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Anomalous surface behavior of hydrated guanidinium ions due to ion pairing

Ekholm, Victor; Vazdar, Mario; Mason, Philip E.; Bialik, Erik LU ; Walz, Marie Madeleine; Öhrwall, Gunnar LU ; Werner, Josephina; Rubensson, Jan Erik; Jungwirth, Pavel and Björneholm, Olle LU (2018) In Journal of Chemical Physics 148(14).
Abstract

Surface affinity of aqueous guanidinium chloride (GdmCl) is compared to that of aqueous tetrapropylammonium chloride (TPACl) upon addition of sodium chloride (NaCl) or disodium sulfate (Na2SO4). The experimental results have been acquired using the surface sensitive technique X-ray photoelectron spectroscopy on a liquid jet. Molecular dynamics simulations have been used to produce radial distribution functions and surface density plots. The surface affinities of both TPA+ and Gdm+ increase upon adding NaCl to the solution. With the addition of Na2SO4, the surface affinity of TPA+ increases, while that of Gdm+ decreases. From the results of MD... (More)

Surface affinity of aqueous guanidinium chloride (GdmCl) is compared to that of aqueous tetrapropylammonium chloride (TPACl) upon addition of sodium chloride (NaCl) or disodium sulfate (Na2SO4). The experimental results have been acquired using the surface sensitive technique X-ray photoelectron spectroscopy on a liquid jet. Molecular dynamics simulations have been used to produce radial distribution functions and surface density plots. The surface affinities of both TPA+ and Gdm+ increase upon adding NaCl to the solution. With the addition of Na2SO4, the surface affinity of TPA+ increases, while that of Gdm+ decreases. From the results of MD simulations it is seen that Gdm+ and SO42- ions form pairs. This finding can be used to explain the decreased surface affinity of Gdm+ when co-dissolved with SO42- ions. Since SO42- ions avoid the surface due to the double charge and strong water interaction, the Gdm+-SO42- ion pair resides deeper in the solutions' bulk than the Gdm+ ions. Since TPA+ does not form ion pairs with SO42-, the TPA+ ions are instead enriched at the surface.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Chemical Physics
volume
148
issue
14
publisher
American Institute of Physics
external identifiers
  • scopus:85045434311
ISSN
0021-9606
DOI
10.1063/1.5024348
language
English
LU publication?
yes
id
09636c62-f67d-4fb9-8598-a81fe2636834
date added to LUP
2018-04-26 15:30:31
date last changed
2019-01-14 07:39:50
@article{09636c62-f67d-4fb9-8598-a81fe2636834,
  abstract     = {<p>Surface affinity of aqueous guanidinium chloride (GdmCl) is compared to that of aqueous tetrapropylammonium chloride (TPACl) upon addition of sodium chloride (NaCl) or disodium sulfate (Na<sub>2</sub>SO<sub>4</sub>). The experimental results have been acquired using the surface sensitive technique X-ray photoelectron spectroscopy on a liquid jet. Molecular dynamics simulations have been used to produce radial distribution functions and surface density plots. The surface affinities of both TPA<sup>+</sup> and Gdm<sup>+</sup> increase upon adding NaCl to the solution. With the addition of Na<sub>2</sub>SO<sub>4</sub>, the surface affinity of TPA<sup>+</sup> increases, while that of Gdm<sup>+</sup> decreases. From the results of MD simulations it is seen that Gdm<sup>+</sup> and SO42- ions form pairs. This finding can be used to explain the decreased surface affinity of Gdm<sup>+</sup> when co-dissolved with SO42- ions. Since SO42- ions avoid the surface due to the double charge and strong water interaction, the Gdm+-SO42- ion pair resides deeper in the solutions' bulk than the Gdm<sup>+</sup> ions. Since TPA<sup>+</sup> does not form ion pairs with SO42-, the TPA<sup>+</sup> ions are instead enriched at the surface.</p>},
  articleno    = {144508},
  author       = {Ekholm, Victor and Vazdar, Mario and Mason, Philip E. and Bialik, Erik and Walz, Marie Madeleine and Öhrwall, Gunnar and Werner, Josephina and Rubensson, Jan Erik and Jungwirth, Pavel and Björneholm, Olle},
  issn         = {0021-9606},
  language     = {eng},
  month        = {04},
  number       = {14},
  publisher    = {American Institute of Physics},
  series       = {Journal of Chemical Physics},
  title        = {Anomalous surface behavior of hydrated guanidinium ions due to ion pairing},
  url          = {http://dx.doi.org/10.1063/1.5024348},
  volume       = {148},
  year         = {2018},
}