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R Faure - One of the best experts on this subject based on the ideXlab platform.
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understanding co stripping mechanism from niupd pt 110 in view of the measured Nickel formal partial charge number upon underpotential deposition on platinum surfaces in sulphate media
Electrochimica Acta, 2007Co-Authors: Marian Chatenet, Yvonne Soldoolivier, Eric Chainet, R FaureAbstract:Abstract We recently showed Nickel-underpotential deposition (Ni-UPD) occurs on polycrystalline or single crystal platinum electrodes in acidic media. Whereas the decoupling of the Nickel and hydrogen adsorption/desorption peaks is difficult for low pH, these processes can be better separated for higher pH values, typically pH > 3. However, even for platinum single crystals, high pH solutions do not enable to sufficiently separate Nickel from hydrogen phenomena. As a result, electrochemistry alone cannot yield important information about Ni-UPD, such as the formal partial charge number (valency of electrosorption) and the role of the sulphate or hydrogen sulphate anions. So, we decided to couple cyclic voltammetry to electrochemical quartz crystal microbalance (EQCM). EQCM measurements enable to decorrelate the simultaneous hydrogen and Nickel adsorption/desorption peaks, which we could not attempt solely with electrochemistry. The coupling between gravimetric and electrochemical measurements allows us to detect the contribution of the anions and thus to isolate that of Nickel: Nickel coverage can then be determined. Nearly 4/5 Ni UPD monolayer ( θ Ni ≈ 0.8) over platinum is reached at Nickel equilibrium potential for high pH solutions (5.5). The QCM and electrochemistry coupling further allows the determination of Nickel formal partial charge number: ι Ni,EQCM = 1.3 ± 0.13. Direct electrochemistry measurements (Swathirajan and Bruckenstein method) yield: ι Ni,Pt(poly) = 1.5 ± 0.17. These two values are close, which validates the electrochemical method for the Nickel/platinum system. In consequence, we used Swathirajan and Bruckenstein method for Pt(1 1 0)-(1 × 2) crystal and found: ι Ni,Pt(1 1 0) ≈ 1.4 ± 0.1. Whatever the system (Ni UPD /Pt(poly) or Ni UPD /Pt(1 1 0)-(1 × 2)) or the experimental technique, Nickel formal partial charge number is lower than Nickel Cation charge: ι Ni z Ni = 2. In consequence, upon underpotential deposition on platinum surfaces, Nickel Cations discharge and then undergo additional charge exchange processes, such as anion (or water) adsorption, resulting in apparent partial Nickel Cation discharge. Moreover, Ni UPD /Pt(1 1 0) surface displays high activity towards CO ad oxidation reaction. We explain such positive effect by the possible existence of a bifunctional mechanism in which oxygenated-species-covered Ni UPD adatoms provide the oxygen atom to CO ad ⋯Pt species, enabling its facile oxidation.
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Understanding CO-stripping mechanism from NiUPD/Pt(1 1 0) in view of the measured Nickel formal partial charge number upon underpotential deposition on platinum surfaces in sulphate media
Electrochimica Acta, 2007Co-Authors: Marian Chatenet, Eric Chainet, Yvonne Soldo-olivier, R FaureAbstract:We recently showed Nickel-underpotential deposition (Ni-UPD) occurs on polycrystalline or single crystal platinum electrodes in acidic media. Whereas the decoupling of the Nickel and hydrogen adsorption/desorption peaks is difficult for low pH, these processes can be better separated for higher pH values, typically pH > 3. However, even for platinum single crystals, high pH solutions do not enable to sufficiently separate Nickel from hydrogen phenomena. As a result, electrochemistry alone cannot yield important information about Ni-UPD, such as the formal partial charge number (valency of electrosorption) and the role of the sulphate or hydrogen sulphate anions. So, we decided to couple cyclic voltammetry to electrochemical quartz crystal microbalance (EQCM). EQCM measurements enable to decorrelate the simultaneous hydrogen and Nickel adsorption/desorption peaks, which we could not attempt solely with electrochemistry. The coupling between gravimetric and electrochemical measurements allows us to detect the contribution of the anions and thus to isolate that of Nickel: Nickel coverage can then be determined. Nearly 4/5 NiUPD monolayer (θNi ≈ 0.8) over platinum is reached at Nickel equilibrium potential for high pH solutions (5.5). The QCM and electrochemistry coupling further allows the determination of Nickel formal partial charge number: ιNi,EQCM = 1.3 ± 0.13. Direct electrochemistry measurements (Swathirajan and Bruckenstein method) yield: ιNi,Pt(poly) = 1.5 ± 0.17. These two values are close, which validates the electrochemical method for the Nickel/platinum system. In consequence, we used Swathirajan and Bruckenstein method for Pt(1 1 0)-(1 × 2) crystal and found: ιNi,Pt(1 1 0) ≈ 1.4 ± 0.1. Whatever the system (NiUPD/Pt(poly) or NiUPD/Pt(1 1 0)-(1 × 2)) or the experimental technique, Nickel formal partial charge number is lower than Nickel Cation charge: ιNi
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Understanding CO-stripping mechanism from NiUPD/Pt(110) in view of the measured Nickel formal partial charge number upon underpotential deposition on platinum surfaces in sulphate media
Electrochimica Acta, 2007Co-Authors: Marian Chatenet, Eric Chainet, Yvonne Soldo-olivier, R FaureAbstract:Abstract We recently showed Nickel-underpotential deposition (Ni-UPD) occurs on polycrystalline or single crystal platinum electrodes in acidic media. Whereas the decoupling of the Nickel and hydrogen adsorption/desorption peaks is difficult for low pH, these processes can be better separated for higher pH values, typically pH > 3. However, even for platinum single crystals, high pH solutions do not enable to sufficiently separate Nickel from hydrogen phenomena. As a result, electrochemistry alone cannot yield important information about Ni-UPD, such as the formal partial charge number (valency of electrosorption) and the role of the sulphate or hydrogen sulphate anions. So, we decided to couple cyclic voltammetry to electrochemical quartz crystal microbalance (EQCM). EQCM measurements enable to decorrelate the simultaneous hydrogen and Nickel adsorption/desorption peaks, which we could not attempt solely with electrochemistry. The coupling between gravimetric and electrochemical measurements allows us to detect the contribution of the anions and thus to isolate that of Nickel: Nickel coverage can then be determined. Nearly 4/5 Ni UPD monolayer ( θ Ni ≈ 0.8) over platinum is reached at Nickel equilibrium potential for high pH solutions (5.5). The QCM and electrochemistry coupling further allows the determination of Nickel formal partial charge number: ι Ni,EQCM = 1.3 ± 0.13. Direct electrochemistry measurements (Swathirajan and Bruckenstein method) yield: ι Ni,Pt(poly) = 1.5 ± 0.17. These two values are close, which validates the electrochemical method for the Nickel/platinum system. In consequence, we used Swathirajan and Bruckenstein method for Pt(1 1 0)-(1 × 2) crystal and found: ι Ni,Pt(1 1 0) ≈ 1.4 ± 0.1. Whatever the system (Ni UPD /Pt(poly) or Ni UPD /Pt(1 1 0)-(1 × 2)) or the experimental technique, Nickel formal partial charge number is lower than Nickel Cation charge: ι Ni z Ni = 2. In consequence, upon underpotential deposition on platinum surfaces, Nickel Cations discharge and then undergo additional charge exchange processes, such as anion (or water) adsorption, resulting in apparent partial Nickel Cation discharge. Moreover, Ni UPD /Pt(1 1 0) surface displays high activity towards CO ad oxidation reaction. We explain such positive effect by the possible existence of a bifunctional mechanism in which oxygenated-species-covered Ni UPD adatoms provide the oxygen atom to CO ad ⋯Pt species, enabling its facile oxidation.
Gregory N. Tew - One of the best experts on this subject based on the ideXlab platform.
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Thermodynamics of Counterion Release Is Critical for Anion Exchange Membrane Conductivity
Journal of the American Chemical Society, 2018Co-Authors: Michael T. Kwasny, Liang Zhu, Michael A. Hickner, Gregory N. TewAbstract:As the field of anion exchange membranes (AEMs) employs an increasing variety of Cations, a critical understanding of Cation properties must be obtained, especially as they relate to membrane ion conductivity. Here, to elucidate such properties, metal Cation-based AEMs, featuring bis(norbornene) Nickel, ruthenium, or cobalt complexes, were synthesized and characterized. In addition, isothermal titration calorimetry (ITC) was used to probe counterion exchange thermodynamics in order to understand previously reported differences in conductivity. The ion conductivity data reported here further demonstrated that Nickel-complex Cations had higher conductivity as compared to their ruthenium and cobalt counterparts. Surprisingly, bulk hydration number, ion concentration, ion exchange capacity, and activation energy were not sufficient to explain differences in conductivity, so the thermodynamics of metal Cation–counterion association were explored using ITC. Specifically, for the Nickel Cation as compared to the...
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utilizing thiol ene chemistry for crosslinked Nickel Cation based anion exchange membranes
Journal of Polymer Science Part A, 2018Co-Authors: Michael T. Kwasny, Liang Zhu, Michael A. Hickner, Gregory N. TewAbstract:Metal Cation-based anion exchange membranes (AEMs) are a unique class of materials that have shown potential to be highly stable AEMs with competitive conductivities. Here, we expand upon previous work to report the synthesis of crosslinked Nickel Cation-based AEMs formed using the thiol–ene reaction. These thiol–ene-based samples were first characterized for their morphology, both with and without Nickel Cations, where the Nickel-containing membranes demonstrated a disordered scattering peak characteristic of ionic clusters. The samples were then characterized for their water uptake, chemical and mechanical stability, and conductivity. They showed a combination of high water content and extreme brittleness, which also resulted in fairly low conductivity. The brittleness resulted from large water swelling as well as the need for each Nickel Cation to act as a crosslinker, necessary with the current Nickel-coordination chemistry. Therefore, increasing the ion exchange capacity (IEC) for these types of AEMs, important for enhancing conductivity, also increased the crosslink density. The low conductivity and brittleness seen in this work demonstrated the need to develop non-crosslinking metal-complexes. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017.
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Thermodynamics of Counterion Release Is Critical for Anion Exchange Membrane Conductivity
2018Co-Authors: Michael T. Kwasny, Liang Zhu, Michael A. Hickner, Gregory N. TewAbstract:As the field of anion exchange membranes (AEMs) employs an increasing variety of Cations, a critical understanding of Cation properties must be obtained, especially as they relate to membrane ion conductivity. Here, to elucidate such properties, metal Cation-based AEMs, featuring bis(norbornene) Nickel, ruthenium, or cobalt complexes, were synthesized and characterized. In addition, isothermal titration calorimetry (ITC) was used to probe counterion exchange thermodynamics in order to understand previously reported differences in conductivity. The ion conductivity data reported here further demonstrated that Nickel-complex Cations had higher conductivity as compared to their ruthenium and cobalt counterparts. Surprisingly, bulk hydration number, ion concentration, ion exchange capacity, and activation energy were not sufficient to explain differences in conductivity, so the thermodynamics of metal Cation–counterion association were explored using ITC. Specifically, for the Nickel Cation as compared to the other two metal-based Cations, a larger thermodynamic driving force for chloride counterion release was observed, shown through a smaller ΔHtot for counterion exchange, which indicated weaker Cation–counterion association. The use of ITC to study Cation–counterion association was further exemplified by characterizing more traditional AEM Cations, such as quaternary ammoniums and an imidazolium Cation, which demonstrated small variances in their enthalpic response, but an overall ΔHtot similar to that of the Nickel-based Cation. The Cation hydration, rather than its hydration shell or the bulk hydration of the membrane, likely played the key role in determining the strength of the initial Cation–counterion pair. This report identifies for the first time how ITC can be used to experimentally determine thermodynamic quantities that are key parameters for understanding and predicting conductivity in AEMs
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Utilizing thiol–ene chemistry for crosslinked Nickel Cation-based anion exchange membranes
Journal of Polymer Science Part A: Polymer Chemistry, 2017Co-Authors: Michael T. Kwasny, Liang Zhu, Michael A. Hickner, Gregory N. TewAbstract:Metal Cation-based anion exchange membranes (AEMs) are a unique class of materials that have shown potential to be highly stable AEMs with competitive conductivities. Here, we expand upon previous work to report the synthesis of crosslinked Nickel Cation-based AEMs formed using the thiol–ene reaction. These thiol–ene-based samples were first characterized for their morphology, both with and without Nickel Cations, where the Nickel-containing membranes demonstrated a disordered scattering peak characteristic of ionic clusters. The samples were then characterized for their water uptake, chemical and mechanical stability, and conductivity. They showed a combination of high water content and extreme brittleness, which also resulted in fairly low conductivity. The brittleness resulted from large water swelling as well as the need for each Nickel Cation to act as a crosslinker, necessary with the current Nickel-coordination chemistry. Therefore, increasing the ion exchange capacity (IEC) for these types of AEMs, important for enhancing conductivity, also increased the crosslink density. The low conductivity and brittleness seen in this work demonstrated the need to develop non-crosslinking metal-complexes. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017.
Marian Chatenet - One of the best experts on this subject based on the ideXlab platform.
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understanding co stripping mechanism from niupd pt 110 in view of the measured Nickel formal partial charge number upon underpotential deposition on platinum surfaces in sulphate media
Electrochimica Acta, 2007Co-Authors: Marian Chatenet, Yvonne Soldoolivier, Eric Chainet, R FaureAbstract:Abstract We recently showed Nickel-underpotential deposition (Ni-UPD) occurs on polycrystalline or single crystal platinum electrodes in acidic media. Whereas the decoupling of the Nickel and hydrogen adsorption/desorption peaks is difficult for low pH, these processes can be better separated for higher pH values, typically pH > 3. However, even for platinum single crystals, high pH solutions do not enable to sufficiently separate Nickel from hydrogen phenomena. As a result, electrochemistry alone cannot yield important information about Ni-UPD, such as the formal partial charge number (valency of electrosorption) and the role of the sulphate or hydrogen sulphate anions. So, we decided to couple cyclic voltammetry to electrochemical quartz crystal microbalance (EQCM). EQCM measurements enable to decorrelate the simultaneous hydrogen and Nickel adsorption/desorption peaks, which we could not attempt solely with electrochemistry. The coupling between gravimetric and electrochemical measurements allows us to detect the contribution of the anions and thus to isolate that of Nickel: Nickel coverage can then be determined. Nearly 4/5 Ni UPD monolayer ( θ Ni ≈ 0.8) over platinum is reached at Nickel equilibrium potential for high pH solutions (5.5). The QCM and electrochemistry coupling further allows the determination of Nickel formal partial charge number: ι Ni,EQCM = 1.3 ± 0.13. Direct electrochemistry measurements (Swathirajan and Bruckenstein method) yield: ι Ni,Pt(poly) = 1.5 ± 0.17. These two values are close, which validates the electrochemical method for the Nickel/platinum system. In consequence, we used Swathirajan and Bruckenstein method for Pt(1 1 0)-(1 × 2) crystal and found: ι Ni,Pt(1 1 0) ≈ 1.4 ± 0.1. Whatever the system (Ni UPD /Pt(poly) or Ni UPD /Pt(1 1 0)-(1 × 2)) or the experimental technique, Nickel formal partial charge number is lower than Nickel Cation charge: ι Ni z Ni = 2. In consequence, upon underpotential deposition on platinum surfaces, Nickel Cations discharge and then undergo additional charge exchange processes, such as anion (or water) adsorption, resulting in apparent partial Nickel Cation discharge. Moreover, Ni UPD /Pt(1 1 0) surface displays high activity towards CO ad oxidation reaction. We explain such positive effect by the possible existence of a bifunctional mechanism in which oxygenated-species-covered Ni UPD adatoms provide the oxygen atom to CO ad ⋯Pt species, enabling its facile oxidation.
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Understanding CO-stripping mechanism from NiUPD/Pt(1 1 0) in view of the measured Nickel formal partial charge number upon underpotential deposition on platinum surfaces in sulphate media
Electrochimica Acta, 2007Co-Authors: Marian Chatenet, Eric Chainet, Yvonne Soldo-olivier, R FaureAbstract:We recently showed Nickel-underpotential deposition (Ni-UPD) occurs on polycrystalline or single crystal platinum electrodes in acidic media. Whereas the decoupling of the Nickel and hydrogen adsorption/desorption peaks is difficult for low pH, these processes can be better separated for higher pH values, typically pH > 3. However, even for platinum single crystals, high pH solutions do not enable to sufficiently separate Nickel from hydrogen phenomena. As a result, electrochemistry alone cannot yield important information about Ni-UPD, such as the formal partial charge number (valency of electrosorption) and the role of the sulphate or hydrogen sulphate anions. So, we decided to couple cyclic voltammetry to electrochemical quartz crystal microbalance (EQCM). EQCM measurements enable to decorrelate the simultaneous hydrogen and Nickel adsorption/desorption peaks, which we could not attempt solely with electrochemistry. The coupling between gravimetric and electrochemical measurements allows us to detect the contribution of the anions and thus to isolate that of Nickel: Nickel coverage can then be determined. Nearly 4/5 NiUPD monolayer (θNi ≈ 0.8) over platinum is reached at Nickel equilibrium potential for high pH solutions (5.5). The QCM and electrochemistry coupling further allows the determination of Nickel formal partial charge number: ιNi,EQCM = 1.3 ± 0.13. Direct electrochemistry measurements (Swathirajan and Bruckenstein method) yield: ιNi,Pt(poly) = 1.5 ± 0.17. These two values are close, which validates the electrochemical method for the Nickel/platinum system. In consequence, we used Swathirajan and Bruckenstein method for Pt(1 1 0)-(1 × 2) crystal and found: ιNi,Pt(1 1 0) ≈ 1.4 ± 0.1. Whatever the system (NiUPD/Pt(poly) or NiUPD/Pt(1 1 0)-(1 × 2)) or the experimental technique, Nickel formal partial charge number is lower than Nickel Cation charge: ιNi
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Understanding CO-stripping mechanism from NiUPD/Pt(110) in view of the measured Nickel formal partial charge number upon underpotential deposition on platinum surfaces in sulphate media
Electrochimica Acta, 2007Co-Authors: Marian Chatenet, Eric Chainet, Yvonne Soldo-olivier, R FaureAbstract:Abstract We recently showed Nickel-underpotential deposition (Ni-UPD) occurs on polycrystalline or single crystal platinum electrodes in acidic media. Whereas the decoupling of the Nickel and hydrogen adsorption/desorption peaks is difficult for low pH, these processes can be better separated for higher pH values, typically pH > 3. However, even for platinum single crystals, high pH solutions do not enable to sufficiently separate Nickel from hydrogen phenomena. As a result, electrochemistry alone cannot yield important information about Ni-UPD, such as the formal partial charge number (valency of electrosorption) and the role of the sulphate or hydrogen sulphate anions. So, we decided to couple cyclic voltammetry to electrochemical quartz crystal microbalance (EQCM). EQCM measurements enable to decorrelate the simultaneous hydrogen and Nickel adsorption/desorption peaks, which we could not attempt solely with electrochemistry. The coupling between gravimetric and electrochemical measurements allows us to detect the contribution of the anions and thus to isolate that of Nickel: Nickel coverage can then be determined. Nearly 4/5 Ni UPD monolayer ( θ Ni ≈ 0.8) over platinum is reached at Nickel equilibrium potential for high pH solutions (5.5). The QCM and electrochemistry coupling further allows the determination of Nickel formal partial charge number: ι Ni,EQCM = 1.3 ± 0.13. Direct electrochemistry measurements (Swathirajan and Bruckenstein method) yield: ι Ni,Pt(poly) = 1.5 ± 0.17. These two values are close, which validates the electrochemical method for the Nickel/platinum system. In consequence, we used Swathirajan and Bruckenstein method for Pt(1 1 0)-(1 × 2) crystal and found: ι Ni,Pt(1 1 0) ≈ 1.4 ± 0.1. Whatever the system (Ni UPD /Pt(poly) or Ni UPD /Pt(1 1 0)-(1 × 2)) or the experimental technique, Nickel formal partial charge number is lower than Nickel Cation charge: ι Ni z Ni = 2. In consequence, upon underpotential deposition on platinum surfaces, Nickel Cations discharge and then undergo additional charge exchange processes, such as anion (or water) adsorption, resulting in apparent partial Nickel Cation discharge. Moreover, Ni UPD /Pt(1 1 0) surface displays high activity towards CO ad oxidation reaction. We explain such positive effect by the possible existence of a bifunctional mechanism in which oxygenated-species-covered Ni UPD adatoms provide the oxygen atom to CO ad ⋯Pt species, enabling its facile oxidation.
Shangqing Gong - One of the best experts on this subject based on the ideXlab platform.
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a longitudinally expanded ni based metal organic framework with enhanced double Nickel Cation catalysis reaction channels for a non enzymatic sweat glucose biosensor
Journal of Materials Chemistry B, 2020Co-Authors: Xiao Yang Xuan, Min Qian, Likun Pan, Lu Han, Lijia Wan, Yueping Niu, Shangqing GongAbstract:Nickel-based metal–organic frameworks (Ni-MOFs) have attracted increasing attention in non-enzymatic glucose sensing. However, the insufficient active Ni Cation sites from a stacked MOF layer, the unclear Ni catalysis mechanism, and the severe liquid alkaline electrolyte remain challenging for practical appliCations. In this work, the soniCation-induced longitudinal-expansion of Ni-MOFs increases the active Nickel ion sites, which not only enhances the current response to glucose detection, but also shows the oxidation peak evolution of Nickel ions with different soniCation times, revealing the mechanism of different glucose detection channels. The Ni-MOF sonicated for 60 min (60 min Ni-MOF) displays enhanced Ni(III)/Ni(II) and more significant Ni(IV)/Ni(III) double Nickel Cation channels for catalyzing glucose into glucolactone compared to the 0 min Ni-MOF (without soniCation), showing optimized glucose detection ability with a high sensitivity of 3297.10 μA mM−1 cm−2, a low detection limit of ∼8.97 μM (signal-to-noise = 3) and a wide linear response range from 10 to 400 μM from the cyclic voltammetry test as well as a high sensitivity of 3.03 μA mM−1 cm−2, a low detection limit of ∼1.16 μM (signal-to-noise = 3) and a wide linear response range from 10 to 2000 μM from the chronoamperometry test. More importantly, an all-solid-state glucose biosensor using a PVA/NaOH solid-state electrolyte and a disposable 60 min Ni-MOF working electrode is assembled for non-enzymatic sweat glucose detection.
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A longitudinally expanded Ni-based metal–organic framework with enhanced double Nickel Cation catalysis reaction channels for a non-enzymatic sweat glucose biosensor
Journal of materials chemistry. B, 2020Co-Authors: Xiao Yang Xuan, Min Qian, Likun Pan, Lu Han, Lijia Wan, Yueping Niu, Shangqing GongAbstract:Nickel-based metal–organic frameworks (Ni-MOFs) have attracted increasing attention in non-enzymatic glucose sensing. However, the insufficient active Ni Cation sites from a stacked MOF layer, the unclear Ni catalysis mechanism, and the severe liquid alkaline electrolyte remain challenging for practical appliCations. In this work, the soniCation-induced longitudinal-expansion of Ni-MOFs increases the active Nickel ion sites, which not only enhances the current response to glucose detection, but also shows the oxidation peak evolution of Nickel ions with different soniCation times, revealing the mechanism of different glucose detection channels. The Ni-MOF sonicated for 60 min (60 min Ni-MOF) displays enhanced Ni(III)/Ni(II) and more significant Ni(IV)/Ni(III) double Nickel Cation channels for catalyzing glucose into glucolactone compared to the 0 min Ni-MOF (without soniCation), showing optimized glucose detection ability with a high sensitivity of 3297.10 μA mM−1 cm−2, a low detection limit of ∼8.97 μM (signal-to-noise = 3) and a wide linear response range from 10 to 400 μM from the cyclic voltammetry test as well as a high sensitivity of 3.03 μA mM−1 cm−2, a low detection limit of ∼1.16 μM (signal-to-noise = 3) and a wide linear response range from 10 to 2000 μM from the chronoamperometry test. More importantly, an all-solid-state glucose biosensor using a PVA/NaOH solid-state electrolyte and a disposable 60 min Ni-MOF working electrode is assembled for non-enzymatic sweat glucose detection.
Michael T. Kwasny - One of the best experts on this subject based on the ideXlab platform.
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Thermodynamics of Counterion Release Is Critical for Anion Exchange Membrane Conductivity
Journal of the American Chemical Society, 2018Co-Authors: Michael T. Kwasny, Liang Zhu, Michael A. Hickner, Gregory N. TewAbstract:As the field of anion exchange membranes (AEMs) employs an increasing variety of Cations, a critical understanding of Cation properties must be obtained, especially as they relate to membrane ion conductivity. Here, to elucidate such properties, metal Cation-based AEMs, featuring bis(norbornene) Nickel, ruthenium, or cobalt complexes, were synthesized and characterized. In addition, isothermal titration calorimetry (ITC) was used to probe counterion exchange thermodynamics in order to understand previously reported differences in conductivity. The ion conductivity data reported here further demonstrated that Nickel-complex Cations had higher conductivity as compared to their ruthenium and cobalt counterparts. Surprisingly, bulk hydration number, ion concentration, ion exchange capacity, and activation energy were not sufficient to explain differences in conductivity, so the thermodynamics of metal Cation–counterion association were explored using ITC. Specifically, for the Nickel Cation as compared to the...
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utilizing thiol ene chemistry for crosslinked Nickel Cation based anion exchange membranes
Journal of Polymer Science Part A, 2018Co-Authors: Michael T. Kwasny, Liang Zhu, Michael A. Hickner, Gregory N. TewAbstract:Metal Cation-based anion exchange membranes (AEMs) are a unique class of materials that have shown potential to be highly stable AEMs with competitive conductivities. Here, we expand upon previous work to report the synthesis of crosslinked Nickel Cation-based AEMs formed using the thiol–ene reaction. These thiol–ene-based samples were first characterized for their morphology, both with and without Nickel Cations, where the Nickel-containing membranes demonstrated a disordered scattering peak characteristic of ionic clusters. The samples were then characterized for their water uptake, chemical and mechanical stability, and conductivity. They showed a combination of high water content and extreme brittleness, which also resulted in fairly low conductivity. The brittleness resulted from large water swelling as well as the need for each Nickel Cation to act as a crosslinker, necessary with the current Nickel-coordination chemistry. Therefore, increasing the ion exchange capacity (IEC) for these types of AEMs, important for enhancing conductivity, also increased the crosslink density. The low conductivity and brittleness seen in this work demonstrated the need to develop non-crosslinking metal-complexes. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017.
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Thermodynamics of Counterion Release Is Critical for Anion Exchange Membrane Conductivity
2018Co-Authors: Michael T. Kwasny, Liang Zhu, Michael A. Hickner, Gregory N. TewAbstract:As the field of anion exchange membranes (AEMs) employs an increasing variety of Cations, a critical understanding of Cation properties must be obtained, especially as they relate to membrane ion conductivity. Here, to elucidate such properties, metal Cation-based AEMs, featuring bis(norbornene) Nickel, ruthenium, or cobalt complexes, were synthesized and characterized. In addition, isothermal titration calorimetry (ITC) was used to probe counterion exchange thermodynamics in order to understand previously reported differences in conductivity. The ion conductivity data reported here further demonstrated that Nickel-complex Cations had higher conductivity as compared to their ruthenium and cobalt counterparts. Surprisingly, bulk hydration number, ion concentration, ion exchange capacity, and activation energy were not sufficient to explain differences in conductivity, so the thermodynamics of metal Cation–counterion association were explored using ITC. Specifically, for the Nickel Cation as compared to the other two metal-based Cations, a larger thermodynamic driving force for chloride counterion release was observed, shown through a smaller ΔHtot for counterion exchange, which indicated weaker Cation–counterion association. The use of ITC to study Cation–counterion association was further exemplified by characterizing more traditional AEM Cations, such as quaternary ammoniums and an imidazolium Cation, which demonstrated small variances in their enthalpic response, but an overall ΔHtot similar to that of the Nickel-based Cation. The Cation hydration, rather than its hydration shell or the bulk hydration of the membrane, likely played the key role in determining the strength of the initial Cation–counterion pair. This report identifies for the first time how ITC can be used to experimentally determine thermodynamic quantities that are key parameters for understanding and predicting conductivity in AEMs
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Utilizing thiol–ene chemistry for crosslinked Nickel Cation-based anion exchange membranes
Journal of Polymer Science Part A: Polymer Chemistry, 2017Co-Authors: Michael T. Kwasny, Liang Zhu, Michael A. Hickner, Gregory N. TewAbstract:Metal Cation-based anion exchange membranes (AEMs) are a unique class of materials that have shown potential to be highly stable AEMs with competitive conductivities. Here, we expand upon previous work to report the synthesis of crosslinked Nickel Cation-based AEMs formed using the thiol–ene reaction. These thiol–ene-based samples were first characterized for their morphology, both with and without Nickel Cations, where the Nickel-containing membranes demonstrated a disordered scattering peak characteristic of ionic clusters. The samples were then characterized for their water uptake, chemical and mechanical stability, and conductivity. They showed a combination of high water content and extreme brittleness, which also resulted in fairly low conductivity. The brittleness resulted from large water swelling as well as the need for each Nickel Cation to act as a crosslinker, necessary with the current Nickel-coordination chemistry. Therefore, increasing the ion exchange capacity (IEC) for these types of AEMs, important for enhancing conductivity, also increased the crosslink density. The low conductivity and brittleness seen in this work demonstrated the need to develop non-crosslinking metal-complexes. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017.