Structure and transport in 2D-nanoconfined electrolytes - Damien Toquer (ENS Paris)

Recent experimental advances in nanofluidics have enabled the exploration of ion transport across molecular-scale pores. Conductance and flow measurements show that electrostatic coupling between the ions and the confining walls plays a major role. Despite these advances, direct measurements of ionic behaviour in such small systems remain challenging. Numerical simulations and theoretical modelling help break down complex phenomena into simple physical ingredients.

I will first show that the electrostatic interactions between the ions are enhanced by the confinement of the electric field. As a result, the ions become strongly correlated over long distances. One consequence of these correlations is ionic pairing, which suppresses linear ionic conduction at low voltage drop, in accord with experiments in MoS2 nanochannels. This effect shows promising applications in the active domain of ionic memristors. [1]

I will then show that those strong correlations allow the emergence of collective charge fluctuations of the ions. Those fluctuation modes can couple with plasmonic modes in the solid, and directly affect the transport properties of the flow, in particular in systems with a strong physisorbed surface charge. This paves the way for smart tuning of liquid transport by solid engineering, with possible applications to ion separation and desalination technologies. [2]

[1] Damien Toquer, Lydéric Bocquet, Paul Robin; Ionic association and Wien effect in 2D confined electrolytes. J. Chem. Phys. 14 February 2025; 162 (6): 064703. https://doi.org/10.1063/5.0241949
[2] Damien Toquer, Baptiste Coquinot, Nikita Kavokine, Lydéric Bocquet [In preparation]

Contact: Simon Gravelle