• Proceedings of the Korean Magnetic Resonance Society Conference
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• 2002.01a
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• pp.6-6
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• 2002

• Journal of the Korean Chemical Society
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• v.59 no.2
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• pp.136-141
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• 2015

We have discovered that quercetin, once coated on the CdSe and CdSe-CdS quantum dots (QDs), becoming highly water soluble. In the present work, we have successfully synthesized CdSe/CdS/N-Acetyl-L-Cysteine(NAC)/Quercetin nano-composites in the aqueous solution. The products were characterized using UV-vis spectroscopy, X-ray powder diffraction, fluorescence spectroscopy, and Fourier transform infrared spectroscopy. The transmission electron microscopy (TEM) tests indicated that our nano-composite products are highly stable with homogeneous particle size and great monodispersity. Quercetin coated nano-composite CdSe/CdS/NAC/Quercetin showed different fluorescence behavior from that of CdSe/CdS/NAC. Most amazingly, the synthesized CdSe/CdS/NAC/Quercetin nano-composite exhibits strong antibacterial activity. The combination of the strong fluorescence and its antibacterial activity makes the quercetin modified quantum dots as a potential candidate for cancer targeted therapy and other cancer treatments.

• Polymer(Korea)
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• v.39 no.1
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• pp.6-12
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• 2015

In order to improve the poor water solubility of aceclofenac, it was loaded into solid Kollidon VA 64 dispersion prepared by spray drying and rotary evaporation methods using different drug and polymer ratios. Morphology and physicochemical behavior of the aceclofenac loaded solid dispersions was analyzed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), and differential scanning calorimetry (DSC). Encapsulation efficiency and dissolution behavior in a simulated intestinal juice of aceclofenac in the solid dispersions was measured using HPLC and the latter was compared with that of the active pharmaceutical ingredient (API) and Airtal$^{(R)}$. It was demonstrated that two methods could significantly improve the dissolution behavior of aceclofenac.

• Polymer(Korea)
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• v.39 no.1
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• pp.33-39
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• 2015

Olmesartan affiliated to biopharmaceutics classification system class 2 is a poorly water soluble drug. For this reason, olmesartan showed a low bioavailability and a lot of difficulties in the process of designing the pharmaceutical formulation. We prepared the solid dispersions of olmesartan. We confirmed the dissolution rate of drug which was prepared by manufacturing. The pharmaceutical formulation of solid dispersions was designed by using PVP as water soluble polymer. We analyzed morphological feature of solid dispersion by employing a scanning electron microscope. Then, the crystalline property of solid dispersion was confirmed through X-ray diffraction and differential scanning calorimeter. Also, the chemical change of solid dispersion was confirmed by the Fourier transform infrared spectroscopy. In vitro dissolution test was used to analyze the dissolution rate of solid dispersion. The prepared solid dissolution olmesartan confirmed the dissolution rate in the pH 1.2. It was compared with olmetec and improved dissolution rate through solid dispersion.

• Polymer(Korea)
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• v.35 no.2
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• pp.113-118
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• 2011

Solid dispersion is used to improve the solubility of water-insoluble drug. Release properties depend on the characteristics of polymer and the physicochemical properties of solid dispersion. In this study the solid dispersions of ibuprofen and cellulose acetate were prepared using spray-drying and rotary evaporation. The physicochemical properties of the solid dispersions were analyzed by SEM, XRD, DSC, and FTIR. The hydrophilicity of polymer was analyzed by measuring the contact angle of water. The results of DSC and XRD analysis demonstrated that the crystallinity of ibuprofen was changed by solid dispersion preparation. The results of contact angle showed that hydrophilicity was proportional to polymer content. Release profile showed that for solid dispersion. the release rate of ibuprofen decreased as polymer content increased in intestinal juice (pH 6.8). The dissolution rate of ibuprofen was improved with increasing polymer content in gastric juice (pH 1.2).

• Polymer(Korea)
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• v.38 no.5
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• pp.656-663
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• 2014

Atorvastatin calcium-loaded polyoxalate (POX) microspheres were prepared by an emulsion solvent-evaporation/ extraction method of oil-in-oil-in-water ($O_1/O_2/W$) for sustained release. We investigated the release behavior according to initial drug ratio, molecular weight ($M_w$) and concentration of POX and concentration of emulsifier. The microsphere was characterized on the surface, the cross-section morphology and the behavior of atorvastatin calcium release for 10 days by scanning electron microscopy (SEM) and high performance liquid chromatography (HPLC). The analysis of crystallization was analyzed to use X-ray diffraction (XRD), differential scanning calorimeter (DSC) and Fourier transform infrared (FTIR). These results showed that the release behaviors can be controlled by preparation conditions.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.72-72
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• 2011

Recently, Zinc oxide (ZnO) nano-structures have been received attractive attention because of their outstanding optical and electrical properties. It might be a promising material considered for applications to photonic and electronic devices such as ultraviolet light emitting diode, thin film transistor, and gas sensors. ZnO nano-structures can be typically synthesized by the VLS growth mode and self-assembly. In the VLS growth mode using various growth techniques, the noble metal catalysts such as Au and Sn were used. However, the growth of ZnO nano-structures on nano-crystalline Au seeds using radio frequency (RF) magnetron sputtering might be explained by the profile coating, i.e. the ZnO nano-structures were a morphological replica of Au seeds. Ga doped ZnO (ZnO:Ga) nano-structures using this concept were synthesized and characterized by XRD, AFM, SEM, and TEM. We found that surface morphology is drastically changed from initial islands to later sun-flower typed nano-structures. We will present the structural evolution of ZnO:Ga nano-structures with increasing the film thickness.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.147-150
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• 2005

Low actuation voltage and no contact stiction are the important factors to apply MEMS RF switches to mobile devices. Conventional electrostatic MEMS RF switches require several tens of voltages for actuation. In this paper we propose PAS MEMS RF switch which adopt PZT actuators and seesaw cantilevers to meet the above requirements. The fundamental structures of PAS MEMS switch were designed, optimized, and fabricated. Through the developed processes PAS SPDT MEMS RF switches were successfully fabricated on 4" wafers and they showed good electrical properties. The driving voltage was less than 5 volts. And the insertion loss was -0.5dB and the isolation was 35dB at 5GHz. The switching speed was about 5kHz. So these MEMS RF switches can be applicable to mobile communication devices or wireless multi-media devices at lower than 6GHz.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.1030-1033
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• 2004

We herewith report for the effect of dielectric surface modification on the electrical characteristics of organic thin-film transistors (OTFTs). The kist-jm-1 as an organic molecule for the surface modification is deposited onto the surface of zirconium oxide ($ZrO_2$) gate dielectric layer. The OTFTs are elaborated on the flexible plastic substrates through 4-level mask process to yield a simple fabrication process. In this work, we also have examined the dependence of electrical performance on the interface surface state of gate dielectric/pentacene, which may be modified by chemical properties in the gate dielectric surface.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04a
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• pp.51-52
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• 2008

A single gap transflective liquid crystal display(LCD) driven by fringe electric field in the transmissive(T) region and vertical electric field in the reflective(R) region was designed. Because the pretilt angle is formed in $53^{\circ}$ through polymerization of an UV curable reactive mesogen(RM) monomer at the surface, the effective cell retardation $(d{\Delta}n_{eff})$ value of the R region becomes half of that in the T region where the LCs are homogenously aligned. Consequently, a transflective display driven by a vertical and fringe electric field with a single cell gap and single gamma curves is realized.