• Journal of Photoscience
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• v.8 no.3_4
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• pp.87-92
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• 2001

Intramolecular excimer formation of 1,3-di(1-pyrenyl)propane (Py-3-Py) and fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) were used to investigate the effects of parathyroid hormone (PTH) on the bulk bilayer fluidity of the plasma membrane vesicles isolated from cultured osteoblasts (OB-PMV). In a dose-dependent manner, rat PTH-(1-34) [rPTH-(1-34)] increased the excimer to monomer fluorescence intensity ratio (I'/I) of Py-3-Py and decreased the anisotropy (r) of DPH in OB-PMV. This indicates that PTH increased both the lateral and rotational diffusion of the probes in OB-PMY. Selective quenching of DPH fluorescence by trinitrophenyl groups was utilized to examine the transbilayer fluidity asymmetry of OB-PMV. The anisotropy, limiting anisotropy, and order parameter of DPH in the inner monolayer were 0.024, 0.032, and 0.062 greater than calculated for the outer monolayer of OB-PMY. Selective quenching of DPH fluorescence by trinitrophenyl groups was also utilized to examine the transbilayer effects of PTH on the fluidity of OB-PMV. rPTH-(1-34) had a greater fluidizing effect on the outer monolayer as compared to the inner monolayer of OB-PMV. Thus, it has been proven that PTH exhibits a selective rather than nonselective fluidizing effect within transbilayer domains of OB-PMV.

• Applied Science and Convergence Technology
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• v.24 no.6
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• pp.254-256
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• 2015

Effect of growth temperature ($T_g$) on the structural and optical properties of $In_{0.5}Ga_{0.5}As$ atomic layer epitaxial (ALE) quantum dots (QDs) is investigated in the range of $T_g=480-510^{\circ}C$. $In_{0.5}Ga_{0.5}As$ ALE QDs consist of 5 periods of short-period superlattices (SPSs) of 1 monolayer-thick InAs and GaAs. Number of coalescent QDs decreases as $T_g$ increases, and they disappear at $T_g=510^{\circ}C$. As $T_g$ increases in the range of $480-495^{\circ}C$, sizes of QDs increase, and densities of QDs decrease due to merge of QDs. On the contrary, although sizes of QDs are maintained at $T_g=495-510^{\circ}C$, densities of QDs decrease. This is attributed to the desorption of material-mainly indium-during the growth interruption. This conjecture is supported by the optical properties of the QDs as a function of $T_g$. As a result, we propose that optimum growth temperature of the QD is $495^{\circ}C$ with less repetition of SPSs than 5.

• Journal of Integrative Natural Science
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• v.4 no.4
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• pp.294-297
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• 2011

Quality of PEDOT electrode thin film vapor phase-polymerized on 3-aminopropyltriethoxysilane (APS) self-assembled monolayer (SAM) is very crucial for making an ohmic contact between electrode and semiconductor layer of an organic transistor. In order to improve the quality of PEDOT film, the quality of APS-SAM laying underneath the film must be in the best condition. In this study, in order to improve the quality of APS-SAM, the monolayer was self-assembled on $SiO_2$ surface by a dip-coating method under strictly controlled relative humidity (< 18%RH). The quality of APS-SAM and PEDOT thin film were investigated with a contact angle analyzer, AFM, FE-SEM, and four-point probe. The investigation showed that a PEDOT film grown on the humidity-controlled SAM is very smooth and compact (sheet resistivity = 20.2 Ohm/sq) while a film grown under the uncontrolled condition is nearly amorphous and contains quite many pores (sheet resistivity = 200 Ohm/sq). Therefore, this study clearly proves that a highly improved quality of APSSAM can offer a highly conductive PEDOT electrode thin film on it.

• Bulletin of the Korean Chemical Society
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• v.23 no.4
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• pp.575-579
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• 2002

Two-dimensionally cross-linked ultrathin films of poly(maleic acid-alt-methyl vinyl ether) (MA-MVE) and poly(allylamine) (PAA) were produced by using sodium dioctadecyl sulfate (2C18S) as the monolayer template for Langmuir-Blodgett (LB) depositio n. The template molecules were subsequently removed by thermal treatment followed by extraction. The polyion-complexed monolayers of three components, i.e., template 2C18S, co-spread PAA, and subphase MA-MVE, were formed at the air-water interface. Their monolayer properties were studied by the surface pressure-area isotherm. The monolayers were transferred on solid substrates as Y type. The polyion-complexed LB films and the resulting network films were characterized by FT-IR spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The cross-linking to form a polymer network was achieved by amide or imide formation through heat treatment under a vacuum. SEM observation of the film on a porous fluorocarbon membrane filter (pore diameter 0.1 ㎛) showed covering of the pores by four layers in the polyion complex state. Extraction by chloroform followed by heat treatment produced hole defects in the film.

• Journal of the Korean institute of surface engineering
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• v.28 no.1
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• pp.34-45
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• 1995

An amphiphilic nitroxide radical(2,2'6,6'-tetramethyl-4-octadecyioxy-1-piperidinyloxyl, TEMOPO) or mixture of TEMOPO and arachidic acid(Icosanoic acid, AA), was spread on water surface by the Langmuir-Blodgett(LB) method and surface pressure-area curve was measured. Such monolayer films of TEMOPO were transferred onto surfaces of photo transferable tin oxide electrodes(PTTO) by the LB method under various surface pressure with the transfer ratio of larger than 0.95 at the surface pressure higher than 15mN/m. The electrochemical effect of functional nitroxy radical monolayer onto semi-conductive electrode to electrolyte have been investigated by using LB method. Cyclic voltammetry technique was used for the electrochemical behavior measurement of TEMOPO monolayer onto the PTTO in 0.18 mo1/$dm^3$ $H_2SO_4$ solutions. The shape of voltammograms was found to change from one electrode to another. The amount of charge for the oxidation and the re-reduction of the cation to TEMOPO were evaluated from graphical integration. The amounts of charge were always smaller than those predicted from the $\pi$-$\sigma$ curves though the transfer ratio was unity. The poor reproducibility of the cyclic voltammograms was improved by the mixing with AA. Structure and arrangement of monomolecular layer on water surface and electrode were studied. Characteristics of monolayer film applied for the mediation reaction was also discussed by electrochemical method.

• The Journal of Natural Sciences
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• v.10 no.1
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• pp.1-7
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• 1998

A Lennard-Jones fluid layer adsorbed on a smooth solid surface was studied at coverages $\theta$ ~ 0.8 to 1.8 on an isotherm by performing intensive grand canonical Monte Carlo simulations. The results clearly show a picture of two-step melting process which used to be observed in recent thermodynamic measurements of argon monolayer melting on graphite. The observed melting process consist of an abrupt density change followed by a gradual transition. Snapshots of monolayer configurations indicate that the creation and dissociation of a dislocation pair are involved in the melting mechanism. Taking the effect of system size into account, it is suggested that, while the abrupt density change may be not related to the theory of Kosterlitz, Thouless, Halperin, Nelson, and Young (KTHNY), the second gradual transition is probably a KTHNY-type melting transition.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.6
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• pp.563-567
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• 2006

Indium tin oxide (ITO) used as an electrode in organic light emitting diodes (OLEDs) and organic thin film transistors (OTFTs) was modified by a self-assembled monolayer (SAM). For device fabrication, surface of the ITO was modified by immersion in a solution including various phosphonic acid at room temperature in order to increase work function of an electrode. The work function of ITO with SAM was measured by Kelvin probe. Work function increase of 0.88 eV was observed in ITO with various SAM. Therefore, ohmic contact is achieved in an interface between ITO and organic semiconductors (pentacene). We analyzed the origin of work function increase of ITO with SAM by X-ray photoelectron spectroscopy. We confirmed that increase of oxygen bonding energy attributed to increase the work function of ITO. These results suggested that ITO with the SAM gives a high possibility for high performance of OLEDS and OTFTs.

• Applied Microscopy
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• v.46 no.4
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• pp.217-226
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• 2016

Monolayer hexagonal boron nitride (h-BN) is a phenomenal two-dimensional material; most of its physical properties rival those of graphene because of their structural similarities. This intriguing material has thus spurred scientists and researchers to develop novel synthetic methods to attain scalability for enabling its practical utilization. When probing the growth behaviors and structural characteristics of h-BN, the use of appropriate characterization techniques is important. In this review, we detail the use of scanning and transmission electron microscopies to investigate the atomic configurations of monolayer and bilayer h-BN grown via chemical vapor deposition. These advanced microscopy techniques have been demonstrated to provide intimate insights to the atomic structures of h-BN, which can be interpreted directly or indirectly using known growth mechanisms and existing theoretical calculations. This review provides a collective understanding of the structural characteristics and defects of synthetic h-BN films and facilitates a better perspective toward the development of new and improved synthesis techniques.

• Electrical & Electronic Materials
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• v.9 no.7
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• pp.674-679
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• 1996

Using the home made Kuhn type LB (Langmuir - Blodgett) film's deposition apparatus, We measured the displacement current of monolayer film on the water surface. The obtained displacement current had each different pattern by the kind of solution while varying pressure of the monolayer. Solution of 4 - octyl - 4' - (5 - carboxyl - pentamethyleneoxy ) - azobenzene (8A5H) and stearic acid (CH$_{3}$(CH$_{2}$)$_{16}$COOH) (C18) were spreaded at the air water interface respectively, and the current induced by the dynamic behavior of molecules were pressed by barrier. Displacement current of 8A5H measured small current than C18 at same condition and it was positive direction when increasing pressure but it was negative direction when decreasing pressure. Also, Two patterns of displacement current were symmetrical form and appeared repeatedly. The C18 has unsymmetrical form of displacement current and weak current when decreasing pressure (expansion). The C18 molecules have two distinct peak values of displacement current that show that the orientations of molecules were changed largely at this points. From these results, we obtained that the 8A5H has more elasticity than the C18.8.C18.

• The Korean Journal of Pharmacology
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• v.31 no.3
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• pp.271-278
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• 1995

The relative distribution ratio of barbiturates between hyarocarbon interior and surface region of outer monolayer of synaptosomal plasma membrane vesicles (RSPMV) isolated from rat whole brain was determined by employing the fluorescent probe technique. The two fluorescent probes N- octadecylnaphthyl-2-amine-6-sulfonic acid (ONS) and 12-(9-anthroyloxy) stearic acid (AS) were utilized as probes for hydrocarbon interior and surface of outer monolayer of RSPMV. respectively. The Stern-Volmer equation for fluorescent quenching was modified to calculate the relative distribution ratio. The analysis of preferential quenching of these probes by barbiturates indicates that pentobarbital, hexobarbital, amobarbital and phenobarbital are predominantly distributed on the surface region. whereas thiopental sodium has an accessibility to the hydrocarbon interior of the outer monolayer of the RSPMV. From these results, it is strongly suggested that the more effective penetration into the hydrocarbon interior of the outer monolayer of the membrane lipid bilayer could result in higher general anesthetic activity.