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        검색결과 38

        2.
        2023.12 구독 인증기관 무료, 개인회원 유료
        최근 여러 연구에서 Hg2+에 선택적으로 반응해 형광을 강화시키거나 소광시키는 thiophene을 기반으로한 probe가 많이 개발되어 왔지만, 이에 따른 분광학적 현상에 대한 정확한 분자적 수준의 이론적 해석이 이루어지지 않 았다. 이에 따라 우리는 Hg2+와 thiophene간 상호작용을 면밀히 분석하기 위해 Hg2+와 thiophene간 거리에 따른 에너 지 포텐셜을 구하였다. Hg2+ 이온에 대한 모든 전자(all electron, AE) basis set인 x2c-TZVPPall와 effective core potential (ECP) 기반인 LANL2DZ는 모두 상대성 효과가 고려된 바닥 상태에서 Hg2+와 thiophene이 결합력이 없이 해 리가 되는 에너지 포텐셜을 보여주었지만, 용매인 물이 고려된 시스템에서는 Hg2+와 thiophene이 결합력을 가지는 것 을 보였으며 이것은 실험적인 결과를 잘 재현하는 것이었다. 따라서 Hg2+ 이온을 포함하는 착화합물 시스템에서 올바 른 에너지 상태를 구하기 위해서는 상대성효과와 더불어 solvent 영향도 잘 고려돼야 함을 알 수 있다.
        4,000원
        4.
        2022.10 구독 인증기관·개인회원 무료
        Ag-containing aluminosilicate sorbents capable of capturing iodine were prepared by sol-gelation from Na, Al, and Si alkoxides using co-solvent exchange, Ag/Na ion exchange, solvent exchange, and ambient-pressure drying. The Na+AlSi-OH gel was prepared using sodium methoxide (NaOMe): aluminum tri-sec-butoxide (Al(OsBu)3): tetraethyl orthosilicate (TEOS) molar ratios of 1.05:1:1, 1.3:1.1:1, 1.5:1.3:1. The solvent effect on textural properties such as Brunauer-Emmett-Teller (BET) surface areas and pore size distributions and Ag0 particle sizes was investigated using water with high surface tension, isopropanol and n-heptane with low surface tension. The BET surface area, average pore size, and cumulative pore volume for sorbents strongly increased with decreasing surface tension of solvents and increasing Al/Si atomic ratios. In addition, Ag0 particle sizes increased with decreasing surface tension of solvents.
        5.
        2021.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Carbon xerogels (CXs) with three-dimensional (3D) structure, unusual surface, physical, electrical and mechanical properties and their electrically conductive polymer polypyrrole (PPy) composites were synthesized as electrode materials for supercapacitors. The effect of different resorcinol/formaldehyde (R/C) ratios, whether solvent exchange with or without acetone and polypyrrole addition on the physicochemical (FTIR, XRD, BET, SEM and TGA) and electrochemical properties (CV, 1000 cycles) of the synthesized materials were investigated. It was observed that the R/C ratio and the solvent exchange process prior to drying affect the specific surface areas and the pore size distributions, thereby positively affecting the specific capacitance. PPy film thickness was observed to be effective in the specific capacitance of the electrode in PPy composite synthesis. Among the synthesized materials, the highest specific capacitance values belong to polypyrrole/carbon xerogel composites. As a result of the analysis and calculations, it was found that the highest specific capacitance belongs to CX2/PPy composite with 599 Fg− 1 at 5 mVs− 1. CX2/PPy composite has been found to have a capacitance retention rate of 80.30% at the end of 1000 cycles.
        5,800원
        7.
        2020.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        한국 자생식물인 기린초(Sedum kamtschaticum Fisch.)는 열수 추출 형태로 혈액 순환 개선과 항산화 및 항염증 효과를 내는 한약재로 사용되어왔다. 선행연구를 통해 기린초 여러 부위에서 우수한 항산화 효과를 확인하여, 본 연구에서는 기린초의 줄기(Stem)와 뿌리(Root) 부위를 각각 70% ethanol (SKS, SKR)로 추출한 후, n-hexane (SSH), ethyl acetate (SSE, SRE), chloroform (SSC, SRC) 및 water (SSW, SRW) 순서로 용매 극성별로 분획하여 화장품 소재로서 응용 가능성을 확인하였다. 각 분획물마다 총 폴리페놀 함량, 플라보노이드 함량 및 DPPH 라디칼 소거능을 확인한 결과 뿌리추출물(SKR)이 줄기추출물 (SKS)보다 우수한 함량과 효과를 나타냈고, 전체적으로 ethyl acetate 분획물(SSE, SRE)이 가장 효과가 우수했다. 또한, tyrosinase 활성 저해 효과도 ethyl acetate 분획물이 가장 우수하였고, 모든 분획물은 세포독성이 없는 10 μg/mL 농도에서 B16F10 멜라노마 세포에 처리했을 때 우수한 멜라닌 생성 저해력을 보였다. 70% ethanol 추출물(SKS, SKR)에 대해 HPLC 분석 시 gallic acid와 quercetin을 포함한 플라보노이드가 검출되었다. 본 연구에서는 기린초의 피부 항산화 효과와 미백효과를 나타내는 기능성화장품 천연소재로서 응용 가능성을 제시한다.
        4,000원
        9.
        2018.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Raphiolepis indica (R. indica) is one of evergreen shrubs belonging to the Rosaceae and is grown wildly in Jeju. This study was performed to evaluate the hepatoprotective effect of different fractions (n-hexane, dichloromethane, ethyl acetate, butanol, water) from R. indica. Anti-oxidative effects were determined using 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity and total phenol contents. Hepatoprotective effect was identified by 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide (MTT) assay in Huh7 cells. Among various fractions, ethyl acetate and butanol fractions showed the lowest DPPH remained rate reaching approximately 78.7 and 65.5% at 400 μg/mL. Ethyl acetate and butanol fractions showed the total phenolic content at 164.5 and 137.3 mg GAE/g extract. The ethyl acetate and butanol fractions were resistant against oxidative stress in MTT assay and showed higher hepatoprotective effect than other fractions. Therefore, these results suggest that the ethyl acetate and butanol fractions of R. indica might have therapeutic value in liver damage.
        4,000원
        10.
        2017.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Spherical-type zirconia granules are successfully fabricated by a spray-drying process using a water solvent slurry, and the change in the green density of the granule powder compacts is examined according to the organic polymers used. Two organic binders, polyvinyl alcohol (PVA) and 2-hydroxyethyl methacrylate (HEMA), which are dissolved in a water solvent and have different degrees of polymerization, are applied to the slurry with a plasticizer (polyethylene glycol). The granules employing a binder with a higher degree of polymerization (PVA) are not broken under a uniaxial press; consequently, they exhibit a poor green density of 2.4 g/cm3. In contrast, the granule powder compacts employing a binder with a lower degree of polymerization (HEMA) show a higher density of 2.6 g/cm3 with an increase in plasticizer content. The packing behavior of the granule powders for each organic polymer system is studied by examining the microstructure of the fracture surface at different applied pressures.
        4,000원
        11.
        2017.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Antioxidant activities of 80% methanol, water, and 70% ethanol extracts of Lentinula edodes GNA01 were compared and estimated. The yield of Lentinula edodes GNA01 was identified to be in the following order: water>70% ethanol>80% methanol, but there was no significant difference between 80% methanol and 70% ethanol extracts. The highest total phenolic content (TPC) and total flavonoid content (TFC) were found in water extract, and TPC of 80% methanol extract was higher than that of 70% ethanol extract and TFC of 70% ethanol extract was higher than that of 80% methanol extract. Water extract exhibited the strongest DPPH, ABTS radicals, and nitrite scavenging activities, Fe2+ chelating ability, and FRAP among the three extracts. In addition, antioxidant activity of 80% methanol extract was higher than that of 70% ethanol extract in most of the experiments. As a result, antioxidant activity of Lentinula edodes GNA01 showed a difference according to extraction solvent and concentration; nevertheless, water extract exhibiting high polarity had the strongest antioxidant effect. Consequently, water extract from Lentinula edodes GNA01 is anticipated to be useful for the development of a high value-added functional product
        4,000원
        12.
        2016.11 구독 인증기관·개인회원 무료
        The hollow fiber membranes were prepared via hybrid process of the thermally induced phase separation(TIPS) and the non-solvent induced phase separation(NIPS). The spinning dope solution consisted of poly(vinylidene fluoride) (PVDF) / dibutyl phthalate (DBP) / 1-methyl-2-pyrrolidone (NMP), where DBP was used as a diluent and NMP as a solvent for PVDF. Various bore fluids were tested different ratio solvent/diluent mixture. Depending on the miscibility of dope solution and internal coagulant the samples underwent the different phase separation mechanisms and rates. Phase separation mechanism study for various combinations were performed to support the interpretation of the membrane structure. Membrane characterizations were performed such as water flux, porosity, pore size, and mechanical strength.
        13.
        2016.11 구독 인증기관·개인회원 무료
        Perfluorinated sulfonic acid (PFSA) ionomers such as Nafion® and 3M ionomers have been used as polymer electrolyte membrane materials for fuel cells owing to their excellent chemical inertness, and high proton conductivity. The membrane characteristics are highly affected by their fabrication history as well as chemical structure. It is important to choose appropriate solvents for membrane preparation, since a relatively low solubility of PFSA ionomers may result in fairly different morphological features, which influence the transport behavior of small molecules such as proton and water through the resulting membranes. In this study, PFSA membranes are prepared using a variety of solvents with different properties and their fundamental characteristics and morphologies are compared each other.
        14.
        2016.05 구독 인증기관·개인회원 무료
        The hollow fiber membranes were prepared via hybrid process of the thermally induced phase separation(TIPS) and the non-solvent induced phase separation(NIPS). The spinning dope solution consisted of poly(vinylidene fluoride) (PVDF) / dibutyl phthalate (DBP) / 1-methyl-2-pyrrolidone (NMP), where DBP was used as a diluent and NMP as a solvent for PVDF. Bore fluids were tested different ratio solvent/ethanol and diluent/ethanol mixture. The membrane structure was analyzed by SEM and FT-IR to confirm phase separation mechanisms. Various structures were obtained due to the different phase separation mechanism. Membrane characterizations were performed such as water flux, pore size, rejection efficiencies and mechanical strength.
        15.
        2016.04 구독 인증기관·개인회원 무료
        Lycopene, one of the major carotenoids in human diet, has been suggested as a healthful phytochemical compound. Recently, it is important to quantify lycopene content in the lycopene-containing foods. However, it has been difficult to analyze lycopene content in the lycopene-containing foods using a HPLC because lycopene is not fully extracted during sample pretreatment resulting in less reliable quantitative data. The aim of this study was to investigate the effect of solvent on lycopene extraction from lycopene-containing foods for HPLC quantitative analysis. Two different solvents such as 100% acetone and methanol/acetone (1:1) mixture were used to extract lycopenefrom a commercial lycopene-enriched tomato concentrate (containing approximate 72 mg/g lycopene). All extracted samples were sonicated for 10 min, centrifuged, and filtered before injection into HPLC. The analysis of lycopene content was performed by an Ultimate3000 series HPLC system using a Unisol C18 column on UV detector at 450 nm. When the lycopene-enriched tomato concentrate was extracted using 100% acetone and methanol/acetone mixture for HPLC analysis, the lycopene contents were 75.88 and 39.84 (mg/g), respectively. As a result of quantitative analysis, acetone was able to extract lycopene fully from the lycopene-containing foods. The HPLC method established in this study might be useful to quantify lycopene in the lycopene-containing foods which are manufactured in various typessuchasbeverage, powder, tablet, and etc
        16.
        2015.11 구독 인증기관·개인회원 무료
        금속 유기 골격체(Metal Organic Framework, 이하 MOF) 종류의 하나인 제올라이트형 이미 다졸레이트 골격체(Zeolitic Imidazolate Framework, 이하 ZIF) 중 ZIF-8은 Zn 금속이온과 imidazole 유기 리간드의 결합으로 이루어져 있다. 본 연구에서는 여러 종류의 용매에서 합성된 ZIF-8의 1차 결정과 2차 입자의 형성이 용매가 가진 특성에 영향을 받는 것을 확인하였다. HBD(hydrogen bond donation) 값이 큰 용매에서 합성된 ZIF-8의 1차 결정은 HBD 값이 작은 용매에서의 것보다 크기가 컸고, 용매의 유전상수의 값이 작을수록 2차 입자의 크기가 큰 ZIF-8이 합성되었다.
        18.
        2015.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        용매추출법에서 희토류 금속을 효과적으로 분리하기 위해 추출제만 사용하는 것이 아니라 crown ether와 같은 첨가제를 이용하는 연구를 하였다. Host-guest 화합물인 macrocyclic ligand는 금 속과 착화물을 형성하는데, 이 때 crown ether의 cavity 크기와 비슷한 크기의 금속 이온들과 안정한 착 화물을 형성한다. 이전 연구에서 europium과 yttrium을 분리하기 위해 여러 사슬 길이의 지방산 추출제 를 이용한 추출실험을 행하였었다. 이를 토대로 분리효율이 좋지 않았던 hexanoic acid에 크기가 다른 crown ether (18-crown-6 ether, 15-crown-5 ether, 12-crown-4 ether)를 첨가하여 분리효과가 증가 하는 것을 연구하였다. hexanoic acid의 농도별로 분리효율을 본 후 가장 분리 효율이 좋은 농도에서 crown ether를 종류와 농도를 다르게 하여 첨가하였다. 그 결과 0.05 M hexanoic acid에서 분리능이 1.72으로 가장 높게 나타났고, crown ether를 첨가하였을 시 분리능이 0.002 M 15-crown-5 ether에서 가장 높게 나왔으며 기존의 분리능보다 2배 이상 더 높았다. 또한 crown ether를 첨가하였을 때 두 금 속이 MLR3·3RH의 형태로 추출되는 것도 확인 할 수 있었다.
        4,000원
        19.
        2014.12 구독 인증기관 무료, 개인회원 유료
        유기태양전지의 투명전극으로서 기존의 값비싸고 깨지기 쉬운 Indium Tin Oxide (ITO) 전극을 대체하고자, 전도성 고분자인 poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)를 적용하였다. 솔벤트의 도핑 농도에 따른 PEDOT:PSS 박막의 전기 전도도와 표면 거칠기의 특성 변화를 관찰하고, 그 결과가 PEDOT:PSS를 투명전극으로 사용한 유기태양전지의 특성에 미치는 영향을 연구하였다. PEDOT:PSS의 솔벤트 농도가 증가함에 따라, 박막의 표면 거칠기가 증가하고, 이는 유기태양전지의 단락전류의 변화를 야기했다. 또한, 소자의 홀 이동층이 얇아짐에 따라 광활성층의 단파장영역의 광흡수가 증가하는 것을 관찰할 수 있었다.
        4,000원
        20.
        2013.03 구독 인증기관 무료, 개인회원 유료
        To investigate the effects of co-solvents on the morphology of nano-scale zein materials, zein solutions were electrospun with different co-solvent ratios of EtOH/H2O. Different zein solution concentrations were used to study the effects of the zein content on the electrospun materials. The resulting electrospun materials were all characterized using field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The diameters of the electrospun nanoparticles and nanofibers were found to increase when increasing the EtOH ratio at certain zein concentrations. Furthermore, increasing the zein content changed the morphology of the electrospun materials from nanoparticles to nanofibers.
        4,000원
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