• Journal of the Speleological Society of Korea
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• no.76
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• pp.37-42
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• 2006

The Dielectric Barrier Discharge (DBD) is a nonequilibrium gas discharge that is generated in the space between two electrodes, which are separated by an insulating dielectric layer. The dielectric layer can be put on either of the two electrodes or be inserted in the space between two electrodes. If an AC or pulse high voltage is applied to the electrodes that is operated at applied frequency from 50Hz to several MHz and applied voltages from a few to a few tens of kilovolts rms, the breakdown can occur in working gas, resulting in large numbers of micro-discharges across the gap, the gas discharge is the so called DBD. Compared with most other means for nonequilibrium discharges, the main advantage of the DBD is that active species for chemical reaction can be produced at low temperature and atmospheric pressure without the vacuum set up, it also presents many unique physical and chemical process including light, heat, sound and electricity. This has led to a number of important applications such as ozone synthesizing, UV lamp house, CO2 lasers, et al. In recent years, due to its potential applications in plasma chemistry, semiconductor etching, pollution control, nanometer material and large area flat plasma display panels, DBD has received intensive attention from many researchers and is becoming a hot topic in the field of non-thermal plasma.

• Bulletin of the Korean Chemical Society
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• v.18 no.1
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• pp.32-37
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• 1997

We have built a laser ionization mass spectrometer (LIMS) for chemical composition analysis of solid samples, which employs an Nd:YAG laser and a time-of-flight mass analyzer. In this spectrometer, the maximum mass we identified clearly is higher than 2000 amu. A mass resolution of 230 has been achieved at m/z 208 (Pb element) in the linear TOFMS and can be even improved up to 1550 by employing a reflectron. The detection limit is determined to be on the order of ppm for Fe and In. The depth resolution is found to be about 20Å/spectrum with a laser power of 0.5 J/cm2. We also report a preliminary application of the LIMS to identifying impurities resident in several solid samples.

• Journal of the Korean Chemical Society
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• v.41 no.3
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• pp.117-122
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• 1997

On the basis of our previous paper[Bull. Korean Chem. Soc. 1995, 16, 1015], the relative stability, ionization potential, and chemical reaction of the neutral and multiply charged $C_{60}$n ions(n=3+ to 6-) have been investigated by the semi-empirical MNDO method. $C_{60}^{1-}$ has the highest stability. The ionization potential values of the $C_{60}$ ions range from 15.31 eV of $C_{60}^{2+}$ to -13.01 eV of $C_{60}^{6-}$. These values show a linear relationship according to charges. The average IP per charge is 3.15 eV from our calculations and 3.22 eV from the linear function of IP. A charge- or electron-transfer reaction of $C_{60}^{n+}$ will only occur if the ionization potential of any guest molecule is lower than the electron affinity of the host $C_{60}^{n+}$. If the energy gap between ionization potential and electron affinity, ${\Delta}_{IP-EA}$, is high, charge-transfer reactions arise by the charge-controlled effect. However, if ${\Delta}_{IP-EA}$ is low, electron-transfer reactions arise by the frontier-controlled effect.

• Bulletin of the Korean Chemical Society
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• v.23 no.2
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• pp.189-194
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• 2002

Two-photon resonant third photon ionization of atomic bromine $(4p^5\;^2P_{3/2}\;and\;^2P_{1/2})$ has been studied using a photoelectron imaging spectroscopy in the wavelength region 250 - 278 nm. The technique has yielded simultaneously both relative branching ratios to the three levels of $Br^+(^3P_2,\;^3P_{0.1}\;and^1D_2)$ with $4p^4$ configuration and the angular distributions of outgoing photoelectrons. The product branching ratios reveal a strong propensity to populate particular levels in many cases. Several pathways have been documented for selective formation of $Br^+(^3P_2)$ and $Br^+(^3P_{0.1})$ ions. In general, the final ion level distributions are dominated by the preservation of the ion core configuration of a resonant excited state. Some deviations from this simple picture are discussed in terms of the configuration interaction of resonant states and the autoionization in the continuum. The photoelectron angular distributions are qualitatively similar for all transitions, with a positive $A_2$ anisotropy coefficient of 1.0-2.0 and negligible $A_4$ in most cases, which suggests that the angular distribution is mainly determined by the single-photon ionization process of a resonant excited state induced from the third photon absorption.

• Bulletin of the Korean Chemical Society
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• v.32 no.4
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• pp.1221-1227
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• 2011

Ethyl pyruvate (EP) is known as a scavenger of reactive oxygen species (ROS) in the body through its role in the donation of diketone groups to metals to form an EP-metal complex. In order to develop a method for the quantification of EP in biological media, a sensitive and specific, high-performance liquid chromatographyelectrospray ionization-mass spectrometry (HPLC-ESI/MS) method is used to determine the EP-alkali metal ion binding species. The analyte was separated on a ZORBOX SB-C8 ($3.5{\mu}m$, $30mm{\times}2.1mm$ I.D.) column and analyzed in selected ion monitoring (SIM) mode with a positive ESI interface using the m/z 255 $[2M + Na]^+$ ion. The method was validated over the concentration range of $0.5-60.0\;{\mu}g$/mL under 1/9 (v/v) of acetonitrile/methanol solvent system with flow rate 0.05 mL/min. The limit of quantification (LOQ) was $0.5{\mu}g$/mL.

• Journal of the Korean Chemical Society
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• v.35 no.5
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• pp.469-479
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• 1991

According to the recent paper by B. Fricke (J. Chem. Phys. 84, 862 (1986)), it is reported that the atomic polarizability (${\alpha}$) correlates very strongly with the first ionization potential (IP) within the groups of elements. In our study, we obtained very significant correlations between $ln\alpha$ and IP as well as lnIP by employing the least squares method. In examining the correlations of various atomic electronegativities with their first ionization potentials and the atomic polarizability within the groups of elements, good correlation coefficients are obtained except for groups 3a and 4a. Within the periods of elements, good correlation coefficients are obtained with no exception. This allows a very good prediction of various atomic polarizabilities undetermined.

• Journal of the Korean Applied Science and Technology
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• v.20 no.2
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• pp.125-129
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• 2003

The effects of molecular structure on the redox properties of the organic electroluminescent materials (Ir$(ppy)_3$ Ir$(m-ppy)_3$ Ir$(p-toly)_3$) were studied using cyclic voltammetry and spectroscopy. These iridium complexes show reversible oxidation and reduction on the electrode, which produce the symmetric cyclic voltammogram. It indicates that these materials are very stable under repetitive oxidation/reduction cycles. The electrochemically determined ionization potentia/electron affinity values are 5.4OeV/3.02eV for Ir$(ppy)_3$, 5.36eV/2.96eV for Ir$(m-ppy)_3$, and 5.35eV/2.97eV for Ir$(p-toly)_3$ from the SCE(Standard Calomel Electrode). The electrically determined band gaps are 2.38eV (521nm), Ir$(ppy)_3$, 2.4OeV (517nm), Ir$(m-ppy)_3$, and 2.38eV (521nm). Ir$(p-toly)_3$, which are similar with the optical band gaps. The position of methyl group on 2-phenylpyridine (ppy) effects do not influence much on the ionization potential, electron affinity, and band gap of Ir$(ppy)_3$ derivatives.

• Bulletin of the Korean Chemical Society
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• v.24 no.9
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• pp.1319-1323
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• 2003

This paper presents a successful demonstration of the on-line coupling of MEKC (micellar electrokinetic chromatography) to ESIMS (electrospray ionization mass spectrometry) for the quantitative analysis of seven s-triazine herbicides. The on-line MEKC-ESIMS was used to determine the structure of CE-separated peaks of seven triazine herbicides. The mixture of triazine herbicides was separated in a 20 mM sodium borate buffer (pH 8.5) containing 15 mM sodium dodecylsulfate (SDS) by using a bare fused-silica capillary. Electrospray ionization mass spectrometer was operated in the positive-ion mode when the mass spectra of seven triazine herbicides were observed from each peak, and the solution of water-methanol-formic acid (50/49/1 v/v/v) was used as a sheath liquid. The effects of SDS concentration, the run buffer pH, and the electric field on the separation of seven s-triazine herbicides were investigated. The MEKC-ESIMS detection showed 5 to 10 times higher sensitivity compared to the MEKC-UV detection. In addition, it did not need any pretreatment step.

• Bulletin of the Korean Chemical Society
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• v.26 no.8
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• pp.1235-1240
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• 2005

A combination of electrospray ionization and tandem mass spectrometry was used to characterize the scavenging reactions of acrylamide (AA) in the presence of glutathione (GSH) in vitro. In the presence of GSH, AA was deactivated effectively and scavenged by reactions consuming small amount of GSH. Reaction products and structural information were identified using collision-induced dissociation (CID) in an ion trap mass spectrometer. In the mixture of GSH and AA, significant increase in abundance of fragment ion peak was observed at m/z 233, which was identified as $[Cys-Glu]^+$, formed by the elimination of glycine moiety of GSH. GSH also contributes to the AA scavenging reaction by conjugating with AA through the sulfhydryl group in cysteine moiety. The probable scavenging reaction pathway of AA in the presence of GSH has been proposed based on the CID experimental data.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1534-1535
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• 2007

This paper describes a novel microfluidic device with a microfabricated electrospray source for a sheathless electrospray ionization interface to a mass spectrometer. This electrospray ionization-mass spectrometry (ESI-MS) device consists of a triangular-shaped metal emitter, allowing the generation of an efficient electrospray for peptide detection, and microfluidic channels monolithically in a glass microchip. The performance of the proposed interface was evaluated by opimizing its experimental condition and spraying standard peptides. The spraying has high signal strength and stability, with a relative standard deviation of 2.9% and singly-charged and doubly-charged peaks of the peptides were successfully detected. The metal emitter source showed a good performance to be comparable to commercially available emitters in signal strength and stability.