• Toxicological Research
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• v.30 no.3
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• pp.169-178
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• 2014

This review covers general information regarding the green synthesis of antibacterial silver nanoparticles. Owing to their antibacterial properties, silver nanoparticles are widely used in many areas, especially biomedical applications. In green synthesis practices, the chemical reducing agents are eliminated, and biological entities are utilized to convert silver ions to silver nanoparticles. Among the various biological entities, natural plant extracts have emerged as green reducing agents, providing eco-friendly routes for the preparation of silver nanomaterials. The most obvious merits of green synthesis are the increased biocompatibility of the resulting silver nanoparticles and the ease with which the reaction can be carried out. This review summarizes some of the plant extracts that are used to produce antibacterial silver nanoparticles. Additionally, background information regarding the green synthesis and antibacterial activity of silver nanoparticles is provided. Finally, the toxicological aspects of silver nanoparticles are briefly mentioned.

• Mass Spectrometry Letters
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• v.3 no.2
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• pp.54-57
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• 2012

Mass spectrometric analysis was carried out using multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) for the precise and accurate determination of the isotope ratios of ultratrace levels of uranium dissolved in 3% $HNO_3$. We used the certified reference material (CRM) 112-A at a trace level of 100 pg/mL for the uranium isotopic measurement. Multiple collectors were utilized for the simultaneous measurement of uranium isotopes to reduce the signal uncertainty due to variations in the ion beam intensity over time. Mass bias correction was applied to the measured U isotopes to improve the precision and accuracy. Furthermore, elemental standard solution with certified values of platinum, iridium, gold, and thallium dissolved in 3% $HNO_3$ were analyzed to investigate the formation rates of the polyatomic ions of $Ir^{40}$ $Ar^+$, $Pt^{40}$ $Ar^+$, $Tl^{40}$ $Ar^+$, $Au^{40}$ $Ar^+$ for the concentration range of 50-400 pg/mL. Those polyatomic ions have mass-to-charge ratios in the 230-245 m/z region that it would contribute to the increase of background intensity of uranium, thorium, plutonium, and americium isotopes. The effect of the polyatomic ion interference on uranium isotope measurement has been estimated.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.16
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• pp.6773-6779
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• 2014

Background: Nanotechnology opens new applications in many fields including medicine. Among all metallic nanoparticles, silver nanoparticles (silver NPS) have proved to be the most effective against a large variety of organisms including toxic cyanobacteria. Materials and Methods: Silver NPs were biosynthesized in vivo with different alga species namely, Spirulina piatensis, Chlorella vulgaris and Scenedesmus oh/iquus following two scenarios. First: by suspending a thoroughly washed algae biomass in 1 mM aqueous $AgN0_3$ solution. Second: by culturing them individually in culture media containing the same concentration of $AgN0_3$. Silver NPs were characterized using UV-Vis spectroscopy, transmission electron microscopy (TEM), energy dispersive analysis (EDX) and Fourier transform infra-red (FfIR) spectroscopy. The biosynthesized silver NPs were tested for cytotoxic activity against a cancer promoter cyanobacteruim Microcystis aeruginosa, considering effects on cell viability and chlorophyll content. Results: The surface plasmon band indicated the biosynthesis of silver NPs at ~400 nm. Transmission electron microscopy (TEM) revealed that the silver NPs had a mean average size below 100 nm. Energy-dispersive analysis X-ray (EDX) spectra confirmed the presence of silver element. FfIR spectral analyses suggested that proteins and or polysaccharides may be responsible for the biosynthesis of silver NPs and (-COO-) of carboxylate ions is responsible for stabilizing them. The toxic potentialities ofthe biosynthesized silver NPs against the cancer promoter cyanobacterium, Microcystis aeruginosa showed high reduction in viable cells count and the total chlorophyll content. Conclusions: The potential activity of the biosynthesized silver NPs from the studied algae species against Microcystis aernginosa cells is expected to be mainly mediated by the release of silver ions (Ag+) from the particle surface and bioactive compounds as indicated by FfIR analysis.

• Korean Journal of Environmental Agriculture
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• v.33 no.2
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• pp.69-77
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• 2014

BACKGROUND: The purpose of this study was to investigate the effects of clothianidin on the soil in terms of clothianidin dissipation and degradation to evaluate its safety in order to provide an analytical foundation for clothianidin and the 5 metabolites related to it. METHODS AND RESULTS: High-performance liquid chromatography(HPLC) was used to separate clothianidin and its metabolites in this study. In soil, after suppressing dissociation-proned ions with weak alkalic $NH_4OH$ and extracting the metabolites with methanol, clothianidin, Methylaminoimidazole(MAI), Methylnitroguanidine(MNG), Thiazolylmethylurea(TZMU) and Thiazolylnitroguanidine(TZNG). Thiazolylmethylguanidine(TMG) were extracted with the addition of neutral $NH_4OAC$ to increasing the intensity of ions. Compounding elements were separated by using Hydrometrix ($ChemElut^{TM}$) and ion-exchanging Solid-phase extraction(SPE) Strong cation-exchanger(SCX) and C18 were used. The recovery rates of clothianidin and 5 metabolites in soil and water ranged from 87.4% to 104.3%. A standard deviation of our analysis for the soil and water samples were less than 5%. CONCLUSION: Well accepted detection limits for clothianidin and 5 metabolites in soil samples based on a dissipation analysis is 0.005 mg/kg and 0.001 mg/L in water samples. The dissipation concentration of this study was decided to be enough to evaluate the dissipation levels of clothianidin and its metabolites.

• Journal of Radiation Protection and Research
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• v.41 no.3
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• pp.222-228
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• 2016

Background: We are developing a small size dosimeter for dose estimation in particle therapies. The developed dosimeter is an optical fiber based dosimeter mounting an radiation induced luminescence material, such as an OSL or a scintillator, at a tip. These materials generally suffer from the quenching effect under high LET particle irradiation. Materials and Methods: We fabricated two types of the small size dosimeters. They used an OSL material Eu:BaFBr and a BGO scintillator. Carbon ions were irradiated into the fabricated dosimeters at Heavy Ion Medical Accelerator in Chiba (HIMAC). The small size dosimeters were set behind the water equivalent acrylic phantom. Bragg peak was observed by changing the phantom thickness. An ion chamber was also placed near the small size dosimeters as a reference. Results and Discussion: Eu:BaFBr and BGO dosimeters showed a Bragg peak at the same thickness as the ion chamber. Under high LET particle irradiation, the response of the luminescence-based small size dosimeters deteriorated compared with that of the ion chamber due to the quenching effect. We confirmed the luminescence efficiency of Eu:BaFBr and BGO decrease with the LET. The reduction coefficient of luminescence efficiency was different between the BGO and the Eu:BaFBr. The LET can be determined from the luminescence ratio between Eu:BaFBr and BGO, and the dosimeter response can be corrected. Conclusion: We evaluated the LET dependence of the luminescence efficiency of the BGO and Eu:BaFBr as the quenching effect. We propose and discuss the correction of the quenching effect using the signal intensity ratio of the both materials. Although the correction precision is not sufficient, feasibility of the proposed correction method is proved through basic experiments.

• Journal of Radiation Protection and Research
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• v.41 no.4
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• pp.344-349
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• 2016

Background: Carbon ion therapy has achieved satisfactory results. However, patients have a risk to get a secondary cancer. In order to estimate the risk, it is essential to understand particle transportation and nuclear reactions in the patient's body. The particle transport Monte Carlo simulation code is a useful tool to understand them. Since the code validation for heavy ion incident reactions is not enough, the experimental data of the elementary reaction processes are needed. Materials and Methods: We measured neutron production double-differential cross-sections (DDXs) on a carbon bombarded with 430 MeV/nucleon carbon beam at PH2 beam line of HIMAC facility in NIRS. Neutrons produced in the target were measured with NE213 liquid organic scintillators located at six angles of 15, 30, 45, 60, 75, and $90^{\circ}$. Results and Discussion: Neutron production double-differential cross-sections for carbon bombarded with 430 MeV/nucleon carbon ions were measured by the time-of-flight method with NE213 liquid organic scintillators at six angles of 15, 30, 45, 60, 75, and $90^{\circ}$. The cross sections were obtained from 1 MeV to several hundred MeV. The experimental data were compared with calculated results obtained by Monte Carlo simulation codes PHITS, Geant4, and FLUKA. Conclusion: PHITS was able to reproduce neutron production for elementary processes of carbon-carbon reaction precisely the best of three codes.

• Journal of Ginseng Research
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• v.41 no.1
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• pp.78-84
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• 2017

Background: In the present study, metabolite profiles of ginsenosides Rk1 and Rg5 from red ginseng or red notoginseng in zebrafish were qualitatively analyzed with ultraperformance liquid chromatography/quadrupole-time-of-flight MS, and the possible metabolic were pathways proposed. Methods: After exposing to zebrafish for 24 h, we determined the metabolites of ginsenosides Rk1 and Rg5. The chromatography was accomplished on UPLC BEH C18 column using a binary gradient elution of 0.1% formic acetonitrile-0.1% formic acid water. The quasimolecular ions of compounds were analyzed in the negative mode. With reference to quasimolecular ions and MS2 spectra, by comparing with reference standards and matching the empirical molecular formula with that of known published compounds, and then the potential structures of metabolites of ginsenosides Rk1 and Rg5 were acquired. Results: Four and seven metabolites of ginsenoside Rk1 and ginsenoside Rg5, respectively, were identified in zebrafish. The mechanisms involved were further deduced to be desugarization, glucuronidation, sulfation, and dehydroxymethylation pathways. Dehydroxylation and loss of C-17 residue were also metabolic pathways of ginsenoside Rg5 in zebrafish. Conclusion: Loss of glucose at position C-3 and glucuronidation at position C-12 in zebrafish were regarded as the primary physiological processes of ginsenosides Rk1 and Rg5.

• Journal of environmental and Sanitary engineering
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• v.19 no.4 s.54
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• pp.9-18
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• 2004

In this study, the observation data for the yellow sandy dust phenomena from the year 1999 to 2003 at background sites in Korea were collected at Global Atmospheric Observatory at An-Myeon island and its temporal variation were analyzed. The chemical characteristics of the fine particles were also analyzed in order to evaluate sources of the yellow sandy dust particles. The results showed that the monthly average mass concentration of the fine particles was the highest in springtime and the lowest in summertime in general. The magnitude of its variation was also the highest in March in which the occurrence of yellow sandy dust was the most frequent and thus the number of samples was the largest, while the lowest in June through September. The yearly variation of ion components contributions to the total mass concentration of the fine particles was slowly decreasing, showing that $63\%$ in 1999, $59\%$ in 2000 and $56\%$ in 2003. The most prevalent ion components in the fine particles were found to be $NO_3$ and $SO_4^{2-}$, which are known to be source materials of acidic precipitation, and $NH_4^+$, a neutralizing material of the acid precipitation. Relative proportion of metal components in the fine particles was calculated as $14\%$ in average, and their concentrations are in an order of Fe > Al > Na > Ca > Zn > Pb > Cu > Mn > Ni > Cd > Cr > Co > U. The results indicated that main sources of the metals was soil-originated Fe, Al, Ca, and Mg, and the contribution of anthropogenic air Pollution-originated Zn, Pb, Cu, Mn were also high and keep slightly increasing. Statistical analysis showed that the chemical components could be divided into soil-originated group of Mg, Al, Ca, Fe, and Mn and air pollution-originated group of $NO_3$, Zn, Pb, and they are occupying more than $60\%$of all the components in the dusty sand. The results explain that An-Myeon island is more influenced by soil-originated source than ocean-originated one and also the influencing strength of anthropogenic poilution-originated source is less than $50\%$ of that of soil-originated sources. Compared to non-yellow sandy period, the yellow sandy dust period showed that the amounts of soil-originated $Mg^{2+}$ and $Ca^{2+}$ and ocean-originated $Na^+$ and $Cl^-$ were increased to more than double and the metals of Mg, Al, Ca, Fe were also highly increased, while micro metal components such as Pb, Cd, Zn, which have a tendency of concentrating in air, were either decreased or maintained at nearly constant level. In the period of yellow sandy dust, a strong positive correlation was observed between water soluble ions and between metals in terms of its concentration, respectively. Factor analysis showed that the first group being comprised of about $43\%$ of the total inorganic components was affected by soil and they are ions of $Na^+,\;Mg^{2+}\;and\;Ca^{2+}$ and metals of Na, Fe, Mn and Ni. The result also showed that the metals of Mg and Cr were classified as second group and they were also highly affected by soil sources.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.100-101
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• 2012

The plasma damage free and room temperature processedthin film deposition technology is essential for realization of various next generation organic microelectronic devices such as flexible AMOLED display, flexible OLED lighting, and organic photovoltaic cells because characteristics of fragile organic materials in the plasma process and low glass transition temperatures (Tg) of polymer substrate. In case of directly deposition of metal oxide thin films (including transparent conductive oxide (TCO) and amorphous oxide semiconductor (AOS)) on the organic layers, plasma damages against to the organic materials is fatal. This damage is believed to be originated mainly from high energy energetic particles during the sputtering process such as negative oxygen ions, reflected neutrals by reflection of plasma background gas at the target surface, sputtered atoms, bulk plasma ions, and secondary electrons. To solve this problem, we developed the NBAS (Neutral Beam Assisted Sputtering) process as a plasma damage free and room temperature processed sputtering technology. As a result, electro-optical properties of NBAS processed ITO thin film showed resistivity of $4.0{\times}10^{-4}{\Omega}{\cdot}m$ and high transmittance (>90% at 550 nm) with nano- crystalline structure at room temperature process. Furthermore, in the experiment result of directly deposition of TCO top anode on the inverted structure OLED cell, it is verified that NBAS TCO deposition process does not damages to the underlying organic layers. In case of deposition of transparent conductive oxide (TCO) thin film on the plastic polymer substrate, the room temperature processed sputtering coating of high quality TCO thin film is required. During the sputtering process with higher density plasma, the energetic particles contribute self supplying of activation & crystallization energy without any additional heating and post-annealing and forminga high quality TCO thin film. However, negative oxygen ions which generated from sputteringtarget surface by electron attachment are accelerated to high energy by induced cathode self-bias. Thus the high energy negative oxygen ions can lead to critical physical bombardment damages to forming oxide thin film and this effect does not recover in room temperature process without post thermal annealing. To salve the inherent limitation of plasma sputtering, we have been developed the Magnetic Field Shielded Sputtering (MFSS) process as the high quality oxide thin film deposition process at room temperature. The MFSS process is effectively eliminate or suppress the negative oxygen ions bombardment damage by the plasma limiter which composed permanent magnet array. As a result, electro-optical properties of MFSS processed ITO thin film (resistivity $3.9{\times}10^{-4}{\Omega}{\cdot}cm$, transmittance 95% at 550 nm) have approachedthose of a high temperature DC magnetron sputtering (DMS) ITO thin film were. Also, AOS (a-IGZO) TFTs fabricated by MFSS process without higher temperature post annealing showed very comparable electrical performance with those by DMS process with $400^{\circ}C$ post annealing. They are important to note that the bombardment of a negative oxygen ion which is accelerated by dc self-bias during rf sputtering could degrade the electrical performance of ITO electrodes and a-IGZO TFTs. Finally, we found that reduction of damage from the high energy negative oxygen ions bombardment drives improvement of crystalline structure in the ITO thin film and suppression of the sub-gab states in a-IGZO semiconductor thin film. For realization of organic flexible electronic devices based on plastic substrates, gas barrier coatings are required to prevent the permeation of water and oxygen because organic materials are highly susceptible to water and oxygen. In particular, high efficiency flexible AMOLEDs needs an extremely low water vapor transition rate (WVTR) of $1{\times}10^{-6}gm^{-2}day^{-1}$. The key factor in high quality inorganic gas barrier formation for achieving the very low WVTR required (under ${\sim}10^{-6}gm^{-2}day^{-1}$) is the suppression of nano-sized defect sites and gas diffusion pathways among the grain boundaries. For formation of high quality single inorganic gas barrier layer, we developed high density nano-structured Al2O3 single gas barrier layer usinga NBAS process. The NBAS process can continuously change crystalline structures from an amorphous phase to a nano- crystalline phase with various grain sizes in a single inorganic thin film. As a result, the water vapor transmission rates (WVTR) of the NBAS processed $Al_2O_3$ gas barrier film have improved order of magnitude compared with that of conventional $Al_2O_3$ layers made by the RF magnetron sputteringprocess under the same sputtering conditions; the WVTR of the NBAS processed $Al_2O_3$ gas barrier film was about $5{\times}10^{-6}g/m^2/day$ by just single layer.

• Journal of Korean Society on Water Environment
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• v.21 no.1
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• pp.66-72
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• 2005

Effect of the pH, molar ratio of Cu(II)/EDTA, concentration of Cu(II)-EDTA and ionic strength on the photocatalytic oxidation(PCO) of Cu(II)-EDTA in solar light was studied in this work. Experimental results in this work were compared with previous results obtained with UV-lamp. In the kinetics, Cu(II)-EDTA decomposition was favorable below neutral pH. The removal of Cu(II) and DOC was favorable as $TiO_2$ dosage increased. The initial rate for the decomplexation of Cu(II)-EDTA linearly increased as the concentration of Cu(II)-EDTA increased. The removal of Cu(II) and DOC was not much affected by variation of ionic strength with $NaClO_4$ as a background ion while much reduction was observed in the presence of background ions having higher formal charges. The removal trend of Cu(II) and DOC with variation of ionic strength and concentration of Cu(II)-EDTA in solar light was similar with that in UV light. Variation of the molar ratio of Cu(II)/EDTA showed a negligible effect on the removal of both Cu(II) and DOC. However, removal of both Cu(II) and DOC was two-times greater than that previous results obtained with UV light.