Papers by Author: Hyung Shik Shin

Abstract: Cubic shaped Magnesium oxide nanoparticles were successfully synthesized by sol-gel method using magnesium nitrate and sodium hydroxide at room temperature. Hydrated Magnesium oxide nanoparticles were annealed in air at 300 and 500°C. X-ray diffraction patterns indicate that the obtain nanoparticles are in good crystallinity, pure magnesium oxide periclase phase with (200) orientation. Morphological investigation by FESEM reveals that the typical sizes of the grown nanoparticles are in the range of 50-70nm. Powder composition was analyzed by the FTIR spectroscopy and the results confirms that the conversion of brucite phase magnesium hydroxide in to magnesium oxide periclase phase was achieved at 300°C.The Thermo-gravimetric analysis showed the phase transition of the synthesized magnesium oxide nanoparticles occurs at 280-300°C.

Abstract: The double-layered microspheres play an important role in controlling drug delivery for pharmaceutical application, because of the low initial burst compared with single-layered spheres and targetable delivery to specific organ. But it has drawback in loading drug and controlling size. In this study, we developed double-layered spheres using relatively simple oil-in-water (O/W) solvent evaporation method using bovine serum albumin (BSA) as water-soluble protein and poly(D,L-lactide-co-glycolide) (PLGA). BSA/PLGA double-layered microspheres were fabricated using O/W solvent evaporation method and investigated the specific character of double-layered microspheres according to the kind of surfactants. In SEM observation, double layered microsphere had spherical shape and smooth surface without pores. And the double layered microsphere using O/W solvent evaporation method was transparency because of slow evaporation of solvent. In fluorescent observation, we observed the fluorescent core in the double-walled spheres composed of FITC-BSA and PLGA using fluorescent observation. In the case of polyvinylalcohol as emulsifier, the yield was better than gelatin. As decreased concentration of PLGA, the size of double-layered microspheres deceased.

Abstract: Maghemite and hematite nanospheres were synthesized by using the Sol-gel technique. The structural properties of these nanosphere powders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM),and pore size distribution.Hematite phase shows crystalline structures.The mean particle size that resulted from BET and XRD analyses were 4.9 nm and 2 nm. The field emission scanning electron microscopy shows iron-oxide powder is composed of nanosized particles, but in nanosized aggregates (agglomeration of particles). It can be seen from transmission electron microscopy that the size of the particles are very small which is in good agreement with the FESEM and the Xray diffraction. TEM and FESEM confirmed that the iron-oxide powder is composed of sizes from 8 nm to 10 nm. The BET and pore size method were employed for specific surface area determination.