Development and Optimisation of Integrated Electrochemical Sensors for Aquatic Analysis

Diplôme Thèse Development and Optimisation of Integrated Electrochemical Sensors for Aquatic Analysis eng 2023 2023 author Forrest Tara 0000-0003-2243-3221 788805 director Bakker Eric 716236 Département de chimie minérale et analytique (CHIAM) 10.13097/archive-ouverte/unige:172738 urn:nbn:ch:unige-1727383 Sc. 5769 Being able to precisely estimate the concentration of ions in a sample has always been of specific interest. Classical analytical techniques, such as titration or gravimetric analysis, were initially employed but showed limitations. Ion-selective electrodes (ISE) based on polymeric membranes were introduced a couple of decades ago and present a viable option to have a small, portable and affordable measuring platform for ions. They rely on potentiometry, an open-circuit measurement technique requiring low operating power, where a potential difference between the working and reference electrode of same cell is measured. The response of the working electrode as a function of ionic activity can be easily estimated using the Nernst equation. This thesis focuses on enhancing and improving the stability and longevity of potentiometric sensors. Chapter 1 will provide an overview of potentiometric sensors, focussing on the shift from liquid inner filling solution towards solid-contact ion-selective electrodes. Chapter 2 will present the use of thin membranes (nm thick) to speed up the development process of new ion-selective systems. To illustrate and showcase this new methodology, a hydrophobic transducing redox polymer, PEDOT-C14, was used for the first time as transducer in anion-selective membranes. Chapter 3 will focus more on the reference element in a potentiometric cell. The use of a regenerated cellulose-based dialysis membrane as liquid junction material was investigated. Liquid junction potential predictions according to the Henderson equation were made, but due to deviations from the theoretical behaviour, a new mathematical model was developed. This new simple calculation method, based on partial Donnan exclusion, showed good correlation with the rigorous Nernst-Poisson-Planck (NPP) simulation method. Chapter 4 presents the design and field testing of a potentiometric probe for nitrate analysis in freshwater. Sensors based on the previously developed PEDOT-C14 transducer were applied successfully in real conditions. To correct underlying drifts occurring on the electrode side, a one-point calibration step was implemented and pre-programmed to run at defined time intervals. A symmetrical reference element was also deployed for the first time on the field to reduce fluctuations caused by environmental factors. Chapter 5 presents the use of a self-plasticised matrix for ion-selective membranes. It is well known that the plasticiser that is added to the polymer to reduce its hardness tends to leach, causing drifts. In this work, using “Click” chemistry, a plasticiser-like moiety was grafted to azide-modified poly(vinyl chloride), inhibiting the leaching process. This newly developed polymer was successfully used in pH and potassium-selective electrodes. Chapter 6 investigates a new versatile transducing polymer, PEDOT-N3. This redox polymer is not naturally considered a good transducer due to its high hydrophilicity, but the azide groups offer a good platform to perform surface “Click” chemistry with hydrophobic groups. After surface grafting, the properties of these modified transducing layers were evaluated through contact angle measurements and then finally tested as ion-to-electron transducers ion solid-contact ion-selective electrodes. Chapter 7 offers a conclusion of the thesis while discussing possible outlooks and further development of this work. Ion Sensing Ion-Selective Electrodes Potentiometric Sensor Transducers Aquatic Analysis Click Chemistry Electrochemical Sensors Dewey 540 40 Département de chimie minérale, analytique et appliquée 145 false 772 Groupe Bakker 2ed1499a-5244-4566-bf78-0c8b1779185a Thesis Public Thesis Archive Ouverte.pdf 28270343 application/pdf Private 2025-01-01 a5e25d6347d4ba71227df4bfc82fd3b9bc4751954bcbdf7484d2c4c8f95a9b70 dbf74791-e5f2-41a2-923a-32bfa1bee246 Imprimatur Public Imprimatur.pdf 107235 application/pdf 37866dfad9df0054565ce27ff70a8fd0efa536fc29c84ac4803143ddd81efd20 9e397020-382d-4511-8ae6-454ed3708047 Publication mode Private Mode de Publication.pdf 268895 application/pdf 6f4d0f57576a5d2153efb2a6cdc0796c8deb7ae8d4450fa1c9be98e509e40fe6 0e4aa94e-ebf1-4360-a7e1-5defc27c7fab Agreement Private Contrat_diffusion_these_v2022_DocuS.pdf 1257517 application/pdf e22b9af96ddb62eb561a36c8d1bee614806b20929ecabe986033e145cad10213 tara.forrest@unige.ch Le Châtelard 75 1633 Marsens embargoedAccess Faculté des sciences / Section de chimie et biochimie / Département de chimie minérale, analytique et appliquée

Title	Published in	Year	Views	Downloads

Development and Optimisation of Integrated Electrochemical Sensors for Aquatic Analysis		2023	123	1
Thin Layer Membrane Systems as Rapid Development Tool for Potentiometric Solid Contact Ion‐selective Electrodes	Electroanalysis	2020	258	196

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