cross-section surface of the whole membrane, which allow SP-GO fillers creating inter-connected and broad ionic pathways through the sulfonic acid groups in polymer brushes. Meanwhile, the SP-GO fillers connect the ionic clusters in SPEEK matrix via interfacial interactions. In such a way, proton-transfer highways are constructed along the SPEEK/SP-GO interface, which lower the proton transfer activation energy and enhance the proton conductivities of the composite membranes under both hydrated and anhydrous conditions. Furthermore, elevating the brush length on SP-GO could further enhance the proton conductivity. Compared to SPEEK control membrane, a 95.5% increase in hydrated conductivity, an 178% increase in anhydrous conductivity and a 37% increase in maximum power density are obtained for the optimal composite membrane.

  5. [Effect of extra-cellular polymeric substances on filtration of modified non-woven fabric in membrane bio-reactor].

    PubMed

    Zhang, Chun-hua; Yang, Feng-lin; Wang, Wen-jun; An, Xiao-wen; Zhang, Feng-jie

    2008-06-01

    The effect of extra-cellular polymeric substances (EPS) on filtration of polyvinyl alcohol modified polypropylene non-woven in submerged membrane bioreactor (SMBR) was investigated by statistical method. The results show that soluble extra-cellular polymeric substances (EPSs) of activated sludge on the non-woven modules surface, components (protein/carbohydrate, P/C) of EPSs and relative hydrophobicity (RH) have a significant influence on filtration performance of module B, the Pearson's correlation coefficient (r(p)) related to membrane fouling resistance are 0.868, 0.840, 0.890, respectively. Modified module can effectively restrict the adsorption of EPSs, can reduce the ratio of P/C in EPSs and can decrease the accumulation of activated sludge. After hydrophilic modification of non-woven, the filtration performance is improved obviously and the un-fouling performance is increased.

  6. Improvement of virus removal using ultrafiltration membranes modified with grafted zwitterionic polymer hydrogels.

    PubMed

    Lu, Ruiqing; Zhang, Chang; Piatkovsky, Maria; Ulbricht, Mathias; Herzberg, Moshe; Nguyen, Thanh H

    2017-06-01

    Potable water reuse has been adopted by cities suffering water scarcity in recent years. The microbial safety in water reuse, especially with respect to pathogenic viruses, is still a concern for water consumers. Membrane filtration can achieve sufficient removal of pathogenic viruses without disinfection byproducts, but the required energy is intensive. In this study, we graft-polymerized zwitterionic SPP ([3-(methacryloylamino) propyl] dimethyl (3-sulfopropyl) ammonium hydroxide) on a 150 kDa ultrafiltration polyethersulfone membrane to achieve a significantly higher virus removal. The redox-initiated graft-polymerization was performed in an aqueous solution during filtration of the monomer and initiators, allowing for functionalizing the membrane pores with hydrophilic polySPP. Bacteriophage MS2 and human adenovirus type 2 (HAdV-2) were used as surrogates for pathogenic human norovirus and human adenovirus. The grafting resulted in ∼18% loss of the membrane permeability but an increase of 4 log10 in HAdV-2 removal and 3 log10 in MS2 removal. The pristine and the grafted membranes were both conditioned with soluble microbial products (SMP) extracted from a full-scale membrane bioreactor (MBR) in order to test the virus removal after fouling the membranes. After fouling, the HAdV-2 removal by the grafted membrane was 1 log10 higher than that of the pristine membrane. For MS2, the grafted membrane after fouling with SMP achieved an additional 5 log10 removal compared to the unmodified membrane. The simple graft-polymerization functionalization of commercialized membrane achieving enhanced virus removal efficiency highlights the promise of membrane filtration for pathogen control in potable water reuse. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. X-ray degradation studies of Nafion in a PEM fuel cell

    NASA Astrophysics Data System (ADS)

    Jenkins, Rebecca; Fragoso, Juan

    2008-03-01

    The overall goal of this research is to test for degradation of the Polymer Electrolyte Membrane (PEM) fuel cells due to exposure to ionizing radiation. We have successfully developed a Membrane Electrode Assembly (MEA) that can be fully disassembled down to the bare Proton Exchange Membrane (PEM) and reassembled repeatedly. This is crucial for testing the degradation effects on the individual components of the MEA. It was also important to establish baseline repeatability of the polarization curves of the MEAs. Therefore, we systematically varied different parameters to test their effect as well as to establish consistent experimental procedures. Hydration of the fuel cell has been found to be crucial for repeatable results. These polarization curves showed voltages that ranged from 0.4V to 1.0V and current densities up to 11mA/cm2. The Nafion can then be exposed to an x-ray source and the respective polarization data can be studied. A working fuel cell has also been built that fits into the microwave cavity of an electron paramagnetic resonance spectrometer. This allows for study of in situ behavior of free radicals formed in a normal operational fuel cell as well as fuel cells with x-ray exposed membranes.

  8. Application of pervaporation and vapor permeation processes to separate aqueous ethanol solution through chemically modified Nylon 4 membranes

    SciTech Connect

    Wang, Y.H.; Teng, M.Y.; Lee, K.R.; Wang, D.M.; Lai, J.Y.

    1998-08-01

    The pervaporation performance of a Nylon 4 membrane, chemically grafted by N,N-dimethylaminoethyl methacrylate (DMAEM), DMAEM-g-N4, was studied by measurement of the permeation ratio and the pervaporation separation index. It was found that the water permselectivity and permeation rate for the chemically modified Nylon 4 membrane were higher than those of the unmodified Nylon 4 membrane. Optimum pervaporation results, a separation factor of 28.3, and a permeation rate of 439 g/m{sup 2}{center_dot}h, were obtained when the degree of grafting was 12.7%. It was also found that all the permeation ratios at low temperature were less than unity. In addition, compared with pervaporation, vapor permeation effectively increases the permselectivity of water.

  9. Surface Modified Biodegradable Electrospun Membranes as a Carrier for Human Embryonic Stem Cell-Derived Retinal Pigment Epithelial Cells.

    PubMed

    Sorkio, Anni; Porter, Patrick J; Juuti-Uusitalo, Kati; Meenan, Brian J; Skottman, Heli; Burke, George A

    2015-09-01

    Human embryonic stem cell-derived retinal pigment epithelial (hESC-RPE) cells are currently undergoing clinical trials to treat retinal degenerative diseases. Transplantation of hESC-RPE cells in conjuction with a supportive biomaterial carrier holds great potential as a future treatment for retinal degeneration. However, there has been no such biodegradable material that could support the growth and maturation of hESC-RPE cells so far. The primary aim of this work was to create a thin porous poly (L-lactide-co-caprolactone) (PLCL) membrane that could promote attachment, proliferation, and maturation of the hESC-RPE cells in serum-free culture conditions. The PLCL membranes were modified by atmospheric pressure plasma processing and coated with collagen IV to enhance cell growth and maturation. Permeability of the membranes was analyzed with an Ussing chamber system. Analysis with scanning electron microscopy, contact angle measurement, atomic force microscopy, and X-ray photoelectron spectroscopy demonstrated that plasma surface treatment augments the surface properties of the membrane, which enhances the binding and conformation of the protein. Cell proliferation assays, reverse transcription-polymerase chain reaction, indirect immunofluoresence staining, trans-epithelial electrical resistance measurements, and in vitro phagocytosis assay clearly demonstrated that the plasma treated PLCL membranes supported the adherence, proliferation, maturation and functionality of hESC-RPE cells in serum-free culture conditions. Here, we report for the first time, how PLCL membranes can be modified with atmospheric pressure plasma processing to enable the formation of a functional hESC-RPE monolayer on a porous biodegradable substrate, which have a potential as a tissue-engineered construct for regenerative retinal repair applications.

  10. Treatment of lead contaminated water by a PVDF membrane that is modified by zirconium, phosphate and PVA.

    PubMed

    Zhao, Dandan; Yu, Yang; Chen, J Paul

    2016-09-15

    Lead contamination is one of the most serious problems in drinking water facing humans. In this study, a novel zirconium phosphate modified polyvinyl alcohol (PVA)-PVDF membrane was developed for lead removal. The zirconium ions and PVA were firstly coated onto a PVDF membrane through crosslinking reactions with glutaraldehyde, which was then modified by phosphate. The adsorption kinetics study showed that most of ultimate uptake occurred in 5 h. The adsorption increased with an increase in pH; the optimal adsorption was achieved at pH 5.5. The experimental data were better described by Langmuir equation than Freundlich equation; the maximum adsorption capacity was 121.2 mg-Pb/g at pH 5.5, much higher than other reported adsorptive membranes. The membrane exhibited a higher selectivity for lead over zinc with a relative selectivity coefficient (Pb(2+)/Zn(2+)) of 9.92. The filtration study showed that the membrane with an area of 12.56 cm(2) could treat 13.9 L (equivalent to 73,000 bed volumes) of lead containing wastewater with an influent concentration of 224.5 μ g/L to meet the maximum contaminant level of 15 μ g/L. It was demonstrated that the membrane did well in the removal of lead in both simulated wastewater and lead-spiked reservoir water and had a good reusability in its applications. The XPS studies revealed that the lead uptake was mainly due to cation exchange between hydrogen ions and lead ions. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. To what end does nature produce superoxide? NADPH oxidase as an autocrine modifier of membrane phospholipids generating paracrine lipid messengers.

    PubMed

    Saran, Manfred

    2003-10-01

    Production of superoxide anion O2*- by the membrane-bound enzyme NADPH oxidase of phagocytes is a long-known phenomenon; it is generally assumed that O2*-helps phagocytes kill bacterial intruders. The details and the chemistry of the killing process have, however, remained a mystery. Isoforms of NADPH oxidase exist in membranes of nearly every cell, suggesting that reactive oxygen species (ROS) participate in intra- and intercellular signaling processes. What the nature of the signal is exactly, how it is transmitted, and what structural characteristics a receptor of a "radical message" must have, have not been addressed convincingly. This review discusses how the action of messengers is in agreement with radical-specific behavior. In search for the smallest common denominator of cellular free radical activity we hypothesize that O2*- and its conjugate acid, HO2*, may have evolved under primordial conditions as regulators of membrane mechanics and that isoprostanes, widely used markers of "oxidative stress", may be an adventitious correlate of this biologic activity of O2*-/HO2*. An overall picture is presented that suggests that O2*-/HO2* radicals, by modifying cell membranes, help other agents gain access to the hydrophobic region of phospholipid bilayers and hence contribute to lipid-dependent signaling cascades. With this, O2*-/HO2* are proposed as indispensable adjuvants for the generation of cellular signals, for membrane transport, channel gating and hence, in a global sense, for cell viability and growth. We also suggest that many of the allegedly O2*- dependent bacterial pathologies and carcinogenic derailments are due to membrane-modifying activity rather than other chemical reactions of O2*-/HO2*. A consequence of this picture is the potential evolution of the "radical theory of ageing" to a "lipid theory of aging".

  12. Iron-tannin-framework complex modified PES ultrafiltration membranes with enhanced filtration performance and fouling resistance.

    PubMed

    Fang, Xiaofeng; Li, Jiansheng; Li, Xin; Pan, Shunlong; Sun, Xiuyun; Shen, Jinyou; Han, Weiqing; Wang, Lianjun; Van der Bruggen, Bart

    2017-11-01

    In this work, an iron-tannin-framework (ITF) complex was introduced to a poly (ether sulfone) (PES) casting solution as a hydrophilic additive to fabricate ITF/PES ultrafiltration (UF) membranes via non-solvent-induced phase separation (NIPS). The structure and performance of the PES membranes with ITF concentrations ranging from 0 to 0.9wt.% were systematically investigated by scanning electron microscopy, water contact angle, permeability, protein rejection and fouling resistance measurements. The results indicate that the pore structure and surface properties of PES UF membranes can be regulated by incorporating the ITF complex. Compared with classical PES membranes, ITF/PES membranes were found to have an increased hydrophilicity and porosity and reduced surface pore size. Importantly, a simultaneous enhancement of permeability and separation performance was observed for the blend membranes, which indicates that the introduction of the ITF complex can break through the trade-off between permeability and selectivity of UF membranes.When the ITF content was 0.3wt.%, the permeability reached a maximum of 319.4(L/m(2)h) at 0.1MPa, which is 1.6 times higher than that of the classical PES membrane. Furthermore, the BSA rejection increased from 25.9% for the PES membrane to 95.9% for the enhanced membrane. In addition, the same membrane showed an improved fouling resistance (higher flux recovery and lower adhesion force) and stable hydrophilicity (unchanged after incubation in deionized water for 30days). The simple, green and cost-effective preparation process and the outstanding filtration performance highlight the potential of ITF/PES membranes for practical applications. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Unexpected water flow through Nafion-tube punctures.

    PubMed

    O'Rourke, Colin; Klyuzhin, Ivan; Park, Ji Sun; Pollack, Gerald H

    2011-05-01

    When a Nafion tube is immersed in water and a small hole is punched in the tube's wall, an unexpected phenomenon occurs: Water flows continuously into the tube through the hole. The phenomenon has proved repeatable, and dynamic aspects were therefore explored, including the effects of altered pH and introduction of a second hole. It appears that the flow is closely tied to the recently discovered "exclusion zone" that forms as an annulus inside the Nafion tube. These zones generate protons in the core of the tube, which exert pressure on the menisci; once a hole is punched, the pressure is relieved by sucking water through the hole. This hypothesis is consistent with the observed experimental evidence and may be relevant to the mechanism of water transport in trees.

  14. Study and development of sulfated zirconia based proton exchange fuel cell membranes

    NASA Astrophysics Data System (ADS)

    Kemp, Brittany Wilson

    With the increasing consumption of energy, fuel cells are among the most promising alternatives to fossil fuels, provided some technical challenges are overcome. Proton exchange membrane fuel cells (PEMFCs) have been investigated and improvements have been made, but the problem with NafionRTM, the main membrane for PEMFCs, has not been solved. NafionRTM restricts the membranes from operating at higher temperatures, thus preventing them from working in small electronics. The problem is to develop a novel fuel cell membrane that performs comparably to NafionRTM in PEMFCs. The membranes were fabricated by applying sulfated zirconia, via template wetting, to porous alumina membranes. The fabricated membranes showed a proton conductivity of 0.016 S/cm in comparison to the proton conductivity of Nafion RTM (0.05 S/cm). Both formic acid and methanol had a lower crossover flux through the sulfated zirconia membranes (formic acid- 2.89x10 -7 mols/cm2s and methanol-1.78x10-9 mols/cm2s) than through NafionRTM (formic acid-2.03x10 -8 mols/cm2s methanol-2.42x10-6 mols/cm 2s), indicating that a sulfated zirconia PEMFC may serve as a replacement for NafionRTM.

  15. Composite Electrolyte Membranes from Partially Fluorinated Polymer and Hyperbranched, Sulfonated Polysulfone

    PubMed Central

    Subianto, Surya; Roy Choudhury, Namita; Dutta, Naba

    2013-01-01

    Macromolecular modification of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF) was done with various proportions of sulfonic acid terminated, hyperbranched polysulfone (HPSU) with a view to prepare ion conducting membranes. The PVDF-co-HFP was first chemically modified by dehydrofluorination and chlorosulfonation in order to make the membrane more hydrophilic as well as to introduce unsaturation, which would allow crosslinking of the PVDF-co-HFP matrix to improve the stability of the membrane. The modified samples were characterized for ion exchange capacity, morphology, and performance. The HPSU modified S-PVDF membrane shows good stability and ionic conductivity of 5.1 mS cm−1 at 80 °C and 100% RH for blends containing 20% HPSU, which is higher than the literature values for equivalent blend membranes using Nafion. SEM analysis of the blend membranes containing 15% or more HPSU shows the presence of spherical domains with a size range of 300–800 nm within the membranes, which are believed to be the HPSU-rich area.

  16. Adsorption and activity of Candida rugosa lipase on polypropylene hollow fiber membrane modified with phospholipid analogous polymers.

    PubMed

    Deng, Hong-Tao; Xu, Zhi-Kang; Huang, Xiao-Jun; Wu, Jian; Seta, Patrick

    2004-11-09

    Efforts have recently been made toward the study of interactions of phospholipid with various enzymes. It seems that phospholipids may be directly involved in regulating the enzyme activity. In this work, three phospholipid analogous polymers (PAPs), containing hydrophobic octyloxy, dodecyloxy, and octadecyloxy groups (abbreviated as 8-PAP, 12-PAP, and 18-PAP, respectively), were tethered on polypropylene hollow fiber microfiltration membrane (PPHFMM) to create a biocompatible interface for lipase immobilization. Lipase from Candida rugosa was immobilized on these PPHFMMs by adsorption. The adsorption capacity, activity, and thermal stability of enzyme on the PAP-modified PPHFMMs were compared with those of enzyme on the nascent ones. It was found that, as for the PAP-modified PPHFMMs, the adsorption capacities of lipase are lower than that of the nascent ones, while the activity retention of immobilized lipase increases from 57.5% to 74.1%, 77.5%, and 83.2% respectively for the 8-PAP-, 12-PAP-, and 18-PAP-modified PPHFMMs. In addition, the experimental results of thermal stability show that the residual activity of the immobilized lipase at 50 degrees C for 2 h is 62% for the 8-PAP-modified PPHFMM, 59% for the 12-PAP-modified PPHFMM, and 66% for the 18-PAP-modified PPHFMM, which are also higher than that of the nascent ones.

  17. Voltammetric heparin-selective electrode based on thin liquid membrane with conducting polymer-modified solid support.

    PubMed

    Guo, Jidong; Amemiya, Shigeru

    2006-10-01

    A novel, solid-supported voltammetric ion-selective electrode to detect anticoagulant/antithrombotic heparin at polarizable poly(vinyl chloride) (PVC) membrane/water interfaces was developed. An approximately 3-4.5-microm-thick PVC membrane plasticized with 2-nitrophenyl octyl ether was supported on a gold electrode modified with a poly(3-octylthiophene) (POT) film as an ion-to-electron transducer. Charge transport through the PVC-covered POT film is electrochemically reversible, as demonstrated by cyclic voltammetry with nonpolarizable membrane/water interfaces. In addition to the fast charge transport, adequate redox capacity of the POT film and a small ohmic potential drop in the thin PVC membrane enable ion transfer voltammetry at polarizable macroscopic membrane/water interfaces in a standard three-electrode cell. Reversible ClO4- transfer at the interfaces coupled with oxidation of a neutral POT film was examined by cyclic voltammetry to determine the distribution of the applied potential to the two polarizable interfaces by convolution technique. Interfacial adsorption and desorption of heparin facilitated by octadecyltrimethylammonium were studied also by cyclic voltammetry and convolution technique to demonstrate that the processes are electrochemically irreversible. Stripping voltammetry based on the interfacial processes gives a low detection limit of 0.005 unit/mL heparin in a saline solution, which is slightly lower than the detection limit of most sensitive heparin sensors reported so far (0.01 unit/mL).

  18. Effect of gating modifier toxins on membrane thickness: implications for toxin effect on gramicidin and mechanosensitive channels.

    PubMed

    Chen, Rong; Chung, Shin-Ho

    2013-02-22

    Various gating modifier toxins partition into membranes and interfere with the gating mechanisms of biological ion channels. For example, GsMTx4 potentiates gramicidin and several bacterial mechanosensitive channels whose gating kinetics are sensitive to mechanical properties of the membrane, whereas binding of HpTx2 shifts the voltage-activity curve of the voltage-gated potassium channel Kv4.2 to the right. The detailed process by which the toxin partitions into membranes has been difficult to probe using molecular dynamics due to the limited time scale accessible. Here we develop a protocol that allows the spontaneous assembly of a polypeptide toxin into membranes in atomistic molecular dynamics simulations of tens of nanoseconds. The protocol is applied to GsMTx4 and HpTx2. Both toxins, released in water at the start of the simulation, spontaneously bind into the lipid bilayer within 50 ns, with their hydrophobic patch penetrated into the bilayer beyond the phosphate groups of the lipids. It is found that the bilayer is about 2 Å thinner upon the binding of a GsMTx4 monomer. Such a thinning effect of GsMTx4 on membranes may explain its potentiation effect on gramicidin and mechanosensitive channels.

  19. Separation of hematopoietic stem cells from human peripheral blood through modified polyurethane foaming membranes.

    PubMed

    Higuchi, Akon; Sekiya, Mayu; Gomei, Yumiko; Sakurai, Masaru; Chen, Wen-Yih; Egashira, Satsuki; Matsuoka, Yuki

    2008-06-15

    Cell separation from peripheral blood was investigated using polyurethane (PU) foam membranes having 5.2 mum pore size and coated with Pluronic F127 or hyaluronic acid. The permeation ratio of hematopoietic stem cells (CD34(+) cells) and lymphocytes through the membranes was lower than for red blood cells and platelets. Adhered cells were detached from membrane surfaces using human serum albumin (HSA) solution after permeation of blood through the membranes, allowing isolation of CD34(+) cells in the permeate (recovery) solution. High-yield isolation of CD34(+) cells was achieved using Pluronic-coated membranes. This was because the Pluronic coating dissolved into the recovery solution at 4 degrees C, releasing adhered cells from the surfaces of the membranes during permeation of HSA solution through these membranes. Dextran and/or bovine serum albumin solutions were also evaluated for use as recovery solutions after blood permeation. A high recovery ratio of CD34(+) cells was achieved at 4 degrees C in a process using 20% dextran solution through PU membranes having carboxylic acid groups.

  20. Cellulose Acetate Modified Titanium Dioxide (TiO2) Nanoparticles Electrospun Composite Membranes: Fabrication and Characterization

    NASA Astrophysics Data System (ADS)

    Das, Chandan; Gebru, Kibrom Alebel

    2017-08-01

    Hybrid membranes from Cellulose Acetate (CA) and titanium oxide (TiO2) nanoparticles were fabricated using electrospinning technique. The electrospun hybrid membranes were characterized using field emission scanning electron microscopy, high energy electrons of the energy dispersive X-ray spectroscopy, X-ray diffraction patterns, atomic force microscopy, zeta potential (ζ), and thermo gravimetric analysis. The impact of TiO2 contents on the electrospun membranes matrix was studied in detail. All these characterization results indicated that TiO2 were uniformly distributed within the CA electrospun membrane's matrix. The addition of TiO2 caused formation of largely interconnected fiber networks which in turn have a positive effect on the enhancement of the membrane pore structures. As the amount of TiO2 addition was raised from 0 to 6.5 wt%, the entanglements of the fibers and the spider-net like network among fibers were increased.

  1. Efficient Targeting of Fatty-Acid Modified Oligonucleotides to Live Cell Membranes through Stepwise Assembly

    PubMed Central

    2014-01-01

    Lipid modifications provide efficient targeting of oligonucleotides to live cell membranes in a range of applications. Targeting efficiency is a function of the rate of lipid DNA insertion into the cell surface and its persistence over time. Here we show that increasing lipid hydrophobicity increases membrane persistence, but decreases the rate of membrane insertion due to the formation of nonproductive aggregates in solution. To ameliorate this effect, we split the net hydrophobicity of the membrane anchor between two complementary oligonucleotides. When prehybridized in solution, doubly anchored molecules also aggregate due to their elevated hydrophobicity. However, when added sequentially to cells, aggregation does not occur so membrane insertion is efficient. Hybridization between the two strands locks the complexes at the cell surface by increasing net hydrophobicity, increasing their total concentration and lifetime, and dramatically improving their utility in a variety of biomedical applications. PMID:25325667

  2. Staphylococcal Phenotypes Induced by Naturally Occurring and Synthetic Membrane-Interactive Polyphenolic β-Lactam Resistance Modifiers

    PubMed Central

    Palacios, Lucia; Rosado, Helena; Micol, Vicente; Rosato, Adriana E.; Bernal, Patricia; Arroyo, Raquel; Grounds, Helen; Anderson, James C.; Stabler, Richard A.; Taylor, Peter W.

    2014-01-01

    Galloyl catechins, in particular (-)-epicatechin gallate (ECg), have the capacity to abrogate β-lactam resistance in methicillin-resistant strains of Staphylococcus aureus (MRSA); they also prevent biofilm formation, reduce the secretion of a large proportion of the exoproteome and induce profound changes to cell morphology. Current evidence suggests that these reversible phenotypic traits result from their intercalation into the bacterial cytoplasmic membrane. We have endeavoured to potentiate the capacity of ECg to modify the MRSA phenotype by stepwise removal of hydroxyl groups from the B-ring pharmacophore and the A:C fused ring system of the naturally occurring molecule. ECg binds rapidly to the membrane, inducing up-regulation of genes responsible for protection against cell wall stress and maintenance of membrane integrity and function. Studies with artificial membranes modelled on the lipid composition of the staphylococcal bilayer indicated that ECg adopts a position deep within the lipid palisade, eliciting major alterations in the thermotropic behaviour of the bilayer. The non-galloylated homolog (-)-epicatechin enhanced ECg-mediated effects by facilitating entry of ECg molecules into the membrane. ECg analogs with unnatural B-ring hydroxylation patterns induced higher levels of gene expression and more profound changes to MRSA membrane fluidity than ECg but adopted a more superficial location within the bilayer. ECg possessed a high affinity for the positively charged staphylococcal membrane and induced changes to the biophysical properties of the bilayer that are likely to account for its capacity to disperse the cell wall biosynthetic machinery responsible for β-lactam resistance. The ability to enhance these properties by chemical modification of ECg raises the possibility that more potent analogs could be developed for clinical evaluation. PMID:24699700

  3. Preparation of antifouling polyvinylpyrrolidone (PVP 40K) modified polyethersulfone (PES) ultrafiltration (UF) membrane for water purification

    NASA Astrophysics Data System (ADS)

    Vatsha, Banele; Ngila, Jane Catherine; Moutloali, Richard M.

    This study reports the fabrication of polyethersulfone (PES) membrane using the phase inversion method in the presence of polyvinylpyrrolidone (PVP, 40K) as pore-forming agent. The membranes were made from two PES concentration types, i.e. 16 and 18 wt.%. The effect of high molecular weight PVP concentration (2-10%) was examined in order to obtain a membrane with good performance, i.e. high water flux and reasonable Bovine Serum Albumin (BSA, protein model solution) rejection. The optimised membranes were characterised by ATR-FTIR, AFM, SEM, contact angle and dead-end membrane filtration tests. It was found that PVP moieties have positive influence in the prepared PES membranes. SEM surface and cross-sectional images were used to observed morphological changes as PVP content was varied. The pore sizes increased with PVP content for membranes prepared from 16 wt.% PES polymer, whereas at the higher PVP content in 18 wt.% PES membrane, pore sizes tend to decrease or completely disappear. The CA decreased gradually for the 16 wt.% PES with increasing PVP content whereas in the 18 wt.% PES the CA decreased initially before tapering off or increasing slightly. The rejection of BSA solution by both neat PES and PVP-containing PES membrane was above 85%. AFM surface topography exhibited increase in roughness value with PVP content. FTIR/ATR spectra corroborated the functional composition of neat PES and PVP molecule dispersed on PES membrane backbone. The results attained confirmed the potential industrial application of PVP molecule to minimise fouling tendencies.

  4. Improved antibacterial activity of nanofiltration polysulfone membranes modified with silver nanoparticles.

    PubMed

    Andrade, Patricia Fernanda; de Faria, Andreia Fonseca; Oliveira, Silvana Ruella; Arruda, Marco Aurélio Zezzi; Gonçalves, Maria do Carmo

    2015-09-15

    Polysulfone membranes (PSf) containing silver nanoparticles were prepared by the wet phase-inversion process. Silver nanoparticles (AgNP) were dispersed into the polymer matrix using two different methodologies. In the first one, the AgNP were synthesized and further dispersed into the polymer solution (ex situ process). In the second method, the formation of the AgNP was performed in situ. The AgNP crystalline structure in the PSf membranes was confirmed by X-ray diffraction. Field emission scanning electron microscopy images showed that the addition of AgNP in PSf membranes caused no significant changes to the finger-like morphology. When the ex situ methodology was applied, 45 nm average size AgNP were uniformly distributed in the internal pores of the membranes. However, when the AgNP were formed through the in situ process, the AgNP were uniformly and preferentially distributed on the top and bottom surfaces of the membrane. In the last case, the AgNP showed cubic morphology when present in the bottom and top surfaces, however, when inside the membrane their morphology was spherical. The cubic-like nanoparticles displayed a 38 nm average edge length. The silver ion released from the membrane during water filtration was measured using inductively coupled plasma mass spectrometry, which showed a silver leaching of approximately 2 μg L(-1). The nanocomposite membranes prepared by the in situ method exhibited a better antibacterial activity, in comparison to those prepared by ex situ, and also a decrease in 90% Escherichia coli adhered cells compared to the pristine PSf membranes. In conclusion, the in situ procedure can be considered a feasible, simple, and reproducible methodology to prepare anti-biofouling polysulfone membranes containing AgNP.

  5. Transparent Bipolar Membrane for Water Splitting Applications.

    PubMed

    Chabi, Sakineh; Wright, Andrew G; Holdcroft, Steven; Freund, Michael S

    2017-08-16

    This study describes the use of a benzimidazolium-based anion exchange membrane for creating bipolar membranes and the assessment of their suitability for solar-driven water splitting. Bipolar membranes were prepared by laminating anion exchange membrane with Nafion NR-211 membrane without modification of the interface. Under acidic and basic conditions, proton and hydroxide ion conductivities of 103 and 102 mS cm(-1) were obtained for Nafion and benzimidazolium-based membranes, respectively. The fabricated bipolar membranes have an average thickness of 90 μm and show high transmittance, up to 75% of the visible light. The findings suggest that the two membranes create a sharp hydrophilic interface with a space charge region of only a few nanometers, thereby generating a large electric field at the interface that enhances water dissociation.

  6. Novel Swelling-Resistant Sodium Alginate Membrane Branching Modified by Glycogen for Highly Aqueous Ethanol Solution Pervaporation.

    PubMed

    Ji, Chen-Hao; Xue, Shuang-Mei; Xu, Zhen-Liang

    2016-10-12

    A novel carbohydrate chain cross-linking method of sodium alginate (SA) is proposed in which glycogen with the branched-chain structure is utilized to cross-link with SA matrix by the bridging of glutaraldehyde (GA). The active layer of SA composite ceramic membrane modified by glycogen and GA for pervaporation (PV) demonstrates great advantages. The branched structure increases the chain density of the active layer, which compresses the free volume between the carbohydrate chains of SA. Large amounts of hydroxyl groups are consumed during the reaction with GA, which reduces the hydrogen bond formation between water molecules and the polysaccharide matrix. The two factors benefit the active layer with great improvement in swelling resistance, promoting the potential of the active layer for the dehydration of an ethanol-water solution containing high water content. Meanwhile, the modified active layer is loaded on the rigid α-Al2O3 ceramic membrane by dip-coating method with the enhancement of anti-deformation and controllable thickness of the active layer. Characterization techniques such as SEM, AFM, XRD, FTIR, XPS, and water contact angle are utilized to observe the composite structure and surface morphology of the composite membrane, to probe the free volume variation, and to determine the chemical composition and hydrophilicity difference of the active layer caused by the different glycogen additive amounts. The membrane containing 3% glycogen in the selective layer demonstrates the flux at 1250 g m(-2) h(-1) coupled with the separation factor of 187 in the 25 wt % water content feed solution at the operating temperature of 75 °C, reflecting superior pervaporation processing capacity compared with the general organic PV membranes in the same condition.

  7. Low Crossover Polymer Electrolyte Membranes for Direct Methanol Fuel Cells

    NASA Technical Reports Server (NTRS)

    Prakash, G. K. Surya; Smart, Marshall; Atti, Anthony R.; Olah, George A.; Narayanan, S. R.; Valdez, T.; Surampudi, S.

    1996-01-01

    Direct Methanol Fuel Cells (DMFC's) using polymer electrolyte membranes are promising power sources for portable and vehicular applications. State of the art technology using Nafion(R) 117 membranes (Dupont) are limited by high methanol permeability and cost, resulting in reduced fuel cell efficiencies and impractical commercialization. Therefore, much research in the fuel cell field is focused on the preparation and testing of low crossover and cost efficient polymer electrolyte membranes. The University of Southern California in cooperation with the Jet Propulsion Laboratory is focused on development of such materials. Interpenetrating polymer networks are an effective method used to blend polymer systems without forming chemical links. They provide the ability to modify physical and chemical properties of polymers by optimizing blend compositions. We have developed a novel interpenetrating polymer network based on poly (vinyl - difluoride)/cross-linked polystyrenesulfonic acid polymer composites (PVDF PSSA). Sulfonation of polystyrene accounts for protonic conductivity while the non-polar, PVDF backbone provides structural integrity in addition to methanol rejection. Precursor materials were prepared and analyzed to characterize membrane crystallinity, stability and degree of interpenetration. USC JPL PVDF-PSSA membranes were also characterized to determine methanol permeability, protonic conductivity and sulfur distribution. Membranes were fabricated into membrane electrode assemblies (MEA) and tested for single cell performance. Tests include cell performance over a wide range of temperatures (20 C - 90 C) and cathode conditions (ambient Air/O2). Methanol crossover values are measured in situ using an in-line CO2 analyzer.

  8. Impedance Spectroscopic Investigation of Proton Conductivity in Nafion Using Transient Electrochemical Atomic Force Microscopy (AFM)

    PubMed Central

    Hink, Steffen; Wagner, Norbert; Bessler, Wolfgang G.; Roduner, Emil

    2012-01-01

    Spatially resolved impedance spectroscopy of a Nafion polyelectrolyte membrane is performed employing a conductive and Pt-coated tip of an atomic force microscope as a point-like contact and electrode. The experiment is conducted by perturbing the system by a rectangular voltage step and measuring the incurred current, followed by Fourier transformation and plotting the impedance against the frequency in a conventional Bode diagram. To test the potential and limitations of this novel method, we present a feasibility study using an identical hydrogen atmosphere at a well-defined relative humidity on both sides of the membrane. It is demonstrated that good quality impedance spectra are obtained in a frequency range of 0.2–1000 Hz. The extracted polarization curves exhibit a maximum current which cannot be explained by typical diffusion effects. Simulation based on equivalent circuits requires a Nernst element for restricted diffusion in the membrane which suggests that this effect is based on the potential dependence of the electrolyte resistance in the high overpotential region. PMID:24958175

  9. Molecular modeling of the pendant chain in Nafion{reg_sign}

    SciTech Connect

    Paddison, S.J.; Zawodzinski, T.A.

    1998-03-01

    Ion transport through perfluorosulfonic acid ionomers such as Nafion{reg_sign} is controlled by both the microstructure of the polymer and the charge and water distribution in the hydrated polymer. The authors present here the results of theoretical calculations on the side chain of Nafion{reg_sign}, establishing microscopic information for the modeling of water modeling of water modeling of water and proton transport in the membrane. Optimized geometries for the trifluoromethane sulfonic acid fragment (CF{sub 3}SO{sub 3}H), the di-trifluoromethane ether fragment (CF{sub 3}OCF{sub 3}), and the side chain (CF{sub 3}{single_bond}OCF{sub 2}CF(CF{sub 3})OCF{sub 2}CF{sub 2}SO{sub 3}H) were determined by means of both ab initio Hartree Fock theory with second order Moeller-Plesset electron correlation corrections, and density functional theory with Becke`s three parameter hybrid method. Several rotational potential energy surfaces were calculated to assess chain flexibility and proton accessibility. A probe water molecule was added to each of the fragments to characterize hydrophilic sites. These calculations confirmed that the sulfonic acid group is hydrophilic and the ethers are hydrophobic. Molecular dynamics simulations were then performed on the side chain to check the conditions required to stretch the pendant chain. Thermal averages of several structural parameters assessing the flexibility and stretch of the chain were computed from selected conformations produced in the simulation and these results indicate that although the sulfonate group is free to rotate, the chain stretches little. The construction of a potential energy surface for rotation about the second ether group suggests that the side chain exists in a folded or curled up conformation. A physical continuum dielectric solvent model was used to obtain free energies of electrostatic interaction of the fragments and the full chain with the solvent.

  10. Preparation and characterization of nanocomposite membranes made of poly(2,6-dimethyl-1,4-phenylene oxide) and montmorillonite for direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Hasani-Sadrabadi, Mohammad Mahdi; Emami, Shahriar Hojjati; Moaddel, Homayoun

    Partially sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (sulfonated PPO) with various degrees of sulfonation were prepared. The solutions were mixed with organically modified montmorillonite (MMT) to prepare membranes by solvent casting. By increasing the sulfonation degree up to 40% for membranes without MMT, ion exchange capacity, water uptake and proton conductivity reached 2.59 mequiv. g -1, 21% and 0.0182 S cm -1, respectively. The Fourier transfer infrared (FTIR) analysis of sulfonated membranes revealed absorption bands at 1060 and 1100-1300 cm -1 for sulfur-oxygen S dbnd O bonds. X-ray diffraction analysis showed the exfoliated structure of clay in polymeric matrices. A sulfonated PPO/MMT membrane with 27% sulfonation and 2.0 wt% MMT loading showed a membrane selectivity of approximately 63,500 compared to 40,500 for Nafion ® 117, and also a higher power density (125 mW cm -2) than Nafion ® 117 (108 mW cm -2) for single cell DMFC in a 5 M methanol feed.

  11. A modified parallel artificial membrane permeability assay for evaluating the bioconcentration of highly hydrophobic chemicals in fish.

    PubMed

    Kwon, Jung-Hwan; Escher, Beate I

    2008-03-01

    Low cost in vitro tools are needed at the screening stage of assessment of bioaccumulation potential of new and existing chemicals because the number of chemical substances that needs to be tested highly exceeds the capacity of in vivo bioconcentration tests. Thus, the parallel artificial membrane permeability assay (PAMPA) system was modified to predict passive uptake/ elimination rate in fish. To overcome the difficulties associated with low aqueous solubility and high membrane affinity of highly hydrophobic chemicals, we measured the rate of permeation from the donor poly(dimethylsiloxane)(PDMS) disk to the acceptor PDMS disk through aqueous and PDMS membrane boundary layers and term the modified PAMPA system "PDMS-PAMPA". Twenty chemicals were selected for validation of PDMS-PAMPA. The measured permeability is proportional to the passive elimination rate constant in fish and was used to predict the "minimum" in vivo elimination rate constant. The in vivo data were very close to predicted values except for a few polar chemicals and metabolically active chemicals, such as pyrene and benzo[a]pyrene. Thus, PDMS-PAMPA can be an appropriate in vitro system for nonmetabolizable chemicals. Combination with metabolic clearance rates using a battery of metabolic degradation assays would enhance the applicability for metabolizable chemicals.

  12. Modified gas-permeable silicone rubber membranes for covalent immobilisation of enzymes and their use in biosensor development.

    PubMed

    Schüler, R; Wittkampf, M; Chemnitius, G C

    1999-08-01

    Novel enzyme membranes are introduced. Modified polymeric gas-permeable layers were developed enabling biological components which have available reactive groups (-NH2, -OH, -SH, -COOH) to couple covalently on to their surfaces. Therefore, gas-permeable two component room temperature vulcanizing (2K-RTV) silicone rubber was modified using additional cross-linking agents. Triethoxysilanes with functional groups on their side chains such as epoxy or amino groups were used. A special attribute of the resulting gas-permeable membranes is that their formation and modification occur simultaneously during one reaction step. IR spectroscopy was used to observe the changes in the polymeric structure due to the reaction with the additional cross-linking agents. Sensors equipped with these layers are suitable to measure dissolved gases such as O2, CO2 and NH3 consumed or produced by enzymes converting their substrates. Determination of glucose, a well investigated enzymatic detection process, was chosen to demonstrate the applicability of the enzyme immobilisation. Glucose oxidase was immobilised on the membranes and glucose was detected by amperometric measurement of oxygen consumption. It is expected that this immobilisation method will also be useful for miniaturised planar biosensors.

  13. BASELINE MEMBRANE SELECTION AND CHARACTERIZATION FOR AN SDE

    SciTech Connect

    Colon-Mercado, H; David Hobbs, D

    2007-04-03

    Thermochemical processes are being developed to provide global-scale quantities of hydrogen. A variant on sulfur-based thermochemical cycles is the Hybrid Sulfur (HyS) Process which uses a sulfur dioxide depolarized electrolyzer (SDE) to produce the hydrogen. In FY05 and FY06, testing at the Savannah River National Laboratory (SRNL) explored a low temperature fuel cell design concept for the SDE. The advantages of this design concept include high electrochemical efficiency and small footprint that are crucial for successful implementation on a commercial scale. A key component of the SDE is the ion conductive membrane through which protons produced at anode migrate to the cathode and react to produce hydrogen. An ideal membrane for the SDE should have both low ionic resistivity and low sulfur dioxide transport. These features allow the electrolyzer to perform at high currents with low potentials, along with preventing contamination of both the hydrogen output and poisoning of the catalysts involved. Another key component is the electrocatalyst material used for the anode and cathode. Good electrocatalysts should be chemically stable and have a low overpotential for the desired electrochemical reactions. This report summarizes results from activities to evaluate commercial and experimental membranes for the SDE. Several different types of commercially-available membranes were analyzed for sulfur dioxide transport as a function of acid strength including perfluorinated sulfonic acid (PFSA), sulfonated poly-etherketone-ketone, and poly-benzimidazole (PBI) membranes. Experimental membranes from the sulfonated diels-alder polyphenylenes (SDAPP) and modified Nafion{reg_sign} 117 were evaluated for SO{sub 2} transport as well. These membranes exhibited reduced transport coefficient for SO{sub 2} transport without the loss in ionic conductivity. The use of Nafion{reg_sign} with EW 1100 is recommended for the present SDE testing due to the limited data regarding chemical

  14. Construction of functional pancreatic artificial islet tissue composed of fibroblast-modified polylactic- co-glycolic acid membrane and pancreatic stem cells.

    PubMed

    Liu, Liping; Tan, Jing; Li, Baoyuan; Xie, Qian; Sun, Junwen; Pu, Hongli; Zhang, Li

    2017-09-01

    Objective To improve the biocompatibility between polylactic- co-glycolic acid membrane and pancreatic stem cells, rat fibroblasts were used to modify the polylactic- co-glycolic acid membrane. Meanwhile, we constructed artificial islet tissue by compound culturing the pancreatic stem cells and the fibroblast-modified polylactic- co-glycolic acid membrane and explored the function of artificial islets in diabetic nude mice. Methods Pancreatic stem cells were cultured on the fibroblast-modified polylactic- co-glycolic acid membrane in dulbecco's modified eagle medium containing activin-A, β-catenin, and exendin-4. The differentiated pancreatic stem cells combined with modified polylactic- co-glycolic acid membrane were implanted subcutaneously in diabetic nude mice. The function of artificial islet tissue was explored by detecting blood levels of glucose and insulin in diabetic nude mice. Moreover, the proliferation and differentiation of pancreatic stem cells on modified polylactic- co-glycolic acid membrane as well as the changes on the tissue structure of artificial islets were investigated by immunofluorescence and haematoxylin and eosin staining. Results The pancreatic stem cells differentiated into islet-like cells and secreted insulin when cultured on fibroblast-modified polylactic- co-glycolic acid membrane. Furthermore, when the artificial islet tissues were implanted into diabetic nude mice, the pancreatic stem cells combined with polylactic- co-glycolic acid membrane modified by fibroblasts proliferated, differentiated, and secreted insulin to reduce blood glucose levels in diabetic nude mice. Conclusion Pancreatic stem cells can be induced to differentiate into islet-like cells in vitro. In vivo, the artificial islet tissue can effectively regulate the blood glucose level in nude mice within a short period. However, as time increased, the structure of the artificial islets was destroyed due to the erosion of blood cells that resulted in the gradual

  15. A new deposition method for the preparation of Pt-Pd nanocatalysts on a nafion coated carbon black via the reduction of metallic precursors in a drying process.

    PubMed

    Lee, Jae-Young; Shim, Joongpyo; Hong, Sung-Wan; Han, Kyeongsik; Lee, Woo-Kum; Lee, Hong-Ki

    2013-05-01

    A simple method for the synthesis of Pt-Pd nanocatalysts was developed for a proton-exchange membrane fuel cell (PEMFC), which was loaded on a nafion coated carbon black via the sequential reduction of palladium(II) bis(acetylacetonato) and platinum(II) bis(acetylacetonato) in a drying process. Metallic precursors were sublimed and reduced on a nafion coated carbon black which was spray coated on a gas diffusion layer (GDL) in a glass reactor of N2 atmosphere at 180 degrees C for various times. The morphology and distribution of the Pt and Pd nanoparticles were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and we found that the loading weight, number density and particle size of Pt-Pd nanoparticles increased with increasing exposure time at 180 degrees C.

  16. Electrochemical Properties of a Thiol Monolayers Coated Gold Electrode Modified with Osmium Gel Membrane as Enzyme Sensor

    NASA Astrophysics Data System (ADS)

    Yabutani, Tomoki; Okada, Nobuyuki; Maruyama, Kenichi; Motonaka, Junko

    The electrochemical behavior of an enzyme sensor for glucose using a gold electrode modified with thiol self-assembled membrane and osmium complex gel as an electron transferring mediator has further been investigated by electrochemical analysis. The gold electrode was initially coated with aminomethanethiol self assembling mono layer membrane(thiol-SAM) and then immobilized with glucose oxidase using poly(vinylpyridine-co-allylamine) (PVP-co-AA), gel coordinated with osmium bipyridine complexes (GOD/Os-PVP-co-AA gel). The cleaning condition of the surface of the Au electrode prior to coating thiol SAM was optimized for reduction of interference caused by concomitant compounds. It was found that interfering influence was most efficiently reduced in the case of use of the Au electrode immersed into nitric acid. The current ratio with a thiol coated gold electrode modified with Os-PVP-co-AA gel in glucose solution in the presence to absence of ascorbic acid, acetaminophen, and uric acid (ID+I/II) was 1.006, 1.014, and 1.018, respectively. The peak current response of glucose in the electrode modified with thiol SAM was dropped to 60 98% as compared with that without thiol SAM.

  17. High resolution neutron imaging of water in the polymer electrolyte fuel cell membrane

    SciTech Connect

    Mukherjee, Partha P; Makundan, Rangachary; Spendelow, Jacob S; Borup, Rodney L; Hussey, D S; Jacobson, D L; Arif, M

    2009-01-01

    Water transport in the ionomeric membrane, typically Nafion{reg_sign}, has profound influence on the performance of the polymer electrolyte fuel cell, in terms of internal resistance and overall water balance. In this work, high resolution neutron imaging of the Nafion{reg_sign} membrane is presented in order to measure water content and through-plane gradients in situ under disparate temperature and humidification conditions.

  18. Selective label-free electrochemical impedance measurement of glycated haemoglobin on 3-aminophenylboronic acid-modified eggshell membranes.

    PubMed

    Boonyasit, Yuwadee; Heiskanen, Arto; Chailapakul, Orawan; Laiwattanapaisal, Wanida

    2015-07-01

    We propose a novel alternative approach to long-term glycaemic monitoring using eggshell membranes (ESMs) as a new immobilising platform for the selective label-free electrochemical sensing of glycated haemoglobin (HbA1c), a vital clinical index of the glycaemic status in diabetic individuals. Due to the unique features of a novel 3-aminophenylboronic acid-modified ESM, selective binding was obtained via cis-diol interactions. This newly developed device provides clinical applicability as an affinity membrane-based biosensor for the identification of HbA1c over a clinically relevant range (2.3 - 14 %) with a detection limit of 0.19%. The proposed membrane-based biosensor also exhibited good reproducibility. When analysing normal and abnormal HbA1c levels, the within-run coefficients of variation were 1.68 and 1.83%, respectively. The run-to-run coefficients of variation were 1.97 and 2.02%, respectively. These results demonstrated that this method achieved the precise and selective measurement of HbA1c. Compared with a commercial HbA1c kit, the results demonstrated excellent agreement between the techniques (n = 15), demonstrating the clinical applicability of this sensor for monitoring glycaemic control. Thus, this low-cost sensing platform using the proposed membrane-based biosensor is ideal for point-of-care diagnostics.

  19. In situ synthesis of MOF membranes on ZnAl-CO3 LDH buffer layer-modified substrates.

    PubMed

    Liu, Yi; Wang, Nanyi; Pan, Jia Hong; Steinbach, Frank; Caro, Jürgen

    2014-10-15

    We develop here a urea hydrolysis method to in situ prepare asymmetric ZnAl-CO3 layered double hydroxide (LDH) buffer layers with various stable equilibrium morphology on porous Al2O3 substrates. In particular it is found that well-intergrown ZIF-8 membranes can be directly synthesized on the ZnAl-CO3 LDH buffer layer-modified substrates, owing to the specific metal-imidazole interaction between ZnAl-CO3 LDHs and ZIF-8. Other Zn-based MOF membranes, like ZIF-7 and ZIF-90, can also be synthesized with this method. Our finding demonstrates that LDH buffer layer represents a new concept for substrate modification.

  20. Highly effective permeability and antifouling performances of polypropylene non-woven fabric membranes modified with graphene oxide by inkjet printing and immersion coating methods.

    PubMed

    Zhao, Chuan-Qi; Xu, Xiao-Chen; Li, Rui-Yun; Chen, Jie; Yang, Feng-Lin

    2013-01-01

    In the current study, graphene oxide (GO)-modified polypropylene non-woven fabric (PP-NWF) membranes were prepared via inkjet printing and immersion coating methods. Scanning electron microscopy, Fourier transform infrared spectroscopy, contact angle measurements, pure water permeation (JPWP) and protein adsorption were tested to evaluate the impact of the GO nanosheet on the characteristics and performance of modified PP-NWF membranes. The results showed that the exfoliated GO nanosheets uniformly deposited on the membrane surface and firmly embedded into the interlaced fibers, resulting in the improvement of membrane hydrophilicity, permeability and antifouling properties comparing with original PP-NWF membranes. The GO-printed and GO-coated membranes had 113 and 188% higher fluxes, and 70.95 and 75.74% lower protein adsorptions than the original PP-NWF membranes, respectively. After cross-linked treatment, ultrasound processing was conducted to evaluate the stability of the modified PP-NWF membranes. The results demonstrated that there was almost no decrease in permeation after ultrasonic treatment indicating that the cross-linking treatment could enhance the immobilization of the GO nanosheets on and into the modified membranes.

  1. Chelating polymer modified P84 nanofiltration (NF) hollow fiber membranes for high efficient heavy metal removal.

    PubMed

    Gao, Jie; Sun, Shi-Peng; Zhu, Wen-Ping; Chung, Tai-Shung

    2014-10-15

    High performance nanofiltration (NF) membranes for heavy metal removal have been molecularly designed by adsorption of chelating polymers containing negatively charged functional groups such as poly (acrylic acid-co-maleic acid) (PAM), poly (acrylic acid) (PAA) and poly (dimethylamine-co-epichlorohydrin-co-ethylenediamine) (PDMED) on the positively charged polyethyleneimine (PEI) cross-linked P84 hollow fiber substrates. Not only do these chelating polymers change the membrane surface charge and pore size, but also provide an extra mean to remove heavy metal ions through adsorption in addition to traditional steric effect and Donnan exclusion. The adsorbed membranes have comparable water permeability and superior rejections to heavy metals, for instance, Pb(NO3)2, CuSO4, NiCl2, CdCl2, ZnCl2, Na2Cr2O7 and Na2HAsO4, with rejections higher than 98%. The membranes also display excellent rejections to mixed ions with rejections more than 99%. The newly developed membranes show reasonably stability during 60-h tests as well as multiple washes.

  2. Pure And Modified Co-poly(amide-12-b-ethylene oxide) Membranes For Gas Separation Studied By Molecular Investigations

    NASA Astrophysics Data System (ADS)

    Tocci, Elena; De Lorenzo, Luana; Gugliuzza, Annarosa; Macchione, Marialuigia; Drioli, Enrico

    2010-10-01

    A combined experimental and theoretical study has been performed to investigate transport properties in a pure and modified poly(amide-12-b-ethylene oxide) (PEBAX®2533) block copolymer membrane with N-ethylo,p-toluenesulphonamide (KET) as additive molecules. MD simulations using COMPASS force field, Gusev-Suter Transition State Theory (TST) and Monte Carlo methods have been used. Bulk models of PEBAX®2533 and PEBAX/KET in different copolymer/additive compositions have been assembled and analysed to evaluate gas permeability and the morphology to characterize structure-performance relationships.

  3. Pure and Modified Co-Poly(amide-12-b-ethylene oxide) Membranes for Gas Separation Studied by Molecular Investigations

    PubMed Central

    De Lorenzo, Luana; Tocci, Elena; Gugliuzza, Annarosa; Drioli, Enrico

    2012-01-01

    This paper deals with a theoretical investigation of gas transport properties in a pure and modified PEBAX block copolymer membrane with N-ethyl-o/p-toluene sulfonamide (KET) as additive molecules. Molecular dynamics simulations using COMPASS force field, Gusev-Suter Transition State Theory (TST) and Monte Carlo methods were used. Bulk models of PEBAX and PEBAX/KET in different copolymer/additive compositions were assembled and analyzed to evaluate gas permeability and morphology to characterize structure-performance relationships. PMID:24958285

  4. Degradation analyses of Ru85Se15 catalyst layer in proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Zheng, Qiaoming; Cheng, Xuan; Jao, Ting-Chu; Weng, Fang-Bor; Su, Ay; Chiang, Yu-Chun

    2012-11-01

    Accelerated degradation tests (ADTs) for the H2/air single cell are carried out at 65 °C and ambient pressure by cycling the cell between 0 and 200 mA cm-2 up to 6000 cycles. Membrane electrode assemblies (MEAs) are prepared using the Nafion 212 membrane and the carbon supported platinum as an anode catalyst, as well as the carbon supported Ru85Se15 as a cathode catalyst prepared with five selected Nafion contents and Ru loads to represent the optimized (33% Nafion and 0.27 mg Ru cm-2), overloaded (43% Nafion and 0.61 mg Ru cm-2) and underloaded (20% Nafion and 0.14 mg Ru cm-2) conditions. The lowest cell performance loss of 44% in terms of peak power density is achieved with 33% Nafion and 0.27 mg Ru cm-2. Very severe losses of 80% and 82% are found for 20% and 43% Nafion contents, respectively, while relatively moderate losses of 57% and 64% for 0.14 and 0.61 mg Ru cm-2, respectively. Dissolution and migration of Se/Ru and corrosion of carbon support from the catalyst, together with the shrinkage and release of sulfonic acid from the membrane are identified and correlated to decayed cell performances.

  5. A novel electrochemical sensor for the analysis of β-agonists: the poly(acid chrome blue K)/graphene oxide-nafion/glassy carbon electrode.

    PubMed

    Lin, Xiaoyun; Ni, Yongnian; Kokot, Serge

    2013-09-15

    A novel modified electrode was constructed by the electro-polymerization of 4,5-dihydroxy-3-[(2-hydroxy-5-sulfophenyl)azo]-2,7-naphthalenedisulfonic acid trisodium salt (acid chrome blue K (ACBK)) at a graphene oxide (GO)-nafion modified glassy carbon electrode (GCE). The characterization of an electrochemically synthesized poly-ACBK/GO-nafion film was investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), atomic force microscopy (AFM) and scanning electron microscopy (SEM) techniques, and the results were interpreted and compared at each stage of the electrode construction. Electrochemical oxidation of eight β-agonists - clenbuterol, salbutamol, terbutaline, ractopamine, dopamine, dobutamine, adrenaline, and isoprenaline, was investigated by CV at the different electrodes. At the poly-ACBK/GO-nafion/GCE, the linear sweep voltammetry peak currents of the eight β-agonists increased linearly with their concentrations in the range of 1.0-36.0 ng mL(-1), respectively, and their corresponding limits of detection (LODs) were within the 0.58-1.46 ng mL(-1) range. This electrode showed satisfactory reproducibility and stability, and was used successfully for the quantitative analysis of clenbuterol in pork samples.

  6. Plasma modified PLA electrospun membranes for actinorhodin production intensification in Streptomyces coelicolor immobilized-cell cultivations.

    PubMed

    Scaffaro, Roberto; Lopresti, Francesco; Sutera, Alberto; Botta, Luigi; Fontana, Rosa Maria; Gallo, Giuseppe

    2017-09-01

    Most of industrially relevant bioproducts are produced by submerged cultivations of actinomycetes. The immobilization of these Gram-positive filamentous bacteria on suitable porous supports may prevent mycelial cell-cell aggregation and pellet formation which usually negatively affect actinomycete submerged cultivations, thus, resulting in an improved biosynthetic capability. In this work, electrospun polylactic acid (PLA) membranes, subjected or not to O2-plasma treatment (PLA-plasma), were used as support for immobilized-cell submerged cultivations of Streptomyces coelicolor M145. This strain produces different bioactive compounds, including the blue-pigmented actinorhodin (ACT) and red-pigmented undecylprodigiosin (RED), and constitutes a model for the study of antibiotic-producing actinomycetes. Wet contact angles and X-ray photoelectron spectroscopy analysis confirmed the increased wettability of PLA-plasma due to the formation of polar functional groups such as carboxyl and hydroxyl moieties. Scanning electron microscope observations, carried out at different incubation times, revealed that S. coelicolor immobilized-cells created a dense "biofilm-like" mycelial network on both kinds of PLA membranes. Cultures of S. coelicolor immobilized-cells on PLA or PLA-plasma membranes produced higher biomass (between 1.5 and 2 fold) as well as higher levels of RED and ACT than planktonic cultures. In particular, cultures of immobilized-cells on PLA and PLA-plasma produced comparable levels of RED that were approximatively 4 and 5 fold higher than those produced by planktonic cultures, respectively. In contrast, levels of ACT produced by immobilized-cell cultures on PLA and PLA-plasma were different, being 5 and 10 fold higher than those of planktonic cultures, respectively. Therefore, this is study demonstrated the positive influence of PLA membrane on growth and secondary metabolite production in S. coelicolor and also revealed that O2-plasma treated PLA membranes

  7. Solubilization of Carbon Nanotubes by Nafion Toward the Preparation of Amperometric Biosensors

    SciTech Connect

    Wang, Joseph; Musameh, Mustafa; Lin, Yuehe )

    2003-03-05

    We report on the ability of the perfluorosulfonated polymer Nafion to solubilize single-wall and multi-wall CNT and on the dramatically enhanced redox activity of hydrogen peroxide at CNT/Nafion-coated electrodes in connection to the preparation of oxidase-based amperometric biosensors.

  8. Virus passage through track-etch membranes modified by salinity and a nonionic surfactant.

    PubMed

    Lytle, C D; Routson, L B; Jain, N B; Myers, M R; Green, B L

    1999-06-01

    Why do viruses sometimes not pass through larger pores in track-etch filters? Increasing the salinity (0.8 to 160 mM Na+) decreased phiX174 and PRD1 passage through track-etch polycarbonate membranes (sodium dodecyl sulfate coated but not polyvinylpyrrolidone coated) and PRD1 passage through polyester membranes. Undiminished passage when 0.1% Tween 80 was added implied that nonionic virus adsorption occurred and indicated that high levels of salinity decreased virus passage by decreasing electrostatic repulsion that prevented adsorption.

  9. Virus Passage through Track-Etch Membranes Modified by Salinity and a Nonionic Surfactant

    PubMed Central

    Lytle, C. David; Routson, Licia B.; Jain, Nisha B.; Myers, Matthew R.; Green, Barbara L.

    1999-01-01

    Why do viruses sometimes not pass through larger pores in track-etch filters? Increasing the salinity (0.8 to 160 mM Na+) decreased φX174 and PRD1 passage through track-etch polycarbonate membranes (sodium dodecyl sulfate coated but not polyvinylpyrrolidone coated) and PRD1 passage through polyester membranes. Undiminished passage when 0.1% Tween 80 was added implied that nonionic virus adsorption occurred and indicated that high levels of salinity decreased virus passage by decreasing electrostatic repulsion that prevented adsorption. PMID:10347078

  10. Dietary fat modifies mitochondrial and plasma membrane apoptotic signaling in skeletal muscle of calorie-restricted mice.

    PubMed

    López-Domínguez, José Alberto; Khraiwesh, Husam; González-Reyes, José Antonio; López-Lluch, Guillermo; Navas, Plácido; Ramsey, Jon Jay; de Cabo, Rafael; Burón, María Isabel; Villalba, José M

    2013-12-01

    Calorie restriction decreases skeletal muscle apoptosis, and this phenomenon has been mechanistically linked to its protective action against sarcopenia of aging. Alterations in lipid composition of membranes have been related with the beneficial effects of calorie restriction. However, no study has been designed to date to elucidate if different dietary fat sources with calorie restriction modify apoptotic signaling in skeletal muscle. We show that a 6-month calorie restriction decreased the activity of the plasma membrane neutral sphingomyelinase, although caspase-8/10 activity was not altered, in young adult mice. Lipid hydroperoxides, Bax levels, and cytochrome c and AIF release/accumulation into the cytosol were also decreased, although caspase-9 activity was unchanged. No alterations in caspase-3 and apoptotic index (DNA fragmentation) were observed, but calorie restriction improved structural features of gastrocnemius fibers by increasing cross-sectional area and decreasing circularity of fibers in cross sections. Changing dietary fat with calorie restriction produced substantial alterations of apoptotic signaling. Fish oil augmented the protective effect of calorie restriction decreasing plasma membrane neutral sphingomyelinase, Bax levels, caspase-8/10, and -9 activities, while increasing levels of the antioxidant coenzyme Q at the plasma membrane, and potentiating the increase of cross-sectional area and the decrease of fiber circularity in cross sections. Many of these changes were not found when we used lard. Our data support that dietary fish oil with calorie restriction produces a cellular anti-apoptotic environment in skeletal muscle with a downregulation of components involved in the initial stages of apoptosis engagement, both at the plasma membrane and the mitochondria.

  11. Nanocharacterization and nanofabrication of a Nafion thin film in liquids by atomic force microscopy.

    PubMed

    Umemura, Kazuo; Wang, Tong; Hara, Masahiko; Kuroda, Reiko; Uchida, On; Nagai, Masayuki

    2006-03-28

    We demonstrated the nanocharacterization and nanofabrication of a Nafion thin film using atomic force microscopy (AFM). AFM images showed that the Nafion molecules form nanoclusters in water, in 5% methanol, and in acetic acid. Young's modulus E of a Nafion film was estimated by sequential force curve measurements in water and in 5% methanol on one sample surface. Ewater/E5% methanol was 1.75 +/- 0.40, so the film was much softer in 5% methanol than in water. Even when solvent was replaced from 5% methanol to water, Young's modulus was not recovered soon. We showed the first example of the mechanical properties of a Nafion film on the nanoscale. Furthermore, we succeeded in fabricating 3D nanostructures on a Nafion surface by AFM nanolithography in liquids. Our results showed the new potential of the AFM nanolithography of a polymer film by softening the molecules in liquids.

  12. Membranes of Polymers of Intrinsic Microporosity (PIM-1) Modified by Poly(ethylene glycol)

    PubMed Central

    Bengtson, Gisela; Neumann, Silvio; Filiz, Volkan

    2017-01-01

    Until now, the leading polymer of intrinsic microporosity PIM-1 has become quite famous for its high membrane permeability for many gases in gas separation, linked, however, to a rather moderate selectivity. The combination with the hydrophilic and low permeable poly(ethylene glycol) (PEG) and poly(ethylene oxides) (PEO) should on the one hand reduce permeability, while on the other hand enhance selectivity, especially for the polar gas CO2 by improving the hydrophilicity of the membranes. Four different paths to combine PIM-1 with PEG or poly(ethylene oxide) and poly(propylene oxide) (PPO) were studied: physically blending, quenching of polycondensation, synthesis of multiblock copolymers and synthesis of copolymers with PEO/PPO side chain. Blends and new, chemically linked polymers were successfully formed into free standing dense membranes and measured in single gas permeation of N2, O2, CO2 and CH4 by time lag method. As expected, permeability was lowered by any substantial addition of PEG/PEO/PPO regardless the manufacturing process and proportionally to the added amount. About 6 to 7 wt % of PEG/PEO/PPO added to PIM-1 halved permeability compared to PIM-1 membrane prepared under similar conditions. Consequently, selectivity from single gas measurements increased up to values of about 30 for CO2/N2 gas pair, a maximum of 18 for CO2/CH4 and 3.5 for O2/N2. PMID:28587247

  13. Long-alkane-chain modified N-phthaloyl chitosan membranes with controlled permeability.

    PubMed

    Chen, Chao; Tao, Shuming; Qiu, Xiaoyun; Ren, Xueqin; Hu, Shuwen

    2013-01-02

    A series of N-phthaloyl acylated chitosan membranes with controlled permeability were synthesized by the regioselective protection of the chitosan amino groups as the corresponding phthalimides followed by reaction with the long-chain dodecanoyl chloride. Fourier transform infrared (FT-IR) and (1)H nuclear magnetic resonance ((1)H NMR) analysis suggested that the degree of substitution (DS) ranged from 2.8 to 3.6. Contact angles, water retention values and mechanical examinations demonstrated that the hydrophobicity and mechanical properties of the membranes were all improved significantly following the modifications, together with their solubility in many organic solvents. Thermal weight change analysis demonstrated that a higher DS provided enhanced thermal properties. The controlled permeability of the membranes was determined by measuring the diffusion of urea, and the amount of urea released decreased significantly with increasing DS. The comprehensive properties of the membranes could be tuned by regulating their DS values as required. Copyright © 2012 Elsevier Ltd. All rights reserved.

  14. Concentration Dependence of VO2+ Crossover of Nafion for Vanadium Redox Flow Batteries

    SciTech Connect

    Lawton, Jamie; Jones, Amanda; Zawodzinski, Thomas A

    2013-01-01

    The VO2+ crossover, or permeability, through Nafion in a vanadium redox flow battery (VRFB) was monitored as a function of sulfuric acid concentration and VO2+ concentration. A vanadium rich solution was flowed on one side of the membrane through a flow field while symmetrically on the other side a blank or vanadium deficit solution was flowed. The blank solution was flowed through an electron paramagnetic resonance (EPR) cavity and the VO2+ concentration was determined from the intensity of the EPR signal. Concentration values were fit using a solution of Fick s law that allows for the effect of concentration change on the vanadium rich side. The fits resulted in permeability values of VO2+ ions across the membrane. Viscosity measurements of many VO2+ and H2SO4 solutions were made at 30 60 C. These viscosity values were then used to determine the effect of the viscosity of the flowing solution on the permeability of the ion. 2013 The Electrochemical Society. [DOI: 10.1149/2.004306jes] All rights reserved.

  15. PVDF-Nafion nanomembranes coated microneedles for in vivo transcutaneous implantable glucose sensing.

    PubMed

    Chen, Dajing; Wang, Cang; Chen, Wei; Chen, Yuquan; Zhang, John X J

    2015-12-15

    We demonstrate that microporous PVDF membranes sandwiched between multiple layers of nanomaterials can be used for continuous monitoring of glucose level in vivo. This is achieved by coating needle electrodes with Polyaniline nanofiber, Platinum nanoparticles, glucose oxidase enzyme and porous layers, successfully fabricated with layer-by-layer deposition. Nanoparticles incorporated into conductive Polyaniline nanofibers resulted in high surface to volume ratio and electrocatalytic activity for glucose enzyme. A composite coating membrane of porous PVDF and nano-sphere Nafion limited the glucose transportation and increased the lifetime of in vivo measurements. The glucose biosensor exhibited a sub-microamperometric output current, fast response time of less than 30s and a sensitivity of 0.23 μA/mM. The linear sensing range in terms of glucose concentration was from 0 to 20mM. Implantable experiments using mice models showed excellent response to the variation of blood glucose concentration while maintaining biocompatibility with the surrounding tissues. The sensitivity was shown to remain within 10% close to initial sensitivity within the 7 days of continuous monitoring, and maintain at 70% of the initial sensitivity within 21 days.

  16. [Modified technique of autologous transplantation of internal limiting membrane for macular hole].

    PubMed

    Hernández-da Mota, Sergio Eustolio; Béjar-Cornejo, Francisco

    Autologous internal limiting membrane transplantation has allowed some cases of macular holes refractory to conventional surgery techniques to be treated. The purpose of this study is to describe the anatomical and functional outcomes of a modification of this technique in a case series of naïve macular hole patients. A consecutive case series study was performed on patients with naïve macular holes with a diameter greater than 600 μ. Best corrected visual acuity, clinical features of the macular area, and optical coherence tomography were recorded before the operation and at the end of follow-up in all patients studied. All patients underwent 23 Ga core vitrectomy, posterior hyaloid separation, and brilliant-blue assisted internal limiting membrane peeling. A small piece of the internal limiting membrane was peeled off to make a free flap, and this was trasplanted and placed inside the macular hole under perfluorocarbon liquids. Air-fluid exchange was performed and SF6 gas was injected at a non-expansile concentration. The study included 5 eyes of 5 patients who underwent internal limiting membrane autograft. The mean age was 50.6 (SD 12.3) years. Four of the 5 cases had macular hole closure. The case where there was no closure of the macular hole was secondary to trauma. There was an improvement in visual acuity in all patients where the closing of the macular hole was achieved at the end of follow-up. In this cases series of macular hole patients, the autologous internal limiting membrane transplantation was associated with an anatomical closure of the macular hole and functional improvement in most of the patients studied. Copyright © 2016 Academia Mexicana de Cirugía A.C. Publicado por Masson Doyma México S.A. All rights reserved.

  17. Critical modifier role of membrane-CFTR dependent ceramide signaling in lung injury and emphysema

    PubMed Central

    Bodas, Manish; Min, Taehong; Mazur, Steven; Vij, Neeraj

    2010-01-01

    Ceramide accumulation mediates the pathogenesis of chronic obstructive lung diseases. Although, an association between lack of CFTR and ceramide accumulation has been described, it is unclear how membrane-CFTR may modulate ceramide signaling in lung injury and emphysema. The Cftr+/+- and Cftr−/−- mice and cells were used to evaluate the CFTR-dependent ceramide signaling in lung injury. Lung tissue from control and COPD patients was used to verify the role of CFTR-dependent ceramide signaling in pathogenesis of chronic emphysema. Our data reveals a novel finding that CFTR expression inversely correlates with severity of emphysema and ceramide-accumulation in COPD subjects compared to controls. We found that chemical inhibition of de novo- ceramide-synthesis controls Pa-LPS induced lung injury in Cftr+/+-mice, while its efficacy was significantly lower in Cftr−/−-mice indicating that membrane-CFTR is required for controlling lipid-raft ceramide levels. Inhibition of membrane-ceramide release showed enhanced protective effect in controlling Pa-LPS induced lung injury in Cftr−/−- mice as compared to the Cftr+/+, confirming our observation that CFTR regulates lipid-raft ceramide- levels and signaling. Our results indicate that inhibition of de novo- ceramide-synthesis may be effective in disease states with low-CFTR expression like emphysema and chronic lung injury but not in complete absence of lipid-raft CFTR as in ΔF508-CF. In contrast, inhibiting membrane ceramide release has the potential of a more effective drug candidate for ΔF508-CF but may not be effectual in treating lung injury and emphysema. Our data demonstrates the critical role of membrane-localized CFTR in regulating ceramide-accumulation and inflammatory-signaling in lung injury and emphysema. PMID:21135173

  18. Transparent, mediator- and membrane-free enzymatic fuel cell based on nanostructured chemically modified indium tin oxide electrodes.

    PubMed

    González-Arribas, Elena; Bobrowski, Tim; Di Bari, Chiara; Sliozberg, Kirill; Ludwig, Roland; Toscano, Miguel D; De Lacey, Antonio L; Pita, Marcos; Schuhmann, Wolfgang; Shleev, Sergey

    2017-11-15

    We detail a mediator- and membrane-free enzymatic glucose/oxygen biofuel cell based on transparent and nanostructured conducting supports. Chemically modified indium tin oxide nanoparticle modified electrodes were used to substantially increase the active surface area without significantly compromising transparency. Two different procedures for surface nanostructuring were employed, viz. spray-coating and drop-coating. The spray-coated biodevice showed superior characteristics as compared to the drop-coated enzymatic fuel cell, as a result of the higher nanostructured surface area as confirmed by electrochemical characterisation, as well as scanning electron and atomic force microscopy. Subsequent chemical modification with silanes, followed by the immobilisation of either cellobiose dehydrogenase from Corynascus thermophiles or bilirubin oxidase from Myrothecium verrucaria, were performed to obtain the bioanodes and biocathodes, respectively. The optimised biodevice exhibited an OCV of 0.67V and power output of up to 1.4µW/cm(2) at an operating voltage of 0.35V. This is considered a significant step forward in the field of glucose/oxygen membrane- and mediator-free, transparent enzymatic fuel cells. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Surface chemistry of grafted expanded poly(tetrafluoroethylene) membranes modifies the in vitro proinflammatory response in macrophages.

    PubMed

    Chandler-Temple, Adrienne; Kingshott, Peter; Wentrup-Byrne, Edeline; Cassady, A Ian; Grøndahl, Lisbeth

    2013-04-01

    A series of surface-modified expanded poly(tetrafluoroethylene) membranes showed varied levels of in vitro macrophage proinflammatory response. Membranes containing a mixture of phosphate and hydroxyl groups (as determined by X-ray photoelectron spectroscopy analysis) stimulate greater macrophage activation than samples containing a mixture of phosphate and carboxylic acid segments. The types of proteins that adsorbed irreversibly from serum onto the two samples with the highest and lowest cellular response were investigated using surface-matrix-assisted laser desorption ionisation time-of-flight mass spectrometry. Distinct differences in the number and type of proteins that adsorbed were observed between these samples. A correlation was found between the main protein components adsorbed onto the surfaces and the resulting in vitro proinflammatory response. This study strongly supports the hypothesis that the cellular response is not controlled directly by surface properties but is mediated by specific protein adsorption events. This in turn highlights the importance of better understanding and controlling the properties of intelligent surface-modified biomaterials.

  20. Cycling performance and efficiency of sulfonated poly(sulfone) membranes in vanadium redox flow batteries

    SciTech Connect

    Kim, Soowhan; Yan, Jingling; Schwenzer, Birgit; Zhang, Jianlu; Li, Liyu; Liu, Jun; Yang, Zhenguo; Hickner, Michael A.

    2010-11-30

    As an alternative to the expensive Nafion® ion exchange membrane, an inexpensive commercially-available Radel® polymer was sulfonated, fabricated into a thin membrane, and evaluated for its performance in a vanadium redox flow battery (VRFB). The sulfonated Radel (S-Radel) membrane showed almost an order of magnitude lower permeability of V (IV) ions (2.07×10-7 cm2/min), compared to Nafion 117 (1.29×10-6 cm2/min), resulting in better coulombic efficiency (~98% vs. 95% at 50 mA/cm2) and lower capacity loss per cycle. Even though the S-Radel membrane had slightly higher membrane resistance, the energy efficiency of the VRFB with the S-Radel membrane was comparable to that of Nafion due to its better coulombic efficiency. The S-Radel membrane exhibited good performance up to 40 cycles, but a decay in performance at later cycles was observed.

  1. Superacid-doped polybenzimidazole-decorated carbon nanotubes: a novel high-performance proton exchange nanocomposite membrane

    NASA Astrophysics Data System (ADS)

    Hasani-Sadrabadi, Mohammad Mahdi; Dashtimoghadam, Erfan; Majedi, Fatemeh Sadat; Moaddel, Homayoun; Bertsch, Arnaud; Renaud, Philippe

    2013-11-01

    Here we demonstrate design and electrochemical characterization of novel proton exchange membranes based on Nafion and superacid-doped polymer coated carbon nanotubes (CNTs). Polybenzimidazole-decorated CNT (PBI-CNT), a high-performance proton exchange nanostructure, was doped using phosphotungstic acid (PWA) as a super proton conductor. The engineered nanohybrid structure was shown to retain water molecules and provide high proton conduction at low humidity and elevated temperatures. The developed complex nanomaterial was then incorporated into the Nafion matrix to fabricate nanocomposite membranes. The acid-base interactions between imidazole groups of PBI and sulfonate groups of Nafion facilitate proton conductivity, especially at elevated temperatures. The improved characteristics of the membranes at the nanoscale result in enhanced fuel cell power generation capacity (386 mW cm-2) at elevated temperatures and low humidity (40% R.H.), which was found to be considerably higher than the commercial Nafion®117 membrane (73 mW cm-2).

  2. Large-Scale Membrane- and Lignin-Modified Adsorbent-Assisted Extraction and Preconcentration of Triazine Analogs and Aflatoxins.

    PubMed

    Hu, Shun-Wei; Chen, Shushi

    2017-04-11

    The large-scale simultaneous extraction and concentration of aqueous solutions of triazine analogs, and aflatoxins, through a hydrocarbon-based membrane (e.g., polyethylene, polyethylene/polypropylene copolymer) under ambient temperature and atmospheric pressure is reported. The subsequent adsorption of analyte in the extraction chamber over the lignin-modified silica gel facilitates the process by reducing the operating time. The maximum adsorption capacity values for triazine analogs and aflatoxins are mainly adsorption mechanism-dependent and were calculated to be 0.432 and 0.297 mg/10 mg, respectively. The permeation, and therefore the percentage of analyte extracted, ranges from 1% to almost 100%, and varies among the solvents examined. It is considered to be vapor pressure- and chemical polarity-dependent, and is thus highly affected by the nature and thickness of the membrane, the discrepancy in the solubility values of the analyte between the two liquid phases, and the amount of adsorbent used in the process. A dependence on the size of the analyte was observed in the adsorption capacity measurement, but not in the extraction process. The theoretical interaction simulation and FTIR data show that the planar aflatoxin molecule releases much more energy when facing toward the membrane molecule when approaching it, and the mechanism leading to the adsorption.

  3. Promising monolayer membranes for CO2/N2/CH4 separation: Graphdiynes modified respectively with hydrogen, fluorine, and oxygen atoms

    NASA Astrophysics Data System (ADS)

    Zhao, Lianming; Sang, Pengpeng; Guo, Sheng; Liu, Xiuping; Li, Jing; Zhu, Houyu; Guo, Wenyue

    2017-05-01

    Three graphdiyne-like monolayers were designed by substituting one-third diacetylenic linkages with heteroatoms hydrogen, fluorine, and oxygen (GDY_X, X = H, F, and O), respectively. The CO2/N2/CH4 separation performance of the designed graphdiyne-like monolayers was investigated by using both first-principle density functional theory (DFT) and molecular dynamic (MD) simulations. The stabilities of GDY_X monolayers were confirmed by the calculated cohesive energies and phonon dispersion spectra. Both the DFT and MD calculations demonstrated that although the GDY_H membrane has poor selectivity for CO2/N2/CH4 gases, the GDY_F and GDY_O membranes can excellently separate CO2 and N2 from CH4 in a wide temperature range. Moreover, the CO2/N2 mixture can be effectively separated by GDY_O at temperatures lower than 300 K. Based on the kinetic theory, extremely high permeances were found for CO2 and N2 passing through the GDY_X membranes (10-4-10-2 mol/m2 s Pa at 298 K). In addition, the influence of relative concentration on selectivity was also investigated for gases in the binary mixtures. This work provides an effective way to modify graphdiyne for the separation of large molecular gases, which is quite crucial in the gas separation industry.

  4. Wastewater from wood and pulp industry treated by combination of coagulation, adsorption on modified clinoptilolite tuff and membrane processes.

    PubMed

    Bennani, Yasmina; Kosutić, Kresimir; Drazević, Emil; Rozeć, Mirela

    2012-06-01

    Wastewater from the wood and pulp industry is of environmental concern. It contains high concentrations of organic and inorganic matter. In this work a combined method of coagulation, adsorption and nanofiltration/reverse osmosis (NF/RO) was investigated in the purification of biologically treated wastewater from wood processing. Coagulation with 0.8 g dm(-3) AlCl3 x 6H2O and adsorption on 2.5 g m(-3) modified clinoptilolite tuff resulted in removal efficiencies of total carbon (TC), total organic carbon (TOC) and inorganic carbon (IC) up to 67.1%, 77.4% and 49.5%, respectively. Almost complete removal of solutes was achieved after NF/RO treatment. The TOC removal efficiency with RO membrane (CPA-3, LFC-1, XLE) and tight NF membrane (NF90) was 98% and with highly porous NF membrane (DK), 88%. After the proposed treatment the purified water stream can be recycled into the process or safely disposed to the river.

  5. Large-Scale Membrane- and Lignin-Modified Adsorbent-Assisted Extraction and Preconcentration of Triazine Analogs and Aflatoxins

    PubMed Central

    Hu, Shun-Wei; Chen, Shushi

    2017-01-01

    The large-scale simultaneous extraction and concentration of aqueous solutions of triazine analogs, and aflatoxins, through a hydrocarbon-based membrane (e.g., polyethylene, polyethylene/polypropylene copolymer) under ambient temperature and atmospheric pressure is reported. The subsequent adsorption of analyte in the extraction chamber over the lignin-modified silica gel facilitates the process by reducing the operating time. The maximum adsorption capacity values for triazine analogs and aflatoxins are mainly adsorption mechanism-dependent and were calculated to be 0.432 and 0.297 mg/10 mg, respectively. The permeation, and therefore the percentage of analyte extracted, ranges from 1% to almost 100%, and varies among the solvents examined. It is considered to be vapor pressure- and chemical polarity-dependent, and is thus highly affected by the nature and thickness of the membrane, the discrepancy in the solubility values of the analyte between the two liquid phases, and the amount of adsorbent used in the process. A dependence on the size of the analyte was observed in the adsorption capacity measurement, but not in the extraction process. The theoretical interaction simulation and FTIR data show that the planar aflatoxin molecule releases much more energy when facing toward the membrane molecule when approaching it, and the mechanism leading to the adsorption. PMID:28398252

  6. Electrochemical Membrane Reactors for Sustainable Chlorine Recycling

    PubMed Central

    Vidakovic-Koch, Tanja; Martinez, Isai Gonzalez; Kuwertz, Rafael; Kunz, Ulrich; Turek, Thomas; Sundmacher, Kai

    2012-01-01

    Polymer electrolyte membranes have found broad application in a number of processes, being fuel cells, due to energy concerns, the main focus of the scientific community worldwide. Relatively little attention has been paid to the use of these materials in electrochemical production and separation processes. In this review, we put emphasis upon the application of Nafion membranes in electrochemical membrane reactors for chlorine recycling. The performance of such electrochemical reactors can be influenced by a number of factors including the properties of the membrane, which play an important role in reactor optimization. This review discusses the role of Nafion as a membrane, as well as its importance in the catalyst layer for the formation of the so-called three-phase boundary. The influence of an equilibrated medium on the Nafion proton conductivity and Cl− crossover, as well as the influence of the catalyst ink dispersion medium on the Nafion/catalyst self-assembly and its importance for the formation of an ionic conducting network in the catalyst layer are summarized. PMID:24958294

  7. Electrotransportation of aniline through a perfluorosulfonate ion-exchange membrane

    SciTech Connect

    Katakura, Katsumi . Dept. of Chemical Engineering); Inaba, Minoru; Toyama, Koji; Ogumi, Zempachi; Takehara, Zenichiro . Division of Energy and Hydrocarbon Chemistry)

    1994-07-01

    Transport phenomena of aniline through Na[sup +]-, K[sup +]-, and Cs[sup +]-form of a perfluorosulfonate ion-exchange membrane, Nafion 117, under a flow of dc current, electrotransportation, were investigated. In each form, an increase in transport number of anilinium cation was observed in the current density range from 0.3 to 1.3 mA cm[sup [minus]2]. The transport number of the anilinium cation in Cs[sup +]-form was larger than that expected from the concentration and diffusion coefficient of the anilinium cation in Cs[sup +]-form Nafion. These aniline transport phenomena may be attributable to a structural change of Nafion or a decrease in hydrophobic interaction between the anilinium cation and Nafion caused by the flow of dc current.

  8. Synthesis of indium sulphide quantum dots in perfluoronated ionomer membrane

    SciTech Connect

    Sumi, R.; Warrier, Anita R.; Vijayan, C.

    2014-01-28

    In this paper, we demonstrate a simple and efficient method for synthesis of β-indium sulphide (In{sub 2}S{sub 3}) nanoparticles embedded in an ionomer matrix (nafion membrane). The influence of reaction temperature on structural, compositional and optical properties of these films were analysed using X-Ray Diffraction, EDAX, UV-Vis absorption spectroscopy and photoluminescence studies. Average particle diameter was estimated using modified effective mass approximation method. Absorption spectra of In{sub 2}S{sub 3} nanoparticles show blue shift compared to bulk In{sub 2}S{sub 3}, indicating strong quantum size confinement effects. PL emission in the wavelength range 530–600 nm was recorded using a 488 nm line from an Ar{sup +} laser as the excitation source.

  9. Synthesis of indium sulphide quantum dots in perfluoronated ionomer membrane

    NASA Astrophysics Data System (ADS)

    Sumi, R.; Warrier, Anita R.; Vijayan, C.

    2014-01-01

    In this paper, we demonstrate a simple and efficient method for synthesis of β-indium sulphide (In2S3) nanoparticles embedded in an ionomer matrix (nafion membrane). The influence of reaction temperature on structural, compositional and optical properties of these films were analysed using X-Ray Diffraction, EDAX, UV-Vis absorption spectroscopy and photoluminescence studies. Average particle diameter was estimated using modified effective mass approximation method. Absorption spectra of In2S3 nanoparticles show blue shift compared to bulk In2S3, indicating strong quantum size confinement effects. PL emission in the wavelength range 530-600 nm was recorded using a 488 nm line from an Ar+ laser as the excitation source.

  10. Hydrophilic poly(vinylidene fluoride) porous membrane with well connected ion transport networks for vanadium flow battery

    NASA Astrophysics Data System (ADS)

    Cao, Jingyu; Yuan, Zhizhang; Li, Xianfeng; Xu, Wanxing; Zhang, Huamin

    2015-12-01

    Hydrophilic poly(vinylidene fluoride) (PVDF) porous membranes are facilely fabricated via grafting polymerization and cross-linking reaction for vanadium flow battery (VFB) application. A solvent swelling pre-treatment is specifically carried out to introduce hydrophilic groups in the pores and on the surface, where they can form well connected ion transport networks. The modification is performed through chemical cross-linking and grafting of PVP by using potassium persulfate (K2S2O8) as a radical initiator. The effect of reaction condition on membrane morphology, hydrophilicity is characterized in detail. Meanwhile, the performance of modified membranes is detected in VFB single cell at a current density of 80 mA cm-2. It is found that more PVP is immobilized on membrane surface and in the pores with prolonging reaction time. Consequently, the membrane wetability and effective pore size change dramatically, resulting better hydrophilicity and higher ion selectivity. As a result, the VFBs assembled with these modified membranes show higher CE and overall better EE than unmodified ones. The optimized membrane shows CE of 94.4% and EE of 83.3%, which is comparable to commercial Nafion 115. Furthermore, the prepared hydrophilic PVDF membranes demonstrate excellent chemical stability through the long-term battery operation, showing great prospects in VFB applications.

  11. Direct power production from a water salinity difference in a membrane-modified supercapacitor flow cell.

    PubMed

    Sales, B B; Saakes, M; Post, J W; Buisman, C J N; Biesheuvel, P M; Hamelers, H V M

    2010-07-15

    The entropy increase of mixing two solutions of different salt concentrations can be harnessed to generate electrical energy. Worldwide, the potential of this resource, the controlled mixing of river and seawater, is enormous, but existing conversion technologies are still complex and expensive. Here we present a small-scale device that directly generates electrical power from the sequential flow of fresh and saline water, without the need for auxiliary processes or converters. The device consists of a sandwich of porous "supercapacitor" electrodes, ion-exchange membranes, and a spacer and can be further miniaturized or scaled-out. Our results demonstrate that alternating the flow of saline and fresh water through a capacitive cell allows direct autogeneration of voltage and current and consequently leads to power generation. Theoretical calculations aid in providing directions for further optimization of the properties of membranes and electrodes.

  12. Modulating molecular transport across peptide-modified nanoporous alumina membranes with light

    NASA Astrophysics Data System (ADS)

    Kumeria, Tushar; Yu, Jingxian; Alsawat, Mohammed; Kurkuri, Mahaveer D.; Santos, Abel; Abell, Andrew D.; Losic, Dusan

    2016-12-01

    We designed and fabricated a smart and stimuli responsive membrane to cater on demand molecular transporting applications. A novel photoswitchable peptide (PSP) was synthesized and attached inside nanoporous anodic alumina membranes (NAAMs) pores. The PSP specifically switched between its cis and trans photostationary states on exposure to 364 nm and 440 nm wavelength lights respectively, which not only provided the ability to control its pore diameter but also the surface chemistry. The switchable molecular transport properties of the PSP-NAAMs have been shown as a function of the light exposure. Most importantly, the molecular transport across PSP-NAAMs could be repeatedly switched between on and off state, which is highly significant for on-demand triggered drug release systems.

  13. Promotion of initial anti-tumor effect via polydopamine modified doxorubicin-loaded electrospun fibrous membranes

    PubMed Central

    Yuan, Ziming; Zhao, Xin; Wang, Xiaohu; Qiu, Wangwang; Chen, Xinliang; Zheng, Qi; Cui, Wenguo

    2014-01-01

    Drug-loaded electrospun PLLA membranes are not conducive to adhesion between materials and tissues due to the strong hydrophobicity of PLLA, which possibly attenuate the drugs’ effect loaded on the materials. In the present work, we developed a facile method to improve the hydrophilicity of doxorubicin (DOX)-loaded electrospun PLLA fibrous membranes, which could enhance the anti-tumor effect at the early stage after implantation. A mussel protein, polydopamine (PDA), could be easily grafted on the surface of hydrophobic DOX-loaded electrospun PLLA membranes (PLLA-DOX/pDA) in water solution. The morphology analysis of PLLA-DOX/pDA fibers displayed that though the fiber diameter was slightly swollen, they still maintained a 3D fibrous structure, and the XPS analysis certified that pDA had successfully been grafted onto the surface of the fibers. The results of surface wettability analysis showed that the contact angle decreased from 136.7° to 0° after grafting. In vitro MTT assay showed that the cytotoxicity of PLLA-DOX/pDA fibers was the strongest, and the stereologic cell counting assay demonstrated that the adhesiveness of PLLA/pDA fiber was significantly better than PLLA fiber. In vivo tumor-bearing mice displayed that, after one week of implantation, the tumor apoptosis and necrosis of PLLA-DOX/pDA fibers were the most obvious from histopathology and TUNEL assay. The caspase-3 activity of PLLA-DOX/pDA group was the highest using biochemical techniques, and the Bax: Bcl-2 ratio increased significantly in PLLA-DOX/pDA group through qRT-PCR analysis. All the results demonstrated that pDA can improve the affinity of the electrospun PLLA membranes and enhance the drug effect on tumors. PMID:25337186

  14. Promotion of initial anti-tumor effect via polydopamine modified doxorubicin-loaded electrospun fibrous membranes.

    PubMed

    Yuan, Ziming; Zhao, Xin; Wang, Xiaohu; Qiu, Wangwang; Chen, Xinliang; Zheng, Qi; Cui, Wenguo

    2014-01-01

    Drug-loaded electrospun PLLA membranes are not conducive to adhesion between materials and tissues due to the strong hydrophobicity of PLLA, which possibly attenuate the drugs' effect loaded on the materials. In the present work, we developed a facile method to improve the hydrophilicity of doxorubicin (DOX)-loaded electrospun PLLA fibrous membranes, which could enhance the anti-tumor effect at the early stage after implantation. A mussel protein, polydopamine (PDA), could be easily grafted on the surface of hydrophobic DOX-loaded electrospun PLLA membranes (PLLA-DOX/pDA) in water solution. The morphology analysis of PLLA-DOX/pDA fibers displayed that though the fiber diameter was slightly swollen, they still maintained a 3D fibrous structure, and the XPS analysis certified that pDA had successfully been grafted onto the surface of the fibers. The results of surface wettability analysis showed that the contact angle decreased from 136.7° to 0° after grafting. In vitro MTT assay showed that the cytotoxicity of PLLA-DOX/pDA fibers was the strongest, and the stereologic cell counting assay demonstrated that the adhesiveness of PLLA/pDA fiber was significantly better than PLLA fiber. In vivo tumor-bearing mice displayed that, after one week of implantation, the tumor apoptosis and necrosis of PLLA-DOX/pDA fibers were the most obvious from histopathology and TUNEL assay. The caspase-3 activity of PLLA-DOX/pDA group was the highest using biochemical techniques, and the Bax: Bcl-2 ratio increased significantly in PLLA-DOX/pDA group through qRT-PCR analysis. All the results demonstrated that pDA can improve the affinity of the electrospun PLLA membranes and enhance the drug effect on tumors.

  15. Antiscaling efficacy of CaCO3 and CaSO4 on polyethylene glycol (PEG)-modified reverse osmosis membranes in the presence of humic acid: interplay of membrane surface properties and water chemistry.

    PubMed

    Ray, Jessica R; Wong, Whitney; Jun, Young-Shin

    2017-02-15

    Mineral scaling persists in many water treatment processes. More specifically, it can significantly reduce the efficacy of aromatic polyamide (PA) membranes during reverse osmosis (RO) water treatment. Previous studies have integrated hydrophilic materials, such as polyethylene glycol (PEG), onto RO membranes to combat scaling from generally hydrophobic feed water constituents; however, there are still outstanding knowledge gaps regarding the interplay of the modified membrane surface chemistry and the water chemistry in complex RO feed waters. In this work, we have investigated the mechanisms of hydrophilic PEG-grafted PA membranes in reducing mineral scaling from calcium carbonate (CaCO3) and calcium sulfate (CaSO4) in the presence of humic acid (HA). Based on surface and solution analyses, we found that colloidal formation was significantly reduced on PA-PEG surfaces in systems without HA. When HA was introduced, CaCO3 scaling was reduced on both virgin and PA-PEG membrane surfaces; while, interestingly, synergistic PEG-HA-CaSO4 interactions increased CaSO4 colloidal formation on PA-PEG membranes. Promoted CaSO4 formation results from a high negative surface charge near the PEG-modified membrane surface when HA and SO4(2-) are present, attracting more Ca(2+) to form CaSO4. The results of this work provide new information about colloidal formation at water-membrane interfaces for designing better PEG and PEG-based scale-resistant desalination membranes.

  16. Gadolinium modifies the cell membrane to inhibit permeabilization by nanosecond electric pulses

    PubMed Central

    Gianulis, Elena C.; Pakhomov, Andrei G.

    2015-01-01

    Lanthanide ions are the only known blockers of permeabilization by electric pulses of nanosecond duration (nsEP), but the underlying mechanisms are unknown. We employed timed applications of Gd3+ before or after nsEP (600-ns, 20 kV/cm) to investigate the mechanism of inhibition, and measured the uptake of the membrane-impermeable YO-PRO-1 (YP) and propidium (Pr) dyes. Gd3+ inhibited dye uptake in a concentration-dependent manner. The inhibition of Pr uptake was always about 2-fold stronger. Gd3+ was effective when added after nsEP, as well as when it was present during nsEP exposure and removed afterwards. Pores formed by nsEP in the presence of Gd3+ remained quiescent unless Gd3+ was promptly washed away. Such pores resealed (or shrunk) shortly after the wash despite the absence of Gd3+. Finally, a brief (3 s) Gd3+ perfusion was equally potent at inhibiting dye uptake when performed either immediately before or after nsEP, or early before nsEP. The persistent protective effect of Gd3+ even in its absence proves that inhibition by Gd3+ does not result from simple pore obstruction. Instead, Gd3+ causes lasting modification of the membrane, occurring promptly and irrespective of pore presence; it makes the membrane less prone to permeabilization and/or reduces the stability of electropores. PMID:25707556

  17. A molecule-imprinted polyaniline membrane modified on carbon fiber for detection of glycine.

    PubMed

    Zeng, Hongjuan; Wang, Deshun; Yu, Junsheng

    2014-01-01

    A layer of L-glycine-molecule-imprinted polyaniline (LMIP-PANI) polymer film has been modified on a carbon fiber electrode for the determination of L-glycine standard samples and L-glycine in cerebrospinal fluid of wistar mice. It has been found that a linear relationship exists between current and concentration for the glycine standard samples in the range of 0-12 μM by using the LMIP-PANI-modified carbon fiber electrode as a sensor. However, there is no any relationship between current and concentration for the carbon fiber electrode modified with no-glycine-molecule-imprinted polyaniline (NIP-PANI). The MIP-PANI- and NIP-PANI-modified carbon fiber films have been characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemistry methods. The investigation shows that the MIP-PANI-imprinted carbon fiber electrode will have a potential application in in-situ monitoring neurotransmitter due to its easy fabrication, low cost, bio-compatibility and flexibility.

  18. Non-platinum cathode catalyst layer composition for single Membrane Electrode Assembly Proton Exchange Membrane Fuel Cell

    NASA Astrophysics Data System (ADS)

    Olson, Tim S.; Chapman, Kate; Atanassov, Plamen

    The performance of nano-structured templated non-platinum-based cathode electrocatalysts for proton exchange membrane fuel cells (PEMFC) was evaluated for different catalyst layer compositions. The effect of non-platinum catalyst, Nafion, and 35 wt% Teflon modified Vulcan XC-72 Carbon Blacks (XC-35) loadings were measured under H 2/air and H 2/O 2 conditions. Transport hindrances that occur in the catalyst layers are evaluated with Δ E vs. i analysis. It is shown that transport limitations in the cathode catalyst layer can limit the performance of the cell at relatively low current densities if the catalyst layer composition is not optimized. Further, a procedure is outlined here to aid in the implementation of non-traditional catalyst materials into fuel cell systems (i.e. templated electrocatalyst as compared to the standard supported material).

  19. Nonhumidified High-Temperature Membranes Developed for Proton Exchange Membrane Fuel Cells

    NASA Technical Reports Server (NTRS)

    Kinder, James D.

    2005-01-01

    Fuel cells are being considered for a wide variety of aerospace applications. One of the most versatile types of fuel cells is the proton-exchange-membrane (PEM) fuel cell. PEM fuel cells can be easily scaled to meet the power and space requirements of a specific application. For example, small 100-W PEM fuel cells are being considered for personal power for extravehicular activity suit applications, whereas larger PEM fuel cells are being designed for primary power in airplanes and in uninhabited air vehicles. Typically, PEM fuel cells operate at temperatures up to 80 C. To increase the efficiency and power density of the fuel cell system, researchers are pursuing methods to extend the operating temperature of the PEM fuel cell to 180 C. The most widely used membranes in PEM fuel cells are Nafion 112 and Nafion 117--sulfonated perfluorinated polyethers that were developed by DuPont. In addition to their relatively high cost, the properties of these membranes limit their use in a PEM fuel cell to around 80 C. The proton conductivity of Nafion membranes significantly decreases above 80 C because the membrane dehydrates. The useful operating range of Nafion-based PEM fuel cells can be extended to over 100 C if ancillary equipment, such as compressors and humidifiers, is added to maintain moisture levels within the membrane. However, the addition of these components reduces the power density and increases the complexity of the fuel cell system.

  20. Regulation of epithelial cell morphology and functions approaching to more in vivo-like by modifying polyethylene glycol on polysulfone membranes.

    PubMed

    Shen, Chong; Zhang, Guoliang; Meng, Qin

    2012-01-01

    Cytocompatibility is critically important in design of biomaterials for application in tissue engineering. However, the currently well-accepted "cytocompatible" biomaterials are those which promote cells to sustain good attachment/spreading. The cells on such materials usually lack the self-assembled cell morphology and high cell functions as in vivo. In our view, biomaterials that can promote the ability of cells to self-assemble and demonstrate cell-specific functions would be cytocompatible. This paper examined the interaction of polyethylene glycol (PEG) modified polysulfone (PSf) membranes with four epithelial cell types (primary liver cells, a liver tumor cell line, and two renal tubular cell lines). Our results show that PSf membranes modified with proper PEG promoted the aggregation of both liver and renal cells, but the liver cells more easily formed aggregates than the renal tubular cells. The culture on PEG-modified PSf membranes also enhanced cell-specific functions. In particular, the cells cultured on F127 membranes with the proper PEG content mimicked the in vivo ultrastructure of liver cells or renal tubules cells and displayed the highest cell functions. Gene expression data for adhesion proteins suggest that the PEG modification impaired cell-membrane interactions and increased cell-cell interactions, thus facilitating cell self-assembly. In conclusion, PEG-modified membrane could be a cytocompatible material which regulates the morphology and functions of epithelial cells in mimicking cell performance in vivo.

  1. Understanding the Effects of Compression and Constraints on Water Uptake of Fuel-Cell Membranes

    SciTech Connect

    Kusoglu, Ahmet; Kienitz, Brian L.; Weber, Adam Z.

    2011-01-01

    Accurate characterization of polymer-electrolyte fuel cells (PEFCs) requires understanding the impact of mechanical and electrochemical loads on cell components. An essential aspect of this relationship is the effect of compression on the polymer membrane?s water-uptake behavior and transport properties. However, there is limited information on the impact of physical constraints on membrane properties. In this paper, we investigate both theoretically and experimentally how the water uptake of Nafion membrane changes under external compression loads. The swelling of a compressed membrane is modeled by modifying the swelling pressure in the polymer backbone which relies on the changes in the microscopic volume of the polymer. The model successfully predicts the water content of the compressed membrane measured through in-situ swelling-compression tests and neutron imaging. The results show that external mechanical loads could reduce the water content and conductivity of the membrane, especially at lower temperatures, higher humidities, and in liquid water. The modeling framework and experimental data provide valuable insight for the swelling and conductivity of constrained and compressed membranes, which are of interest in electrochemical devices such as batteries and fuel cells.

  2. [Membrane transfer-based colorimetric DNA detection using enzyme modified gold nanoparticles].

    PubMed

    Li, Haiyan; Jing, Fengxiang; Gao, Qiuyue; Jia, Chunping; Chen, Jiwu; Jin, Qinghui; Zhao, Jianlong

    2010-08-01

    We report here a novel membrane transfer-based DNA detection method, in which alkaline phosphatase labeled gold nanoparticle (AuNP) probes were used as a means to amplify the detection signal. In this method, the capture probe P1, complimentary to the 3' end of target DNA, was immobilized on the chip. The multi-component AuNP probes were prepared by co-coating AuNPs with the detecting probe P2, complimentary to the 5' end of target DNA, and two biotin-labeled signal probes (T10 and T40) with different lengths. In the presence of target DNA, DNA hybridization led to the attachment of AuNPs on the chip surface where specific DNA sequences were located in a "sandwich" format. Alkaline phosphatase was then introduced to the surface via biotine-streptavidin interaction. By using BCIP/NBT alkaline phosphatase color development kit, a colorimetric DNA detection was achieved through membrane transfer. The signal on the membrane was then detected by the naked eye or an ordinary optical scanner. The method provided a detection of limit of 1 pmol/L for synthesized target DNA and 0.23 pmol/L for PCR products of Mycobacterium tuberculosis 16S rDNA when the ratio of probes used was 9:1:1 (T10:T40:P2). The method described here has many desirable advantages including high sensitivity, simple operation, and no need of sophisticated equipment. The method can be potentially used for reliable biosensings.

  3. Radiation-Grafted Polymer Electrolyte Membranes for Water Electrolysis Cells: Evaluation of Key Membrane Properties.

    PubMed

    Albert, Albert; Barnett, Alejandro O; Thomassen, Magnus S; Schmidt, Thomas J; Gubler, Lorenz

    2015-10-14

    Radiation-grafted membranes can be considered an alternative to perfluorosulfonic acid (PFSA) membranes, such as Nafion, in a solid polymer electrolyte electrolyzer. Styrene, acrylonitrile, and 1,3-diisopropenylbenzene monomers are cografted into preirradiated 50 μm ethylene tetrafluoroethylene (ETFE) base film, followed by sulfonation to introduce proton exchange sites to the obtained grafted films. The incorporation of grafts throughout the thickness is demonstrated by scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) analysis of the membrane cross-sections. The membranes are analyzed in terms of grafting kinetics, ion-exchange capacity (IEC), and water uptake. The key properties of radiation-grafted membranes and Nafion, such as gas crossover, area resistance, and mechanical properties, are evaluated and compared. The plot of hydrogen crossover versus area resistance of the membranes results in a property map that indicates the target areas for membrane development for electrolyzer applications. Tensile tests are performed to assess the mechanical properties of the membranes. Finally, these three properties are combined to establish a figure of merit, which indicates that radiation-grafted membranes obtained in the present study are promising candidates with properties superior to those of Nafion membranes. A water electrolysis cell test is performed as proof of principle, including a comparison to a commercial membrane electrode assembly (MEA).

  4. Ordered mesoporous carbon/Nafion as a versatile and selective solid-phase microextraction coating.

    PubMed

    Zeng, Jingbin; Zhao, Cuiying; Chen, Jingjing; Subhan, Fazle; Luo, Liwen; Yu, Jianfeng; Cui, Bingwen; Xing, Wei; Chen, Xi; Yan, Zifeng

    2014-10-24

    In this study, ordered mesoporous carbon (OMC) with large surface area (1019m(2)g(-1)), uniform mesoporous structure (pore size distribution centering at 4.2nm) and large pore volume (1.46cm(3)g(-1)) was synthesized using 2D hexagonally mesoporous silica MSU-H as the hard template and sucrose as the carbon precursor. The as-synthesized OMC was immobilized onto a stainless steel wire using Nafion as a binder to prepare an OMC/Nafion solid-phase microextraction (SPME) coating. The extraction characteristics of the OMC/Nafion coating were extensively investigated using a wide range of analytes including non-polar (light petroleum and benzene homologues) and polar compounds (amines and phenols). The OMC/Nafion coating exhibited much better extraction efficiency towards all selected analytes than that of a multi-walled carbon nanotubes/Nafion coating with similar length and thickness, which is ascribed to its high surface area, well-ordered mesoporous structure and large pore volume. When the OMC/Nafion coating was used to extract a mixture containing various kinds of analytes, it possessed excellent extraction selectivity towards aromatic non-polar compounds. In addition, the feasibility of the OMC/Nafion coating for application in electrochemically enhanced SPME was demonstrated using protonated amines as model analytes.

  5. Plasma Modified Polypropylene Membranes as the Lithium-Ion Battery Separators

    NASA Astrophysics Data System (ADS)

    Wang, Zhengduo; Zhu, Huiqin; Yang, Lizhen; Wang, Xinwei; Liu, Zhongwei; Chen, Qiang

    2016-04-01

    To reduce the thermal shrinkage of the polymeric separators and improve the safety of the Li-ion batteries, plasma treatment and plasma enhanced vapor chemical deposition (PECVD) of SiOx-like are carried out on polypropylene (PP) separators, respectively. Critical parameters for separator properties, such as the thermal shrinkage rate, porosity, wettability, and mechanical strength, are evaluated on the plasma treated PP membranes. O2 plasma treatment is found to remarkably improve the wettability, porosity and electrolyte uptake. PECVD SiOx-like coatings are found to be able to effectively reduce the thermal shrinkage rate of the membranes and increase the ionic conductivity. The electrolyte-philicity of the SiOx-like coating surface can be tuned by the varying O2 content in the gas mixture during the deposition. Though still acceptable, the mechanical strength is reduced after PECVD, which is due to the plasma etching. supported by National Natural Science Foundation of China (Nos. 11175024, 11375031), the Beijing Institute of Graphic and Communication Key Project of China (No. 23190113051), the Shenzhen Science and Technology Innovation Committee of China (No. JCYJ20130329181509637), BJNSFC (No. KZ201510015014), and the State Key Laboratory of Electrical Insulation and Power Equipment of China (No. EIPE15208)

  6. Polymer electrolyte membrane resistance model

    NASA Astrophysics Data System (ADS)

    Renganathan, Sindhuja; Guo, Qingzhi; Sethuraman, Vijay A.; Weidner, John W.; White, Ralph E.

    A model and an analytical solution for the model are presented for the resistance of the polymer electrolyte membrane of a H 2/O 2 fuel cell. The solution includes the effect of the humidity of the inlet gases and the gas pressure at the anode and the cathode on the membrane resistance. The accuracy of the solution is verified by comparison with experimental data. The experiments were carried out with a Nafion 112 membrane in a homemade fuel cell test station. The membrane resistances predicted by the model agree well with those obtained during the experiments.

  7. Characterization of vanadium ion uptake in sulfonated diels alder poly(phenylene) membranes

    DOE PAGES

    Lawton, Jamie; Jones, Amanda; Tang, Zhijiang; ...

    2015-11-28

    Sulfonated diels alder poly(phenylene) (SDAPP), alternative aromatic hydrocarbon membranes for vanadium redox flow batteries (VRFBs) are characterized using electron paramagnetic resonance (EPR). Membranes soaked in sulfuric acid and vanadyl sulfate are analyzed to determine the membrane environment in which the vanadyl ion (VO2+) diffuses in the membranes. These results are compared to Nafion 117 membranes. In contrast to Nafion, the VO2+ in SDAPP membranes exists in two different environments. The results of analysis of rotational diffusion determined from fits the EPR spectral lineshapes in comparison with previously reported permeation studies and measurements of partitioning functions reported here suggest that themore » diffusion pathways in SDAPP are very different than in Nafion.« less

  8. Characterization of vanadium ion uptake in sulfonated diels alder poly(phenylene) membranes

    SciTech Connect

    Lawton, Jamie; Jones, Amanda; Tang, Zhijiang; Lindsey, Melanie; Zawodzinski, Thomas A

    2015-11-28

    Sulfonated diels alder poly(phenylene) (SDAPP), alternative aromatic hydrocarbon membranes for vanadium redox flow batteries (VRFBs) are characterized using electron paramagnetic resonance (EPR). Membranes soaked in sulfuric acid and vanadyl sulfate are analyzed to determine the membrane environment in which the vanadyl ion (VO2+) diffuses in the membranes. These results are compared to Nafion 117 membranes. In contrast to Nafion, the VO2+ in SDAPP membranes exists in two different environments. The results of analysis of rotational diffusion determined from fits the EPR spectral lineshapes in comparison with previously reported permeation studies and measurements of partitioning functions reported here suggest that the diffusion pathways in SDAPP are very different than in Nafion.

  9. Fabrication of a nanosize-Pt-embedded membrane electrode assembly to enhance the utilization of Pt in proton exchange membrane fuel cells.

    PubMed

    Choe, Junseok; Kim, Doyoung; Shim, Jinyong; Lee, Inhae; Tak, Yongsug

    2011-08-01

    A procedure to locate the Pt nanostructure inside the hydrophilic channel of a Nafion membrane was developed in order to enhance Pt utilization in PEMFCs. Nanosize Pt-embedded MEA was constructed by Cu electroless plating and subsequent Pt electrodeposition inside the hydrophilic channels of the Nafion membrane. The metallic Pt nanostructure fabricated inside the membrane was employed as an oxygen reduction catalyst for a PEMFC and facilitated effective use of the hydrophilic channels inside the membrane. Compared to the conventional MEA, a Pt-e