• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.197-197
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• 2011

In this study, in contrast with cases in which Scanning Tunneling Microscopy (STM) tip-induced reactions were instigated by the tunneling electrons, the local electric field, or the mechanical force between a tip and a surface, we found that the tungsten oxide (WO3) covered tungsten (W) tip of a STM acted as a chemical catalyst for the S-H dissociative adsorption of phenylthiol and 1-octanethiol onto a Ge(100) surface. By varying the distance between the tip and the surface, the degree of the tip-catalyzed adsorption could be controlled. We have found that the thiol head-group is the critical functional group for this catalysis and the catalytic material is the WO3 layer of the tip. After removing the WO3 layer by field emission treatment, the catalytic activity of the tip has been lost. 3-mercapto isobutyric acid is a chiral bi-functional molecule which has two functional groups, carboxylic acid group and thiol group, at each end. 3-Mercapto Isobutyric Acid adsorbs at Ge(100) surface only through carboxylic acid group at room temperature and this adsorption was enhanced by the tunneling electrons between a STM tip and the surface. Using this enhancement, it is possible to make thiol group-terminated surface where we desire. On the other hand, surprisingly, the WO3 covered W tip of STM was found to act as a chemical catalyst to catalyze the adsorption of 3-mercapto isobutyric acid through thiol group at Ge(100) surface. Using this catalysis, it is possible to make carboxylic acid group-terminated surface where we want. This functional group-selective adsorption of bi-functional molecule using the catalysis may be used in positive lithographic methods to produce semiconductor substrate which is terminated by desired functional groups.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.1
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• pp.26-30
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• 2004

Orientation control of a polyoxometalate (POM) nanoparticle in its two-dimensional arrangement was attempted by Langmuir-Blodgett (LB) technique. For their uniorientation, two carboxyl groups were introduced on one side of the POM particle, and hydrophobic long chains were attached by esterification with the carboxyl groups (C18-POM). The C18-POM layer spread on water surface showed stability against surface pressure up to 60 mN/m. The pattern of the C18-POM isotherm was quite different from stearyl alcohol (C18-OH), while the POM itself did not show any development of surface pressure on water surface. The AFM images of C18-POM LB films showed some microcrystalline structures that were noticed as dot structures by Brewster angle microscopy. The microimages for C18-POM did not completely spread out as a monolayer on the water surface. The XPS spectra indicated the presence of POM structures and stearyl ester bonds formed from about 65% of the total carboxyls. The XRD spectra showed that the unioriented POMs were not positioned with the same lattice distance but rather in a wavy surface state.

• Bulletin of the Korean Chemical Society
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• v.24 no.5
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• pp.633-637
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• 2003

We have studied the surface-enhanced Raman spectroscopy (SERS) spectrum of quinomethionate (6-methyl-1,3-dithiolo[4,5-b]quinoxalin-2-one), which is an insecticide or fungicide used on vegetables and wheat. We observed no signals in the ordinary Raman spectra of solid-state quinomethionate, but when it was adsorbed on a colloidal silver surface, strong vibrational signals were obtained at a very low concentration. The SERS spectra were obtained by silver colloids prepared by the Creighton et al. method. The influence of pH and the aggregation inductors ($Cl^-,\;Br^-,\;I^-,\;F^-$) on the adsorption mechanism was investigated. Two different adsorption mechanisms were deduced, depending on the experimental conditions: The one N atom or two N atoms are chemisorbed on an Ag surface. An important contribution of the chemical mechanism was inferred when the one N atom was perpendicularly adsorbed on a surface. It is possible that quinomethionate can be detected to about $10^{-5}$ M.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.199-200
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• 2015

실리콘 기판위에 Gecko의 피부를 모사한 다층의 나노, 마이크로 구조표면에서 일어나는 응결된 water vapor droplets의 coalescence에 기인하는 surface energy의 kinetic energy의 변환을 통하여 발생하는 water droplets의 self-propelling을 이용한 빙점하에서 dynamic wetting 성질의 관찰을 통해서 얼음 방지, 지연, 또는 얼음 부착성 최소화 표면의 구현 가능성을 보여준다.

• Applied Chemistry for Engineering
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• v.35 no.4
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• pp.335-340
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• 2024

In this paper, we synthesized organic and inorganic hybrid materials to introduce antibody functionality to UIO-66 and incorporated them into a surface plasmon resonance (SPR) assay to enhance the sensitivity of detecting small molecules such as oxytocin. A biological marker peptide called oxytocin may help in the diagnosis of heart failure, Alzheimer's disease, and cancer. To detect oxytocin at concentrations as low as a few femtomole (fM), we developed a surface sandwich assay utilizing a pair of oxytocin-specific antibodies for enhancing selectivity and one of metal organic frameworks [e.g., UiO-66-(COOH)₂] possessing high porosity and surface-area as a signal amplifier. Initially, real-time SPR assays were used to confirm that each selected oxytocin-specific antibody binds strongly to oxytocin and to different binding sites on oxytocin. One of these antibodies (e.g., anti-OXT[OTI5G4]) was immobilized on the surface of a thin gold chip. Upon sequential injecting of oxytocin and the other antibody (e.g., anti-OXT[4G11]) conjugated to UiO-66-(COOH)₂ onto the surface to form the surface sandwich complex of anti-OXT[OTI5G4]/oxytocin/UiO-66-(COOH)₂-anti-OXT[4G11]), SPR changes, which varied with oxytocin concentration, were then measured in real time. The results demonstrated that sensitivity was amplified by over a million-fold compared to assays without UiO-66-(COOH)₂, enabling oxytocin detection down to approximately 10 fM.

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1215-1218
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• 2010

We demonstrate the possible application of the sandwich type surface-enhanced Raman scattering (SERS) immunoassay using antigen-antibody binding for detection of prostate-specific antigen (PSA) in cancer cells. In this sandwich type of SERS immunoassay, to capture antigens onto the immobilized layer of antibodies on the gold substrate we prepared the monolayer of gold nanoparticles on the APTMS-derivatized surface of a glass slide by using the SAM technique. This sandwich type of SERS immunoassay in which antigens on the substrate specifically capture antibodies on a Raman reporter (DSNB coated gold nanoparticles with R6G) could successfully detect PSA at low levels. A strong SERS spectrum of Raman reporter was observed only with a substrate in which PSA is present.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.371-374
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• 2006

We developed new quantum chemical molecular dynamics and kinetic Monte Carlo programs to simulate the destruction processes of MgO protecting layer in plasma display panel. Our simulation results proposed that MgO(111) surface with nano-dot structures covered by (001) facets has the highest stability, which is against the previous knowledge. The formation of nano-dot structures on the MgO(111) surface covered by (001) facets was found to be the reason for the high stability of the MgO(111) surface. Furthermore, the effect of grain boundary on the stability of MgO surfaces was also clarified.

• Proceedings of the Korean Vacuum Society Conference
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• 2006.08a
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• pp.94-94
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• 2006

• Applied Chemistry for Engineering
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• v.7 no.1
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• pp.101-108
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• 1996

The dynamic surface tension of GL12 (easily biodegradable nonionic surfactant and mild to skin), LAS and SLES aqueous solutions and that of mixed surfactant systems were measured by the maximum bubble pressure method at different mixing ratios. The effects of various salt such as NaCl, CsCl and urea on the dynamic surface tension of mixed surfactant systems were also studied. The dynamic surface tension of GL12 was not influenced by the presence of salts. On the contrary, the dynamic surface tensions of anionic surfactants (LAS and SLES) were significantly affected by the salts. In the mixed surfactant systems, the effect of salt increased as the composition of anionic LAS or SLES increased in the GL12/LAS and GL12/SLES mixtures.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1559-1563
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• 2011

Thermal hydrogenation of phenylacetylene (PA, $C_8H_6$) to styrene ($C_8H_8$) on pre-$C_xH_y$- and C-covered Cu(111) single crystal substrates has been studied using temperature-programmed desorption (TPD) mass spectrometry. Chemisorbed PA with an acetylene group has been proved to be associated with hydrogen of pre-adsorbed $C_xH_y$ to form styrene (104 amu) on Cu surface. For the parent (PA) mass (102 amu) TPD profile, the TPD peaks at 360 K and 410 K are assigned to chemisorbed vertically aligned PA and flat-lying cross-bridged PA, respectively (J. Phys. Chem. C 2007, 111, 5101). The relative $I_{360K}/I_{410K}$ TPD ratio dramatically increases with increasing pre-adsorbed $C_xH_y$ before dosing PA, while the ratio does not increase for pre-C-covered surface. For PA on pre-$C_xH_y$-covered Cu(111) surface, styrene desorption is enhanced relative to the parent PA desorption, while styrene formation is dramatically quenched on pre-C-covered (lack of adsorbed hydrogen nearby) surface. It appears that only cross-bridged PA associates with adsorbed hydrogen to form styrene that promptly desorbs at 410 K, while vertically aligned PA is less likely to participate in forming styrene.