Electro-responsivity of ionic liquid boundary layers in a polar solvent revealed by neutron reflectanceShow others and affiliations
2018 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 148, no 19, article id 193806Article in journal (Refereed) Published
Abstract [en]
Using neutron reflectivity, the electro-responsive structuring of the non-halogenated ionic liquid (IL) trihexyl(tetradecyl)phosphonium-bis(mandelato)borate, [P6,6,6,14][BMB], has been studied at a gold electrode surface in a polar solvent. For a 20% w/w IL mixture, contrast matched to the gold surface, distinct Kiessig fringes were observed for all potentials studied, indicative of a boundary layer of different composition to that of the bulk IL-solvent mixture. With applied potential, the amplitudes of the fringes from the gold-boundary layer interface varied systematically. These changes are attributable to the differing ratios of cations and anions in the boundary layer, leading to a greater or diminished contrast with the gold electrode, depending on the individual ion scattering length densities. Such electro-responsive changes were also evident in the reflectivities measured for the pure IL and a less concentrated (5% w/w) IL-solvent mixture at the same applied potentials, but gave rise to less pronounced changes. These measurements, therefore, demonstrate the enhanced sensitivity achieved by contrast matching the bulk solution and that the structure of the IL boundary layers formed in mixtures is strongly influenced by the bulk concentration. Together these results represent an important step in characterising IL boundary layers in IL-solvent mixtures and provide clear evidence of electro-responsive structuring of IL ions in their solutions with applied potential.
Place, publisher, year, edition, pages
2018. Vol. 148, no 19, article id 193806
Keywords [en]
Electrodes, Gold, Ionic liquids, Ions, Mixtures, Reflection, Solvents, Applied potentials, Bulk concentration, Contrast matching, Enhanced sensitivity, Liquid boundary layers, Neutron reflectance, Neutron reflectivity, Solvent mixtures, Boundary layers
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:ri:diva-33422DOI: 10.1063/1.5001551Scopus ID: 2-s2.0-85041289749OAI: oai:DiVA.org:ri-33422DiVA, id: diva2:1189151
2018-03-092018-03-092023-05-25Bibliographically approved