Jump to main content
Jump to site search


Determining the composition of the vacuum–liquid interface in ionic-liquid mixtures

Author affiliations

Abstract

The vacuum–liquid interfaces of a number of ionic-liquid mixtures have been investigated using the combination of reactive-atom scattering with laser-induced fluorescence detection (RAS-LIF), selected surface tension measurements, and molecular dynamics (MD) simulations. The mixtures are based on the widespread 1-alkyl-3-methylimidazolium ([Cnmim]+) cation, including mixed cations which differ in chain length or chemical functionality with a common anion; and different anions for a common cation. RAS-LIF results imply that the surface compositions exhibit a general form of non-stoichiometric behaviour that mimics the well-known Henry’s and Raoult’s laws at low and high mole fraction, respectively. The extended Langmuir model provides a moderately good single-parameter fit, but higher-order terms are required for an accurate description. The quantitative relationship between RAS-LIF and surface tension, which probes the surface composition only indirectly, is explored for mixtures of [C2mim]+ and [C12mim]+ with a common bis(trifluoromethylsulfonyl)imide ([NTf2]) anion. Extended Langmuir model fits to surface tension data are broadly consistent with those to RAS-LIF; however, several other common approaches to extracting surface compositions from measured surface tensions result in much larger discrepancies. MD simulations suggest that RAS-LIF faithfully reports on the alkyl-chain exposure at the surface, which is only subtly modified by composition-dependent structural reorganisation.

Graphical abstract: Determining the composition of the vacuum–liquid interface in ionic-liquid mixtures

Back to tab navigation

Supplementary files

Publication details

The article was received on 22 May 2017, accepted on 09 Jun 2017 and first published on 14 Jun 2017


Article type: Paper
DOI: 10.1039/C7FD00175D
Citation: Faraday Discuss., 2018, Advance Article
  •   Request permissions

    Determining the composition of the vacuum–liquid interface in ionic-liquid mixtures

    E. J. Smoll, M. A. Tesa-Serrate, S. M. Purcell, L. D’Andrea, D. W. Bruce, J. M. Slattery, M. L. Costen, T. K. Minton and K. G. McKendrick, Faraday Discuss., 2018, Advance Article , DOI: 10.1039/C7FD00175D

Search articles by author

Spotlight

Advertisements