• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.264-264
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• 2013

Strong metal-support interaction effect is an important issue in determining the catalytic ac-tivity for heterogeneous catalysis. In this study, we investigated the support effect and the role of organic capping layers of two-dimensional Pt nanocatalysts on reducible metal oxide supports under the CO oxidation. Several reducible metal oxide supports including CeO2, Nb2O5, and TiO2 thin films were prepared via sol-gel techniques. The structure, chemical state and optical property were characterized using XRD, XPS, TEM, SEM, and UV-VIS spectrometer. We found that the reducible metal oxide supports have a homogeneous thin thickness and crystalline structure after annealing at high temperature showing the different optical band gap energy. Langmuir-Blodgett technique and arc plasma deposition process were employed to ob-tain Pt nanoparticle arrays with capping and without capping layers, respectively on the oxide support to assess the role of the supports and capping layers on the catalytic activity of Pt catalysts under the CO oxidation. The catalytic performance of CO oxidation over Pt supported on metal oxide thin films under oxidizing reaction conditions (40 Torr CO and 100 Torr O2) was tested. The results show that the catalytic activity significantly depends on the metal oxide support and organic capping layers of Pt nanoparticles, revealing the strong metal-support interaction on these nanocatalysts systems.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.44 no.10
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• pp.1311-1316
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• 1995

The electrical properties of the Langmuir-Blodgett (LB) films layered with arachidic acid were studied at the room temperature. The sample was formed with 2 different structure ; One was Al/LB/Al and the other was Au/LB/Au. The precise structure of Al/LB/Al was considered as Al/Al$_{2}$O$_{3}$/LB/Al, because the natural oxide layer was formed on surface of lower Al electrode. The electrical conductivity of Al/Al$_{2}$O$_{3}$/LB/Al structure was determined the value of 3.5 * 10$^{-14}$ S/cm from the measurement of current-voltage (I-V) characteristics. The sample with the structure of Au/LB/Au was made to eliminate the influence of oxide layer in the electrical properties of the LB films. The short circuit current was observed in this sample from the I-V characteristics. To verify the reason of short circuit current generation, copper decoration method was employed to the 15 layers of LB films deposited on the Al and Au electrode each. The defects were shown on the films deposited with Au electrode. This results means that the defects on the LB films which layered with the Au electrode were contributed to the short circuit current. Several films (15, 31, 51, 71L) were deposited on the Au electrode and measured the size of defects with the copper decoration method. The size of defects becomes smaller as the film layer was increased. We conclude that the existence of defects affects the short circuit current generation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.343-346
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• 1999

We have investigated the dielectric and electrical characteristics of palrnitic acid(PA), stearic acid(SA) and arachidic acid(AA) Langmuir-Blodgett(LB) films because these fatty acid systems have a same hydrophilic group and a different hydrophobic one(alky1 chain lqngth). The dielectric characteristics such as the capacitance-frequency(C-F) characteristics and the dielectric dispersion and absorption characteristics of PA, SA and AA through-plane were measured. In the result, the relative dielectric constants of PA, SA and AA LB films were about 3.0-4.6, 2.7-4.1 and 2.4-3.8, respectively. The relative dielectric constants were decreased in proportion to the chain length of alkyl group. Also, the dielectric dispersion and absorption of each fatty acid LB films have arisen from the dipole polarization in the range of $10^4~10^5[Hz]. And, the conductivity of PA, SA and AA LB films obtained from I-V characteristics were about $9{\times}10^{-14}, 3{\times}10^{-l4} and 5{\times}10^{-15}[S/cm], respectively. These results have shown the insulating materials and could control the conductivity by changing the length of alkyl group. Also, we have confirmed that the barrier height of fatty acid systems were about 1.32-1.40[eV] and the dielectric constant were about 3.0-4.2. These values were almost the same ones obtained from dielectric characteristics.

• Journal of the Korean Applied Science and Technology
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• v.31 no.3
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• pp.352-358
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• 2014

We were investigated the stability through the electrochemical characteristics of saturated fatty acid(C12, C14, C16, C18) monolayer LB films by cyclic voltammetry. Saturated fatty acid monolayer LB films was deposited on the indium tin oxide(ITO) glass by the LB method. The electrochemical properties were measured by cyclic voltammetry with a three-electrode system in 0.1 N $NaClO_4$ solution. The measuring range was continuously oxidized to 1650 mV, with an initial potential of -1350 mV was reduced. Scanning rates of 50, 100, 150, 200, and 250 mV/s were set. As a result, LB monolayer films of saturated fatty acid were appeared on irreversible processes by the oxidation current from the cyclic voltammogram. Diffusion coefficient(D) of saturated fatty acid(C12, C14, C16, and C18) was calculated 22.231, 2.461, 7.114 and 2.371 ($cm^2s^{-1}{\times}10^{-4}$) in 0.1 N $NaClO_4$ solution, respectively.

• Journal of the Korean Chemical Society
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• v.37 no.6
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• pp.570-576
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• 1993

1-, 3-, 9-, and 21-Monolayer Langmuir-Blodgett(LB) films of stearic acid were deposited on silver-coated glass slides at the surface pressure of 30 mN/m. Fourier transform infrared(FTIR) reflection-absorption spectra (RAS) of these LB films were recorded at various temperatures from 31 to $72^{\circ}C.$ The spectra at $31^{\circ}C$ exhibited characteristic features of highly perpendicular orientation of the hydrocarbon chain. In the 1-monolayer LB film, the C=O stretching band was not observed, presumably due to the image dipole effect on the silver surface. In the 1-and 3-monolayer LB films, the trans isomer of stearic acid was prominent, but the cis isomer was dominant in the 21-monolayer LB film. FTIR-RAS measurements at an elevated temperature indicated that the chain melting temperature increases and approached to the bulk melting point with increasing the number of monolayer, except for the 1-monolayer LB film which has a higher melting temperature than the 3-monolayer film due to the strong interaction with the silver substrate.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.868-870
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• 1992

Langmuir-Blodgett method is the best candidate for the development of the future molecular electronic devices. But, this molecular thin film devices requires the bulk properties that was influenced by the molecular arrangements and orientations. So, these are of current interest in molecular electronic device fabrications of new materials. In this experiment, the N-docosylquinolium-TCNQ LB films were deposited on the surface pressures of 30 mN/m and 45 mN/m. We measured the polarized UV/visible absorptions of deposited films for the study of the molecular arrangements and orientations. The polarized UV/visible absorption variation on the incidence and polarization angle of the LB film deposited on the surface pressure of 45 mN/m shown methodically variated. So, we concluded that the LB film deposited on 45 mN/mwas arranged better than that obtained at 30 mN/m.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.11a
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• pp.112-115
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• 1993

We have studied a property of arachidic acid Langmuir-Blodgett films at room temperature with two different electrodes ; Al/LB/Al and Au/LB/Au. Since a natural oxide layer is formed on top of the Al electrode, the appropriate structure of AL/LB/Al is Al/Al$_2$O$_3$/LB/Al. To obtain a property of Pure LB film, Aua/LB/Au structure was made. In Al/Al$_2$O$_3$/LB/Al structure, a conductivity of 3.7${\times}$10$\^$-14/ S/cm was obtained by using current-voltage(I-V) characteristics. In Au/LB/AU structure, however, I-V curve was not able to be measured because of short current even in 51 layers of the LB film. A status of defects in the film was confirmed by copper decoration method. We have clearly seen a rather big difference of defect in those two above structures.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.8
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• pp.695-701
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• 2002

Maxwell displacement current (MDC) measuring technique has been applied on the study of monolayers of fatty acid and polyamic acid mixture. The displacement current was generated from monolayers on the water surface by monolayer compression and expansion. Displacement current was generated when the area per molecule was about 132 $^2$and 115 $^2$just before the initial rise of the surface pressure during the 1st and 2nd mixed monolayer compressions cycle, respectively. Maxwell displacement currents were investigated in connection with mixed monolayer compression cycles. It was found that the maximum of MDC appeared at the molecular area just before the initial rise of surface pressure in compression cycles. Ultra thin film of fatty acid and polyamic acid mixture was prepared on the hydrophilic quartz plate by Langmuir-Blodgett (LB) method. The precursor LB film was heated in a vacuum dry oven at 12$0^{\circ}C$ in order to convert it into the LB film of polyimide. The absorption spectra of LB films were also induced photoisomerization by UV and visible light irradiation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.199-202
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• 1996

This paper describes the thermally stimulated current (TSC) measurements of arachidic acid and polyamic acid alkylamine salt(PAAS) LB film, which is a precursor of polyimide(PI). The measurements were performed from room temperature to about 25$0^{\circ}C$ and the temperature was increased at a rate of 0.02 K/s linearly. It shows that peaks of TSC are observed at about 8$0^{\circ}C$ in the arachidic acid and about 8$0^{\circ}C$, 16$0^{\circ}C$ in the PAAS LB films. Results of these measurements indicate that one peak at 8$0^{\circ}C$ is resulted from alkyl group; the other peak at 16$0^{\circ}C$ is due to alkyl and C-O group of PAAS. Additional large peak at about 16$0^{\circ}C$ is due to dipole moments in the PAAS films. The DSC and TGA of PAAS, arachidic acid and octadesylamine are measured. Thermal imidization was performed at 30$0^{\circ}C$ far 1 hour by our pre study

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.05a
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• pp.220-223
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• 1995

Stable polyion-complexed polymeric monolayrers were prepared by spreading perfluoroalkyl monomaleatd copolymers. C$_2$F$\_$8/MA-VE$_2$ and C$_2$F$\_$8/Mv-VE$_3$ on aqueous poly(allylamine) subphase. The monolayer properties have been studied by the surface pressure-area($\pi$-A) isotherms. The C$_2$F$\_$8/MA-VE$_3$containing longer oligoethyleneglycol pendant showed more expaned monolayer phase than the C$_2$F$\_$8/MA-VE$_2$ The polyion-complexed monolayers were transferable on various substrates, and the resulting Langmuir-Blodgett(LB) films were characterized b ET-IR spectroscopy and scanning electron microscopy(SEM) Two-dimensional crosslinking to from a polymer network was achieved by amide formation through heat treatment under vacuum with concurrent removel of perfluoroalkyl tails. SEM observation of this film ona porous membrane filter showed that the four layer film was sufficiently stable to cover the filter pore size of 0.1$\mu\textrm{m}$. The C$_2$F$\_$8/MA-VE$_3$revealed better covering capability than the C$_2$F$\_$8/MA-VE$_2$Immersion of this film in water or in benzend did not cause any change in its appearance and in FT-IR spectra.