• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.375-375
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• 2009

For many large-scale applications of high-temperature superconducting materials, large critical current density($J_c$) in high applied magnetic fields are required. A number of methods have been reported to introduce artificial pinning centers(APCs) in $YBa_2Cu_3O_{7-\delta}$(YBCO) films for enhancement of their $J_c$. We report measurements of critical current in $YBa_2Cu_3O_{7-\delta}$ films deposited by PLD on $SrTiO_3$ substrates decorated with Au nanoparticles. Au nanoparticles were synthesized on STO substrates with self assembled monolayer. Microstructural analysis of the obtained YBCO films was performed by using cross-section transmission electron microscopy(TEM). Phase and textural analysis was done using X-ray diffraction. The surface morphology and surface roughness(Ra) of the layers was measured by atomic force microscopy(AFM).

• Journal of Hydrogen and New Energy
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• v.30 no.6
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• pp.549-555
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• 2019

Electrocatalysis of oxygen reduction reaction (ORR) using Pt nanoparticles or bimetal on carabon was studied. Currently, the best catalyst is platinum, which is a limited resource and expensive to commercialize. In this paper, we investigated the cheaper and more active electrocatalysts by making Pt nanoparticles and adding 3D transition metal such as copper. Electrocatalysts were obtained by chemical reduction based on ethylene glycol solutions. Elemental analysis and particle size were confirmed by XRD and TEM. The electrochemical surface area (ECSA) and activity of the catalyst were determined by electrochemical techniques such as cyclic voltammetry and linear sweep voltammetry method. The commercialized Pt support on carbon (Pt/C, JM), synthesis Pt/C and synthesis Pt3Cu1 alloy nanoparticles supported on carbon were compared. We confirmed that the synthesized Pt3-Cu1/C has high electrochemical performance than commercial Pt/C. It is expected to develop an electrocatalyst with high activity at low price by increasing the oxygen reduction reaction rate of the fuel cell.

• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2645-2648
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• 2014

In this paper ultrafine copper nanoparticles (CuNPs) were prepared from copper salt via chemical reduction method with sodium citrate dispersant and polyvinylalcol (PVA) capping polymer. The colloidal CuNPs were characterized by using UV-Visible spectroscopy, Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD) techniques. Our obtained results indicated that the CuNPs were produced ranging from 2 to 4 nm in diameter. The colloidal solution at 7 ppm of CuNPs exhibited a powerful antifungal activity against Corticium salmonicolor (C. Salmonicolor). Fungal killing assays showed colloid solutions containing 10 ppm of CuNPs killed entirely the cultured fungus. A highly killing activity against the fungus was also performed when the CuNPs were sprayed on pink disease-infected rubber trees. These positive results may offer a great potential to produce CuNPs-based eco-fungicide for pink disease.

• Journal of the Korean Ceramic Society
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• v.50 no.3
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• pp.231-237
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• 2013

Thermodynamic modeling of the $Ni_{0.5}Zn_{0.4}Cu_{0.1}Fe_2O_4$ complex ferrite system has been adopted as a rational approach to establish routes to better synthesis conditions for pure phase $Ni_{0.5}Zn_{0.4}Cu_{0.1}Fe_2O_4$ complex ferrite. Quantitative analysis of the different reaction equilibria involved in the precipitation of $Ni_{0.5}Zn_{0.4}Cu_{0.1}Fe_2O_4$ from aqueous solutions has been used to determine the optimum synthesis conditions. The spinel ferrites, such as magnetite and substitutes for magnetite, with the general formula $MFe_2O_4$, where M= $Fe^{2+}$, $Co^{2+}$, and $Ni^{2+}$ are prepared by coprecipitation of $Fe^{3+}$ and $M^{2+}$ ions with a stoichiometry of $M^{2+}/Fe^{3+}$= 0.5. The average particle size of the as synthesized $Ni_{0.5}Zn_{0.4}Cu_{0.1}Fe_2O_4$, measured by transmission electron microscopy (TEM), is 14.2 nm, with a standard deviation of 3.5 nm the size when calculated using X-ray diffraction (XRD) is 16 nm. When $Ni_{0.5}Zn_{0.4}Cu_{0.1}Fe_2O_4$ ferrite is annealed at elevated temperature, larger grains are formed by the necking and mass transport between the $Ni_{0.5}Zn_{0.4}Cu_{0.1}Fe_2O_4$ ferrite nanoparticles. Thus, the grain sizes of the $Ni_{0.5}Zn_{0.4}Cu_{0.1}Fe_2O_4$ gradually increase as heat treatment temperature increases. Based on the results of Thermogravimetric Analysis (TGA) and Differential Scanning Calorimeter (DSC) analysis, it is found that the hydroxyl groups on the surface of the as synthesized ferrite nanoparticles finally decompose to $Ni_{0.5}Zn_{0.4}Cu_{0.1}Fe_2O_4$ crystal with heat treatment. The results of XRD and TEM confirmed the nanoscale dimensions and spinel structure of the samples.

• Toxicological Research
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• v.25 no.4
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• pp.195-201
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• 2009

Recent publications showed that metal nanoparticles which are made from $TiO_2,\;CeO_2,\;Al_2O_3,\;CuCl_2,\;AgNO_3$ and $ZnO_2$ induced oxidative stress and pro-inflammatory effects in cultured cells and the responses seemed to be common toxic pathway of metal nanoparticles to the ultimate toxicity in animals as well as cellular level. In this study, we compared the gene expression induced by two different types of metal oxide nanoparticles, titanium dioxide nanoparticles (TNP) and cerium dioxide nanoparticles (CNP) using microarray analysis. About 50 genes including interleukin 6, interleukin 1, platelet-derived growth factor $\beta$, and leukemia inhibitory factor were induced in cultured BEAS2B cells treated with TNP 40 ppm. When we compared the induction levels of genes in TNP-treated cells to those in CNP-treated cells, the induction levels were very correlated in various gene categories (r=0.645). This may suggest a possible common toxic mechanism of metal oxide nanoparticles.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.625-628
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• 2012

We investigated the interaction between polyynes (linear carbon chains) and various metal nanoparticles (Ag, Au, and Cu) to provide insight into the optical properties of metal-polyynes systems prepared by different experimental techniques. Polyynes were produced by laser ablation in deionized water, metal nanoparticles solutions, and copper chloride solution. Metal nanoparticles complexes with polyynes were analyzed by Raman, surface-enhanced Raman scattering, and UV-vis spectroscopy.

• Bulletin of the Korean Chemical Society
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• v.29 no.8
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• pp.1561-1564
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• 2008

Although the use of Cu(II) salts as catalysts without reductants is limited in the cycloaddition of acetylenes with azides, the catalytic system employing average 10 nm CuO(II) nanoparticles in the absence of reductants shows good catalytic activity to form 1,4-disubstituted 1,2,3-triazoles even in wet THF as well as water. It is also noticeable that CuO(II) nanoparticle catalysts can be recycled with consistent activity. A range of alkynes and azides were subject to the optimized CuO(II) nanoparticle-catalyzed cycloaddition reaction conditions to afford the desired products in good yields.

• Bulletin of the Korean Chemical Society
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• v.34 no.7
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• pp.2176-2182
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• 2013

A novel sol-gel method was implied to prepare CuO-doped ZnO nanoparticles. XRD and SEM techniques were used to characterize the CuO-doped ZnO sample. The photocatalytic degradation of Lidocaine HCl was investigated by two methods. The degradation was studied under different conditions such as the amount of photocatalyst, pH of the system, initial concentration, presence of electron acceptor, and presence of anions. The results showed that they strongly affected the photocatalytic degradation of Lidocaine HCl. The photodegradation efficiency of drug increased with the increase of the irradiation time. After 6 h irradiation with 400-W mercury lamp, about 93% removal of Lidocaine HCl was achieved. The degree of photodegradation obtained by Taguchi method compatible with the trial-and-error method showed reliable results.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.3
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• pp.25-30
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• 2015

SAC-coated Cu specimens were fabricated by novel pad finish process using a phenomenon that metal nanoparticles less than 20 nm in diameter melted at a temperature lower than the melting point of bulk metal, and their wettabilities were evaluated. The thickness of SAC305 layer coated at low temperature of $160^{\circ}C$ using SAC305 ink was extremely thin as the level of several nanometers. It was analyzed by Auger electron spectroscopy that $Cu_6Sn_5$ intermetallic layer with a thickness of 10~100 nm and $Cu_3Sn$ intermetallic layer with a thickness of 50~150 nm were sequentially formed under the SAC305 coating layer. The thickness of formed intermetallic layers was thicker in electroplated Cu than rolled Cu, which attributed to improved surface roughness in the electroplated Cu. The improved surface roughness induces the contact, melting, and reaction of a larger number of SAC305 nanoparticles per the unit area of Cu specimen. In the wetting angle test using SAC305 solder balls, the Cu coated with SAC305 through the low temperature process presented evidently low wetting angles than those in non-coated Cu, indicating that only a few nanometer-thick SAC305 coating layer on Cu could also cause the enhancement of wettability.

• Journal of Powder Materials
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• v.16 no.4
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• pp.243-248
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• 2009

Carbon-coated Cu nanopowders with core/shell structure have been successfully fabricated by pulsed wire evaporation (PWE) method, in which a mixed gas of Ar/$CH_4$ (10 vol.%) was used as an ambient gas. The characterization of the samples was carried out using x-ray diffraction (XRD), scanning electron microscope (SEM), and high resolution transmission electron microscope (HRTEM). It was found that the nanoparticles show a spherical morphology with the size ranging of 10-40 nm and are covered with graphite layers of 2-4 nm. When oxygen-passivated Cu nanopowders were annealed under flowing argon gas (600 and 800$^{\circ}C$), the crystallinity of $Cu_2O$ phase and the particle size gradually increased. On the other hand, carbon-coated Cu nanopowders remained similar to as-prepared case with no additional oxide or carbide phases even after the annealing, indicating that the metal nanoparticles are well protected by the carbon-coating layers.