Bi-layering at ionic liquid surfaces: a sum-frequency generation vibrational spectroscopy- and molecular dynamics simulation-based study

Iwahashi, Takashi; Ishiyama, Tatsuya; Sakai, Yasunari; Morita, Akihiro; Kim, Doseok; Ouchi, Yukio

doi:10.1039/d0cp01219j

Cited by 11 publications

(8 citation statements)

References 50 publications

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“…This is confirmed by visual inspection of individual snapshots (see, e.g., the relevant panels of Figure or ). Such multilayer ordering is consistent with independent MD simulations, confirmed by X-ray scattering and SFG measurements, on related systems. − …”

Section: Discussionsupporting

confidence: 86%

“…The breadth of this secondary CT peak suggests that although predominantly inward-pointing, the alkyl chains adopt a wide range of orientations. This is also plausible based on simulations of related systems …”

Section: Discussionmentioning

confidence: 71%

“…Such multilayer ordering is consistent with independent MD simulations, confirmed by X-ray scattering and SFG measurements, on related systems. 113 − 116 …”

Section: Discussionmentioning

confidence: 99%

“…This is also plausible based on simulations of related systems. 116 In this absence of any obvious anomalies and barring any undetected errors in the way the MD simulations have been carried out, one remaining possibility within explanation (2) is that the nonpolarizable OPLS-AA/CL&P force fields do not give an accurate representation of the surfaces of these mixed alkyl/fluoro systems. The developers of the OPLS-AA/CL&P framework have recently described its extension to include explicit polarizability using an approach based on Drude dipoles (also known as a "core−shell" model); they have demonstrated its application to the bulk structures of selected ILs.…”

Section: ■ Discussionmentioning

confidence: 99%

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Surface Structure of Alkyl/Fluoroalkylimidazolium Ionic–Liquid Mixtures

et al. 2022

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The gas–liquid interface of ionic liquids (ILs) is critically important in many applications, for example, in supported IL phase (SILP) catalysis. Methods to investigate the interfacial structure in these systems will allow their performance to be improved in a rational way. In this study, reactive-atom scattering (RAS), surface tension measurements, and molecular dynamics (MD) simulations were used to study the vacuum interface of mixtures of partially fluorinated and normal alkyl ILs. The underlying aim was to understand whether fluorinated IL ions could be used as additives to modify the surface structure of one of the most widely used families of alkyl ILs. The series of ILs 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C n mim][Tf 2 N]) with n = 4–12 were mixed with a fixed-length, semiperfluorinated analogue (1 H ,1 H ,2 H ,2 H -perfluorooctyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C 8 mimF 13 ][Tf 2 N]), forming [C n mim] (1– x ) [C 8 mimF 13 ] x [Tf 2 N] mixtures, where x is the bulk mole fraction of the fluorinated component. The RAS-LIF method combined O-atom projectiles with laser-induced fluorescence (LIF) detection of the product OH as a measure of surface exposure of the alkyl chains. For [C 8 mim] (1– x ) [C 8 mimF 13 ] x [Tf 2 N] mixtures, RAS-LIF OH yields are below those expected from stoichiometry. There are quantitatively consistent negative deviations from linearity of the surface tension. Both results imply that the lower-surface-tension fluoroalkyl material dominates the surface. A similar deficit is found for alkyl chain lengths n = 4, 6, 8, and 12 and for all (nonzero) x investigated by RAS-LIF. Accessible-surface-area (ASA) analyses of the MD simulations for [C n mim] (1– x ) [C 8 mimF 13 ] x [Tf 2 N] mixtures qualitatively reproduce the same primary effect of fluoro-chain predominance of the surface over most of the range of n . However, there are significant quantitative discrepancies between MD ASA predictions and experiment relating to the strength of any n -dependence of the relative alkyl coverage at fixed x , and on the x -dependence at fixed ...

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Section: Discussionsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 71%

“…Such multilayer ordering is consistent with independent MD simulations, confirmed by X-ray scattering and SFG measurements, on related systems. 113 − 116 …”

Section: Discussionmentioning

confidence: 99%

Section: ■ Discussionmentioning

confidence: 99%

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Surface Structure of Alkyl/Fluoroalkylimidazolium Ionic–Liquid Mixtures

et al. 2022

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“…Therefore, the structure of the vacuum/IL interface has been in the center of surface science investigations using different techniques like molecular dynamics calculations, [21] X-ray reflectivity, [22] direct recoil spectrometry, [23] Rutherford backscattering, [23b,24] low energy ion scattering, [25] reactive atom scattering, [26] sum frequency generation vibrational spectroscopy [27] and X-ray photoelectron spectroscopy (XPS). [28] Thereby, a good understanding of the static properties of this interface has been obtained.…”

Section: Introductionmentioning

confidence: 99%

n‐Butane, iso‐Butane and 1‐Butene Adsorption on Imidazolium‐Based Ionic Liquids Studied with Molecular Beam Techniques

Winter

Bhuin

Maier

et al. 2021

Chemistry A European J

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The interaction of molecules, especially hydrocarbons, at the gas/ionic liquid (IL) surface plays a crucial role in supported IL catalysis. The dynamics of this process is investigated by measuring the trapping probabilities of nbutane, iso-butane and 1-butene on a set of frozen 1-alkyl-3methylimidazolium-based ILs [C n C 1 Im]X, where n = 4, 8 and X À =Cl À , Br À , [PF 6 ] À and [Tf 2 N] À . The decrease of the initial trapping probability with increasing surface temperature is used to determine the desorption energy of the hydrocarbons at the IL surfaces. It increases with increasing alkyl chain length n and decreasing anion size for the ILs studied. We attribute these effects to different degrees of alkyl chain surface enrichment, while interactions between the adsorbate and the anion do not play a significant role. The adsorption energy also depends on the adsorbing molecule: It decreases in the order n-butane > 1-butene > iso-butane, which can be explained by different dispersion interactions.

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Solid-liquid interfacial nanostructure of ionic liquids and deep eutectic solvents

Elbourne,

Awad,

Meredith

et al. 2024

Encyclopedia of Solid-Liquid Interfaces

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Bi-layering at ionic liquid surfaces: a sum-frequency generation vibrational spectroscopy- and molecular dynamics simulation-based study

Abstract: IV-SFG vibrational spectroscopy and MD simulation studies successfully demonstrate the presence of a “head-to-head” bi-layer structure at ionic liquid surfaces.

Cited by 11 publications

References 50 publications

Surface Structure of Alkyl/Fluoroalkylimidazolium Ionic–Liquid Mixtures

Surface Structure of Alkyl/Fluoroalkylimidazolium Ionic–Liquid Mixtures

n‐Butane, iso‐Butane and 1‐Butene Adsorption on Imidazolium‐Based Ionic Liquids Studied with Molecular Beam Techniques

Solid-liquid interfacial nanostructure of ionic liquids and deep eutectic solvents

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