• Journal of the Korean Vacuum Society
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• v.18 no.5
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• pp.358-364
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• 2009

We investigated the growth of ZnO thin films with prominent emission characteristics through minimizing the formation of defects by using pulsed laser deposition (PLD). To do so, the ZnO films were deposited on sapphire(0001) substrates at the substrate temperature of $400-850^{\circ}C$ and then the variation of their structural and optical properties were analyzed by x-ray diffraction, atomic force microscope and photoluminescence. As a result, all ZnO films were grown with c-axis preferential orientation irrespective of the substrate temperature. However, the crystallinity and stress state were dependent on the substrate temperature and the ZnO film deposited at $600^{\circ}C$ showed the best surface morphology and crystallinity with nearly no strain. And also this film exhibited outstanding emission characteristics from the viewpoint of full width half maximum of UV emission peak as well as visible emission due to defects. These results indicate that the emission characteristics of the ZnO films are strongly related to their structural characteristics influenced by substrate temperature. Consequently, ZnO films with strong UV emission and nearly no visible emission, which are applicable to UV emission devices, could be grown at the substrate temperature of $600^{\circ}C$ by PLD.

• Journal of Korean Society on Water Environment
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• v.23 no.5
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• pp.705-711
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• 2007

Green quantum-dot nanocrystal (QD525) with anti-microcystin monoclonal antibody was applied for detection of microcystin, a monocyclic peptide hepatotoxin, extracted from the culture of Microcystis aeruginosa. The presence of microcystin in the cell lysate was verified by HPLC analysis with UV absorbance at 238 nm. Microcystis cell extract exhibited fluorescence emission spectra, which peak was around 460 nm because of their complex organic substances. When a spherical QD525 antibody conjugates (10~20 nm in diameter) were bound to the microcystins in the Microcystis cell lysate, the fluorescence intensity of the primary peak at 525 nm diminished while the secondary emission peak at 460 nm slightly increased intensities. It is due to energy transfer from the primary (major) to the secondary (minor) peak, resulting from physical deformation of QD525 and different environmental factors. On the other hand, other cell extracts did not show any fluorescence emission change. This study is very available for detecting and monitoring the microcystin because it is one step assay without washing step and portable spectrophotometer makes on-site measurement possible. For health risk assessment of the microcystin, the reliable and rapid system to detect and quantify microcystin is seriously required.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.346-346
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• 2012

We investigated electrical and optical properties and chemical states of amorphous In-Ga-Zn-O (a-IGZO) thin films deposited at different substrate temperatures (from room temperature to $300^{\circ}C$). a-IGZO thin films were fabricated by radio frequency magnetron sputtering using $In_2O_3$ : $Ga_2O_3$ : ZnO = 1 : 1 : 1 target, and their electrical and optical properties and chemical states were investigated by Hall-measurement, UV-visible spectroscopy and x-ray photoelectron spectroscopy (XPS), respectively. The data showed that as substrate temperature increased, carrier concentration increased, but mobility, conductivity, transmittance in the shorter wavelength region (>350 nm), and the Tauc-plot-estimated optical bandgap decreased. XPS data indicated that the intensity of In 3d peak compared to Ga 3d peak increased but the intensity of Zn 3d peak compared to Ga 3d decreased, and that, from the deconvoluted O 1s peak, defects or oxygen vacancies and non-quaternary contents increased as the temperature increased. The relative intensity changes of the In, Zn, and O 1s sub-component are suggested to explain the changes in electrical and optical properties.

• KSBB Journal
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• v.26 no.5
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• pp.471-476
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• 2011

Nowadays biodiesel (fatty acid methyl ester, FAME) has been becoming an important issue as a desired alternative of energy products because of non-toxic, biodegradable properties, and lower exhaust emissions. During esterification of fatty acids or transesterification of oils and fats with short chain alcohols by the alkali-catalyzed methanolysis, FAME and unrefined glycerol are generated. Quantification of glycerol as a by-product is important because of a determinant of biodiesel quality. However, the glycerol analysis by gas chromatography (GC) method has laborious works with sample preparation, long time and cost of sample analysis. Thus, there is a need to analyze glycerol more simply. Herein we demonstrate that the colorimetric assay for glycerol analysis conducted by UV-vis spectrophotometer at the wavelength 617 nm whose peak is maximum intensity of malachite green, resulting in the red-shift occurred proportionally as a function of glycerol amount. Thus, it is considered the solvent media for malachite green fading for biodiesel production: (1) water, (2) MeOH, and (3) EtOH. The resulting findings show that the peak intensity at 617 nm in glycerol-malachite green mixture had a relationship between glycerol concentration and degree of peak shift as increase in pure glycerol concentration approximately at pH 7.0. However, when it was measured the unrefined glycerol concentration by diluting and adjusting with water to buffer (pH 7.0), it was not observed the absorption peak at 617 nm because of impurities and OH ions. In case of glycerol from biodiesel production factories, glycerol concentration could be successfully measured.

• Korean Chemical Engineering Research
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• v.54 no.1
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• pp.75-80
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• 2016

Biologically stabilized gold nanoparticles were synthesized from the flower aqueous extract of T. divaricata. The synthesized nanoparticles were characterized by UV-Vis spectrophotometer, Zeta sizer, FTIR and TEM analysis. T. divaricata reduced gold nanoparticles having particle size and potential of 106.532 nm and -10.2 mV, respectively, with a characteristic peak of 550 nm in UV-visible spectrophotometer. FTIR graph after comparison between the crude flower extract and gold nanoparticles showed three major shifts in the functional groups. The morphology and size of the gold nanoparticles were examined by HRTEM analysis, which showed that most of the nanoparticles were nearly spherical with size of 100 nm. The gold nanoparticles synthesized demonstrated potent anticancer activity against MCF-7 cell line. The findings conclude that the antioxidant molecule present in T. divaricata may be responsible for both reduction and capping of gold nanoparticles which possess potential applications in medicine and pharmaceutical fields.

• Advances in nano research
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• v.1 no.2
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• pp.83-91
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• 2013

The synthesis of semiconductor nanoparticles is a growing research area due to the prospective applications for the development of novel technologies. In this paper we have reported the biosynthesis of Cadmium sulfide nanoparticles (CdSNPs) by reduction of cadmium sulphate solution, using the bacteria of Serratia nematodiphila. The process for the synthesis of CdS nanoparticles is fast, novel and ecofriently. Formation of the CdS nanoparticles was confirmed by surface Plasmon spectra using UV-Vis spectrophotometer and absorbance strong peak at 420 nm. The morphology of crystalline phase of nanoparticles was determined from Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy and X-ray diffraction (XRD) spectra. The average size of CdS nanoparticles was in the range of 12 nm and the observed morphology was spherical. The results indicated that the proteins, which contain amine groups, played a reducing and controlling responsibility during the formation of CdS nanoparticles in the colloidal solution. Antibacterial activity against some bacteria such as Bacillus subtilis, Klebsiella planticola. CdS nanoparticles exhibiting good bactericidal activity.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.51.1-51.1
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• 2010

이번 연구에서는 저온 용액공정을 이용하여p-type 반도체로 많이 사용되고 있는 $Cu_xS$를 기판 위에 증착하여 그 특성을 분석하였다. $Cu_xS$는 x의 값에 따라 다섯가지의 결정구조를 가지는데 CuS, $Cu_{1.75}S$, $Cu_{1.8}S$, $Cu_{1.95}S$, $Cu_2S$ 들이 그것이다. 태양전지에서 p형 반도체로 중요한 역할을 담당하고 있는 $Cu_xS$는 cell에서 사용되었을 때 energy bandgap이 1.2-2.5eV일 때 가장 좋은 특성을 나타낸다. 이번 연구에서는 특히 조성에 따라서 물리적, 광학적으로 어떤 특성을 나타내는지에 대하여 XRD, SEM, Uv-vis 등의 분석을 해보았다. XRD의 경우 농도가 높아질수록 peak의 intensity는 커지지만 어느 농도 이상부터는 Cu가 Oxide화 되는 것을 관찰할 수 있었다. SEM image의 경우에는 조성에 따른 포면의 상태를 분석해보았다. 조성에 따른energy bandgap을 알아보기 위해서는 Uv-vis을 측정하였으며 이를 이용하여 증착된 박막의 투과도 역시 함께 분석해보았다.

• Journal of the Korean Ceramic Society
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• v.34 no.9
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• pp.993-1001
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• 1997

The (0.8PPV+0.2DMPPV) copolymer and silica/borosilicate composites were synthesized by sol-gel process. The organic-inorganic hybrid solution was prepared by using of (0.8PPV+0.2DMPPV) copolymer precursor solution as a raw material for organic components and TEOS and TMB for glass components. Then by drying the solution in vacuum at 5$0^{\circ}C$ for 7days and subsequent heat treatment in vacuum at 15$0^{\circ}C$~30$0^{\circ}C$ for 2h~72h with heating rate of 0.2$^{\circ}C$/min and 1.8$^{\circ}C$/min, the organic-inorganic composites were synthesized. Microstructural evolution of the composites was characterized by DSC, IR spectrocopy, UV/VIS spectroscopy, and TEM. Elimination of the polymer precursor and degradation of the polymer were observed by DSC and Si-O and trans C=C absorption peaks were identified by IR spectra. The polymer was found to be successfully incorporated into the glass matrix and it was confirmed by the absorption peaks from the polymer in the UV/VIS spectra and the TEM results. The absorption peak of the composites was found to shift toward short wavelength side compared to that of the pure polymer and the amount of the blue shift increased with increasing the heat treatment temperature and heat treatment time and with decreasing the heating rate.

• Journal of the Korean Electrochemical Society
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• v.7 no.3
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• pp.138-142
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• 2004

The polyaniline films of emeraldine base (EB) and leucoemeraldine base (LEB) form doped with cam-phorsulfonic acid (CSA) were prepared by casting the mixed solution of chloroform and m-cresol on ITO (indium tin oxide) electrode. By analyzing UV-vis spectra of the mixed solutions, the effects of the secondary doping by m-cresol were obtained. And the conductivity of polyaniline film was increased with increasing m-cresol content. As the results of analyzing cyclic voltammograms, it was known that the redox peak currents of polyaniline electrode prepared from LEB were larger and more reversible than those of polyaniline eleclrodes prepared from EB. The charge transfer resistances $(R_{ct})$ of polyaniline electrodes were reduced with increasing m-cresol content, showing smaller Rct for LEB/CSA than EB/CSA.

• Fashion & Textile Research Journal
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• v.8 no.4
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• pp.465-470
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• 2006

Walnut hull is a by-product from the Walnut tree, used as natural dyestuff from ancient times. This study was done to examine the effects of extractive conditions on the properties of walnut hull extracts for making efficient use of the walnut hull as a natural colorant. Aqueous extracts of walnut hull were prepared at various extractive concentration, temperature and time. Then they were characterized using UV-Vis. Spectrophotometer, FT-IR Spectrometer, Prep Liquid Chromatography, and Energy dispersive X-ray spectrometer. The aqueous extracts have two absorbency peaks of UV-Vis. Spectrum, shoulder type peak in the range of 270-280 nm and broad type band around 420 nm. Intensity of absorbency is increased with increase of extraction concentration and time. However, Boiling temperature extraction method showed the most efficiency of all. Intensity of absorbency is also affected by extraction pH. The Prep LC examined two kinds of isolated colorant with different molecular weight. FT-IR spectra of hull extracts showed an absorption band around $3400cm^{-1}$, the peaks at $1700-1600cm^{-1}$, which are characteristic of aromatic compounds with unsaturated ketone and benzene ring. It showed that the extraction contained some mineral ions, such as K, Ca, Si, Mg.