• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.2
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• pp.57-62
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• 2007

Willemite green phosphor powders have been prepared by the metallo-organic decomposition (MOD) method, and the photoluminescence and phase formation were studied as a function of both the firing temperature ($800{\sim}1100^{\circ}C$) and the concentration of Mn activator ($4{\sim}12 mol%$). Under 254 nm excitation source, the emission intensity of the phosphors increased with increasing the firing temperature from 800 to $1000^{\circ}C$. From the XRD analysis, the powders heat-treated above $1000^{\circ}C$ showed willemite crystal structure. The maximum emission intensity was obtained far the phosphors heat-treated at $1000^{\circ}C$ with 8 mol% of Mn content. The concentration quenching was occurred when the Mn concentration exceeded 10 mol%. The phosphor particles showed spherical shapes with the average size of $0.4{\sim}0.5{\mu}m$ by the SEM morphology.

• Korean Journal of Materials Research
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• v.21 no.6
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• pp.352-356
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• 2011

[ $Zn_{2(1-x)}Mn_xSiO_4$ ]$0.07{\leq}x{\leq}0.15$) green phosphor was prepared by solid state reaction. The first heating was at $900^{\circ}C-1250^{\circ}C$ in air for 3 hours and the second heating was at $900^{\circ}C$ in $N_2/H_2$(95%/5%) for 2 hours. The size effect of $SiO_2$ in forming $Zn_2SiO_4$ was investigated. The temperature for obtaining single phase $Zn_2SiO_4$ was lowered from $1100^{\circ}C$ to $1000^{\circ}C$ by decreasing the $SiO_2$ particle size from micro size to submicro size. The effect of the activators for the Photoluminescence (PL) intensity of $Zn_2SiO_4:Mn^{2+}$ was also investigated. The PL intensity properties of the phosphors were investigated under vacuum ultraviolet excitation (147 nm). The emission spectrum peak was between 520 nm and 530 nm, which was involved in green emission area. $MnCl_2{\cdot}4H_2O$, the activator source, was more effective in providing high emission intensity than $MnCO_3$. The optimum conditions for the best optical properties of $Zn_2SiO_4:Mn^{2+}$ were at x = 0.11 and $1100^{\circ}C$. In these conditions, the phosphor particle shape was well dispersed spherical and its size was 200 nm.

• The Korean Journal of Zoology
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• v.23 no.3
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• pp.137-148
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• 1980

The effects of divalent cations, $Hg^{2+}, Cu^{2+}, Pb^{2+}, Cd^{2+}$, and $Mn^{2+}$ on the total ATPase activity of the fragmented sarcoplasmic reticulum isolated from rabbit skeletal muscle were investigated. The inhibitory effects of the cations on the enzyme activity increased as the concentrations of the ions increased with the order of efficiency of $Hg^{2+}$ > $Cu^{2+}$ > $Pb^{2+}$ > $Cd^{2+}$ > $Mn^{2+}$ in the concentration range between 10 and 500$\mu$M. The 50% inhibition for each ion was almost identical with the inhibition constant (Ki) value for each ion. The Ki's were 10, 30 130, and 350$\mu$M for $Hg^{2+}, Cu^{2+}, Pb^{2+}, and Cd^{2+}$, respectively. $Mn^{2+}$ seemed to be an activator at lower concentrations and an inhibitor at higher concentrations. The presence of the cations did not change the Km values, suggesting that the ions act as a reversible noncompetitive inhibitor on the FSR ATPase. The energy of activation of the enzyme was aproximately 19 Kcal/mole. The presence of the ions decreased the value slightly. A possible mechanism for the reversible noncompetitive inhibitory effect of the cations was discussed.

• Journal of Sensor Science and Technology
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• v.15 no.5
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• pp.323-327
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• 2006

Manganese, copper and chlorine-doped ZnS phosphors (ZnS:Mn,Cu,Cl) were synthesized through solid-state reaction. Manganese was added in the range of amount $1.4{\sim}5.3$ mol % to ZnS phosphors containing 0.2 or 1.0 mol % of copper and a small amount of chlorine. As-synthesized phosphors showed a spherical morphology with a mean size of ${\sim}20\;{\mu}m$ and structural properties of Wurtzite, which were identified by SEM and XRD, respectively. Optical properties of ZnS:Mn,Cu,Cl synthesized with various concentrations of activators were analysed by both of PL and EL spectra. Samples mainly showing only 580 nm-orange emission by 380 nm-UV excitation gave different EL spectra of blue, green, and orange emissions at 450, 480 and 580 nm, respectively, depending on concentrations of $Cu^{2+}$ and $Mn^{2+}$.

• Korean Journal of Materials Research
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• v.9 no.1
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• pp.46-50
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• 1999

$\textrm{Zn}_{2-x}\textrm{Mn}_{x}\textrm{SiO}_{4}$ green phosphors have been prepared by the solution reaction method and the photoluminescence and crystalline properties were studied as a function of both the firing temperature ($900^{\circ}C$~$1200^{\circ}C$) and the concentration of Mn activator (x=0.01~0.20). Under 147 nm and 254nm and excitation sources, the emission intensity of the phosphors was increased about 4 times increasing firing temperatures from $900^{\circ}C$ to $1200^{\circ}C$. From the XRD analysis, $\textrm{Zn}_{2}\textrm{SiO}_{4}$:Mn phosphors fired above $1100^{\circ}C$ showed willemite crystal structure. Under 147nm excitation, the maximum emission intensity was obtained at the Mn concentration of x=0.02 for $\textrm{Zn}_{2-x}\textrm{Mn}_{x}\textrm{SiO}_{4}$ phosphors fired at $1200^{\circ}C$ and the concentration quenching was occurred at the Mn concentration above x=0.10. The phosphor particles showed almost spherical shapes with the average size of around 2~3$\mu\textrm{m}$ by the SEM morphology.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.5
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• pp.432-436
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• 2006

The $ZnGa_2O_4$ and Mn, Cr-doped $ZnGa_2O_4$ Phosphors were synthesized through conventional solid state reactions. The XRD patterns show that the $ZnGa_2O_4$ has a (3 1 1) main peak and a spinel phase. The emission wavelength of $ZnGa_2O_4$ showed main peak of 420 nm and maximum intensity at the sintering temperature of $1100^{\circ}C$. In the crystalline $ZnGa_2O_4$, the Mn shows green emission (510 nm, $^4T_1-^6A_1$) with a quenching concentration of 0.6 mol%, and the Cr shows red emission (705 nm, $^4T_2-^4A_2$) with a quenching concentration of 2 mol%. These results indicate that $ZnGa_2O_4$ Phosphors hold promise for potential applications in field emission display devices with high brightness operating in full color regions.

• Journal of Life Science
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• v.14 no.4
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• pp.636-643
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• 2004

D-Xylose isomerase produced by Lactococcus sp. JK-8, isolated from kimchi, was purified 17-fold of homogeneity, and its physicochemical properties were determined. Although the N-terminal amino acid sequence of D-xylose isomerase was analysed to Ala-Tyr-Phe-Asn-Asp-Ile-Ala-Pro-Ile-Lys, it was not similar to that of Lactobacillus enzyme. The molecular weight of the purified enzyme was estimated to be 180 kDa by gel filtration, 45 kDa by SDS-PAGE and the enzyme was homotetramer. The optimum pH of the enzyme was around 7 and stable between pH 6 and 8. The optimum reaction temperature was 7$0^{\circ}C$ and stable up to 7$0^{\circ}C$ in the presence of 1 mM $Mn^{2+}$. Like other D-xylose isomerases, this enzyme required divalent cation, such as $Mg^{2+}$, $Co^{2+}$, or $Mn^{2+}$ for the activity and thermostability. $Mn^{2+}$was the best activator. Substrate specificity studies showed that this enzyme was highly active on D-xylose. The enzyme had an isoelectric point of 4.8, and fm values for D-xylose was 5.9 mM.

• Microbiology and Biotechnology Letters
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• v.25 no.4
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• pp.408-413
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• 1997

It was studied in order to improve the yield of serrapeptase production in fermentation that organic nitrogen sources play important roles not only as inducer, repressor and activator, but also nitrogen sources. From the investigation of the effect of Na-caseinate on the induction of serrapeptase production, it was elucidated that real inducer was leucine and strong repressor was cysteine, which were produced through hydrolysis of proteins. Serrapeptase production was strongly induced by Na-caseinate in culture time 12 hrs, but was weakly induced before and after that time. Therefore fed batch culture where partial amount of Na-caseinate is added in 12 hrs, is better than batch culture where total amount of Na-caseinate is added at the beginning. Cysteine, methionine, MgSO$_{4}$, and so on, sulfur-containing materials, repressed the serrapeptase production. In the addition of mineral salts, chlorinated salts is better than sulfated salts because of sulfur repression. The synergic effect of soybean meal with Na-caseinate on the serrapeptase production resulted from Mn$^{2+}$ contained in soybean meal, of which the optimal concentration is 4 mM in enzyme production.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.301-302
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• 2005

The $ZnGa_2O_4$:Cr phosphor was synthesized through solid-state reactions at the various molar ratio of Cr from 0.002 % to 0.01 %. The XRD patterns show that the Cr-doped $ZnGa_2O_4$ has a (311) main peak and a spinel phase. Also the emission wavelength shills from 510 to 705 nm in comparison with $ZnGa_2O_4$:Mn when Cr is doped in $ZnGa_2O_4$. These results indicate that $ZnGa_2O_4$ phosphors hold promise for potential applications in field-emission display devices with high brightness operating in full color regions.

• Advances in concrete construction
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• v.10 no.5
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• pp.403-416
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• 2020

This study investigated the effect of alkaline activators - NaOH_aq (NH) (NH: 0-16 M) and Na₂SiO_3aq (NS) (NS/NH: 0-3.5) in the synthesis of silico-manganese fume (SMF) and ground blast furnace slag (BFS) blended alkali-activated mortar (AASB). The use of individual activator was ineffective in producing AASB of sufficient fresh and hardened properties, compared to the synergy of both activators. This may be attributed to incomplete dissolution and condensation of oligomers required for gelation of the binder. An inverse relationship was noted among the fresh properties and the NH concentration or NS/NH ratio. This was influenced by the dissolution and condensation of silicate monomers under polymerization process. The maximum 28-day strength of ~45 MPa, setting time of 60 min and flow of 182 mm was obtained with the use of combined activators (10M-NH and NS/NH=2.5). The combined activators at NS/10M-NH=2.5 constituted SiO₂/Na₂O, H₂O/Na₂O and H₂O/SiO₂ molar ratio of 1.61, 17.33 and 10.77, respectively. This facilitated the formation of C-S-H, C/K-A-S-H and C-Mn-S-H in the framework together with an increase in the crystallinity due to more silicate re-organization within the aluminosilicate chain. On comparison of the high concentrated with mild alkali synthesized product, it revealed that the concentration of OH^- and Si monomers together with alkali metals influenced the dissolution of precursors and embedment of the constituent elements in the polymeric matrix. These factors eventually contributed to the microstructural densification of the mortar prepared with NS/10M-NH=2.5 thereby enhancing the compressive strength.