• 한국응용과학기술학회지
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• 제18권3호
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• pp.186-190
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• 2001

By fabricating the organic light-emitting devices (OLEDs) based on phosphorescent material, the internal quantum efficiency can reach 100%, compared to 25% in the case of the fluorescent material. Thus, the phosphorescent OLEDs have recently been extensively studied and showed higher internal quantum efficiencies then the conventional OLEDs. In this study, we investigated the characteristics of the phosphorescent OLEDs, with the green emitting phosphor, $Ir(ppy)_{3}$, (tris(2-phenylpyridine)iridium). The devices with a structure of $ITO/TPD/Ir(ppy)_{3}$ doped in the host material $/BCP/Alq_{3}/Li:Al/Al$ were fabricated, and its electrical and optical characteristics were studied. By changing the doping concentration of $Ir(ppy)_{3}$, we fabricated several devices and investigated the device characteristics. OLEDs doped into BCP by 10% showed the best characteristics. For 10% doped OLEDs, the maximum luminance of was over 10000 $cd/m^{2}$, and the maximum power efficiency was 7.14 lm/W.

• Bulletin of the Korean Chemical Society
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• 제20권12호
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• pp.1493-1500
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• 1999

The electronic transitions from the ground state to low-lying excited states of CF₃OH have been investigated using high level ab initio quantum mechanical techniques. Also the possible photodissociation procedures of CF₃OH have been considered. The highest level employed in this study is TZP CCSD(T) level of theory. The possible four low-lying excited states can result by the excitation of the lone pair electron (n) in oxygen to σ$^*$ molecular orbital in C-O or O-H bond. The vertical transition (n → σ$^*$) energy is predicted to be 220.5 kcal/mol (130 nm) at TZ2P CISD level to theory. The bond dissociation energies of CF₃OH to CF₃O +H and CF₃+OH have been predicted to be 119.5 kcal/mol and 114.1 kcal/mol, respectively, at TZP CCSD level of theory. In addition, the transition state for the unimolecular decomposition of CF₃OH into CF₂O + HF has been examined. The activation energy and energy separation for this decomposition have been computed to be 43.6kcal/mol and 5.0 kcal/mol including zero-point vibrational energy corrections at TZP CCSD(T) level of theory.ed phenols were also estimated.

• 한국화재소방학회논문지
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• 제33권6호
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• pp.80-86
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• 2019

국내에서는 2012년부터 2018년 까지 총 556건의 화학사고가 발생하였다. 화학사고 중 두 가지 이상의 화학물질 이상반응에 의해 발생하는 사고는 그 원인물질을 파악하는데 많은 시간이 필요하여 효과적인 사고대응과 수습을 위해서 신속한 분석이 필요하다. 본 논문은 이상반응에 의해 발생한 화학사고의 원인물질 파악을 위해 양자전이 비행시간 질량분석기를 사용하였다. 이 분석기는 시료채취와 전처리 없이 빠른 응답시간을 가져 실시간 분석이 가능하며 또한 수소친화도가 높은 대부분의 휘발성유기화합물질의 정량·정성 분석이 가능하여 이상반응에 의해 발생되는 화학사고의 원인 물질을 조사하는데 적합하다. 실제로 201◯년 ◯월에 ◯◯ 지역 화학사고 발생 시 양자전이 비행시간 질량분석기를 이용하여 측정한 결과 메탄올과 톨루엔 등이 검출되는 것을 알았으며 이상반응에 의해 발생된 황 계열 화합물이 사고 주변의 강한 악취의 원인임을 알 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1747-1749
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• 1999

Organic electroluminescent devices (OLEDs) have received a great deal of attention due to their potential application as full-color displays. Europium complexes are known as excellent red color-emitting materials for OLEDs since they show intense photoluminescence at around 610 nm with a sharp spectral bandwidth. In this study, triple-layer and multiple quantum-well structures consisting of Eu$(TTA)_3$(bpy) complex well layer sandwiched triphenyldiamine derivative (TPD) layers were fabricated and their photoluminescent characteristics were investigated. Sharp emission at the wavelength of 615 nm has been observed from the triple-layer and multiple quantum-well structures containing Eu complex. Details on the electrical properties of these structures will be also discussed.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.229-240
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• 2002

Quantum mechanical calculation is performed for the $O(^1D)$ + HCl ${\rightarrow}$OH + Cl reaction using Reactive Infinite Order Sudden Approximation. Shifting approximation is also employed for the l ${\neq}$ 0 partial wave contributions. Various dynamical quantities are calculated and compared with available experimental results and quasiclassical trajectory results. Vibrational distributions agree well with experimental results i.e. product states mostly populated at $v_f$ = 3, 4. Our results also show small peak at $v_f$ = 0, which indicates bimodal vibrational distribution. The results show two significant broad peaks in ${\gamma}_i$ dependence of the cross section, one is at ${\gamma}_i$ = $15^{\circ}-35^{\circ}$ and the another is at ${\gamma}_i$= $55^{\circ}-75^{\circ}$ which can be explained as steric effects. At smaller gi, the distribution is peaked only at higher state ($v_f$ = 3, 4) while at the larger gi, both lower state ($v_f$ = 0) and higher state ($v_f$ = 3, 4) are significantly populated. Such two competing contributions (smaller and larger ${\gamma}_i$) result in the bimodal distribution. From these points we suggest two mechanisms underlying in current reaction system: one is that reaction occurs in a direct way, while the another is that reaction occurs in a indirect way.

• Bulletin of the Korean Chemical Society
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• 제26권1호
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• pp.119-126
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• 2005

The geometrical parameters, vibrational frequencies, and relative energies of H$_2$(A$_{n+1}$X$_{2n}$)H$_2$ (A=C or Si, X=O or S, n = 1-2) oligomers have been investigated using high level ab initio quantum mechanical techniques with large basis sets. The equilibrium geometries have been optimized at the self-consistent field (SCF), the coupled cluster with single and double excitation (CCSD), and the CCSD with connected triple excitations [CCSD(T)] levels of theory. The highest level of theory employed in this study is cc-pVTZ CCSD(T). Harmonic vibrational frequencies and IR intensities are also determined at the SCF level of theory with various basis sets and confirm that all the optimized geometries are true minima. Also zero-point vibrational energies have been considered to predict the dimerization and the relative energies.

• Bulletin of the Korean Chemical Society
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• 제14권1호
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• pp.21-29
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• 1993

For the study of relaxation processes in complex spin system, a general master equation, which can be used to simulate a vast range of pulse experiments, has been formulated using the Liouville representation of quantum mechanics. The state of a nonequilibrium spin system in magnetic field is described by a density vector in Liouville space and the time evolution of the system is followed by the application of a linear master operator to the density vector in this Liouville space. In this master equation the nuclear spin relaxation due to intramolecular dipolar interaction or randomly fluctuating field interaction is explicitly implemented as a relaxation supermatrix for a strong coupled two-spin (1/2) system. The whole dynamic information inherent in the spin system is thus contained in the density vector and the master operator. The radiofrequency pulses are applied in the same space by corresponding unitary rotational supertransformations of the density vector. If the resulting FID is analytically Fourier transformed, it is possible to represent the final nonstationary spectrum using a frequency dependent spectral vector and intensity determining shape vector. The overall algorithm including relaxation interactions is then translated into an ANSIFORTRAN computer program, which can simulate a variety of two dimensional spectra. Furthermore a new strategy is tested by simulation of multiple quantum signals to differentiate the two relaxation interaction types.

• Bulletin of the Korean Chemical Society
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• 제19권9호
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• pp.968-973
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• 1998

Solvolyses of para-substituted phenyl chloroformates in water, $D_2O,\;CH_3OD$, 50% $D_2O-CH_3OD$, and in aqueous binary mixtures of acetone, ethanol, methanol are investigated at 25.0 ℃. Product selectivities are reported for a wide range of ethanol-water and methanol-water solvent compositions. These data are interpreted using the Grunwald-Winstein relationship, Hammett equation, and quantum mechanical model. Grunwald-Winstein plots of the first-order rate constants for phenyl chloroformates with $Y_{Cl}$ (based on 1-adamantyl chloride) show marked dispersions into three separate curves for the three aqueous mixtures with a small m value and a rate maximum for aqueous alcohol solvents. To account for these results, third-order rate constants, $k_{ww},\;k_{aw},\;k_{wa}$, and $k_{aa}$ were calculated from the observed $k_{ww}\;and\;k_{aa}$ values together with $k_{aw}\;and\;k_{wa}$ calculated from the computer fit. The kinetic solvent isotope effects determined in water and methanol are consistent with the proposed mechanism of the general base catalyzed carbonyl addition-elimination for para-substituted phenyl chloroformates solvolyses based on mass law and stoichiometric salvation effect studies. This study has shown that the quantum mechanical model predicts transition state variation correctly for $S_N2\;like\;S_AN$ reaction mechanism of para-substituted phenyl chloroformates.

• 대한화학회지
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• 제52권1호
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• pp.7-15
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• 2008

분자들의 전자 흡수스펙트럼에 영향을 주는 분자 핵 운동은 이론적으로 양자동역학적 시간상관함수로 표현된다. 본 연구에서는 분자동역학 전산모사와 양자화학적 계산등의 순 이론적 계산을 이용해 고전역학적 시간상관함수를 구하고 두 가지의 준고전역학적 근사방법으로 양자동역학적 시간상관함수를 얻었다. 또한 이차 축적전개 근사식을 이용하여 액체상에 있는 nile blue 색소분자의 전자전이 흡수스펙트럼을 얻었다. 계산 결과는 실험에서 얻은 스펙트럼과 비교적 잘 일치하였으며, 실험 결과와의 비교를 통해, 본 계의 용매화 동역학의 시간 척도는 1ps 보다 길며 색소분자에 인접한 용매분자들이 용매화에 영향을 주는 주 성분임을 확인하였다.

• Bulletin of the Korean Chemical Society
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• 제31권10호
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• pp.2841-2848
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• 2010

Quasiclassical trajectory (QCT) method has been used to investigate stereodynamics information of the reaction $O(^1D)+H_2{\rightarrow}\;OH$+H on the DK (Dobbyn and Knowles) potential energy surface (PES) at a collision energy of 23.06 kcal/mol, with the initial quantum state of reactant $H_2$ being set for v = 0 (vibration quantum number) and j = 0-5 (rotation quantum number). The PDDCSs (polarization dependent differential cross sections) and the distributions of P($\theta_r$), P($\phi_r$), P($\theta_r$, $\phi_r$) have been presented in this work. The results demonstrate that the products are both forward and backward scattered. As j increases, the backward scattering becomes weaker while the forward scattering becomes slightly stronger. The distribution of P($\theta_r$) indicates that the product rotational angular momentum j' tends to align along the direction perpendicular to the reagent relative velocity vector k, but this kind of product alignment is found to be rather insensitive to j. Furthermore, the distribution of P($\phi_r$) indicates that the rotational angular momentum vector of the OH product is preferentially oriented along the positive direction of y-axis, and such product orientation becomes stronger with increasing j.