Layering of [BMIM]+ -based ionic liquids at a charged sapphire interface

Markus Mezger; Sebastian Schramm; Heiko Schröder; Harald Reichert; Moshe Deutsch; Emerson J. De Souza; John S. Okasinski; Benjamin M. Ocko; Veijo Honkimäki; Helmut Dosch

doi:10.1063/1.3212613

Layering of [BMIM]⁺ -based ionic liquids at a charged sapphire interface

Markus Mezger, Sebastian Schramm, Heiko Schröder, Harald Reichert, Moshe Deutsch, Emerson J. De Souza, John S. Okasinski, Benjamin M. Ocko, Veijo Honkimäki, Helmut Dosch

Department of Physics - at Bar-Ilan University

Research output: Contribution to journal › Article › peer-review

125 Scopus citations

Abstract

The structure of two model room temperature ionic liquids, [BMIM] ⁺ [PF₆]^- and [BMIM]⁺ [BF ₄] ^-, near the solid/liquid interface with charged Al ₂ O₃ (0001) (sapphire) was determined with subnanometer resolution by high energy (72.5 keV) x-ray reflectivity. [BMIM]⁺ [PF₆]^- exhibits alternately charged, exponentially decaying, near-surface layering. By contrast, the smaller-anion compound, [BMIM]⁺ [BF₄] ^-, shows only a single layer of enhanced electron density at the interface. The different layering behaviors, and their characteristic length scales, correspond well to the different bulk diffraction patterns, also measured in this study. Complementary measurements of the surface and interface energies showed no significant different between the two RTILs. The combined bulk-interface results support the conclusion that the interfacial ordering is dominated by the same electrostatic ion-ion interactions dominating the bulk correlations, with hydrogen bonding and dispersion interactions playing only a minor role.

Original language	English
Article number	094701
Journal	Journal of Chemical Physics
Volume	131
Issue number	9
DOIs	https://doi.org/10.1063/1.3212613
State	Published - 2009

Bibliographical note

Funding Information:
We would like to thank the beamline staff at ID15A and ID15B (T. Buslaps, G. Gonzalez Aviles, F. Venturini, and D. Pontoni), as well as H. Müller from the central chemistry laboratory of the ESRF for assistance. We gratefully acknowledge the support by the German-Israeli Foundation for Scientific Research and Development (Grant No. I 779-42.10/2003) and the U.S.-Israel Binational Science Foundation, Jerusalem. B.N.L. was supported by DOE’s Division of Materials Science under Grant No. DE-AC02-76CH0016.

Funding

We would like to thank the beamline staff at ID15A and ID15B (T. Buslaps, G. Gonzalez Aviles, F. Venturini, and D. Pontoni), as well as H. Müller from the central chemistry laboratory of the ESRF for assistance. We gratefully acknowledge the support by the German-Israeli Foundation for Scientific Research and Development (Grant No. I 779-42.10/2003) and the U.S.-Israel Binational Science Foundation, Jerusalem. B.N.L. was supported by DOE’s Division of Materials Science under Grant No. DE-AC02-76CH0016.

Funders	Funder number
DOE’s Division of Materials Science	DE-AC02-76CH0016
German-Israeli Foundation for Scientific Research and Development	779-42.10/2003
United States-Israel Binational Science Foundation

Access to Document

10.1063/1.3212613

Cite this

@article{1e629566fe0b48e8b6235e5fad12959d,

title = "Layering of [BMIM]+ -based ionic liquids at a charged sapphire interface",

abstract = "The structure of two model room temperature ionic liquids, [BMIM] + [PF6]- and [BMIM]+ [BF 4] -, near the solid/liquid interface with charged Al 2 O3 (0001) (sapphire) was determined with subnanometer resolution by high energy (72.5 keV) x-ray reflectivity. [BMIM]+ [PF6]- exhibits alternately charged, exponentially decaying, near-surface layering. By contrast, the smaller-anion compound, [BMIM]+ [BF4] -, shows only a single layer of enhanced electron density at the interface. The different layering behaviors, and their characteristic length scales, correspond well to the different bulk diffraction patterns, also measured in this study. Complementary measurements of the surface and interface energies showed no significant different between the two RTILs. The combined bulk-interface results support the conclusion that the interfacial ordering is dominated by the same electrostatic ion-ion interactions dominating the bulk correlations, with hydrogen bonding and dispersion interactions playing only a minor role.",

author = "Markus Mezger and Sebastian Schramm and Heiko Schr{\"o}der and Harald Reichert and Moshe Deutsch and {De Souza}, {Emerson J.} and Okasinski, {John S.} and Ocko, {Benjamin M.} and Veijo Honkim{\"a}ki and Helmut Dosch",

note = "Funding Information: We would like to thank the beamline staff at ID15A and ID15B (T. Buslaps, G. Gonzalez Aviles, F. Venturini, and D. Pontoni), as well as H. M{\"u}ller from the central chemistry laboratory of the ESRF for assistance. We gratefully acknowledge the support by the German-Israeli Foundation for Scientific Research and Development (Grant No. I 779-42.10/2003) and the U.S.-Israel Binational Science Foundation, Jerusalem. B.N.L. was supported by DOE{\textquoteright}s Division of Materials Science under Grant No. DE-AC02-76CH0016.",

year = "2009",

doi = "10.1063/1.3212613",

language = "אנגלית",

volume = "131",

journal = "Journal of Chemical Physics",

issn = "0021-9606",

publisher = "American Institute of Physics",

number = "9",

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T1 - Layering of [BMIM]+ -based ionic liquids at a charged sapphire interface

AU - Mezger, Markus

AU - Schramm, Sebastian

AU - Schröder, Heiko

AU - Reichert, Harald

AU - Deutsch, Moshe

AU - De Souza, Emerson J.

AU - Okasinski, John S.

AU - Ocko, Benjamin M.

AU - Honkimäki, Veijo

AU - Dosch, Helmut

N1 - Funding Information: We would like to thank the beamline staff at ID15A and ID15B (T. Buslaps, G. Gonzalez Aviles, F. Venturini, and D. Pontoni), as well as H. Müller from the central chemistry laboratory of the ESRF for assistance. We gratefully acknowledge the support by the German-Israeli Foundation for Scientific Research and Development (Grant No. I 779-42.10/2003) and the U.S.-Israel Binational Science Foundation, Jerusalem. B.N.L. was supported by DOE’s Division of Materials Science under Grant No. DE-AC02-76CH0016.

PY - 2009

Y1 - 2009

N2 - The structure of two model room temperature ionic liquids, [BMIM] + [PF6]- and [BMIM]+ [BF 4] -, near the solid/liquid interface with charged Al 2 O3 (0001) (sapphire) was determined with subnanometer resolution by high energy (72.5 keV) x-ray reflectivity. [BMIM]+ [PF6]- exhibits alternately charged, exponentially decaying, near-surface layering. By contrast, the smaller-anion compound, [BMIM]+ [BF4] -, shows only a single layer of enhanced electron density at the interface. The different layering behaviors, and their characteristic length scales, correspond well to the different bulk diffraction patterns, also measured in this study. Complementary measurements of the surface and interface energies showed no significant different between the two RTILs. The combined bulk-interface results support the conclusion that the interfacial ordering is dominated by the same electrostatic ion-ion interactions dominating the bulk correlations, with hydrogen bonding and dispersion interactions playing only a minor role.

AB - The structure of two model room temperature ionic liquids, [BMIM] + [PF6]- and [BMIM]+ [BF 4] -, near the solid/liquid interface with charged Al 2 O3 (0001) (sapphire) was determined with subnanometer resolution by high energy (72.5 keV) x-ray reflectivity. [BMIM]+ [PF6]- exhibits alternately charged, exponentially decaying, near-surface layering. By contrast, the smaller-anion compound, [BMIM]+ [BF4] -, shows only a single layer of enhanced electron density at the interface. The different layering behaviors, and their characteristic length scales, correspond well to the different bulk diffraction patterns, also measured in this study. Complementary measurements of the surface and interface energies showed no significant different between the two RTILs. The combined bulk-interface results support the conclusion that the interfacial ordering is dominated by the same electrostatic ion-ion interactions dominating the bulk correlations, with hydrogen bonding and dispersion interactions playing only a minor role.

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