Monolayers of charged particles in a Langmuir trough: Could particle aggregation increase the surface pressure?

Petkov, Plamen; Danov, Krassimir D.; Kralchevsky, Peter A.

doi:10.1016/j.jcis.2015.09.075

Cited by 38 publications

(58 citation statements)

References 72 publications

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“…in which is the particle surface charge density, equal to 0.12 µC/cm 2 for silica 46 , a value comparable to that determined on the basis of the experimentally measured zeta potential via…”

Section: Particle-particle Interactions At the Air/aqueous Interfacesupporting

confidence: 83%

Interfacial Particle Dynamics: One and Two Step Yielding in Colloidal Glass

Zhang

Cayre

et al. 2016

Langmuir

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The yielding behaviour of silica nanoparticles partitioned at an air-aqueous interface is reported. Linear viscoelasticity of the particle-laden interface can be retrieved via a timedependent and electrolyte-dependent superposition, and the applicability of the 'soft glassy rheology' (SGR) model is confirmed. With increasing electrolyte concentration a non-ergodic state is achieved with particle dynamics arrested firstly from attraction induced bonding bridges and then from the cage effect of particle jamming, manifesting in a two-step yielding process under large amplitude oscillation strain (LAOS). The Lissajous curves disclose a shear-induced in-cage particle re-displacement within oscillation cycles between the two yielding steps, exhibiting a 'strain softening' transitioning to 'strain stiffening' as the interparticle attraction increases. By varying and the particle spreading concentration, , a variety of phase transitions from fluid-to gel-and glass-like can be unified to construct a state diagram mapping the yielding behaviors from one-step to two-step before finally exhibiting one-step yielding at high and .

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Section: Particle-particle Interactions At the Air/aqueous Interfacesupporting

confidence: 83%

Interfacial Particle Dynamics: One and Two Step Yielding in Colloidal Glass

Zhang

Cayre

et al. 2016

Langmuir

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“…In the large inter-particle separation limit, it was found that the surface pressure scales as Π ∼ a −3/2 . This scaling was shown to be in good agreement with experimental data [17,18,25] measured either in the absence of salt or for weak electrolytes (using two fit parameters). It contradicts, however, the scaling law found earlier in ref [16].…”

Section: Introductionsupporting

confidence: 83%

“…Such approximation recovers the main physical features. The redistribution of charge merely introduces geometric corrections (as was similarly approached in refs [17][18][19]32]).…”

Section: Modeling Of the Colloidal Monolayermentioning

confidence: 97%

Surface Pressure of Charged Colloids at the Air/Water Interface

2018

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Charged colloidal monolayers at the interface between water and air (or oil) are used in a large number of chemical, physical and biological applications. Although a considerable experimental and theoretical effort has been devoted in the past few decades to investigate such monolayers, some of their fundamental properties are not yet fully understood. In this paper, we model charged colloidal monolayers as a continuum layer of finite thickness, with separate charge distribution on the water and air sides. The electrostatic surface free-energy and surface pressure are calculated via the charging method and within the Debye-Hückel approximation. We obtain the dependence of surface pressure on several system parameters: the monolayer thickness, its distinct dielectric permittivity, and the ionic strength of the aqueous subphase. The surface pressure scaling with the area per particle, a, is found to be between a −2 in the close-packing limit, and a −5/2 in the loose-packing limit. In general, it is found that the surface-pressure is strongly influenced by charges on the air-side of the colloids. However, when the larger charge resides on the water-side, a more subtle dependence on salt concentration emerges. This corrects a common assumption that the charges on the water-side can always be neglected due to screening. Finally, using a single fit parameter, our theory is found to fit well the experimental data for strong to intermediate strength electrolytes. We postulate that an anomalous scaling of a −3/2 , recently observed in low ionic concentrations, cannot be accounted for within a linear theory, and its explanation requires a fully-nonlinear analysis.

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“…The experimental plot of A versus α is a linear dependence, which means that there is no loss of particles during the compression due, for example, to particle detachment from the interface and sinking in the subphase. From the slope of this dependence, we can determine N (see [23,24] for details).…”

Section: Experimental System and Results (A) Materials And Methodsmentioning

confidence: 99%

“…One of our goals in this article is the explanation of the dependence of surface pressure Π on the interparticle distance L. The paper represents a brief review of our recent results [23,24], as well as related results from other studies, and considers also the effects of particle aggregation and added electrolyte on the surface pressure of monolayers from charged particles. The experimental system and results are described in §2.…”

Section: Introductionmentioning

confidence: 99%

Soft electrostatic repulsion in particle monolayers at liquid interfaces: surface pressure and effect of aggregation

Kralchevsky¹,

Danov²,

Petkov³

2016

Phil. Trans. R. Soc. A.

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Non-densely packed interfacial monolayers from charged micrometre-sized colloid particles find applications for producing micropatterned surfaces. The soft electrostatic repulsion between the particles in a monolayer on an air/water (or oil/water) interface is mediated by the non-polar fluid, where Debye screening is absent and the distances between the particles are considerably greater than their diameters. Surface pressure versus area isotherms were measured at the air/water interface. The experiments show that asymptotically the surface pressure is inversely proportional to the third power of the interparticle distance. A theoretical model is developed that predicts not only the aforementioned asymptotic law but also the whole surface pressure versus area dependence. An increase in the surface pressure upon aggregation of charged particles in the interfacial monolayers is experimentally established. This effect is explained by the developed theoretical model, which predicts that the surface pressure should linearly increase with the square root of the particle mean aggregation number. The effect of added electrolyte on the aggregation is also investigated. The data lead to the conclusion that 'limited aggregation' exists in the monolayers of charged particles. In brief, the stronger electrostatic repulsion between the bigger aggregates leads to a higher barrier to their coalescence that, in turn, prevents any further aggregation, i.e. negative feedback is present.This article is part of the themed issue 'Soft interfacial materials: from fundamentals to formulation'.

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Monolayers of charged particles in a Langmuir trough: Could particle aggregation increase the surface pressure?

Cited by 38 publications

References 72 publications

Interfacial Particle Dynamics: One and Two Step Yielding in Colloidal Glass

Interfacial Particle Dynamics: One and Two Step Yielding in Colloidal Glass

Surface Pressure of Charged Colloids at the Air/Water Interface

Soft electrostatic repulsion in particle monolayers at liquid interfaces: surface pressure and effect of aggregation

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