• Korean Journal of Materials Research
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• v.22 no.2
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• pp.91-96
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• 2012

AC and ZnS modified $TiO_2$ composites (AC/ZnS/$TiO_2$) were prepared using a sol-gel method. The composite obtained was characterized by Brunauer-Emmett-Teller (BET) surface area measurements, X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis, scanning electron microscope (SEM) analysis, and according to the UV-vis absorption spectra (UV-vis). XRD patterns of the composites showed that the AC/ZnS/$TiO_2$ composites contain a typical single and clear anatase phase. The surface properties as observed by SEM present the characterization of the texture of the AC/ZnS/$TiO_2$ composites, showing a homogenous composition in the particles showing the micro-surface structures and morphology of the composites. The EDX spectra of the elemental identification showed the presence of C and Ti with Zn and S peaks for the AC/ZnS/$TiO_2$ composite. UV-vis patterns of the composites showed that these composites had greater photocatalytic activity under visible light irradiation. A rhodamine B (Rh.B) solution under visible light irradiation was used to determine the photocatalytic activity. The degradation of Rh.B was determined using UV/Vis spectrophotometry. An increase in the photocatalytic activity was observed. From the photocatalytic results, the excellent activity of the Y-fullerene/$TiO_2$ composites for the degradation of methylene blue under visible irradiation could be attributed to an increase in the photo-absorption effect caused by the ZnS and to the cooperative effect of the AC.

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1907-1914
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• 2010

A novel catalytic kinetic method is proposed for the determination of Se(IV), Se(VI) and total inorganic selenium in water based on the catalytic effect of Se(IV) on the reduction of bromate by p-nitrophenylhydrazine at pH 3.0. The generated bromine, $Br_2$ or $Cl_2$ plus $Br_2$ in 0.1 M NaCl (or NaBr) environment efficiently decolorized Calmagite and the reaction was monitored spectrophotometrically at 523 nm as a function of time. In this indicator reaction, bromide acted as an activator for the catalysis of selenium (IV) and a reducing agent for selenium (VI) at pH 3.0, which allowed the determination of total selenium. The fixed time method was adopted for the determination and speciation of inorganic selenium. Under the optimum conditions, the calibration graph are linear in the range 1 - 35 ${\mu}gL^{-1}$ of Se(IV) for the fixed time method at $25^{\circ}C$. The detection limit based on statistical $3S_{blank}$/m-criterion was 0.215 ${\mu}gL^{-1}$ for the fixed time method (7 min). All of the variables that affect the sensitivity at 523 nm were investigated, and the optimum conditions were established. The interference effect of various cations and anions on the Se (IV) determination was also studied. The selectivity of the selenium determination was greatly improved with the use of the strongly cation exchange resin such as Amberlite IR120 plus. The proposed kinetic method was validated statistically and through recovery studies in natural water samples. The RSDs for ten replicate measurements of 5, 15 and 25 ${\mu}gL^{-1}$ of Se(IV) and Se(VI) was changed between 2.1 - 4.85%. Analyses of a certified standard reference material (NIST SRM 1643e) for selenium using the fixed-time method showed that the proposed kinetic method has good accuracy. Se(IV), Se(VI) and total inorganic selenium in environmental water samples have been successfully determined by this method after selective reduction of Se(VI) to Se(IV).

• Journal of the Korean Chemical Society
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• v.51 no.2
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• pp.147-153
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• 2007

A simple, selective and highly sensitive flow injection catalytic method was presented for determination of ruthenium based on its catalytic effect on the oxidation of pyronin B by periodate in pH=1.0. The reaction rate is controlled specrophotometricaly by monitoring the dye absorbance at 555 nm. The optimized conditions make it possible to determine ruthenium in the ranges of 0.1-10.0 ng/mL (r2=0.9982) and 10.0-50.0 ng/mL (r2=0.9934) with a detection limit of 0.04 ng/mL and a sample rate of 30±5 samples/h. Relative standard deviation for the results of five replicate measurements does not exceed 1.44%. The proposed method has been successfully applied for quantitation of ultra trace amounts of ruthenium in some environmental and biological samples.

• Journal of the Korean Chemical Society
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• v.11 no.3
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• pp.111-116
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• 1967

A new alkaloid named Spirajine(m.p. 182~$184^{\circ}C$ $[{\alpha}]d^{19}+3.4^{\circ}$ in $CHCl_3$, $C_{23}H_{33}NO_3$, colorless prism) was isolated from the leaves of Spiraea Koreana Nakai (Spiraeceae) (Korean name "Chamjopab namu") which grows in the mountaineous area of Korea, by process of Scheme I (yields 0.13%). Another two unidentified alkaloids (not yet crystallized) were separated by the method of thin layer chromatography. (The Rf values of the two unidentified alkaloids were 0.66, 0.77, respectively and Spirajine 0.72) Spirajine were subjected to the structural investigation with the use of ultra violet and infra red spectrophotometry, and opical rotatory dispersion. The alkaloid contains two ketonic carbonyl groups, tertiary hydroxyl group, methyl groups, N-methyl group and both cyclohexane ring and cyclopentane ring.

• Current Photovoltaic Research
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• v.4 no.1
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• pp.25-29
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• 2016

$Eu^{3+}$-activated $MgMoO_4$ phosphor thin films were grown at $400^{\circ}C$ on quartz substrates by radio-frequency magnetron sputter deposition from a 15 mol% Eu-doped $MgMoO_4$ target. After the deposition, the phosphor thin films were annealed at several temperatures for 30 min in air. The influence of thermal annealing temperature on the structural and optical properties of $MgMoO_4:Eu^{3+}$ phosphor thin films was investigated by using X-ray diffraction (XRD), photoluminescence (PL), and ultraviolet-visible spectrophotometry. The transmittance, optical band gap, and intensities of the luminescence and excitation spectra of the thin films were found to depend on the thermal annealing temperature. The XRD patterns indicated that all the thin films had a monoclinic structure with a main (220) diffraction peak. The highest average transmittance of 91.3% in the wavelength range of 320~1100 nm was obtained for the phosphor thin film annealed at $800^{\circ}C$. At this annealing temperature the optical band gap energy was estimated as 4.83 eV. The emission and excitation spectra exhibited that the $MgMoO_4:Eu^{3+}$ phosphor thin films could be effectively excited by near ultraviolet (281 nm) light, and emitted the dominant 614 nm red light. The results show that increasing RTA temperature can enhance $Eu^{3+}$ emission and excitation intensity.

• Journal of dental hygiene science
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• v.19 no.4
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• pp.288-293
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• 2019

Background: Dental caries is one of several prevalent oral diseases caused by dental plaque biofilms. This study evaluated the anti-cariogenic effects of a bamboo salt (BS) and sodium fluoride (NaF) mixture on oral bacteria. Methods: The effects of several mixtures of NaF and BS on acid production, growth, and adhesion to glass beads of Streptococcus mutans, and their anti-cariogenic properties were investigated. The growth of S. mutans was measured according to optical density at 3, 6, 9, 12, 15, 18, and 24 hours after treatment using spectrophotometry at a wavelength of 600 nm, while pH was measured using a pH meter. Adhesion of S. mutans was measured according to the weight of glass beads from each group before and after incubation. Gene expression was measured using real-time polymerase chain reaction. Acid production and growth patterns of S. mutans were compared using repeated measures analysis of variance, followed by Scheffe's post-hoc test. The Kruskal-Wallis test was used to compare adhesion, followed by the Mann-Whitney test. Gene expression in the experimental and control samples was compared using the Student's t-test. Results: Growth, acid production, and adhesion of S. mutans were inhibited in all experimental groups. Expression of gft and fructosyltransferase in S. mutans was inhibited in all groups. A mixture of NaF and BS significantly reduced growth, acid production, adhesion, and gene expression of S. mutans compared with the other groups. Conclusion: Results of the present study demonstrated that a mixture of NaF and BS was useful as a mouth rinse in preventing dental caries.

• Journal of Preventive Medicine and Public Health
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• v.53 no.1
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• pp.29-36
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• 2020

Objectives: Prenatal cadmium (Cd) exposure may be associated with attention-deficit/hyperactivity disorder (ADHD) in children. Therefore, the objective of this study was to examine the relationship between Cd exposure during gestation and ADHD at 6 years of age. Methods: As part of an ongoing cohort study (the Environment and Development of Children study), 479 mother-child pairs from Seoul, Korea were included for analysis between 2008 and 2011. The whole blood concentration of Cd was analyzed using atomic absorption spectrophotometry. The parents were surveyed about ADHD behaviors in their children at age 6. Multivariable linear regression models were used to investigate the relationship between prenatal exposure to Cd and ADHD at 6 years of age. Results: Increased prenatal Cd concentrations were associated with increased scores for ADHD for girls, but not for boys, at age 6. A 2-fold increase in the prenatal Cd level was significantly associated with a 22.3% (95% confidence interval, 11.6 to 34.1) increase in ADHD in girls at 6 years of age, as indicated by the linear regression model. Conclusions: Our results identified significant associations between prenatal Cd exposure and ADHD scores in 6-year-old girls.

• The Journal of Advanced Prosthodontics
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• v.9 no.3
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• pp.200-207
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• 2017

PURPOSE. In this study, three bioceramic materials, [IPS Empress CAD (Ivoclar), IPS e.max CAD (Ivoclar), and Lava Ultimate CAD (3M ESPE)] were treated with three commercial mouthrinses [Listerine, Tantum Verde, and Klorhex]; and changes in colour reflectance and surface roughness values were then quantitatively assessed. MATERIALS AND METHODS. One hundred and twenty ceramic samples, with dimensions of $2{\times}12{\times}14mm$, were prepared and divided into nine sample groups, except three control samples. The samples were immersed in the mouthrinse solutions for 120 hrs, and changes in colour reflectance and surface roughness values were measured by UV light spectrophotometry (Vita Easyshade; VITA Zahnfabrik) and by profilometer device (MitutoyoSurftest SJ-301), respectively. The change of surface roughness was inspected by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). RESULTS. There was a positive correlation between the ${\Delta}E$ and increase in the surface roughness. Two of the ceramic materials, IPS Empress and Lava Ultimate, were affected significantly by the treatment of the mouthrinse solutions (P<.05). The most affecting solution was Tantum Verde and the most affected material was Lava Ultimate. As expected, the most resistant material to ${\Delta}E$ and chemical corrosion was IPS e max CAD among the materials used. CONCLUSION. This work implied that mouthrinse with lower alcohol content had less deteriorating effect on colour and on the surface morphology of the bioceramic materials.

• Analytical Science and Technology
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• v.6 no.4
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• pp.405-409
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• 1993

Spectrophotometric assay for memantine HCl was developed by using sodium 1-(4-methoxypheyl) cinnamonitrile-2-sulfonate (MPCN) as an UV labelling reagent. The optimum derivatizing condition was obtained by incubation for 30 min at pH 5.0 in the presence of 20-fold molar excess of the labelling reagent. The absorbance of reaction product was measured at 324.5 nm and detection limit was $0.43{\mu}g/ml$. A linear range was $5.0{\times}10^{-6}{\sim}6.5{\times}10^{-5}M$ of memantine HCl. The linear regression analysis of absorbance at various drug concentration was r=0.9998 (n=6). When applied to memantine HCl ampule and tablet, it gave the mean contents of $100.08{\pm}0.72%$ and $99.75{\pm}0.77%$, respectively.

• Analytical Science and Technology
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• v.12 no.5
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• pp.355-359
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• 1999

Trace cadmium was determined in urine by flame and nameless AAS. Inflame method, cadmium was extracted into MIBK from Cd-DDTC complex. In flameless method, samples were pretreated with 1%, Triton X-100. 1% $HNO_3$ and matrix modifier $Pd(NO_3)_2$. Analysis of cadmium was, performed at $450-750^{\circ}C$ ashing temperature by use of pyrocoated tubes. Results of analysis, flameless method superior in sample treatment and reproducibility to flame method and highest absorbance was obtained at $550^{\circ}C$ ashing temperature. 100 mg/L $Pd(NO_3)_2$ concentration. Proposed method were applied to the determination of cadmium in standard urine Lononorm-Metalle 3.