Stepwise collapse of highly overlapping electrical double layers

Zachariah, Zita; Espinosa‐Marzal, Rosa M.; Spencer, Nicholas D.; Heuberger, Manfred

doi:10.1039/c6cp04222h

Cited by 28 publications

(45 citation statements)

References 47 publications

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“…The experimental procedures used in this work were chosen similar to those described in earlier references [23,24]: Muscovite mica is the substrate of choice to measure surfaces forces [25] at nanometer separations; it has an atomically flat surface, it is optically transparent and can easily be cleaved along the (001) plane [26] into macroscopic sheets. The negative lattice charge of the mica surface in aqueous solution originates from the isomorphic substitution of Si 4+ by Al 3+ in the crystal lattice and the hydration-dissociation of the interlayer K + ions [27].…”

Section: Experimental Methodsmentioning

confidence: 99%

“…The increasing counterion population at the interface eventually also gives rise to a sudden fundamental change in the way the molecular structure evolves, since above a threshold activity, oscillatory forces appeared in the forcecurve, and, almost simultaneously the pull-off force deviated sharply from this general gradual slope. The occurrence of an abrupt change of pull-off force was originally discovered with solutions of KNO3 and termed the π-transition [24]. It was previously concluded that since the pull-off force is dependent on the molecular arrangement at the loaded interface and the πtransition coincided with the occurrence of hydrated ions layering, the π-transition was caused by a change in the arrangement of the hydrated couterions at the surface.…”

Section: /13mentioning

confidence: 99%

“…Previous work in aqueous KNO3 solutions established three phenomenological regimes: the "DLVO" regime at low concentrations, the "ordering" regime at intermediate concentrations and the "solidification" regime at high concentrations [23,24]. The crossover from the DLVO regime to the ordering regime, where hydrated-ion layering is noticed as film-thickness transitions (FTTs), is marked by the phenomenon of a stepwise decrease in pull-off force, π, over a narrow range of salt concentration; this was called the π-transition.…”

Section: The Blue Spheres Represent the Hydration Water Associated Tomentioning

confidence: 99%

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Ion specific hydration in nano-confined electrical double layers

Zachariah

Espinosa‐Marzal

Heuberger

2017

Journal of Colloid and Interface Science

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We probe counter-ion specific effects in nano-confined electrical-double-layers (EDLs) by means of direct force measurements across a model slit pore in the extended surface forces apparatus. By variation of solution composition, we compare four different counter-ions with dissimilar hydration properties, namely Na, K, Cs as well as HO, all confined between (001) mica surfaces. We discuss the results in terms of a recently proposed π-transition model, evoking hydrated ion layering as the recurrent structural element in highly confined EDLs. We demonstrate that the π-transition essentially proceeds in multiple steps in coherence with the event of single- or multiple- hydrated-ion layering.

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Section: Experimental Methodsmentioning

confidence: 99%

Section: /13mentioning

confidence: 99%

Section: The Blue Spheres Represent the Hydration Water Associated Tomentioning

confidence: 99%

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Ion specific hydration in nano-confined electrical double layers

Zachariah

Espinosa‐Marzal

Heuberger

2017

Journal of Colloid and Interface Science

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“…h j + w P n 8 A X y g j c 0 = < / l a t e x i t > < l a t e x i t s h a 1 _ b a s e 6 4 = " t c t z s J P H magnitude of the EDL repulsive barrier for calcite surfaces in low ionic strength solution is very small, and unlikely to explain the purely repulsive behavior observed under these conditions; and 2) pull-off forces seem to increase in magnitude even as the ionic strength is increased beyond what should be the limit of the DLVO theory [29,31,48,[73][74][75]. An increase in the measured pull-off force can be explained by a decrease in any repulsive barrier present (due to EDL or hydrophilic repulsion), to an increase in the adhesive interaction (van der Waals or ion correlation forces), or both.…”

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confidence: 99%

Adhesive forces between two cleaved calcite surfaces in NaCl solutions: The importance of ionic strength and normal loading

Javadi

Røyne

2018

Journal of Colloid and Interface Science

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The mechanical strength of calcite bearing rocks is influenced by pore fluid chemistry due to the variation in nano-scale surface forces acting at the grain contacts or close to the fracture tips. The adhesion of two contacting surfaces, which affects the macroscopic strength of the material, is not only influenced by the fluid chemistry but also by the surface topography. In this paper, we use Atomic Force Microscope (AFM) to measure the interfacial forces between two freshly cleaved calcite surfaces in CaCO-saturated solutions with varying NaCl concentration. We show that calcite contacts become stronger with increasing NaCl concentration (>100 mM), as a result of progressively weaker secondary hydration and increasing attraction due to instantaneous ion-ion correlation. Moreover, we discuss the effect of normal applied force (F) and surface roughness on the measured adhesion forces (F). We show that the measured pull-off force (adhesion) is linearly correlated with the magnitude of F, where an increase in applied force results in increased adhesion. This is attributed to a larger number of contacting surface asperities and thus increase in real contact area and the contact-bond strength. We discuss that the possible variation in local topography at contacts, together with strong dependence on ionic strength of the solution, can explain the inconsistent behavior of calcite rocks in NaCl solutions.

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“…Discrepancies from the DLVO theory have been reported at concentrations as low as 0.3 mM (10): Direct surface force measurements have revealed repulsive hydration forces with decay lengths ranging from 0.1 to 1 nm (10, 11) with an oscillatory component, first considered to result from the oscillatory density profile (i.e., layering) of confined water layers (12). Besides water layering, the surface adsorption of hydrated ions (13,14) and, more recently, their confinement-induced layering (15,16), have been also considered to be responsible for the repulsive hydration forces. The experimental results by Pashley first demonstrated the ion specificity of the hydration force (10).…”

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confidence: 99%

Molecular insight into the nanoconfined calcite–solution interface

Diao

Espinosa‐Marzal

2016

Proc. Natl. Acad. Sci. U.S.A.

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Little is known about the influence of nanoconfinement on calcium carbonate mineralization. Here, colloidal probe atomic force microscopy is used to confine the calcite-solution interface with a silica microsphere and to measure Derjaguin-Landau-Verwey-Overbeek (DLVO) and non-DLVO forces as a function of the calcium concentration, also after charge reversal of both surfaces occurs. Through the statistical analysis of the oscillatory component of a strong hydration force, the subnanometer interfacial structure of the confined atomically flat calcite is resolved in aqueous solution. By applying a mechanical work, both water and hydrated counterions are squeezed out from the nanoconfined solution, leaving the calcite surface more negatively charged than the analogous unconfined surfaces. Layer size and applied work allow a distinction between the hydration states of the counterions in the Stern layer; we propose counterions to be inner-and outer-sphere calcium ions, with a population of inner-sphere calcium ions larger than on unconfined calcite surfaces. It is also shown that the composition of the nanoconfined solution can be tuned by varying calcium concentration. This is a fundamental study of DLVO and hydration forces, and of their connection, on atomically flat calcite. More broadly, our work scrutinizes the greatly unexplored relation between surface science and confined mineralization, with implications for diverse areas of inquiry, such as nanoconfined biomineralization, CO 2 sequestration in porous aquifers, and pressure solution and crystallization in confined hydrosystems.calcite | hydration forces | DLVO theory | nanoconfinement | atomic force microscopy U nderstanding the effect of nanoconfinement on the solution composition near the calcite surface is crucial in revealing the mechanisms of biomineralization in confinement, because the confined thin film of aqueous electrolyte, which provides the path for ions and water to the buried mineral interface, can behave totally different from the unconfined (free) solution.Whereas the effect of confinement on the properties of the calcite-solution interface is largely unexplored, the Stern layer of unconfined calcite surfaces has been intensively investigated via simulations and experiments. Interestingly, Ca 2+ and CO 3 2− (and HCO 3 − ) ions are not adsorbed directly to calcite but to surfaceadsorbed water molecules as outer-sphere species (OS) due to calcite's strong affinity to water (1). X-ray reflectivity studies (2, 3) and molecular dynamics (MD) simulations (4) have proved that the calcite-solution interface is well defined by two layers of water molecules. Hence, instead of the conventional model, where the Stern layer is adjacent to the charged surface, calcite's Stern layer, the compact layer of counterions, is believed to be located on top of two water layers: OS calcium (OS-Ca 2+ ) ions mainly populate the interface at ∼4.9 Å from the unconfined calcite surface, whereas the population of inner-sphere calcium (IS-Ca 2+ ) ions is located at ∼3.3 Å...

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Stepwise collapse of highly overlapping electrical double layers

Cited by 28 publications

References 47 publications

Ion specific hydration in nano-confined electrical double layers

Ion specific hydration in nano-confined electrical double layers

Adhesive forces between two cleaved calcite surfaces in NaCl solutions: The importance of ionic strength and normal loading

Molecular insight into the nanoconfined calcite–solution interface

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