Critical Onset of Layering in Sedimenting Suspensions of Nanoparticles

Бутенко, А. В.; Nanikashvili, Pilkhaz; Zitoun, David; Sloutskin, Eli

doi:10.1103/physrevlett.112.188301

Cited by 11 publications

(8 citation statements)

References 26 publications

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“…The herein observed phenomena of non-ideality in AC experiments is not new and was recently discussed in detail by Butenko et al 33 It was shown that temperature gradients can induce such convection, which can be followed by layering in the measurement cell. 34 This in turn will affect the width of distributions or can even result in false peaks.…”

Section: Assessment Of Particle Size Distributions and Monitoring Of mentioning

confidence: 50%

New possibilities of accurate particle characterisation by applying direct boundary models to analytical centrifugation

et al. 2015

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Analytical centrifugation (AC) is a powerful technique for the characterisation of nanoparticles in colloidal systems. As a direct and absolute technique it requires no calibration or measurements of standards. Moreover, it offers simple experimental design and handling, high sample throughput as well as moderate investment costs. However, the full potential of AC for nanoparticle size analysis requires the development of powerful data analysis techniques. In this study we show how the application of direct boundary models to AC data opens up new possibilities in particle characterisation. An accurate analysis method, successfully applied to sedimentation data obtained by analytical ultracentrifugation (AUC) in the past, was used for the first time in analysing AC data. Unlike traditional data evaluation routines for AC using a designated number of radial positions or scans, direct boundary models consider the complete sedimentation boundary, which results in significantly better statistics. We demonstrate that meniscus fitting, as well as the correction of radius and time invariant noise significantly improves the signal-to-noise ratio and prevents the occurrence of false positives due to optical artefacts. Moreover, hydrodynamic non-ideality can be assessed by the residuals obtained from the analysis. The sedimentation coefficient distributions obtained by AC are in excellent agreement with the results from AUC. Brownian dynamics simulations were used to generate numerical sedimentation data to study the influence of diffusion on the obtained distributions.Our approach is further validated using polystyrene and silica nanoparticles. In particular, we demonstrate the strength of AC for analysing multimodal distributions by means of gold nanoparticles.

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Section: Assessment Of Particle Size Distributions and Monitoring Of mentioning

confidence: 50%

New possibilities of accurate particle characterisation by applying direct boundary models to analytical centrifugation

et al. 2015

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“…It is useful to point out that, in the presence of even minimal lateral temperature gradients, a stretching interface may become unstable, leading to stratification and formation of a banded profile. Although known for almost a century [27], this curious effect has usually been observed for extremely dilute dispersions, where substantial spreading of the interface takes place before it reaches a time-invariant shape [28,29]. Our evidence suggests that stratified settling may also occur in rather concentrated suspensions of strongly attractive monodisperse particles.…”

mentioning

confidence: 56%

Colloidal Swarms Can Settle Faster than Isolated Particles: Enhanced Sedimentation near Phase Separation

2016

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By experimenting on model colloids where depletion forces can be carefully tuned and quantified, we show that attractive interactions consistently "promote" particle settling, so much that the sedimentation velocity of a moderately concentrated dispersion can even exceed its single-particle value. At larger particle volume fraction ϕ, however, hydrodynamic hindrance eventually takes over. Hence, v(ϕ) actually displays a nonmonotonic trend that may threaten the stability of the settling front to thermal perturbations. Finally, by discussing a representative case, we show that these results are relevant to the investigation of protein association effects by ultracentrifugation.

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“…Few reports argue that the formation of such steps can allude to convective instabilities leading to the formation of layers during sedimentation. For instance, Butenko et al [59] noticed the formation of successive plateaus, when they measured Cu-Ag nanoparticles. It is reported that such convective instabilities arise primarily due to (i) temperature gradients across the cuvette and (ii) rectangular shaped sample cell.…”

Section: Tem Imaging Of Inksmentioning

confidence: 99%

On the State and Stability of Fuel Cell Catalyst Inks

Bapat

Giehl²,

Kohsakowski³

et al. 2021

Preprint

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Catalyst layers (CL), as an active component of the catalyst coated membrane (CCM), form the heart of the proton electrolyte membrane fuel cell (PEMFC). For optimum performance of the fuel cell, obtaining suitable structural and functional characteristics for the CL is crucial. Direct tuning of the microstructure and morphology of the CL is non-trivial; hence catalyst inks as CL precursors need to be modulated, which are then applied onto a membrane to form the CCM. Obtaining favorable dispersion characteristics forms an important prerequisite in engineering catalyst inks for large scale manufacturing. In order to facilitate a knowledge-based approach for developing fuel cell inks, this work introduces new tools and methods to study both the dispersion state and stability characteristics, simultaneously. Catalyst inks were prepared using different processing methods, which include stirring and ultrasonication. The proposed tools are used to characterize and elucidate the effects of the processing method. Structural characterization of the dispersed particles and their assemblages was carried out by means of transmission electron microscopy. Analytical centrifugation (AC) was used to study the state and stability of the inks. Herein, we introduce new concepts, S score, and stability trajectory, for a time-resolved assessment of inks in their native state using AC. The findings were validated and rationalized using transmittograms as a direct visualization technique. The flowability of inks was investigated by rheological measurements. It was found that probe sonication only up to an optimum amplitude leads to a highly stable colloidal ink.

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Critical Onset of Layering in Sedimenting Suspensions of Nanoparticles

Cited by 11 publications

References 26 publications

New possibilities of accurate particle characterisation by applying direct boundary models to analytical centrifugation

New possibilities of accurate particle characterisation by applying direct boundary models to analytical centrifugation

Colloidal Swarms Can Settle Faster than Isolated Particles: Enhanced Sedimentation near Phase Separation

On the State and Stability of Fuel Cell Catalyst Inks

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