Simultaneous Absolute Determination of Particle Size and Effective Density of Submicron Colloids by Disc Centrifuge Photosedimentometry

Kamiti, Mungai; Boldridge, David; Ndoping, Linda M.; Remsen, Edward E.

doi:10.1021/ac3022086

Cited by 25 publications

(26 citation statements)

References 23 publications

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“…The corresponding particle size is obtained from the sedimentation time taking density and viscosity profiles into account. 24 Colloidal gold particles with a nominal diameter of 60 nm were used to quantify the density gradient. The disc rotation speed was set to either 10000 or 15000 rpm depending on the particle size.…”

Section: Methodsmentioning

confidence: 99%

Monodisperse PEGylated Spheres: An Aqueous Colloidal Model System

2014

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Fluorinated core–shell spheres have been synthesized using a novel semibatch emulsion polymerization protocol employing slow feeding of the initiator. The synthesis results in aqueous dispersions of highly monodisperse spheres bearing a well-defined poly(ethylene glycol) graft (PEGylation). Measurements are consistent with the synthesis achieving a high grafting density that moreover consists of a single PEG layer with the polymer significantly elongated beyond its radius of gyration in bulk. The fluorination of the core of the particles confers a low index of refraction such that the particles can be refractive index matched in water through addition of relatively small amounts of a cosolvent, which enables the use of optical and laser-based methods for studies of concentrated systems. The systems exhibit an extreme stability in NaCl solutions, but attractions among particles can be introduced by addition of other salts, in which case aggregation is shown to be reversible. The PEGylated sphere dispersions are expected to be ideally suited as model systems for studies of the effect of PEG-mediated interactions on, for instance, structure, dynamics, phase behavior, and rheology.

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Section: Methodsmentioning

confidence: 99%

Monodisperse PEGylated Spheres: An Aqueous Colloidal Model System

2014

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“…39 The corrected particle density (ρ ps ) can be estimated by means of two CLS measurements in two media of different density. For estimation of ρ ps of the SAS studied here, the so called 'zero velocity approach' was used.…”

Section: Scanning Electron Microscopy In High Vacuum and Liquid Setupmentioning

confidence: 99%

A uniform measurement expression for cross method comparison of nanoparticle aggregate size distributions

Dudkiewicz

Wagner

Lehner

et al. 2015

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Available measurement methods for nanomaterials are based on very different measurement principles and hence produce different values when used on aggregated nanoparticle dispersions. This paper provides a solution for relating measurements of nanomaterials comprised of nanoparticle aggregates determined by different techniques using a uniform expression of a mass equivalent diameter (MED). The obtained solution is used to transform into MED the size distributions of the same sample of synthetic amorphous silica (nanomaterial comprising aggregated nanoparticles) measured by six different techniques: scanning electron microscopy in both high vacuum (SEM) and liquid cell setup (Wet-SEM); gas-phase electrophoretic mobility molecular analyzer (GEMMA); centrifugal liquid sedimentation (CLS); nanoparticle tracking analysis (NTA); and asymmetric flow field flow fractionation with inductively coupled plasma mass spectrometry detection (AF4-ICP-MS). Transformed size distributions are then compared between the methods and conclusions drawn on methods' measurement accuracy, limits of detection and quantification related to the synthetic amorphous silca's size. Two out of the six tested methods (GEMMA and AF4-ICP-MS) cross validate the MED distributions between each other, providing a true measurement. The measurement accuracy of other four techniques is shown to be compromised either by the high limit of detection and quantification (CLS, NTA, Wet-SEM) or the sample preparation that is biased by increased retention of smaller nanomaterials (SEM). This study thereby presents a successful and conclusive cross-method comparison of size distribution measurements of aggregated nanomaterials. The authors recommend the uniform MED size expression for application in nanomaterial risk assessment studies and clarifications in current regulations and definitions concerning nanomaterials.

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“…Perhaps more importantly, the lack of radial scans monitoring the entire solution column prohibits diagnostics of systematic errors in the model or experimental problems, including significant contributions to particle migration from diffusion, convection, systematic noise contributions, and/or signal offsets from sedimenting small co-solute molecules. Fixed-radius detection has been applied recently in conjunction with a multiwavelength detector design for AUC 55 , and is used in disc centrifuges 56–58 . However, in the latter approach, similar to band centrifugation configurations in AUC, samples are injected causing sedimenting lamella that will exhibit reduced, but more complex simultaneous detection and radial dilution effects.…”

Section: Resultsmentioning

confidence: 99%

Sedimentation coefficient distributions of large particles

Schuck

2016

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The spatial and temporal evolution of concentration boundaries in sedimentation velocity analytical ultracentrifugation reports on the size distribution of particles with high hydrodynamic resolution. For large particles such as large protein complexes, fibrils, viral particles, or nanoparticles, sedimentation conditions usually allow migration from diffusion to be neglected relative to sedimentation. In this case, the shape of the sedimentation boundaries of polydisperse mixtures relates directly to the underlying size-distributions. Integral and derivative methods for calculating sedimentation coefficient distributions g*(s) of large particles from experimental boundary profiles have been developed previously, and are recapitulated here in a common theoretical framework. This leads to a previously unrecognized relationship between g*(s) and the time-derivative of concentration profiles. Of closed analytical form, it is analogous to the well-known Bridgman relationship for the radial derivative. It provides a quantitative description of the effect of substituting the time-derivative by scan differences with finite time intervals, which appears as a skewed box average of the true distribution. This helps to theoretically clarify the differences between results from time-derivative method and the approach of directly fitting the integral definition of g*(s) to the entirety of experimental boundary data.

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Simultaneous Absolute Determination of Particle Size and Effective Density of Submicron Colloids by Disc Centrifuge Photosedimentometry

Cited by 25 publications

References 23 publications

Monodisperse PEGylated Spheres: An Aqueous Colloidal Model System

Monodisperse PEGylated Spheres: An Aqueous Colloidal Model System

A uniform measurement expression for cross method comparison of nanoparticle aggregate size distributions

Sedimentation coefficient distributions of large particles

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