• Journal of the Korean Society of Radiology
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• v.3 no.3
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• pp.37-40
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• 2009

In this study, we made a high efficiency x-ray detecting sensor using the lead oxide(PbO) that are used in direct method of x-ray detector. PbO with nano size particles is produced by sol-gel method for high efficiency. The produced PbO with nano size is deposited on ITO(Induim Tin Oxide) glass in several temperature using the PIB(particle-in-binder) method. The thickness of the deposited PbO is about $200{\mu}m$. Through the measurement of dark current, sensitivity and SNR(Signal To Noise Ratio), an electrical properties of the produced PbO film are analyzed. Therefore, we show that an electrical properties are changed according to a temperature and that the PbO film that was treated at $500^{\circ}C$ in O2 atmosphere is the most high efficiency x-ray detecting sensor.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.3
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• pp.287-292
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• 2007

In general, the response of bulk material is independent of its size when it comes to considering classical elasticity theory. Because the surface to bulk ratio of the large solids is very small, the influence of surface can be negligible. But the surface effect plays important role as the surface to bulk ratio becomes larger, that is, the contribution of the surface effect must be considered in nano-size elements such as thin film or beam structure. Molecular dynamics computation has been a conventional way to analyze these ultra-thin structures but this method is limited to simulate on the order of $10^6{\sim}10^9$ atoms for a few nanoseconds, and besides, very time consuming. Analysis of structures in submicro to micro range(thin-film, wire etc.) is difficult with classical molecular dynamics due to the restriction of computing resources and time. Therefore, in this paper, the continuum-based method is considered to simulate the overall physical and mechanical properties of the structures in nano-scale, especially, for the thin-film.

• Membrane Journal
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• v.24 no.2
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• pp.113-122
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• 2014

Porous poly(L-lactic acid)(PLLA) scaffold membranes were prepared via. phase separation process. Chloroform, dichloromethane and 1,4-dioxane were used as solvent and, ethyl alcohol was used as non-solvent. Morphologies, mechanical properties and mass transfer characteristics of the scaffold membranes were investigated through SEM, stress-strain test and glucose diffusion test. The scaffold membranes obtained from the casting solutions with chloroform and with dichloromethane showed similar morphologies. They showed sponge-like porous structure with the pore size in the range of $3-10{\mu}m$ and, their porosities were in 50-80% range. Using 1,4-dioxane as solvent, nano-fibrous scaffold membranes with porosities over 80% were fabricated. When the polymer content in the solution with 1,4-dioxane was lowered to 4%, highly porous, macroporous and nano-fibrous scaffold membranes were obtained. The size of the macropore was tens of the microns and the porosity was around 90%. These results indicate that the solvent has significant effect on the scaffold membrane structure and, that scaffold membranes with various structures can be fabricated through phase separation method by choosing solvent and by controlling polymer concentration in the casting solution.

• Polymer(Korea)
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• v.29 no.3
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• pp.266-270
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• 2005

Iron oxide nanoparticles were prepared by the thermal decomposition of iron pentacarbonyl (Fe(CO)$_5$) Poly(vinylpyrrolidone) (PVP) was used as surface-modifying agent to control the size of the iron oxide nanoparticles. The crystalline structure of PVP coated iron oxide nanoparticles was determined by XRD. The size of PVP coated iron oxide nanoparticles was determined by TEM and ELS. The particle sizes of PVP coated iron oxide nanoparticles were controlled by adjusting the molar ratio of PVP/Fe (CO)$_5$, solvent and molecular weight of PVP Particle sizes increased with increasing PVP content. Spherical $50\~100$ nm sized iron oxide nanoclusters were produced when dimethylformamide was used as a solvent. And well-defined 10 nm iron oxide nanoparticles were produced in Carbitol. The prepared PVP coated iron oxide nanoparticles exhibited a well-dispersed property in water. The results obtained in this study confirmed the feasibility of the PVP-coated iron oxide nanoparticles as a biomaterial for MRI contrast agent.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.6
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• pp.457-460
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• 2005

Nano-sized titanium oxide and zirconium oxide powders were synthesized by hydrolysis of titanium isopropoxide $[Ti(OC_3H7)_4]$ and zirconium tetrachloride ($ZrC1_4$) via a sol-gel technique. Lead titanate powders were prepared by mixing $TiO_2$ precursors with PbO slurry made with dilute $NH_4OH$. Lead zirconate titanate powders were, then, synthesized by mixing $PbTiO_3$ with $ZrO_2$ powders. The goal of this research was to obtain the $PbZrTiO_3(PZT)$ powders and sintering these powders at low temperature. The $PbTiO_3$ and PZT powders after firing were analyzed by X-ray diffraction(XRD) and transmission electron microscopy(TEM) was utilized to observe the shape and size of the synthesized nano-particles. In the XRD pattern, the well-crystallized PZT phase could be obtained in consequence of firing at $900^{\circ}C$. SEM micrographs also showed that grains of PZT were relatively well grown with the size of the range of $2{\~}4{\mu}m$. The densified perovskite structure of $PbZrTiO_3$ could be obtained by sintering at temperature as low as $900^{\circ}C$. Characterization of the samples showed improved piezoelectric properties.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.2
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• pp.57-62
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• 2011

The energy conversion efficiency of DSSCs (Dye-Sensitized Solar Cells) is dependent on the powder size, the structure, and the morphology of $TiO_2$ electrode. The higher efficiency is obtained with high surface area of the nanoanatase-$TiO_2$ powder adsorbed onto a lot more of the dye. Also, the enhancement of light scattering increases the efficiency with high adsorption of the dye. Powder size, crystalline phase, and shape of $TiO_2$ obtained by hydrothermal method have 15-20 nm, anatase and round. $TiO_2$ electrode has fabricated with the mixture of scattering $TiO_2$ particle with 0.4 ${\mu}m$ in nano-sized powder. Conversion efficiency of series of DSSCs was measured with volume fraction of scattering particle. Photovoltaic characteristics of DSSCs with 10% scattering particles are 3.51 mA for Jsc (short circuit current), 0.79 V for Voc(open circuit potential), filling factor 0.619 and 6.86% for efficiency. Jsc was improved by 11% and enhancement of efficiency by 0.77% compared with that of no scattering particles. The confinement of inserted light by light scattering particles has more increase of the injection of exiton(electron-hole pair) and decrease of moving path in electron. Efficiencies of DSSCs with more than 10% for scattering particles have reduced with increasing the pore in the $TiO_2$ electrode.

• Journal of the Korean Ceramic Society
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• v.42 no.8 s.279
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• pp.561-566
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• 2005

For the homogeneous dispersion of $ZrO_2$ particles in $Al_2O_3/ZrO_2$ceramics, Zr-precusors were mixed with oxide $Al_2O_3$powders by chemical routes such as partial precipitation or partial polymerization of Zr-nitrate solutions. In case of the mechanical mixing of ultrafine $Al_2O_3$ and $ZrO_2$ oxide powders, relatively homogeneous dispersion was difficult to achieve so that the particle size and distributions of $ZrO_2$ were relatively inhomogeneous after sintering at high temperature. But when the Zr-Y-hydroxide were co-precipitated to ultrafine $Al_2O_3$ oxide powders followed by calcinations, homogeneous dispersion of nano-sized $ZrO_2$ particles in $Al_2O_3/ZrO_2$ composite ceramics were obtained. But because of the coalescence of dispersed $ZrO_2$ particles, dispersed $ZrO_2$ was grown up to more than 0.2${mu}m$ (200 nm) when sintered at the temperature of higher than $1500^{\circ}C$ But when the sintering temperature was kept to lower than $1400^{\circ}C$ by using nano-sized $\alpha-alumina$, the particle size of dispersed $ZrO_2$ could be sustained below 0.1 ${\mu}m$. But the coalescence of dispersed $ZrO_2$ between $Al_2O_3$ particles could not be avoided so that the mechanical properties were not enhanced contrary to the expectations. So Zr-polyester precursors were precipitated and coated to the surface of ultrafine $\alpha-alumina$ powders by the polymerization of Ethylene Glycol with Citric Acid and Zirconium Nitrate. By this dispersion much more uniform dispersion of $ZrO_2$ was achieved at $1450\~1600^{\circ}C$ of sintering temperature ranges. And due to especially discrete dispersion of $ZrO_2$ between $Al_2O_3$ particles, their mechanical strength was more enhanced than mechanical mixing or hydroxide precipitation methods.

• Journal of Technologic Dentistry
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• v.29 no.1
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• pp.121-131
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• 2007

A preparation process's conditions of aqueous sol which contains anatase-type nano titania particles with photocatalyic properties was established by using Yoldas process, so called, DCS(Destabilization of Colloidal Solution) process in this study. And crystal size change and phase transformation of titania particles in aqueous titania sol depending on reaction conditions was investigated by a light scattering method and XRD analysis of frozen dried powders, respectively. This sol with photo catalytic nano titania particles was used to the following hydrophilic hybrid coating film's fabrication and its properties was evaluated. Subsequently, for coating film using the above mentioned aqueous titania sol, non-aqueous titania sol was prepared without any chemical additives and its time stability according to aging time was investigate. By using the above mentioned aqueous titania sol and non-aqueous sol, a complex oxide coating sol for metal and ceramic substrate and a organic-inorganic hybrid coating sol for polymer substrate was prepared and it's hydrophilicity depending on UV irradiation conditions was evaluated. As a conclusions, the following results were obtained. (1)Aqueous titania sol The average particle size of titania in formed aqueous titania sol was distributed between 20$\sim$90nm range depending on reaction conditions. And the crystal phase of titania powders obtained by frozen drying method was changed from amorphous state to anatase and subsequently transformed to rutile crystal phase and it is attributed to concentration gradient in aqueous sol. (2)Non-aqueous titania sol Non-aqueous titania sol was prepared using methanol as a solvent and a little distilled water for hydrolysis and nitric acid as a catalyst were used. The obtained non-aqueous titania sol was stable at room temperature for 20 days. Additionally, non-aqueous titania sol with addition of chealating reagent such as acethylaceton and ethylene glycol prolonged the stability of sol by six months. (3)Complex sol and hybrid sol with super hydrophilicity The above mentioned aqueous titania sol as a main photocataylic component and non-aqueous titania sol as a binder for coating process was used to prepare a complex sol used for metal, ceramic and wood material substrate and also to prepare the organic-inorganic hybrid sol for polymer substrate such as polycarbonate and polyethylene, in which process APMS(3-Aminopropyltrimethoxysilane), GPTS(3-Glycidoxypropyl-trimethoxysilane) as a hydrophilic silane compound and HEMA(2-Hydroxyethyl methacrylate) as a forming network in hybrid coating film were used. The hybrid coating film such as prepared through this process showed a superhydrophilicity below 1$10^{\circ}$ depending on processing conditions and a pencil's hardness over 6 H.

• Journal of Korean Neurosurgical Society
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• v.63 no.6
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• pp.698-706
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• 2020

Objective : To study the physiochemical characteristics of podophyllotoxin (PPT) conjugated stearic acid grafted chitosan oligosaccharide micelle (PPT-CSO-SA), and evaluate the ability of the potential antineoplastic effects against glioma cells. Methods : PPT-CSO-SA was prepared by a dialysis method. The quality of PPT-CSO-SA including micellar size, zeta potential, drug encapsulation efficiency and drug release profiles was evaluated. Glioma cells were cultured and treated with PPT and PPT-CSO-SA. The ability of glioma cells to uptake PPT-CSO-SA was observed. The proliferation of glioma cells was determined by 3-[4, 5-dimethyl-2-thiazolyl]-2, 5-diphenyl-2H-tetrazolium bromide (MTT) assay. The apoptosis and morphology of U251 cells were observed by 4',6-Diamidino-2-phenylindole dihydrochloride (DAPI) dye staining. Cell cycle analysis was performed by flow cytometry. The migration ability of U251 cells was determined by wound healing test. Results : PPT-CSO-SA had nano-level particle size and sustained release property. The encapsulation efficiency of drug reached a high level. The cellular uptake percentage of PPT in glioma cells was lower than that of PPT-CSO-SA (p<0.05). The inhibitory effect of PPT-CSO-SA on glioma cells proliferation was significantly stronger than that of PPT (p<0.05). The morphologic change of apoptosis cell such as shrinkage, karyorrhexis and karyopyknosis were observed. The percentage of U251 cells in G2/M phase increased significantly in the PPT-CSO-SA group compared with PPT group (p<0.05). Compared with the PPT group, the cell migration ability of the PPT-CSO-SA group was significantly inhibited after 12 and 24 hours (p<0.05). Conclusion : PPT-CSO-SA can effectively enhance the glioma cellular uptake of drugs, inhibit glioma cells proliferation and migration, induce G2/M phase arrest of them, and promote their apoptosis. It may be a promising anti-glioma nano-drug.

• Journal of the Korean Chemical Society
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• v.61 no.1
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• pp.29-33
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• 2017

Formation of Au particles in nonstoichiometric $Cu_{2-x}{^I}Cu{_2}^{II}O_{3-{\delta}}$ ($x{\approx}0.20$; ${\delta}{\approx}0.10$) oxide from aniline + hydrochloric acid mixtures and chloroauric acid in the ratios 30 : 1; 60 : 1; 90 : 1 (S1-S3) by volume and 0.01 mol of copper acetate, $Cu(OCOCH_3)_2.H_2O$, in each case is performed by sol-gel growth. Powder x-ray diffraction (XRD) results show Au particles are dispersed in tetragonal nonstoichiometric dicopper (I) dicopper (II) oxides, $Cu_{2-x}{^I}Cu{_2}^{II}O_{3-{\delta}}$ ($x{\approx}0.20$; ${\delta}{\approx}0.10$). Average crystallite sizes of Au particles determined using Scherrer equation are found to be in the approximate ranges ${\sim}85-140{\AA}$, ${\sim}85-150{\AA}$ and ${\sim}80-150{\AA}$ in S1-S3, respectively which indicate the formation of Au nano-micro size particles in $Cu_{2-x}{^I}Cu{_2}^{II}O_{3-{\delta}}$ ($x{\approx}0.20$; ${\delta}{\approx}0.10$) oxides. Hysteresis behaviour at 300 K having low loop areas and magnetic susceptibility values ${\sim}5.835{\times}10^{-6}-9.889{\times}10^{-6}emu/gG$ in S1-S3 show weakly ferromagnetic nature of the samples. Broad and isotropic electron paramagnetic resonance (EPR) lineshapes of S1-S4 at 300, 77 and 8 K having $g_{iso}$-values ${\sim}2.053{\pm}0.008-2.304{\pm}0.008$ show rapid spin-lattice relaxation process in magnetic $Cu^{2+}$ ($3d^9$) sites as well as delocalized electrons in Au ($6s^1$) nano-micro size particles in the $Cu_{2-x}{^I}Cu{_2}^{II}O_{3-{\delta}}$ ($x{\approx}0.20$; ${\delta}{\approx}0.10$) oxides. Broad and weak UV-Vis diffuse reflectance optical absorption band ~725 nm is assigned to $^2B_{1g}{\rightarrow}^2A_{1g}$ transitions, and the weak band ~470 nm is due to $^2B_{1g}{\rightarrow}^2E_g$ transitions from the ground state $^2B_{1g}$(${\mid}d_{x^2-y^2}$>) of $Cu^{2+}$ ($3d^9$) ions in octahedral coordination having tetragonal distortion.