Miscibility and distribution of counterions of imidazolium ionic liquid mixtures at the air/water surface

Kei Shimamoto, Asuka Onohara, Hiroki Takumi, Iwao Watanabe, Hajime Tanida, Hiroki Matsubara, Takanori Takiue, Makoto Aratono

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

The miscibility and distribution of Br- and BF4 - ions of imidazolium ionic liquid mixtures, l-hexyl-3- methylimidazolium bromide (HMIMBr) + l-hexyl-3-methylimidazolium tetrafluoroborate (HMIMBF4), at the air/water surface were investigated by surface tensiometry and the total-reflection XAFS (TRXAFS) method. Tensiometry showed that the surface density Of BF4 - was much larger than that of Br-, the adsorbed films of the HMIMBr-HMIMBF4 mixture were greatly enriched in BF 4- at all surface tensions, and the excess Gibbs energy of adsorption was positive. However, TRXAFS revealed that the Br ions were all in the free-Br state solvated by six water molecules in the mixed adsorbed film. Entropy-originated nonideal mixing, where a kind of segregation of the counterion distribution takes place in the interfacial region, was suggested in the mixture.

Original languageEnglish
Pages (from-to)9954-9959
Number of pages6
JournalLangmuir
Volume25
Issue number17
DOIs
Publication statusPublished - Sep 1 2009

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Ionic Liquids
surface water
Ionic liquids
solubility
Solubility
Bromides
Water
bromides
air
liquids
Air
Ions
Gibbs free energy
Surface tension
interfacial tension
ions
Entropy
entropy
Adsorption
Molecules

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

Cite this

Miscibility and distribution of counterions of imidazolium ionic liquid mixtures at the air/water surface. / Shimamoto, Kei; Onohara, Asuka; Takumi, Hiroki; Watanabe, Iwao; Tanida, Hajime; Matsubara, Hiroki; Takiue, Takanori; Aratono, Makoto.

In: Langmuir, Vol. 25, No. 17, 01.09.2009, p. 9954-9959.

Research output: Contribution to journalArticle

Shimamoto, Kei ; Onohara, Asuka ; Takumi, Hiroki ; Watanabe, Iwao ; Tanida, Hajime ; Matsubara, Hiroki ; Takiue, Takanori ; Aratono, Makoto. / Miscibility and distribution of counterions of imidazolium ionic liquid mixtures at the air/water surface. In: Langmuir. 2009 ; Vol. 25, No. 17. pp. 9954-9959.
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AU - Tanida, Hajime

AU - Matsubara, Hiroki

AU - Takiue, Takanori

AU - Aratono, Makoto

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N2 - The miscibility and distribution of Br- and BF4 - ions of imidazolium ionic liquid mixtures, l-hexyl-3- methylimidazolium bromide (HMIMBr) + l-hexyl-3-methylimidazolium tetrafluoroborate (HMIMBF4), at the air/water surface were investigated by surface tensiometry and the total-reflection XAFS (TRXAFS) method. Tensiometry showed that the surface density Of BF4 - was much larger than that of Br-, the adsorbed films of the HMIMBr-HMIMBF4 mixture were greatly enriched in BF 4- at all surface tensions, and the excess Gibbs energy of adsorption was positive. However, TRXAFS revealed that the Br ions were all in the free-Br state solvated by six water molecules in the mixed adsorbed film. Entropy-originated nonideal mixing, where a kind of segregation of the counterion distribution takes place in the interfacial region, was suggested in the mixture.

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