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Functional 1D mesochannels for Electrochemical Sensors

Abstract : In this thesis, we discuss vertically oriented mesoporous silica and their characteristic properties, synthesis procedures and applications. It is of particular interest as it provides direct access to underlying substrate through the pores and is suitable for a variety of applications such as molecular sieving, electrode protection, enhanced detection of cations through electrochemistry and electrochemiluminescence, deposition of isolated metallic and polymeric nanowires, DNA biosensor, etc. We then discuss the electrochemically mediated oxidation of natural aminothiols (cysteine, glutathione and homocysteine) by a ferrocene derivative following an EC’ mechanism and the rate kinetics at a bare indium-tin oxide (ITO) electrode. Further, mesoporous silica thin films exhibiting vertical nanochannels were grown by electrochemically assisted self-assembly method onto ITO electrode. When using the silica film deposited electrodes and ferrocenedimethanol (Fc(MeOH)2) as mediator in solution, both cysteine and glutathione can be oxidized by Fc(MeOH)2+ generated at the electrode surface, following an EC’ mechanism. Electron transfer rates were three times faster with cysteine than glutathione, suggesting that selectivity for cysteine could be achieved using mesoporous films. This was exploited for the reagent-free selective detection of cysteine over glutathione by using a ferrocene-functionalized mesoporous silica film on ITO electrode, based on a combination of charge transfer kinetic and mass transport limitations through the oriented nanochannels. This has been demonstrated by cyclic voltammetry and amperometry in a flow injection analysis mode. Experimentally, the lowest concentration of cysteine detected was 3 µM in flow injection analysis mode. Further, microelectrodes made of ITO and carbon were fabricated and modified with mesoporous silica. Carbon microelectrodes were further functionalized with ferrocene and characterized electrochemically. Overall, silica modified electrodes show a good potential in electroanalytical applications for a variety of reagents through their size and charge selective properties.
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Submitted on : Tuesday, July 13, 2021 - 11:52:50 AM
Last modification on : Sunday, June 26, 2022 - 3:10:55 AM
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  • HAL Id : tel-03285377, version 1


Himanshu Maheshwari. Functional 1D mesochannels for Electrochemical Sensors. Chemical Sciences. Université de Lorraine, 2020. English. ⟨NNT : 2020LORR0267⟩. ⟨tel-03285377⟩



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