Molecular layering of fluorinated ionic liquids at a charged sapphire (0001) surface

Markus Mezger; Heiko Schröder; Harald Reichert; Sebastian Schramm; John S. Okasinski; Sebastian Schöder; Veijo Honkimäki; Moshe Deutsch; Benjamin M. Ocko; John Ralston; Michael Rohwerder; Martin Stratmann; Helmut Dosch

doi:10.1126/science.1164502

Molecular layering of fluorinated ionic liquids at a charged sapphire (0001) surface

Markus Mezger, Heiko Schröder, Harald Reichert, Sebastian Schramm, John S. Okasinski, Sebastian Schöder, Veijo Honkimäki, Moshe Deutsch, Benjamin M. Ocko, John Ralston, Michael Rohwerder, Martin Stratmann, Helmut Dosch

Department of Physics

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

566 Scopus citations

Abstract

Room-temperature ionic liquids (RTILs) are promising candidates for a broad range of "green" applications, for which their interaction with solid surfaces plays a crucial role. In this high-energy x-ray reflectivity study, the temperature-dependent structures of three ionic liquids with the tris(pentafluoroethyl)trifluorophosphate anion in contact with a charged sapphire substrate were investigated with submolecular resolution. All three RTILs show strong interfacial layering, starting with a cation layer at the substrate and decaying exponentially into the bulk liquid. The observed decay length and layering period point to an interfacial ordering mechanism, akin to the charge inversion effect, which is suggested to originate from strong correlations between the unscreened ions. The observed layering is expected to be a generic feature of RTILs at charged interfaces.

Original language	English
Pages (from-to)	424-428
Number of pages	5
Journal	Science
Volume	322
Issue number	5900
DOIs	https://doi.org/10.1126/science.1164502
State	Published - 17 Oct 2008

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abstract = "Room-temperature ionic liquids (RTILs) are promising candidates for a broad range of {"}green{"} applications, for which their interaction with solid surfaces plays a crucial role. In this high-energy x-ray reflectivity study, the temperature-dependent structures of three ionic liquids with the tris(pentafluoroethyl)trifluorophosphate anion in contact with a charged sapphire substrate were investigated with submolecular resolution. All three RTILs show strong interfacial layering, starting with a cation layer at the substrate and decaying exponentially into the bulk liquid. The observed decay length and layering period point to an interfacial ordering mechanism, akin to the charge inversion effect, which is suggested to originate from strong correlations between the unscreened ions. The observed layering is expected to be a generic feature of RTILs at charged interfaces.",

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T1 - Molecular layering of fluorinated ionic liquids at a charged sapphire (0001) surface

AU - Mezger, Markus

AU - Schröder, Heiko

AU - Reichert, Harald

AU - Schramm, Sebastian

AU - Okasinski, John S.

AU - Schöder, Sebastian

AU - Honkimäki, Veijo

AU - Deutsch, Moshe

AU - Ocko, Benjamin M.

AU - Ralston, John

AU - Rohwerder, Michael

AU - Stratmann, Martin

AU - Dosch, Helmut

PY - 2008/10/17

Y1 - 2008/10/17

N2 - Room-temperature ionic liquids (RTILs) are promising candidates for a broad range of "green" applications, for which their interaction with solid surfaces plays a crucial role. In this high-energy x-ray reflectivity study, the temperature-dependent structures of three ionic liquids with the tris(pentafluoroethyl)trifluorophosphate anion in contact with a charged sapphire substrate were investigated with submolecular resolution. All three RTILs show strong interfacial layering, starting with a cation layer at the substrate and decaying exponentially into the bulk liquid. The observed decay length and layering period point to an interfacial ordering mechanism, akin to the charge inversion effect, which is suggested to originate from strong correlations between the unscreened ions. The observed layering is expected to be a generic feature of RTILs at charged interfaces.

AB - Room-temperature ionic liquids (RTILs) are promising candidates for a broad range of "green" applications, for which their interaction with solid surfaces plays a crucial role. In this high-energy x-ray reflectivity study, the temperature-dependent structures of three ionic liquids with the tris(pentafluoroethyl)trifluorophosphate anion in contact with a charged sapphire substrate were investigated with submolecular resolution. All three RTILs show strong interfacial layering, starting with a cation layer at the substrate and decaying exponentially into the bulk liquid. The observed decay length and layering period point to an interfacial ordering mechanism, akin to the charge inversion effect, which is suggested to originate from strong correlations between the unscreened ions. The observed layering is expected to be a generic feature of RTILs at charged interfaces.

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Molecular layering of fluorinated ionic liquids at a charged sapphire (0001) surface

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