title: Nanoscale capillary freezing of ionic liquids confined between metallic interfaces and the role of electronic screening.
abstract: Room-temperature ionic liquids (RTILs) are new materials with fundamental importance for energy storage and active lubrication. They are unusual liquids, which challenge the classical frameworks of electrolytes, whose behaviour at electrified interfaces remains elusive, with exotic responses relevant to their electrochemical activity. Using tuning-fork-based atomic force microscope nanorheological measurements, we explore here the properties of confined RTILs, unveiling a dramatic change of the RTIL towards a solid-like phase below a threshold thickness, pointing to capillary freezing in confinement. This threshold is related to the metallic nature of the confining materials, with more metallic surfaces facilitating freezing. This behaviour is interpreted in terms of the shift of the freezing transition, taking into account the influence of the electronic screening on RTIL wetting of the confining surfaces. Our findings provide fresh views on the properties of confined RTIL with implications for their properties inside nanoporous metallic structures, and suggests applications to tune nanoscale lubrication with phase-changing RTILs, by varying the nature and patterning of the substrate, and application of active polarization.
authors.affiliation: Laboratoire de Physique Statistique, Ecole Normale Supérieure, UMR CNRS 8550, PSL Research University, 75005 Paris Cedex 05, France.
authors.forename: Jean
authors.initials: J
authors.lastname: Comtet
authors.affiliation: Laboratoire de Physique Statistique, Ecole Normale Supérieure, UMR CNRS 8550, PSL Research University, 75005 Paris Cedex 05, France.
authors.forename: Antoine
authors.initials: A
authors.lastname: Niguès
authors.affiliation: Laboratoire de Physique Statistique, Ecole Normale Supérieure, UMR CNRS 8550, PSL Research University, 75005 Paris Cedex 05, France.
authors.forename: Vojtech
authors.identifier: 0000-0002-6129-4618
authors.initials: V
authors.lastname: Kaiser
authors.affiliation: Laboratoire Interdisciplinaire de Physique, CNRS and Université Grenoble Alpes, UMR CNRS 5588, 38000 Grenoble, France.
authors.forename: Benoit
authors.initials: B
authors.lastname: Coasne
authors.affiliation: Laboratoire de Physique Statistique, Ecole Normale Supérieure, UMR CNRS 8550, PSL Research University, 75005 Paris Cedex 05, France.
authors.forename: Lydéric
authors.identifier: 0000-0003-3577-5335
authors.initials: L
authors.lastname: Bocquet
authors.affiliation: Laboratoire de Physique Statistique, Ecole Normale Supérieure, UMR CNRS 8550, PSL Research University, 75005 Paris Cedex 05, France.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Siria