• Journal of the Korean Chemical Society
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• v.37 no.5
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• pp.503-512
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• 1993

The purpose of this study was to investigate the retention behavior of phenols and to predict their retention in RPLC. The retention data of twenty-five phenols were measured on a $\mu-{Bondapak}\;C_{18}$ and a polymeric $C_{18}$ columns with methanol-water and acetonitrile-water as a mobile phase. From the observation of enthalpy-entropy compensation phenomenon, the following conclusions are drawn with regard to the retention mechanism: 1) the retention mechanism of nitrophenols in different from that of metheyl-and chlorophenols in both mobile phase; 2) in methanol-water mobile phase, the retention mechanism of methyl-and chlorophenols is consistent in the range of methanol-water composition; 3) on the other hand, in the case of acetonitrile-water mobile phase, the retention mechanism depends on the volume fraction of acetonitrile. It means that the retention mechanism can not be explained only by a simple interaction. Based on retention data as compared with two columns, it may be said that the hydrophobic interaction of phenols with polymeric $C_{18}$ column was greater than that with monomeric $C_{18}$ column. The equations for predicting the retention of phenols were derived by using hydrophobic substituent constant $(\pi)$ and the sum of Hammett's constant $(\sigma)$ and Taft's steric constant $(E_s)$.

• Journal of Adhesion and Interface
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• v.13 no.3
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• pp.131-136
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• 2012

In this study, commercial poly(vinyl alcohol) (PVA) film was dyed with reactive dichroic dyes under mild conditions using organic solvents in stead of strong basic aqueous solution. After drawing of 500% of this PVA film, the polarizing efficiency and the single piece transmittance were measured. The degree of saponification of the commercialized PVA film was determined by using NMR and FT-IR spectromety. The commercial PVA film, with ca. 100% of the degree of saponification determined by NMR spectrometry, was dyed with the reactive dichroic dyes, which have 3,5-dichloro-2,4,6-triazine moiety. As a result, we found that the PVA film dyed with the reactive congo red showed relatively good polarization efficiency, and the PVA film dyed with the reactive direct black 22 exhibited relatively good single piece transmittance.

• Journal of Marine Bioscience and Biotechnology
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• v.2 no.3
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• pp.174-186
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• 2007

Amphora coffeaeformis and Achnanthes longipes are commonly found as dominant benthic microalgae in Jeju coastal water throughout the year. In order to investigate pharmaceutical uses of these diatoms, each single species was isolated with micropipette under phase contrast microscope and subcultured with synthetic seawater media which was enriched with F/2 media, trace metal solution and $Na_2SiO_3$). Growth characteristics of these species were also determined with different combination of salinity, nutrients concentration and temperature. Thereafter, mass culture of each species was done based on the maximum growth condition. Biomass was collected after two weeks of mass culture and freeze dried for antioxidant study. The antioxidant properties of different fractions (n-hexane, chloroform and ethylacetate) obtained by solvent fractionation of 80% methanolic extract of two microalgae were investigated for free radical, reactive oxygen species scavenging (Super oxide, Hydrogen peroxide, Hydroxyl radical and Nitric oxide), metal chelating and lipid peroxidation inhibition activities. All fractions of A. longipes showed higher $DPPH^{\cdot}$ (free radical) scavenging activities (n-hexane: 89.0%, Chloroform: 76.0%, Ethylacetate: 66.0%, Methanol: 90.6% and aqueous residue: 63.0%). N-hexane fraction of A. longipes showed significantly higher activity (49.0%) on nitric-oxide. Ethylacetate fraction of A. longipes and aqueous residue of A. coffeaeformis exhibited 64.0% and 75.6% metal chelating activity which was higher than commercial antioxidants (${\alpha}$-tocopherol: 18.0% and BHT: 16.0%). The n-hexane fraction of A. coffeaeformis had 67.5% activity on $DPPH^{\cdot}$. Chloroform and n-hexane fractions of A. coffeaeformis exhibited 46.2% and 47.6% $H_2O_2$ scavenging effects which were closely similar to commercial antioxidants (${\alpha}$-tocopherol: 49.2% and BHT: 58.6%). Chloroform and ethylacetate fractions of A. longipes and fraction of n-hexane and chloroform of A. coffeaeformis showed better lipid peroxidation activities than ${\alpha}$-tocopherol. These data suggest that both organic and aqueous fractions have good antioxidative compounds with different antioxidant properties.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.7
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• pp.472-478
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• 2013

Cu and Cr as a base metal and Pt, Pd as a supportive metal were selected for improving adsorption capacity of activated carbon fiber in eliminating especially targeted VOCs. Preparing variables such as metal loading, loading temperature, loading hours and kinds of loaded metals were changed. Properties measurement was carried out by SEM (scanning electron microscope), XRF (x-ray fluorescence analysis) and EDX (Energy Dispersive X-ray spectrometer) and adsorption capacity evaluation were also performed by gas analyzer. Under this study, the adsorption capacity of complex metal loaded activated carbon fiber was improved positively than that of single metal loaded activated carbon fiber. And we found that the best conditions for metal loading were 5 hours loading time at $100^{\circ}C$ and the adsorption capacity was enhanced almost double compared with other condition based activated carbon fiber. Cu-Cr-Pt-Pd loaded activated carbon fiber showed the best adsorption capacity. Also we confirmed that more than 0.5 second is necessary for adsorbate diffusion and adsorption over activated carbon fiber.

• Membrane Journal
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• v.23 no.4
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• pp.257-266
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• 2013

The main purpose of this study is to develop a commercial scale of pervaporative process equipped with hollow fiber membrane modules, being able to effectually purify organic solvent at high temperature well over its boiling point under high vapor pressure. Three constituent technologies have been developed; 1) to fabricate braid-reinforced hollow fiber membrane stable in high pressure and high temperature application, 2) to design and fabricate a commercial scale of hollow fiber membrane module, and 3) to design and fabricate a pilot scale of pervaporation equipment system. The developed hollow fiber membrane possesses a membrane performance superior to the membrane of Sulzer (Germany) which is the most-well known for pervaporation process, and the membrane module equips hollow fiber membranes of $4.6m^2$ and the pervaporation system can treat organic liquid at 200 L/h, which is based on the dehydration of 95 wt% isopropyl alcohol (IPA). Since the membrane module is designed to flow in and pass through the inside of individual hollow fiber membrane, not to involve both the formation of feed's dead volume observed in flat-sheet membrane module and the channeling of feed occurring inside hollow fiber bundle which lower membrane performance seriously, it showed excellent separation efficiency. In particular, the module is inexpensive and has less heat loss into its surrounding, in compared with flat-sheet membrane module. In addition, permeant can be removed effectively from the outer surface of hollow fiber membrane because the applied vacuum is conveyed uniformly through space between fibers into respective fiber, even into one in the middle of the hollow fiber bundle in which the space between fibers is uniform in distance. Since the hollow fiber membrane pervaporation system is the first one ever developed in the world, our own unique proprietary technology can be secured, preoccupying technical superiority in export competitive challenges.

• Korean Chemical Engineering Research
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• v.55 no.5
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• pp.609-617
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• 2017

Lignocellulosic biomass is a renewable resource for production of biofuels and biochemicals. Furfural (FF) is an important platform chemical catalytically derived from the hemicellulose fraction of biomass. Tetrahydrofurfuryl alcohol (THFA) is a FF derivative and can be used as an eco-friendly solvent with thermal and chemical stability. Despite large numbers of experimental studies for catalytic conversion of FF to THFA, few research have conducted on the economic feasibility for large-scale THFA production from FF. At the stage of assessment of the potential for commercialization of conversion technology, a large-scale process study is required to identify technological bottleneck and to obtain information for solving scale-up problems. In this study, process simulation and technoeconomic evaluation for catalytic conversion of FF to THFA are performed, as the following three steps: integrated process design, heat integration, and economic evaluation. First, a large-scale process including conversion and separation processes is designed based on experimental results. When the FF processing rate is 255 tonnes per day, the FF-to-THFA yields are 63.2~67.9 mol%. After heat integration, the heating requirements are reduced by 14.4~16.4%. Finally, we analyze the cost drivers and calculate minimum selling price of THFA by economic evaluation. The minimum selling price of THFA for the developed process are $2,120~2,340 per tonne, which are close to the current THFA market price.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.255-255
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• 2016

Resistive random access memory (ReRAM)는 낮은 동작 전압, 빠른 동작 속도, 고집적화 등의 장점으로 인해 차세대 비휘발성 메모리 소자로써 많은 관심을 받고 있다. 최근에 ReRAM 절연막으로 NiOx, TiOx, AlOx TaOx, HfOx와 같은 binary metal oxide 물질들을 적용하는 연구가 활발히 진행되고 있다. 특히, HfOx는 안정적인 동작 특성을 나타낸다는 점에서 ReRAM 절연막 물질로 적합하다고 보고되고 있다. ReRAM 절연막을 형성할 때, 물리 기상 증착 방법 (PVD)이나 화학 기상 증착법 (CVD)과 같은 방법이 많이 이용된다. 이러한 증착 방법들은 고품질의 박막을 형성시킬 수 있는 장점이 있다. 하지만, 높은 온도에서의 공정과 고가의 진공 장비가 이용되기 때문에 경제적인 문제가 있으며, 기판 또는 금속에 플라즈마 손상으로 인한 문제가 발생할 수 있다. 따라서 이러한 문제점들을 개선하기 위해 용액 공정이 많은 관심을 받고 있다. 용액 공정은 공정과정이 간단할 뿐만 아니라 소자의 대면적화가 가능하고 공정온도가 낮으며 고가의 진공장비가 필요하지 않은 장점을 가진다. 따라서 본 연구에서는, 용액공정을 이용하여 HfOx 기반의 ReRAM 제작하였고 $25^{\circ}C$와 $85^{\circ}C$에서 ReRAM의 동작특성에 미치는 compliance current의 영향을 평가하였다. 실험 방법으로는, hafnium chloride (0.1 M)를 2-methoxyethanol에 충분히 용해시켜서 precursor를 제작하였다. 이후, p-type Si 기판 위에 습식산화를 통하여 300 nm 두께의 SiO2 절연층을 성장시킨 후, 하부전극을 형성하기 위해 electron beam evaporation을 이용하여 10/100 nm 두께의 Ti/Pt 전극을 증착하였다. 순차적으로, 제작된 산화물 precursor를 이용하여 Pt 위에 spin coating 방법으로 1000 rpm 10 초, 6000 rpm 30초의 조건으로 두께 35 nm의 HfOx 막을 증착하였다. 최종적으로, solvent 및 불순물을 제거하기 위해 $180^{\circ}C$의 온도에서 10 분 동안 열처리를 진행하였으며, 상부 전극을 형성하기 위해 electron beam evaporation을 이용하여 Ti와 Al을 각각 50 nm, 100 nm의 두께로 증착하였다. ReRAM 동작에서 compliance current가 미치는 영향을 평가하기 위하여 compliance current를 10mA에서 1mA까지 변화시키면서 측정한 결과, $25^{\circ}C$에서는 compliance current의 크기와 상관없이 일정한 메모리 윈도우와 우수한 endurance 특성을 얻는 것을 확인하였다. 한편, $85^{\circ}C$의 고온에서 측정한 경우에는 1mA의 compliance current를 적용하였을 때, $25^{\circ}C$에서 측정된 메모리 윈도우 크기를 비슷하게 유지하면서 더 우수한 endurance 특성을 얻는 것을 확인하였다. 결과적으로, 용액공정 방법으로 제작된 ReRAM을 측정하는데 있어서 compliance current를 줄이면 보다 우수한 endurance 특성을 얻을 수 있으며, ReRAM 소자의 전력소비감소에 효과적이라고 기대된다.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.42 no.4
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• pp.321-328
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• 2016

In this study, we investigated identification of anti-oxidative constituents from Ficus erecta var. sieboldii King (F. erecta) leaves. DPPH and $ABTS^+$ radical scavenging activities were screened for the ethanol extract and solvent fractions, and ethyl acetate fraction showed the most potent scavenging activities. Five constituents were isolated from the ethyl acetate fraction of F. erecta leaves; monoolein (1), oleic acid (2), lutein (3), afzelechin (4), catechin (5). The chemical structures of the isolated compounds were elucidated based on the spectroscopic data including NMR spectra, as well as comparison of the data to the literature values. As far as we know, all of the compounds 1 ~ 5 were isolated for the first time from this plant. Studies on DPPH and $ABTS^+$ radical scavenging activities were conducted for the isolated compounds. Among them, afzelechin (4) and catechin (5) showed strong DPPH and $ABTS^+$ radical scavenging activities, whose activities were comparable to a positive control vitamin C. Also, the content of catechin isolated from this plant was determined by HPLC and it was about 3.8 mg/g for the 70% ethanol extract and 20.8 mg/g for the ethyl acetate fraction. From these results, F. erecta leaves extract could be potentially applicable as anti-oxidant ingredients in cosmetic industries.

• Journal of the Korean Society of Food Science and Nutrition
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• v.31 no.5
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• pp.905-909
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• 2002

This study was peformed to determine the anticarcinogenic activity of the Solanum tuberosum Peel (SP) on several microorganisms and human cancer cell lines. Among the various solvent fractions of SP, the ethylether Partition layer (SPMEE) showed the strongest antimicrobial activity, ethylacetate partition layer (SPMEA) and butanol partition layer (SPMB) resulted in good antimicrobial activity. We also determined the effect of SP extract and fractions on cytotoxicity, and chemopreventive effect on human cancer cells. The experiment was conducted to determine cytotoxicity of SP partition layers on HepG2, HeLa and MCF-7 cells by MTT assay. Among the various partition layers of SP, SPMEE and SPW were showed the strongest cytotoxic effects on all cancer cell lines. The quinone reductase induced activities of HepG2 cell, the butanol partition layer (SPMB) at a does of 40 $\mu\textrm{g}$/mL was 8.49 times more effective compared to the control value of 1.0. This value was significantly higher than that of previous results using the other materials. Therefore, based on these studies, SP may be developed into a potentially useful antimicrobial and anticarcinogenic agents.

• Applied Chemistry for Engineering
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• v.29 no.3
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• pp.336-341
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• 2018

In general, the synthesis of poly(3-hexylthiophene)(P3HT)-based block copolymers requires at least a 4-5 step process. To control the molecular weight, molecular weight distribution, and block ratio, the reaction conversion and time should be monitored. In addition, the reaction scale usually limited to several mg to g was difficult to increase due to the limitations of living radical polymerizations. In this study, we synthesized P3HT-b-poly(4-vinylprydine) (P3HT-b-P4VP) with a final product quantity of > 19 g via a 2-step synthetic method with an anionic polymerization. In this method, the molecular weight and molecular weight distribution of P3HT-b-P4VP can be well controlled without monitoring the reaction conversion. We also studied physical properties of P3HT-b-P4VP depending on different solvent systems, which were investigated by UV-vis spectroscopy, atomic force microscopy, and ultraviolet photoelectron spectroscopy.