Effects of Double-Layer Relaxation on the Interaction of Colloidal Particles Approaching at Constant Speed

Mandralis, Zenon I.; Wernet, Judith H.; Feke, Donald L.

doi:10.1006/jcis.1996.0433

Cited by 8 publications

(4 citation statements)

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“…In addition to the possible incomplete surface charging, there may be another aspect of nonequilibrium interaction especially for very small particlesthe electrical double layer relaxation. − It was found, in an experiment using atomic force microscopy (AFM), that there is an increase in repulsive double layer force with increasing approaching velocity (although the effect of hydrodynamic hindrance cannot be ruled out, especially for the flat AFM tip to which the colloidal probe attached); this double layer relaxation effect may contribute to the high stability in very low ionic strength, which cannot be fully accounted for by the equilibrium double layer interaction model employed in classic DLVO theory.…”

Section: Resultsmentioning

confidence: 99%

Paradox of Stability of Nanoparticles at Very Low Ionic Strength

Lin

Wiesner

2012

Langmuir

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The scaling of electrical double layer interaction energy from a plate-plate system to a sphere-plate system was reexamined, and it was found that accurate scaling without resorting to the Derjaguin approximation theoretically predicts the destabilization of nanoparticles in water depleted of added electrolyte and, consequentially, a maximum stability at a moderate ionic strength. This theoretical feature re-emphasizes the dual-role nature of added electrolyte that was supported by experimental results of direct surface force measurement but not by those of colloidal stability of nanoparticle deposition/aggregation. Inconsistences between the theoretical prediction and the experimental observation and between experimental observations in different systems were discussed. Possible reasons leading to the inconsistences were explored, including the effect of curvature, the contribution from counterions, the mode of interaction, and the applicability of an equilibrium model to describe the colloidal interaction of a nanoparticle suspension.

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Section: Resultsmentioning

confidence: 99%

Paradox of Stability of Nanoparticles at Very Low Ionic Strength

Lin

Wiesner

2012

Langmuir

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“…For Si 3 N 4 tips and mica surfaces immersed in Milli-Q water, the capacitance of the electric field interface has become the Stern capacitance 21 of the interface, consequently the dominant relaxation mechanism involves the interchange of ionic species between the Stern and the diffuse part of the double layer. The characteristic time for the interchange of charged species between the Stern and diffuse part of the double layer is given by ϭkTC/ei 0 , where kT/e is equal to 0.025 V, C is the mica/solution interface capacitance, and i 0 is the exchange current density.…”

Section: ͓S0034-6748͑98͒04010-6͔mentioning

confidence: 99%

Atomic force microscopy improved resolution employing large scanning speeds: Effects of the double relaxation time

Teschke

Souza

1998

Review of Scientific Instruments

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The minimum scanning speed of atomic force microscopes for improved atomic resolution has been measured in liquid media, and shown to be equal to 100 nm/s for mica immersed in water corresponding to the time spent scanning the distance between two neighbor ions (∼0.52 nm) of ∼5 ms. The scanning velocity dependence of the force acting on the tip in the double-layer region (∼135 nm) when it approaches the surface was also measured. The stationary component of this force, for scanning speeds up to 30 μm/s, was identified as the exchange of the liquid media with ε≈80 by the tip with ε≈6. As the tip approaches the surface and as well as when the tip images atomic features, this repulsive force shows a relaxation time of a few milliseconds, corresponding to the shielding of the surface charge by the solution, i.e., the double-layer relaxation time. Scanning surfaces at speeds higher than the ratio of the atomic features distance and this relaxation time results in a variable repulsive force acting on the tip, as a function the scanning speed, which might be used to improve the atomic imaging resolution.

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“…In this paper, the forces between plane and curved surfaces are modeled for surfaces that approach and retract with a constant velocity. A dynamic charge regulation model is used based on the assumption that surface reactions are rate limiting. − ,− The charging reactions are based on a standard 2-p K model with all surface charges assumed to reside in a single charging plane. Dynamic population balances are used instead of the equilibrium relations that are generally used but are only valid at thermodynamic equilibrium, e.g., for a slow enough approach/retraction.…”

Section: Introductionmentioning

confidence: 99%

“…Whereas most of the former authors implemented the influence of the force field on the relative velocity of the particles, Mandralis et al describe the electrostatic repulsion between spheres and plates that approach with a constant velocity. The solution phase is assumed to be at equilibrium and the surface charge is assumed to be a function of the overpotential.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Charge Regulation Model for the Electrostatic Forces between Ionizable Materials

Biesheuvel

2002

Langmuir

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The electrostatic repulsion between similar surfaces with ionizable surface groups interacting across aqueous solutions is calculated for plane parallel and curved surfaces for the case in which the solution phase is at thermodynamic equilibrium, but the charged surface is not in equilibrium with the solution. Simulations are made for approaching and retracting oxidic surfaces for which the (equilibrium) surface chemistry is described by a standard 2-pK model. Population balances describe the concentration of each surface species as a function of the rates of the different reactions with the ions in solution. Approaching surfaces experience a higher repulsion than predicted by thermodynamic equilibrium, with the upper limit being the repulsion at a constant surface charge (at very high approach velocities). For retracting surfaces the electrostatic repulsion is lower than that for equilibrium and may decrease to zero when the surfaces are sufficiently discharged at contact and pulled apart fast enough. In that case, and with the attractive van der Waals force still operating, a net attractive force is predicted, which might explain the pull-off force (adhesion force) often measured in the atomic force microscope and the surface force apparatus.

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Effects of Double-Layer Relaxation on the Interaction of Colloidal Particles Approaching at Constant Speed

Cited by 8 publications

References 0 publications

Paradox of Stability of Nanoparticles at Very Low Ionic Strength

Paradox of Stability of Nanoparticles at Very Low Ionic Strength

Atomic force microscopy improved resolution employing large scanning speeds: Effects of the double relaxation time

Dynamic Charge Regulation Model for the Electrostatic Forces between Ionizable Materials

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