• Journal of the Korean Chemical Society
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• v.60 no.4
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• pp.267-275
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• 2016

Experiment is recognized as an important part in science and science education. Scientists do experiments for verifying or refuting theory and they take many forms to do experiments. One of the central goals of science education is to improve inquiry ability. So we have taken for granted that students engage in authentic inquiry and experiment which scientists carry out to research. But it is not always positive about discussions and opinions what school experiment and its role is in learning science and understanding about science. There is certainly a gap between experiments which scientists and students do even though there is a theoretical basis of school science experiment. In this study, we discussed how scientific inquiry and school inquiry are different, and what it means to use instrument in school science experiment. And as a case, we analyzed chemistry experiments in science textbook and manipulation level of instruments which were handled in chemistry experiments, we shed light on the meanings of experiments and instruments in school science inquiry based on the result of experiments and instruments analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.1555-1562
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• 2015

Metal oxide semiconductors have been applied in several areas, such as solar cells, sensor, optical elements and displays, due to the high surface area, unique electrical and optical characteristics. Zinc oxide among the metal oxide has excellent physicochemical properties. Zinc oxide is a n-type semiconductor with a wide direct transition band gap of 3.37 eV at room temperature and large exciton binding energy of 60 meV. Cation-doped zinc oxide studies were conducted to complement the electrical and optical characteristics. In this paper, Al-doped ZnO was synthesized by hydrothermal synthesis using microwaves. ZnO was synthesized by adjusting the precursor ratio and using different dopants. The optimal ZnO synthesis conditions for crystal shape and optical properties were determined. The optical properties of aluminum doped zinc oxide were then examined by SEM, XRD, PL, UV-vis absorbance spectrum, and EDS.

• Applied Chemistry for Engineering
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• v.32 no.6
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• pp.632-639
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• 2021

In this research, fluorine doping was performed to enhance the photocatalytic activities of WO₃ which were measured using methylene blue dye. WO_3-xF_x photocatalyts were prepared by a vaper phase fluorination during a sintering for preparing WO₃ photocatalysts from a WCl₆ precursor. The bandgap energy of WO₃ photocatalysts decreased from 2.95 eV to 2.54 eV, and the oxygen vacancies site increased by about 55% after fluorine doping. In addition, the initial degradation efficiency of methylene blue showed that the fluorine doped sample showed a 6-fold increase in photocatalytic activities from 10% to 60% compared to that of the untreated sample. It is believed that fluorine is doped to reduce the band gap of photocatalysts, enabling the catalytic activity with low energy, and that oxygen vacancies-generated surface defects increase the visible light absorption region of WO₃ photocatalysts, thereby increasing photocatalytic activity. In this study, it was confirmed that fluorine-doped WO_3-xF_x photocatalysts with an excellent photocatalytic activity can be manufactured easily using a one-step vaper phase fluorination that does not require a post-treatment process.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.505-512
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• 2014

A new donor-accepter-donor-accepter-donor (D-A-D-A-D) type 2,1,3-benzothiadiazole-thiophene-based acceptor unit 2,5-di(4-(5-bromo-4-octylthiophen-2-yl)-2,1,3-benzothiadiazol-7-yl)thiophene ($DTBTTBr_2$) was synthesized. Copolymerized with fluorene and indeno[1,2-b]fluorene electron-rich moieties, two alternating narrow band gap (NBG) copolymers PF-DTBTT and PIF-DTBTT were prepared. And two copolymers exhibit broad and strong absorption in the range of 300-700 nm with optical band gap of about 1.75 eV. The highest occupied molecular orbital (HOMO) energy levels vary between -5.43 and -5.52 eV and the lowest unoccupied molecular orbital (LUMO) energy levels range from -3.64 to -3.77 eV. Potential applications of the copolymers as electron donor material and $PC_{71}BM$ ([6,6]-phenyl-$C_{71}$ butyric acid methyl ester) as electron acceptors were investigated for photovoltaic solar cells (PSCs). Photovoltaic performances based on the blend of PF-DTBTT/$PC_{71}BM$ (w:w; 1:2) and PIF-DTBTT/$PC_{71}BM$ (w:w; 1:2) with devices configuration as ITO/PEDOT: PSS/blend/Ca/Al, show an incident photon-to-current conversion efficiency (IPCE) of 2.34% and 2.56% with the open circuit voltage ($V_{oc}$) of 0.87 V and 0.90 V, short circuit current density ($J_{sc}$) of $6.02mA/cm^2$ and $6.12mA/cm^2$ under an AM1.5 simulator ($100mA/cm^2$). The photocurrent responses exhibit the onset wavelength extending up to 720 nm. These results indicate that the resulted narrow band gap copolymers are viable electron donor materials for polymer solar cells.

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.2073-2076
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• 2010

• Journal of the Korean Mathematical Society
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• v.57 no.5
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• pp.1187-1237
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• 2020

Simply reducible groups are important in physics and chemistry, which contain some of the important groups in condensed matter physics and crystal symmetry. By studying the group structures and irreducible representations, we find some new examples of simply reducible groups, namely, dihedral groups, some point groups, some dicyclic groups, generalized quaternion groups, Heisenberg groups over prime field of characteristic 2, some Clifford groups, and some Coxeter groups. We give the precise decompositions of product of irreducible characters of dihedral groups, Heisenberg groups, and some Coxeter groups, giving the Clebsch-Gordan coefficients for these groups. To verify some of our results, we use the computer algebra systems GAP and SAGE to construct and get the character tables of some examples.

• Journal of the Semiconductor & Display Technology
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• v.2 no.3
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• pp.7-11
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• 2003

In this research, the etching characteristics of via contact and deep contact hole have been studied using multi-pole inductively coupled plasma(MICP) etching system. We investigated Plasma density of MICP source using the Langmuir probe and etching characteristics with RF frequency, wall temperature, chamber gap, and gas chemistry containing Carbon and Fluorine. As the etching time increases, formation of the polymer increases. To improve the polymer formation, we controlled the temperature of the reacting chamber, and we found that temperature of the chamber was very effective to decrease the polymer thickness. The deep contact etch profile and high selectivity(oxide to photoresist) have been achieved with the optimum mixed gas ratio containing C and F and the temperature control of the etching chamber.

• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3722-3726
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• 2013

Covalent functionalization of a $Zn_{12}O_{12}$ nano-cage with $CO_2$ molecule in terms of energetic, geometry, and electronic properties was investigated by density functional theory method. For chemisorption configurations, the adsorption energy of $CO_2$ on the $Zn_{12}O_{12}$ nano-cage for the first $CO_2$ was calculated -1.25 eV with a charge transfer of 1.00|e| from the nano-cage to the $CO_2$ molecule. The results show that $CO_2$ molecule was significantly detected by pristine $Zn_{12}O_{12}$ nano-cage, therefore the nano-cage can be used as $CO_2$ storage. Also, more efficient binding could not be achieved by increasing the $CO_2$ concentration. For Physisorption configurations, HOMO-LUMO gap of the configurations has not changed, while slight changes have been observed in the chemisorption configurations.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.25-27
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• 2003

The device characteristics and the interface electronic structures of organic light-emitting devices based on /tris-(8-hydroxyquinoline)aluminum ($Alq_3$) were investigated with Al/NaF cathode. The Al/NaF cathode greatly improved the performance of the device over the Al-only cathode. A series of photoelectron spectroscopy studies on cathode structures including Al/LiF and $Al/CaF_2$ revealed that the performance enhancement originated mainly from the HOMO peak shift upon the fluoride deposition rather than the formation of the gap states

• Journal of Electrochemical Science and Technology
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• v.9 no.2
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• pp.149-156
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• 2018

In this technical note, I report the analysis of electrochemical impedance data measured with potential sweeping. Even though the instruments for voltammetric impedance measurements have been developed for decades using different approaches, their applications are limited due to the lack of well-established protocols to easily analyze voltammetry data. To fill this gap, the singular point of the specific potential is considered that is only determined by the standard/formal potential and the transfer coefficient and is independent of the kinetics and experimental parameters (including revertability) of faradaic reactions. Taking the advantage of its inertness, I suggest an approach employing the singular point as a reference to obtain general electrochemical information. As all the concepts and methods are verified with numerical simulations, this technique is expected to be applied for complex reactions involving electrochemical and chemical reaction mechanisms.