Hee-Dong Kang

Interaction between the surface of the silver nanoparticles prepared by γ-irradiation and organic molecules containing thiol group

The colloidal silver nanoparticles were prepared by the γ-irradiation of silver nitrate (AgNO3) in a mixture solution of water and 2-propanol in the presence of poly(vinylpyrrolidone) as a colloidal stabilizer. The Ag colloids obtained by γ-irradiation were characterized by use of XRD and TEM. The surface of the Ag colloids were modified by use of mercaptosuccinic acid (MSA), (d)-cysteine (Cys), and (l)-Cys, respectively. The MSA and (l)-Cys-capped Ag colloids were aggregated because of hydrogen bonding of the carboxylic acid and amino acid group, respectively. From the analysis by CD spectroscopy, it was shown that chiral-enhanced phenomena were obtained in (l)- and (d)-Cys-capped Ag colloids.

Adsorption of uranium ions by resins with amidoxime and amidoxime/carboxyl group prepared by radiation-induced polymerization

Abstract In order to recover uranium ions from seawater, chelate-type resins with amidoxime and amidoxime/carboxylic acid groups were prepared by radiation-induced polymerization of acrylonitrile (AN) and AN/acrylic acid and by subsequent amidoximation of cyano group of poly(AN), respectively. The resins were characterized by FT–IR, FT–Raman, solid-state 13 C-NMR, SEM, and elemental analysis, respectively. The adsorption rate of uranium ion by resins with the amidoxime/carboxylic acid group were higher than that of resins with the amidoxime group. The adsorption of uranium ions in artificial seawater to chelate-type resins was also examined.

Daily intakes of naturally occurring radioisotopes in typical Korean foods

The concentrations of naturally occurring radioisotopes ((232)Th, (228)Th, (230)Th, (228)Ra, (226)Ra, and (40)K) in typical Korean foods were evaluated. The daily intakes of these radioisotopes were calculated by comparing concentrations in typical Korean foods and the daily consumption rates of these foods. Daily intakes were as follows: (232)Th, 0.00-0.23; (228)Th, 0.00-2.04; (230)Th, 0.00-0.26; (228)Ra, 0.02-2.73; (226)Ra, 0.01-4.37 mBq/day; and (40)K, 0.01-5.71 Bq/day. The total daily intake of the naturally occurring radioisotopes measured in this study from food was 39.46 Bq/day. The total annual internal dose resulting from ingestion of radioisotopes in food was 109.83 muSv/y, and the radioisotope with the highest daily intake was (40)K. These values were same level compiled in other countries.

Luminescence properties of a CsI crystal doped with Eu2+ ions

Abstract Optical properties of a CsI crystal doped with Eu 2+ ions are investigated by absorption, emission and excitation spectroscopy. Two absorption bands with a fine structure are observed at 277 and 363 nm, and an emission band is observed at 445 nm. These bands are caused by the electronic transition between 4f 7 and 4f 6 5d configurations. The crystal field parameter 10 Dq of Eu 2+ in CsI is estimated to be 8600 cm −1 . Comparison with the results obtained in other alkali halides is made.

Nationwide survey of radon levels in Korea

Abstract— A nationwide radon survey was conducted to provide data on the annual average indoor radon concentration in Korean homes. This survey also provided data on the variation of radon concentration with season, house type, and building age. The arithmetic mean (AM) of annual radon concentration in Korean homes was 53.4 ± 57.5 Bq m−3. The indoor radon concentration showed a lognormal distribution with a geometric mean (GM) and its standard deviation (GSD) of 43.3 ± 1.8 Bq m−3. The radon concentrations in the traditional Korean- style houses were about two times higher than those in apartments and row houses. The average annual outdoor radon concentration was 23.3 Bq m−3. The average annual effective dose to the general public from radon was 1.63 mSv y−1.

Luminescence and Scintillation Properties of a CeBr

Crystal growth, luminescence, and scintillation properties of a CeBr3 crystal are presented. The crystal was grown with Bridgman method using two-zone transparent furnace and cut to Oslash10 times 10 mm3. The investigation of luminescence and scintillation properties of the CeBr3 was performed under the excitation by ultraviolet and gamma-rays at room temperature. The emission spectrum of the CeBr3 was observed in the range of near ultraviolet to violet, which is due to the 5d rarr 4f transition of Ce3+. The decay time of the Ce3+ emission was measured to be approximately 20 ns. The energy resolution of the CeBr3 single crystal was obtained to be 4.9% for the 137Cs 662 keV gamma-rays. The relative signal of the CeBr3 crystal by the 137Cs gamma-rays is about three times higher than that of a CsI:Tl crystal when a bi-alkali PMT was used. The nonproportionality in the gamma-ray energy of the crystal was also measured. The study showed that the CeBr3 crystal is the promising candidate for the PET application. The CeBr3 crystal with high light output and fast decay time affords its use for the particle detection in a high counting rate environment such as nuclear and high-energy physics.

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Three different cation-exchange membranes with carboxylic acid, phosphoric acid, and sulfonic acid groups, and one anion-exchange membrane with a triethylamine group were prepared by radiation-induced graft polymerization. The maximum capacities of the carboxylic acid, phosphoric acid, sulfonic acid, and triethylamine groups were 3.0, 2.30, 2.43, and 1.42 mmol/g, respectively. The physico-chemical properties of the polyalkene non-woven fabric membrane with four different ion-exchange groups were examined by thermogravimetric analysis, X-ray photoelectron spectrometry (XPS), and scanning electron microscopy. The prepared ion-exchange membrane was applied to the removal of terephthalic acid in dyeing wastewater.

Single Crystal

We present the luminescent and scintillation characteristics of CsI:CO3 single crystals. The CsI:CO3 single crystals were grown by using Czochralski method for different concentrations of CO3 from 0.007 to 0.1 mole%. The crystals were cut into a size of 10 mm times 10 mm times 5 mm. The luminescent characteristics were measured with X-rays to study the emission spectra of the CsI:CO3 crystals. The scintillation properties of the CsI:CO3 crystals such as fluorescence decay time, energy resolution, pulse height spectra, proportionality, and relative light output were studied by using various gamma-ray sources with a photomultiplier tube (PMT) at room temperature. The absolute light outputs of the crystals were also measured with an avalanche photo-diode (APD).

Preparation and characterization of polyalkene membranes modified with four different ion-exchange groups by radiation-induced graft polymerization.

Pd-M (M=Ag and Ni) and Pt-M (Ru and Ni) alloy colloids were successfully prepared in aqueous solution by γ-irradiation using poly(vinylpyrrolidone), PVP, as stabilizer. The PVP-stabilized Pd-M and Pt-M nanoparticles were characterized by UV-Vis spectroscopy, Transmission Electron Microscopy (TEM) and Electrophoretic Light Scattering (ELS) analysis. The influence of molecular size of the PVP on the size and size distribution of the alloy nanoparticles was followed. Pd-Ag nanoparticles were formed by employing PVP with different molecular weights. The size of Pd-Ag alloy nanoparticles was determined by TEM photograph and ELS spectra, respectively. From the TEM photographs, the average diameter of Pd-Ag nanoparticles does not show strong dependence on the molecular weight of the PVP. On the other hand, the average diameter of Pd-Ag alloy colloids prepared by PVP with Mw=40,000 was consistently larger than that of Pd-Ag alloy colloids prepared by PVP with Mw=10,000. A plausible scheme is given to explaining this. The size and size distribution of Pt-M (Ru and Ni) alloy colloids are presented.

The Growth and Scintillation Characteristics of CsI:CO

We grew a Gd-doped lead chloride single crystal by the Bridgman method and investigated scintillation properties of the crystals at low temperature. We measured the relative light yield, energy resolution, fluorescence decay time, and proportionality of the crystals for the gamma-ray at low temperature. The energy resolution is measured to be 25.6% for the137Cs 662 keV gamma-ray, and the fluorescence decay time of the crystal is composed of two components with decay times of 1.35 and 6.20 mus at 173 K.