Agglomeration Dynamics of Magnetite Nanoparticles at Low Magnetic Field Gradient

Abstract

Agglomeration of magnetite nanoparticles in the aqueous solution is studied at the low magnetic field gradients of 23-34 T/m by monitoring the temporal change of magnetic weight. A conventional electronic balance is used to measure the magnetic weight that is the magnetic force on the magnetic sample by the magnetic field gradient. The magnetic weight grows slowly following the stretched exponential after the instantaneous jump by the Neel and Brown relaxation. Magnetization of the magnetite nanoparticles is estimated from the magnetic weight and compared with the Langevin function. The magnetization is close to the saturation in the studied magnetic field range and the saturation magnetization of the agglomerate of nanoparticles is about 60% of that of the bulk magnetite. Kinetic parameters of the stretched exponential show little the magnetic field dependence in the investigated range. Complex energy landscape is involved in the agglomeration as the stretched exponential dynamics indicates. The half-life of the response function for the magnetic weight change suggests that the pathways of low energy barriers are activated by magnetic field at the early stage of agglomeration.

Thermoresponsive nanocomposites incorporating microplasma synthesized magnetic nanoparticles—Synthesis and potential applications

“…The level of Ms seen in our study is similar to a previous study in which Fe 3 O 4 NPs were synthesized using pulsed plasma in liquid containing a cationic surfactant . The magnetic properties of MNPs can be affected by many parameters, such as crystallinity, size, shape, and crystal defect density as well as the degree of agglomeration of the material . The presence of MBAm during the synthesis process may have influenced the Ms value of the magnetic hydrogel sample, however, the specific nature of the interaction between MBAm and the MNPs during the APM process requires more detailed investigation in the future.…”

Joining host/guest with contrary affinity at the nanoscale by chemical bonds or non-covalent interactions with organic media under diffusion: control of embedded versus exposed magnetite dispersions.

“…Last detail emphasizes preservation of identical distributions afterwards calcination step. Described pattern deviation accuses as judicious a size-selective magnetic attraction modulated by viscosity, 52 in a media able of storing and, conducting electromagnetic elds, allowing attractive diffusion, collapse and ultimate agglomeration of hydrophobic guest, 53 via self-inducing aggregation 54 or, perceptible chaining organization separated by distances compatible with metallic species fenced by original ligands 55 and also, without them in smaller guest (Figures 2C-black, SI5 A-C). Data supports signi cative EM transmissions in high e media while, in low e continuum, conduction must be heightened under con nement, being not assisted by dipoles present in host surface.…”

Complex Thermal Fluctuation of Agglomerated Magnetic Nanoparticles under Magnetic Field

“…Microscopic understanding of behaviors of magnetic nanoparticles under the magnetic field is requisite for the enhancement of their applicability in those fields. In the previous works, we have reported the agglomeration dynamics of magnetic nanoparticles in the ferrofluid under the magnetic field studied by measuring temporal changes of magnetic weight. The magnetic weight is a magnetic force that magnetic samples experience under the magnetic field gradient.…”

“…The temperature is recorded every minute during the dynamics. The same magnetite nanoparticles are used in this work as in the previous reports . The magnetite nanoparticles are very stable to remain in the superparamagnetic state for several months or longer.…”

“…As the magnetic nanoparticles agglomerate and structural relaxations take place to reach the potential energy minimum, the magnetic weight approaches a maximum. 3,6 The magnetite nanoparticles are very stable to remain in the superparamagnetic state for several months or longer. A single exponential is observed for the dynamics with a single energy barrier.…”