Aggregation in polystyrene-sphere suspensions in near-critical binary liquid mixtures

Gallagher, Patrick; Kurnaz, M. Levent; Maher, J. V.

doi:10.1103/physreva.46.7750

Cited by 66 publications

(66 citation statements)

References 20 publications

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“…Such a solvent-mediated flocculation, which can be interpreted as indirect evidence for the critical Casimir force, has indeed been observed for silica spheres suspended in a binary liquid mixture of water and lutidine [30,31,32,33] (see also Ref. [34] and references therein) as well as in other binary mixtures [35,36,37,38].…”

Section: Introductionmentioning

confidence: 93%

Critical Casimir interaction of ellipsoidal colloids with a planar wall

Kondrat

Harnau

Dietrich

2009

The Journal of Chemical Physics

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Based on renormalization group concepts and explicit mean field calculations we study the universal contribution to the effective force and torque acting on an ellipsoidal colloidal particle which is dissolved in a critical fluid and is close to a homogeneous planar substrate. At the same closest distance between the substrate and the surface of the particle, the ellipsoidal particle prefers an orientation parallel to the substrate and the magnitude of the fluctuation induced force is larger than if the orientation of the particle is perpendicular to the substrate. The sign of the critical torque acting on the ellipsoidal particle depends on the type of boundary conditions for the order parameter at the particle and substrate surfaces, and on the pivot with respect to which the particle rotates.

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Section: Introductionmentioning

confidence: 93%

Critical Casimir interaction of ellipsoidal colloids with a planar wall

Kondrat

Harnau

Dietrich

2009

The Journal of Chemical Physics

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“…First, we discuss the results for a standard set of parameters (σ std = 0.1, I std = 0.85, ε std = 62/72, b 1 ≈ 0.23, βeΦ D = 1) which corresponds to a typical experimental setup, e.g., a water-lutidine (2,6-dimethylpyridine) mixture with NaI salt (1 mM in the aqueous phase) at temperature T = 313 K in contact with polystyrene walls exhibiting, in the aqueous phase, a surface charge density of 0.1 e/nm 2 [13,25,[27][28][29][30][31]. The resulting interaction energies are presented in Fig.…”

Section: A L-dependent Interactionsmentioning

confidence: 99%

Poisson-Boltzmann study of the effective electrostatic interaction between colloids at an electrolyte interface

Majee¹,

Bier²,

Dietrich

2016

The Journal of Chemical Physics

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The effective electrostatic interaction between a pair of colloids, both of them located close to each other at an electrolyte interface, is studied by employing the full, nonlinear Poisson-Boltzmann (PB) theory within classical density functional theory. Using a simplified yet appropriate model, all contributions to the effective interaction are obtained exactly, albeit numerically. The comparison between our results and those obtained within linearized PB theory reveals that the latter overestimates these contributions significantly at short inter-particle separations. Whereas the surface contributions to the linear and the nonlinear PB results differ only quantitatively, the line contributions show qualitative differences at short separations. Moreover, a dependence of the line contribution on the solvation properties of the two adjacent fluids is found, which is absent within the linear theory. Our results are expected to enrich the understanding of effective interfacial interactions between colloids.

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“…At higher particle concentrations, additional critical Casimir forces between nearby particle surfaces arise and eventually lead to the formation of three-dimensional, facetted colloidal islands on the substrate. Because the particle-substrate and the particle-particle critical Casimir interactions can be systematically and independently varied, this also leads to new opportunities in the use of colloidal model systems to study the growth of islands on surfaces as this is important for the fabrication of nanostructures [15].We used 2.4 µm diameter polystyrene (PS) spheres with a surface charge of 10 µC/cm 2 rendering them hydrophilic which corresponds to (−) boundary conditions [16]. They were suspended in a water-2,6-lutidine (WL) mixture with critical composition, i.e.…”

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confidence: 99%

Critical Casimir Forces in Colloidal Suspensions on Chemically Patterned Surfaces

et al. 2008

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We investigate the behavior of colloidal particles immersed in a binary liquid mixture of water and 2,6-lutidine in the presence of a chemically patterned substrate. Close to the critical point of the mixture, the particles are subjected to critical Casimir interactions with force components normal and parallel to the surface. Because the strength and sign of these interactions can be tuned by variations in the surface properties and the mixtures temperature, critical Casimir forces allow the formation of highly ordered monolayers but also extend the use of colloids as model systems.PACS numbers: 82.70. Dd, 68.35.Rh, 81.16.Dn Analogous to the geometrical confinement of quantumelectrodynamical (QED) vacuum fluctuations between two parallel metallic plates [1], the constraint of concentration fluctuations in fluid mixtures close to their critical point gives rise to critical Casimir forces acting on the confining surfaces [2]. The range of this interaction is set by the bulk correlation length ξ of the mixture which diverges when approaching the critical point. Therefore, critical Casimir forces are sensitive to minute changes in temperature. Despite several quantitative measurements of such forces [3,4], it was only recently when the amplitude of measured critical Casimir forces in quantumand classical liquids has been directly compared to theoretical predictions [5,6,7,8]. Direct force measurements of a single colloidal particle above a flat surface and immersed in a critical water-lutidine mixture demonstrated, that critical Casimir interactions can easily exceed multiples of the thermal energy k B T [8]. Accordingly, they offer a versatile opportunity to control the pair interaction in colloidal suspensions by weak temperature changes [9,10]. Apart from their exquisite temperature dependence, critical Casimir forces respond sensitively to the chemical properties of the confining surfaces. Depending on whether both surfaces preferentially attract the same mixture's component or not (symmetric or asymmetric boundary conditions), attractive or repulsive critical Casimir forces arise [8,11,12].So far, experimental investigations of critical Casimir interactions were limited to homogeneous surfaces (in contrast to QED Casimir forces [13]) where the corresponding forces act perpendicular to the confining walls. However, when one or both surfaces are chemically patterned, also lateral critical Casimir forces have been predicted [14] In this Letter we experimentally study the interaction between colloidal particles and chemically patterned substrates immersed in a binary critical mixture. Close to the critical point lateral critical Casimir forces lead to the formation of highly ordered colloidal assemblies whose structure is controlled by the underlying chemical pattern. This may suggest a novel route for templated growth of colloidal crystals. At higher particle concentrations, additional critical Casimir forces between nearby particle surfaces arise and eventually lead to the formation of three-dimensional, face...

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Aggregation in polystyrene-sphere suspensions in near-critical binary liquid mixtures

Cited by 66 publications

References 20 publications

Critical Casimir interaction of ellipsoidal colloids with a planar wall

Critical Casimir interaction of ellipsoidal colloids with a planar wall

Poisson-Boltzmann study of the effective electrostatic interaction between colloids at an electrolyte interface

Critical Casimir Forces in Colloidal Suspensions on Chemically Patterned Surfaces

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