Solvent dependence of the molecular order in ion-exchanged self-assembled dialkylammonium monolayers on mica studied with soft X-ray absorption

Hähner, Georg; Zwahlen, Mathias; Caseri, Walter

doi:10.1016/j.jcis.2005.04.111

Cited by 6 publications

(1 citation statement)

References 24 publications

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“…However, this consideration obviously does not hold for the results shown in Figure . Hähner et al have studied the structures of the diC n ABr monolayer formed on mica by near edge XAFS spectroscopy and the water contact angle measurement. , They evaluated the disorder of the alkyl chains of diC n ABr molecules adsorbed onto mica in terms of gauche defects, which led to the high anisotropy of the C−H and C−C bonds. The numbers of the gauche defects of C−H and C−C bonds in a diC12A + molecule on mica were determined to be 13.2 and 15.4, respectively, and, similarly, 7.4 and 11.2 for diC16A + and 5.4 and 8.3 for diC18A + , respectively .…”

Section: Resultsmentioning

confidence: 99%

Evacuation of Counteranions from Langmuir Monolayers of Double-Tailed Quaternary Ammonium Ions into Subphase at High Surface Pressures as Studied by Total Reflection X-ray Absorption Spectrometry

Harada

Okada

2009

J. Phys. Chem. C

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Total reflection X-ray absorption fine structure (TR-XAFS) has been utilized for the detailed analyses of the surface aggregation of double-tailed quaternary ammonium ion bromides. TR-XAFS at the Br K-edge gives us information on the population of Br -just below the subphase surface as well as its local structure. The spectra indicate that Br -is almost completely hydrated, even when it is attracted by the compressed monolayer. In addition, the signal intensities obtained for the monolayers of the ammonium amphiphiles with different hydrocarbon chain lengths suggest that the correction for the attenuation of X-rays due to the absorption by the hydrocarbon layer is necessary to obtain a reliable population of Br -on the subphase surface. The correction of the attenuation reveals that the population of Br -is lower than that predicted on the basis of the electrostatic attraction, and that this deviation becomes larger as the monolayer is compressed. These findings can be explained by the submergence of Br -into the subphase when the amphiphiles are substantially in contact with each other upon the compression of the monolayer. This consideration is also supported by the pressure-molecular area (π-A) isotherms.

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Section: Resultsmentioning

confidence: 99%