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Electrochemical pesticide detection and film deposition at liquid-liquid interface

Abstract : Modern electrochemistry at the liquid-liquid interface, also termed the interface between two immiscible electrolyte solutions (ITIES), has been investigated for over a century due to its special interface properties. It provides a unique platform to allows the non-redox electrochemical detection of ions ranging from protons to macromolecules across the soft molecular interface that is intrinsically defect-free and self-healing. Additionally, the ITIES can act as a scaffold to electrodeposit nanometer-sized objects or charged molecules in arrange film. This thesis is intended for the pesticide detection and electrodeposited films at ITIES. In the first part, we made an effort to detect pesticides at micro-ITIES due to its cost-effectiveness. Due to the miniaturization of ITIES, the micro-pore capillary can be as a support to construct a liquid-liquid interface. Thus, the accumulation of analytes from a solution close to neutral pH into an organic phase through an automatic transfer at open-circuit potential is possible and increasing the detection signal. This strategy is successful for ametryn but is failed for the detection of Imidacloprid and Metam sodium. In the second part, we developed silica deposition at Micro-ITIES. The objective of the silica membrane at ITIES is to focus on improving the selectivity for ion transfer. Electrochemical experiments at the liquid-liquid interface revealed that the TMA+ transfer is blocked by the presence of silica film. However, electrodeposit silica at Micro-ITIES is not accurately reproduced due to the geometry limitation. Furthermore, the ex-situ measures are hardly achieved. In the third part, we realized chitosan electrodeposition at ITIES. Chitosan films act as membrane for ion transfer and presented positive charge, which could provide the adsorption effect for negative ion. To improve the structure of chitosan film, the cross-linker Terephthalaldehyde (TPA) is introduced into the organic phase. We demonstrated a protocol for controlling the interfacial reaction with the variable concentration of cross-linker in the organic phase, and the precursor is limited in the aqueous phase. Therefore, we obtained different types of chitosan films.
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https://hal.univ-lorraine.fr/tel-03264568
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Submitted on : Friday, June 18, 2021 - 12:41:43 PM
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  • HAL Id : tel-03264568, version 1

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Guofeng Lu. Electrochemical pesticide detection and film deposition at liquid-liquid interface. Analytical chemistry. Université de Lorraine, 2020. English. ⟨NNT : 2020LORR0231⟩. ⟨tel-03264568⟩

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