• Korean Chemical Engineering Research
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• v.61 no.3
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• pp.463-471
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• 2023

Nitrogen-rich carbon dots (NDots) were synthesized by using uric acid as carbon and nitrogen sources. The as-synthesized NDots showed strong dual emissions at 420 nm and 510 nm with excitation at 350 nm and 460 nm, respectively. The physicochemical analyses such as X-ray photoelectron spectroscopy, Transmission electron microscopy and Fourier transform infrared spectroscopy were used to analyze the chemical, physical and morphological structures of NDots. The as-synthesized NDots exhibited wide linear range (0-100 µM) and very low detection limit (124 nM) in Ag⁺ ion sensing. In addition, Ag⁺ saturated NDots could be used as an EDTA sensor by the EDTA induced PL recovery.

• Horticultural Science & Technology
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• v.33 no.3
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• pp.356-363
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• 2015

This study examined the effects of different day/night temperature regimes or silver ion on growth and flowering of passion fruit 'Tai-nung No.1'. Low temperature treatment ($20/15^{\circ}C$) caused passion fruit cultivar 'Tai-nung No.1' to fail to flower. Flowering induction occurred within a temperature range of $20-30^{\circ}C$, with no significant difference in the days to first flower bud and the total number of flower buds between plants grown at $30/25^{\circ}C$ and $25/20^{\circ}C$. However, plants grown at $30/25^{\circ}C$ exhibited their first flower buds set on the higher nodes and had higher abortion rates of flower buds than those at $25/20^{\circ}C$. Plants grown at $30/25^{\circ}C$ had the most rapid growth and the shortest plastochron. We also evaluated the effect of the ethylene response inhibitors silver nitrate ($AgNO_3$) and silver thiosulfate (STS) on growth and flowering of potted passion fruit 'Tai-nung No.1', when they were exposed to low temperature conditions ($20/15^{\circ}C$) following chemical treatments ($AgNO_3$ or STS, at 0.5 or 1.0 mM). $AgNO_3$ and STS treatments induced flower formation and initial flower bud formation within approximately two weeks at $20/15^{\circ}C$ whereas non-treated control plants exhibited no flower formation. ACC content and activity of ACC oxidase in the leaves of passion fruit 'Tai-nung No.1'exposed to low temperature conditions ($20/15^{\circ}C$) were significantly inhibited by the ethylene inhibitor treatments. These results indicate that ethylene, which is produced under low temperature conditions, plays an important role in inhibiting flower formation in passion fruit.

• Toxicological Research
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• v.35 no.3
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• pp.257-270
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• 2019

Silver nanoparticles (AgNPs) have been widely used in a variety of applications in innovative development; consequently, people are more exposed to this particle. Growing concern about toxicity from AgNP exposure has attracted greater attention, while questions about nanosilver-responsive genes and consequences for human health remain unanswered. By considering early detection and prevention of nanotoxicology at the genetic level, this study aimed to identify 1) changes in gene expression levels that could be potential indicators for AgNP toxicity and 2) morphological phenotypes correlating to toxicity of HepG2 cells. To detect possible nanosilver-responsive genes in xenogenic targeted organs, a comprehensive systematic literature review of changes in gene expression in HepG2 cells after AgNP exposure and in silico method, connection up- and down-regulation expression analysis of microarrays (CU-DREAM), were performed. In addition, cells were extracted and processed for transmission electron microscopy to examine ultrastructural alterations. From the Gene Expression Omnibus (GEO) Series database, we selected genes that were up- and down-regulated in AgNPs, but not up- and down-regulated in silver ion exposed cells, as nanosilver-responsive genes. HepG2 cells in the AgNP-treated group showed distinct ultrastructural alterations. Our results suggested potential representative gene data after AgNPs exposure provide insight into assessment and prediction of toxicity from nanosilver exposure.

• Electrical & Electronic Materials
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• v.7 no.2
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• pp.100-106
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• 1994

A bilayer film consisting of a layer of a-Se$_{75}$ Ge$_{25}$ with a surface layer of silver -100[.angs.] thick and a monolayer film of a-Se$_{75}$ Ge$_{25}$ are irradiated with 9[keV] Ga$^{+}$ ion beam. The Ga$^{+}$ ion (10$^{16}$ [ions/cm$^{2}$] exposed a-Se$_{75}$ Ge$_{25}$ and Ag/a-Se$_{75}$ Ge$_{25}$ thin films show an increase in optical absorption, and the absorption edge on irradiation with shifts toward longer wavelength. The shift toward longer wavelength called a "darkening effect" is observed also in film exposure to optical radiation(4.5*10$^{20}$ [photons/cm$^{2}$]). The 0.3[eV] edge shift for ion irradiation films is about twice to that obtained on irradiation with photons. These large changes are primarily due to structural changes, which lead to high etch selectivity and high sensitivity.

• Bulletin of the Korean Chemical Society
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• v.24 no.7
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• pp.948-952
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• 2003

New approach for the determination of Ag(I) ion was performed by using a carbon paste electrode (CPE) containing N,N'-Diphenyl oxamide (DPO) with anodic stripping voltammetry. The CMEs have been prepared by making carbon paste mixtures containing an appropriate amount of DPO salt coated onto graphite particles to analyze trace metal ions via complexation followed by stripping voltammetry. Various experimental parameters affecting the response, such as pH, deposition time, temperature, and electrode composition, were carefully optimized. Using differential pulse anodic stripping voltammetry, the logarithmic linear response range for the Ag(I) ion was 1.0 × $10^{-7}$ - 5.0 × $10^{-9}$ M at the deposition time of 10 min, with the detection limit was 7.0 × $10^{-10}$ M. The detection limit adopted from anodic stripping differential pulse voltammetry was 7.0 × $10^{-10}$ M for silver and the relative standard deviation was ± 3.2% at a 5.0 × $10^{-8}$ M of Ag(I) ion (n = 7). The proposed electrode shows a very good selectivity for Ag(I) in a standard solution containing several metals at optimized conditions.

• Bulletin of the Korean Chemical Society
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• v.8 no.2
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• pp.69-72
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• 1987

The structures of dehydrated $Ag_9Cs_3$-A treated with hydrogen gas at three different temperatures have been determined by single-crystal X-ray diffraction techniques. Their structures were solved and refined in the cubic space group Pm3m at 23(1) $^{\circ}C$. All crystals were ion exchanged in flowing streams of aqueous $AgNO_3$/$CsNO_3$ with a mole ratio 1:3.0 to achieve the desired crystal composition. The structures treated with hydrogen at $23^{\circ}C(a=12.288(1)\;{\AA})\;and\;310^{\circ}C(a=12.291(2)\;{\AA})$ refined to the final error indices R1 = 0.091 and R2 = 0.079, and 0.065 and 0.073, respectively, using the 216 and 227 reflections, respectively, for which I >3${\sigma}$(I). In both of these structures, eight $Ag^+$ ions are found nearly at 6-ring centers, and three $Cs^+$ ions lie at the centers of the 8-rings at sites of $D_{4h}$ symmetry. One $Ag^{\circ}atom$, presumably formed from the reduction of a $Ag^+$ ion by an oxide ion of a residual water molecule or of the zeolite framework during the dehydration process, is retained within the zeolite, perhaps in a cluster. In these two structures hydrogen gas could not enter the zeolite to reduce the $Ag^+$ ions because the large $Cs^+$ ions blocked all the 8-windows. However, hydrogen could slowly diffuse into the zeolite and was able to reach and to reduce about half of the $Ag^+$ ions in the structure only at high temperature ($470^{\circ}C$). The silver atoms produced migrated out of the zeolite framework, and the protons generated led to substantial crystal damage.

• Applied Chemistry for Engineering
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• v.32 no.4
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• pp.456-460
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• 2021

A potentiometric sodium-ion (Na⁺) sensor was prepared using a screen-printing process with carbon and silver inks. The two-electrode configuration of the sensor resulted in potential differences in Na⁺ solutions according to Nernstian equation. The obtained Na⁺-sensor exhibited an ideal Nernstian sensitivity, fast response time, and low limit of detection. The Nernstian response was stable when the sensor was tested for repeatability and long-term durability. The Na⁺-selective membrane coated onto the carbon electrode selectively passed sodium ions against interfering ions, indicating an excellent selectivity. The portable Na⁺-sensor was finally fabricated using a printed circuit system, demonstrating the successful measurements of Na⁺ concentrations in various real samples.

• YAKHAK HOEJI
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• v.56 no.2
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• pp.74-79
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• 2012

Citrate-capped silver nanoparticles (AgNPs) are widely used in industry, consumer products and medical appliances. However, information on the toxicity, environmental fate and toxicokinetics are not enough. In this study, stability of citrate-capped AgNPs was investigated using different types of isotonic solution, which is important in the toxicokinetic study by the exposure route of intravenous injection. Size, morphology, zeta potential and ion formation were investigated in isotonic solutions for the physico-chemical characterization of AgNPs. Aggregation and precipitation of AgNPs were observed in saline or phosphate-buffered saline while they were stable without precipitation in 2% glycerol of isotonic solution. The average size of AgNPs in 2% glycerol was 6~10 nm, which was almost same as that in water-based suspension of AgNPs. Zeta potential was ranged from -30 mV to -60 mV, which was in the range of original stock AgNPs. The stability was maintained during the whole experimental period of 48 hours. Furthermore, the stability was not changed in different temperature (10~36$^{\circ}C$) and at different concentrations (10~1,000 ppm). The osmolarity of the AgNPs suspension was $299{\pm}1$ mOsm/kg which was in isotonic range. These data suggest that AgNPs in 2% glycerol solution can be used for the preparations of intravenous injection for toxicokinetic study without undesired disturbance of blood isotonicity.

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.549-558
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• 2011

Application of a generalized equivalent circuit including the electrode condition for the Hebb-Wagner polarization in the frequency domain proposed by Jamnik and Maier can provide a consistent set of material parameters, such as the geometric capacitance, partial conductivities, chemical capacitance or diffusivity, as well as electrode characteristics. Generalization of the shunt capacitors for the chemical capacitance by the constant phase elements (CPEs) was applied to a model mixed conducting system, $Ag_2S$, with electron-blocking AgI electrodes and ion-blocking Pt electrodes. While little difference resulted for the electron-blocking cell with almost ideal Warburg behavior, severely non-ideal behavior in the case of Pt electrodes not only necessitates a generalized transmission line model with shunt CPEs but also requires modelling of the leakage in the cell approximately proportional to the cell conductance, which then leads to partial conductivity values consistent with the electron-blocking case. Chemical capacitance was found to be closer to the true material property in the electron-blocking cell while excessively high chemical capacitance without expected silver activity dependence resulted in the electron-blocking cell. A chemical storage effect at internal boundaries is suggested to explain the anomalies in the respective blocking configurations.

• Corrosion Science and Technology
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• v.4 no.1
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• pp.19-22
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• 2005

Two Au-Ag-Cu-Pd dental casting alloys (Au:12% and 20%) used. The test solutions used 0.9 % NaCl solution (isotonic sodium chloride solution), 0.9 % NaCl solution containing 1 % lactic acid, and 0.9 % NaCl solution containing 1 % lactic acid and 0.1 mol $dm^{-3}$ $Na_2S$. The surface of two samples in three sample solutions was not natural discoloration during one year. The alloy containing 12 % gold was easily alloyed and the composition was uniform comparing with the alloy containing 20 % gold. The rest potentials have not a little effect after three months. The kinds of metals could not definitely from the oxidation and reduction waves of metal on the cyclic voltammograms. The dissolutions of gold and palladium were 12 % Au sample in the 0.9 % NaCl solution containing 1 % lactic acid and 0.1 mol $dm^{-3}$ $Na_{2}S$. The pH of solution had an affect on dissolution of copper, and sulfur ion had an affect on dissolution of silver. The copper dissolved amount from 20 % gold sample was about 26 times comparing with that of 12 % gold sample in the 0.9 % solution containing 1 % lactic acid. Corrosion products were silver chloride and copper chloride in NaCl solution, and silver sulfide and copper sulfide in NaCl solution containing $Na_{2}S$.