Electrochemistry of ion-selective electrodes

Buck, Richard P.

doi:10.1016/0250-6874(81)80010-8

Cited by 39 publications

(3 citation statements)

References 58 publications

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“…This roughness has an impact on the diffusion layer, which is translated into a difference in the time response and stability of the devices [ 34 , 37 ]. In addition, such roughness can increase the interfacial resistance of the films due to a change on their capacitive behavior [ 38 , 39 , 40 ]. Consequently, the fabrication of highly smooth and homogeneous films is necessary to achieve a systematic study of the effects of thickness in the performance of the ion sensors.…”

Section: Resultsmentioning

confidence: 99%

Integration of an Aerosol-Assisted Deposition Technique for the Deposition of Functional Biomaterials Applied to the Fabrication of Miniaturised Ion Sensors

Ruiz-Gonzalez

Choy

2021

Nanomaterials

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Ion-selective electrodes are at the forefront of research nowadays, with applications in healthcare, agriculture and water quality analysis among others. Despite multiple attempts of miniaturization of these polyvinyl chloride (PVC) gel-based ion sensors, no ion-sensing devices with a thickness below the micrometer range, and operating using open circuit potential, have been developed so far. This work reports the causes of this thickness limitation in potassium-selective sensors. Highly homogeneous ion-sensing films were fabricated by a method based on aerosol assisted chemical vapour deposition, leading to smooth surfaces with 27 ± 11 nm of roughness. Such homogeneity allowed the systematic study of the performance and ionic diffusion properties of the sensing films at sub-micrometer scales. Sensitivities below the Nernst response were found at low thicknesses. The nature of this reduction in sensitivity was studied, and a difference in the superficial and bulk compositions of the films was measured. An optimal configuration was found at 15 µm, with a good selectivity against Na+ (KK+, Na+ = −1.8) a limit of detection in the range of 10−4 M and esponse time below 40 s. The stability of sensors was improved by the deposition of protective layers, which expanded the lifespan of the ion sensors up to 5 weeks while preserving the Nernst sensitivity.

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Section: Resultsmentioning

confidence: 99%

Integration of an Aerosol-Assisted Deposition Technique for the Deposition of Functional Biomaterials Applied to the Fabrication of Miniaturised Ion Sensors

Ruiz-Gonzalez

Choy

2021

Nanomaterials

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“…The kinetics of ion exchange across the electrolyte/insertion electrode interface has recently been reported to be very fast at ambient temperature an.d the associated charge transfer resistance could not be detected using a-c impedance techniques (23). In addition, it is known that rapid, reversible ion exchange processes correspond to exchange current densities higher than about 0.1 A 9 cm -2 (24). The small charge transfer resistance found in the present study is an important result since it means that the kinetics of the system is limited only by proton diffusion in the electrochromic material.…”

Section: Resultsmentioning

confidence: 99%

Proton Diffusion in Tungsten Trioxide Thin Films

Randin¹,

Viennet²

1982

J. Electrochem. Soc.

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A small signal a‐c impedance method has been applied to the cell HyWO3/normalacid electrolyte/normalhigh surface area carbon, in which the carbon electrode acts as a nonpolarizable electrode. Tungsten trioxide films were prepared by vacuum evaporation onto tin oxide covered glass substrate. The films, which were initially amorphous, were heated in air at temperatures from 300° to 400°C. The a‐c impedance measurements were carried out at several temperatures as a function of frequency from 10−2 to 105 Hz. The Randles circuit was fitted to the data by nonlinear chi‐squared minimization. The amorphous films have higher diffusion coefficients, i.e., about 4×10−10 cm2/sec at 20°C, than crystalline samples, i.e., 2×10−11 cm2/sec at 20°C. The activation energy for the amorphous sample is about 0.25 eV as compared to about 0.4 eV for crystalline films. Such a difference might be explained by a difference in composition and density between the amorphous and crystalline films or by different transport mechanisms such as hopping of H+ and diffusion of oxygen ion vacancies. The diffusion coefficient does not change significantly with composition in the range 0.01

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“…The selectivity series can be modified through changes of the membrane dielectric properties, e.g., by using different plasticizers or by compounding membranes with selective hydrophobic complexing agents: neutral or charged carriers. Addition of carriers (ionophores) into the membrane phase, Figure , confers special selectivity to the counterion exchange or extraction processes that forces a non-Hofmeister response. − The ion exchange or partitioning of a desired counterion is accompanied by formation of an association complex. For uncharged carriers, the bonding is of ion−dipole interaction type, and characteristic structures, typically octahedral, of carbonyl and ether oxygens of the carriers are involved.…”

Section: Introductionmentioning

confidence: 99%