Structural anomalies of Rb and Br ionic nanosolutions in hydrophobic slit-shaped solid space as revealed by the EXAFS technique

Takahiro Ohkubo, Yoshiyuki Hattori, Hirofumi Kanoh, Takehisa Konishi, Takashi Fujikawa, Katsumi Kaneko

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Abstract

The hydration structure of RbBr electrolytic solutions confined in slit-shaped nanospaces of carbon was determined with the extended X-ray absorption fine structure (EXAFS) technique and related analysis. The nitrogen adsorption isotherms at 77 K were measured to evaluate the porosity of RbBr-deposited carbon samples. The EXAFS results indicate that the electrolytic solution confined in hydrophobic nanospaces has a restricted hydration structure depending on the average pore width of the nanospaces. Also the asymmetric-field effect of slit-pore geometry on the formation of unique hydration structures of ions in nanospaces was unveiled with the analysis of EXAFS spectra. A marked decrease of the hydration number around a Rb ion was observed in slit-shaped nanospaces, indicating the compressed hydration structure around a Rb ion restricted in slit-shaped nanospaces. The distorted hydration structure around a Br ion in the slit-shaped pore of 0.7 nm was formed to increase the hydration number, though partially dehydrated structure can be formed in a 1.1-nm pore. The cluster-mediated ordered structure of water molecules can play an important role in forming a dehydrated structure around a Br ion confined in the 1.1-nm pore.

Original languageEnglish
Pages (from-to)13616-13622
Number of pages7
JournalJournal of Physical Chemistry B
Volume107
Issue number49
Publication statusPublished - Dec 11 2003
Externally publishedYes

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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