• Nano
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• v.13 no.12
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• pp.1850147.1-1850147.14
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• 2018

In this work, water-soluble and blue-emitting carbon nanodots (CDs) were synthesized from apple peels for the first time via one-step hydrothermal method. The synthetic route is facile, green, economical and viable. The as-prepared CDs were characterized thoroughly by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman, Fourier transform infrared (FT-IR), X-ray photoelectron (XPS), fluorescence and UV-Vis absorption spectroscopy in terms of their morphology, surface functional groups and optical properties. The results show that these CDs possessed ultrasmall size, good dispersivity, and high tolerance to pH, ionic strength and continuous UV irradiation. Significantly, the CDs had fast and reversible response towards temperature, and the accurate linear relationship between fluorescence intensity and temperature was used to design a novel nanothermometer in a broad temperature range from 5 to $65^{\circ}C$ facilely. In addition, the fluorescence intensity of CDs was observed to be quenched immediately by Cr(VI) ions based on the inner filter effect. A low-cost Cr(VI) ions sensor was proposed employing CDs as fluorescent probe, and it displayed a wide linear range from 0.5 to $200{\mu}M$ with a detection limit of $0.73{\mu}M$. The practicability of the developed Cr(VI) sensor for real water sample assay was also validated with satisfactory recoveries.

• Korean Journal of Metals and Materials
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• v.47 no.4
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• pp.256-260
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• 2009

This study examined the effects of plated temperature on the surface morphology and property of an electrodeposited copper foil. The morphology, crystal structure and electric characteristics of the electrodeposited copper foil were examined by scanning electron microscopy, X-ray diffraction, and a four-point probe, respectively. The surface roughness, crystal growth orientation and resistivity could be controlled using various temperature of electrolyte. Large particles were observed on the surface of the copper layer electroplated onto the $30^{\circ}C$. However, a uniform surface, lower resistivity and high flexibility were obtained when a $50^{\circ}C$ electrolyte was used.

• Biomaterials Research
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• v.22 no.4
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• pp.352-359
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• 2018

Background: Black phosphorus (BP) has emerged as a novel class of nanomaterials owing to its unique optical and electronic properties. BP, a two-dimensional (2D) nanomaterial, is a structure where phosphorenes are stacked together in layers by van der Waals interactions. However, although BP nanodots have many advantages, their biosafety and biological effect have not yet been elucidated as compared to the other nanomaterials. Therefore, it is particularly important to assess the cytotoxicity of BP nanodots for exploring their potentials as novel biomaterials. Methods: BP nanodots were prepared by exfoliation with a modified ultrasonication-assisted solution method. The physicochemical properties of BP nanodots were characterized by transmission electron microscopy, dynamic light scattering, Raman spectroscopy, and X-ray diffractometry. In addition, the cytotoxicity of BP nanodots against C2C12 myoblasts was evaluated. Moreover, their cell imaging potential was investigated. Results: Herein, we concentrated on evaluating the cytotoxicity of BP nanodots and investigating their cell imaging potential. It was revealed that the BP nanodots were cytocompatible at a low concentration, although the cell viability was decreased with increasing BP nanodot concentration. Furthermore, our results demonstrated that the cells took up the BP nanodots, and the BP nanodots exhibited green fluorescence. Conclusions: In conclusion, our findings suggest that the BP nanodots have suitable biocompatibility, and are promising candidates as fluorescence probes for biomedical imaging applications.

• Korean Journal of Metals and Materials
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• v.46 no.2
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• pp.88-96
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• 2008

Thermal evaporated 10 nm-$Ni_{50}Co_{50}$/(70 nm-poly)Si films were deposited to examine the energy saving properties of silicides formed by rapid thermal annealing at temperature ranging from 500 to $1,100^{\circ}C$ for 40 seconds. Thermal evaporated 10 nm-Ni/(70 nm-poly)Si films were also deposited as a reference using the same method for depositing the 10 nm-$Ni_{50}Co_{50}$/(70 nm-poly)Si films. A four-point probe was used to examine the sheet resistance. Transmission electron microscopy (TEM) and X-ray diffraction XRD were used to determine cross sectional microstructure and phase changes, respectively. UV-VIS-NIR and FT-IR (Fourier transform infrared spectroscopy) were used to examine the near-infrared (NIR) and middle-infrared (MIR) absorbance. TEM analysis confirmed that the uniform nickel-cobalt composite silicide layers approximately 21 to 55 nm in thickness had formed on the single and polycrystalline silicon substrates as well as on the 25 to 100 nm thick nickel silicide layers. In particular, nickel-cobalt composite silicides showed a low sheet resistance, even after rapid annealing at $1,100^{\circ}C$. Nickel-cobalt composite silicide and nickel silicide films on the single silicon substrates showed similar absorbance in the near-IR region, while those on the polycrystalline silicon substrates showed excellent absorbance until the 1,750 nm region. Silicides on polycrystalline substrates showed high absorbance in the middle IR region. Nickel-cobalt composite silicides on the poly-Si substrates annealed at $1,000^{\circ}C$ superior IR absorption on both NIR and MIR region. These results suggest that the newly proposed $Ni_{50}Co_{50}$ composite silicides may be suitable for applications of IR absorption coatings.

• Korean Journal of Metals and Materials
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• v.47 no.9
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• pp.586-590
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• 2009

The effects of additives on the surface morphology and physical properties of copper electrodeposited on polyimide(PI) film were investigated here. Two kinds of additives, an activator(additive A) and a leveler(additive B),were used in this study. Electrochemical experiments, in conjunction with scanning electron microscopy(SEM), X-ray diffraction(XRD) and a four-point probe, were performed to characterize the morphology and mechanical characteristics of copper electrodeposited in the presence of the additives. The surface roughness, crystal growth orientation and resistivity could be controlled using various quantities of additive B. High resistivity and lower peel strength were observed on the surface of the copper layer electroplated onto the electrolyte with no additive B. However, a uniform surface, lower resistivity and high flexibility were obtained with a combination of 20 ppm of additive A and 100 ppm of additive B.

• Korean Journal of Metals and Materials
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• v.48 no.2
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• pp.133-140
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• 2010

10 nm thick Ni layers were deposited on 200 nm $SiO_2/Si$ substrates using an e-beam evaporator. Then, 60 nm or 20 nm thick ${\alpha}$-Si:H layers were grown at low temperature (<$200^{\circ}C$) by a Catalytic-CVD. NiSi layers were already formed instantaneously during Cat-CVD process regardless of the thickness of the $\alpha$-Si. The resulting changes in sheet resistance, microstructure, phase, chemical composition, and surface roughness with the additional rapid thermal annealing up to $500^{\circ}C$ were examined using a four point probe, HRXRD, FE-SEM, TEM, AES, and SPM, respectively. The sheet resistance of the NiSi layer was 12${\Omega}$/□ regardless of the thickness of the ${\alpha}$-Si and kept stable even after the additional annealing process. The thickness of the NiSi layer was 30 nm with excellent uniformity and the surface roughness was maintained under 2 nm after the annealing. Accordingly, our result implies that the low temperature Cat-CVD process with proposed films stack sequence may have more advantages than the conventional CVD process for nano scale NiSi applications.

• Korean Journal of Metals and Materials
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• v.47 no.12
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• pp.811-818
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• 2009

In order to meet increasingly complex and rigorous technical specifications, extensive effort has been devoted to fabricate clad materials with multi-layered metal plates. In this study, novel stainless steel/aluminum/copper (STS/Al/Cu) three-ply clad materials were fabricated by a hot rolling process for cookware applications. The effect of the testing temperature on the mechanical properties of the clad materials and on each component metal was investigated during the tensile tests. The interface properties of the clad materials were also examined by optical microscopy (OM) and an electron probe micro-analyzer (EPMA). The best mechanical and interfacial properties for a warm working process were found in a sample annealed at a temperature of $300^{\circ}C$. For the sample annealed at $400^{\circ}C$, the results of the tensile test indicated that interface delamination occurred only in the region of the Al/Cu interfaces. This was due to the formation of the thick and brittle intermetallic compound of $Al_2Cu$ in the Al/Cu interface. In contrast, no interface delamination was observed in the STS/Al interface, most likely due to its strong bond strength.

• Journal of the Korean Applied Science and Technology
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• v.38 no.6
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• pp.1553-1560
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• 2021

We have confirmed that optimized transmittance and surface resistance by electrospinning time, also the fabricated transparent electrode composed of silver nanofiber with excellent electrical, optical and mechanical performances is showed applicability to next generation flexible displays such as solar cells, displays, and touch screens. → We have confirmed the optimized transmittance and surface resistance by electrospinning time Also the fabricated transparent electrode composed of silver nanofiber with excellent electrical, optical and mechanical performances showed applicability to next generation flexible displays such as solar cells, displays, and touch screens.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.163-163
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• 2000

In this research, we used the ion irradiation technique which has an advantae in improving intentionally the properties of surface and interface in a non-equilibrium, instead of the conventional annealing method which has been known to improve the material properties in the equilibrium stat. Cu/Co multilayered films were prepared on SiN4/SiO2/Si substrates by the electron-beam evaporation for the Co layers and the thermal evaporation for the Cu layers in a high vacuum. The ion irradiation with a 80keV Ar+ was carried out at various ion doses in a high vacuum. Hysteresis loops of the films were investigated by magneto-optical polar Kerr spectroscopy at various experimental conditions. The change of atomic structure of the films before and after the ion irradiation was studied by glancing angle x-ray diffraction, and the intermixing between Co and Cu sublayers was confirmed by Rutherford backscattering spectroscopy. The surface roughness and magneto-resistance were measured by atomic force microscopy and with a four-point probe system, respectively. During the magneto-resistance measurement, we changed temperature and the direction of magnetization. From the results of experiments, we found that the change at the interfaces of the Cu/Co multilayered film induced by ion irradiation cause the change of magnetic properties. According to the change in hysteresis loop, the surface inplane component of magnetic easy axis was isotropic before the ion irradiation, but became anisotropic upon irradiation. It was confirmed that this change influences the axial behavior of magneto-resistance. Especially, the magneto-resistance varied in accordance with an external magnetic field and the direction of current, which means that magneto-resistance also shows the uniaxial behavior.

• Economic and Environmental Geology
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• v.19 no.spc
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• pp.139-149
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• 1986

Compositional variation of sphalerites from various hydrothermal metallic ore deposits in Korea were investigated in mine and local, and regional scale. The sphalerites were partially analyzed for iron, manganese, and cadmium by using an electron probe microanalyzer(EPMA). The contents of iron and cadmium in sphalerites collected from the Weolam deposit of the No.1 Yeonhwa mine are not variable with increase of depth, but manganese content is highly variable. Sphalerites from lead-zinc deposits which are geologically associated with hypabyssal and effusive activity are characterized by high manganese (more than 1.0 MnS mole %) and low cadmium contents (less than 0.5 CdS mole %). Relatively manganese rich sphalerites are found in the deposits where sphalerites are enriched in iron content. Variation of cadmium content is very limited compared with that of manganese content. Sphalerites from most tungsten and some gold-silver deposits are remarkably high in cadmium content, but most of base metal and iron deposits are low in cadmium content. Cadmium content in sphalerites which occur in the metallic ore deposits genetically associated with plutonic activity shows a tendency to high variation. Available amounts of cadmium in sphalerites could be originated from the initial enrichment during the magmatic and postmagmatic processes.