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One-step fabrication and photoluminescence of aluminasheathed GaN nanowires
곽동섭,권용정,조홍연,이종무,이종무 한양대학교 세라믹연구소 2013 Journal of Ceramic Processing Research Vol.14 No.4
Gallium nitride (GaN)/alumina (Al2O3) core-shell structures were successfully synthesized by a simple and one-step thermal evaporation method. We characterized their morphology, microstructures, and optical properties by SEM, TEM, EDX, and photoluminescence (PL). The core-shell structures were comprised of a core of single crystalline, GaN nanowires surrounded by a shell of Al2O3 tubular structures. We proposed a base-growth process as the dominant mechanism for the growth of the core/shell nanowires. We have discussed the possible reason for the preferential formation of the Al2O3 shells on the outside of the core-shell structures. In regard to the core/shell structures, an emission peak of 3.3 eV was observed in the roomtemperature PL measurements in addition to the GaN-associated peaks, and was attributed to the Al2O3 shell.
TiO2/SiOx Core-Shell Nanowires Generated by Heating the Multilayered Substrates
나한길,곽동섭,권용중,조홍연,이종무,김현우 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.4
By heating Au/TiN/Si substrates, we fabricated TiO2/SiOx core-shell nanowires. By changing the thickness of predeposited Au layers, we demonstrated that the thickness of the Au layer needs to be optimized to obtain nanowires. High-resolution transmission electron microscopy image, X-ray diffraction spectrum,and selected area electron diffraction pattern coincidentally revealed that the resultant core nanowires had a tetragonal rutile structure of TiO2, and the shell was comprised of amorphous SiOx. The dominant growth mechanism was a base-growth mode, in which Au played a catalytic role, resulting in morphological changes with variation of the Au layer thickness. The TiO2/SiOx core-shell nanowires exhibited a broad photoluminescence emission band, which comprised four peaks centered at 1.54, 2.34, 2.67, and 2.99 eV,respectively. We expected that the 1.54 eV- and 2.34 eV-centered peaks arised from the TiO2 core, whereas the 2.67 eV- and 2.34 eV-peaks were ascribed to both the TiO2 core and the SiOx shell.
나한길,곽동섭,권용중,Fan Xia,박원일,김현우 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.2
We have investigated the effects of the oxygen gas flow ratio in a synthesis process, ultimately producing thin (~40 nm in diameter) SnO2 nanowires. Scanning electron microscopy revealed that the oxygen partial pressure affected the diameter as well as the length of the nanowires. An X-ray diffraction investigation suggested that the grain size of the SnO2 phase was slightly increased with a decrease in the oxygen partial pressure. Lattice-resolved transmission electron microscopy (TEM)images, selected area electron diffraction, and micro-Raman spectroscopy coincidentally showed that the as-synthesized nanowires comprised a tetragonal SnO2 phase. Based on the analysis by fabricating field effect transistors, we found that the transport properties of SnO2 nanowires exhibited an n-type semiconductor characteristic.
김솔,곽동섭,이동진,이은성 한국고분자학회 2016 Macromolecular Research Vol.24 No.2
In this study, we developed porous poly(lactide-co-glycolide) (PLGA) microparticles (PM) exhibiting pH-activated drug release properties. The PMs were prepared via the water-in-oil-in-water (W1/O/W2) multi-emulsion method using PLGA, 3-diethylaminopropyl amine (DEAP)-conjugated hyaluronate (HA) (HA-DEAP), and an anticholinergic model drug (tiotropium). Here, HA-DEAP was incorporated into the PMs; it acted as a drug release activator, accelerating drug release. In vitro drug release studies revealed that the tiotropium was released from the PMs as their pores were destabilized by eletrostatic interactions between the carboxyl groups (negatively charged) of the HA molecules and the tertiary amine groups (positively charged) of the DEAP moieties under acidic environments. This PLGA microparticle system, which contains a HA-DEAP, could provide unique advantages in treating chronic obstructive pulmonary disease (COPD) with chronic respiratory acidosis.
Multifunctional nano-sized fullerenes for advanced tumor therapy
윤유석,곽동섭,이은성 한국약제학회 2017 Journal of Pharmaceutical Investigation Vol.47 No.1
There is an increasing demand for the development of functional photosensitizing nano-sized drugs. Fullerene, one of the new carbon molecules, has been considered to be a useful and versatile material for this purpose. Notably, fullerenes are water-insoluble, and they readily aggregate in aqueous solution. Therefore, fullerenes usually have been coupled with water-soluble, biocompatible, biodegradable polymers (e.g., polysaccharides, proteins, and other functional polymers), achieving their improved water-solubility and biocompatible properties. In particular, when fullerenes are paired with tumor-targeting ligands or stimuli-responsive polymers, these conjugates exhibit enhanced tumor recognition ability and improved tumor inhibition. Some groups encapsulated fullerenes into liposomes or nanoemulsions for various pharmaceutical purposes. This review provides an in-depth understanding of fullerene/polymer nanoparticles for effective fullerenemediated tumor therapy.