Time-dependent AC magnetometry and chain formation in magnetite: the influence of particle size, initial temperature and the shortening of the relaxation time by the applied field

Abstract

Magnetite nanoparticles (MNPs) with 12, 34 and 53 nm sizes have been measured by ac-magnetometry at 50 kHz and 57 mT maximum applied field. The MNPs form chains under the...

A Fast, Reliable Oil-In-Water Microemulsion Procedure for Silica Coating of Ferromagnetic Zn Ferrite Nanoparticles Capable of Inducing Cancer Cell Death In Vitro

“…Alternatively, the silica coating increases the hydrodynamic diameters of clusters, reducing their Brownian motion and consequently, the SAR diminishes. However, a closer look at the TEM images in Figure 3a individual NPs, and it ultimately leads to an enhancement of the heating performances, as was previously reported for magnetite NPs with comparable sizes and magnetic properties [51]. On the contrary, the silica layer prevents the Zn0.4Fe2.6O4 NPs within clusters from entering into physical contact and associating in long chains along the AMF lines.…”

“…This big difference can be explained by the potential of uncoated Zn 0.4 Fe 2.6 O 4 NPs to organize in chains under the influence of the AMF. This type of organization increases the magnetic anisotropy of the assembly as compared to individual NPs, and it ultimately leads to an enhancement of the heating performances, as was previously reported for magnetite NPs with comparable sizes and magnetic properties [ 51 ]. On the contrary, the silica layer prevents the Zn 0.4 Fe 2.6 O 4 NPs within clusters from entering into physical contact and associating in long chains along the AMF lines.…”

Simulating the Self-Assembly and Hysteresis Loops of Ferromagnetic Nanoparticles with Sticking of Ligands

“…However, other explanations for the disordered clump shapes may include the fact that single particles are not perfectly spherical (thus the point dipole approximation breaks down) or that there are size distributions among particles [46,47]. The size of the magnetic moment and the density of particles may play a role in the shape of formed agglomerates [48,49]. Furthermore, taking into account hydrodynamic interactions between particles will change how they approach each other when self-assembling.…”

Perspective: magnetic nanoparticles in theranostic applications

“…Additionally, the differences between the obtained relaxation time constants from different approaches can be used to quantitatively assess the impact of the used magnetic fields in every approach. Indeed, changes in relaxation time might be of value in measuring the degree of dipolar interactions and other field dependencies in the sample, which can impact application and imaging performance 34,[81][82][83] . In a recently developed MNP characterization technique called thermal noise magnetometry 84 , this idea is carried to the extreme, as it uniquely measures the magnetic noise originating from the thermally induced fluctuations in the particles' magnetization in the absence of any externally applied field.…”