• Journal of the Korean Magnetics Society
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• v.14 no.6
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• pp.236-239
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• 2004

We studied the specular spin valve (SSV) having the spin filter layer (SFL) in contact with the ultrathin free layer composed of Ta3/NiFe2/IrMn7/CoFel/(NOLl)/CoFe2/Cu1.8/CoFe( $t_{F}$)/Cu( $t_{SF}$ )/(NOL2)/Ta3.5 (in nm) by the magnetron sputtering system. For this antiferromagnetic I $r_{22}$M $n_{78}$-pinned spin filter specular spin valve (SFSSV) films, an optimal magnetoresistance (MR) ratio of 11.9% was obtained when both the free layer thickness ( $t_{F}$) and the SFL thickness ( $t_{SF}$ ) were 1.5 nm, and the MR ratio higher than 11% was maintained even when the $t_{F}$ was reduced to 1.0 nm. It was due to increase of specular electron by the nano-oxide layer (NOL) and of current shunting through the SFL. Moreover, the interlayer coupling field ( $H_{int}$) between free layer and pinned layer could be explained by considering the RKKY and magnetostatic coupling. The coercivity of the free layer ( $H_{cf}$ ) was significantly reduced as compared to the traditional spin valve (TSV), and was remained as low as 4 Oe when the $t_{F}$ varied from 1 nm to 4 urn. It was found that the SFL made it possible to reduce the free layer thickness and enhance the MR ratio without degrading the soft magnetic property of the free layer.

• Bulletin of the Korean Chemical Society
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• v.28 no.7
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• pp.1091-1096
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• 2007

Water dispersible ZnS:Mn nanocrystals were synthesized by capping the surface of the nanocrystals with four kinds of aminoacids ligands: arginine, cystein, histidine, and methionine. The aminoacids capped ZnS:Mn nanocrystal powders were characterized by XRD, HR-TEM, EDXS, and FT-IR spectroscopy. The optical properties of the aminoacids capped ZnS:Mn colloidal nanocrystals were also measured by UV/Vis and solution photoluminescence (PL) spectroscopies in aqueous solvents. The solution PL spectra showed broad emission peaks around 575 nm (orange light emissions) with PL efficiencies in the range of 4.4 to 7.1%. The measured particle sizes for the aminoacid capped ZnS:Mn nanocrystals by HR-TEM images were in the range of 5.3 to 11.7 nm.

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1741-1747
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• 2012

Water-dispersible ZnS:Mn nanocrystals were synthesized by capping the surface of the nanocrystals with conventional aminoacids ligands: serine and threonine. The aminoacids capped ZnS:Mn nanocrystal powders were characterized by XRD, HR-TEM, EDXS, ICP-AES and FT-IR spectroscopy. The optical properties were also measured by UV/Vis and solution photoluminescence (PL) spectroscopies in aqueous solvents. The solution PL spectra showed broad emission peaks around 600 nm with PL efficiencies of 9.7% (ZnS:Mn-Ser) and 15.4% (ZnS:Mn-Thr) respectively. The measured particle sizes for the aminoacid capped ZnS:Mn nanocrystals by HR-TEM images were about 3.0-4.0 nm, which were also supported by Debye-Scherrer calculations. In addition, cytotoxic effects of four aminoacids capped ZnS:Mn nanocrsystals over the growth of wild type E. coli were investigated. Although toxicity in the form of growth inhibition was observed with all the aminoacids capped ZnS:Mn nanocrystals at higher dose (1 mg/mL), ZnS:Mn-Met and ZnS:Mn-Thr appeared non-toxic at doses less than 100 ${\mu}g$/mL. Low biological toxicities were seen at doses less than 10 ${\mu}g$/ mL for all nanocrystals.

• Korean Journal of Materials Research
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• v.33 no.7
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• pp.315-322
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• 2023

In the present work, we address the new route for the green synthesis of manganese dioxide (MnO₂) by an innovative method named the solution plasma process (SPP). The reaction mechanism of both colloidal and nanostructured MnO₂ was investigated. Firstly, colloidal MnO₂ was synthesized by plasma discharging in KMnO₄ aqueous solution without any additives such as reducing agents, acids, or base chemicals. As a function of the discharge time, the purple color solution of MnO₄^- (oxidation state +7) was changed to the brown color of MnO₂ (oxidation state +4) and then light yellow of Mn²⁺ (oxidation state +2). Based on the UV-vis analysis we found the optimal discharging time for the synthesis of stable colloidal MnO₂ and also reaction mechanism was verified by optical emission spectroscopy (OES) analysis. Secondly, MnO₂ nanoparticles were synthesized by SPP with a small amount of reducing sugar. The precipitation of brown color was observed after 8 min of plasma discharge and then completely separated into colorless solution and precipitation. It was confirmed layered type of nanoporous birnessite-MnO₂ by X-ray powder diffraction (XRD), fourier-transform infrared spectroscopy (FT-IR), and electron microscopes. The most important merits of this approach are environmentally friendly process within a short time compared to the conventional method. Moreover, the morphology and the microstructure could be controllable by discharge conditions for the appropriate potential applications, such as secondary batteries, supercapacitors, adsorbents, and catalysts.

• Journal of the Korean Chemical Society
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• v.55 no.1
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• pp.19-27
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• 2011

New series of Mn(II), Ni(II), Co(II), Cu(II) and Zn(II) of the 2-(benzothiazol-2-yl)-N'-(2,5-dihydroxybenzylidene) acetohydrazide have been synthesized and characterized by elemental analysis, IR, UV-vis, $^1H$-NMR, mass and ESR spectra, magnetic susceptibility and molar conductivity measurements. The spectral data and magnetic measurements of the complexes indicate that, the geometries are either square planar or octahedral. The biological activity of the ligand and its complexes against fungi (Aspergillus nigar and Fusarium oxysporium) were investigated. The metal complexes exhibited higher activity than both the parent ligand and the corresponding metal ion.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.29.1-29.1
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• 2011

The selective catalytic reduction (SCR) of $MnO_x$ with $NH_3$ is an effective method for the removal of $MnO_x$ from stationary system. The typical catalyst for this method is $V_2O_5-WO_3(MoO_3)/TiO_2$, caused by the high activity and stability. However, This catalyst is active within $300{\sim}400^{\circ}C$ and occurs the pore plugging from the deposition of ammonium sulfate salts on the catalysts surface. It needs to locate the SCR unit after the desulfurizer and electrostatic precipitator without reheating of the flue gas as well as deposition of dust on the catalyst. The manganese oxides supported on titania catalysts have attracted interest because of its high SCR activity at low temperature. The catalytic activity of $MnO_x/TiO_2$ SCR catalyst with different manganese precursors have investigated for low-temperature SCR in terms of structural, morphological, and physico-chemical analyses. The $MnO_x/TiO_2$ were prepared from three different precursors such as manganese nitrate, manganese acetate (II), and manganese acetate (III) by the sol-gel method and then it calcinated at $500^{\circ}C$ for 2 hr. The structural analysis was carried out to identify the phase transition and the change intensity of catalytic activity by various manganese precursors was analyzed by FT-IR and Raman spectroscopy. These different precursors also led to various surface Mn concentrations indicated by SEM. The Mn acetate (III) tends to be more suppressive the crystalline phase (rutile), and it has not only smaller particle size, but also better distributed than the others. It was confirmed that the catalytic activity of MA (III)-$MnO_x/TiO_2$ was the highest among them.

• Journal of the Korean Chemical Society
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• v.32 no.5
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• pp.464-475
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• 1988

The complex formation of p-aminoazobenzene and its derivatives with Fe(III) and Mn(II) has been studied by UV and IR spectroscopy and conductometry. The effects of solvents, donor basicity, and other factors on the formation of these complexes have been examined. The vatio of metal to ligand for the complexes formed is 1 : 1, both in the solid state and in solution. The stability constants of Fe(III)-donor and Mn(II)-donor complexes are in the range of 10$^2$∼10$^4$ and 0.1∼1, respectively. The absorptivities are ~10$^4$ and ∼10$^3$ l/mol${\cdot}$cm respectively. Thermodynamic properties such as ${\Delta}H^{\circ}$, ${\Delta}G^{\circ}$ and ${\Delta}S^{\circ}$ are calculated from their stability constants utilizing Van't Hoff equation.

• Bulletin of the Korean Chemical Society
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• v.35 no.12
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• pp.3601-3608
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• 2014

RGB light emitting ZnSe based nanocrystals: ZnSe (blue), ZnSe:Cu (green) and ZnSe:Mn (red) were synthesized by capping the surface of the nanocrystals with oleic acid. The obtained nanocrystal powders were characterized by using XRD, HR-TEM, ICP-AES, FT-IR, and FT-Raman spectroscopies. The optical properties were also measured by UV/Vis and photoluminescence (PL) spectroscopies. The PL spectra showed broad emission peaks at 471 nm (ZnSe), 530 nm (ZnSe:Cu) and 665 nm (ZnSe:Mn), with relative PL efficiencies in the range of 0.7% to 5.1% compared to a reference organic dye standard. The measured average particle sizes from the HR-TEM images for those three nanocrystals were 4.5 nm on average, which were also supported well by the Debye-Scherrer calculations. The elemental compositions of the ZnSe based nanocrystals were determined by ICP-AES analyses. Finally, the drawn CIE diagram showed the color coordinates of (0.15, 0.16) for ZnSe, (0.22, 0.57) for ZnSe:Cu, and (0.62, 0.35) for ZnSe:Mn respectively, which were fairly well matched to that of the RGB color standards.

• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.189-196
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• 2014

Water dispersible ZnS based nanocrystals: ZnS (blue), ZnS:Cu (green) and ZnS:Mn (yellow-orange) were synthesized by capping the surface of the nanocrystals with a mercaptopropionic acid (MPA) molecule. The MPA capped ZnS based nanocrystal powders were characterized by using XRD, HR-TEM, EDXS, FT-IR, and FT-Raman spectroscopy. The optical properties of the colloidal nanocrystals were also measured by UV/Vis and photoluminescence (PL) spectroscopies in aqueous solvents. The PL spectra showed broad emission peaks at 440 nm (ZnS), 510 nm (ZnS:Cu) and 600 nm (ZnS:Mn), with relative PL efficiencies in the range of 4.38% to 7.20% compared to a reference organic dye. The measured average particle sizes from the HR-TEM images were in the range of 4.5 to 5.0 nm. White light emission was obtained by mixing these three nanocrystals at a molar ratio of 20 (ZnS):1 (ZnS:Cu):2 (ZnS:Mn) in water. The measured color coordinate of the white light was (0.31, 0.34) in the CIE chromaticity diagram, and the color temperature was 5527 K.

• Journal of the Korean Ceramic Society
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• v.44 no.10
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• pp.554-561
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• 2007

Synthesis and characterization of pigments by using $Fe_2O_3,\;CoO,\;Cr_2O_3\;and\;MnO_2$ were undertaken. The resulting pigments were characterized by using XRD, SEM, FT-IR and UV-Vis spectrophotometer. The color of glazed tiles containing 6 wt% pigment changed from dark green to black depending on the compositions of used materials. Pigments were calcined with mixed materials at $1350^{\circ}C$, and the dark green and dark brown color were obtained. Pigments were used to determine possible interactions between a pigment and a glaze.