An X‐ray photoelectron spectroscopy investigation of silver iodide‐coated ion‐selective electrodes

Strydom, Christien A.; Staden, Jacobus Frederick van; Strydom, H. J.

doi:10.1002/elan.1140041009

Cited by 10 publications

(5 citation statements)

References 6 publications

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“…The spectra show a continuous increase of the iodine and an accompanying decrease of the silver signal with longer iodine exposure: both reaching characteristic saturation values after about 60 s. The straight forward interpretation of a sequence of spectra between 0 s and 180 s of iodine exposure shows a gradual transformation of the AgTF into β-AgI thin film as supported from the aforementioned GIXD results (section 1) and optoelectronic properties in the next sections 19 20 . Accompanying the change in surface stoichiometry, we observe a systematic shift of both the Ag and the I core level doublets towards higher binding energies ( cf.…”

Section: Resultssupporting

confidence: 54%

Systematic Surface Phase Transition of Ag Thin Films by Iodine Functionalization at Room Temperature: Evolution of Optoelectronic and Texture Properties

Bashouti

Talebi

Kassar

et al. 2016

Sci Rep

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We show a simple room temperature surface functionalization approach using iodine vapour to control a surface phase transition from cubic silver (Ag) of thin films into wurtzite silver-iodid (β-AgI) films. A combination of surface characterization techniques (optical, electronical and structural characterization) reveal distinct physical properties of the new surface phase. We discuss the AgI thin film formation dynamics and related transformation of physical properties by determining the work-function, dielectric constant and pyroelectric behavior together with morphological and structural thin film properties such as layer thickness, grain structure and texture formation. Notable results are: (i) a remarkable increase of the work-function (by 0.9 eV) of the Ag thin layer after short a iodine exposure time (≤60 s), with simultaneous increase of the thin film transparency (by two orders of magnitude), (ii) pinning of the Fermi level at the valance band maximum upon iodine functionalization, (iii) 84% of all crystallites grain were aligned as a result of the evolution of an internal electric field. Realizing a nano-scale layer stack composed of a dielectric AgI layer on top of a metallic thin Ag layer with such a simple method has some technological implications e.g. to realize optical elements such as planar optical waveguides.

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Section: Resultssupporting

confidence: 54%

Systematic Surface Phase Transition of Ag Thin Films by Iodine Functionalization at Room Temperature: Evolution of Optoelectronic and Texture Properties

Bashouti

Talebi

Kassar

et al. 2016

Sci Rep

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“…In contrast to AgCl, the silver iodide has a much lower solubility product: 8.3 × 10 –17 vs 1.8 × 10 –10 . The silver iodide electrode was successfully used as a pseudoreference for the detection with ion-selective electrodes, − and long-term stability of the AgI film was confirmed with an X-ray photoelectron spectroscopy studies . Lower solubility product corresponds to lower contamination of the sample with silver and halide ions.…”

Section: Resultsmentioning

confidence: 89%

Detection Limits of Thin Layer Coulometry with Ionophore Based Ion-Selective Membranes

2012

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We report here on a significant improvement in lowering the low detection limit of thin layer coulometric sensors based on liquid ion-selective membranes, using a potassium-selective system as a model example. Various possible processes that may result in an elevated residual current reading after electrolysis were eliminated. Self-dissolution of AgCl on the Ag/AgCl inner element may result in a residual ion flux that could adversely affect the lower detection limit. It was here replaced with an Ag/AgI inner pseudoreference electrode where the self-dissolution equilibrium is largely suppressed. Possible residual currents originating from a direct contact between inner element and ion-selective membranes were eliminated by introducing an inert PVDF separator of 50 μm diameter that was coiled around the inner element by a custom-made instrument. Finally, the influence of electrolyte fluxes from the outer solution across the membrane into the sample was evaluated by altering its lipophilic nature and reducing its concentration. It was found that this last effect is most likely responsible for the observed residual current for the potassium-selective membranes studied here. For the optimized conditions, the calibration curves demonstrated a near zero intercept, thereby paving the way to the coulometric calibration-free sensing of ionic species. A linear calibration curve for the coulometric cell with valinomycin potassium-selective membrane was obtained in the range of 100 nM to 10 μM potassium in the presence of a 10 μM sodium background. In the presence of a higher (100 μM) concentration of sodium, a reliable detection of 1-100 μM of potassium was achieved.

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“…As an alternative, a Ag|AgI reference electrode was used, for not only is I - less soluble than Cl - , K sp for I - = 8 × 10 -17 and for Cl - = 2 × 10 -10 ( The Merck Index ; Merck & Co.: Rahway, NJ, 1996), but X-ray photoelectron spectroscopic studies have shown that AgI is a particularly stable reference material when exposed to aqueous electrolytes …”

Section: Resultsmentioning

confidence: 99%

Micromachining Sensors for Electrochemical Measurement in Subnanoliter Volumes

1997

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An X‐ray photoelectron spectroscopy investigation of silver iodide‐coated ion‐selective electrodes

Cited by 10 publications

References 6 publications

Systematic Surface Phase Transition of Ag Thin Films by Iodine Functionalization at Room Temperature: Evolution of Optoelectronic and Texture Properties

Systematic Surface Phase Transition of Ag Thin Films by Iodine Functionalization at Room Temperature: Evolution of Optoelectronic and Texture Properties

Detection Limits of Thin Layer Coulometry with Ionophore Based Ion-Selective Membranes

Micromachining Sensors for Electrochemical Measurement in Subnanoliter Volumes

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