• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2010년도 제39회 하계학술대회 초록집
• /
• pp.63-63
• /
• 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.

• 대한화학회지
• /
• 제35권5호
• /
• pp.553-559
• /
• 1991

$NH^{4+}$ retaining 이온으로 치환된 양이온교환 수지관에서 흡착시키는 희토류원소이온의 양, 수지관의 내경, 수지관의 길이 및 용리액의 pH 등을 변화시켜 용리시킨 후 용출액 중의 각 화학종을 분석하여 희토류원소이온의 용리 mechanism과 monazite 광에 포함된 희토류원소들의 분리에 관해 연구하였다. 인접한 희토류원소간의 분리능은 수지의 교환용량 이내에서는 흡착시키는 희토류원소이온의 양을 증가시킬수록 증가하였고, 내경이 같으면 수지관의 높이는 희토류원소이온의 분리능 및 분리시간에 영향을 미치지 않으며 희토류-EDTA 착물은 $NH^{4+}$형 수지에 흡착되지 않음을 알 수 있었다. 용리액의 pH는 수지관 내에서 희토류원소이온과 EDTA와의 반응성에 영향을 미쳐 분리에 큰 영향을 미쳤으며 pH가 낮을수록 분리능은 향상되나 분리시간이 길어짐을 알 수 있었다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2010년도 제39회 하계학술대회 초록집
• /
• pp.246-246
• /
• 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
• /
• 한국신재생에너지학회 2009년도 추계학술대회 논문집
• /
• pp.171-171
• /
• 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.

• 공업화학
• /
• 제3권4호
• /
• pp.649-656
• /
• 1992

t-Butyl hydroperoxide(TBHP)에 의한 염화알릴의 에폭시화에 의해서 에피클로로히드린을 합성하는데 실리카에 담지된 몰리브데늄 촉매를 사용하였다. 속도론적 연구는 회분 반응기를 사용하여 $60-80^{\circ}C$, 10기압에서 TBHP/염화알릴의 농도비를 0.01-0.1의 범위내에서 수행하였다. t-butyl alcohol(TBA)에 의해서 염화알릴의 에폭시화 반응이 억제되었고, 반응속도는 Michaelis-Menten 형태의 속도식으로 표현할 수 있었다. 반응기구는 TBHP와 TBA의 가역흡착과 $Mo/SiO_2$에 흡착된 TBHP와 염화알릴의 표면반응으로 설명할 수 있었다.

• 대한바이러스학회지
• /
• 제27권1호
• /
• pp.69-75
• /
• 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
• /
• 제19권8호
• /
• pp.33.1-33.7
• /
• 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
• /
• 제16권1호
• /
• pp.31-37
• /
• 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.

• Bulletin of the Korean Chemical Society
• /
• 제31권4호
• /
• pp.901-904
• /
• 2010

Decylthiocyanate (DTC) self-assembled monolayers (SAMs) on Au(111) were prepared by solution and vapor phase deposition methods at $50^{\circ}C$ for 24 h. The formation and surface structure of DTC SAMs were examined using scanning tunneling microscopy (STM). STM imaging revealed that DTC SAMs formed in 1 mM ethanol solution at $50^{\circ}C$ were composed of small ordered domains with lateral dimensions of a few nanometers and disordered phases, whereas DTC SAMs formed in the vapor phase at $50^{\circ}C$ contained two ordered phases: a closely packed c($4{\times}2$) superlattice and a striped phase with an interstripe spacing of 2.6 - 2.8 nm. It was also found that the ordered domain and vacancy island formation for DTC SAMs on Au(111) differs significantly from that of decanethiol SAMs, suggesting that adsorption mechanism is different from each other. From this study, it was confirmed that DTC SAMs with a high degree of structural order can be obtained by vapor phase deposition.

• 자연과학논문집
• /
• 제7권
• /
• pp.37-46
• /
• 1995

란탄족이온($Gd^{3+},$ $Tb^{3+},$ $Dy^{3+},$ $Ho^{3+},$ $Er^{3+},$ $Yb^{3+}$ 및 $Lu^{3+}$)과 alizarin complexone(ALC) 사이에 생성한 착물의 전기화학적 거동을 직류폴라로그래피, 펄스차이폴라로그래피 및 순환전압전류법으로 연구하였다. 0.1M $HOA_C-NaOA_C$ 지지전해질 용액에서, 착화제인 ALC는 2전자 1단계의 1:1의 착물을 형성하였으며 이 착물의 환원파는 펄스차이폴라로그래피 및 순환전압전류법으로 흡착성 착물파임을 확인하였다. 착물파의 환원전위는 ALC의 환원파보다 음전위에서 나타났으며 란탄족이온의 농도의 증가에 따른 ALC의 봉우리전류(PI)의 감소와 착물의 봉우리전류($P_2$)의 증가는 란탄족이온의 농도 $2.5X10^5$~$1.0X10^4M$ 범위에서 직선적으로 변화하였다.