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Direct imaging of micrometer-thick interfaces in salt–salt aqueous biphasic systems

Unlike the interface between two immiscible electrolyte solutions (ITIES) formed between water and polar solvents, molecular understanding of the liquid–liquid interface formed for aqueous biphasic systems (ABSs) is relatively limited and mostly relies on surface tension measurements and thermodynam...

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Autores principales: Degoulange, Damien, Pandya, Raj, Deschamps, Michael, Skiba, Dhyllan A., Gallant, Betar M., Gigan, Sylvain, de Aguiar, Hilton B., Grimaud, Alexis
Formato: Online Artículo Texto
Lenguaje:English
Publicado: National Academy of Sciences 2023
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10151592/
https://www.ncbi.nlm.nih.gov/pubmed/37068232
http://dx.doi.org/10.1073/pnas.2220662120
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author Degoulange, Damien
Pandya, Raj
Deschamps, Michael
Skiba, Dhyllan A.
Gallant, Betar M.
Gigan, Sylvain
de Aguiar, Hilton B.
Grimaud, Alexis
author_facet Degoulange, Damien
Pandya, Raj
Deschamps, Michael
Skiba, Dhyllan A.
Gallant, Betar M.
Gigan, Sylvain
de Aguiar, Hilton B.
Grimaud, Alexis
author_sort Degoulange, Damien
collection PubMed
description Unlike the interface between two immiscible electrolyte solutions (ITIES) formed between water and polar solvents, molecular understanding of the liquid–liquid interface formed for aqueous biphasic systems (ABSs) is relatively limited and mostly relies on surface tension measurements and thermodynamic models. Here, high-resolution Raman imaging is used to provide spatial and chemical resolution of the interface of lithium chloride - lithium bis(trifluoromethanesulfonyl)imide - water (LiCl–LiTFSI–water) and HCl–LiTFSI–water, prototypical salt–salt ABSs found in a range of electrochemical applications. The concentration profiles of both TFSI anions and water are found to be sigmoidal thus not showing any signs of a positive adsorption for both salts and solvent. More striking, however, is the length at which the concentration profiles extend, ranging from 11 to 2 µm with increasing concentrations, compared to a few nanometers for ITIES. We thus reveal that unlike ITIES, salt–salt ABSs do not have a molecularly sharp interface but rather form an interphase with a gradual change of environment from one phase to the other. This knowledge represents a major stepping-stone in the understanding of aqueous interfaces, key for mastering ion or electron transfer dynamics in a wide range of biological and technological settings including novel battery technologies such as membraneless redox flow and dual-ion batteries.
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spelling pubmed-101515922023-10-17 Direct imaging of micrometer-thick interfaces in salt–salt aqueous biphasic systems Degoulange, Damien Pandya, Raj Deschamps, Michael Skiba, Dhyllan A. Gallant, Betar M. Gigan, Sylvain de Aguiar, Hilton B. Grimaud, Alexis Proc Natl Acad Sci U S A Physical Sciences Unlike the interface between two immiscible electrolyte solutions (ITIES) formed between water and polar solvents, molecular understanding of the liquid–liquid interface formed for aqueous biphasic systems (ABSs) is relatively limited and mostly relies on surface tension measurements and thermodynamic models. Here, high-resolution Raman imaging is used to provide spatial and chemical resolution of the interface of lithium chloride - lithium bis(trifluoromethanesulfonyl)imide - water (LiCl–LiTFSI–water) and HCl–LiTFSI–water, prototypical salt–salt ABSs found in a range of electrochemical applications. The concentration profiles of both TFSI anions and water are found to be sigmoidal thus not showing any signs of a positive adsorption for both salts and solvent. More striking, however, is the length at which the concentration profiles extend, ranging from 11 to 2 µm with increasing concentrations, compared to a few nanometers for ITIES. We thus reveal that unlike ITIES, salt–salt ABSs do not have a molecularly sharp interface but rather form an interphase with a gradual change of environment from one phase to the other. This knowledge represents a major stepping-stone in the understanding of aqueous interfaces, key for mastering ion or electron transfer dynamics in a wide range of biological and technological settings including novel battery technologies such as membraneless redox flow and dual-ion batteries. National Academy of Sciences 2023-04-17 2023-04-25 /pmc/articles/PMC10151592/ /pubmed/37068232 http://dx.doi.org/10.1073/pnas.2220662120 Text en Copyright © 2023 the Author(s). Published by PNAS. https://creativecommons.org/licenses/by-nc-nd/4.0/This article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND) (https://creativecommons.org/licenses/by-nc-nd/4.0/) .
spellingShingle Physical Sciences
Degoulange, Damien
Pandya, Raj
Deschamps, Michael
Skiba, Dhyllan A.
Gallant, Betar M.
Gigan, Sylvain
de Aguiar, Hilton B.
Grimaud, Alexis
Direct imaging of micrometer-thick interfaces in salt–salt aqueous biphasic systems
title Direct imaging of micrometer-thick interfaces in salt–salt aqueous biphasic systems
title_full Direct imaging of micrometer-thick interfaces in salt–salt aqueous biphasic systems
title_fullStr Direct imaging of micrometer-thick interfaces in salt–salt aqueous biphasic systems
title_full_unstemmed Direct imaging of micrometer-thick interfaces in salt–salt aqueous biphasic systems
title_short Direct imaging of micrometer-thick interfaces in salt–salt aqueous biphasic systems
title_sort direct imaging of micrometer-thick interfaces in salt–salt aqueous biphasic systems
topic Physical Sciences
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10151592/
https://www.ncbi.nlm.nih.gov/pubmed/37068232
http://dx.doi.org/10.1073/pnas.2220662120
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