Non-equilibrium concentration fluctuations in superparamagnetic nanocolloids

Oprisan, Ana; Rice, Ashley; Oprisan, Sorinel A.; Giraudet, Cédric; Croccolo, Fabrizio

doi:10.1140/epje/i2017-11503-y

Cited by 5 publications

(3 citation statements)

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“…In the limiting case of infinite dilution of the particles, both types of diffusivities match and correspond with the tracer diffusion coefficient of the particles . While particle tracking methods only provide diffusivity data within this limitation, dynamic light scattering , (DLS) and other photon correlation spectroscopy methods − give access to the translational or Fick diffusion coefficients . The latter ones are the diffusivities required for the description of mass transport in particulate systems.…”

Section: Introductionmentioning

confidence: 99%

Translational and Rotational Diffusion Coefficients of Gold Nanorods Dispersed in Mixtures of Water and Glycerol by Polarized Dynamic Light Scattering

et al. 2019

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Polarized dynamic light scattering (DLS) gives access to orientation-averaged translational and rotational diffusion coefficients of anisotropic particles dispersed in fluids in a single experiment. As the combination of both diffusivities contains information on the morphology of the particles, their simultaneous and accurate measurement for the same sample and thermodynamic state is beneficial for particle characterization. For nontransparent model suspensions of gold nanorods in water and water–glycerol mixtures, a scattering geometry in reflection direction was realized, which minimizes multiple scattering and allows using low laser powers to avoid laser heating. Furthermore, a heterodyne detection scheme was guaranteed by superimposing much stronger reference light to the scattered light. This ensures an unambiguous data evaluation and reduces the uncertainties for the rotational and the translational diffusivity, where the latter is accessible with smaller uncertainty. For the water-based suspensions, both diffusivities agree well with the stick hydrodynamic theory for rods and show an Andrade-type behavior in the studied temperature range from 271 to 323 K. The measured results for both diffusivities, particularly for the rotational diffusivity, indicate a breakdown of the stick boundary conditions for dynamic viscosities larger than 4 mPa·s.

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Section: Introductionmentioning

confidence: 99%

Translational and Rotational Diffusion Coefficients of Gold Nanorods Dispersed in Mixtures of Water and Glycerol by Polarized Dynamic Light Scattering

et al. 2019

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“…On a more general perspective, we remark that NE effects are continuously invoked in a variety of situations of experimental interest involving complex hydrodynamics. These include studies with colloidal suspensions [79][80][81][82], transient and enhanced diffusion effects [83][84][85][86], driven active matter [87], complex polymeric fluids [88], finite Reynolds numbers fluids [89]. In particular, for the future, it could be insightful to design experiments involving colloidal particles exhibiting a mechanical-chemical coupling with the fluid [90], in such a way that NE fluctuations effects can be indirectly reconstructed and studied from the particles trajectories.…”

Section: Discussionmentioning

confidence: 99%

Lattice Boltzmann simulations of nonequilibrium fluctuations in a nonideal binary mixture

et al. 2019

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In the recent years the lattice Boltzmann (LB) methodology has been fruitfully extended to include the effects of thermal fluctuations. So far, all studied cases pertain equilibrium fluctuations, i.e. fluctuations with respect to an equilibrium background state. In this paper we take a step further and present results of fluctuating LB simulations of a binary mixture confined between two parallel walls in presence of a constant concentration gradient in the wall-to-wall direction. This is a paradigmatic set-up for the study of non-equilibrium (NE) fluctuations, i.e. fluctuations with respect to a nonequilibrium state. We analyze the dependence of the structure factors for the hydrodynamical fields on the wave vector q in both the directions parallel and perpendicular to the walls, as well as the finite-size effects induced by confinement, highlighting the long-range (∼ |q| −4 ) nature of correlations in the NE framework. Results quantitatively agree with the predictions of fluctuating hydrodynamics. Moreover, in presence of a non-ideal (NI) equation of state of the mixture, we also observe that the (spatially homogeneous) average pressure changes, due to a genuinely new contribution triggered by the long-range nature of NE fluctuations. These NE pressure effects are studied at changing the system size and the concentration gradient. Taken all together, we argue that these findings are instrumental to boost the applicability of the fluctuating LB methodology in the framework of NE fluctuations, possibly in conjunction with experiments.

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“…In addition to that, there is a contribution by Giavazzi et al [19] who discuss the double enhancement of the concentration fluctuations in a binary liquid mixture due to the simultaneous effects of a temperature gradient and the proximity to an (equilibrium) critical point. Moreover, Martínez Pancorbo et al [20] incorporate the effects of buoyancy in the theory of fluctuations in a ternary mixture subjected to a temperature gradient; while Oprisan et al [21] present an experimental study of non-equilibrium fluctuations in magnetic colloidal suspensions, for which the application of an external magnetic field modifies the fluctuation intensity.…”

Section: Non-equilibrium Concentration Fluctuations Induced By the Somentioning

confidence: 99%

Topical issue on non-isothermal transport in complex fluids

et al. 2017

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Non-equilibrium concentration fluctuations in superparamagnetic nanocolloids

Cited by 5 publications

References 100 publications

Translational and Rotational Diffusion Coefficients of Gold Nanorods Dispersed in Mixtures of Water and Glycerol by Polarized Dynamic Light Scattering

Translational and Rotational Diffusion Coefficients of Gold Nanorods Dispersed in Mixtures of Water and Glycerol by Polarized Dynamic Light Scattering

Lattice Boltzmann simulations of nonequilibrium fluctuations in a nonideal binary mixture

Topical issue on non-isothermal transport in complex fluids

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