• Korean Chemical Engineering Research
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• v.51 no.5
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• pp.597-601
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• 2013

In this study, we present simple microfluidic approach for the synthesis of monodisperse microcapsules by using droplet-based system. We generate double emulsion through single step in the microfluidic device having single junction while conventional approaches are limited in surface treatment for the generation of double emulsion. First, we have injected disperse fluid containing FC-77 oil and photocurable ethoxylated trimethylolpropane triacrylate (ETPTA) and water containing 3 wt% poly(vinyl alcohol) (PVA) as continuous phase into microfluidic device. Under the condition, we easily generate double emulsion with high monodispersity by using flow focusing. The double emulsion droplets are transformed into microcapsules under the UV irradiation via photopolymerization. In addition, we control thickness of double emulsion's shell by controlling flow rate of ETPTA. We also show that the size of double emulsions can be controlled by manipulation of flow rate of continuous phase. Furthermore, we synthesize microcapsules encapsulating various materials for the application of drug delivery systems.

• Journal of Adhesion and Interface
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• v.12 no.4
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• pp.133-137
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• 2011

Exfoliated graphite oxide (EGO) was prepared by graphite oxide in an aqueous solution of TMAOH. The hybrid graphene/Zn-Al LDH material was fabricated by the hydrothermal reduction of the solution of EGO, $Zn(NO_3)_2{\cdot}6H_2O$, $Al(NO_3)_3{\cdot}9H_2O$, urea, and trisodium citrate. That is, metal ions were absorbed on the surface of EGO, and Zn-Al LDH material was randomly dispersed on the surface of graphene along with a reduction process of EGO to graphene by hydrothermal treatment. The composition, morphology, and thermal property of the obtained graphene-based hybrid material were studied by FE-SEM, EDX, TEM, FT-IR, XRD, TGA, and DSC.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.4
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• pp.509-520
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• 1996

Ultrafine calcim carbonate powders with the size of $0.05~0.1\;{\mu}m$ and the calcite phase were synthesized by the nozzle spouting method, which could be only obtained when high calcium ion concentration within slurry was maintained at the beginning of the reaction. But, in the regions of low ${Ca(OH)}_2$ concentration (0.5~1.0 wt%) or high ${Ca(OH)}_2$ concentration (<3.0 wt%), synthesized calcium carbonate powder was shown the large particle size with agglomeration. To obtain ultrafine calcium carbonate powder in this region, the methods of slurry circuation and $CO_{2}$ gas supply were changed during reaction. Resultly, it was possible to synthesize ultrafine particles (${\approx}0.05{\mu}\textrm{m}$)in the regions of low ${Ca(OH)}_2$ concentration (${\approx}0.5wt%$) and high ${Ca(OH)}_2$ concentration (${\approx}0.5wt%$), which can not be obtained the fine calcium carbonate powder still now.

• Clean Technology
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• v.14 no.3
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• pp.218-223
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• 2008

Decomposition of reactive organic compound dispersed in microemulsion media by hydroxide ions and proton ions generated during electrolysis was tried and the half-lifes for decomposition were compared. Absorbance of p-nitrophenoxide produced from the decomposition of p-nitrophenylacetate (PNPA) was followed to find the rate of decomposition. The applied voltage, temperature, and the amount of substrate were changed to see the effects on the decomposition rate. The advantages of electrolysis in microemulsion system were the high solubilizing capacity of substrate, easy control of decomposition rate, low operation cost, no need for any addition of chemicals, and no byproducts. The mechanism of decomposition and the application to water purification were discussed.

• Journal of the Korean Ceramic Society
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• v.40 no.9
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• pp.902-908
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• 2003

Au/TiO$_2$ core-shell structure nanoparticles were synthesised by sol-gel process, and the morphology and crystallinity of TiO$_2$ shell were investigated by TEM and UV-Vis. absorption spectrometer. Au/TiO$_2$ core-shell structure nanoparticles could be prepared by the hydrolysis of TOAA (Titanium Oxide Acethylacetonate) in Au colloid ethanol solution with $H_2O$. The thickness of TiO$_2$ shell on the surface of Au particles was about 1 nm. To investigate the crystallinity of TiO$_2$ shell, UV light with 254 nm and radioactive lay of $^{60}$ CO were irradiated on the TiO$_2$ coated Au colloid ethanol solution. The surface plasmon phenomenon of Au nanoparticles appeared only when the radioactive lay was irradiated on the TiO$_2$ coated Au colloid ethanol solution. From these results, it was found that the TiO$_2$ shell was amorphous and the MUA (Mercaptoundecanoic Acid) layer on the Au particle for its dispersion didn't act as an obstacle to disturb the movement of electron onto the surface of Au particle.

• Journal of the Korean Magnetics Society
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• v.19 no.1
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• pp.28-34
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• 2009

Magnetic nanoparticles are widely used for bio-medical applications such as MRI contrast agents, drug-delivery systems, cell separation and hyperthermia, thanks to their unique magnetic properties and physico-chemical characteristics. In the early stage, efforts were focused on synthesis of uniform nanoparticles of desired dimension to achieve targeted, stable functionalities. Recently, it has been of great interest in dispersion of such nanoparitcles in aqueous solution and to render the nanoparticles bio-compatible with biofunctionality on request for utilization in bio-medical fields. In this paper, we survey the research status and give prospective on future work of magnetic nanoparticles for biomedical applications.

• Applied Chemistry for Engineering
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• v.30 no.4
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• pp.487-492
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• 2019

Nano flexible vesicles encapsulating an adenosine, an active ingredient for anti-wrinkle, were prepared for the transdermal delivery. The nano flexible vesicle is usually composed of phospholipid, ethanol, and lysolecithin, which is a type of liquid crystalline one made by dispersing the liquid crystalline phase formed through a hydration process into a water phase. In this study, the Taguchi method, one of the experimental design methods, was applied to investigate the factors affecting the vesicle droplet size. Signal to noise (S/N) ratios for the smaller the better characteristics of vesicle droplet size were calculated using the Taguchi orthogonal array. The composition of ethanol and lysolecithin in the vesicle constituents and the amount of aqueous solution added in the hydration process were main factors that had a great effect on the vesicle droplet size and ANOVA test showed that these factors were significant at 95% confidence level.

• Korean Chemical Engineering Research
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• v.60 no.1
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• pp.139-144
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• 2022

This study reports a microfluidic approach to produce monodisperse hydrogel microparticles in a simple and highly efficient manner. Specifically, we produce double emulsion drops with a thin oil shell surrounding an aqueous prepolymer solution, which is solidified via UV-induced free radical polymerization. When they are dispersed in an aqueous solution, the oil shell is dewetted due to the absence of surfactants, resulting in production of highly uniform hydrogel microparticles (C.V.=1%). Results show that production of monodisperse hydrogel microparticles with controllable size and composition can be achieved with minimal use of oil unlike water-in-oil (w/o) single emulsion-based approach. Furthermore, in-depth study of flow patterns in microfluidic device using a phase diagram exhibits a crucial relationship among relative flow rates while providing windows of readily controllable parameters for reliable manufacturing of hydrogel microparticles.

• Applied Chemistry for Engineering
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• v.20 no.4
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• pp.381-385
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• 2009

A basic objective is the preparation and surface studies of supported molten salt catalysts because molten salts can stay as the liquid phase in the range of the ordinary reaction temperature. Many kinds of metal salt mixtures for the formation of molten salt phase are appliable but CuCl and KCl were selected in this study because Cu is considered catalytically reactive in many reactons. The loading of the molten salt was selected as 25 vol% of the total pore volume of ${\gamma}-alumina$ to provide reasonable exposed surface area. The surface structure of catalysts containing molten salts in the ${\gamma}-alumina$ was studied using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). CuCl and KCl were added into the ${\gamma}-alumina$ using concentrated hydrochloric acid solution by the impregnation technique. The surfaces of the prepared catalysts before and after heat treatments were compared and they suggested that the heat treatment of catalysts helped the formation of molten-salt although the surface compositions of CuCl and KCl were not uniform.

• Applied Biological Chemistry
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• v.44 no.2
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• pp.109-115
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• 2001

The foliar uptake of dimethomoiph induced by several nonionic surfactants was measured in order to study the correlations between the uptake rate of dimethomorph and the fungicidal activity to cucumber downy mildew. Dimethomorph was not absorbed in cucumber leaf in the absence of activator surfactant. And the curative effect of dimethomoiph WP to cucumber downy mildew was very low under the concentration of 250 ${\mu}g/ml$. But dimethomorph uptake was remarkably enhanced by addition of nonionic surfactants, such as polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, and polyoxyethylene stearyl ether. And the curative effect to cucumber downy mildew was enhanced with proportion to uptake rate of dimethomorph. The protective effect to cucumber downy mildew, however, tends to decrease with the increase of foliar uptake of dimethomorph. The uptake rate of dimethomorph to cucumber leaf was proportional to the content of polyoxyethylene cetyl ether in formulation, but was decreased with dilution.