• 공업화학
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• 제10권1호
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• pp.51-57
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• 1999

원자로 정지시 냉각제 계통내 탈염 공정의 최적운전에 도움을 줄 목적으로 Amberite IRN 77 양이온 교환수지상에서 Ni(II), Co(II) 및 Ag(I) 이온의 흡착특성을 연구하였다. 양이온 교환수지상에서 Ni(II), Co(II) 및 Ag(I) 이온 각각의 흡착 메카니즘은 Langmuir isotherm에 잘 일치하였다. 양이온교환수지의 형태에 따른 영향으로서 $H^+$-형의 수지의 흡착 및 처리 용량은 $Li^+$-형의 수지보다 우수하였다. 다성분계의 용액을 위한 연속식 이온교환공정에서 양이온교환수지의 흡착선택성은 Ni(II)${\approx}$Co(II)>Ag(I)였으며, 유속의 증가는 수지의 처리용량 뿐만 아니라 파과곡선의 기울기를 감소시켰다.

• Journal of Microbiology and Biotechnology
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• 제28권10호
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• pp.1654-1663
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• 2018

Finding a safe and broad-spectrum medication is a goal of scientists, pharmacists, and physicians, but developing and fabricating the right medicine can be challenging. The current study describes the formation of silver nanoparticles (AgNPs) by Fusarium mangiferae. It involves the antibiofilm activity of the nanoparticles against Staphylococcus aureus. It also involves cytotoxic effect against mammalian cell lines. Well-dispersed nanoparticles are formed by F. mangiferae. The sizes of the nanoparticles were found to range from 25 to 52 nm, and UV-Vis scan showed absorption around 416-420 nm. SEM, TEM, and AFM results displayed spherical and oval shapes. Furthermore, the FTIR histogram detected amide I and amide II compounds responsible for the stability of AgNPs in an aqueous solution. AgNPs were observed to decrease the formation of biofilm at 75% (v/v). DNA reducing, smearing, and perhaps fragmentation were noticed after treating the bacterial cells with 50% (v/v). Additionally, cell lysis was detected releasing proteins in the supernatant. It was also observed that the AgNPs have the ability to cause 59% cervical cancer cell line (HeLa) deaths at 25% (v/v), however, they showed about 31% toxicity against rat embryo fibroblast transformed cell lines (REF). The results of this study prove the efficiency of AgNPs as an antibiofilm against S. aureus, suggesting that AgNPs could be an alternative to antibiotics. It must also be emphasized that AgNPs displayed cytotoxic behavior against mammalian cell lines. Further studies are needed for assessing risk in relation to the possible benefit of prescribing AgNPs.

• Progress in Superconductivity
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• 제1권1호
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• pp.61-67
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• 1999

We evaluated the effect of alloying element additions to Ag sheath on mechanical, electrical and thermal properties of Bi-2223. Additions of Au, Pd and Mg to Ag sheath increased hardness and strength, while reduced elongation and electrical and thermal conductivity. In addition, microstructural investigation showed that the grain size of Ag significantly decreased with increasing content of alloying elements. The improvements in strength and hardness are believed to be due to the presence of alloying elements that lead to strengthen materials by combined effects of solid-solution, dispersion hardening and grain size hardening. Thermal conductivity of Ag and Ag alloys was evaluated in the temperature range from 77 K to 300 K, and com-pared to calculated value obtained by Wiedermann-Franz law. It was observed that the thermal conductivity decreased with increasing the content of alloying elements. Specifically, the thermal conductivity of $Ag_{0.92}Pd_{0.06}Mg_{0.02}$ alloy was measured to be $48.2W/(m{\cdot}K)$ at 77 K, which is about 6 times lower than that of $Ag(302.6W/(m{\cdot}K))$.

• 한국진공학회지
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• 제17권5호
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• pp.442-447
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• 2008

강유전체 0.65Pb$(Mg_{1/3}Ta_{2/3})O_3-0.35PbTiO_3$ 고용체에 $Ag_2O$를 첨가하여 $1200^{\circ}C$에서 소결하여 시료를 제작하였다. 완성된 시료의 미세구조는 주사 전자현미경(SEM)을 이용하여 관찰하였고, 전기적 특성의 관찰을 위하여 유전상수와 유전손실, 초전계수를 측정하였다. 제작된 시료 중에서 0.2 mol%의 $Ag_2O$를 과잉 첨가한 시료에서 유전상수와 초전계수가 가장 크게 나타났다. 각 시료에서 유전상수와 초전계수의 최대값의 온도는 $Ag_2O$ 첨가량이 증가할수록 저온으로 이동하였다.

• 한국태양에너지학회 논문집
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• 제34권5호
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• pp.65-72
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• 2014

In this paper, the water-based Ag nanofluids are synthesized by the chemical reduction method and their extinction coefficients are measured by an in-house developed measurement device. The Ag nanofluids are manufactured by the chemical reduction method with the mixing of silver nitrate ($AgNO_3$) and sodium borohydride ($NaBH_4$) in an aqueous solution of polyvinyl pyrrolidone (PVP). The extinction coefficients of Ag nanofluids are measured by means of the in-house developed apparatus at a wavelength of 632.8nm according to the particle volume fractions. The results show that the extinction coefficient of water-based Ag nanofluids increases with the increase of nanoparticle concentrations. Finally, the temperature field and efficiency of direct absorption solar collector (DASC) are analytically estimated based on the measured extinction coefficient of water-based Ag nanofluids. The results indicate that the direct absorption solar collectors using nanofluids have the feasibility to improve the efficiency of conventional flat-plate solar collectors without using an absorber plate.

• 멤브레인
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• 제21권1호
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• pp.39-45
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• 2011

원자전달 라디칼 중합(ATRP)에 의해 poly(vinyl chloride) (PVC) 주사슬과 poly(styrene sulfonic acid) (PSSA) 곁사슬로 되어있는 양쪽성 PVC-g-PSSA 가지형 공중합체를 합성하였다. 합성된 고분자 전해질막을 10 wt% $AgNO_3$ 수용액에 담가 은이온으로 이온교환을 하였으며, 환원제를 통하여 은 나노입자를 성장시켰다. UV분광학과 XRD 분석을 통해 은 나노입자 성장을 확인하였다. 투과전자현미경(TEM) 분석결과 $NaBH_4$를 사용하였을 때 10~20 nm 크기의 은 나노입자를 얻는데 가장 효과적임을 알 수 있었다. 또한 은 나노입자의 성장은 환원제의 농도와 환원 시간에 크게 영향을 받았다.

• 방사성폐기물학회지
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• 제8권3호
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• pp.201-205
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• 2010

고준위방사성폐기물에서 유출되어 나오는 아이오딘의 이동을 저지하기 위하여 은을 흡착시킨 벤토나이트 블록에 NaI 용액을 흘려주었을 때 대부분의 아이오딘이 흡착되었다. 이 은이온에 의한 아이오딘의 저지 메커니즘을 상세히 조사하기 위하여 아이오딘과 접촉하기 전후의 은이 흡착된 벤토나이트의 X-ray Absorption Near Edge Structure (XANES)와 Extended X-ray Absorption Fine Structure (EXAFS) 스펙트 럼과 표준물질로서 AgO, $Ag_2O$, AgI의 스펙트럼을 비교하였다. 그 결과, 벤토나이트에 흡착되었던 은이 떨어져 나와 AgI 침전 클러스터를 형성함으로서 아이오딘의 이동이 지연되는 것으로 생각된다.

• 분석과학
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• 제8권4호
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• pp.663-668
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• 1995

Ion transport of a polypyrrole/chloride (PPy/Cl) film and a polypyrrole/poly(styenesulfonate) (PPy/PSS) film as a function of applied dc potential was investigated by employing electrogravimetric impedance technique and electrochemical impedance technique. The cation and anion contribution to the whole charge capacitance and the diffusion coefficients of cation and anion in a PPy/PSS film were calculated by fitting the electrogravimetric impedance data with proposed model circuit. The diffusion coefficients of $Na^+$ in a 1 M $NaClO_4$ solution are over 1 order of magnitude larger than those of $ClO{_4}^-$, and $ClO{_4}^-$ contribution to charge compensation decreases as dc potential lowers. The charge compensation of a PPy/Cl film ir a 1 M CsCl solution is carried out largely by $Cl^-$ at 0.2 V vs. Ag/AgCl and by $Cs^+$ as well as $Cl^-$ at -0.4 V.

• 분석과학
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• 제8권4호
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• pp.655-661
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• 1995

The electrochemical reduction of coumarin derivatives in 0.1M TEAP acetonitrile solution was investigated by the direct current, differential pulse polarography, cyclic voltammetry and controlled potential coulometry. The electrochemical reduction of 7-acetoxy-4-bromomethyl-coumarin(ABMC) was proceeded as an irreversible three steps(-0.58, -1.63 and -2.25 volts) of electrochemical transfer before chemical reaction. The solution color turned to yellow after the carboxyl group was reduced at 2nd step(-1.63 volts vs. Ag-AgCl) and the change in color was independant to the bromo group. Upon the basis of the results on the products analysis and the interpretaton of polarograms, a possible electrochemical reaction mechanism was suggested.

• Bulletin of the Korean Chemical Society
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• 제30권12호
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• pp.2943-2948
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• 2009

Copper-dimethylglyoxime complex (CuDMG) modified Copper electrode (Cu/CuDMG) showed a catalytic activity towards cyclohexanol oxidation in NaOH solution. The modified electrode prepared by the dimethylglyoxime anodic deposition on Cu electrode in the solution contained 0.20 M $NH_4Cl\;+\;NH_4OH\;(pH\;9.50)\;and\;1\;{\times}\;10^{-4}$ M dimethylglyoxime. The modified electrode conditioned by potential recycling in a potential range of -900${\sim}$900 mV vs. Ag/AgCl by cyclic voltammetry in alkaline medium (1 M NaOH). The results show that the CuDMG film on the electrode behaves as an efficient catalyst for the electro-oxidation of cyclohexanol in alkaline medium via Cu (III) species formed on the electrode.