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Interfacial Structures of Trihexyltetradecylphosphonium-bis(mandelato)borate Ionic Liquid Confined between Gold Electrodes

Wang, Yong-Lei; Golets, Mikhail; Li, Bin LU ; Sarman, Sten and Laaksonen, Aatto (2017) In ACS Applied Materials and Interfaces 9(5). p.4976-4987
Abstract

Atomistic molecular dynamics simulations have been performed to study microscopic the interfacial ionic structures, molecular arrangements, and orientational preferences of trihexyltetradecylphosphonium-bis(mandelato)borate ([P6,6,6,14][BMB]) ionic liquid confined between neutral and charged gold electrodes. It was found that both [P6,6,6,14] cations and [BMB] anions are coabsorbed onto neutral electrodes at different temperatures. The hexyl and tetradecyl chains in [P6,6,6,14] cations lie preferentially flat on neutral electrodes. The oxalato and phenyl rings in [BMB] anions are characterized by alternative parallel-perpendicular orientations in the mixed innermost ionic layer adjacent to neutral... (More)

Atomistic molecular dynamics simulations have been performed to study microscopic the interfacial ionic structures, molecular arrangements, and orientational preferences of trihexyltetradecylphosphonium-bis(mandelato)borate ([P6,6,6,14][BMB]) ionic liquid confined between neutral and charged gold electrodes. It was found that both [P6,6,6,14] cations and [BMB] anions are coabsorbed onto neutral electrodes at different temperatures. The hexyl and tetradecyl chains in [P6,6,6,14] cations lie preferentially flat on neutral electrodes. The oxalato and phenyl rings in [BMB] anions are characterized by alternative parallel-perpendicular orientations in the mixed innermost ionic layer adjacent to neutral electrodes. An increase in temperature has a marginal effect on the interfacial ionic structures and molecular orientations of [P6,6,6,14][BMB] ionic species in a confined environment. Electrifying gold electrodes leads to peculiar changes in the interfacial ionic structures and molecular orientational arrangements of [P6,6,6,14] cations and [BMB] anions in negatively and positively charged gold electrodes, respectively. As surface charge density increases (but lower than 20 μC/cm2), the layer thickness of the mixed innermost interfacial layer gradually increases due to a consecutive accumulation of [P6,6,6,14] cations and [BMB] anions at negatively and positively charged electrodes, respectively, before the formation of distinct cationic and anionic innermost layers. Meanwhile, the molecular orientations of two oxalato rings in the same [BMB] anions change gradually from a parallel-perpendicular feature to being partially characterized by a tilted arrangement at an angle of 45° from the electrodes and finally to a dominant parallel coordination pattern along positively charged electrodes. Distinctive interfacial distribution patterns are also observed accordingly for phenyl rings that are directly connected to neighboring oxalato rings in [BMB] anions.

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organization
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type
Contribution to journal
publication status
published
subject
keywords
atomistic simulations, gold electrodes, interfacial structures, molecular arrangements, trihexyltetradecylphosphonium-bis(mandelato)borate ionic liquid
in
ACS Applied Materials and Interfaces
volume
9
issue
5
pages
12 pages
publisher
The American Chemical Society
external identifiers
  • scopus:85011994079
  • wos:000393848900080
ISSN
1944-8244
DOI
10.1021/acsami.6b14429
language
English
LU publication?
yes
id
5de02a87-5a0a-4d72-8e2e-06cfe6e59e59
date added to LUP
2017-02-23 07:48:46
date last changed
2018-01-07 11:52:07
@article{5de02a87-5a0a-4d72-8e2e-06cfe6e59e59,
  abstract     = {<p>Atomistic molecular dynamics simulations have been performed to study microscopic the interfacial ionic structures, molecular arrangements, and orientational preferences of trihexyltetradecylphosphonium-bis(mandelato)borate ([P<sub>6,6,6,14</sub>][BMB]) ionic liquid confined between neutral and charged gold electrodes. It was found that both [P<sub>6,6,6,14</sub>] cations and [BMB] anions are coabsorbed onto neutral electrodes at different temperatures. The hexyl and tetradecyl chains in [P<sub>6,6,6,14</sub>] cations lie preferentially flat on neutral electrodes. The oxalato and phenyl rings in [BMB] anions are characterized by alternative parallel-perpendicular orientations in the mixed innermost ionic layer adjacent to neutral electrodes. An increase in temperature has a marginal effect on the interfacial ionic structures and molecular orientations of [P<sub>6,6,6,14</sub>][BMB] ionic species in a confined environment. Electrifying gold electrodes leads to peculiar changes in the interfacial ionic structures and molecular orientational arrangements of [P<sub>6,6,6,14</sub>] cations and [BMB] anions in negatively and positively charged gold electrodes, respectively. As surface charge density increases (but lower than 20 μC/cm<sup>2</sup>), the layer thickness of the mixed innermost interfacial layer gradually increases due to a consecutive accumulation of [P<sub>6,6,6,14</sub>] cations and [BMB] anions at negatively and positively charged electrodes, respectively, before the formation of distinct cationic and anionic innermost layers. Meanwhile, the molecular orientations of two oxalato rings in the same [BMB] anions change gradually from a parallel-perpendicular feature to being partially characterized by a tilted arrangement at an angle of 45° from the electrodes and finally to a dominant parallel coordination pattern along positively charged electrodes. Distinctive interfacial distribution patterns are also observed accordingly for phenyl rings that are directly connected to neighboring oxalato rings in [BMB] anions.</p>},
  author       = {Wang, Yong-Lei and Golets, Mikhail and Li, Bin and Sarman, Sten and Laaksonen, Aatto},
  issn         = {1944-8244},
  keyword      = {atomistic simulations,gold electrodes,interfacial structures,molecular arrangements,trihexyltetradecylphosphonium-bis(mandelato)borate ionic liquid},
  language     = {eng},
  month        = {02},
  number       = {5},
  pages        = {4976--4987},
  publisher    = {The American Chemical Society},
  series       = {ACS Applied Materials and Interfaces},
  title        = {Interfacial Structures of Trihexyltetradecylphosphonium-bis(mandelato)borate Ionic Liquid Confined between Gold Electrodes},
  url          = {http://dx.doi.org/10.1021/acsami.6b14429},
  volume       = {9},
  year         = {2017},
}