• Applied Chemistry for Engineering
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• v.17 no.4
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• pp.403-408
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• 2006

To enhance the dental properties of polymeric dental restorative composite activated by visible-light, the surface of hydrophilic silica nanoparticle was hydrophobically treated using $\gamma$-methacryloxypropyltrimethoxysilane ($\gamma$-MPS) coupling agent. Structural properties and dispersity of silica in the composite was compared with the hydrophobicity of silica. Polymerization characteristic of the composite was also evaluated. Degree of hydrophobicity of silica nanoparticle was considerably improved with an increase of $\gamma$-MPS upto 40 wt% and converged asymptotically. Additionally, with an increase of the hydrophobicity of silica nanoparticle, the dispersity of silica was improved and the residual monomer in the composite was not detected from nuclear magnetic resonance experiment which indicated superior polymerization behavior.

• 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.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.577-577
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• 2012

자성나노유체(ferrofluid)는 계면활성제로 코팅된 직경 10 nm인 자성나노입자(magnetic nanoparticle)가 바탕액체(물 또는 오일 등)에 분산하고 있는 액체이다. 최근 연구에 의하면 자성나노 유체가 변압기 절연유로 사용될 경우 열전달 및 절연 특성이 향상된다고 보고되고 있다. 또한 자성나노유체에 포함된 자성나노입자는 영구자석 및 전자석 등에 의한 외부 자기장뿐만 아니라, 두 전극 사이에 인가된 전기장에 의한 유도자기장에 영향을 받는다고 한다. 본 연구에서는 두 전극 사이 전압을 1 kV로 인가한 경우에서 광학현미경을 이용한 자성나노입자의 마이크로 채널(microchannel) 내부 이동특성 관측 및 Maxwell 방정식을 이용한 전자기장 수치해석을 수행하였다. 실험 및 해석 결과를 통하여 자성나노유체에 포함된 자성나노입자가 인가된 전기장에 의하여 발생되는 이동특성을 분석하고, 선행연구에서 보고된 절연특성 변화에 관한 상관관계에 대해 고찰하였다. 광학현미경 관측 결과로부터 전기장이 인가되지 않은 경우에 균일하게 분산되어 있는 자성나노입자는 전기장 인가에 따라 발생되는 유도자기장에 의하여 입자 간의 뭉침(agglomeration) 현상과 전극 주위로 이동하려는 성질을 확인하였다. 또한 수치해석 결과로부터 자성나노입자의 존재로 인하여 전극 사이의 전기장 강도와 자속밀도가 증가함을 확인하였으며, 자성나노입자의 이동을 유발하는 유도자기장이 전극 주위에서 큰 것을 파악할 수 있었다. 이와 같은 결과는 자성나노입자가 변압기 절연유에 첨가된 경우우 절연파괴전압이 변화되는 이유를 설명할 수 있는 근거가 된다.

• Journal of Radiation Industry
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• v.9 no.1
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• pp.15-20
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• 2015

Carbon fiber has received much attention owing to its properties, including a large surface-to-volume ratio, chemical and thermal stability, high thermal and electrical conductivity, and high mechanical strengths. In particular, magnetic nanopowder dispersed carbon fiber has been attractive in technological applications such as the electrochemical capacitor and electromagnetic wave shielding. In this study, the nickel-oxide-nanoparticle dispersed polyacrylonitrile (PAN) fibers were prepared through an electrospinning method. Electron beam irradiation was carried out with a 2.5 MeV beam energy to stabilize the materials. The samples were then heat-treated for stabilization and carbonization. The nanofiber surface was analyzed using a field emission scanning electron microscope (FE-SEM). The crystal structures of the carbon matrix and nickel nanopowders were analysed using X-ray diffraction (XRD). In addition, the magnetic and electrical properties were analyzed using a vibrating sample magnetometer (VSM) and 4 point probe. As the irradiation dose increases, the density of the carbon fiber was increased. In addition, the electrical properties of the carbon fiber improved through electron beam irradiation. This is because the amorphous region of the carbon fiber decreases. This electron beam effect of PAN fibers containing nickel nanoparticles confirmed their potential as a high performance carbon material for various applications.

• Journal of Magnetics
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• v.18 no.3
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• pp.230-234
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• 2013

The $Ni_{0.5}Zn_{0.5}Fe_2O_4$ nanoparticles about 30 nm were prepared using sol-gel method with metal nitrates dissolved in 2-methoxyathanol. The concentrations of the metal nitrates are adjusted from 0.1 to 0.75 M in order to study the influence on the structural and magnetic properties. The structure and morphology characterization revealed that the crystallinity was improved and the nanoparticle size was increased with the nutrition solution concentrations up to 0.5 M. Degraded crystallinity together with decreased nanoparticle size were observed for concentration of 0.75 M. The saturation magnetization at room temperature reached maximum at 0.5 M, which can be explained by considering the crystallinity and size effect.

• Journal of Magnetics
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• v.10 no.1
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• pp.5-9
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• 2005

Nanoparticles $Ni_{0.9}Zn_{0.1}Fe_2O_4$ is fabricated by a sol-gel method. The magnetic and structural properties of powders were investigated with XRD, SEM, Mossbauer spectroscopy, and VSM. $Ni_{0.9}Zn_{0.1}Fe_2O_4$ powders annealed at $300{^{\circ}C}$ have a spinel structure and behaved superparamagnetically. The estimated size of $Ni_{0.9}Zn_{0.1}Fe_2O_4$ nanoparticle is about 10 nm. The hyperfine fields at 13 K for the A and B patterns are found to be 533 and 507 kOe, respectively. The ZFC curves are rounded at the blocking temperature ($T_B$)and show a paramagnetic-like behavior above $T_B$. $T_B$ of $Ni_{0.9}Zn_{0.1}Fe_2O_4$ nanoparticle is about 250 K. Nanoparticles $Ni_{0.9}Zn_{0.1}Fe_2O_4$ annealed at 400 and $500{^{\circ}C}$ have a typical spinel structure and is ferrimagnetic in nature. The isomer shifts indicate that the iron ions were ferric at the tetrahedral (A) and the octahedral (B). The saturation magnetization of nanoparticles $Ni_{0.9}Zn_{0.1}Fe_2O_4$ annealed at 400 and $500{^{\circ}C}$ are 40 and 43 emu/g, respectively. The magnetic anisotropy constant of $Ni_{0.9}Zn_{0.1}Fe_2O_4$ annealed at $300{^{\circ}C}$ were calculated to be 1.6 ${\times}$ $10^6$ ergs/$cm^3$.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.9
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• pp.4237-4240
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• 2016

Drugs processed using nanobiotechnology may be more biocompatible, with sustainable and stabilised release or action. L-asparaginase produced from fungi has many advantages for treatment of lymphocytic leukemia with lesser side effect. In the present work, maghemite nanobiocomposites of fungal asparaginase were produced using glutaraldehyde-pretreated colloidal magnetic nanoparticles. Formation of nanobiocomposites was observed using laser light scattering and confirmed by UV-visible spectrophotometry with the absorption peak at 497 nm. The specific asparaginase activity was increased from 320 U/mg with crude asparaginase to 481.5 U/mg. FTIR analysis confirmed that primary amines are the functional groups involved in binding of asparaginase on magnetic nanoparticles. The average size of the produced nanobiocomposite was found in the range of 30 nm to 40 nm using histogram analysis. The magnetic nanobiocomposite of asparaginase synthesised using glutaraldehyde showed 90.75% cytotoxicity against human colon adenocarcinoma cell lines. Hence it can be used as an active anticancer drug with an augmented level of bioavailability.

• Smart Structures and Systems
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• v.12 no.1
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• pp.1-22
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• 2013

Magnetic nanoparticle based bioseparation in microfluidics is a multiphysics phenomenon that involves interplay of various parameters. The ability to understand the dynamics of these parameters is a prerequisite for designing and developing more efficient magnetic cell/bio-particle separation systems. Therefore, in this work proof-of-concept experiments are combined with advanced numerical simulation to design and optimize the capturing process of magnetic nanoparticles responsible for efficient microfluidic bioseparation. A low cost generic microfluidic platform was developed using a novel micromolding method that can be done without a clean room techniques and at much lower cost and time. Parametric analysis using both experiments and theoretical predictions were performed. It was found that flow rate and magnetic field strength greatly influence the transport of magnetic nanoparticles in the microchannel and control the capturing efficiency. The results from mathematical model agree very well with experiments. The model further demonstrated that a 12% increase in capturing efficiency can be achieved by introducing of iron-grooved bar in the microfluidic setup that resulted in increase in magnetic field gradient. The numerical simulations were helpful in testing and optimizing key design parameters. Overall, this work demonstrated that a simple low cost experimental proof-of-concept setup can be synchronized with advanced numerical simulation not only to enhance the functional performance of magneto-fluidic capturing systems but also to efficiently design and develop microfluidic bioseparation systems for biomedical applications.

• Membrane and Water Treatment
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• v.4 no.1
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• pp.53-67
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• 2013

In this study, ageing characteristics of an industrial hollow-fiber membrane module were investigated after 50 months of drinking water production. For this purpose, the industrial module was opened to make 18 smaller modules with hollow-fibers taken from different parts of the industrial module. These modules were probed by the use of a magnetic nanoparticle (NP) challenge test based on magnetic susceptibility (K) measurement of permeate. No magnetic susceptibility was detected in permeate when the challenge test was performed on an intact membrane module, indicating the complete retention of nanoparticles by the membrane. The compromised membrane module can be successfully detected by means of magnetic susceptibility measurement in permeate. So, this study clearly demonstrates that ageing of ultrafiltration membranes can be monitored by measuring the magnetic susceptibility of permeate from an ultrafiltration membrane module. These results showed that the hollow fibers in the center zones of the bundle would age faster than those in the outer zones around the bundle. This result is in agreement with numerical simulation (Daurelle et al. 2011).

• Journal of Magnetics
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• v.21 no.1
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• pp.20-24
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• 2016

Magnetic properties of bio-magnetic molecule ferritin have been investigated. Two ferritin samples were synthesized under different magnetic fields, 0 and 9.4 T, respectively. This work is focused on the influence of magnetic field on biomineralization process. While magnetization vs. temperature (M-T) data of both samples measured at 1000 Oe are almost identical except for low temperature region (T < 6 K), magnetization vs. field (M-H) data show noticeable difference. From an analysis of M-H data by using a modified Langevin function, we could extract the saturation magnetization $m_0$(T), the effective magnetic moment ${\mu}_{eff}$(T) and the linear susceptibility x(T). The difference between the samples is most prominent in the x(T), whereby the x(T) of the sample prepared at 9.4 T is 1.7 times bigger than that of the other. In addition, from hysteresis and relaxation measurements, we found the sample prepared at 9.4 T showed strikingly smaller coercivity and slower relaxation.