• Bulletin of the Korean Chemical Society
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• 제35권7호
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• pp.1939-1943
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• 2014

Solid dispersion (SD) system of everolimus (EVR) with Gelucire 50/13 (Stearoyl polyoxyl-32 glycerides) was prepared using melt granulation technique with the aim of improving the physicochemical properties and dissolution rate. The solid state characterization using scanning electron microscopy and X-ray powder diffraction, indicated that the drug was homogeneously distributed in the surfactant carrier in a stable amorphous form. The dissolution rate of EVR from the optimized SD composed of the drug, Gelucire 50/13 and microcrystalline cellulose in a weight ratio of 1:5:10, was markedly rapid and higher than that from the drug powder and the market product (Afinitor$^{(R)}$, Novartis Pharmaceuticals) in all dissolution mediums tested from pH 3.0 to pH 6.8. The results of this study suggest that formulation of SD with Gelucire 50/13 using melt granulation procedure may be a simple and promising approach for improving the dissolution rate and oral absorption of the anti-cancer agent without the need for using an organic solvent.

• Bulletin of the Korean Chemical Society
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• 제28권3호
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• pp.397-402
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• 2007

Restenosis after percutaneous coronary intervention (PCI) continues to be a serious problem in clinical cardiology. To solve this problem, drug eluting stents (DES) with antiproliferative agents have been developed. Variable local drug delivery systems in the context of stenting require the development of stent manufacture, drug pharmacology and coating technology. We have worked on a system that integrates electrophoretic deposition (EPD) technology with the polymeric nanoparticles in DES for local drug delivery and a controlled release system. The surface morphology and drug loading amount of DES by EPD have been investigated under different operational conditions, such as operation time, voltage and the composition of media. We prepared poly-D,L-lactide-co-glycolic acid (PLGA) nanoparticles embedded with curcumin, which was done by a modified spontaneous emulsification method and used polyacrylic acid (PAA) as a surfactant because its carboxylic group contribute negative charge to the surface of CPNPs (?53.5 ± 5.8 mV). In the process of ‘trial and error' endeavors, we found that it is easy to control the drug loading amount deposited onto the stent while keeping uniform surface morphology. Accordingly, stent coating by EPD has a wide application to the modification of DES using various kinds of nanoparticles and drugs.

• 청정기술
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• 제23권3호
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• pp.325-330
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• 2017

This study presents the preparation of n-tetradecane-in-water emulsions with different weight ratios of n-tetradecane and water, and their potential application in packaging and shipping vaccines. The size and distribution of the n-tetradecane droplets are characterized using optical microscopy and light scattering methods, respectively. The thermal properties of the emulsions are determined using the T-history method. In the results, the emulsions, which are comprised of 17 ~ 30 wt% oil, 3 wt% surfactant, and 67 ~ 80 wt% water, are stable and have droplet sizes in the range of 100 to 800 nm. The thermal properties demonstrate that subcooling is prevented through increasing the droplet size. The results indicate that the n-tetradecane/water emulsions containing 25 ~ 35 wt% n-tetradecane, with a melting point of $2{\sim}8^{\circ}C$ and a latent heat of $227.0{\sim}250.8kJ\;kg^{-1}$, are good candidate materials for packaging and shipping vaccines.

• 대한화학회지
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• 제35권5호
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• pp.506-511
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• 1991

In-Morin 착물에 대한 흡착벗김전압전류법적 연구를 HMDE를 사용하여 pH 3.20의 0.1M 아세테이트 완충용액에서 수행하였다. 흡착 현상들을 미분펄스전압전류법으로 관찰하였으며, HMDE의 표면에 흡착된 착물의 환원 전류에 미치는 여러 분석 조건들에 과하여 논의하였다. 또한 여러 다른 금속이온들과 계면활성제의 방해효과에 관해서도 검토하였다. 본 연구에서의 검출한계는 90초의 흡착시간을 적용하였을 때 2.6nM이었으며, 4${\mu}g$/l의 In을 7회 분석하였을 때 상대표준편차는 2.0%이었다.

• 공업화학
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• 제17권6호
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• pp.625-632
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• 2006

임계 마이셀 농도의 온도 의존성을 통계 역학적으로 고찰하였다. 본 논문에서 논의된 단순하고 소박한 모델은 임계 마이셀 농도(CMC)가 온도에 대해서 ln CMC= A+BT+C/T+D ln T와 같이 변함을 말해준다. 여기에서 T는 온도이고 A, B, C, D는 마이셀을 이루는 계면활성제 분자의 성질에 의존하는 상수이다. 모델에서 얻어진 식은, 온도에 따른 CMC 측정 자료를 잘 맞춤하는 것으로 평가된, 기존의 Muller와 Lim의 식을 결합한 형태이다. 그러므로 본 논문에서 제안된 CMC의 온도 의존성에 대한 모델은 Muller와 Lim의 식에 대한 이론적인 토대를 제공한다.

• 한국전기전자재료학회논문지
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• 제16권12S호
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• pp.1181-1186
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• 2003

Chemical Mechanical Polishing (CMP) is an essential dielectric planarization in multilayer microelectronic device fabrication. In the CMP process, it is necessary to minimize the extent of surface defect formation while maintaining good planarity and optimal material removal rates. The polishing mechanism of W-CMP process has been reported as the repeated process of passive layer formation by oxidizer and abrasion action by slurry abrasives. Thus, it is important to understand the effect of oxidizer on W passivation layer, in order to obtain higher removal rate (RR) and very low non-uniformity (NU %) during W-CMP process. In this paper, we compared the effects of oxidizer or W-CMP process with three different kind of oxidizers with 5 wt% hydrogen peroxide such as Fe(NO$_3$)$_3$, H$_2$O$_2$, and KIO$_3$. The difference in removal rate and roughness of W in stable and unstable slurries are believed to caused by modification in the mechanical behavior of Al$_2$O$_3$ particles in presence of surfactant stabilizing the slurry.

• Macromolecular Research
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• 제14권5호
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• pp.545-551
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• 2006

Aqueous dispersions of pristine and functionalized (COOH- and $NH_2$-) multi-walled, carbon nanotubes (MWNTs) were prepared by using three types of surf act ants: sodium dodecyl sulfate (SDS, anionic), PEO-PPO-PEO (Pluronic P84, non-ionic), and poly(styrene/$\alpha-methyl$ styrene/acrylic acid) random terpolymer, i.e., alkali-soluble resin (ASR). The aggregate size, $\zeta-potential$, and storage stability of the MWNT aqueous dispersions were investigated by using dynamic light scattering and the turbidity method at room temperature. The exfoliation of the MWNT aggregates was determined by a UV-visible spectrophotometer and the morphology of the surfactant-coated MWNTs was observed by transmission electron microscopy (TEM). In all cases, ASR showed better dispersion stability with the smallest aggregate size, compared with the other surfactants, because of its unique molecular structure, i.e., randomly incorporated carboxylic acid groups and planar phenyl groups that can be irreversibly and effectively adsorbed on the MWNT surface. A predominantly-exfoliated morphology of MWNTs was observed in the presence of ASR from the strong intensity of the UV-vis spectrum at 263 nm.

• Bulletin of the Korean Chemical Society
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• 제31권11호
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• pp.3128-3132
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• 2010

A disposable solid-state pH sensor was realized by utilizing two nanoporous Pt (npPt) electrodes and a copolyelectrolytic junction. One nanoporous Pt electrode was to measure the pH as an indicating electrode (pH-IE) and the other assembled with copolyelectrolytic junction was to maintain constant open circuit potential ($E_{oc}$) as a solid-state reference electrode (SSRE). The copolyelectrolytic junction was composed of cationic and anionic polymers immobilized by photo-polymerization of N,N'-methylenebisacrylamide, making buffered electrolytic environment on the SSRE. It was expected to make. The nanoporous Pt surrounded by a constant pH excellently worked as a solid state reference electrode so as to stabilize the system within 30 s and retain the electrochemical environment regardless of unknown sample solutions. Combination between the SSRE and the pH-IE commonly based on nanoporous Pt yielded a complete solid-state pH sensor that requires no internal filling solution. The solid state pH sensing chip is simple and easy to fabricate so that it could be practically used for disposable purposes. Moreover, the solid-state pH sensor successfully functions in calibration-free mode in a variety of buffers and surfactant samples.

• Bulletin of the Korean Chemical Society
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• 제34권4호
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• pp.1065-1069
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• 2013

A highly sensitive electrochemical detection method for bisphenol A (BPA) has been developed by using multi-walled carbon nanotube (CNT)-doped titania-Nafion composite modified glassy carbon (GC) electrode. The CNT-titania-Nafion/GC electrode exhibited excellent electrocatalytic activity towards BPA. Therefore, the CNT-titania-Nafion/GC electrode showed improved voltammetric responses for BPA compared to that obtained with bare GC electrode. In addition, cetyltrimethylammonium bromide (CTAB), a cationic surfactant, was added into the BPA sample solution in order to accumulate BPA through hydrophobic interaction between CTAB and BPA. The CNT-titania-Nafion/GC electrode gave a linear response ($r^2$ = 0.999) for BPA from $1.0{\times}10^{-8}$ M to $5.0{\times}10^{-6}$ M with a detection limit of $9.0{\times}10^{-10}$ M (S/N = 3). The modified electrode showed good selectivity against interfering species and also exhibited good reproducibility. The present electrochemical sensor based on the CNT-titania-Nafion/GC electrode was applied to the determination of BPA in food package samples.

• 한국응용과학기술학회지
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• 제18권4호
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• pp.325-331
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• 2001

The critical micelle concentration (CMC) at which micelles start to form from a surfactant solution is usually measured in terms of conventional concentration units. However, the thermodynamic potentials are expressed in terms of mole fraction $X_{CMC}$ and $X_{CMC}$ cannot be directly measured experimentally. The Gibbs free energy, ${\Delta}G^{\ast}_{mic}$, in particular is related to $X_{CMC}$ through ${\Delta}G^{\ast}_{mic}$ = $RTlnX_{CMC}$. When it comes to CMC, the molar CMC, $C_{CMC}$, differs only by the proportionality $C^{-1}_{w}$ with $C_{w}$ being the molarity of water. Hence, $C_{CMC}$ is found to be a proper representation of CMC. However, in calculation of ${\Delta}G^{\ast}_{mic}$ and other thermodynamic potentials from the CMC, $X_{CMC}$ or $C_{CMC}/C_{w}$ should be used.