• Proceedings of the SCSK Conference
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• 2003.09a
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• pp.501-519
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• 2003

Silk Sericin(SS) is a natural protein extracted from cocoon of bombix mori and shows moisturizing effect to the skin due to a number of hydroxyl groups in the structure. But its application to cosmetics is limited due to its poor solubility in water. In order to solve this drawback and expand its application to cosmetics, polyethyleneglycol(PEG) was conjugated with sericin by reacting activated polyethyleneglycol(ActPEG). Reaction site of sericin is tyrosine residue, which was determined by using $^1$H-NMR. Random coil structure of sericin was transformed to beta-sheet structure by conjugating polyethyleneglycol. It was confirmed that melting point of sericin-PEG conjugate was lowered compared to that of each sericin and PEG due to the interaction between sericin and PEG in crystalline structure. Self-assembled sericin-PEG nanoparticle was obtained by dialyzing with alcohol solution of sericin-PEG conjugate against water. The particle is spherical and has 200-400nm of size. The moisturizing ability of sericin-PEG nanoparticle was much higher than that of sericin itself. Incorporation of vitamin A into sericin-PEG nanoparticle was carried out by diafiltration method. The content of incorporated Vitamin A in sericin-PEG nanoparticle was 8.9 wt％. Releasing behaviour of vitamin A incorporated into nanoparticle was tested in phosphate buffer, pH 7.4 at 37$^{\circ}C$. and half-life of Vitamin A release was 43hrs. Sericin-PEG nanoparticle exhibited higher moisturing effect than sericin itself and distilled water, respectively. No toxicity and irritation were observed in animal tests. It can be expected that the self-assembled sericin-PEG nanoparticle can be developed for cosmetics.

• Korean Journal of Materials Research
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• v.23 no.5
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• pp.260-265
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• 2013

Silicon nanoparticle is a promising material for electronic devices, photovoltaics, and biological applications. Here, we synthesize silicon nanoparticles via $CO_2$ laser pyrolysis and study the hydrogen flow effects on the characteristics of silicon nanoparticles using high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and UV-Vis-NIR spectrophotometry. In $CO_2$ laser pyrolysis, used to synthesize the silicon nanoparticles, the wavelength of the $CO_2$ laser matches the absorption cross section of silane. Silane absorbs the $CO_2$ laser energy at a wavelength of $10.6{\mu}m$. Therefore, the laser excites silane, dissociating it to Si radical. Finally, nucleation and growth of the Si radicals generates various silicon nanoparticle. In addition, researchers can introduce hydrogen gas into silane to control the characteristics of silicon nanoparticles. Changing the hydrogen flow rate affects the nanoparticle size and crystallinity of silicon nanoparticles. Specifically, a high hydrogen flow rate produces small silicon nanoparticles and induces low crystallinity. We attribute these characteristics to the low density of the Si precursor, high hydrogen passivation probability on the surface of the silicon nanoparticles, and low reaction temperature during the synthesis.

• Korean Journal of Materials Research
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• v.25 no.12
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• pp.719-726
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• 2015

For a decade, solution-processed functional materials and various printing technologies have attracted increasingly the significant interest in realizing low-cost flexible electronics. In this study, Cu nanoparticles are synthesized via the chemical reduction of Cu ions under inert atmosphere. To prevent interparticle agglomeration and surface oxidation, oleic acid is incorporated as a surface capping molecule and hydrazine is used as a reducing agent. To endow water-compatibility, the surface of synthesized Cu nanoparticles is modified by a mixture of carboxyl-terminated anionic polyelectrolyte and polyoxylethylene oleylamine ether. For reducing the surface tension and the evaporation rate of aqueous Cu nanoparticle inks, the solvent composition of Cu nanoparticle ink is designed as DI water:2-methoxy ethanol:glycerol:ethylene glycol = 50:20:5:25 wt%. The effects of poly(styrene-co-maleic acid) as an adhesion promoter(AP) on rheology of aqueous Cu nanoparticle inks and adhesion of Cu pattern printed on polyimid films are investigated. The 40 wt% aqueous Cu nanoparticle inks with 0.5 wt% of Poly(styrene-co-maleic acid) show the "Newtonian flow" and has a low viscosity under $10mPa{\cdots}S$, which is applicable to inkjet printing. The Cu patterns with a linewidth of $50{\sim}60{\mu}m$ are successfully fabricated. With the addition of Poly(styrene-co-maleic acid), the adhesion of printed Cu patterns on polyimid films is superior to those of patterns prepared from Poly(styrene-co-maleic acid)-free inks. The resistivities of Cu films are measured to be $10{\sim}15{\mu}{\Omega}{\cdot}cm$ at annealing temperature of $300^{\circ}C$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.6439-6444
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• 2015

With increasing concern about global warming, CCS (Carbon dioxide capture and storage) has attracted much attention as a promising technology for reducing $CO_2$ emission. It is necessary to develop the cost-effective absorbents materials in order to rapid commercialize CCS technologies. In this work, he study for the promotion of absorption rate in $CO_2$ capture system using metal nanoparticle were investigated. Three kinds of metal nanoparticle, cobalt, zinc, and nickel, were prepared by wet and dry method and effect of preparation method on the absorption rate of $CO_2$ were compared. Among the tested using pH method, nickel nanoparticle prepared by wet method showed the most significant improvement of $CO_2$ absorption rate. In case that metal nanoparticle is applied to CCS process, it is expected to be more efficient in $CO_2$ capture process due to reduce the size of absorption tower.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1334-1338
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• 2006

In this work, indium tin oxide (ITO) thin film was fabricated by indium-tin-organic sol including ITO nanoparticle. ITO nanoparticle showed ultrafine size about 5 nm and (222) preferred crystal structure. Also, ITO sol-gel thin film showed good optical transmittance over 83% and electrical resistance less than $7\;{\times}\;10^3\;{\Omega}$.

• Journal of Magnetics
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• v.8 no.1
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• pp.7-12
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• 2003

The method for evaluation of the particle size distribution of fine particles from hysteresis loop measurements is Presented. The method is illustrated on the SiO$_2$-based Co nanoparticle systems. The influence of technological conditions of sample preparation onto particle size distribution is investigated.

• Journal of Powder Materials
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• v.18 no.6
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• pp.538-545
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• 2011

This study shows that catalytic activity of bimetallic RhPt nanoparticle arrays under CO oxidation can be tuned by varying the size and composition of nanoparticles. The tuning of size of RhPt nanoparticles was achieved by changing concentration of rhodium and platinum precursors in one-step polyol synthesis. Two-dimensional RhPt bimetallic nanoparticle arrays in different size and composition were prepared through Langmuir-Blodgett thin film technique. CO oxidation was carried out on these two-dimensional nanoparticle arrays, revealing higher activity on the smaller nanoparticles compared to the bigger nanoparticles. X-ray photoelectron spectroscopy (XPS) results indicate the preferential surface segregation of Rh compared to Pt on the smaller nanoparticles, which is consistent with the thermodynamic analysis. Because the catalytic activity is associated with differences in the rates of $O_2$ dissociative adsorption between Pt and Rh, this paper suppose that the surface segregation of Rh on the smaller bimetallic nanoparticles is responsible for the higher catalytic activity in CO oxidation. This result suggests a control mechanism of catalytic activity via synthetic approaches of colloid nanoparticles, with possible application in rational design of nanocatalysts.

• Journal of the Korean Magnetics Society
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• v.16 no.2
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• pp.144-148
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• 2006

$CoGa_{0.1}Fe_{1.9}O_4$ nanoparticles have been prepared by a sol-gel method. The structural and magnetic properties have been investigated by XRD, SEM, VSM and $M\ddot{o}ssbauer$ spectroscopy. $CoGa_{0.1}Fe_{1.9}O_4$ powder that was annealed at $250^{\circ}C$ has spinel structure and behaved superparamagnetically. The estimated size of superparammagnetic $CoGa_{0.1}Fe_{1.9}O_4$ nanoparticle is around 10 nm. The hyperfine fields at 4.2 K f3r the A and B patterns were found to be 518 and 486 kOe, respectively. The blocking temperature $(T_B)$ of superparammagnetic $CoGa_{0.1}Fe_{1.9}O_4$ nanoparticle is about 250 K. The magnetic anisotropy constant of $CoGa_{0.1}Fe_{1.9}O_4$ nanoparticle was calculated to be $3.0X10^5\;ergs/cm^3$. $CoGa_{0.1}Fe_{1.9}O_4$ nanoparticle was annealed at $250^{\circ}C$ will be used to candidate for biomedicine applications as magnetic carriers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.19-19
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• 2008

We investigated the programmable memory characteristics of nanoparticle-based memory devices based on the elementary metal nanoparticles (Co and Au) and their binary mixture synthesized by a micellar route to ordered arrays of metal nanoparticles as charge trapping layers. According to the metal nanoparticle species quite different programming/erasing efficiencies were observed, resulting in the tunable memory characteristics at the same programming/erasing bias conditions. This finding will be a good implication for further device scaling and novel device applications since most processes are based on the conventional semiconductor processes.

• Proceedings of the Korean Magnestics Society Conference
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• 2004.06a
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• pp.28-29
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• 2004