Hydrogels Doped with Redox Buffers as Transducers for Ion-Selective Electrodes

Rousseau, Celeste R.; Honig, Madeline L.; Bühlmann, Philippe

doi:10.1021/acs.analchem.1c04264

Cited by 5 publications

(4 citation statements)

References 48 publications

(95 reference statements)

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“…Additionally, a PVA hydrogel has been used as a dopant to solidify the hydrophilic SC of a ferricyanide/ferrocyanide redox buffer for a stable and reproducible SC-ISE, which suggests its application in potentiometric ion sensors. 44 In this work, the concept of GO-PVA hydrogel-coated SC-ISEs has been introduced and applied for a wearable sweat potassium ion sensor. The GO-PVA hydrogel avoids direct contact of the ISM with the skin.…”

Section: ■ Introductionmentioning

confidence: 99%

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Graphene Oxide–Poly(vinyl alcohol) Hydrogel-Coated Solid-Contact Ion-Selective Electrodes for Wearable Sweat Potassium Ion Sensing

Liu,

Zhong,

Tang

et al. 2024

Anal. Chem.

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Solid-contact ion-selective electrodes (SC-ISEs) with ionophore-based polymer-sensitive membranes have been the major devices in wearable sweat sensors toward electrolyte analysis. However, the toxicity of ionophores in ion-selective membranes (ISMs), for example, valinomycin (K + ion carrier), is a significant challenge, since the ISM directly contacts the skin during the tests. Herein, we report coating a hydrogel of graphene oxide−poly(vinyl alcohol) (GO-PVA) on the ISM to fabricate hydrogel-based SC-ISEs. The hydrogen bond interaction between GO sheets and PVA chains could enhance the mechanical strength through the formation of a cross-linking network. Comprehensive electrochemical tests have demonstrated that hydrogel-coated K + -SC-ISE maintains Nernstian response sensitivity, high selectivity, and anti-interference ability compared with uncoated K + -SC-ISE. A flexible hydrogel-based K + sensing device was further fabricated with the integration of a solid-contact reference electrode, which has realized the monitoring of sweat K + in real time. This work highlights the possibility of hydrogel coating for fabricating biocompatible wearable potentiometric sweat electrolyte sensors.

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Section: ■ Introductionmentioning

confidence: 99%

“…These groups could enhance the mechanical strength by cross-linking PVA chains via a hydrogen bond interaction. Additionally, a PVA hydrogel has been used as a dopant to solidify the hydrophilic SC of a ferricyanide/ferrocyanide redox buffer for a stable and reproducible SC-ISE, which suggests its application in potentiometric ion sensors …”

Section: Introductionmentioning

confidence: 99%

Graphene Oxide–Poly(vinyl alcohol) Hydrogel-Coated Solid-Contact Ion-Selective Electrodes for Wearable Sweat Potassium Ion Sensing

Liu,

Zhong,

Tang

et al. 2024

Anal. Chem.

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“…To stabilize this interfacial potential, intermediate layers consisting of conducting polymers with a high redox capacitance were introduced. − , The E ° values of such are, however, not very reproducible, and they change over time, which can be attributed to a wide variability in local conformations as well as spontaneous oxidation by ambient oxygen. ,, In an attempt to use a more well-defined molecular redox buffer, redox-active self-assembled monolayers (SAMs) were explored, such as ferrocene-modified SAMs, but the redox buffer capacity of these sensors was insufficient due to the small amount of redox species in the monolayer on the planar substrate. , More recently, this concept has been extended to polymers doped with metal–organic complexes − and TEMPO , as redox-active species, and the advantages of using redox buffers comprising both the reduced and oxidized forms of the redox buffer have been shown. − …”

Section: Introductionmentioning

confidence: 99%

Functionalizing Carbon Substrates with a Covalently Attached Cobalt Redox Buffer for Calibration-Free Solid-Contact Ion-Selective Electrodes

Kim,

Dong,

Spindler

et al. 2024

Anal. Chem.

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With a view to potentiometric sensing with minimal calibration requirements and high long-term stability, colloidimprinted mesoporous (CIM) carbon was functionalized by the covalent attachment of a cobalt redox buffer and used as a new solid contact for ion-selective electrodes (ISEs). The CIM carbon surface was first modified by electroless grafting of a terpyridine ligand (Tpy-ph) using diazonium chemistry, followed by stepwise binding of Co(II) and an additional Tpy ligand to the grafted ligand, forming a bis(terpyridine) Co(II) complex, CIM-ph-Tpy-Co(II)-Tpy. Half a molar equivalent of ferrocenium tetrakis(3chlorophenyl)borate was then used to partially oxidize the Co(II) complex. Electrodes prepared with this surface-attached CIM-ph-Tpy-Co(III/II)-Tpy redox buffer as a solid contact were tested as K + sensors in combination with valinomycin as the ionophore and Dow 3140 silicone or plasticized poly(vinyl chloride) (PVC) as the matrixes for the ion-selective membrane (ISM). This solid contact is characterized by a redox capacitance of 3.26 F/g, ensuring a well-defined interfacial potential that underpins the transduction mechanism. By use of a redox couple as an internal reference element to control the phase boundary potential at the interface of the ISM and the CIM carbon solid contact, solid-contact ionselective electrodes (SC-ISEs) with a standard deviation of E°as low as 0.3 mV for plasticized PVC ISMs and 3.5 mV for Dow 3140 silicone ISMs were obtained. Over 100 h, these SC-ISEs exhibit an emf drift of 20 μV/h for plasticized PVC ISMs and 62 μV/h for silicone ISMs. The differences in long-term stability and reproducibility between electrodes with ISMs comprising either a plasticized PVC or silicone matrix offer valuable insights into the effect of the polymeric matrix on sensor performance.

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“…Specifically, in a flow-type system, we stopped the flow after feeding the sample into the flow path of the ISE and analyzed the dependence of the measured potential on the time. The ISEs used for this purpose comprised high-capacity ion-exchanger (HCIE) membranes, , which are characterized by high ion fluxes. , For comparison, transient potential changes caused by ion flux phenomena were also studied in membranes with low charge densities, such as an ion exchange membrane with a top layer inhibiting ion exchange as well as plasticized poly(vinyl chloride) (PVC) membranes doped with a quaternary ammonium salt. The mechanism underlying the transient potential changes in stationary solutions is also discussed.…”

mentioning

confidence: 99%

Detection of Interfering Ions Using Ion Flux Phenomena in Flow-Through Cl-ISEs with Ion Exchange Membranes

2023

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Ion-selective electrodes (ISEs) are among the most successful electrochemical sensors used in various applications because of their ability to measure electrolyte concentrations in liquids easily. It is common practice to suppress ion fluxes through the ion-sensitive membranes in ISEs because such fluxes worsen the lower limit of detection. In this study, we propose a method to detect interfering ions using this ion flux phenomenon. As a proof of principle, a flow-type Cl-ISE based on an ion exchange membrane loaded with the target ion chloride was used to acquire transient potential profiles during standstill after the introduction of liquids containing various ion species. When the target ion of the ion-sensitive membrane was measured, there was almost no change in potential over time. In contrast, when hydrophilic interfering ions were measured, the potential gradually decreased, and when hydrophobic interfering ions were measured, the potential gradually increased. The direction and intensity of these changes over time depended on the ion species and concentrations. The main reason for these potential changes is presumed to be the change in the local ionic composition of the sample near the sensing membrane due to ion exchange between the sample and membrane. This phenomenon could not be observed in a hydrophobic ion exchanger membrane doped with a quaternary ammonium salt and was characteristically observable using hydrophilic ion exchange membranes with a high charge density and a high ion diffusion rate. Finally, using a high-throughput flow-type system, we demonstrated the detection of interfering ions in solutions containing multiple ion species by using the ion flux phenomenon.

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Hydrogels Doped with Redox Buffers as Transducers for Ion-Selective Electrodes

Cited by 5 publications

References 48 publications

Graphene Oxide–Poly(vinyl alcohol) Hydrogel-Coated Solid-Contact Ion-Selective Electrodes for Wearable Sweat Potassium Ion Sensing

Graphene Oxide–Poly(vinyl alcohol) Hydrogel-Coated Solid-Contact Ion-Selective Electrodes for Wearable Sweat Potassium Ion Sensing

Functionalizing Carbon Substrates with a Covalently Attached Cobalt Redox Buffer for Calibration-Free Solid-Contact Ion-Selective Electrodes

Detection of Interfering Ions Using Ion Flux Phenomena in Flow-Through Cl-ISEs with Ion Exchange Membranes

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