Surface layering and melting in an ionic liquid studied by resonant soft X-ray reflectivity.
basic_science · Level V
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- Record sourced from PubMed, PMID 23431181.
- Also identified by DOI 10.1073/pnas.1211749110 and PMC identifier 3593890.
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Abstract
The molecular-scale structure of the ionic liquid [C18mim](+)[FAP](-) near its free surface was studied by complementary methods. X-ray absorption spectroscopy and resonant soft X-ray reflectivity revealed a depth-decaying near-surface layering. Element-specific interfacial profiles were extracted with submolecular resolution from energy-dependent soft X-ray reflectivity data. Temperature-dependent hard X-ray reflectivity, small- and wide-angle X-ray scattering, and infrared spectroscopy uncovered an intriguing melting mechanism for the layered region, where alkyl chain melting drove a negative thermal expansion of the surface layer spacing.