• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2279-2282
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• 2007

Highly crystalline, uniform Fe nanoparticles were successfully synthesized and encapsulated in zirconia shell using sol-gel process. Two different approaches have been employed for the coating of Fe nanoparticle with zirconia. The thickness of zirconia shell can be readily controlled by altering molar ratio of Fe nanoparticle core to zirconia precursor in the first case where as reaction time was found to be most effective parameter to controlled the shell thickness in the second method. The structure and magnetic properties of the ZrO2-coated Fe nanoparticles were studied. TEM and HRTEM images show a typical core/shell structure in which spherical α-iron crystal sized of ~25 nm is surrounded by amorphous ZrO2 coating layer. TGA study showed an evidence of weight loss of less than 2% over the temperature range of 50-500 °C. The nanoparticles are basically in ferromagnetic state and their magnetic properties depend strongly on annealing temperature. The thermal treatment carried out in as-prepared sample resulted in reduction of coercivity and an increase in saturation magnetization. X-ray diffraction experiments on the samples after annealing at 400-600 °C indicate that the size of the Fe@ZrO2 particles is increased slightly with increasing annealing temperature, indicating the ZrO2 coating layer is effective to interrupt growing of iron particle according to heat treatment.

• Bulletin of the Korean Chemical Society
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• v.27 no.2
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• pp.237-242
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• 2006

$Fe_3O_4$ and $CoFe_2O_4$ magnetic nanoparticles have been synthesized successfully in aqueous solution and coated with oleic acid. The solid and organic solution of the synthesized nanoparticles was obtained. Self-assembled monolayer films were formed using organic solution of these nanoparticles. The crystal sizes determined by Debye-Scherre equation with XRD data were found close to the particle sizes calculated from TEM images, and this indicates that the synthesized particles are nanocrystalline. Especially, EDS, ED, FT-IR, TGA/DTA and DSC were used to characterize the nanoparticles and the oleic acid adsorption, and it was found that oleic acid molecule on the $Fe_3O_4$ nanoparticle is a bilayer adsorption, while that on $CoFe_2O_4$ nanoparticle is single layer adsorption. The superparamagnetic behavior of the nanoparticles was documented by the hysteresis loop measured at 300 K.

• Journal of Magnetics
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• v.11 no.4
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• pp.189-194
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• 2006

The recent development of bio-conjugated magnetic nanoparticles offers many opportunities for applications in the field of biomedicine. In particular, the use of magnetic nanoparticles for biosensing has generated widespread research efforts following the progress of various magnetic field sensors. Here we demonstrate substrate-free biosensing approaches based on the Brownian rotation of ferromagnetic nanoparticles suspended in liquids. The signal transduction is through the measurement of the magnetic ac susceptibility as a function of frequency, whose peak position changes due to the modification of the hydrodynamic radius of bio-conjugated magnetic nanoparticles upon binding to target bio-molecules. The advantage of this approach includes its relative simplicity and integrity compared to methods that use substrate-based stray-field detectors.

• Journal of the Korean Society of Combustion
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• v.16 no.2
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• pp.33-39
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• 2011

We demonstrated heat generation efficiency of the magnetic hyperthermia system to find optimal condition using gelatin tissue phantom. Magnetic hyperthermia induction can be used to make heat generation with different concentration of $Fe_3O_4$ iron oxide inside tissue phantom and magnetically labeled cells by applying AC magntic field at a frequency of 145 kHz. It was observed that the maximum temperature achieved in the magnetic gelatin tissue phantom increased with the concentration of $Fe_3O_4$ iron oxide and alternating magnetic field intensity. Results were discussed with respect to further optimization of therapeutic technique for biomedical application with modified functional nanoparticles.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.4 no.1
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• pp.36-42
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• 2018

Molecular imaging refers to detect the biochemical process in living organisms at the cellular and molecular levels and to quantify them. Due to several advantages of nanomaterials, various molecular images using nanomaterials are being tried. Attempts have been made to combine nanoparticles, known as micro- or nanosized nanomaterials, with radioactive isotopes for molecular imaging probe. The radiolabeled nanoparticles will expend the molecular imaging due to nanoparticle's size-dependent nature. In particular, iron oxide nanoparticles can be used for magnetic resonance imaging, can be adjusted in size, easily functionalized, and biocompatible, making it a very good platform for molecular imaging. In addition, iron oxide nanoparticles may be the best example for a new approach to molecular imaging techniques. In this paper, we introduce various methods for preparation of iron oxide nanoparticle combined with radioisotope starting from various synthesis methods of iron oxide nanoparticles to utilize iron oxide nanoparticles as a platform for molecular imaging through radioactive labeling.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.431.2-431.2
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• 2014

The dielectric breakdown voltage (DBV) is a measure of an insulating fluids ability to withstand a high electric field stress without breaking down. Conventionally, the presence of water or particulate matter in a dielectric fluid comprises the liquid's breakdown strength. However, the addition of magnetic nanoparticles (MNPs) in the base oil can increase the dielectric breakdown voltage of the fluid reversely, if the condition of the added particles in the fluid is in balance with that of keeping down the initiation and propagation of electrical streamers. In this study, we developed a mathematical model by a set of coupled, nonlinear equations using the COMSOL multiphysics finite element simulation suite and calculated the dielectrophoretic activity of magnetic nanoparticles suspended in the presence of electric field, which is the behavior responsible for enhancing the dielectric characteristics of transformer oil, in order to examine how the activity differ in a transformer oil-based magnetic fluid.

• Proceedings of the Korea Environmental Mutagen Society Conference
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• 2002.11a
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• pp.159-159
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• 2002

• Journal of the Korean Chemical Society
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• v.53 no.2
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• pp.207-212
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• 2009

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.12.2-12.2
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• 2009

The work describes anoptimized process to highly efficient and convenient preparation in highthroughput magnetic human DNA separation with chemically functionalizedsilica-coated magnetic nanoparticles. The effect of nanoparticle's size and the surface's hydrophilicity change were studied for magnetic DNA separation process, inwhich the optimum efficiency was explored via the function of the amino-groupnumbers, particle size, the amount of the nanoparticles used, and theconcentration of NaCl salt. The DNA adsorption yields were high in terms of theamount of triamino-functionalized nanoparticles used, and the average particlesize was 25 nm. The adsorption efficiency of aminofunctionalized nanoparticleswas the 4-5 times (80-100%) higher compared to silica-coated nanoparticles only(10-20%). DNA desorption efficiency showed an optimum level of over 0.7 M ofthe NaCl concentration. To elucidate the agglomeration of nanoparticles afterelectrostatic interaction, the Guinier plots were calculated from small angleX-ray diffractions in a comparison of the results of electron diffraction TEM,and confocal laser scanning microscopy. Additionally, the direct separation ofhuman genomic DNA was achieved from human saliva and whole blood with highefficiency.

• Journal of Magnetics
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• v.11 no.4
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• pp.160-163
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• 2006

We have prepared crystalline Ag nanoparticles with an average size of 4 nm in diameter by using an inductively coupled plasma reactor equipped with the liquid nitrogen cooling system. Our magnetic data show that the nano-sized effect of Ag nanoparticles on the magnetic properties is ferromagnetic, instead of a diamagnetic component of the Ag bulk and a superparamagnetic component of magnetic nanoparticles. We have also studied the magnetic properties of Ag-Cu nanocomposites with an opposite concentration profile between surface and core. These comparisons indicate that the ferromagnetic component strongly depends on the surface of Ag nanoparticles, while the paramagnetic component is strongly affected by the outer oxide layer, with the background of a diamagnetic component from the core of Ag.