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A Calibration-Free pH Sensor Using an In-Situ Modified Ir Electrode for Bespoke Application in Seawater.

ABSTRACT: A bespoke calibration-free pH sensor using an in situ modified Ir electrode for applications in seawater is reported. The electrochemical behaviour of an iridium wire in air-saturated synthetic seawater was studied and the formation of pH-sensitive surface layers was observed that featured three pH-sensitive redox couples, Ir(III/IV), IrOxOI-/IrOxOII-H, and H_upd/H⁺, where H_upd is adsorbed hydrogen deposited at underpotential conditions. The amperometric properties of the electrochemically activated Ir wire were investigated using linear sweep voltammetry first, followed, second, by square wave voltammetry with the formation conditions in seawater for the optimal pH sensitivity of the redox couples identified. The sensor was designed to be calibration-free by measuring the "super-Nernstian" response, in excess of ca 60 mV per pH unit, of Ir(III/IV) relative to the less sensitive upd H oxidation signal with the pH reported on the total pH scale. The pH dependency of the optimised sensor was 70.1 ± 1.4 mV per pH unit at 25 °C, showing a super-Nernstian response of high sensitivity.

SUBMITTER: Chen Y

PROVIDER: S-EPMC9102169 | biostudies-literature | 2022 Apr

REPOSITORIES: biostudies-literature

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A Calibration-Free pH Sensor Using an In-Situ Modified Ir Electrode for Bespoke Application in Seawater.

Chen Yuqi Y Compton Richard R

Sensors (Basel, Switzerland) 20220425 9

A bespoke calibration-free pH sensor using an in situ modified Ir electrode for applications in seawater is reported. The electrochemical behaviour of an iridium wire in air-saturated synthetic seawater was studied and the formation of pH-sensitive surface layers was observed that featured three pH-sensitive redox couples, Ir(III/IV), IrOxOI-/IrOxOII-H, and Hupd/H+, where Hupd is adsorbed hydrogen deposited at underpotential conditions. The amperometric propertie ...[more]

PMID: 35590977

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Project description:The development of eco-friendly chemicals and material-based electrode systems with a reduced carbon footprint is a novel initiative for future technological applications. While electrochemical systems based on plant phytochemicals meet the requirements, comprehending the fundamental electron-transfer reactions and preparing stable surface-confined redox systems pose significant research challenges. In this study, we have demonstrated an in situ electrochemical reaction-assisted entrapment of redox-active betanin molecular species from native beetroot plants on a carbon black-modified glassy carbon surface (GCE/CB@Betn-Redox, where Betn-Redox stands for redox-active betanin molecular species) in a pH 2.2 KCl-HCl solution. In general, direct access to native plant phytochemicals is a formidable task due to the matrix effect. Isolating the desired phytochemicals necessitates a series of time-consuming chemical separation steps. Unlike previous literature reports on the unstable nature of Betn, GCE/CB@Betn-Redox exhibited a stable and well-defined proton-coupled electron-transfer peak at an apparent electrode potential, Eo' = 0.4 V vs Ag/AgCl, with a surface-excess value of 17.02 × 10-9 mol cm-2. Using several physicochemical techniques (transmission electron microscopy (TEM), Fourier-transform infrared (FTIR), and Raman), molecular techniques (UPLC), and electrochemical methods (in situ electrochemical quartz crystal microbalance (EQCM) and scanning electrochemical microscopy (SECM)), we have demonstrated the biomimicking electron-transfer functionality of CB@Betn-Redox. The unique feature of CB@Betn-Redox is its nonmediated effect on common biochemicals. This advantage makes it an interesting option for use as a selective pH sensor system without the complications of voltage drift that occur with the mediated oxidation/reduction functionality. We have successfully demonstrated highly selective and stable voltammetric and potentiometric pH sensor applications with practical real samples.

Dataset Information

A Calibration-Free pH Sensor Using an In-Situ Modified Ir Electrode for Bespoke Application in Seawater.

Publications

A Calibration-Free pH Sensor Using an In-Situ Modified Ir Electrode for Bespoke Application in Seawater.

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