• Macromolecular Research
• /
• v.14 no.1
• /
• pp.66-72
• /
• 2006

The purpose of this study is to develop novel nanoparticles based on polyion complex formation between low molecular weight water-soluble chitosan (LMWSC) and all-trans retinoic acid (atRA). LMWSC nanoparticles encapsulating atRA based on polyion complex were prepared by mixing of atRA into LMWSC aqueous solution using ultrasonication. In FTIR spectra, the carbonyl group of atRA at 1690 $cm^{-1}$ disappeared or decreased when ion complexes were formed between LMWSC and atRA. In ${1}^H$ NMR spectra, specific peaks of atRA disappeared when atRA-encapsulated LMWSC (RAC) nanoparticles were reconstituted into $D_{2}O$ while specific peaks both of atRA and LMWSC appeared in $D_{2}O$/DMSO (1/3, v/v) mixture. XRD patterns also showed that the crystal peaks of atRA were disappeared by encapsulation into LMWSC nanoparticles. LMWSC nanoparticles encapsulating atRA have spherical shapes with particle size below 200 nm. The mechanism of encapsulation of atRA into LMWSC nanoparticles was thought to be an ion complex formation between LMWSC and atRA. LMWSC nanoparticles showed high atRA loading efficiency over 90$\%$ (w/w). AtRA was continuously released from nanoparticles over 10 days. In in vitro cell cytotoxicity test, free atRA showed higher cytotoxic effect against CT 26 colon carcinoma cell line on 1 day. However, RAC nanoparticles showed similar cytotoxicity against CT 26 cells on 2 day. These results suggest the potential for the introduction of LMWSC nanoparticles into various biomedical fields such as drug delivery.

• Korean Journal of Crystallography
• /
• v.4 no.2
• /
• pp.100-104
• /
• 1993

Reduced glutathione (GSH) plays a vital role in the metabolism of all cells. Glutathions, a tripeptide cowfosed of glutamic acid, cysteane, and gtycina is synthesized by two synthesized reutions. The first is catalyzed by Y-glutamylcysteine synthetase (GSH-I) and the second by glutathione synthetase (GSH-ll). The glutathione biosynthetic pathway of E. coziis mainly controlled by nonallosteric feedback inhibition of GHS-I by GSH. Determination of the three-dimensional structure of GSH-I by X-ray crystallography is necessary in order to understand the structure-function relationship at the molecular level. As the (irst step toward its structure determination, crystallization of 5. coli V-glutamylcystfine synthetase (GSH-I) has been achived using the hanging drop vapor diffusion method and capillaw method. Crystals of GSH-I have been grown from ammonium sulfate solution. The crystals grew at room temperature within 10 days to dimensions of 0.2 m x 0.2 m x 0.2 ml by hanging drop vapor diffusion method and diffracted to about 4 A resolution using synchrotron X-rays. Another crystal, grown by the capillary method to dimensions of 0.25 mm x 0.25 mm x 0.3 mm within 40 days, diffracted to about 4 A resolution using X-rays from a rotating anode.

• Current Photovoltaic Research
• /
• v.2 no.3
• /
• pp.88-94
• /
• 2014

The structural, optical and electrical properties of sputter-deposited CIGS films were directly influenced by the sputtering process parameters such as substrate temperature, working pressure, RF power and distance between target and substrate. CIGS thin films deposited by using a quaternary target revealed to be Se deficient due to Se low vapor pressure. This Se deficiency affected the overall stoichiometry of the films, causing the films to be Cu-rich. Current tends to pass through the Cu-Se channels which act as the shunting path increasing the film conductivity. The crystal structure of CIGS thin films depends on the substrate orientation due to the influence of surface morphology, grain size and stress of Mo substrate. The excess of Cu was removed from the CIGS films by KCN treatment, achieving a suitable Cu concentration (referred as Cu-poor) for the fabrication of solar cell. Due to high Cu concentrations on the CIGS film surface induced by Cu-Se phases after CIGS film deposition, KCN treatment proved to be necessary for the fabrication of high efficiency solar cells. Also during KCN treatment, dislocation density and lattice parameter decreased as excess Cu was removed, resulting in increase of bandgap and the decrease of conductivity of CIGS films. It was revealed that Cu-Se secondary phase could be removed by KCN wet etching of CIGS films, allowing the fabrication of high efficiency absorber layer.

• Proceedings of the SCSK Conference
• /
• 1999.10a
• /
• pp.97-110
• /
• 1999

The new stick make-up product was studied by using a gel, which is a viscous complex formed with clay minerals, vitamins A and I and fluorinated liquid polymer with a 1500 molecular weight. The gel cannot be obtained with any random combination of clay minerals and the ingredients described above. It takes the sequential manufacturing method as follows to get this kind of gel. Firstly, clay minerals and liquid polymers have ·to be pre-mixed in order to saturate the liquid polymers with the clay minerals. Then tile on-processed gel has to be finely crystallized. The clay minerals, which are the core elements for this gel, were used as a function of Binder & Buffer and liquid polymer was mixed together for the deterioration of the surface tension of each component and to from a functional film in the gel. This liquid polymer was combined with clay minerals because it is not miscible with most oils and solvents. Waxes have a function of keeping a solid status in the stick. We reduced the usage of waxes by putting clay minerals as buffer in the proportion of 0.5 : 1 with oil phase. Ceramide takes care of the skin when used regularly and maintains the skin’s moisture. Vitamins A and I contribute to preventing skin’aging by the activation of skin cells. We could get the stable viscous gel, which has about 80% oil phase using clay minerals and liquid polymer, The crystal 1 me structures of gel were surface-chemical1y-analyzed using SEM and Image Analyzer and were thermodynamically analyzed using DSC, Surface tension test and softness were done by Rheometer. In the end, these characteristics were verified by consumer panel tests in Seoul, Baegeon and Pusan in Korea and Hokkaido, Oska and Miyazaki in Japan with correlation to the climate.

• International Journal of Internet, Broadcasting and Communication
• /
• v.7 no.1
• /
• pp.75-92
• /
• 2015

This paper presents the application of the bond valence method to estimate the valence charge distribution in several perovskite systems: $La_{{\tilde{1}}x}Pb_xMnO_3$ (x=0.1-0.5), $La_{0.6}Sr_{0.{\tilde{4}}x}Ti_xMnO_3$ (x=0.0-0.25) and $La_{{\tilde{1}}x}Sr_xCoO_3$ (x=0.1-0.5); the reviewing of their crystal structures is also incorporated. The results showed the failure of the elastic bonding mechanism in all studied systems and revealed the general deficit of the valence charge in their unit cells. This valence deficit was not associated with the structural defects and was not equally localized in all coordination spheres. As the content of substitution increased, the charge deficit declined systematically from balanced level, signifying the transfer of valence charge from the ${\tilde{B}}O_6$ to ${\tilde{A}}O_{12}$ spheres. This transfer depended on the valence deviation of spheres and the average reached near 2 electron per unit cell. The possible impact of the limitted accuracy of the available structural data on the bond valence results has also been considered.

• Animal cells and systems
• /
• v.9 no.3
• /
• pp.139-144
• /
• 2005

The attractant (orange light) or repellent (white light) signal is transmitted from SRI (Sensory Rhodopsin I) via protein-protein interaction with its transducer Htrl (Halobacterial Transducer for Sensory Rhodopsin I) which in turn controls a cytoplasmic phospho-transfer pathway that modulates flagella motor switching in Halobacterium salinarum. Some mutations in both SRI and Htrl showed an unusual mutant phenotype called inverted signaling, in which the cell produces a repellent response to normally attractant light. Twelve mutations at the Glutamate 56 (E56) position in the second transmembrane helix of Htrl were introduced by site-specific random mutagenesis. Almost all E56 mutants showed orange-light inverted responses in pH and temperature-dependent manners except E56D and E56Y. Except for these two mutants, all mutants accelerated the $S_{373}$ decay compared to wild-type at $18^{\circ}C$. This supported that there is an interaction between SRI and the second transmembrane of Htrl. Also a structural model of Htrl based on the Tar crystal structure and the secondary structure prediction program proposed the E56 residue to be in the middle of the proton channel. The most important observation is that the E56 mutant provides the evidence that this residue is very sensitive for signal relay, which can be explained by the open and closed conformations of the channel (A and R conformations) in SRI, as was postulated by the unified conformational shuttling model for transport and signaling.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.2
• /
• pp.1555-1562
• /
• 2015

Metal oxide semiconductors have been applied in several areas, such as solar cells, sensor, optical elements and displays, due to the high surface area, unique electrical and optical characteristics. Zinc oxide among the metal oxide has excellent physicochemical properties. Zinc oxide is a n-type semiconductor with a wide direct transition band gap of 3.37 eV at room temperature and large exciton binding energy of 60 meV. Cation-doped zinc oxide studies were conducted to complement the electrical and optical characteristics. In this paper, Al-doped ZnO was synthesized by hydrothermal synthesis using microwaves. ZnO was synthesized by adjusting the precursor ratio and using different dopants. The optimal ZnO synthesis conditions for crystal shape and optical properties were determined. The optical properties of aluminum doped zinc oxide were then examined by SEM, XRD, PL, UV-vis absorbance spectrum, and EDS.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.06a
• /
• pp.30-31
• /
• 2006

The LSCF cathode for Solid Oxide Fuel Cell was investigated to develop high performance unit cell at intermediate temperature by modified oxalate method with different electrolyte. The LSCF precursors using oxalic acid, ethanol and $NH_4OH$ solution were prepared at $80^{\circ}C$, and pH was controlled as 2, 6, 7, 8, 9 and 10. The synthesis precursor powders were calcined at $800^{\circ}C$, $1000^{\circ}C$ and $1200^{\circ}C$ for 4hrs. Unit cells were prepared with the calcined LSCF cathode, buffer layer between cathode and each electrolyte that is the LSGM, YSZ, ScSZ and CeSZ. The synthesis LSCF powders by modified oxalate method were measured by scanning electron microscope and X-ray diffraction. The interfacial polarization resistance of cell was characterized by Solatron 1260 analyzer. The crystal of LSCF powders show single phase at pH 2, 6, 7, 8 and 9, and the average particle size was about $3{\mu}m$. The electric conductivity of synthesis LSCF cathode which was calcined at $1200^{\circ}C$ shows the highest value at pH 7. The cell consist of GDC had the lowest interfacial resistance (about 950 S/cm@650) of the cathode electrode. The polarization resistance of synthesis LSCF cathode by modified oxalate method has the value from 4.02 to 7.46ohm at $650^{\circ}C$. GDC among the electrolytes, shows the lowest polarization resistance.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.252.2-252.2
• /
• 2013

ZnO nanostructures have a lot of interest for decades due to its varied applications such as light-emitting devices, power generators, solar cells, and sensing devices etc. To get the high performance of these devices, the factors of nanostructure geometry, spacing, and alignment are important. So, Patterning of vertically- aligned ZnO nanowires are currently attractive. However, many of ZnO nanowire or nanorod fabrication methods are needs high temperature, such vapor phase transport process, metal-organic chemical vapor deposition (MOCVD), metal-organic vapor phase epitaxy, thermal evaporation, pulse laser deposition and thermal chemical vapor deposition. While hydrothermal process has great advantages-low temperature (less than $100^{\circ}C$), simple steps, short time consuming, without catalyst, and relatively ease to control than as mentioned various methods. In this work, we investigate the dependence of ZnO nanowire alignment and morphology on si substrate using of nanosphere template with various precursor concentration and components via hydrothermal process. The brief experimental scheme is as follow. First synthesized ZnO seed solution was spun coated on to cleaned Si substrate, and then annealed $350^{\circ}C$ for 1h in the furnace. Second, 200nm sized close-packed nanospheres were formed on the seed layer-coated substrate by using of gas-liquid-solid interfacial self-assembly method and drying in vaccum desicator for about a day to enhance the adhesion between seed layer and nanospheres. After that, zinc oxide nanowires were synthesized using a low temperature hydrothermal method based on alkali solution. The specimens were immersed upside down in the autoclave bath to prevent some precipitates which formed and covered on the surface. The hydrothermal conditions such as growth temperature, growth time, solution concentration, and additives are variously performed to optimize the morphologies of nanowire. To characterize the crystal structure of seed layer and nanowires, morphology, and optical properties, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and photoluminescence (PL) studies were investigated.

• Korean Journal of Materials Research
• /
• v.22 no.7
• /
• pp.362-367
• /
• 2012

Magnetite nanoparticles(NPs) have been the subject of much interest by researchers owing to their potential use as magnetic carriers in drug targeting and as a tumor treatment in cases of hyperthermia. However, magnetite nanoparticles with 10 nm in diameter easily aggregate and thus create large secondary particles. To disperse magnetite nanoparticles, this study proposes the infiltration of magnetite nanoparticles into hybrid silica aerogels. The feasible dispersion of magnetite is necessary to target tumor cells and to treat hyperthermia. Magnetite NPs have been synthesized by coprecipitation, hydrothermal and thermal decomposition methods. In particular, monodisperse magnetite NPs are known to be produced by the thermal decomposition of iron oleate. In this study, we thermally decomposed iron acetylacetonate in the presence of oleic acid, oleylamine and 1,2 hexadecanediol. We also attempted to disperse magnetite NPs within a mesoporous aerogels. Methyltriethoxysilicate(MTEOS)-based hybrid silica aerogels were synthesized by a supercritical drying method. To incorporate the magnetite nanoparticles into the hybrid aerogels, we devised two methods: adding the synthesized aerogel into a magnetite precursor solution followed by nucleation and crystal growth within the pores of the aerogels, and the infiltration of magnetite nanoparticles synthesized beforehand into aerogel matrices by immersing the aerogels in a magnetite nanoparticle colloid solution. An analysis using a vibrating sample magnetometer showed that approximately 20% of the magnetite nanoparticles were well dispersed in the aerogels. The composite samples showed that heating under an inductive magnetic field to a temperature of $45^{\circ}C$ is possible.