• Bulletin of the Korean Chemical Society
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• v.34 no.9
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• pp.2577-2582
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• 2013

A novel stick-shaped portable sensing device featuring a microhole array interface between the polyvinylchloride-2-nitrophenyloctylether (PVC-NPOE) gel and water phase was developed for in-situ sensing of perchlorate ions in real water samples. Perchlorate sensitive sensing responses were obtained based on measuring the current changes with respect to the assisted transfer reaction of perchlorate ions by a perchlorate selective ligand namely, bis(dibenzoylmethanato)Ni(II) (Ni(DBM)2) across the polarized microhole array interface. Cyclic voltammetry was used to characterize the assisted transfer reaction of perchlorate ions by the $Ni(DBM)_2$ ligand when using the portable sensing device. The current response for the transfer of perchlorate anions by $Ni(DBM)_2$ across the micro-water/gel interface linearly increased as a function of the perchlorate ion concentration. The technique of differential pulse stripping voltammetry was also utilized to improve the sensitivity of the perchlorate anion detection down to 10 ppb. This was acquired by preconcentrating perchlorate anions in the gel layer by means of holding the ion transfer potential at 0 mV (vs. Ag/AgCl) for 30 s followed by stripping the complexed perchlorate ion with the ligand. The effect of various potential interfering anions on the perchlorate sensor was also investigated and showed an excellent selectivity over $Br^-$, $NO_2{^-}$, $NO_3{^-}$, $CO{_3}^{2^-}$, $CH_3COO^-$ and $SO{_4}^{2^-}$ ions. As a final demonstration, some regional water samples from the Sincheon river in Daegu city were analyzed and the data was verified with that of ion chromatography (IC) analysis from one of the Korean-certified water quality evaluation centers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.05a
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• pp.100-105
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• 1995

Bulk glasses in the system $Na_2O$-CaO-$Al_2O_3$-$B_2O_3$-$SiO_2$ containing 20 to 30 mol% sod-ium hav been subjected to a sodium silver ion-exchange reaction for 0, 24, 36, 48 jr were analysed by electrical characterization Ion-exchanged glasses exhibit resistivity and activation energy values lower than those of the untreated ones. The electrical conductivity increase with sodium content and ion-exchanged time. In this experiment the electrical conductivity exhibit a maximum value of 1.78${\times}$10$^{-4}$S/cm at $200^{\circ}C$ which contains 30 mol% sodium and subjects ion-exchange reaction for 48hr.

• Journal of the Korean Chemical Society
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• v.42 no.4
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• pp.416-421
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• 1998

In the reversed-phase ion-pair high performance liquid chromatographic (RPIP-HPLC) elution behavior of noble metal-thiacrown ether complexes, the effects of the concentration of ion-pairing reagent and kind of ligands were studied. It was found that the less the number of atoms in the ring of the thiacrown ether molecule was, the larger the selectivity was, and the elution mechanism of the complexes was explained due to the formation of ion-pair when the concentration of sodium dodecyl sulfate (SDS) in mobile phase was lower than 10 mM and due to the formation of micelle when the SDS concentration was higher than 10 mM. As a conclusion, separations of the noble metal-thiacrown ether complexes in an optimum separation condition were accomplished successfully and the method was proved to be an useful one for the separation and determination of Ag (Ⅰ) ion in a black-white photographic fixing solution.

• Korean Journal of Optics and Photonics
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• v.11 no.5
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• pp.335-339
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• 2000

A $1.31/1.55\mu\textrm{m}$ coarse WDM opncal dIrectional coupler that conslsls of two idenlical straight channel waveguides in BK7 glass has been fabricated. The separatIOn between two channel waveguides is $8\mu\textrm{m}$ and the wavegu.ide width is $4\mu\textrm{m}$ . Especlally, we assumed that the index profile is Gaussian function and complementary error function in the width direction and depth direction, respectrvely. This directional coupler operating at $1.31/1.55\mu\textrm{m}$ with crosstalk of 18dB is demonstrated and has the 16 mm long length with 12.6 mm coupling region.region.

• Korean Membrane Journal
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• v.8 no.1
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• pp.43-49
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• 2006

Complex membranes consisting of silver salt ($AgBF_4,\;AgCF_3SO_3,\;AgSbF_6,\;AgNO_3$) and poly(vinyl alcohol) (PVA) or crosslinked PVA (CPVA) were prepared and tested for the separation of propylene/propane mixtures. For the tested membranes, the complex membranes containing $AgBF_4$ exhibited the highest separation properties, i.e., approximately 20 GPU ($1 GPU=10^{-6}cm^3 (STP)/(cm^2 sec cmHg)$) and 100 of selectivity at 0.2 of silver mole fraction. The CPVA membranes containing silver salt always showed higher selectivity than PVA membranes, presenting silver ions coordinated to -CHO are more effective than those to -OH groups. The threshold silver concentration of CPVA membranes was lower than that of PVA membranes, which might be due to stronger interaction of silver ions with -CHO than that with -OH. The composition at which the selectivity is the highest did not significantly depend on the crosslinking, but did on the kind of silver salt.

• Progress in Superconductivity
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• v.3 no.1
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• pp.91-94
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• 2001

By varying fabricating process, precursor powders with different initial conditions were prepared. Subsequently, Bi-2223/Ag tapes were made through these powders. The effects of precursor powders on the phase evolution and Jr properties of Bi-2223/Ag tapes were studied along with several thermomechanical cycles. Our results showed that the initial conditions of precursor powders could strongly influence the phase formation rate and $J_{c}$ value in final tapes. The factors of precursor powders that influence the phase formation and $J_{c}$ of Bi-2223/Ag tapes must be studied and optimized in combination.ion.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.34.2-34.2
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• 2009

The silver sulphide (Ag2S) thin films have been chemically deposited from an alkaline medium (pH 8 to 10) by using a silver nitrate and thiourea as a Ag and S ion precursor sources. Ethylene Damine tetraacetic acid (EDTA) was used as a complexing agent. The effect of annealing atmosphere such as Ar, N2+H2S and O2 on the structural, morphological and optical properties of Ag2S thin films has been studied. The annealed films were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical absorption techniques for the structural, morphological, and optical properties, respectively. XRD studies reveal that the as-deposited thin films are polycrystalline with monoclinic crystal structure, is converted in to silver oxide after air annealing. The surface morphology study shows that grains are uniformly distributed over the entire surface of the substrate. Optical absorption study shows the as-deposited Ag2S thin films with band gap energy of 0.92eV and after air annealing it is found to be 2.25 eV corresponding to silver oxide thin films.

• Carbon letters
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• v.18
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• pp.30-36
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• 2016

Well-dispersed Ag₃VO₄ nanoparticles @polyacrylonitrile (PAN) nanofibers were synthesized by an easily controlled, template-free method as a photo-catalyst for the degradation of methylene blue. Their structural, optical, and photocatalytic properties have been studied by X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscopy equipped with rapid energy dispersive analysis of X-ray, photoluminescence, and ultraviolet-visible spectroscopy. The characterization procedures revealed that the obtained material is PAN nanofibers decorated by Ag₃VO₄ nanoparticles. Photocatalytic degradation of methylene blue investigated in an aqueous solution under irradiation showed 99% degradation of the dye within 75 min. Finally, the antibacterial performance of Ag₃VO₄ nanoparticles @PAN composite nanofibers was experimentally verified by the destruction of Escherichia coli. These results suggest that the developed inexpensive and functional nanomaterials can serve as a non-precious catalyst for environmental applications.

• Bulletin of the Korean Chemical Society
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• v.31 no.3
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• pp.615-619
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• 2010

A new coumarin-thiazolobenzo-crown ether based fluorogenic chemosensor BTC (1) was reported. The ion-selective binding properties of 1 with different alkali, alkaline earth metals and transitional metals were investigated in an ethanol-DMSO system. BTC (1) showed the highest binding constant toward $Hg^{2+}$ over $Ag^+$, $Pb^{2+}$ and $Cu^{2+}$.

• Membrane Journal
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• v.21 no.1
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• pp.39-45
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• 2011

An amphiphilic graft copolymer consisting of a poly(vinyl chloride) (PVC) backbone and poly(styrene sulfonic acid) (PSSA) side chains (PVC-g-PSSA) was synthesized via atom transfer radical polymerization (ATRP). This polymer electrolyte membrane was ion-exchanged to Ag ions by immersing in 10 wt% $AgNO_3$ aqueous solution and templated the growth of Ag nanoparticles by a reducing agent. The formation of Ag nanoparticles was confirmed using UV-visible spectroscopy and X-ray diffraction (XRD). Transmission electron microscopy (TEM) revealed that utilization of $NaBH_4$ was the most effective in the formation of Ag nanoparticles with 10~15 nm in size. The formation of Ag nanoparticles was also strongly affected by the concentration of reducing agent and reduction time.