• Journal of the Korean Chemical Society
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• v.55 no.3
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• pp.364-372
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• 2011

The corrosion inhibition of imatinib mesylate (IMT) on mild steel in 0.25 M sulphuric acid has been studied using gravimetric and potentiodynamic polarization techniques at various concentrations of inhibitor, temperature and fluid velocities. The results obtained showed that, inhibition efficiency (% IE) increases with increasing concentration of the inhibitor. The adsorption process on mild steel surface follows Langmuir adsorption isotherm. The values of Gibbs free energies of adsorption obtained suggest that, the adsorption process of IMT on mild steel is chemisorption. Thermodynamic parameters were evaluated and discussed. The electron orbital density distribution of HOMO and LUMO of IMT was used to discuss the inhibition mechanism. FT-IR spectroscopy and SEM images were used to analyze the surface adsorbed film.

• Journal of Photoscience
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• v.7 no.2
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• pp.67-71
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• 2000

A quantum-chemical investigation on the conformations and electronic properties of trans(diphenyl-diheterocyclic) ethenes(t-PHEs) as building block for fully $\pi$-conjuated polymer are performed in order to display the effects of heterocyclic ring substitution. Structures for the molecules, t-PHEs were fully optimized by using semiempirical AM1, PM3 methods, and ab initio HF methods, with 6-31G basic set. The potential energy curves with respect to the change of single are obtained by using ab initio HF/6-31G basic set. The curves are not similar shapes in the molecules with respect to heterocyclic rings. It is shown that the steric repulsion interactions between phenyl ring and heterocyclic ring are subjected to different type with the respect to each heterocyclic ring. Electronic properties of the molecules were molecules were obtained by applying the optimized structures and selected geometries to the extended Huckel method. To investigate the change of HOMO-LUMO gap with respedt to the torsion angle, we select the optimized structures. By using the results, the dependency of conjugation for the energy gaps is analyzed. For t-PHE the energy gap increase up to 0.52 eV compared with its planar structure. In the cases of t-PHE and t-PHE, the energy gap increase by 1.29 and 1.15 eV, respectively, compared with its planar structure.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.120.2-120.2
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• 2011

The improvement of solar energy-to-electricity conversion efficiency has continued to be an important research area of dye-sensitized solar cells (DSSCs). The mechanism of DSSCs is based on the injection of electrons from the photoexcited dye into the conduction band of nanocrystalline TiO2 or ZnO. Thus, the electronic structures, such as HOMO, LUMO, and HOMO-LUMO band gaps of dye moleculed in DSSC are deeply related to the electron transfer by photoexcitation and redox potential. Organic dyes, because of their many advantages, such as high molar extinction coefficients, convenience of customized molecular design for desired photophysical and photochemical properties, inexpensiveness with no transition metals contained, and environment-friendliness, are suitable as photosensitizers for DSSC. We believe that practically useful organic dye photosensitizers can be produced by exploiting electron donor/acceptor system with proper length of ${\pi}$-conjugation in a chromophore to control the absorption wavelength and enhance the photovoltaic performance. In this research, We designed and synthesized organic dyes also investigated the photoelectrochemical properties of a series of ionic dyes in DSSCs.

• Journal of the Korean Chemical Society
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• v.25 no.4
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• pp.207-213
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• 1981

Conformations of thioacetamide (TAA) and its protonated form were determined using the CNDO/2 method, and the intermolecular interaction energies between the protonated TAA and water were calculated. It was found that: (1) protonation occurs preferentially on the N rather than on the S atom, (2) the stabilization energy of intermolecular perturbation between the protonated TAA and water was also large for the N-protonated TAA. This causes preferential CS bond cleavage due to large antibonding nature of the CS bond in the LUMO, and leads to an orbital controlled reaction.

• Journal of the Korean Chemical Society
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• v.27 no.6
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• pp.391-398
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• 1983

The reaction for the hydrogen abstraction from substituted-toluenes by t-butoxyl and t-butyl radical have been studied MO theoretically using CNDO/2 method. The reaction for the abstraction from substituted-toluenes by t-butoxyl radical showed the negative ${\rho}$ values from Hammett equation, since t-butoxyl radial is electrophilic, relatively low energy SOMO, which can interact with HOMO energy of substituted-toluens. On the other hand, t-butyl radical is nucleophilic, relatively high energy SOMO, which can interact with LUMO energy of substituted-toluenes. And so the reaction of abstraction from substituted-toluenes by t-butyl radical exhibited positive ${\rho}$ values.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.227-227
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• 2014

OLED 소자에 사용되는 유기물들은 대부분 전자에 비해 정공의 이동속도가 매우 빨라 소자 효율의 손실이 일어난다. 본 연구에서는 이러한 전하 이동도의 불균형에 의한 OLED 소자 성능의 감소를 개선하기 위해 HBL (hole blocking layer) 물질로 BCP (HOMO : 6.5 eV, LUMO : 2.83 eV)를 도입하였다. 그러나 BCP의 LUMO 값이 약 3 eV를 가지기 때문에 전자의 이동에 영향을 미치는 것으로 예상되어 더 높은 효율을 가지는 소자를 제작하기 위해 host 물질을 상용물질(PGH02)로 교체하였다. PGH02의 HOMO 값은 약 5.86 eV로 소자에 사용된 HTL (hole transport layer)의 HOMO 값(5.54 eV)에 비해 높은 값을 가지기 때문에 HBL의 역할 역시 가능하여 소자의 성능이 상당히 개선되는 것을 확인할 수 있었다. 또한 전하 이동도의 균형을 맞추기 위해 ETL 물질로는 기존에 많이 사용되고 있는 Alq3 (${\mu}{\sim}10-5cm2/Vs$)에 비해 이동도가 10배 이상 빠른 Bebq2 (${\mu}{\sim}10-4cm2/Vs$)를 사용하였다. HTL (hole transport layer) 물질로는 상용물질(LHT 259)를 사용하였고, LHT 259의 전하 이동도는 FET (field effect transistor)를 제작하여 측정하였다. 이를 기반으로 하여 ETL과 HTL의 두께를 조절하여 전하 이동도가 균형을 이루는 OLED 소자를 제작하기 위해 실험을 진행하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.473-473
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• 2012

유기발광소자는 낮은 구동전압, 빠른 응답속도, 넓은 시야각 등의 장점으로 소형 디스플레이에 사용되며 차세대 조명으로 관심을 받고 있다. 고효율의 유기발광소자를 제작하기 위해서 다양한 유기 인광물질 합성 및 연구가 진행되고 있으며, 다양한 호스트 물질을 사용하여 전자와 정공의 주입을 향상하여 고효율의 인광 유기발광소자를 제작하였다. 본 논문에서는 발광층에 N,N'-dicarbazolyl-3,5-benzene (mCP)와 1,3,5-tri(phenyl-2-benzimidazole)-benzene (TPBi)를 혼합 호스트로 사용하였으며 tris(2-phenylpyridine)iridium ($Ir(ppy)_3$)청색 인광물질을 도핑하여 고효율의 인광 유기발광소자를 제작하였다. 유기발광소자의 발광층에 단일 호스트와 혼합 호스트의 전기적 및 광학적 특성을 비교 분석하여 전자 및 정공 수송 메커니즘을 규명하였다. 혼합 호스트 TPBi의 lowest unoccupied molecular orbital (LUMO) 준위와 엑시톤 저지층 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)의 LUMO 준위와 비슷하여 전자의 주입을 향상시키는 역할을 하며, 다른 혼합 호스트 mCP는 highest occupied molecular orbital (HOMO)와 정공수송층 N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB)의 HOMO와 비슷하여 정공의 주입을 향상시키는 역할을 하여, $Ir(ppy)_3$에 전자와 정공의 주입이 향상되어 고 효율의 인광 유기발광소자를 제작할 수 있었다. 이와 같은 실험결과는 인광 유기발광소자의 호스트 물질에 따른 전하주입 메커니즘을 설명 하였으며 고효율의 인광 유기발광소자 제작에 도움을 줄 것이다.

• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3211-3217
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• 2013

Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations have been employed to investigate the molecular structures and absorption spectra of three D-${\pi}$-A-type organic dyes (C1-1, D5 and TH208) containing identical ${\pi}$-spacers and electron acceptors, but different aromatic amine electron-donating groups (tetrahydroquinoline, triphenylamine and phenothiazine). The coplanar geometries indicate that the strong conjugation is formed in the dyes. The electronic structures suggest that the intramolecular charge transfer from the donor to the acceptor occurs, and the electron-donating ability of tetrahydroquinoline is stronger than those of triphenylamine and phenothiazine. The computed orbital energy levels of these dyes confirm that the electrons could be injected from the excited dyes to the semiconductor conduction band and the oxidized dyes could be reduced effectively by electrolyte. The TD-DFT results show that the CAM-B3LYP/6-31+G(d, p) is suitable for calculating the absorption spectra. The first absorption band for these dyes is assigned to the HOMO${\rightarrow}$LUMO and HOMO-1${\rightarrow}$LUMO transitions.

• Journal of the Korean Chemical Society
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• v.36 no.1
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• pp.38-43
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• 1992

The Hammett's substituent constants were interpreted for substituted stilbenes by HMO method. The appropriate quantum chemical indices are chosen as independent contribution of the inductive and the resonance effects for substituent constants. It has been found that theoretical values, ${\sigma}_p{^{th}}$, defined as sum of the net charge, self atom polarizability and difference in HOMO energy between substituted- and unsubstituted-stilbenes, correlated with experimental Hammett's substituent constants. The dipole moments were found to be correlated with differences in ${\sigma}_p{^{th}}$ between two substituents for disubstituted stilbenes. It has been also found that transition optical spectra, ${\lambda}_{max}$ of the substituted stilbenes depend on difference between the HOMO and the LUMO energy as expected.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.108-111
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• 2009

We have determined the electronic energy level alignment at the interface between 4,4'-bis-N-phenyl-1-naphthylamino biphenyl (NPB) and 1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile (HAT-CN) using ultraviolet photoelectron spectroscopy (UPS). The highest occupied molecular orbital (HOMO) of 20 nm thick HAT-CN film was located at 3.8 eV below the Fermi level. Thus the lowest unoccupied molecular orbital (LUMO) is very close to the Fermi level. The HOMO position of NPB was only about 0.3 eV below Fermi level at NPB/HAT-CN interface. This enables an easy excitation of electrons from the NPB HOMO to the HAT-CN LUMO, creating electron-hole pairs across this organic-organic interface. We also study the interaction of HAT-CN with a few metallic surfaces including Ca, Cu, and ITO using UPS and ab-inito electronic structure calculation techniques.