• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.255-256
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• 2023

The development of corrosion inhibitors with outstanding performance is a never-ending and complex process engaged in by researchers, engineers and practitioners. Computational assessment of organic corrosion inhibitors performance is a crucial step towards the design of new task-pecific materials. Herein, electronic features, adsorption characteristics and bonding mechanisms of two pyridine oximes, namely 2-pyridylaldoxime (2POH) and 3-pyridylaldoxime (3POH) with the iron surface were investigated using molecular dynamics (MD), and self-consistent-charge density-unctional tight-binding (SCC-DFTB) simulations. SCC-DFTB simulations revealed that 3POH molecule can form covalent bonds with iron atoms in its neutral and protonated states, while 2POH molecule can only bond with iron through its protonated form, resulting in interaction energies of -2.534, -2.007, -1.897, and -0.007 eV for 3POH, 3POH+, 2POH+, and 2POH, respectively. Projected density of states (PDOSs) analysis of pyridines-Fe(110) interactions indicated that pyridine molecules chemically adsorbed on the iron surface.

• The Korean Journal of Food And Nutrition
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• v.36 no.1
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• pp.6-16
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• 2023

To investigate the anti-inflammatory activity of submerged culture using Cordyceps militaris mycelium, culture-including mycelia was extracted and lyophilized into postbiotics (hot-water extract; CM-HW). HW was fractionated into crude polysaccharide (CM-CP) by ethanol precipitation, and CM-CP was further dialyzed into CM-DCP by dialysis with running water using 12~14 kDa dialysis tube. When the cytotoxicity of subfractions against cells was assessed, no subfraction had a cytotoxic impact that was substantially different from the control groups. In an inflammatory model using LPS-stimulated RAW 264.7 cells, CM-DCP significantly decreased IL-6 and MCP-1 production levels compared to the LPS-control group. CM-DCP also inhibited IL-6 and IL-8 secretion in HaCaT keratinocytes stimulated with TNF-α and IFN-γ. In the meanwhile, the neutral sugar content and mannose ratio of anti-inflammatory CM-DCP were higher than the other fractions, and CM-DCP contained β-1,3/1,6-glucan of 216.1 mg/g. High pressure size exclusion chromatography revealed that CM-DCP contained molecules with a molecular weight range of 5.6 to 144.0 kDa. In conclusion, postbiotics of C. militaris mycelium significantly promoted anti-inflammatory activity, suggesting that neutral polysaccharides including Glc and Man contribute to the anti-inflammation in RAW 264.7 or HaCaT cells.

• Journal of the Korean Chemical Society
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• v.40 no.1
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• pp.59-64
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• 1996

The 7F0→5D0excitation spectra of Eu(Ⅲ) complexed with polyfunctional monocarboxylic acid(glycolic acid, glycine and thioglycolic acid) containing a terminal O, N and S neutral donors and propionic acid were investigated using Eu(Ⅲ) luminescence spectroscopy. In the excitation spectra of Eu(Ⅲ)-propionate system, the stepwise appearance of the peaks was observed at 579.0, 579.2 and 579.5 nm with increasing in the ligand-to-metal ratio, which correspond to the formation of Eu(propionate)2+, Eu(propionate)2+ and Eu(propionate)3 species. Three maximum peaks were also obtained for Eu(Ⅲ)-glycolate, Eu(Ⅲ)-glycinate and Eu(Ⅲ)-thioglycolate systems and were found to be quite similar to those of Eu(Ⅲ)-propionate system. The q values (number of coordinated water molecules of Eu(Ⅲ) ion) obtained from the luminescence decay constants of Eu(Ⅲ)-glycolate and Eu(Ⅲ)-thioglycolate were 7.0 and 7.1, and compare well with 7.3 for Eu(Ⅲ)-propionate: Each ligand units replace around two coordinated water molecules. These results show that the polyfunctional monocarboxylates behaves like the propionate for Eu(Ⅲ) ion coordination.

• Journal of the Korean Chemical Society
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• v.51 no.4
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• pp.339-345
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• 2007

Urea reacts with PtCl2, H2[PtCl6]·6H2O, H2[IrCl6] and Ni(CH3CO2)2 in aqueous solution at high temperature (60-80 °C) yielding [PtCl2(Urea)]·2H2O (1), (NH4)2[PtCl6] (2), (NH4)2[IrCl6]·H2O (3) and [Ni2(OH)2(NCO)2(H2O)2] (4) complexes, respectively. In complex 1, urea coordinates to Pt(II) as a neutral bidentate ligand via amido nitrogen atoms. In complexes 2, 3 and 4 it seems that the coordinated urea molecules decompose during the reaction at high temperature and a variety of reaction products are obtained. All complexes were isolated in moderate yields as dark green (1), yellow (2), pale brown (3) and faint green (4) precipitates, respectively. The reaction products were characterized by their microanalysis, IR, 1H and 13C NMR spectra as well as thermal analysis. General mechanisms describing the formation of these complexes were suggested.

• Journal of the Korean Applied Science and Technology
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• v.8 no.1
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• pp.59-67
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• 1991

The reactions of semicarbazide hydrochloride with aliphatic and alicyclic ketones were studied kinetically at 15, 25, 35 and 45$^{\circ}C$ in 20% ethanol solution buffered at pH 2.9. The rate of cyclohexanone semicarbazone formation is 5.5 times as fast as that of cyclopentanone semicarbazone, while 3-pentanone semicarbazone is 4.7 times as slow as that of 2-pentanone, The activation energy of cyclohexanone, 2-pentanone, 2 hexanone, cyclopentanone, 4-methyl-2-pentanone and 3-pentanone semicarbazone formation are calculated 5.08, 7.52, 8.79, 9.59, 9.49, 11.59, respectively. It is concluded from the effect of ionic strength that the reaction is affected by not ion but neutral molecules being progressed hydrogen bond between oxygen atom of carbonyl group and hydrogen atom of acid-catalyst and concerted nucleophilic attack of free base on the carbonly compound. Dependence on pH of the rate of 2-pentanone semicarbozone formation is linear relationship below pH 4.60 and above pH 5.60. As a result of studing citric acid catalysis, second order constants increase linearly with citric acid concentration. As the catalyst concentration is varied from 0.025 to 0.10 mol/1 at pH 2.90, the rate constants increase 1.4 times, but slight increase is observed at pH 5.60. Conclusively, the rate-determining step is formation of tetrahedral interemediate below pH 4.65 and dehydration between pH 5.60 and pH 7.11. It is concluded that the formation reaction of cyclohexanone semicarbazone is faster than cyclopentanone semicarbazone due to the steric strain in the process of forming tetrahedral intermediate.

• Journal of the Korean Chemical Society
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• v.44 no.1
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• pp.4-9
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• 2000

We investigated the self-association and protonation state of norfloxacin, a member of quinokme antibiotics, using electric absorption and potentiom,etric titration. Both nitrogen at the piperazine ring and carboxylic acid were protonated at a low pH (cationic norfloxacin), and deprotonated at a high pH (anionic norfloxacin). In the intermediate pH range, a neutral species was dominant with the possibility of forming a zwitter ion. We also observed that nortloxacin molecules can be sracked to form a dimer at an intermediate pH, The equilibrium constant of the norfloxacin-DNA complex formation, which was measured by Stem-Volmermethod, increases as the pH of the system is lowered. This observation indicates that it is the cationic nortloxacin that forms a complex with DNA among various norfloxacin species in aqueous solution.

• Applied Chemistry for Engineering
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• v.8 no.1
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• pp.59-66
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• 1997

Di(10-hemisuccinyloxy)decyl muconate(DDM) and di(6-hemisuccinyloxy)hexyl muconate(DHM) were synthesized, and showed a phase transition in an aqueous solution at 97 and $79^{\circ}C$, respectively. They did not form liposomes by themselves or even in the presence of cholesterol or dioleoylphosphatidylethanolamine(DOPE), but did form liposomes when they were mixed with phosphatidylcholine(PC). DHM molecules in liposome membranes were readily polymerized via 1,2-polymerization process on exposure to 254nm. Liposomes composed of DOPE/dioleoylphosphatidylcholine(DOPC)/DHM(3/3/1) were stable at neutral pH, but leaky at weakly acidic pH. The leakage of entrapped calcein from liposomes in phosphate-buffered saline (PBS, $37^{\circ}C$) of pH 4.8 and 5.8 was complete within 30 and 50 min, respectively. The release of toke entrapped calcein was increased with decreasing pH such that 50% and 100% of the calcein were released at pH near 5.5 and 5.0, respectively.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4321-4326
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• 2011

A new series of heteroleptic cyclometalated iridium(III) complexes has been synthesized and characterized by absorption, emission and cyclic voltammetry studies: $(pqx)_2Ir(acac)$ (1), $(dmpqx)_2Ir(acac)$ (2) and $(dfpqx)_2Ir(acac)$ (3) where pqx=2-phenylquinoxalinate, dmpqx=2-(2,4-dimethoxyphenyl)quinoxalinate, dfpqx=2-(2,4-difluorophenyl) quinoxalinate and acac=acetylacetonate anion. The reaction of excess acetylacetone with ${\mu}$-chloride-bridged dimeric iridium complex, $[(C\^N)_2Ir({\mu}-Cl)]_2$, gives a complex 1 and an unusual hydridoiridium(III) complex, $(pqx)IrH(acac)_2$ (4). The complex 1, 2 and 3 show their emissions in an orangered region (${\lambda}_{PL,max}$ = 583-616 nm), and the emission maxima can be tuned by the change of substituent at phenyl ring of 2-phenylquinoxaline ligand. The phosphorescent line shape indicates that the emissions originate predominantly from $^3MLCT$ states with little admixture of ligand-based $^3({\pi}-{\pi}^*)$ excited states. The structures of complex 3 and 4 are additionally characterized by a single crystal X-ray diffraction method. The complex 3 shows a distorted octahedral geometry around iridium(III) metal ion. A strong trans influence of the phenyl ring is examined. In complex 4, there are two discrete molecules which are mirror images each other at the ratio of 1:1 in an unit cell. We propose that the phosphorescent complex 1, 2 and 3 are possible candidates for the phosphors in OLEDs applications.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.8
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• pp.849-855
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• 2012

The effect of electric fields on the response of diffusion flames in a counterflow has been investigated experimentally by varying the AC voltage and frequency. The result showed that the flame was stationary with high AC frequency above the threshold frequency, and it increased with the applied voltage and then leveled off at 35 Hz. Below the threshold frequency, however, the flame oscillated with a frequency that was synchronized with the applied AC frequency. This oscillation can be attributed to the ionic wind effect due to the generation of bulk flow, which arises from the momentum transfer by molecular collisions between neutral molecules and ions, where the ions in the reaction zone were accelerated by the Lorentz force.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.192-192
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• 2011

Hyperthermal ion scattering experiments were conducted with low kinetic energy (<35 eV) cesium ion beams to analyze the UV-photolyzed water-ice films. Neutral molecules (X) on the surface were detected as cesium-molecule ion clusters ($CsX^+$) which were formed through a Reactive Ion Scattering (RIS) process. Ionic species on the surface were desorbed from the surface via a low energy sputtering (LES) process, and were analyzed [1]. Using these methods, the thermal stability of hydronium ion ($H_3O^+$) that was produced by UV light was examined. As the thermal stability of $H_3O^+$ is related with the reaction, $H_3O^+$ + OH + $e^-$ (or $OH^-$) ${\rightarrow}$ $2H_2O$, which is similar or same with the reverse reaction of the auto-ionization of water, the result from this work would be helpful to understand the auto-ionization of $H_2O$ in water-ice that has not been well-understood yet. However, as $H_3O^+$ was not detected through a LES method, the titration experiment of $H_3O^+$ with methylamine ($CH_3NH_2$, MA), MA + $H_3O^+\;{\rightarrow}\;MAH^+$ + $H_2O$, was conducted. In this case, the presence of $MAH^+$ indicates that of $H_3O^+$ in the ice. Thus the pristine ice was photolyzed with UV light for a few minutes and this photolyzed ice was remained at the certain temperature for minutes without UV light. Then MA was adsorbed on that surface so that the population of $H_3O^+$ was found. From the calibration experiments, the relation of $MAH^+$ and $H_3O^+$ was found, so that the thermal stability of $H_3O^+$ can be investigated [2].