• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1181-1187
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• 2013

Water-dispersible ZnS:Mn nanocrystals were synthesized by capping the surface of the nanocrystal with O-(2-Aminoethyl)polyethylene glycol (PEG-$NH_2$, Mw = 10,000 g/mol) and O-(2-Carboxyethyl)polyethylene glycol (PEG-COOH, Mw = 10,000 g/mol) molecules. The modified PEG capped ZnS:Mn nanocrystal powders were thoroughly characterized by XRD, HR-TEM, EDXS, ICP-AES and FT-IR spectroscopy. The optical properties were also measured by UV/Vis and photoluminescence (PL) spectroscopies. The PL spectra showed broad emission peaks at 600 nm with similar PL efficiencies of 7.68% (ZnS:Mn-PEG-NH2) and 9.18% (ZnS:Mn-PEG-COOH) respectively. The measured average particle sizes for the modified PEG capped ZnS:Mn nanocrystals by HR-TEM images were 5.6 nm (ZnS:Mn-PEG-NH2) and 6.4 nm (ZnS:Mn-PEG-COOH), which were also supported by Debye-Scherrer calculations. In addition, biological toxicity effects of the nanocrystals over the growth of wild type E. coli were investigated. They showed no biological toxicity to E. coli until very high concentration dosage of 1 mg/mL of the both nanocrystal samples.

• Korean Journal of Materials Research
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• v.15 no.8
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• pp.543-547
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• 2005

Organic electroluminescence devices were made from 1,4-bis-(9-anthrylvinyl)benzene (AVB) and 1,4-bis-(9-aminoanthryl)benzene (AAB) anthracene derivatives. Device structure was ITO/AVB/PANI(EB)/Al (multi-layer device) and ITO/AAB:DCM/Al(single-layer device). In these devices, AVB, polyaniline(emeraldine base) (PANI(EB)) and AAB were used as the emitting material. 4-(dicyanomethylene)-2-methyl-6-p-(dimethylamino)styryl-4H -pyran(DCM) was used as red fluorescent dopant. We studied change of fluorescence wavelength with concentration of DCM doped in AAB. The ionization potential (IP) and optical band gap (Eg) were measured by cyclic voltammetry and UV-visible spectrum. We compared with difference of emitting wavelength between photoluminescence and electroluminescence spectrum. In case of the multi-layer device, PANI and AVB EL spectra have similar wave pattern to each PL spectrum and when PAM and AVB were used at the same time, and multi-layer device showed that a balanced recombination and radiation kom PANI and AVB. In case of the single-layer device, with the increase of DCM concentration, the blue emission decreases and red emission increases. This indicates that DCM was excited by the energy transfer from AAB to DCM or the direct recombination at the dopant sites due to carrier trapping, or both. The device with $1.0wt\%$ DCM concentration gave white light.

• The Korean Journal of Mycology
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• v.14 no.1
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• pp.61-70
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• 1986

Sterigmatocystin bears a close structural relationship to aflatoxin $B_1$ and is a carcinogenic compound that has been shown to affect various species of experimental animals. Reaction and toxicity of sterigmatocystin in the artificial gastric juice were investigated. Sterigmatocystin was degraded in artificial gastric juice and extracted by the method of A.O.A.C. After cleaned up by silica gel column chromatography, this substance was detected and characterized by thin layer chromatography, UV, IR and mass spectra. It showed $R{\mathcal{f}}$ 0.4 and brick-red color by TLC. Especially, in the mass spectrum of it, fragment peak at m/e 327 was due to the loss of the $-CH_3$ and $-H_2O$, fragment peak at m/e 341 was due to the loss of the $H_2O$ and $-H^+$, and fragment peak at m/e 239 was due to the loss of the 2-chloro-tetrahydrofuran and methyl group from the parent molecule. Therefore, a degraded substance of sterigmatocystin reacted in artificial gastric juice (Sub. K) was estimated with additional formation of hydrochloric acid. In four-day-old chicken embryos, the mean lethal dose $(LD_{50})$ was $140\;{\mu}g/egg$, and 90 to 100% of the embryos were killed with 1 mg/egg. This $LD_{50}$ $140\;{\mu}g/egg$ compared with an $LD_{50}$ $14.69\;{\mu}g/egg$ for sterigmatocystin (acute toxicity) showed the substance to be much less toxic than sterigmatocystin.

• Korean Journal of Materials Research
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• v.27 no.4
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• pp.206-210
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• 2017

In this study, an ${\alpha}-Fe_2O_3$ (hematite) coated porcelain plate was sintered in a temperature range from $1100^{\circ}C$ to $1250^{\circ}C$ using ferrous sulfate. The specimens were investigated by X-ray diffractometer (XRD), scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), and UV-visible spectrophotometer. It was confirmed that ${\alpha}-Fe_2O_3$ (hematite) was densely fused to the surface at several tens of ${\mu}m$, the ${\alpha}-Fe_2O_3$ (hematite) was in the form of thin platelet and polyhedra, and no other compounds appeared in the sintering process. In the specimen coated with ${\alpha}-Fe_2O_3$ (hematite), the reflectance spectra show a red absorption band of 560-650 nm. The $L^*$ value decreased from 53.18 to 46.94 with the firing temperature. The values of $a^*$ and $b^*$ were at 19.03 and 15.25 at $1100^{\circ}C$ and gradually decreased with increasing temperature; these values decreased rapidly at $1250^{\circ}C$ to 11.54 and 7.98, respectively. It is considered that the new phases are formed by the phase transition of the porcelain plate (clay), and thus the $a^*$ and $b^*$ values are greatly influenced.

• Bulletin of the Korean Chemical Society
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• v.23 no.12
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• pp.1790-1800
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• 2002

The DNA nucleosides(dA, dC, dG, dT)bound to gold nanoparticles (~13 nm) in aqueous solution has been studied as a probe by the SERS and their coordination structures have been proposed on the basis of them. According to UV-Visible absorption of gold nanoparticles after modifying with DNA nucleosides, the rates of absorption of dA, dC, and dG were much faster than that of dT as monitored by the aggregation kinetics at 700 nm. These data indicated that the nucleosides dA, dC, and dG had a higher affinity for the gold nanoparticles surface than nucleoside dT. As the result of SERS spectra, the binding modes of each of the nucleosides on gold nanoparticles have been assigned. A dA binds to gold nanoparticles via a N(7) nitrogen atom of the imidazole ring, which the C(6)-$NH_2$ group also participates in the coordination process. In the case of dC, it binds to the gold surface via a N(3) nitrogen atom of the pyrimidine ring with a partial contribution from the oxygen of C(2)=O group. A coordination of dG to the gold surfaces is also proposed. Although the dG has the two different nitrogens of a pyrimidine ring and the amino group, the N(1) nitrogen atom of a pyrimidine ring has a higher affinity after the hydrogen migrates to the amino group. Conversely, dT binds via the oxygen of the C(4)=O group of the pyrimidine ring. Accordingly, these data suggest that the nitrogen atom of the imidazole or the pyrimidine ring in the DNA nucleosides will bind more fast to the gold nanoparticles surfaces than the oxygen atom of the carbonyl group.

• Journal of the Korean Chemical Society
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• v.38 no.7
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• pp.485-495
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• 1994

Several new symmetric and asymmetric homo and hetero dinuclear complexes of the type $[Cl(dppp)(NO)_2M({\mu}-pyz)M'(NO)_2(dppp)Cl][ClO_4]_2$ and $[Cl(phen)(NO)_2M({\mu}-pyz)M'(NO)_2(dppp)Cl][ClO_4]_2$(M,M'= Mo or W; phen = 1,10-phenanthroline; dppp = 1,3-bis(diphenylphosphino)propane; pyz = 1,4-pyrazine) were synthesized in three-steps starting from $[M(NO)_2Cl_2]_n(M = Mo, W)$. The final products were purified by eluting it through silica gel column ($2{\times}20$ cm) with acetone as the eluent. Characterization of these complexes and some related complexes was accomplished through UV-vis., $^1H$-NMR, $^{13}C$-NMR and IR spectroscopies as well as elemental analysis. The infrared spectra indicate that the NO groups occupy cis-positions of the octahedral. The $^1H$ and $^{13}C-NMR$ data for the new compounds revealed a dimeric structures with bridged pyz.

• Journal of Environmental Science International
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• v.19 no.7
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• pp.849-860
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• 2010

A new $N_3O_2$ pentadentate ligand, N,N'-Bis(2-hydroxybenzyl)-ethylenetriamine(H-BHET 3HCl) was synthesized. The hydrochloric acid salts of Br-BHET 3HCl, Cl-BHET 3HCl, $CH_3O$-BHET 3HCl and $CH_3$-BHET 3HCl containing Br-, Cl-, H-, $CH_3O-$ and $CH_3-$ groups at the para-site of the phenol group of the H-BHEP were synthesized. The structures of the ligands were confirmed by C. H. N. atomic analysis and $^1H$ NMR, $^{13}C$ NMR, UV-visible and mass spectra. The calculated stepwise protonation constants(${\logK_n}^H$) of the synthesized $N_3O_2$ ligands showed six steps of the proton dissociation. The orders of the overall protonation constants($\log{\beta}_p$) of the ligands were Br-BHET < Cl-BHET < H-BHET < $CH_3O$-BHET < $CH_3$-BHET. The orders agreed well with that of para Hammett substituent constants(${\delta}_p$). The calculated stability constants($\logK_{ML}$) between the ligands and heavy metal ions (Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II)) agreed well with the order of the overall proton dissociation constants of the ligands but they showed a reverse order in para Hammestt substituent constants(${\delta}_p$). The order of the stability constants between the heavy metal ions with the synthesized ligands were Co(II) < Ni(II) < Cu(II) > Zn(II) > Cd(II) > Pb(II).

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.70.3-70.3
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• 2016

Active galactic nuclei (AGNs) typically show a non-thermal continuum locally represented by a power-law and many prominent emission lines in the UV and optical regions. AGNs are classified by two types, where Type I AGNs exhibit both broad and narrow lines and only narrow lines are observed in Type 2 AGNs. The unification models of AGNs invoke the existence of a molecular torus just outside of the broad line region. In the presence of a high column HI region associated with the molecular torus, we propose that significant fraction of broad line photons near Lyman series can be scattered by atomic hydrogen in the torus. In particular, $Ly{\alpha}$ being the strongest emission line, strong linear polarization may develop around $Ly{\alpha}$ through Rayleigh scattering. We adopt a Monte Carlo technique to investigate the polarized transfer of $Ly{\alpha}$ in a thick HI region with the shape of a torus. We consider the range of HI column density N_HI = 1020-23 with fixed geometric parameters of the torus such as the inner and outer radii and the height. We present the polarized spectra and angular distribution of Rayleigh scattered radiation around $Ly{\alpha}$. We find that the $Ly{\alpha}$ core part is polarized in the direction perpendicular to the symmetry axis whereas in the far wing part it is polarized in the parallel direction. It is concluded that the unification of AGNs implies that $Ly{\alpha}$ can be uniquely polarized through Rayleigh scattering.

• The Korea Journal of Herbology
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• v.23 no.3
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• pp.27-32
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• 2008

Objectives : In this paper, we describe that $^1H-NMR$ spectroscopy may be superior to the conventional HPLC for the quantitative analysis of hesperidin from Citrus unshiu. Methods : $^1H-NMR$ spectra (400 MHz) were recorded in $DMSO-d_6$ using a Varian UNITY Inova AS 400 FT NMR spectrometer. One hundred milligram of powdered Citrus unshiu was weighed out and mixed with 1 ml of $DMSO-d_6$ with sonication for 30 min (room temperature). The extracts were filtrated through a 0.45 ${\mu}m$ PVDF filter and 0.5 ml of filtrated extract used for quantitative $^1H-NMR$ measurement (added 1 mg of dimethyl terephthalate as internal standard). The quantity of hesperidin was calculated by the ratio of the intensity of the compound to the known amount of internal standard. For HPLC analysis, the half gram of plant material was extracted with 60 ml of MeOH for 2 hours. The extracts were made 100 ml volume and analyzed by a Waters HPLC system using a YMC ODS column. The total flow rate was 1.0 ml/min with a sample volume 10 ${\mu}l$ and UV detection at 280nm. Results : The contents of hesperidin in Citrus unshiu was determined $5.33{\pm}0.06$% in the quantitative $^1H-NMR$ method and $5.15{\pm}0.12%$ in HPLC method. Using the quantitative $^1H-NMR$ the contents of hesperidin can be determined in much shorter time than the conventional HPLC measurements. Conclusions : From those results, the advantages of quantitative $^1H-NMR$ analysis are that can be analyzed to identify and quantify, and no reference compounds required for calibration curve. Besides, it allows rapid and simple quantification for hesperidin with an analysis time for only 10 min without any pre-purification steps.

• Korean Journal of Agricultural Science
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• v.41 no.3
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• pp.169-175
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• 2014

Objective of this study was to investigate effects of pre-processing method and number of sampling leaves on stability of the reflectance measurement for Chinese cabbage and kale leaves. Chinese cabbage and kale were transplanted and cultivated in a plant factory. Leaf samples of the kale and cabbage were collected at 4 weeks after transplanting of the seedlings. Spectra data were collected with an UV/VIS/NIR spectrometer in the wavelength region from 190 to 1130 nm. All leaves (mature and young leaves) were measured on 9 and 12 points in the blade part in the upper area for kale and cabbage leaves, respectively. To reduce the spectral noise, the raw spectral data were preprocessed by different methods: i) moving average, ii) Savitzky-Golay filter, iii) local regression using weighted linear least squares and a $1^{st}$ degree polynomial model (lowess), iv) local regression using weighted linear least squares and a $2^{nd}$ degree polynomial model (loess), v) a robust version of 'lowess', vi) a robust version of 'loess', with 7, 11, 15 smoothing points. Effects of number of sampling leaves were investigated by reflectance difference (RD) and cross-correlation (CC) methods. Results indicated that the contribution of the spectral data collected at 4 sampling leaves were good for both of the crops for reflectance measurement that does not change stability of measurement much. Furthermore, moving average method with 11 smoothing points was believed to provide reliable pre-processed data for further analysis.