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Real-time tracking of ionic nano-domains under shear flow

Cafolla, C.; Voïtchovsky, K.

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Dr Miro Cafolla
Addison Wheeler Research Fellow


The behaviour of ions at solid–liquid interfaces underpins countless phenomena, from the conduction of nervous impulses to charge transfer in solar cells. In most cases, ions do not operate as isolated entities, but in conjunction with neighbouring ions and the surrounding solution. In aqueous solutions, recent studies suggest the existence of group dynamics through water-mediated clusters but results allowing direct tracking of ionic domains with atomic precision are scarce. Here, we use high-speed atomic force microscopy to track the evolution of Rb+, K+, Na+ and Ca2+ nano-domains containing 20 to 120 ions adsorbed at the surface of mica in aqueous solution. The interface is exposed to a shear flow able to influence the lateral motion of single ions and clusters. The results show that, when in groups, metal ions tend to move with a relatively slow dynamics, as can be expected from a correlated group motion, with an average residence timescale of ~ 1–2 s for individual ions at a given atomic site. The average group velocity of the clusters depends on the ions’ charge density and can be explained by the ion’s hydration state. The lateral shear flow of the fluid is insufficient to desorb ions, but indirectly influences the diffusion dynamics by acting on ions in close vicinity to the surface. The results provide insights into the dynamics of ion clusters when adsorbed onto an immersed solid under shear flow.


Cafolla, C., & Voïtchovsky, K. (2021). Real-time tracking of ionic nano-domains under shear flow. Scientific Reports, 11, Article 19540.

Journal Article Type Article
Acceptance Date Sep 2, 2021
Online Publication Date Oct 1, 2021
Publication Date 2021-12
Deposit Date Sep 2, 2021
Publicly Available Date Oct 7, 2021
Journal Scientific Reports
Publisher Nature Research
Peer Reviewed Peer Reviewed
Volume 11
Article Number 19540


Published Journal Article (1.7 Mb)

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