Effect of Interfacial Ion Structuring on Range and Magnitude of Electric Double Layer, Hydration, and Adhesive Interactions between Mica Surfaces in 0.05–3 M Li⁺ and Cs⁺ Electrolyte Solutions

Abstract

Ions and water structuring at charged-solid/electrolyte interfaces and forces arising from interfacial structuring in solutions above 100 mM concentrations dominate structure and functionality in many physiological, geological, and technological systems. In these concentrations, electrolyte structuring occurs within the range of molecular dimensions. Here, we quantitatively measure and describe electric double layer (EDL) and adhesive interactions at mica-interfaces in aqueous CsCl and LiCl solutions with concentrations ranging from 50 mM to 3 M. Complementarily, using atomic force microscopy and surface forces apparatus experiments we characterize concentration-dependent stark differences in the inner and outer EDL force profiles, and discuss differences between the used methods. From 50 mM to 1 M concentrations, interactions forces measured in CsCl-solutions exhibit strong hydration repulsions, but no diffuse EDL-repulsions beyond the Stern layer. In confinement the weakly hydrated Cs(+) ions condensate into the mica-lattice screening the entire surface charge within the Stern layer. In contrast, strongly hydrated Li(+) ions only partially compensate the surface charge within the Stern layer, leading to the formation of a diffuse outer double layer with DLVO behavior. Both LiCl and CsCl solutions exhibit oscillatory ion-hydration forces at surface separations from 2.2 nm to 4-8 Å. Below 4-8 Å the force profiles are dominated in both cases by forces originating from water and/or ion confinement at the solid/electrolyte/solid interface. Adhesive minima and their location vary strongly with the electrolyte and its concentration due to specific ion correlations across the interface, while dispersion forces between the surfaces are overpowered. Highly concentrated 3 M solutions exhibit solidification of the inner EDL structure and an unexpected formation of additional diffuse EDL forces with an increasing range, as recently measured in ionic liquids. Our results may have important implications for understanding and modeling of interaction forces present in static and dynamic systems under physiological and high salt conditions.

Pore-Scale Controls on Reaction-Driven Fracturing

“…These systems are more complex, but their behavior is still consistent with the molecular picture that has been obtained for the lower solution concentrations (Baimpos et al 2014). Interestingly, at these concentrations adhesive interaction forces are found to be largely due to solute and solvent correlation forces (Lesko et al 2001;Espinosa-Marzal et al 2012;Baimpos et al 2014). Ion correlation forces have been suggested to play a key role in controlling the cohesion of cement (Lesko et al 2001), and we may speculate that they are a critical factor in determining the cohesive properties of natural rocks as well.…”

“…These systems are more complex, but their behavior is still consistent with the molecular picture that has been obtained for the lower solution concentrations (Baimpos et al 2014). Interestingly, at these concentrations adhesive interaction forces are found to be largely due to solute and solvent correlation forces (Lesko et al 2001;Espinosa-Marzal et al 2012;Baimpos et al 2014).…”

“…However, if the stress is suffi cient to open a fracture, the stress on the crystal surface will decrease, thus enabling further growth. When strain rates are slow, as can be the case during precipitation in pores and cracks, fracture propagation takes place through a kinetic process known as subcritical crack growth (Atkinson 1987). Røyne et al (2011b) showed how to couple the rates of crystal growth and fracture propagation when a crystal grows from a supersaturated solution inside the aperture of a fracture (see Fig.…”

Long-range electrostatic screening in ionic liquids

“…We instead propose that local excess charge densities fundamentally determine the length scales of electrostatic screening and show that a "dissociation reaction" between effectively neutral ionic networks and either free ions or higher-order correlated charge domains can provide a useful framework for understanding such systems. For example, recent SFA measurements across concentrated aqueous electrolyte solutions (38,39) establish that the range of electric double-layer interactions increases as the aqueous electrolyte concentrations are increased from 1 to 3 M, but only as long as the electrolyte cation differs from the K + ion that is native to mica surfaces. Our results suggest that this trend may be due to the progressive formation of effectively neutral ionic networks involving large numbers of strongly interacting ions.…”

Long-ranged and soft interactions between charged colloidal particles induced by multivalent coions

“…[1][2][3][4][5][6][7][8] Such forces are becoming routinely accessible with various methods, including, the surface forces apparatus, the colloidal probe technique, or total internal reflection microscopy. [1][2][3][4][5][6][7][8] Such forces are becoming routinely accessible with various methods, including, the surface forces apparatus, the colloidal probe technique, or total internal reflection microscopy.…”