• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.201-201
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• 2011

Recently, mussel-inspired surface modification, called polydopamine coating has been extensively implemented to many areas, due to its material versatility and ease to use. In particular, incubation of substrates in an alkaline dopamine solution resulted in self-polymerization of dopamine and modified variety of material surfaces, including noble metals, metal oxides, ceramics, and synthetic polymers. However, the polydopamine coating has a drawback to practical use; it takes more than 12 hrs to introduce sufficient polydopamine layers to solid substrates. Here, we investigated the rate-enhanced polydopamine coating by varying reaction conditions: pH, concentration, and the addition of the oxidizing agent. As a result, the optimum condition for fast polydopamine coating was found, and solid substrates were efficiently coated with polydopamine layers in just few minutes using the condition. The polydopamine-modified surface was characterized by XPS and contact angle goniometry, and the biocompatibility of the modified surface was also proved by cell attachment test.

• Journal of the Korean Graphic Arts Communication Society
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• v.12 no.1
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• pp.13-27
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• 1994

Litho printing ink vehicles based on rosin modified phenolic are faster drying, have better durability, are harder and glosser and have greater resistance to water than ones based on ester gums. Ink-Water balance and rheological properties are important in litho printing process. These physical properties is concerned with molecular weight of Resin to use vehicle. So this paper was studied about the effects of changing molecular weight of Rosin modified phenolic on surface tension, viscosity, pseudoplasticity and printablility of Litho Inks. The results were as follows. 1) The surface tension of model inks depended on the molecular weight of the resin : Dispersion componnent of ink increase but non dispersion component decrease as molecular weight of Resin increase. 2) Water pick-up of litho ink is more fast balance, using low molecular weight of Resin. 3) Viscosity, Yield value and Newtonian value of model inks increase as molecular weight of Resin increase. 4) The litho ink prepared with the modified phenolic of which molecular weight is about 20000 showed the highest printing density and gloss.

• Bulletin of the Korean Chemical Society
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• v.26 no.3
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• pp.361-370
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• 2005

In this review, the field of biosurface organic chemistry is defined and some examples are presented. The aim of biosurface organic chemistry, composed of surface organic chemistry, bioconjugation, and micro- and nanofabrication, is to control the interfaces between biological and non-biological systems at the molecular level. Biosurface organic chemistry has evolved into the stage, where the lateral and vertical control of chemical compositions is achievable with recent developments of nanoscience and nanotechnology. Some new findings in the field are discussed in consideration of their applicability to nanobiotechnology and biomedical sciences.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.34 no.6
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• pp.616-621
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• 2008

Osseointegration is a result of bone formation and bone regeneration processes, which takes place at the interface between bone and implant, and it indicates a rigid fixation that can be stably maintained while functional loading is applied inside the oral cavity as well as after implant placement. Although many researches were carried out about osseointegration mechanism, but cellular and molecular events have not been clarified. With recent development of molecular biology, some researches have examined biological determinants, such as cytokine, growth factors, bone matrix proteins, during osseointegration between bone and implant surface, other researches attempted to study the ways to increase bone formation by adhering protein to implant surface or by inserting growth factors during implant placement. Cellular research on the reaction of osteoblast especially to surface morphology (e.g. increased roughness) has been carried out and found that the surface roughness of titanium implant affects the growth of osteoblast, cytokine formation and mineralization. While molecular biological research in dental implant is burgeoning. Yet, its results are insignificant. We have been studying the roles of growth factors during osseointegration, comparing different manifestations of growth factors by studying the effect of osseointegration that varied by implant surface. Of many growth factors, $TGF-{\beta}$, IGF-I, BMP2, and BMP4, which plays a significant role in bone formation, were selected, and examined if these growth factors are manifested during osseointegration. The purpose of this article is to present result of our researches and encourage molecular researches in dental implant.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1366-1371
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• 2003

Molecular dynamics (MD) simulations are conducted to investigate the thermophysical characteristics and the stability of liquid threads for various conditions. A cylindrical thread in the simulation domain is made of Lennard-Jones molecules. The surface tension of liquid threads can be determined from local densities, local normal and transverse components of the pressure force. In order to understand the effects of thread radii on surface tensions, the Tolman equation is modified on the basis of the cylindrical coordinates for prediction of surface tensions. Surface tensions calculated from the MD simulation agree with the prediction from the modified Tolman equation. In addition, surface tensions decrease linearly with increasing system temperature. For a binary system, the surface tension decreased linearly compared to that for a pure system with increasing binary ratio of solute molecules which have relatively large value of the affinity coefficient. For a fixed binary ratio, the surface tension increased slightly with the affinity coefficient and the maximum value appear around where the affinity coefficient is 1.5 and decreased rapidly for upper value of 1.5. In addition, the critical wavelengths of perturbations are proven to be directly proportional to the equimolar dividing radii of the liquid threads.

• Advances in nano research
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• v.11 no.6
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• pp.607-620
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• 2021

In this paper, the vibrations of boron nitride nanotubes (BNNTs) are investigated by considering the electric field. To consider the size effect at nanoscale dimensions, the surface elasticity theory is exploited. The equations of motion of the BNNTs are obtained by applying Hamilton's principle, and the clamped-guided boundary conditions are also considered. The governing equations and boundary conditions are discretized using the differential quadrature method (DQM), and the natural frequency is obtained by using the eigenvalue problem solution. The results are compared with the molecular dynamic simulation in order to validate the accurate values of the surface effects. In the molecular dynamics (MD) simulation, the potential between boron and nitride atoms is considered as the Tersoff type. The Timoshenko beam model is adopted to model BNNT. The vibrations of two types of zigzag and armchair BNNTs are considered. In the result section, the effects of chirality, surface elasticity modulus, surface residual tension, surface density, electric field, length, and thickness of BNNT on natural frequency are investigated. According to the results, it should be noted that, as an efficient non-classical continuum mechanic approach, the surface elasticity theory can be used in scrutinizing the dynamic behavior of BNNTs.

• 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.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 1999.11b
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• pp.34-42
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• 1999

The present investigation has focused up on the study of the adsorption of three different molecular mass fractions of a polyDiMethylDiAllylAmmoniumChloride (DMDAAC) (8750(LM\ulcorner), 48000(MM\ulcorner) and 1200000(HM\ulcorner)) on bleached chemical fibres. Both kinetics of adsorption and equilibrium adsorption measurements have been conducted and each adsorption has been measured by polyelectrolyte titration. The results show that the LM\ulcorner polymer can reach all of the charges in the fibre wall whereas the MM\ulcorner and HM\ulcorner can only reach the external surfaces of the fibres. It is also shown that the kinetics of adsorption of the LMw polymer is not at all affected by the presence of a saturated layer of HMw polymer on the surface of the fibres. Finally, the results from the investigation show that it is possible to have full coverage of the external surface of the fibres by a high molecular mass polymer and a full coverage of the internal surface of the fibres with a low molecular mass polymer. This is true if the high molecular masspolymer is added first followed by addition of the low molecular masspolymer.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.654-654
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• 2013

One of the most important yet unresolved problems in molecular electronics is the controversy over the number and nature of multiple conductance peaks in single-molecule junctions. Currently, there are three competing explanations of this observation: (1) manifestation of different molecule-electrode contact geometries, (2) formation of gauche defects within the molecular core, (3) involvement of different electrode surface orientations [1]. However, the exact origin of multiple conductance peaks is not yet fully understood, which indicates our incomplete understanding of the scientifically as well as techno-logically important organic-metal contacts. To theoretically resolve this problem, we previously applied a multiscale computational approach that combines force fields molecular dynamics (FF MD), density functional theory (DFT), and matrix Green's function (MGF) calculations [2] to a thermally fluctuating haxanedithiol (C6DT) molecule stretched between flat Au(111) electrodes, but could observe only a single conductance peak [3]. In this presentation, using DFT geometry optimizations and MGF calculations, we consider molecular junctions with more realistic molecule-metal contact conformations and Au(111) electrode surface directions. We also conduct DFT-based molecular dynamics for the highly stretched junction models to confirm our conclusion. We conclude that the S-Au coordination number should be the more dominant factor than the electrode surface orientation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.277-280
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• 1997

It is important to investigate the molecular arrangement and the orientational distribution in the study of LB films. Polarized UV/visible absorption spectra make it possible to reveal the molecular arrangement and the orientational distribution. It is clarified that the PAAS LB films have specific directions in the molecular arrangement and the orientational distribution, which art different in intensity corresponding to the surface pressure. Unpolarized UV/visible absorption spectra reveal that the surface pressure is proportional to the finn thickness and is related to the molecular orientation. Current-Voltage(I-V) measurements provide that the current decreases as the surface pressure increases and there are certain phenomena called switching phenomena. Switching effort indicates that the current flows in high conductivity during on-state and suddenly decreases into low conductivity during off-state.