Making Sense of Electrical Noise by Simulating Electrolyte Solutions

ongoing

Seemingly unrelated experiments such as electrolyte transport through nanotubes, nano-scale electrochemistry, NMR relaxometry and Surface Force Balance measurements, all probe electrical fluctuations: of the electric current, the charge and polarization, the field gradient (for quadrupolar nuclei) and the coupled mass/charge densities. If only we had the theoretical tools to interpret this “electrical noise”, we would open complementary windows on ionic systems. Such insight is needed, as recent experiments uncovered unexpected behaviour of ionic systems (electrolytes, ionic liquids), which question our understanding of these “simple” fluids and call for a fresh theoretical perspective. This project aims at providing an integrated understanding of fluctuations in bulk, interfacial and confined ionic systems. For modelling, the key challenge is to quantitatively predict the phenomena underlying the various sources of noise: coupled diffusion, long-range electrostatic interactions & hydrodynamic flows, short-range ion-specific effects (solvation, ad/desorption). Using molecular and mesoscopic simulations, I will provide a unified theoretical framework enabling experimentalists to decipher the microscopic properties encoded in the measured electrical noise. I will achieve this by addressing four interlinked questions corresponding to the above-mentioned experiments: 1) What is the microscopic origin of the “coloured” noise of electric current through single nanopores/tubes? 2) What do the charge fluctuations of an electrode tell us about the properties of the interfacial electrolyte? 3) What information can NMR relaxometry provide on the multiscale dynamics of individual ions? 4) Could collective fluctuations in concentrated electrolytes explain long-range forces between surfaces? Each question is in itself an exciting challenge, but addressing them simultaneously is the key to a global understanding of these liquids which play a crucial role in biology and technology.