• 한국분말재료학회지
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• 제26권6호
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• pp.463-470
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• 2019

Fe₃O₄/SiO₂/YVO₄:Eu³⁺ multifunctional nanoparticles are successfully synthesized by facile stepwise sol-gel processes. The multifunctional nanoparticles show a spherical shape with narrow size distribution (approximately 40 nm) and the phosphor shells are well crystallized. The Eu³⁺ shows strong photoluminescence (red emission at 619 nm, absorbance at 290 nm) due to an effective energy transfer from the vanadate group to Eu. Core-shell structured multifunctional nanoparticles have superparamagnetic properties at 300 K. Furthermore, the core-shell nanoparticles have a quick response time for the external magnetic field. These results suggest that the photoluminescence and magnetic properties could be easily tuned by either varying the number of coating processes or changing the phosphor elements. The nanoparticles may have potential applications for appropriate fields such as laser systems, optical amplifiers, security systems, and drug delivery materials.

• Advances in nano research
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• 제2권4호
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• pp.187-198
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• 2014

Magnetite nanoparticles (MNPs) of different sizes were synthesized by solvothermal process maintaining their stoichiometric composition and unique structural phase. Utilizing hydrated ferric (III) chloride as unique iron precursor, it was possible to synthesize sub-micrometric magnetite clusters of sizes in between 208 and 381 nm in controlled manner by controlling the concentration of sodium acetate in the reaction mixture. The sub-micrometer size nanoclusters consist of nanometric primary particles of 19 - 26.3 nm average size. The concentration of sodium acetate in reaction solution seen to control the final size of primary MNPs, and hence the size of sub-micrometric magnetite nanoclusters. All the samples revealed their superparamagnetic behavior with saturation magnetization ($M_s$) values in between 74.3 and 77.4 emu/g. $M_s$. The coercivity of the nanoclusters depends both on the size of the primary particles and impurity present in them. The mechanisms of formation and size control of the MNPs have been discussed.

• Macromolecular Research
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• 제14권2호
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• pp.209-213
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• 2006

The ring-opening polymerization of D,L-lactide initiated by tin(II) 2-ethylhexanoate $(Sn(Oct)_2)$ on the surface-initiated magnetite $(Fe_{3}O_4)$ nanoparticles was performed at $130^{\circ}C$. The effects of the polymer molar mass and concentration on the amount of surface polymer were investigated. The number average molecular weights, $M_n$, obtained by both NMR and GPC methods fit well within the accuracy of the applied methods and ranged from 1,100 to $4,040g\;mol^{-1}$. A surface functionalization density of up to 625 initiation sites per particle was obtained. The composition of various core-shell particles was determined by TGA, with results indicating magnetite $(Fe_{3}O_4)$ contents, ${\mu}m$, between 17 and 59 wt%. Under the influence of a magnetic field, the heating generated by superparamagnetic core-shell particles suspended in toluene presented guidelines for an optimization of magnetic particle systems with respect to an application for hyperthermia.

• 대한자기공명의과학회:학술대회논문집
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• 대한자기공명의과학회 2001년도 제6차 학술대회 초록집
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• pp.109-109
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• 2001

Purpose： To assess the feasibility of sequential administration of ferumoxides and mangafodi trisodium in the same imaging protocols. Method： Thirty patients underwent double-contrast enhanced MR imaging of liver usi ferumoxides (Fe-MRI) and mangafodipir trisodium (Mn-MRI) on 1.5T GE Horizon system. In twenty patients, Mn-MRI was immediately followed by Fe-MRI. In ten patients, Fe-MR was performed first, then Mn-MRI was performed immediately, In all cases, precontras T1-weighted in-phase and opposed-phase spoiled gradient echo (GRE) images an T2-weighted fast spin-echo images (TR 4000ms, TE 102ms, ETL 8-12) were obtained Fe-MRI was performed with FSE and steady state GRE (TE 10 msec, flip angle 30 sequences. Mn-MRI was performed with in-phase and opposed-phase spoiled GR sequences. The SNR changes after the use of each contrast agents were calculated.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2003년도 하계학술연구발표회 및 한.일 공동심포지엄
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• pp.90-91
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• 2003

Amorphous magnetic materials with competing magnetic interactions are the subject of current interest. Critical behaviour studies have been performed in order to understand the nature of the phase transition at the Curie point (T$\sub$c/) and type of magnetic ordering below the T$\sub$c/. In some cases there exists a temperature interval in which the magnetic system consists of ferromagnetic grains separated by the paramagnetic interlayers. Magnetic properties of nanoparticles embedded in amorphous matrix also are the subject of recent interest. While these materials exhibit excellent soft magnetic properties at room temperature, some of them have been found to be superparamagnetic in the temperature range above the T$\sub$c/ of the matrix. Thus the role of different magnetic phases in the intergrain magnetic coupling can possibly be taken apart in a sufficiently broad temperature range and investigated separately. In particular materials with competing magnetic exchange interactions show characteristics of enhanced magnetoresistance and softer magnetic properties when magnetic nanocrystals are dispersed in amorphous matrix. We expect careful magnetic measurements in the vicinity of T$\sub$c/ would throw some light on magnetic behaviour of above materials. We present here the FMR analysis of Fe$\sub$82/Mn$\sub$8-x/B$\sub$x/Zr$\sub$10/ alloy near the Curie point.

• Journal of the Optical Society of Korea
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• 제11권1호
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• pp.26-33
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• 2007

We demonstrate the capability of differential-phase optical coherence tomography (DP-OCT) to detect superparamagnetic iron oxide (SPIO) nanoparticles taken up by liver parenchymeal macrophages (Kupffer cells). We apply an external time-varying high-intensity focused magnetic field. Our experiments demonstrate a novel diagnostic modality to detect macrophages that have taken up SPIO nanoparticles. Magnetic force acting on the nanoparticles was varied by applying a sinusoidal current to a solenoid containing a conical iron core that substantially increased and focused the magnetic field strength ($B_{max}$ = 2 Tesla). $ApoE^{-/-}$ mice were sacrificed 2 days post intravenous injections of different SPIO doses (1.0, and 0.1 mmol Fe/kg body weight). Livers of $ApoE^{-/-}$ mice with and without injection of SPIO nanoparticles were investigated using DP-OCT, which detects tissue movement with nanometer resolution. Frequency response of iron-laden liver movement was twice the stimulus frequency. Movement was not observed in livers of control mice. Results of our experiments indicate DP-OCT is a candidate methodology to detect tissue based macrophages containing SPIO nanoparticles excited by an external focused magnetic field.

• Investigative Magnetic Resonance Imaging
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• 제16권2호
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• pp.97-102
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• 2012

고해상도 경동맥 자기공명영상(MRI)을 이용하여 경화판 특성을 파악할 수 있다. MRI는 경화판의 활동성 염증이나 경화판내 출혈을 비침습적으로 진단할 수 있는 능력이 있다. 3T MRI는 1.5T MRI에 비해 신호 대 잡음비와 대조도 대 잡음비가 높다. 동맥벽의 면적이나 표준화된 동맥벽 면적을 MRI로 측정하면 약물 치료 후 반응을 평가할 수 있다. 결론적으로 고행상도 MRI는 일과성 허혈이나 뇌졸중을 발생하기 쉬운 경화판의 진단과 치료 후 평가에 유용하다.

• 대한화학회지
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• 제27권3호
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• pp.224-232
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• 1983

$Fe_2O_3$와 $BaCO_3$ 분체를 철제 ball-mill로 각각 5, 15, 30, 80, 200시간 혼합분쇄하여 얻어진 $BaCO_3-Fe_2O_3$계에서 고체반응 및 생성 Ba-ferrite의 자기적 성질에 미치는 분쇄시간의 영향을 조사하였다. 열천칭, X-선 회절기, 주사형전자현미경 및 B-H 이력곡선기 등을 사용하여 조사한 결과 일정시간 이상 분쇄시켰을 때 입자의 응집현상과 함께 초상자성을 띄는 미립자가 생기게 되어 Ba-ferrite의 생성 및 자기적 성질에 중요한 영향을 미친다는 사실을 확인했다.

• Macromolecular Research
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• 제14권6호
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• pp.646-653
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• 2006

Highly hydrophilic, uniform, superparamagnetic and nontoxic maltotrionic acid (MA)-coated magnetite nano-particles (MAM) were prepared and characterized by TEM, DLS, XRD and VSM. MA was used to improve the biocompatibility, monodispersity and non-specific intracellular uptake of nanoparticles. Folic acid (FA) was subsequently conjugated to the MAM to preferentially target KB cells (cancer cells) that have folate receptors expressed on their surfaces and to facilitate nanoparticles in their transit across the cell membrane. Finally, fluorescence isothiocyanate (FITC) was added to the nanoparticles to visualize the nanoparticle internalization into KB cells. After the cells were cultured in a media containing the MAM and MAM-folate conjugate (FAMAM), the results of fluorescence and confocal microscopy showed that both types of nanoparticles were internalized into the cells. Nevertheless, the amount of FAMAM uptake was higher than that of MAM. This result indicated that nanoparticles modified with MA and FA could be used to facilitate the nanoparticle uptake to specific KB cells (cancer cells) for molecular imaging.

• 한국분말재료학회지
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• 제14권2호
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• pp.97-100
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• 2007

The magnetic alloys of Cu-Fe ($Cu_{50}Fe_{50},\;Cu_{80}Fe_{20}\;and\;Cu_{90}Fe_{10}$) were prepared by a mechanical alloying method and their structural and magnetic behaviors were examined by X-ray diffraction and Mossbauer spectra. The magnetization curves did not distinctly show the saturation at 70 kOe for the concentrated alloys of $Cu_{80}Fe_{20}\;and\;Cu_{90}Fe_{10}$. The Mossbauer spectrum of $Cu_{80}Fe_{20}$ at room temperature shows one Lorentzian line of the paramagnetic phase, whereas the Mossbauer spectrum of $Cu_{90}Fe_{10}$ consists of sextet Lorentzian line at room temperature and a centered doublet line. The Mossbauer spectra of $Cu_{90}Fe_{10}$ measured in the temperature ranges from 13 to 295 K, implies that $Cu_{90}Fe_{10}$ to consists of two magnetic phases. One superimposed sextet corresponds to the ferromagnetic iron in Cu and the other one indicates the superparamagnetic iron rich phase.