scholarly journals Applying SAXS to study the structuring of Fe3O4 magnetic nanoparticles in colloidal suspensions

DYNA ◽  
2019 ◽  
Vol 86 (209) ◽  
pp. 135-140 ◽  
Author(s):  
Jenny Mera Cordoba ◽  
Diego Fernando Coral-Coral
Keyword(s):  
Particle Size ◽  
Magnetic Nanoparticles ◽  
Mathematical Models ◽  
Size Distribution ◽  
Interaction Strength ◽  
Colloidal Suspensions ◽  
Compact Structure ◽  
Aggregation State ◽  
Broad Size Distribution ◽  
Saxs Analysis

In this work, Small Angle X-ray Scattering (SAXS) patterns, obtained from two different aqueous colloidal suspensions of magnetite nanoparticles electrostatically stabilized with citric acid, were fitted using three different mathematical models in order to describe the particle size distribution and aggregation state. The colloidal suspensions differ in the mean particle size (4.5±1.0 nm and 5.5±1.1 nm) and the aqueous stabilization, allowing control of the strength of the interaction strength between particles. The models used for SAXS analysis, reveal that the particles are almost spherical with a broad size distribution, and that particles in each suspension are aggregated and are subject to an attractive interaction potential, typical for magnetic nanoparticles. For the better-stabilized sample, ramified chain-like aggregates were found, and for the less-stabilized sample, a more compact structure was determined. The size distribution obtained by applying SAXS mathematical models are in agreement with the size distribution determined using Transmission Electronic Microscopy(TEM)

Tailoring Local Hysteresis in Small Clusters of Dipolar Interacting Magnetic Nanoparticles

NANO ◽  
2021 ◽  
pp. 2150104
Author(s):  
Manish Anand
Keyword(s):  
Particle Size ◽  
Magnetic Nanoparticles ◽  
Hysteresis Loop ◽  
Cluster Size ◽  
Interaction Strength ◽  
Dipolar Interaction ◽  
Dipolar Field ◽  
Area Formula ◽  
Loop Area ◽  
Hysteresis Loop Area

Using first-principle calculations and kinetic Monte Carlo simulation, we study the local and averaged hysteresis in tiny clusters of [Formula: see text] magnetic nanoparticles (MNPs) or [Formula: see text]-mers. We also analyze the variation of local dipolar field acting on the constituent nanoparticles as a function of the external magnetic field. The dipolar interaction is found to promote chain-like arrangement in such a cluster. Irrespective of cluster size, the local hysteresis response depends strongly on the corresponding dipolar field acting on a nanoparticle. In a small [Formula: see text]-mer, there is a wide variation in local hysteresis as a function of nanoparticle position. On the other hand, the local hysteresis is more uniform for larger [Formula: see text]-mer, except for MNPs at the boundary. In the case of superparamagnetic nanoparticle and weak dipolar interaction, the local hysteresis loop area [Formula: see text] is minimal and depends weakly on the [Formula: see text]-mer size. While for ferromagnetic counterpart, [Formula: see text] is considerably large even for weakly interacting MNPs. The value of [Formula: see text] is found to be directly proportional to the dipolar field acting on the nanoparticle. The dipolar interaction and [Formula: see text]-mer size also enhance the coercivity and remanence. There is always an increase in [Formula: see text] with cluster size and dipolar interaction strength. Similarly, the averaged hysteresis loop area [Formula: see text] also depends strongly on the [Formula: see text]-mer size, particle size and dipolar interaction strength. [Formula: see text] and [Formula: see text] always increase with [Formula: see text]-mer size and dipolar interaction strength. Interestingly, the value of [Formula: see text] saturates for [Formula: see text] and considerable dipolar interaction irrespective of particle size. We believe that this work would help understand the intricate role of dipolar interaction on hysteresis and the organizational structure of MNPs and their usage in drug delivery and hyperthermia applications.

scholarly journals Effect of ultrasonication on the size distribution and stability of cellulose nanocrystals in suspension: an asymmetrical flow field-flow fractionation study

Cellulose ◽  
2021 ◽  
Vol 28 (16) ◽  
pp. 10221-10238
Author(s):  
Christoph Metzger ◽  
Roland Drexel ◽  
Florian Meier ◽  
Heiko Briesen
Keyword(s):  
Particle Size ◽  
Light Scattering ◽  
Flow Field ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Cellulose Nanocrystals ◽  
Colloidal Suspensions ◽  
Field Flow Fractionation ◽  
Ultrasound Energy ◽  
Flow Fractionation

AbstractCellulose nanocrystals (CNCs) are bio-based building blocks for sustainable advanced materials with prospective applications in polymer composites, emulsions, electronics, sensors, and biomedical devices. However, their high surface area-to-volume ratio promotes agglomeration, which restrains their performance in size-driven applications, thereby hindering commercial CNC utilization. In this regard, ultrasonication is commonly applied to disperse CNCs in colloidal suspensions; however, ultrasonication methodology is not yet standardized and knowledge of the effects of ultrasound treatments on CNC size distribution is scarce. The major goals of this study were attributed to targeted breakage of CNC agglomerates and clusters by ultrasound. The evolution of particle size distribution and potential de-sulfation by ultrasonication as well as the long-term stability of ultrasonicated CNC suspensions were investigated. Colloidal suspensions of sulfated CNCs were isolated from cotton α-cellulose. Effects of ultrasonication on particle size distribution were determined by asymmetrical flow field-flow fractionation (AF4) coupled with on-line multi-angle light scattering and ultraviolet spectroscopy. These results were complemented with off-line dynamic light scattering. High ultrasound energy densities facilitated cumulative dispersion of CNC clusters. Consequently, the mean rod length decreased logarithmically from 178.1 nm at an ultrasound energy input of 2 kJ g−1 CNC to 141.7 nm (− 20%) at 40 kJ g−1 CNC. Likewise, the hydrodynamic diameter of the particle collective decreased logarithmically from 94.5 to 73.5 nm (− 22%) in the same processing window. While the rod length, below which 95 wt% of the CNCs were found, decreased from 306.5 to 231.8 nm (− 24%) from 2 to 40 kJ g−1 CNC, the shape factor of the main particle fraction ranged from 1.0 to 1.1, which indicated a decreasing number of dimers and clusters in the particle collective. In summary, progressing ultrasonication caused a shift of the particle length distribution to shorter particle lengths and simultaneously induced narrowing of the distribution. The suspension’s electrical conductivity concurrently increased, which has been attributed to faster diffusion of smaller particles and exposure of previously obscured surface charges. Colloidal stability, investigated through electrical AF4 and electrophoretic light scattering, was not affected by ultrasonication and, therefore, indicates no de-sulfation by the applied ultrasound treatment. Occurrence of minor CNC agglomeration at low ultrasound energy densities over the course of 6 months suggest the effect was not unmitigatedly permanent.

scholarly journals Analysis of mathematical models for description of the fractional composition of disperse elastic fillers

2019 ◽  
Vol 7 (5) ◽  
pp. 62-78 ◽  
Author(s):  
Yu. A. Naumova ◽  
I. V. Gordeeva
Keyword(s):  
Particle Size ◽  
High Temperature ◽  
Mathematical Models ◽  
Size Distribution ◽  
Fractional Composition ◽  
Cumulative Distribution ◽  
Normal Distribution Function ◽  
Rubber Powder ◽  
Powder Particles ◽  
Temperature Shear

The paper presents a comparative analysis of integral and differential mathematical models describing the particle size distribution of dispersed elastic fillers. Crushed vulcanizates obtained by high temperature shear grinding were studied as objects of research. Technogenic waste – waste passenger car tires and rubber elements of gas mask facepieces – were used as raw materials. Data on the distribution of the crushed vulcanizate particles were obtained by laser diffraction using the particle size analyzer Fritsch Analysette 22 Microtec plus (“Fritsch”, Germany). It was found that the distribution curves are unimodal asymmetric curves. Search and analysis of mathematical models were carried out using a specialized software product TableCurve 2D v5.01 (Jandel Scientific). Four- and five-parameter equations pertaining to the class of logistic models were tested to describe the integral cumulative distribution curves of the rubber powder particles. In order to justify the choice of a suitable mathematical model to describe the fractional composition of the crushed vulcanizes, the adequacy of the models was assessed, the structural characteristics of the variation series, the statistical moments of distribution and the indicators of its shape were determined. It was found that according to a number of criteria it is appropriate to use the logarithmically normal distribution function for the description and analysis of the rubber powders fractional composition. It is suggested that regardless of the nature of the feedstock, the described implementation of high temperature shear grinding provides products having an identical shape of rubber powder particles size distribution.

scholarly journals Nanoparticle Tracking Analysis: A powerful tool for characterizing magnetosome preparations

2020 ◽  
Author(s):  
Alfred Fernández-Castané ◽  
Hong Li ◽  
Stephan Joseph ◽  
Moritz Ebeler ◽  
Matthias Franzreb ◽  
...  
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Particle Concentration ◽  
Sodium Dodecyl ◽  
Cost Effective ◽  
Fold Increase ◽  
Resolving Power ◽  
Nanoparticle Tracking Analysis ◽  
Aggregation State ◽  
Cost Effective Technique

AbstractNanoparticle Tracking Analysis (NTA) has been employed to measure the particle concentration and size distribution of magnetosomes extracted and purified from Magnetospirillum gryphiswaldense MSR-1, and then exposed to probe ultrasonication for various times, or 1% (w/v) sodium dodecyl sulphate (SDS) for 1 h. Particle concentration increased 3.7-fold over the first 15 min of ultrasonication (from 2 × 108 to >7.3 × 108 particles mL−1), but fell steeply to ~3.6 × 108 particles mL−1 after 20 min. NTA of untreated magnetosome preparation confirmed a wide particle distribution dominated by larger species (D[1,0] = 312 nm; Dn50 = 261 nm; mode = 243 nm) with no particles in the size range of isolated single magnetosomes. After 5 min of ultrasonication the whole particle size distribution shifted to smaller size (D[1,0] = 133 nm; Dn50 = 99 nm; mode = 36 nm, corresponding to individual magnetosomes), but longer treatment times (15 and 20 min) reversed the previous transition; all characteristic numbers of the particle size distributions increased and very few small particles were detected. Side-by-side comparison of NTA and TEM sizing data revealed remarkable similarity at low ultrasonication times, with both showing single magnetosomes accounted for ~30% population after 5 min. Exposure of magnetosomes to SDS resulted in a ~3-fold increase in particle concentration to 5.8 × 108 particles mL−1, narrowing of the size distribution and gross elimination of particles below 60 nm. We conclude that NTA is a rapid cost-effective technique for measuring particle number, size distribution and aggregation state of magnetosomes in solution, but requires further work to improve its resolving power.

scholarly journals Droplet-based synthesis of homogeneous magnetic iron oxide nanoparticles

2018 ◽  
Vol 9 ◽  
pp. 2413-2420 ◽  
Author(s):  
Christian D Ahrberg ◽  
Ji Wook Choi ◽  
Bong Geun Chung
Keyword(s):  
Particle Size ◽  
Iron Oxide ◽  
Magnetic Nanoparticles ◽  
Size Distribution ◽  
Iron Oxide Nanoparticles ◽  
Residence Time ◽  
Medical Applications ◽  
Oxide Nanoparticles ◽  
Magnetic Iron Oxide Nanoparticles ◽  
Magnetic Iron Oxide

Nanoparticles have gained large interest in a number of different fields due to their unique properties. In medical applications, for example, magnetic nanoparticles can be used for targeting, imaging, magnetically induced thermotherapy, or for any combination of the three. However, it is still a challenge to obtain narrowly dispersed, reproducible particles through a typical lab-scale synthesis when researching these materials. Here, we present a droplet capillary reactor that can be used for the synthesis of magnetic iron oxide nanoparticles. Compared to conventional batch synthesis, the particles synthesized in our droplet reactor have a narrower size distribution and a higher reproducibility. Furthermore, we demonstrate how the particle size can be changed from 5.2 ± 0.9 nm to 11.8 ± 1.7 nm by changing the reaction temperature and droplet residence time in the droplet capillary reactor.

scholarly journals A comparison of methods for the measurement of the particle-size distribution of magnetic nanoparticles

2007 ◽  
Vol 40 (s1) ◽  
pp. s495-s500 ◽  
Author(s):  
R. C. Woodward ◽  
J. Heeris ◽  
T. G. St. Pierre ◽  
M. Saunders ◽  
E. P. Gilbert ◽  
...  
Keyword(s):  
Particle Size ◽  
Magnetic Nanoparticles ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Comparison Of Methods
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