Temperature-sensitive colloidal phase behavior induced by critical Casimir forces

Dang, Minh Triet; Verde, Ana Vila; Nguyen, Van Duc; Bolhuis, Peter G.; Schall, Peter

doi:10.1063/1.4819896

Cited by 46 publications

(91 citation statements)

References 44 publications

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“…Temperature can be changed in a reversible manner, and reversible structural changes can be induced [20,21,25]. In particular, when the effective potential has a minimum, then analogs of the gas-liquid and liquid-solid transitions between the particles were observed [20].…”

Section: Introductionmentioning

confidence: 99%

The effect of antagonistic salt on a confined near-critical mixture

Pousaneh

Ciach

2014

Soft Matter

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We consider a near-critical binary mixture with addition of antagonistic salt confined between weakly charged and selective surfaces. A mesoscopic functional for this system is developed from a microscopic description by a systematic coarse-graining procedure. The functional reduces to the Landau-Brazovskii functional for amphiphilic systems for sufficiently large ratio between the correlation length in the critical binary mixture and the screening length. Our theoretical result agrees with the experimental observation [Sadakane et.al. J. Chem. Phys. 139, 234905 (2013)] that the antagonistic salt and surfactant both lead to a similar mesoscopic structure. For very small salt concentration ρ ion the Casimir potential is the same as in a presence of inorganic salt.For larger ρ ion the Casimir potential takes a minimum followed by a maximum for separations of order of tens of nanometers, and exhibits an oscillatory decay very close to the critical point. For separations of tens of nanometers the potential between surfaces with a linear size of hundreds of nanometers can be of order of k B T . We have verified that in the experimentally studied samples [Sadakane et.al. J. Chem. Phys. 139, 234905 (2013), Leys et.al. Soft Matter 9, 9326 (2013] the decay length is too small compared to the period of oscillations of the Casimir potential, but the oscillatory force could be observed closer to the critical point.

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Section: Introductionmentioning

confidence: 99%

The effect of antagonistic salt on a confined near-critical mixture

Pousaneh

Ciach

2014

Soft Matter

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“…13 Theoretical and simulation studies on the phase behavior and structure of the full ternary mixture of colloidal particles moving around in an explicit solvent mixture are hampered by the huge differences in length and time scales between the colloids, solvent species, and the diverging bulk correlation length of the solvent mixture. As such, in most theoretical and simulation approaches, such as the works of Mohry et al, [14][15][16] Nguyen et al, 13,17 and Dang et al, 18 the binary solvent mixture is taken to be a structureless implicit background. This approach fails to capture important elements such as the fractionation of the solvent in the coexisting colloidal phases.…”

Section: Introductionmentioning

confidence: 99%

From 2D to 3D: Critical Casimir interactions and phase behavior of colloidal hard spheres in a near-critical solvent

Tasios

Dijkstra

2017

The Journal of Chemical Physics

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Colloids dispersed in a binary solvent mixture experience long-ranged solvent-mediated interactions (critical Casimir forces) upon approaching the critical demixing point of the solvent mixture. The range of the interaction is set by the bulk correlation length of the solvent mixture, which diverges upon approaching the critical point. This presents a great opportunity to realize the reversible selfassembly of colloids by tuning the proximity to the critical point of the solvent. Here, we develop a rejection-free geometric cluster algorithm to study the full ternary mixture of colloidal hard spheres suspended in an explicit three-dimensional lattice model for the solvent mixture using extensive Monte Carlo simulations. The phase diagram displays stable colloidal gas, liquid, and crystal phases, as well as broad gas-liquid and gas-crystal phase coexistence, and pronounced fractionation of the solvent in the coexisting colloid phases. The topology of the phase diagram in our three-dimensional study shows striking resemblance to that of our previous studies carried out in two dimensions. Published by AIP Publishing. [http://dx

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“…As far as the theoretical side is concerned, it was de Gennes who first obtained the CCF between spherical particles [53] considering a local freeenergy functional. Among the other techniques used to study the CCF in sphere-plate and sphere-sphere geometries are the Ornstein-Zernike theory [54], conformal invariance methods [55][56][57], Monte Carlo calculations [58][59][60][61][62][63][64][65][66][67], fluid-particle dynamics simulations [68,69], mean-field type [70][71][72][73][74] and density-functional [75] theory calculations combined with the Derjaguin approximation [44,[76][77][78]. Several review articles and works [8,[79][80][81][82] summarize both the experimental and theoretical results presented there.…”

Section: Introductionmentioning

confidence: 99%

Sign change in the net force in sphere-plate and sphere-sphere systems immersed in nonpolar critical fluid due to the interplay between the critical Casimir and dispersion van der Waals forces

Valchev

Dantchev

2017

Phys. Rev. E

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We study systems in which both long-ranged van der Waals and critical Casimir interactions are present. The last arise as an effective force between bodies when immersed in a near-critical medium, say a nonpolar onecomponent fluid or a binary liquid mixture. They are due to the fact that the presence of the bodies modifies the order parameter profile of the medium between them as well as the spectrum of its allowed fluctuations. We study the interplay between these forces, as well as the total force (TF) between a spherical colloid particle and a thick planar slab, and between two spherical colloid particles. We do that using general scaling arguments and mean-field type calculations utilizing the Derjaguin and the surface integration approaches. They both are based on data of the forces between two parallel slabs separated at a distance L from each other, confining the fluctuating fluid medium characterized by its temperature T and chemical potential µ. The surfaces of the colloid particles and the slab are coated by thin layers exerting strong preference to the liquid phase of the fluid, or one of the components of the mixture, modeled by strong adsorbing local surface potentials, ensuring the socalled (+, +) boundary conditions. On the other hand, the core region of the slab and the particles, influence the fluid by long-ranged competing dispersion potentials. We demonstrate that for a suitable set of colloids-fluid, slab-fluid, and fluid-fluid coupling parameters the competition between the effects due to the coatings and the core regions of the objects involved result, when one changes T , µ or L, in sign change of the Casimir force (CF) and the TF acting between the colloid and the slab, as well as between the colloids. This can be used for governing the behavior of objects, say colloidal particles, at small distances, say in colloid suspensions for preventing flocculation. It can also provide a strategy for solving problems with handling, feeding, trapping and fixing of microparts in nanotechnology. Data for specific substances in support of the experimental feasibility of the theoretically predicted behavior of the CF and TF have been also presented.

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Temperature-sensitive colloidal phase behavior induced by critical Casimir forces

Cited by 46 publications

References 44 publications

The effect of antagonistic salt on a confined near-critical mixture

The effect of antagonistic salt on a confined near-critical mixture

From 2D to 3D: Critical Casimir interactions and phase behavior of colloidal hard spheres in a near-critical solvent

Sign change in the net force in sphere-plate and sphere-sphere systems immersed in nonpolar critical fluid due to the interplay between the critical Casimir and dispersion van der Waals forces

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