• Analytical Science and Technology
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• v.6 no.5
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• pp.479-487
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• 1993

Potassium-Graphite Fiber Intercalation Compounds(K-GFIC) have been prepared from well oriented pitch-based Graphite fiber by the transformed two-bulbs method with variation of reaction temperatures of graphite($T_g$ : $450^{\circ}C$, $400^{\circ}C$, $350^{\circ}C$, $300^{\circ}C$, $250^{\circ}C$). The stage transition process of K-GFICs was studied by X-ray diffraction methods, and we have observed peaks with d-values of (001) diffraction of $5.40{\AA}$ and $8.78({\pm}0.01){\AA}$, which are charecteristic for the stage 1 and stage 2, respectively. The stage stability and energy states of K-GFICs were studied by UV/VIS spectrophotometer. As a results, We found that the minimum values of reflactance of K-GFICs with pure stage was moved to higher energy pristine Graphite fiber's. But because of mixtured stage, we could not observe minimum reflectance in the visible region at high reaction temperatures($400^{\circ}C$, $450^{\circ}C$). From X-ray diffraction and UV/VIS sepctrophotometry data, we can suggest that K-GFICs with lower stage has many charge carriers existed between C atoms of graphite Layers. And then, these results also provides information on the electrical and other physical properties of K-GFICs.

• Journal of the Korean Chemical Society
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• v.58 no.6
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• pp.535-542
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• 2014

A simple and efficient preconcentration method was developed using three-phase liquid phase microextraction prior to HPLC-UV for simultaneous extraction and determination of tetracycline antibiotics (tetracycline, oxytetracycline, and chlortetracycline). The tetracycline antibiotics were separated simultaneously on a column ($C_8$, $3.0{\times}150mm$, $3{\mu}m$) with high selectivity and sensitivity using gradient elution. Under optimized conditions (extraction solvent, heptanal; pH of donor, 9.0; pH of acceptor, 1.0; stirring speed, 700 rpm; NaCl salt, 0%; and extraction time, 60 min), enrichment factors (EF) were between 5.6 and 22.3. The limit of detection (LOD) and limit of quantitation (LOQ) in the spiked urine matrix were in the concentration range of $0.08{\sim}0.8{\mu}g/mL$ and $0.4{\sim}1.6{\mu}g/mL$, respectively. The calibration curves were linear within the range of $0.1{\sim}32{\mu}g/mL$ with the square of the correlation coefficient being more than 0.995. The precision (as a relative standard deviation, RSD) and accuracy (as a relative recovery) within working range were 1.3~9.1% and 84~118%, respectively.

• Membrane Journal
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• v.20 no.1
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• pp.8-12
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• 2010

Poly(3,4-ethylenedioxythiophene) (PEDOT), which has the highest stability in conducting polymer was employed to electrochromic (EC) film and studied about electrochromic properties according to the film fabrication method. PEDOT films were coated by two different methods, electropolymerization (EP) and vapor phase polymerization (VPP). Both of PEDOT films showed dark blue color at dedoped neutral state. Spectroelectrochemistry, switching ability and stability of the devices were investigated by UV-Vis Spectrophotometer and Cyclic voltammetry. Surface morphologies of the PEDOT VPP film at oxidized and reduced state were obtained by AFM. The average surface roughness of the PEDOT-VPP film was 50 nm and more homogeneous than that of the PEDOT-EP. The EC property from the PEDOT-VPP film was improved compared to that of the PEDOT-EP film, to show a response time of 1.5 sec, transmittancechange of 49%, and coloration efficiency of 402.

• Applied Chemistry for Engineering
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• v.27 no.5
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• pp.483-489
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• 2016

Here, we examined the photo-degradation efficiency of $Cu_2Se$-graphene nanocomposites synthesized by a facile and fast microwave-assisted technique. The prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, XPS and UV-Vis spectrophotometry. The photocatalytic performance was studied through the decomposition of Rhodamine (Rh B) as a standard dye under visible light radiation. A 95% of Rh B degradation after visible light irradiation for 180 min indicates that the $Cu_2Se$-graphene composite exhibited significant photodegradation efficiency. Therefore, it can be concluded that the synthesized $Cu_2Se$-graphene can be used as a suitable catalyst for decomposing dye pollutants.

• Applied Chemistry for Engineering
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• v.28 no.5
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• pp.587-592
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• 2017

Uniform and optimum sized silver nanoplates were synthesized through the liquid phase reduction method by using silver nitrate solution as a starting chemical, dimethylformmide (DMF) as a reducing solvent, and polyvinylpyrrolidone (PVP) as reducing and surfactant agents. Synthesized and also film samples were characterized by using SEM, TEM, UV-Vis-NIR spectroscopy, particle size analyzer (PSA), and XRD. Triangle nanoplates with the size of 100~200 nm were found from the sample synthesized at $70^{\circ}C$ for 72 h using silver nitrate, DMF and 26 wt% PVP. The sample could reflect near-infrared light because it showed the maximum absorbing peak at about 1,000 nm. When the content or particle size of silver nanoplates increased in coating solutions, the transmittance decreased and the reflectance increased in film samples.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2009.11a
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• pp.21-22
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• 2009

최근, 헵타메틴 시아닌색소(heptamethinecyanine)는 그 적용 범위가 넓기 때문에 많은 연구자들의 관심을 받고 있다. 특히, photo-sensitizers, dye lasers, optical recordings와 storage media 등 다양한 분야에 적용이 가능하다. 헵타메틴 시아닌색소의 주된 특징은 polymethine 사슬에 연결된 cyclohexene 고리에 의하여 근적외선 부근에서 흡수가 이뤄진다는 것이다. 근적외선 색소의 흡수 특성을 HOMO와 LUMO 에너지 전위를 사용하여, 수치화 함으로써 분자간, 분자내 상호작용을 분석 할 수 있다. 따라서, 본 실험은 헵타메틴 시아닌 색소의 치환체에 따른 전기화학적 특성을 순환 전압-전류법(Cyclic voltammetry)과 분자 모델링을 통하여 HOMO와 LUMO의 에너지 준위를 구하고, 치환체 효과가 헵타메틴 시아닌색소에 미치는 전기화학적 특성을 UV-Vis와 계산으로부터 얻어진 에너지준위를 분석하고자 한다. 본 실험에 사용된 Uv-Vis 스펙트럼 측정은 Agilent 8453 UV-Vis spectrophotometer를 사용하였고, 전기화학적 분석 방법인 순환 전압-전류법은 Versa STAT 3 (Princeton allied research in USA)를 사용하였다. 순환전압-전류법의 측정은 Acetonitrile 용액에 $TBAPF_6$ (Tetrabutylammonium hexafluorophosphate)를 전해질로 하고, Ag/$Ag^+$을 기준전극으로 사용하여 주사 속도를 50mV/s로 하여 측정 하였다. 치환체에 의한 영향을 알아보기 위하여 분자구조 최적화 모델링을 사용하였다. 3차원 분자입체 특성 및 에너지 준위 상태는 Materials studio 4.2를 사용하여 특성을 예측 하였다. 본 연구에서는, 헵타메틴 시아닌 색소의 기본 골격에 각기 다른 치환체를 치환 시켜 치환체에 의한 영향을 전기화학적인 방법인 순환 전압-전류법(Cyclic voltammetry)와 분자 모델링 방법을 사용하여, HOMO와 LUMO에너지 준위 값을 구함으로써 치환체에 의한 영향을 알아보았다. 치환체로는 Dye 1과 Dye 2로 치환된 헵타메틴 시아닌 색소를 사용하였다. 이렇게 얻어진 HOMO/LUMO 에너지 준위 값으로부터 이온화 에너지($I_p$)와 전자 친화도($E_a$) 또한 구할 수 있는데, $I_p$와 $E_a$는 분자 오비탈과 전자전이에 관련된 값들이고, 이는 계산을 통하여 얻을 수 있다. 순환 전압-전류법의 계산 방법은 봉우리 전위(peak postential)와 (onset potential)방법이 있는데, 이 계산을 통한 전위 값들이 봉우리 전위 계산 방법이 onset potential 방법에 비하여 작은 전위 값으로 나타난다. 하지만 이 두 가지 방법 모두 현재 순환 전압-전류법을 사용하여 HOMO/LUMO 에너지 준위를 측정하는 방법에 쓰이고 있으며, 어떠한 계산 방법이 더 정확하다고는 말 할 수 없지만, 본 실험 결과를 통하여 비교 분석한 결과 onset potential 계산 방법이 봉우리 전위 계산 방법에 비하여 정확하다고 판단된다. Dye 1과 Dye 2를 순환 전압-전류법으로 측정한 결과 각기 다른 전위를 나타내고 이것을 계산을 통하여 정량화하면 Dye 2가 Dye 1에 비하여 높은 전위 값을 갖음을 알 수 있는데, 이것은 ethyl 에 비하여 surful 원자의 전자공여성이 더 크다고 할 수 있다.

• Journal of the Korean Chemical Society
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• v.54 no.5
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• pp.573-578
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• 2010

In this study, iron(III)-2,4-dihydroxysalophen chloride (Fe(2,4-DHSalophen)Cl), has been synthesized by combination of 2,4-dihydroxysalophen (2,4-DHSalophen) with $FeCl_2$ in a solvent system. This complex combination was characterized using UV-vis and IR spectroscopies. Subsequently, the interaction between native calf thymus deoxyribonucleic acid (ct-DNA) and Fe(2,4-DHSalophen)Cl, was investigated in 10 mM Tris/HCl buffer solution, pH 7.2, using UV-visible absorption and fluorescence spectroscopies, thermal denaturation technique and viscosity measurements. From spectrophotometric titration experiments, the binding constant of Fe(2,4-DHSalophen)Cl with ct-DNA was found to be $(1.6{\pm}0.2){\times}10^3\;M^{-1}$. The fluorescence study represents the quenching effect of Fe(2,4-DHSalophen)Cl on bound ethidium bromide to DNA. The quenching process obeys linear Stern-Volmer equation in extended range of Fe(2,4-DHSalophen)Cl concentration. Thermal denaturation experiments represent the increasing melting temperature of DNA (about $4.3^{\circ}C$) due to binding of Fe(2,4-DHSalophen)Cl. These results are consistent with a binding mode dominated by interactions with the groove of ct-DNA.

• Analytical Science and Technology
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• v.12 no.1
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• pp.84-88
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• 1999

A method to analyze additives in a polyester resin has been studied by utilizing a centrifuge and a thin layer chromatography. Identification of the separated organic and inorganic compounds were carried out by spectrophotometers, such as NMR, UV-VIS, IR and XRD. For the polyester resin studied in this research contained organic and inorganic compounds which were found to be a dimer form of 2-phenylbenzoazole and an anatase form of $TiO_2$, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.6
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• pp.267-271
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• 2010

Super hydrophilic and high transparent $TiO_2$ thin films were successfully fabricated by sol-gel method without an irradiation of UV light. In addition, surfactant Tween 80 was used for increasing the transmittance of the thin films. When the contents of Tween 80 in $TiO_2$ solution were 0.0, 1.0, 3.0, 5.0 wt%, the transmittance of $TiO_2$ thin films was ca. 74.31%, 74.25%, 79.69%, 81.99% at 550 nm wavelength, respectively. The contact angles of fabricated $TiO_2$ thin films with or without Tween 80 were from ca. $4.0^{\circ}$ to $4.5^{\circ}$. The $TiO_2$ thin films annealed over $400^{\circ}C$ showed anatase crystal structure and the photocatalytic property that decomposed methyl orange with UV irradiation. The surface morphologies, optical properties and contact angle of prepared thin films with different contents of Tween 80 were evaluated by field emission scanning electron microscope (FE-SEM), X-ray diffratometer (XRD), UV-Vis spectrophotometer and contact angle meter.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.4
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• pp.165-168
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• 2008

Ta-doped thin films were deposited on quartz and indium-tin oxide glass substrates using a co-sputtering method. The Ta-doped films formed a solid solution that induced structural changes from rutile to anatase phase. The anodic photocurrents of the Ta-doped $TiO_2$ electrodes were observed not only in UV but also in the visible light range. The photocurrent response in visible light on Ta-doped $TiO_2$ films are due to bandgap reduction.