• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.473-476
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• 2004

This study has investigated radiation degradation of low density polyethylene(LDPE). Samples were irradiated using a $Co^{60}\;\gamma-ray$ and ray up to 800 kGy at a dose rate of 5 kGy/hr in the presence of air atmosphere at room temperature. After irradiation, free radical measurement of LDPE has established by electron spin resonance(ESR). Then, each sample was stored for 2 weeks. ESR measurement showed that free radical concentration(FRC) was increased with radiation dose and changed from alkyl, allyl radical to peroxy radical with time.

• Preventive Nutrition and Food Science
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• v.3 no.2
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• pp.203-209
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• 1998

The development of methods for the identification of irradiated foods helps enforce national and international regulations on labelling to ensure the consumer's free choice to buy irradiated or unirradiated foods. and the availabilityof such methods may assist the promotion of international trade in irradiated food products and help prevent abuse of the technology. A number of approaches to determine the physical , chemical, microbiological and biological changes that occur in foods treated with ionizing radiation have been studied. However no single method is universally applicable. Among physical measurements, the leading methods of indentification are electron spin resonance (ESR) spectroscopy and thermoluminescence(TL). ESR is an established non-destructive method for the analysis of free radicals from their traps and TL is the emission of light from irradiated mineral extracts by heating. Viscosity of carbohydrate polymers by causing chain breaks by irradiation, measuring the impedance of potatoes and detection of gases produced radiolytically are promising techniques for identification purposes. Irradiated water-containing foods show significant supercooling when monitored with a differential scanning calorimeter (DSC), which can be applied to identifying irradiated ones.

• Bulletin of the Korean Chemical Society
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• v.21 no.4
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• pp.412-418
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• 2000

Association of cytochrome c with anionic membranes involved both electrostatic and hydrophobic interactions and their relative contributions depended on the physical state of the membrane and the redox state of cyto-chromec.Hydrophobic interaction was favored by the membranes in gel phase, by the membranes with a large curvature, and by the membranes with a high surface charge density. Ferrocytochrome c was less dissociable by NaCl than ferricytochrome c suggesting that a lower protein stability is beneficial for hydrophobic interac-tion.Hydrophobic interaction induced larger structural perturbations on cytochrome c as monitored by the loss of the Fe-Met bond and by the increase in the distance between heme and Trp-59. When bound to anionic mem-branes,spin-labeled cytochrome c showed an electron paramagnetic resonance spectrum with two or more components, providing a direct evidence for multiple conformations of bound cytochrome c.

• Journal of the Korean Chemical Society
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• v.38 no.9
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• pp.628-631
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• 1994

We have studied the paramagnetic $CuF_2$ using the techniques of pulsed nuclear magnetic resonance (NMR). The powder sample revealed two well-separated lines from the distinct $^{19}F$ sites at room temperature. One of the lines showed little frequency shift. However, the other showed a large frequency shift, suggesting electron transfers. Furthermore, the two sites have very short spin-lattice relaxation times $(T_1).$ The frequency-shifted site has the shorter $T_1$ than the unshifted one, reflecting the difference of the electron environments of the two sites.

• Journal of the Korean Magnetics Society
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• v.5 no.3
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• pp.171-174
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• 1995

We have studied the paramagnetic $CuF_{2}$ using the techniques of pulsed nuclear magnetic resonance(NMR). The powder sample revealed two well-separated lines from the distinct $^{19}F$ sites at room temperature and at 77 K. The distinct frequency shifts of the two lines appear to arise from electron transfers. Furthermore, the two sites have very short spin-lattice relaxation times ($T_{1}$). The frequency-shifted site has the shorter $T_{1}$ than the unshifted one, reflecting the difference of the electron environments of the two sites.

• Journal of the Korean Chemical Society
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• v.16 no.1
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• pp.40-45
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• 1972

An electron spin resonance study has been made on lysozyme in. frozen aqueous solutions irradiated with $_{60}Co$ r-rays in air at $77^{circ}K.$ Water resonances are dominant when the concentration and the temperature are both below 20% and $130^{circ}K$ respectively. More solute radicals are produced in the solution of higher concentration. Majority of the solute radicals results from direct hit of the radiation. The same types of radicals are induced at $77^{circ}K$ whether the substances are irradiated in the dry state or in frozen aqueous solution. Based on these results, it is assumed that the number of ESR centers produced by the secondary intermolecular radical reacions and stabilized in aqueous solutions may depend on the concentration of the solution, and the presence of water may facilitate the secondary radical reactions occuring in the solute molecules after heat treatment. Majority of the solute radicals above around $193^{circ}K$ are believed to react with oxygen to form peroxytype radicals. However, when the solution is subiected to heat-treatment at $265^{circ}K$ after irradiation at $195^{circ}K$ the peroxy-type resonance was not observed, suggestin that an appreciable amount of oxygen is condensed into the ice, at $77^{circ}K.$ in addition to the oxygen that has already been dissolved in solution and react with solute free radicals during the process of heat-treatment. When the solution contains $H_2O_2$, no water resonance but $HO_2$, type resonance was observed probably indicating that the radiation-induced OH radicals are trapped in $H_2O_2$ aggregates and react readily with $H_2O_2$ molecules to poroduce $HO_2$ type radicals even at $77^{circ}K.$.

• Journal of the Korean Magnetics Society
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• v.6 no.5
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• pp.298-304
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• 1996

We have manufactured FMR spectrometer over wide range(2-35 GHz). In order to test FMR spectrometer, res¬onance absorption has been measured of the standard sample DPPH. The Q vaules of absorption line are 189-1096. As a result, We noticed that FMR spectrometer has been manufactured well. FMR studies of MgFez04 single crystal have been performed at S, J, K-band. The resonance lines have been observed for the each orientation of (100) plane at 300 K. The values of the magnetic anisotropy constant $K_{1}$ and the spectroscopic spli tting g valule have been calculated from the ferromagnetic resonance curve, $-2.9{\times}10^{4}erg/cm^{3}$, 2.02 at 23.89 GHz, $-2.2{\times}10^{4}erg/cm^{3}$, 1.89 at 5.3 GHz and $-2.8{\times}10^{4}erg/cm^{3}$, 2.01 at 3.6 GHz.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2505-2511
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• 2014

Indium oxide nanocrystals ($In_2O_3$ NCs) with sizes of 5.5 nm-10 nm were synthesized by hot injection of the mixture precursors, indium acetate and oleic acid, into alcohol solution (1-octadecanol and 1-octadecence mixture). Field emission transmission electron microscopy (FE-TEM), High resolution X-Ray diffraction (X-ray), Nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy (FT-IR) were employed to investigate the size, surface molecular structure, and crystallinity of the synthesized $In_2O_3$ NCs. When covered by oleic acid as a capping group, the $In_2O_3$ NCs had a high crystallinity with a cubic structure, demonstrating a narrow size distribution. A high mobility of $2.51cm^2/V{\cdot}s$ and an on/off current ratio of about $1.0{\times}10^3$ were observed with an $In_2O_3$ NCs thin film transistor (TFT) device, where the channel layer of $In_2O_3$ NCs thin films were formed by a solution process of spin coating, cured at a relatively low temperature, $350^{\circ}C$. A size-dependent, non-monotonic trend on electron mobility was distinctly observed: the electron mobility increased from $0.43cm^2/V{\cdot}s$ for NCs with a 5.5 nm diameter to $2.51cm^2/V{\cdot}s$ for NCs with a diameter of 7.1 nm, and then decreased for NCs larger than 7.1 nm. This phenomenon is clearly explained by the combination of a smaller number of hops, a decrease in charging energy, and a decrease in electronic coupling with the increasing NC size, where the crossover diameter is estimated to be 7.1 nm. The decrease in electronic coupling proved to be the decisive factor giving rise to the decrease in the mobility associated with increasing size in the larger NCs above the crossover diameter.

• Journal of the Korean Magnetics Society
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• v.15 no.3
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• pp.177-180
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• 2005

Ferroelectric $LiTaO_3$ single crystals, grown by the Czochralski method, were thermally treated at temperature $1000^{\circ}C\;and\;1100^{\circ}C$. Electron paramagnetic resonance (EPR) study of stoichiometric $LiTaO_3$ and thermally treated $LiTaO_3$ crystals has been investigated by employing an X-band spectrometer. From the $Fe^{3+}$ EPR spectra, it turned out that there is no change of site location and local site symmetry around $Fe^{3+}$ impurity ion between stoichiometric and thermally treated $LiTaO_3$ single crystals. We confirmed that the ionic state of $Fe^{3+}$ ion changed after thermal treatment. The EPR parameters of $Fe^{3+}$ ion in $LiTaO_3$ single crystals are determined with effective spin Hamiltonian.

• Journal of the Korean Magnetics Society
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• v.21 no.6
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• pp.208-213
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• 2011

We calculated the EPR (electron paramagnetic resonance) line-shape function. The line-widths of a -doped single crystal was studied as a function of the temperature with 0.5 and 2 at. at a frequency of (X-band). The line-width decreases with increasing temperature, such temperature behavior of the line-width can indicate a motional narrowing of the spectrum, when impurity ions substitute for host ions in an off-center position, and thus there can be fast jumping of dipoles between several symmetrically equivalent configurations. Therefore, the present technique is considered to be more convenient to explain the resonant system as in the case of other optical transition problems.