Influence of Different Anions on the Surface Composition of Ionic Liquids Studied Using ARXPS

Kolbeck, Claudia; Cremer, Till; Lovelock, Kevin R. J.; Paape, Natalia; Schulz, Peter S.; Wasserscheid, Peter; Maier, Florian; Steinruck, Hp-P.

doi:10.1021/jp902978r

Cited by 175 publications

(296 citation statements)

References 53 publications

(161 reference statements)

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“…IL1 has already been discussed in literature 44, 45, 46. For this IL, a significant increase of the C alkyl is observed at 80°, that is, the signal at 80° increases by about 22 % (see SI, Figure S1).…”

Section: Resultssupporting

confidence: 55%

“…The neat IL1 and IL2 have already been studied in detail in the past, and a pronounced protruding of the alkyl chains towards the vacuum has consistently been reported 44, 45, 46. On the other hand, we are not aware of any previous XPS studies of IL3, which contains the very specific [(MeO) 2 Im] + cation.…”

Section: Resultsmentioning

confidence: 91%

“…While the spectra of IL1 have already been discussed in the past,44, 45, 46 the spectra of IL3, [(MeO) 2 Im][PF 6 ], and to some extent also IL2 and IL4, [Me(EG) 2 C 1 Im][Tf 2 N], are presented in Figure 1 for the first time; in case of IL4, the very similar IL 1‐[2‐(2‐Ethoxyethoxy)ethyl]‐3‐methylimidazolium bis‐[(trifluoromethyl)sulfonyl]imide ([Et(EG) 2 C 1 Im][Tf 2 N]), that is, an IL with an ethyl instead of a methyl group as end group of the long side chain, has already been discussed in detail in ref [47].…”

Section: Resultsmentioning

confidence: 99%

“…[(MeO) 2 Im][PF 6 ] was synthesized with a purity of >99 % 37,38. [Me(EG) 2 C 1 Im][Tf 2 N] and [C 8 C 1 Im][Tf 2 N] were synthesized as was published earlier;45,47 the PEG‐functionalized IL [Me(EG) 2 C 1 Im] [Tf 2 N] was used for comparison of binding energy positions. [(MeO) 2 Im][PF 6 ] shows a minor contamination in its solid state at room temperature, which almost disappears by heating the sample to 90 °C.…”

Section: Methodsmentioning

confidence: 99%

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Surface Enrichment in Equimolar Mixtures of Non‐Functionalized and Functionalized Imidazolium‐Based Ionic Liquids

et al. 2018

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For equimolar mixtures of ionic liquids with imidazolium‐based cations of very different electronic structure, we observe very pronounced surface enrichment effects by angle‐resolved X‐ray photoelectron spectroscopy (XPS). For a mixture with the same anion, that is, 1‐methyl‐3‐octylimidazolium hexafluorophosphate+1,3‐di(methoxy)imidazolium hexafluorophosphate ([C8C1Im][PF6]+[(MeO)2Im][PF6]), we find a strong enrichment of the octyl chain‐containing [C8C1Im]+ cation and a corresponding depletion of the [(MeO)2Im]+ cation in the topmost layer. For a mixture with different cations and anions, that is, [C8C1Im][Tf2N]+[(MeO)2Im][PF6], we find both surface enrichment of the [C8C1Im]+ cation and the [Tf2N]− (bis[(trifluoromethyl)sulfonyl]imide) anion, while [(MeO)2Im]+ and [PF6]− are depleted from the surface. We propose that the observed behavior in these mixtures is due to a lowering of the surface tension by the enriched components. Interestingly, we observe pronounced differences in the chemical shifts of the imidazolium ring signals of the [(MeO)2Im]+ cations as compared to the non‐functionalized cations. Calculations of the electronic structure and the intramolecular partial charge distribution of the cations contribute to interpreting these shifts for the two different cations.

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Section: Resultssupporting

confidence: 55%

Section: Resultsmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Surface Enrichment in Equimolar Mixtures of Non‐Functionalized and Functionalized Imidazolium‐Based Ionic Liquids

et al. 2018

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“…Kolbeck et al observed spectral changes in their XPS measurements for many [OMIm]-based ILs after extended exposure to X-rays. 13 Most changes appeared in the N1s region at binding energies lower than that of the imidazolium nitrogen. They also suggested the presence of uncharged decomposition products.…”

Section: This Journal Is C the Owner Societies 2011mentioning

confidence: 99%

Changes of the near-surface chemical composition of the 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide room temperature ionic liquid under the influence of irradiation

Keppler

Himmerlich

Ikari

et al. 2011

Phys. Chem. Chem. Phys.

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"This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively." Keppler, Angela; Himmerlich, Marcel; Ikari, Tomonori; Marschewski, Marcel; Pachomow, Evgenij; Höfft, Oliver; Maus-Friedrichs, Wolfgang; Endres, Frank; Krischok, Stefan Radiation induced degradation effects are studied for a model ionic liquid (IL) - [EMIm]Tf 2 N -in order to distinguish in which way the results of X-ray based material analysis methods can be falsified by the radiation supplied by typical X-ray sources itself. Photoelectron spectroscopy is commonly used for determining the electronic structure of ionic liquids. Degradation effects, which often occur e.g. in organic materials during X-ray or electron irradiation, are potentially critical for the interpretation of data obtained from ionic liquids. The changes of the chemical composition as well as the radiation-induced desorption of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIm]Tf 2 N) fragments are analysed by X-ray photoelectron spectroscopy (XPS) as well as quadrupole mass spectroscopy (QMS) upon exposure to monochromated or non-monochromated AlKa X-rays from typical laboratory sources. During the irradiation of [EMIm]Tf 2 N, an increasing carbon concentration is observed in both cases and especially the [Tf 2 N] À ion is strongly altered. This observation is supported by the results from the QMS analysis which revealed a variety of different IL fragments that are desorbed during X-ray irradiation. It is shown that the decomposition rate is directly linked to the photon flux on the sample and hence has to be considered when planning an XPS experiment. However, for typical experiments on this particular IL the measurements suggest that the changes are on a larger time scale as typically required for spectra acquisition, in particular if monochromated X-ray sources are used.

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Interfaces of Ionic Liquids (2)

Hayes

Wakeham

2012

Ionic Liquids Uncoiled

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Influence of Different Anions on the Surface Composition of Ionic Liquids Studied Using ARXPS

Cited by 175 publications

References 53 publications

Surface Enrichment in Equimolar Mixtures of Non‐Functionalized and Functionalized Imidazolium‐Based Ionic Liquids

Surface Enrichment in Equimolar Mixtures of Non‐Functionalized and Functionalized Imidazolium‐Based Ionic Liquids

Changes of the near-surface chemical composition of the 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide room temperature ionic liquid under the influence of irradiation

Interfaces of Ionic Liquids (2)

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