• Analytical Science and Technology
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• v.13 no.2
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• pp.151-157
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• 2000

Effects of acids and pre-reductants in the analysis of arsenic have been studied by hydride generation-atomic absorption spectrometry. The analytical results were strongly dependent on the acid concentrations. All the pre-reductants was very effective to observe the arsenic signal at strong acid concentrations (3 M-5 M). However, at the low acid condition (${\leq}0.1M$), L-cysteine only showed a reasonable effect on the absorption signal. When the sample was treated with the nitric acid, absorption signal was unstable and was also decreased. Although interference effects were observed from metal ions such as $Cr^{6+}$ and $Br^{5+}$ at low acid condition, the generation of hydride could be increased by the strong acid condition.

• Applied Biological Chemistry
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• v.24 no.3
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• pp.167-173
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• 1981

Crude enzyme of polyphenol oxidase was obtained from garlic. This enzyme actively oxidized triphenols such as pyrogallol and gallic acid, although it showed very weak activity on diphenols such as catechol and chlorogenic acid among the phenolic compounds tested. The optimum pH of the enzyme was 6.5 which was slightly higher than that of the garlic itself (pH 6.0). The enzyme was stable relatively at heat treatment. Sodium metabisulfite inhibited the enzyme activity at the concentration of 1mM, and KCN, L-ascorbic acid and thiourea also inhibited the enzyme action. $Mg^{++}$ activated the enzyme activity. $Cu^{++}$ activated slightly the enzyme action at low concentration (1mM), but inhibited at high concentration (10mM).

• Korean Journal of Materials Research
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• v.27 no.9
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• pp.489-494
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• 2017

ZnS powder was synthesized using a relatively facile and convenient glycothermal method at various reaction temperatures. ZnS was successfully synthesized at temperatures as low as $125^{\circ}C$ using zinc acetate and thiourea as raw materials, and diethylene glycol as the solvent. No mineralizers or precipitation processes were used in the fabrication, which suggests that the spherical ZnS powders were directly prepared in the glycothermal method. The phase composition, morphology, and optical properties of the prepared ZnS powders were characterized using XRD, FE-SEM, and UV-vis measurements. The prepared ZnS powders had a zinc blende structure and showed average primary particles with diameters of approximately 20~30 nm, calculated from the XRD peak width. All of the powders consisted of aggregated secondary powders with spherical morphology and a size of approximately $0.1{\sim}0.5{\mu}m$; these powders contained many small primary nanopowders. The as-prepared ZnS exhibited strong photo absorption in the UV region, and a red-shift in the optical absorption spectra due to the improvement in powder size and crystallinity with increasing reaction temperature. The effects of the reaction temperature on the photocatalytic properties of the ZnS powders were investigated. The photocatalytic properties of the as-synthesized ZnS powders were evaluated according to the removal degree of methyl orange (MO) under UV irradiation (${\lambda}=365nm$). It was found that the ZnS powder prepared at above $175^{\circ}C$ exhibited the highest photocatalytic degradation, with nearly 95 % of MO decomposed through the mediation of photo-generated hydroxyl radicals after irradiation for 60 min. These results suggest that the ZnS powders could potentially be applicable as photocatalysts for the efficient degradation of organic pollutants.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.30-30
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• 2018

스마트 도금공장을 구축하기 위해서는 도금액 내부의 화학 물질 농도 변화를 측정할 수 있는 화학 센서 기술이 필수적으로 요구된다. 와트욕은 대표적인 고속 니켈 도금액 중 하나로 기본적으로 황산니켈, 염화니켈, 보릭산의 염과 함께 케리어(type-1 광택제), 광택제(type 2-광택제), 응력 제어제 등의 유기 첨가제로 구성되어 있다. 이러한 유기 첨가제는 전차된 니켈층의 두께 균일도, 조도, 미세 구조, 내부 응력 등 다양한 특성을 제어하며, 정밀한 농도 관리가 필수적으로 요구되나, 분석 기술의 부재로 인하여 지금까지도 대부분의 액관리는 할셀법이나 작업자의 경험에 의존하고 있다. Cyclic voltammetry stripping(CVS) 방법은 전기화학 분석 과정에서 나타나는 첨가제의 가속, 감속 특성 등과 여기에 수반되는 stripping peak의 변화를 이용하여 개별 첨가제의 농도를 측정하는 방법이며, 지금까지 인쇄회로기판의 비아필 공정, 전해 동박 제조, 반도체 배선 등 구리도금 산업 전반에 걸쳐 첨가제 관리에 효과적으로 적용되고 있다. 그러나 수소 발생으로 인한 stripping 효율 문제로 인하여 니켈, 주석, 아연 등 표준 환원 전위가 높은 금속 도금액 내부 첨가제 농도 측정은 아직 어려운 상황이다. 본 연구에서는 이 문제를 극복하기 위해 염소를 과량 첨가한 구리 도금액을 CVS 분석의 base 용액으로 이용하여 니켈 도금액 내부 여러 광택제 (polyetylene glycol(PEG) 계열, thiourea 계열, 2-butyne-1,4-diol 등) 농도를 측정하는 법을 제시하였다. 제시된 방법은 CVS 분석 과정에서 구리-염소 사이의 상호 작용으로 인해 생성되는 3가지 stripping peak의 상대적인 크기 변화가 첨가제 농도에 따라 영향을 받는다는 사실에 기반하였다. 본 연구에서는 여기에 관한 원인에 대해 고찰하였으며, 제시된 방법을 통해 광택제 계열 첨가제 농도 측정을 선택적으로 할 수 있다는 것을 증명하였다.

• Bulletin of the Korean Chemical Society
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• v.30 no.10
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• pp.2227-2232
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• 2009

Novel polythiol materials of urethane lens series for plastic optical lens were synthesized from polyol materials via thioisouronium of thiourea with c-HCl in refluxing aqueous solution, in which polythiol material was carried out from hydrolysis of thioisouronium by ammonia water. Their structure properties were identified by EA, EI-MS, FT-IR, $^1H\;and\;^{13}C$ NMR spectroscopies and TGA. Their ophthalmic lenses as polythiourethane material were prepared by thermal curing to an injected glass mold using the evenly solutions of diisocyanates series (TDI, XDI, HDI or IPDI) with polythiols. Polythiourethane shows that the strong stretching mode for SH group of polythiol disappeared in FT-IR spectra after thermosetting polymerization. Thermal deformation starting temperature of ophthalmic lenses was determined by TMA. Ophthalmic lenses made from characteristic polythiol and diisocyanate series have transparency, colorless and good impact strength, in which thermal resistance and impact strength of ophthalmic lenses were influenced by diisocyanate series. Physical properties of ophthalmic lens have contrast thermal resistance with impact strength. The property of thermal resistance and impact strength for respective ophthalmic lenses was examined by TMA and drop ball test.

• Resources Recycling
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• v.25 no.5
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• pp.50-56
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• 2016

Extraction behaviour of silver from nitric acid solutions by Cyanex 301 as an extractant was examined. Detailed studies have been conducted to evaluate the effect of different variables influencing the extraction such as concentration of nitric acid and extractant, phase ratio(O/A) and synergism of mixed extractant. The extraction behaviour of associated metals namely Ca, Al, Fe, Zn and Sr has been investigated. The extraction results show that Ag can be extracted effectively by Cyanex 301 and selectively extracted from 3.0M $HNO_3$ using 5% Cyanex 301. Impurity metals loaded in organic phase can be effective scrubbed by 4.0M HCl. Finally, pure silver solution can be obtained efficiently by thiourea as a stripping reagent.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.805-808
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• 2010

In this paper, CdS thin films, which were widey used window layer of the CdS/CdTe and the CdS/$CuInSe_2$ heterojunction solar cell, were grown by chemical bath deposition, and effects of temperature of reaction solution on the structural properties were investigated. Cadmium acetate and thiourea were used as cadmium and sulfur source, respectively. And ammonium acetate was used as the buffer solution. The reaction velocity was increased with increasing temerature of reaction solution. For temperature <= $85^{\circ}C$, as increasing temperature of solution, deposition rate of CdS films was increased by ion-by-ion reaction in the substrate surface, and the crystallinity of the films was improved. However, for temperature <= $55^{\circ}C$, deposition rate was decreased resulting from smaller Cd2+ ion, and the grain size was decreased.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.309.2-309.2
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• 2013

Cu(In,Ga)Se2 (CIGS) 박막 태양전지는 일반적으로 Na을 함유하고 있는 소다회유리를 기판으로 사용하여 제작되며, 높은 광전 변환 효율로 인해 많은 연구가 이루어지고 있다. 특히 제조 비용 절감과 양산성 향상을 위해 현재 유연 기판 CIGS 박막 태양전지에 대한 연구가 활발히 이루어지고 있으며, 폴리이미드 기판에서 20.4%의 최고 효율이 보고되었다. 유연 기판은 유리 기판 대비 무게가 가볍기 때문에 유리 기판 태양전지보다 활용도가 높으며, 우주용으로 사용할 경우 단위 무게 당 발생되는 전력이 높은 장점이 있다. 본 연구에서는 폴리이미드 기판을 이용하여 유연 CIGS 박막 태양전지를 제작하였다. 후면 전극 Mo은 DC sputtering으로 증착하였으며, Mo의 증착 압력에 따라 폴리이미드 기판의 잔류 응력과 전기적 특성을 분석하여 증착 압력을 결정하였다. 광흡수층인 CIGS는 다단계 동시 증발 법으로 증착하였으며, 2nd stage 공정온도는 유리 기판 대비 저온인 $475^{\circ}C$로 공정을 진행하였다. 저온공정인 $475^{\circ}C$ 공정에서는 Ga의 함량이 높아질수록 성능이 감소하였으며, Na 공급을 통해 Voc와 FF가 향상되어 성능이 향상됨을 알 수 있었다. 버퍼층 CdS는 습식 공정인 CBD법으로 증착하였으며, 공정변수인 thiourea의 농도와 CdS 박막의 두께 변화를 통해 폴리이미드 기판 CIGS 박막 태양전지에서 CdS 버퍼층의 최적의 조건을 도출하였다. 최종적으로 제작된 폴리이미드 기판 유연 CIGS 박막 태양전지는 반사 방지막 없이 개방전압 0.511V, 단락전류밀도 32.31mA/cm2, 충실도 64.50%, 변환효율 10.65%를 나타내었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.298-299
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• 2010

Cu(In, Ga)Se2 (CIGS) 박막 태양전지는 Soda lime glass/Mo/CIGS/CdS/ZnO/ITO/Al 의 구조를 가지고 있다. CIGS 화합물은 direct bandgap 구조를 하고 있으며, 광흡수율이 다른 어떤 물질들 보다 뛰어나 박막으로도 충분히 태양광을 흡수할 수 있다. 또한 Ga의 도핑 농도에 따른 밴드갭 조절도 가능하다. 이러한 성질들로 인해 현재 박막태양전지로서 20.1%의 최고효율을 가지고 있다.[1] CIGS 박막 태양전지에서 p-CIGS layer와 스퍼터링으로 증착되는 n-ZnO layer사이의 buffer 층으로 chemical bath deposition (CBD)-CdS 박막을 주로 사용한다. CBD-CdS 박막은 n-ZnO 스퍼터로 증착 시킬 때, CIGS 층의 손상을 최소화하고, 이 두 층 사이에서의 격자상수와 밴드갭의 차이를 줄여주어 CIGS 박막태양전지의 효율을 증가 시키는 역할을 한다. 하지만, Cd (카드뮴)의 심각한 독성과 낮은 밴드갭(2.4eV)으로 인해 CIGS 층에서의 광흡수율을 줄여, CdS를 대체할 새로운 buffer 층의 필요성이 대두되었다.[2] 그 대안으로 ZnS, Zn(O, S, OH), (Zn, Mg)O, In2S3 같은 물질이 연구되고 있다. 현재 CBD-ZnS를 buffer 층으로 사용한 CIGS 박막태양전지의 효율은 최고 18.6%로 CBD-CdS의 최고효율보다는 약 1.5% 낮지만, ZnS가 높은 밴드갭(3.7~3.8eV)과 Cd-free 물질이라는 점에서 CdS를 대체할 물질로 각광받고 있다. 본 연구에서는 기존의 CdS 박막을 제조하는 방법과 같은 방법인 CBD를 이용하여 ZnS 박막을 제조하였다. ZnS 박막을 제조하기 위해서는 Zinc sulfate, Thiourea, 암모니아가 사용된다. 암모니아의 mol 농도에 따른 CBD-ZnS/CIGS 박막태양전지의 효율 변화를 관찰하기 위해 암모니아의 mol 농도는 1 mol, 2 mol, 3 mol, 4 mol, 5 mol, 6 mol, 그 이상의 과량을 사용하여 실험하였다. 실험 결과, 암모니아농도 5 mol에서 효율 13.82%를 확인할 수 있었다. 최고효율을 보인 조건인 암모니아 농도가 5 mol 일 때, Voc는 0.602V, Jsc는 33.109mA/cm2, FF는 69.4%를 나타내었다.

• Advances in environmental research
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• v.5 no.1
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• pp.1-18
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• 2016

Magnetic nano-based sorbents have been synthesized for the recovery of two rare earth elements (REE: Nd(III) and Yb(III)). The magnetic nano-based particles are synthesized by a one-pot hydrothermal procedure involving co-precipitation under thermal conditions of Fe(III) and Fe(II) salts in the presence of chitosan. The composite magnetic/chitosan material is crosslinked with epichlorohydrin and modified by grafting alanine and serine amine-acids. These materials are tested for the binding of Nd(III) (light REE) and Yb(III) (heavy REE) through the study of pH effect, sorption isotherms, uptake kinetics, metal desorption and sorbent recycling. Sorption isotherms are well fitted by the Langmuir equation: the maximum sorption capacities range between 9 and 18 mg REE $g^{-1}$ (at pH 5). The sorption mechanism is endothermic (positive value of ${\Delta}H^{\circ}$) and contributes to increase the randomness of the system (positive value of ${\Delta}S^{\circ}$). The fast uptake kinetics can be described by the pseudo-second order rate equation: the equilibrium is reached within 4 hours of contact. The sub-micron size of sorbent particles strongly reduces the contribution of resistance to intraparticle diffusion in the control of uptake kinetics. Metal desorption using acidified thiourea solutions allows maintaining sorption efficiency for at least four successive cycles with limited loss in sorption capacity.