• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.6
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• pp.51-56
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• 2011

The surface of magnetic iron oxide nanoparticles (${\gamma}-Fe_2O_3$) is functionalized ($-NH_2$, -COOH) with bifunctional organic molecules and evaluated using FT-IR (Fourier transform infrared spectroscopy). We immobilize 21-base pair probe DNA and hybridize fluorescence-labeled (Cy5) target DNA onto the functionalized iron oxide nanoparticles. The fluorescence images obtained from a confocal microscopy show that the functionalized iron oxide nanoparticles should detect the hybridization of complementary and noncomplementary DNA.

• Clean Technology
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• v.15 no.3
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• pp.194-201
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• 2009

Reductive reactivity of zero-valent iron nanoparticles was investigated for removal of nitrate-nitrogen which is considered one of the major water pollutants. To elucidate the difference in reactivity between preparation methods, iron nanoparticles were synthesized respectively from microemulsion and aqueous solution of ferric ions. Iron nanoparticles prepared from microemulsion were deposited on aluminum by electrophoretic method, and their reaction kinetics was compared to that of the same nanoparticles suspended in aqueous batch reaction. With an approximation of pseudo-first-order reaction, rate constants for suspended nanoparticles prepared from microemulsion and dilute aqueous solution were $3.49{\times}10^{-2}min^{-1}$ and $1.40{\times}10^{-2}min^{-1}$, respectively. Iron nanoparticles supported on aluminum showed ca. 30% less reaction rate in comparison with the identical nanoparticles in suspended state. However, supported nanoparticles showed the superior effectiveness in terms of nitrate-nitrogen removal per zero-valent iron input especially when excess amounts of nitrates were present. Iron nanoparticles deposited on aluminum maintained reductive reactivity for more than 3 hours, and produced nitrogen gas as a final reduction product of nitrate-nitrogen.

• Journal of the Korean Magnetics Society
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• v.24 no.1
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• pp.18-21
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• 2014

The microwave absorption ($P_{tot}$), which is the double integration value of ferromagnetic resonance signal, propositional to the saturation magnetization, and the increase of the $P_{tot}$ measured during the thermal reaction time expect the growth process of the nanoparticles. Therefore, in this work, we measured the $P_{tot}$ in order to obtain the growth time of iron oxide nanoparticles after thermal decomposition of $Fe(acac)_3$ precursor at aging temperature $T_a=273$, 300 and $324^{\circ}C$, respectively. The best condition for monodisperse nanoparticles was obtained at $T_a=300^{\circ}C$, which condition showed the most rapid increase of $P_{tot}$ with thermal reaction time. Finally, the rapid growth rate was necessary condition for the synthesis of iron-oxide monodisperse nanoparticles.

• Journal of Soil and Groundwater Environment
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• v.14 no.6
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• pp.101-107
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• 2009

Carboxymethyl cellulose (CMC) as stabilizer is expected to facilitate in-situ delivery of zero-valent iron (ZVI) nanoparticles in a contaminated aquifer because it increases dispersity of ZVI nanoparticles. This work investigated the transport of CMC-stabilized ZVI nanoparticles (CMC-Fe) using column breakthrough experiments. The ZVI nanoparticles (100 mg/L Fe) were transportable through sand porous media. In contrast, non-stabilized ZVI nanoparticles rapidly agglomerate in solution and are stopped in sand porous media. At pH 7 of solution approximately 80% CMC-Fe were eluted. When the pH of solution is below 5, 100% CMC-Fe were eluted. These results suggest that the mobility of CMCFe was increased as pH decreases. In the mobility test under different ionic strengths using $Na^+$ and $Ca^{2+}$ ions, there was no signigficant difference in the mobility of CMC-Fe. Also, in the experiments of effect of clay and natural organic mater (NOM) on the mobility of ZVI, there was no significant difference in the mobility of CMC-Fe not only between 1 and 5% clay, but 100 and 1000 mg/L NOM. The results from this work suggests that the CMC-Fe nanoparticles could be easily delivered into the subsurface over a broad range of ionic strength, clay and NOM.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.2
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• pp.144-150
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• 2013

Hybrid ceramic membrane (HCM) processes that combined ozonation with a ceramic membrane (CM) or a reactive ceramic membrane (RM), an iron oxide nanoparticles (IONs) incorporated-CM were investigated for membrane fouling control. Alumina disc type microfiltration and ultrafiltration membranes doped with IONs by sintering method were tested under varying mass fraction of IONs. Scanning electron microscope (SEM) images showed that IONs were well-doped on the CM surface and doped IONs were approximately 50 nm in size. Change in the pure water permeability of RM was negligible compared to that of CM. These results indicate that IONs incorporation onto CM had little effect on CM performance in terms of the flux. Natural organic matter (NOM) fouling and fouling recovery patterns during HCM processes confirmed that the RM-ozonation process enhanced the destruction of NOM and reduced the extent of fouling more than the CM-ozonation process by hydroxyl radical formation in the presence of IONs on RM. In addition, analyses of NOM in the feed water and the permeate showed that the efficiency of membrane fouling control results from the NOM degradation during HCM processes; leading to removal and transformation of relatively high contents of aromatic, high molecular weight and hydrophobic NOM fractions.

• Journal of the Korean Magnetics Society
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• v.22 no.5
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• pp.167-172
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• 2012

In order to analyze the formation mechanism of iron oxide nanoparticles, we measured the heat flow of $Fe(OL)_3$ precursor with temperature, and TEM images and AC susceptibility of aliquots samples sequentially taken from the reaction solution, respectively. The thermal decomposition of two OL-chain from $Fe(OL)_3$ produced the Fe-OL monomer, which were contributed to the formation of iron oxide nanoparticles. In the initial stage of nanoparticles formation, the small iron oxide nanoparticles had ${\gamma}-Fe_2O_3$ structure. However, as the iron oxide nanoparticles were rapidly growth, the iron oxide nanoparticles showed ${\gamma}-Fe_2O_3$-FeO core-shell structure which the FeO layer was formed on the surface of ${\gamma}-Fe_2O_3$ nanoparticles by insufficient oxygen supply from the reaction solution. These nanoparticles were transformed to $Fe_3O_4$ structure by oxidation during long aging time at high temperature. Finally, the $Fe_3O_4$ nanoparticles with high saturation magnetization and stable in the air could be easily synthesized by the thermal decomposition method.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1998.11a
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• pp.52-56
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• 1998

최근 들어 국외에서는 오염된 지하수의 정화기술로써 0가 금속을 이용한 방법이 높은 잠재력을 가진 신기술로 알려져 있다. 본 연구에서는 0가 금속중 나노크기(1-100nm)를 가진 0가 철입자를 이용하여 수중의 NO$_3$￣를 탈질처리하는 실험을 행하였다. 본 실험에서 제조한 나노크기 0가 철입자는 상온상압의 환원적 조건에서 50, 100, 200, 400mg/$\ell$의 NO$_3$￣와 반응하여 반응시간 30분안에 95%이상 제거되는 높은 반응성을 보여주었다. 기존의 상업용 철입자(10-100$\mu\textrm{m}$)를 이용한 NO$_3$￣의 제거결과에서 보여주는 다량의 철사용, 낮은 적용 오염농도, 그리고 낮은 반응속도등의 문제점에 비하여 나노크기 철 입자는 높은 오염농도범위에서도 적은 철 주입량과 짧은 반응시간 내에 매우 높은 제거효율(10-100배)을 나타내었다. 이러한 결과로 수중의 NO$_3$￣의 고속 탈질반응속도에 영향을 주는 중요한 변수는 반응에 참여하는 철 입자의 비표면적임을 알 수 있었다. 본 연구에서 얻은 batch실험 결과를 바탕으로 NO$_3$￣로 오염된 지하수의 정화를 위한 현장 적용을 목표로 연속처리 공정의 설계를 위한 토대를 마련하고자 하였다.

• Polymer(Korea)
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• v.29 no.3
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• pp.266-270
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• 2005

Iron oxide nanoparticles were prepared by the thermal decomposition of iron pentacarbonyl (Fe(CO)$_5$) Poly(vinylpyrrolidone) (PVP) was used as surface-modifying agent to control the size of the iron oxide nanoparticles. The crystalline structure of PVP coated iron oxide nanoparticles was determined by XRD. The size of PVP coated iron oxide nanoparticles was determined by TEM and ELS. The particle sizes of PVP coated iron oxide nanoparticles were controlled by adjusting the molar ratio of PVP/Fe (CO)$_5$, solvent and molecular weight of PVP Particle sizes increased with increasing PVP content. Spherical $50\~100$ nm sized iron oxide nanoclusters were produced when dimethylformamide was used as a solvent. And well-defined 10 nm iron oxide nanoparticles were produced in Carbitol. The prepared PVP coated iron oxide nanoparticles exhibited a well-dispersed property in water. The results obtained in this study confirmed the feasibility of the PVP-coated iron oxide nanoparticles as a biomaterial for MRI contrast agent.

• Clean Technology
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• v.28 no.2
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• pp.110-116
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• 2022

In this study, iron oxide (FeO_x) nanoparticles were synthesized using iron (Fe) by-products recovered from NdFeB permanent magnet scraps, and the effect of heat-treatment temperature on the physical properties of the FeO_x nanoparticles was investigated. In order to prepare the FeO_x nanoparticles, 2.0 M ammonia (NH₄OH) solution was added to an iron by-product solution diluted to c.a. 10 wt% in D.I. water, which led to the precipitation of the iron oxide precursor. Then, the FeO_x nanoparticles were synthesized by heat-treatment at 300 ℃, 400 ℃, 500 ℃ and 600 ℃. After that, the physical properties of the FeO_x nanoparticles were investigated in order to understand the effect of the heat-treatment temperature. The results of the X-ray diffraction (XRD) analysis showed that the diffraction peak in accordance with the <104> direction increased as the heat-treatment increased, and a diffraction peak indicating the α-Fe₂O₃ crystal structure was detected at heat-treatment temperatures above 500 ℃. The BET specific surface area analysis revealed that the specific surface area decreased as the heat-treatment temperature increased to above 400 ℃. Observation with a high resolution transmission electron microscope (HRTEM) showed that rod-shaped nanoparticles were formed, and the size of the nanoparticles showed a tendency to increase as the heat-treatment temperature increased.

• Journal of the Korean Magnetics Society
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• v.24 no.1
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• pp.11-17
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• 2014

We measured the ferromagnetic resonance (FMR) signal using the monodisperse iron oxide nanoparticles with size D=4.67 nm, 5.64 nm and 6.34 nm synthesized by using the thermal decomposition method, respectively. The measured ferromagnetic resonance signals were compared with the calculated ones for superparamagnetic nanoparticles with lognormal volume distribution. The FMR linewidth broadening was propositional to tanh($V^2$), where V was volume of nanoparticles. The narrow linewidth of small size nanoparticles was due to the surface spins, while the broad linewidth of large size nanoparticles was due to the bulk spins affected by the crystalline structure of iron oxide nanoparticles. The superposition of surface and bulk effect was confirmed at D=5.64 nm nanoparticles, which was near the critical size for linewidth transition from surface effect to bulk effect.