Structural Characterization of Magnetic Nanoparticles Suspensions, Using Magnetic Measurements (original) (raw)
Related papers
Journal of Colloid and Interface Science, 2000
Static magnetization curves and the magnetorheological effect were used to study the microstructural properties (agglomerate formation) of magnetic fluids and the properties of dispersed nanoparticles. Improved techniques for magnetogranulometry analysis and a formula for the magnetoviscous effect were proposed. The area of applicability of some existing models was studied. The density, distribution, and dimension of particles, as well as the thickness of the nonmagnetic layer were accurately determined from magnetic measurements. The Shliomis diameter and the effective anisotropy constant were determined from rheological and magnetorheological measurements using information obtained from magnetization curves.
Aggregation behaviour of magnetic nanoparticle suspensions investigated by magnetorelaxometry
Journal of Physics: Condensed Matter, 2006
The aggregation behaviour of magnetic nanoparticles (MNP) is a decisive factor for their application in medicine and biotechnology. We extended the moment superposition model developed earlier for describing the Néel relaxation of an ensemble of immobilized particles with a given size distribution by including the Brownian relaxation mechanism. The resulting cluster moment superposition model is used to characterize the aggregation of magnetic nanoparticles in various suspensions in terms of mean cluster size, aggregate fraction, and size dispersion. We found that in stable ferrofluids 50%-80% of larger magnetic nanoparticles are organized in dimers and trimers. The scaling of the relaxation curves with respect to MNP concentration is found to be a sensitive indicator of the tendency of a MNP suspension to form large aggregates, which may limit the biocompatibility of the preparation. Scaling violation was observed in aged water based ferrofluids, and may originate from damaged MNP shells. In biological media such as foetal calf serum, bovine serum albumin, and human serum we observed an aggregation behaviour which reaches a maximum at a specific MNP concentration. We relate this to agglutination of the particles by macromolecular bridges between the nanoparticle shells. Analysis of the scaling behaviour helps to identify the bridging component of the suspension medium that causes agglutination.
Magnetic spectroscopy as an aide in understanding magnetic fluids
Journal of Magnetism and Magnetic Materials, 2002
Accurate data on the frequency-dependent, complex susceptibility, χ(ω) = χ (ω)−iχ (ω) of magnetic fluids are vital for an understanding of the dynamic behavior of these colloidal suspensions. They enable relaxation mechanisms, both Brownian and Néel, as well as ferromagnetic resonance to be identified and investigated. They also provide a convenient means of determining the macroscopic and microscopic properties of the fluids, such as the mean particle radius,r, the mean value of anisotropy field, HA, the gyromagnetic constant, γ, and the damping constant, α. Also, through the medium of χ(ω) one can also investigate the frequency dependence of the loss tangent (tanδ) and power factor (sinδ) of such particulate systems. In this Chapter the abovementioned topics together with the relevant theory are presented and by means of suitable examples it is demonstrated how the appropriate equations may be employed to determine such properties from experimental data.
Characterization of magnetic colloids by means of magnetooptics
The European Physical Journal E, 2007
A new, efficient method for the characterization of magnetic colloids based on the Faraday effect is proposed. According to the main principles of this technique, it is possible to detect the stray magnetic field of the colloidal particles induced inside the magnetooptical layer. The magnetic properties of individual particles can be determined providing measurements in a wide range of magnetic fields. The magnetization curves of capped colloids and paramagnetic colloids were measured by means of the proposed approach. The registration of the magnetooptical signals from each colloidal particle in an ensemble permits the use of this technique for testing the magnetic monodispersity of colloidal suspensions.
Dimensional analysis of aqueous magnetic fluids
Applied Physics A-materials Science & Processing, 2007
A comparison of the synthesis and characterization of three aqueous magnetic fluids intended for biomedical applications is presented. Stable colloidal suspensions of iron oxide nanoparticles were prepared by a co-precipitation method with the magnetite cores being coated with β-cyclodextrin, tetramethylammonium hydroxide and citric acid. Rheological properties of the fluids were investigated, i.e. viscosity (capillary method) and surface tension (stalagmometric method) in correlation with their density (picnometric method). The dimensional distributions of the ferrophase particles physical diameter of these three magnetic fluids – revealed on the basis of transmission electron microscopy (TEM) data – as well as the diameter distributions of some other magnetic fluids presented in the literature, were comparatively analyzed using the box-plot statistical method. In order to extract complementary data on the magnetic diameter of an iron oxide core, magnetization measurements as well as X-ray diffraction pattern analysis were carried out. Interpretation of all the measurement data was accomplished by assessing the suitability of the three magnetic fluid samples from the viewpoint of their stability and biocompatibility.
From magnetic fluids up to complex biocompatible nanosized magnetic systems
2008
The paper presents magnetic fluid as an excellent material platform for producing more complex magnetic drug delivery systems. In addition, the paper discusses the nanoparticle morphological (electron microscopy) and structural (X-ray diffraction) characterizations. Mössbauer spectroscopy and photoacoustic spectroscopy are revisited as key tools in the characterization of the magnetic core and diamagnetic shell of the magnetic nanoparticle, respectively.
Structure and magnetism in magnetic nanoparticles
Magnetic Nanoparticles: From Fabrication to Clinical Applications, 2012
Scale reduction in materials leads to profound changes in their inner structure, which in turn greatly modifies the intrinsic electronic and optical properties. Magnetic ones do so. In the case of magnetic nanoparticles, these changes have meant the departure from some of the established laws governing the magnetic phenomena observed in bulk materials for the time being. The implications of these new phenomena on developing new technologies are manifold. On the one hand, the research done in magnetic nanoparticles over the last decades – more than two hundred thousand peer-reviewed publications - is now definitely moving from the theoretical grounds to the real applications arena, especially in medicine, as attested by both the increasing number of patents and companies formed around them. On the other hand, and also in relation to medical applications, the effects that many nanostructures could have on health still remain unknown, challenging the Food and Drug Agency (FDA) in USA or the European Medicines Agency (EMEA) to face continuous regulatory issues concerning the commercialisation of nanotechnology-based products and their eventual consumption, certainly slowing down the rate at which they would become available to the final consumer. The aim of this chapter is to present a concise overview of key concepts in magnetism applied to nanoparticles along with some of the instrumental techniques reasonably available in many laboratories to study the properties of magnetic nanoparticles. In accordance to the topic of this book, references to issues that could have a bearing on their potential uses in biomedicine and other related disciplines are also provided where appropriate. Finally, a good deal of what is said here applies to many types of magnetic materials, but given their relevance in medicine compared to other fine particle systems the text is rather focused on ferrimagnetic iron oxides, namely maghemite (g-Fe2O3) and magnetite (Fe3O4).
Study of dynamical behavior of magnetic nanoparticles suspension in biological fluids
Colloid and Interface Science Communications, 2020
The dynamical response of oleic acid (OA), oleic acid/2, 3-dimercaptosuccinic acid (OA/DMSA) and oleic/citric acid (OA/CA) coated iron oxide (Fe 3 O 4) nanoparticles in water and phosphate buffer saline (pH = 7) is investigated by dynamic light scattering (DLS). The aggregation and fragmentation rate of suspended nanoparticles at different concentration of buffers is evaluated. Iron oxide nanoparticles coated with OA, OA/DMSA and OA/CA are synthesized via thermal decomposition and ligand exchange wet chemical route. The hydrodynamic spherical diameter of OA, OA/DMSA and OA/CA coated nanoparticles, measured at room temperature are found to be 83.6, 133.7 and 147.7 nm. The formation of clusters and their distribution in the magnetic nanoparticles suspension is obtained from DLS experiments. It is correlated with the theoretical model based on diffusion dominated aggregation model. The growth rate β due to tailored aggregation and fragmentation processes at different volume fractions in different solvents, shows power law dependence as < k(t) >~t β at intermediate time scale. The slope β for OA/DMSA and OA/CA coated MNPs is obtained to be 0.09 and 0.1 respectively. These studies are therefore extremely relevant and can provide guidelines for research in biological fluids such as serum, plasma etc.
Designing magnetic composite materials using aqueous magnetic fluids
In this paper, we report how to take advantage of the good knowledge of both the chemistry and the stability of an aqueous magnetic colloidal suspension to realize different magnetic composites. The osmotic pressure of the magnetic nanoparticles is set prior to the realization of the composite to a given value specially designed for the purpose of each hybrid material: magnetic particles in polymer networks, particles as probes for studying the structure of clay suspensions and shape modification of giant liposomes.