• Analytical Science and Technology
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• 제7권2호
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• pp.205-211
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• 1994

Acetic acid and succinic acid bonded polyamine-polyurea(CPPI and SAPPI) resins were synthesized from the reaction of polyethylenimine-polymethylenepolyphenylene isocyanate(PPI) resin as matrix polymer and chloroacetic acid and chlorosuccinic acid respectively. These resins were confirmed with infrared spectrometry and elemental analysis. The adsorption characteristics of the chromium(III) and dichromate(or chromate) ions on the resins were studied by measuring distribution coefficients($K_d$) with changing pH of the solution. It was thought that these ions were adsorbed by ion exchange mechanism. Chromium(III) and dichromate ion could be separated with stepwise elution method by changing pH of the eluent using SAPPI resin packed column($0.6cm(i.\;d.){\times}10cm(L.)$). Also, dichromate ion could be preconecntrated with CPPI resin column by a concentration factor of 50.

• Journal of the Korean Chemical Society
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• 제43권6호
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• pp.656-662
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• 1999

We have obtained retention data of benzene, toluene, ethylbenzene, phenol, and acetophenone at 25, 30, 35, 40, 45 and 50 $^{\circ}C$ in 30/70, 40/60, 50/50, 60/40, 70/30, and 80/20 (v/v %) methanol/water eluents using a $C_18$ phase with a high ligand density. We drew van't Hoff plots from the data, and computed enthalpies and entropies of solute transfer from the mobile to the stationary phase. The cavity formation effect was found the major factor that governs the solute distribution between the mobile and stationary phases. The hydrophobic effect became significant in highly aqueous mobile phases. We also concluded that the Shodex C18-5B stationary phase was a polymer-like phase with a high ligand density, and followed a partially adsorption-like mechanism.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.63-63
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• 2010

Using both experimental and theoretical approaches, we have investigated the adsorption properties of an organic molecule (HATCN), which is used in OLEDs as an efficient hole injection layer, on metal and inert surfaces. We have also studied the structural and electronic properties of such interfaces and the dependences on deposition thickness. We have observed different trends in work function changes with different surfaces. Our photoelectron spectroscopic measurements have revealed an abnormal phenomenon in HATCN on a metal (Cu) surface: the work function decreases at lower coverage (~monolayer) of HATCN on a metal (Cu) surface, but it increases back and becomes higher than that of a bare Cu surface at higher coverage. It has, on the contrary, been observed that the work function of graphene surface just increases as the HATCN coverage increases. Our first-principles density functional calculations has not only verified our experimental observations, but also disclosed the underlying mechanism of such abnormal and different work function behaviors. We have found that the change in work function results from mutual polarization induced by the geometrical deformation and the bond dipole formed at the interface due to the charge redistribution. At low coverage of HAT-CN on Cu substrate, the former reduces the work function significantly by pulling down the vacuum level, while the latter tends to push up the vacuum level resulting in the work function increase.

• Journal of the Korean Chemical Society
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• 제35권5호
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• pp.553-559
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• 1991

The elution characteristics of rare earth elements in $NH^{4+}$ form cation exchange resin had been investigated. Elution were performed varing the loading amount, column diameter, column length and eluent pH. Analysing the chemical species contained in each effluent, elution mechanisms of rare earth elements and the separation of rare earth elements in monazite could be understood. The resolution values of adjacent rare earth elements were improved increasing rare earths adsorption amount wfith the same column within it's exchange capacity. With $NH^{4+}$ resin form, column length does not affect on the resolution values and retention time of rare earth elements and the rare earth-EDTA complex were not adsorbed on $NH^{4+}$ resin form. pH of eluent affected on the reactivities between rare earth elements and EDTA. Decreasing eluent pH, resolution values of adjacent rare earth elements were increased while increasing elution time.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.246-246
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• 2010

As the trench width in the interconnect technology decreases down to nano-scale below 50 nm, superconformal gap-filling process of Cu becomes very critical for Cu interconnect. Obtaining superconfomral gap-filling of Cu in the nano-scale trench or via hole using MOCVD is essential to control nucleation and growth of Cu. Therefore, nucleation of Cu must be suppressed near the entrance surface of the trench while Cu layer nucleates and grows at the bottom of the trench. In this study, suppression of Cu nucleation was achieved by treating the Ru barrier metal surface with capacitively coupled hydrogen plasma. Effect of hydrogen plasma pretreatment on Cu nucleation was investigated during MOCVD on atomic-layer deposited (ALD)-Ru barrier surface. It was found that the nucleation and growth of Cu was affected by hydrogen plasma treatment condition. In particular, as the plasma pretreatment time and electrode power increased, Cu nucleation was inhibited. Experimental data suggests that hydrogen atoms from the plasma was implanted onto the Ru surface, which resulted in suppression of Cu nucleation owing to prevention of adsorption of Cu precursor molecules. Due to the hydrogen plasma treatment of the trench on Ru barrier surface, the suppression of Cu nucleation near the entrance of the trenches was achieved and then led to the superconformal gap filling of the nano-scale trenches. In the case for without hydrogen plasma treatments, however, over-grown Cu covered the whole entrance of nano-scale trenches. Detailed mechanism of nucleation suppression and resulting in nano-scale superconformal gap-filling of Cu will be discussed in detail.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.171-171
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• 2009

The electrodes are usually made of a porous mixture of carbon-supported platinum and ionomers. $SnO_2$ particles provide as supports that have been used for DMFCs, and it have high catalytic activities toward methanol oxidation. The main advantage of $SnO_2$ supported electrodes is that it has strong chemical interactions with metallic components. The high activity to a synergistic bifunctional mechanism in which Pt provides the adsorption sites for CO, while oxygen adsorbs dissociative on $SnO_2$. The reaction between the adsorbed species occurs at the Pt/$SnO_2$ boundary. The morphological observations were characterized by FESEM and transmission electron microscopy (TEM). $SnO_2$ particles crystallinity was analyzed by the X-ray diffraction (XRD). The surface bonded state of the $SnO_2$ particles and electrode materials were observed by the X-ray photoelectron spectroscopy (XPS). The electric properties of the Pt/$SnO_2$ catalyst for methanol oxidation have been investigated by the cyclic voltametry (CV) in 0.1M $H_2SO_4$ and 0.1M MeOH aqueous solution. The peak current density of methanol oxidation was increased as the $SnO_2$ content in the anode catalysts increased. Pt/$SnO_2$ catalysts improve the removal of CO ads species formed on the platinum surface during methanol electro-oxidation.

• Applied Chemistry for Engineering
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• 제3권4호
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• pp.649-656
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• 1992

The synthesis of epichlorohydrin was carried out by the epoxidation of allyl chloride with tert-butyl hydroperoxide(TBHP) over silica supported molybdenum catalyst. Kinetic study was performed at $60-80^{\circ}C$ and 10 atm with the molar ratio of TBHP/Allyl chloride between 0.01 and 0.1 in a batch reactor. The epoxidation of allyl chloride was inhibited by tert-butyl alcohol and kinetic data could be represented by Michaelis-Meten type rate equation. The reaction mechanism could be explained by the combination of reversible adsorption of TBHP and tert-butyl alcohol accompanied by reaction of allyl chloride with TBHP adsorbed on $Mo/SiO_2$ catalyst.

• The Journal of Korean Society of Virology
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• 제27권1호
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• pp.69-75
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• 1997

To evaluate in vitro anti-HIV efficacies of nucleoside derivatives, MT-4 cell line was infected with HIV-1 and HIV-2 respectively and treated with various compounds and the formerly approved drugs such as AZT, d4T, ddC and ddI. CPE method was used to evaluate their antiviral activity. Most dideoxynucleosides, AZT, d4T, ddC and ddI, showed anti-HIV activities against both viruses but no other compounds including anti-herpesvirus drugs did any. Further experiments were carried out to study their inhibitory mechanism of viral adsorption. The results showed no inhibition of syncytium formation due to an interaction between the gp120 expressed in HIV -infected cell surface and CD4 receptor on the uninfected cell surface in the presence of AZT. AZT showed no activity up to $100\;{\mu}g/ml$. Inhibition of reverse transcriptase (RT) in the presence of AZT-triphosphate was tested by using RT expressed in E. coli and purified and its $IC_{50}$ was 4.5 nM.

• Fisheries and Aquatic Sciences
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• 제19권8호
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• pp.33.1-33.7
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• 2016

Antifreeze proteins (AFPs) lower the freezing point but not the melting point of aqueous solutions by inhibiting the growth of ice crystals via an adsorption-inhibition mechanism. However, the function of type IV AFP (AFP IV) is questionable, as its antifreeze activity is on the verge of detectable limits, its physiological concentration in adult fish blood is too low to function as a biological antifreeze, and its homologues are present even in fish from tropic oceans as well as freshwater. Therefore, we speculated that AFP IV may have gained antifreeze activity not by selective pressure but by chance. To test this hypothesis, we cloned, expressed, and assayed AFP IV from cultured subtropical olive flounder (Paralichthys olivaceus), which do not require antifreeze protein for survival. Among the identified expressed sequence tags of the flounder liver sample, a 5'-deleted complementary DNA (cDNA) sequence similar to the afp4 gene of the longhorn sculpin was identified, and its full-length cDNA and genome structure were examined. The deduced amino acid sequence of flounder AFP IV shared 55, 53, 52, and 49 % identity with those of Pleuragramma antarcticum, Myoxocephalus octodecemspinosus, Myoxocephalus scorpius, and Notothenia coriiceps, respectively. Furthermore, the genomic structure of this gene was conserved with those of other known AFP IVs. Notably, the recombinant AFP IV showed a weak but distinct thermal hysteresis of $0.07{\pm}0.01^{\circ}C$ at the concentration of 0.5 mg/mL, and ice crystals in an AFP IV solution grew star-shaped, which are very similar to those obtained from other polar AFP IVs. Taken together, our results do not support the hypothesis of evolution of AFP IV by selective pressure, suggesting that the antifreeze activity of AFP IV may have been gained by chance.

• Corrosion Science and Technology
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• 제16권1호
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• pp.31-37
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• 2017

A synergistic effect was observed in the combination of nitrite and ethanolamines. Ethanolamine is one of the representative organic corrosion inhibitors and can be categorized as adsorption type. However, nitrosamines can form when amines mix with sodium nitrite. Since nitrosamine is a carcinogen, the co-addition of nitrite and ethanolamine will be not practical, and thus, a non-toxic combination of inhibitors shall be needed. In order to maximize the effect of monoethanolamine, we focused on the addition of molybdate. Molybdate has been used to alternate the addition of chromate, but it showed insufficient oxidizing power relative to corrosion inhibitors. This work evaluated the synergistic effect of the co-addition of molybdate and monoethanolamine, and its corrosion mechanism was elucidated. A high concentration of molybdate or monoethanolamine was needed to inhibit the corrosion of ductile cast iron in tap water, but in the case of the co-addition of molybdate and monoethanolamine, a synergistic effect was observed. This synergistic effect could be attributed to the molybdate that partly oxidizes the metallic surface and the monoethanolamine that is simultaneously adsorbed on the graphite surface. This adsorbed layer then acts as the barrier layer that mitigates galvanic corrosion between the graphite and the matrix.