• Macromolecular Research
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• v.17 no.11
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• pp.907-911
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• 2009

To improve the moisture stability of the $CaS:Eu^{2+}$ red phosphor, surface coatings with silica nanoparticles were performed using five different methods, i.e., $P_1$, $P_2$, $P_3$, $P_4$, and $P_5$. The phosphors were coated with silica nanoparticles using a dip coating method ($P_1$) and sol-gel method ($P_2$). The phosphors were coated using a solution containing silica nanoparticles and poly(1-vinyl-2-pyrrolidone), PVP, $(P_3$). The phosphors were also coated with silica nanoparticles by reacting with the 1-vinyl-2-pyrrolidone (VP) monomer ($P_4$) or by reacting with mixtures containing VP and tetraethylorthosilicate ($P_5$). A decrease in the photoluminescence (PL) intensity was observed regardless of the coating methods. However, the moisture stability of the phosphors was enhanced by the coating when aged in a temperature-controlled humidity chamber. Among these methods, the $P_4$ (or $P_5$) method exhibited the greatest increase in moisture stability of the phosphors. The coated phosphors showed a relatively constant intensity with aging time, whereas the uncoated phosphor showed a decrease.

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.1006-1013
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• 1997

This study was carried out to elucidate the chemical characteristics of mutual separation for Am and Eu, which were selected as a stand-in from minor actinide and rare earth elements, by solvent extraction with di-(2-ethylhexyl)phosphoric acid containing zirconium at batch system. As results, 92.3% of Am and 99.1% of Eu were coextracted with 1M DEHPA/n-dodecane containing zirconium (Zr $concentration=8.7g/{\ell}$) at 0.5M $HNO_3$ in the extraction step. The extraction yields of Am and Eu were proportionally increased with the concentration of Zr in Zr salt of 1M DEHPA/n-dodecane having the synergistic effect. In the lst stripping step for the selective separation of Am, 38.1% of Am and 3% of Eu were stripped with the mixed solution of 0.05M DTPA and 1M lactic acid adjusted pH of 3.0. At that time, the separation factor calculated from the distribution coefficients of Am and Eu was 14.2. In the 2nd Stipping step to remove the Eu remained the organic phase after the lst stripping step, 94.4% 0f Eu was stripped into aqueous phase with 6M $HNO_3$.

• Economic and Environmental Geology
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• v.40 no.4
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• pp.361-374
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• 2007

Rare earth elements(REEs) have been used as an useful tool in understanding the various geological processes such as evolution and differentiation in the crust. The REEs also have been used as an analog of actinides for radioactive wastes at the water-rock interactions. Using physicochemical properties of the REEs and actinides, we have shown that Eu is an optimum analogue for understanding the behavior of Am in subsurface environments. Factors affecting sorption behavior of radioactive nuclides in groundwater were investigated by batch experiments. Four nuclides such as $^{241}Am,\;^{152}Eu,\;^{160}Tb\;and\;^{60}Co$ were selected to test our hypothesis, and $^{160}Tb$ and $^{60}Co$ were specifically used to compare to the sorption behavior between $^{241}Am-^{152}Eu$ and other radioactive nuclides. Four different rock samples and one groundwater were used in the batch experiments where solution pH for all experiments was fixed at 5.5. Our results demonstrate that $^{241}Am,\;^{152}Eu,\;and\;^{160}Tb$ show similar sorption behavior whereas $^{60}Co$ is different in sorption behavior at the mineral-water interface, suggesting that the sorption behavior of $^{60}Co$ is affected by different rock types. Our results also show that 1) Eu in REEs is optimum analogue of fate and transport of Am in subsurface environments, and 2) mineral compositions such as $SiO_2,\;TiO_2,\;P_2O_5$ and distribution of REEs such as Eu anomaly play key roles in affecting sorption behavior of radioactive nuclides even though physicochemical properties of geological materials such as specific surface area and cation exchange capacity can not be ruled out.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.581-584
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• 2008

$BaMgP_2O_7$:Eu,Mn phosphors for white emission were synthesized and their luminescent properties were investigated under UV excitation. The phosphor emits two colors: a blue band by $Eu^{2+}$ and a red band by $Mn^{2+}$. Due to the efficient energy transfer from $Eu^{2+}$ to $Mn^{2+}$, the red emission positioned at 615 nm is greatly enhanced with increasing $Mn^{2+}$ content up to 17.5 mol%.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05b
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• pp.853-858
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• 1995

$^{152}$EU, $^{241}$Am 및 $^{241}$Np를 선정하여 추출제 di-(2-ethylhexyl)phosphoric acid (DEHPA)로 이들 세가지 핵종의 상호 분리공정에 대해 연구하였다. 추출공정에서 질산농도는 0.IM이고 추출 제DEHPA/n-dodecane 농도가 IM 일때, $^{152}$Eu 및 $^{241}$Am, $^{241}$Np 핵종 모두 99.9% 이상 추출되었다. $^{241}$Am 핵종의 역추출을 위한 제 1 역추출공정에서 역추출제인 0.05M di-ethylenetriamine pentaacetic acid (DTPA)와 1.5M 젖산 (lactic acid) 혼합용액의 pH가 3.6 일때 $^{152}$Eu과 $^{241}$Am의 상호분리비와 역추출율이 가장 좋았다. $^{152}$Eu의 역추출을 위한 제 2 역추출단계에서 역추출제인 질산용액의 최적농도는 6M이며, 이때 $^{152}$Eu은 99%가 역추출되었다.$^{241}$Np 핵종의 역추출을 위한 제 3 역추출공정에서 역추출제는 0.5M 옥살산이며, 이때 $^{241}$Np은 92%가 역추출되었다.

• Korean Journal of Materials Research
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• v.18 no.10
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• pp.511-514
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• 2008

We have synthesized $Eu^{3+}$-doped $YVO_4$ phosphors by using a hydrothermal method and investigated their luminescent properties. Aqueous solutions of $Y_2O_3,\;V_2O_5,\;Eu_2O_3$, and nitric acid with various pH values were used as the precursors. The crystallinity, surface condition, and emission characteristics were examined using XRD, FT-IR, and photo-excited spectrometer. $Eu^{3+}$ incorporation followed by the efficient red emission strongly depends on the acidity of solution media. The emission intensity becomes stronger as the pH values increase to 7 and then gradually decreases. This phenomenon might be related to the hydroxyl quenching effect, which is induced by surface bound OH-groups.

• Nuclear Engineering and Technology
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• v.15 no.2
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• pp.142-148
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• 1983

Distribution coefficients between cation exchange resin (Dowex 50W$\times$8) and $\alpha$-hydroxyisobutric acid ($\alpha$-HIBA) are measured in order to separate traces of Sm, Eu, Gd and Dy from nuclear material. Individual separations are performed by pH gradient technique with 0.40M $\alpha$-HIBA from 3.40 to 3.60 in cation exchange resin after a group separation. Each of separated elements is determined with a fluorometric method except Gd by colorimetry. The results are applied to analyze Sm, Eu, Gd and Dy in magnesium diuranate (yellow cake).

• Applied Biological Chemistry
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• v.37 no.6
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• pp.447-450
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• 1994

Rate of hydrolysis ethylene phosphate, dimethylphosphate and hydroxyethylmethylphosphate in neutral water have been measured. Hydrolysis of ethylene phosphate proceeds with P-0 bond cleavage $(k_{obs}=3{\times}10^{-7}s^{-1}\;at\;100^{\circ}C,\;{\Delta}H{\neq}=24\;kcal,\;{\Delta}S{\neq}=25.5\;eu)$. In constrast, hydrolysis of dimethylphosphate proceeds with C-O bond cleavage $(k_{obs}=3{\times}10^{-7}s^{-1}\;at\;150^{\circ}C)$. The rate constant for P-O bond cleavage of dimethylphosphate is estimated at $1{\times}10^{-11}s^{-1}\;at\;150^{\circ}C,\;({\Delta}H{\neq}=36\;kcal,\;{\Delta}S{\neq}=25.5\;eu)$. A phosphodiesterase catalyzed hydrolysis of dimethylphosphate is $10^{17}$ times faster than the simple water rate. The observed rate of hydrolysis of hydroxyethylmethylphosphate is comparable to that of dimethylphosphate indicating C-O bond cleavage $(k_{obs}=6{\times}10^{-7}s^{-1}\;at\;150^{\circ}C)$.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1514-1517
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• 2005

The $(Y,Gd)BO_3:Eu^{3+}$ phosphor was made by coprecipitation method. The precipitated powders were amorphous. The value of pH in the process of coprecipitation was critical for the luminescence of phosphors. The particle size and morphology were influenced by pH value. The lower calcination temperature and hydrothermal synthesis leads to the distortion of lattices. The distorted lattices changed the symmetry of $Eu^{3+}$ site. The broken inversion symmetry in the distorted lattice caused the increased emission of $^5D_0{\rightarrow}^7D_2$ transition.

• Journal of Veterinary Clinics
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• v.2 no.1
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• pp.121-131
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• 1985

Mouse embryos of 8-cell stage and compacted morulae(approximately 16 cells) containing different number of blastomeres were bisected and cultured in vitro to determine the developmental potentials of the divided embryos compared with those of unmanipulated control embryos. The results were as follows. 1. Micromanipulation was performed successfully by means of a simple manipulator which holds a fine glass, needle, without the use of any micro-instruments for support. 2. The percentage of bisected morulae with 7-9 blastomeres that developed to eu-blastocyst was 94.1% while only 64.8% of the bisected 8-cell embryos with 4 blastomeres developed to eublastocysts (p<0.05). 3. The percentage of eu-blastocysts decreased, while that of pseudoblastocysts and trophectodermal vesicle increased as the number of blastomeres decreased in the bisected embryos of the two stages. 4. The time of the blastocoele re-formation of the bisected and control embryos was not significantly different in morulae stage embryos, but it was significantly delayed in the 8-cell stage embryos (Eu-B, Pseudo-B) compared with control embryos (P<0.01, P<0.05 respectively).