Suspensions of Colloidal Aggregates

Babick, Frank

doi:10.1007/978-3-319-30663-6_4

Cited by 16 publications

(28 citation statements)

References 161 publications

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“…Experiments were conducted along with noninvasive backscattering detection (NIBS), because CaCO 3 causes multiple scattering due to its high contrast in the refractive index (RI). 54 Using NIBS, the multiple scattering effect was reduced 55 , 56 and the scattering information was obtained at 173°. If the particle can be considered to be spherical, the Rayleigh scattering intensity is related to the sixth power of the hydrodynamic radius of the particle ( I R α R H 6 ) 57 and that same hydrodynamic radius is related to the translational diffusion coefficient via the Stokes–Einstein relationship 53 , 58 , 59 where k b is the Boltzmann constant (m 2 kg s –2 K –1 ), T is the absolute temperature (K), μ is the dynamic viscosity (kg s –1 m –1 ), R H is the hydrodynamic diameter (m), and D Trans is the translational diffusion coefficient (m 2 s –1 ).…”

Section: Methodsmentioning

confidence: 99%

Controlling CaCO₃Particle Size with {Ca²⁺}:{CO₃^2–} Ratios in Aqueous Environments

Seepma

Ruiz‐Hernandez

Nehrke

et al. 2021

Crystal Growth & Design

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The effect of stoichiometry on the new formation and subsequent growth of CaCO 3 was investigated over a large range of solution stoichiometries (10 –4 < r aq < 10 4 , where r aq = {Ca 2+ }:{CO 3 2– }) at various, initially constant degrees of supersaturation (30 < Ω cal < 200, where Ω cal = {Ca 2+ }{CO 3 2– }/ K sp ), pH of 10.5 ± 0.27, and ambient temperature and pressure. At r aq = 1 and Ω cal < 150, dynamic light scattering (DLS) showed that ion adsorption onto nuclei (1–10 nm) was the dominant mechanism. At higher supersaturation levels, no continuum of particle sizes is observed with time, suggesting aggregation of prenucleation clusters into larger particles as the dominant growth mechanism. At r aq ≠ 1 (Ω cal = 100), prenucleation particles remained smaller than 10 nm for up to 15 h. Cross-polarized light in optical light microscopy was used to measure the time needed for new particle formation and growth to at least 20 μm. This precipitation time depends strongly and asymmetrically on r aq . Complementary molecular dynamics (MD) simulations confirm that r aq affects CaCO 3 nanoparticle formation substantially. At r aq = 1 and Ω cal ≫ 1000, the largest nanoparticle in the system had a 21–68% larger gyration radius after 20 ns of simulation time than in nonstoichiometric systems. Our results imply that, besides Ω cal , stoichiometry affects particle size, persistence, growth time, and ripening time toward micrometer-sized crystals. Our results may help us to improve the understanding, prediction, and formation of CaCO 3 in geological, industrial, and geo-engineering settings.

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Section: Methodsmentioning

confidence: 99%

Controlling CaCO₃Particle Size with {Ca²⁺}:{CO₃^2–} Ratios in Aqueous Environments

Seepma

Ruiz‐Hernandez

Nehrke

et al. 2021

Crystal Growth & Design

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“…Colloidal particles dispersed in a fluid medium are widely considered to be an ideal system where self-assembly can be explored, since they can be resolved and tracked in real time using optical microscopy [ 1 ]. The aggregation of colloidal particles is often the outcome of steric stabilization by electrostatic repulsion, which is achieved by modifying the salt concentration or by adding chemicals as stabilizing agents, as in the case of gold colloids [ 2 ] or silica and polystyrene particles [ 3 , 4 ].…”

Section: Introductionmentioning

confidence: 99%

Self-Assembled Structures of Colloidal Dimers and Disks on a Spherical Surface

Dlamini

Prestipino

Pellicane

2021

Entropy

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We study self-assembly on a spherical surface of a model for a binary mixture of amphiphilic dimers in the presence of guest particles via Monte Carlo (MC) computer simulation. All particles had a hard core, but one monomer of the dimer also interacted with the guest particle by means of a short-range attractive potential. We observed the formation of aggregates of various shapes as a function of the composition of the mixture and of the size of guest particles. Our MC simulations are a further step towards a microscopic understanding of experiments on colloidal aggregation over curved surfaces, such as oil droplets.

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“…SAS is also synthetized in the gaseous phase from SiCl 4 [9,10], and this material is referred to as pyrogenic or fumed silica (FS). While CS is usually supplied as a stable aqueous suspension of well-dispersed nanoparticles [11], PS, FS and SG are delivered as dry powders which consist of aggregates or agglomerates, both of which are formed by nanosized primary silica (SiO 2 ) particles [9,12].…”

Section: Introductionmentioning

confidence: 99%

Effects of Ultrasonic Dispersion Energy on the Preparation of Amorphous SiO2 Nanomaterials for In Vitro Toxicity Testing

Wiemann¹,

Vennemann²,

Stintz

et al. 2018

Nanomaterials

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Synthetic amorphous silica (SAS) constitute a large group of industrial nanomaterials (NM). Based on their different production processes, SAS can be distinguished as precipitated, fumed, gel and colloidal. The biological activity of SAS, e.g., cytotoxicity or inflammatory potential in the lungs is low but has been shown to depend on the particle size, at least for colloidal silica. Therefore, the preparation of suspensions from highly aggregated or agglomerated SAS powder materials is critical. Here we analyzed the influence of ultrasonic dispersion energy on the biologic activity of SAS using NR8383 alveolar macrophage (AM) assay. Fully characterized SAS (7 precipitated, 3 fumed, 3 gel, and 1 colloidal) were dispersed in H2O by stirring and filtering through a 5 µm filter. Aqueous suspensions were sonicated with low or high ultrasonic dispersion (USD) energy of 18 or 270 kJ/mL, respectively. A dose range of 11.25–90 µg/mL was administered to the AM under protein-free conditions to detect particle-cell interactions without the attenuating effect of proteins that typically occur in vivo. The release of lactate dehydrogenase (LDH), glucuronidase (GLU), and tumor necrosis factor α (TNF) were measured after 16 h. Hydrogen peroxide (H2O2) production was assayed after 90 min. The overall pattern of the in vitro response to SAS (12/14) was clearly dose-dependent, except for two SAS which showed very low bioactivity. High USD energy gradually decreased the particle size of precipitated, fumed, and gel SAS whereas the low adverse effect concentrations (LOECs) remained unchanged. Nevertheless, the comparison of dose-response curves revealed slight, but uniform shifts in EC50 values (LDH, and partially GLU) for precipitated SAS (6/7), gel SAS (2/3), and fumed SAS (3/3). Release of TNF changed inconsistently with higher ultrasonic dispersion (USD) energy whereas the induction of H2O2 was diminished in all cases. Electron microscopy and energy dispersive X-ray analysis showed an uptake of SAS into endosomes, lysosomes, endoplasmic reticulum, and different types of phagosomes. The possible effects of different uptake routes are discussed. The study shows that the effect of increased USD energy on the in vitro bioactivity of SAS is surprisingly small. As the in vitro response of AM to different SAS is highly uniform, the production process per se is of minor relevance for toxicity.

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Suspensions of Colloidal Aggregates

Cited by 16 publications

References 161 publications

Controlling CaCO₃Particle Size with {Ca²⁺}:{CO₃^2–} Ratios in Aqueous Environments

Controlling CaCO₃Particle Size with {Ca²⁺}:{CO₃^2–} Ratios in Aqueous Environments

Self-Assembled Structures of Colloidal Dimers and Disks on a Spherical Surface

Effects of Ultrasonic Dispersion Energy on the Preparation of Amorphous SiO2 Nanomaterials for In Vitro Toxicity Testing

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Suspensions of Colloidal Aggregates

Cited by 16 publications

References 161 publications

Controlling CaCO3Particle Size with {Ca2+}:{CO32–} Ratios in Aqueous Environments

Controlling CaCO3Particle Size with {Ca2+}:{CO32–} Ratios in Aqueous Environments

Self-Assembled Structures of Colloidal Dimers and Disks on a Spherical Surface

Effects of Ultrasonic Dispersion Energy on the Preparation of Amorphous SiO2 Nanomaterials for In Vitro Toxicity Testing

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Controlling CaCO₃Particle Size with {Ca²⁺}:{CO₃^2–} Ratios in Aqueous Environments

Controlling CaCO₃Particle Size with {Ca²⁺}:{CO₃^2–} Ratios in Aqueous Environments