• Bulletin of the Korean Chemical Society
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• 제20권2호
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• pp.147-149
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• 1999

The electronic structures of α- and β-gold selenides are studied. α- and β-AuSe are known as mixed valence compounds having linear (AuSe2, Au+) and square-planar (AuSe4, Au3+) units in their structure simultaneously. Our EHTB calculations, however, show that the oxidation states of Au in α- and β-AuSe are both close to +1. This is because the frontier orbitals are largely made up of Se p-orbitals and Au d-orbitals that lie well below the Fermi level. Our results are consistent with the recent X-ray absorption spectroscopy study on AuSe which show that all Au in the compound exhibit a monovalent state independent of their chemical environments.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2004년도 하계학술연구발표회 논문개요집
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• pp.28-29
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• 2004

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.346-346
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• 2012

We investigated electrical and optical properties and chemical states of amorphous In-Ga-Zn-O (a-IGZO) thin films deposited at different substrate temperatures (from room temperature to $300^{\circ}C$). a-IGZO thin films were fabricated by radio frequency magnetron sputtering using $In_2O_3$ : $Ga_2O_3$ : ZnO = 1 : 1 : 1 target, and their electrical and optical properties and chemical states were investigated by Hall-measurement, UV-visible spectroscopy and x-ray photoelectron spectroscopy (XPS), respectively. The data showed that as substrate temperature increased, carrier concentration increased, but mobility, conductivity, transmittance in the shorter wavelength region (>350 nm), and the Tauc-plot-estimated optical bandgap decreased. XPS data indicated that the intensity of In 3d peak compared to Ga 3d peak increased but the intensity of Zn 3d peak compared to Ga 3d decreased, and that, from the deconvoluted O 1s peak, defects or oxygen vacancies and non-quaternary contents increased as the temperature increased. The relative intensity changes of the In, Zn, and O 1s sub-component are suggested to explain the changes in electrical and optical properties.

• Bulletin of the Korean Chemical Society
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• 제35권5호
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• pp.1422-1432
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• 2014

Convergent all-electron multi-reference configuration-interaction (MRCI) calculations are performed for a lithium dimer with Kaufmann's Rydberg basis functions. A comparison of the results of these calculations with those of the effective core potential/core polarization potential (ECP/CPP) method and experimental data reveals the deficiency of the all-electron ab initio method. The deficiency is related to the mere 51.9% attainment of electron correlation for the ground state. The percent attainment of electron correlation for the first excited state is slightly better than that for the ground state, preventing us from obtaining better agreements with experimental data by means of increasing the size of basis sets. The Kaufmann basis functions are then used with the ECP/CPP method to obtain the accurate convergent potential energy curves for the $^1\prod_u$ states correlated to Li(2p) + Li(2p) and Li(2s) + Li(n = 2, 3, 4). Quantum defect curves (QDCs) calculated for both the $X^2\sum_g$ and 1 $^2\prod_u$ states of the $Li{_2}^+$ ion and the Lu-Fano plot reveal a strong series-series interaction between the two $2snp{\pi}$ and $2pnp{\pi}$ Rydberg series. The QDCs are then used to resolve assignment problems in the literature. The reassignments, performed by Jedrzejewski-Szemek et al., of the dissociation product of the D $^1\prod$ state from (2s+3d) to (2s+3p) and that of the 6 $^1\prod_u$ from (2s+4d) to (2s+4p) are found to be incorrect. It may be more natural to assign their $2snp{\pi}$ Rydberg series as a $2snd{\pi}$ series. The state, assigned as 5p $^1\prod_u$ by Ross et al. and 4d $^1\prod$ by Jedrzejewski-Szemek et al., is assigned as the 7 $^1\prod_u$ state, correlated to the Li(2s) + Li(4f) limit.

• 대한화학회지
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• 제47권4호
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• pp.309-314
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• 2003

Cyclohexane에 녹아있는 Triton X-100/n-hexanol/water 계의 비이온성 역미셀(reverse micelle)에 대한 미세 환경정보를 알아보기 위해 methylene blue(MB)를 이용하여 흡광 및 형광 분광법으로 고찰하였다. 역미셀의 극성 중심(polar core)에서 물의 미세 상태에 대한 정보는 MB와 Triton X-100 사이의 착물형성과 용매화변색(solvatochromic)거동을 조사해 봄으로써 얻을 수 있었으며, 역미셀의 안쪽 극성 중심에서 3가지 상태로 존재함을 알 수 있었다. 물의 세 가지 상태에 대한 $W(=[H_2O]/[Surf])$값은 0.71, 4.98, 7.26으로 측정되었으며, 그에 대한 MB의 형광수명은 $15.45 ns{\pm}0.56$, $12.27 ns{\pm}0.79$, 그리고 $8.28 ns{\pm}0.82$으로 나타났다.

• Bulletin of the Korean Chemical Society
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• 제24권6호
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• pp.817-823
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• 2003

We have performed ab initio calculation on the active site of HIV-1 protease. The FEP method was used to determine the binding free energy of four different of protonated states of HIV-1 protease with inhibitor. The structure of the active site and hole structure was taken from the X-ray crystallographic coordinates of the C₂ symmetric inhibitor A74704 protease bound. The active site was modeled with the fragment molecules of binding pocket, acetic acid/ acetate anion (Asp25, Asp125), formamide (amide bond of Thr26/Gly27, Thr126/ Gly127), and methanol as inhibitor fragment. All possibly protonated states of the active site were considered, which were diprotonated state (0, 0), monoprotonated (-1, 0),(0, -1) and diunprotonated state (-1, -1). Once the binding energy Debind, of each model was calculated, more probabilistic protonated states can be proposed from binding energy. From ab-initio results, the FEP simulations were performed for the three following mutations: Ⅰ) Asp25 … Asp125 → AspH25 … Asp125, ⅱ) Asp25 … Asp125 → Asp25 … AspH125, ⅲ) AspH25 … Asp125 → AspH25 … AspH125. The free energy difference between the four states gives the information of the more realistic protonated state of active site aspartic acid. These results provide a theoretical prediction of the protonation state of the catalytic aspartic residues for A74707 complex, and may be useful for the evaluation of potential therapeutic targets.

• 대한화학회지
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• 제47권3호
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• pp.265-272
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• 2003

본 연구에서는 중학교 1학년 학생들이 만든 물질의 세 가지 상태에 대한 비유를 분석하여 비유의 유형, 학업 성취 수준에 따른 차이, 그리고 오개념 유발 가능성을 조사하였다. 연구 결과, 많은 학생들이 일상생활에서 쉽게 경험할 수 있는 구체적인 소재나 상황을 비유물로 선택하여 부연 설명과 함께 이야기하듯 서술하는 비유를 만드는 것으로 나타났다. 그러나 입자 배열을 변화시키는 잠열의 출입이나 분자의 운동 등의 인과 관계를 고려한 비유는 만들지 못했다. 성취 수준에 따라서는 하위 학생들보다 상위 학생들이 분자의 배열과 운동을 모두 포함하고, 설명을 곁들인 이야기식 비유를 더 많이 만들었다. 한편, 학생들은 고체 상태에서 분자가 움직이지 않는다거나 상태에 따라 입자가 바뀔 수 있다는 것과 같은 오개념을 유발할 수 있는 비유를 만들었다.

• 대한화학회지
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• 제36권4호
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• pp.485-495
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• 1992

기체 및 액체 상태의 여러가지 유기화합물(alcohol, acetate, alkane, acid 및 substituted NH$_2$)과 이성분계 혼합용액(n-alkane/1-chloroalkane)에 대한 점성도를 계산하기 위하여, 분자의 크기, 가지의 형태, 환상구조, 불포화의 정도, 분극성 등이 분자의 성질에 미치는 영향을 잘 설명하여 주는 molecular connectivity index, Wiener index 및 ad hoc descriptor 방법을 이용하였다. 그 결과 기체 상태에 대해서는 Wiener index 방법이, 액체 상태에 대해서는 ad hoc descriptor 방법이 그리고 이성분계에 대해서는 molecular connectivity index 방법이 우수한 방법임을 알 수 있었으며, 각각의 방법으로 구한 최적 상관관계식을 이용하여 점성도를 계산하였고, 이와 같이 구한 이론치와 점성도의 실측치를 비교할 때, 매우 잘 일치하는 결과를 얻을 수 있었다.

• 한국정밀공학회지
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• 제21권1호
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• pp.87-93
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• 2004

Recently, with the development of bio-technology the interests in the micro-fluidic devices for analysis in the fields of biology and medical science have been steadily increasing. Although polymer is considered as one of the best materials for micro-fluidic devices. glass or silicon molds fabricated by photo-lithographic technique have been commonly used. However, it is generally perceived that the conventional photolithographic technique has the limitation for fabricating micro-channels for micro-fluidic devices. In this work, the possibility of fabrication of micro-fluidic channels on PDMS by using the mechano-chemical process and the effect of surface states on the fluid flow were investigated. Experimental results revealed that PDMS mold fabricated by the mechano-chemical process could be used effectively to replicate micro-fluidic channels with high reproducibility and dimensional accuracy. It was also found that the fluid flow generation and flow speed were largely affected by the hydrophilicity and the surface roughness of the micro-channel surfaces.

• Bulletin of the Korean Chemical Society
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• 제32권9호
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• pp.3395-3399
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• 2011

Copper oxide thin films were synthesized by reactive radio frequency magnetron sputtering at different oxygen gas ratios. The chemical and physical properties of the thin films were investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD). XPS results revealed that the dominant oxidation states of Cu were $Cu^0$ and $Cu^+$ at 0% oxygen ratio. When the oxygen ratios increased above 5%, Cu was oxidized as CuO as detected by X-ray induced Auger electron spectroscopy and the $Cu(OH)_2$ phase was confirmed independent of the oxygen ratio. The valence band maxima were $1.19{\pm}0.09$ eV and an increase in the density of states was confirmed after formation of CuO. The thickness and roughness of copper oxide thin films decreased with increasing oxygen ratio. The crystallinity of the copper oxide films changed from cubic Cu through cubic $Cu_2O$ to monoclinic CuO with mean crystallite sizes of 8.8 nm (Cu) and 16.9 nm (CuO) at the 10% oxygen ratio level.