Abstract
The magnetic properties of magnetite nanoparticles (Fe3O4 NPs) strongly depend on their chemical and physical parameters, which can be regulated by a controlled synthesis process. To improve the quality of the obtained nanoparticles, their surface is often modified with organic compounds (from the group of surfactants, sugars, proteins, or organic acid). In this study, we synthesized magnetite nanoparticles with a surface modified with the organic compound DMSA. Then, the nanocrystallites were characterized in terms of structure and morphology. To investigate the role of DMSA and to understand the adsorption mechanism, FTIR measurements were carried out. Using Mössbauer spectroscopy, we investigated temperature-induced changes in the magnetic properties of prepared samples. The spectra were recorded in a wide temperature range (from 4 K to 390 K) for two types of samples: powders and ferrofluids with various concentrations. In the case of powder samples, the superparamagnetic doublet appeared at room temperature. For magnetic suspensions, the spectra were more complicated. They consisted of superposition of asymmetrically broadened sextets and doublets, which was caused by the occurrence of long-range dipole-dipole interactions. These interactions affected the magnetic properties of the material and increased the blocking temperature. Additionally, the magnetic hysteresis and zero field cooling-field cooling (ZFC/FC) curves were measured with the use of a vibrating sample magnetometer.
Highlights
Due to their chemical and physical properties, iron oxide nanoparticles are widely used in many fields of science
It is worth underlining that Fe3O4 NPs exhibit superparamagnetism at room temperature, which means that they can be manipulated by an influence of an alternating external magnetic field
It is worth emphasizing that the usefulness and effectiveness of magnetic nanoparticles (MNPs) strongly depend on their physical and chemical parameters, which can be regulated in the synthesis process [6]
Summary
Due to their chemical and physical properties, iron oxide nanoparticles (mainly magnetite Fe3O4 and maghemite γ-Fe2O3) are widely used in many fields of science. Their low toxicity, interesting magnetic properties, and biocompatibility make them desirable for advanced medical applications such as drug and heat delivery (targeted therapy and magnetic fluid hyperthermia), bioimaging (magnetic resonance imagining contrast), or tissue engineering [1, 2]. Due to the small size, the magnetic energy of anisotropy is smaller or comparable with the thermal energy of crystal lattice vibrations This results in overcoming the energy barrier, which in turn leads to spontaneous fluctuations of the nanoparticle magnetisation vector.
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