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From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
Adsorbed and near surface structure of ionic liquids at a solid interface
Juan José Segura1, Aaron Elbourne, Erica J Wanless
1Department of Materials Science and Engineering, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland.
Physical Chemistry Chemical Physics : PCCP
|January 31, 2013
Summary
Atomic force microscopy revealed distinct self-assembly structures at solid-ionic liquid interfaces. Ethylammonium nitrate (EAN) forms the smallest imaged aggregates, while EMIm TFSI shows templated cation adsorption.
Area of Science:
- Surface Science
- Materials Chemistry
- Physical Chemistry
Background:
- Understanding solid-ionic liquid (IL) interfaces is crucial for applications in electrochemistry and materials science.
- The bulk structure of ILs, whether protic or aprotic, can influence their interfacial organization.
- Atomic force microscopy (AFM) offers high-resolution imaging capabilities for interfacial studies.
Purpose of the Study:
- To characterize the lateral structure of ionic liquids (ILs) adsorbed onto solid surfaces using advanced AFM techniques.
- To compare the interfacial behavior of a protic IL (ethylammonium nitrate, EAN) and an aprotic IL (1-ethyl-3-methylimidazolium bis(trifluoro-methylsulfonyl)imide, EMIm TFSI).
- To elucidate the influence of bulk liquid morphology and IL class on surface organization.
Main Methods:
- Employing soft contact and amplitude-modulation (AM) AFM imaging techniques.
- Utilizing tip pressures optimized for the specific solid-IL interface.
- Characterizing the adsorption of EAN and EMIm TFSI onto mica surfaces.
Main Results:
- Ethylammonium nitrate (EAN) self-assembles into unique worm-like structures at the solid-liquid interface, representing the smallest imaged self-assembled aggregates.
- 1-ethyl-3-methylimidazolium bis(trifluoro-methylsulfonyl)imide (EMIm TFSI) cations adsorb in a more isolated manner, arranged in rows templated by the mica surface.
- Comparison highlights how the distinct bulk structures of EAN (nanostructured sponge phase) and EMIm TFSI (weak/absent bulk structure) dictate their interfacial organization.
Conclusions:
- The study demonstrates that AFM can provide unprecedented clarity in characterizing solid-IL interfaces.
- The strength of bulk liquid morphology significantly impacts the lateral organization at the interface.
- Distinct self-assembly behaviors are observed for protic (EAN) and aprotic (EMIm TFSI) ILs at the solid-liquid interface.
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