• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 추계학술대회 논문집
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• pp.331-332
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• 2012

• Journal of Microbiology and Biotechnology
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• 제17권9호
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• pp.1573-1578
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• 2007

An increasing number of applications is being developed for the use of nanoparticles in various fields. We investigated possible toxicities of nanoparticles in cell culture and in mice. Nanoparticles tested were Zn (300 nm), Fe (100 nm), and Si (10-20, 40-50, and 90-110 nm). The cell lines used were brain, liver, stomach, and lung from humans. In the presence of nanopaticles, mitochodrial activity decreased zero to 15%. DNA contents decreased zero to 20%, and glutathione production increased zero to 15%. None of them showed a dose dependency. Plasma membrane permeability was not altered by nanoparticles. In the case of Si, different sizes of the nanoparticles did not affect cytotoxicity. The cytotoxicity was also shown to be similar in the presence of micro-sized ($45\;{\mu}m$) Si particles. Organs from mice fed with nanoparticles showed nonspecific hemorrhage, lymphocytic infiltration, and medullary congestion. A treatment with the micro-sized particle showed similar results, suggesting that the acute in vivo toxicity was not altered by nano-sized particles.

• Advances in nano research
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• 제2권2호
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• pp.99-109
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• 2014

Experiments are performed to investigate the single-phase flow heat transfer augmentation of MWCNT/HT-B Oil in both smooth and micro-fin helical tubes with constant wall temperature. The tests in laminar regime were carried out in helical tubes with three curvature ratios of 2R/d=22.1, 26.3 and 30.4. Flow Reynolds number varied from 170 to 1800 resulting in laminar flow regime. The effect of some parameters such as the nanoparticles concentration, the dimensionless curvature radius (2R/d) and the Reynolds number on heat transfer was investigated for the laminar flow regime. The weight fraction of nanoparticles in base fluid was less than 0.4%. Within the applied range of Reynolds number, results indicated that for smooth helical tube the addition of nanoparticles to the base fluid enhanced heat transfer remarkably. However, compared to the smooth helical tube, the average heat transfer augmentation ratio for finned tube was small and about 17%. Also, by increasing the weight fraction of nanoparticles in micro-fin helical tubes, no substantial changes were observed in the rate of heat transfer enhancement.

• Applied Science and Convergence Technology
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• 제27권1호
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• pp.14-18
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• 2018

In order to understand the mechanism of the synthesis of particles using a plasma torch, it is necessary to understand the reaction mechanisms using a computer simulation. In this study, we have developed a simulation method to combine the Lagrangian scheme to follow microparticles and a nodal method to treat nanoparticles categorized with different particle sizes. The Lagrangian scheme includes the Coulomb force which affects the dynamics of larger particles. In contrast, the nodal method is adequate for the nanoparticles because the charge effect is negligible for nanoparticles but the number of nanoparticles is much larger than that of microparticles. This method is helpful to understand the dynamics and growth mechanism of micro- and nano-powder mixture observed in the experiment.

• 한국세라믹학회지
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• 제47권2호
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• pp.113-116
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• 2010

The silica coated $Fe_3O_4$ nanoparticles have been synthesized using a micro-emulsion method. The $Fe_3O_4$ nanoparticles with the sizes 6 nm in diameter were synthesized by thermal decomposition method. Hydrophobic $Fe_3O_4$ nanoparticles were coated silica using surfactant and tetraethyl orthosilicated (TEOS) as a $SiO_2$ precursor. Shell thickness of silica coated $Fe_3O_4$ can be controlled (11~20 nm) through our synthetic conditions. The $Fe_3O_4$ and silica coated $Fe_3O_4$ nano powders were characterized by transmission electron microscopy (TEM), x-ray diffraction (XRD) and vortex magnetic separation (VMS).

• Advances in nano research
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• 제3권4호
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• pp.243-255
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• 2015

In this investigation, ecotoxicity of nano and micro metal oxides, namely silica ($SiO_2$) and alumina ($Al_2O_3$), on the growth of green algae (Porphyridium aerugineum Geitler) is discussed. Effects of nano and micro particles on the growth, chlorophyll content and protein content of algae are analysed using standard protocols. Results indicate that $SiO_2$ nano and micro $SiO_2$ particles are non-toxic to P. aerugineum Geitler up to a concentration of 1000 mg/L. In addition, $Al_2O_3$ microparticles are less toxic to P. aerugineum Geitler, whereas $Al_2O_3$ nanoparticles are found to be highly toxic at 1000 mg/L. Moreover, $Al_2O_3$ nanoparticles decrease the growth, chlorophyll content, and protein content of tested algae. In addition, zeta potential and contact angle are also important in enhancing the toxicity of metal oxide nanoparticles in aquatic environment. This study highlights a new insight into toxicity evaluation of nanoparticles on beneficial aquatic organisms such as algae.

• 한국세라믹학회지
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• 제46권1호
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• pp.69-73
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• 2009

We report the preparation of nanocrystalline cobalt ferrite, $CoFe_2O_4$ particles and their surface coating with silica layers using micro emulsion method. The cobalt ferrite nanoparticles with the size 7nm are firstly prepared by thermal decomposition method. Hydrophobic nanoparticles were coated with silica using micro-emulsion method with surfactant, $NH_4OH$, and tetraethylorthosilicate (TEOS). Monodispersed and spherical silica coated cobalt ferrite nanoparticles have average particle diameter of 38 nm and narrow sized distribution.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1874-1879
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• 2008

It is not easy to detect nano-sized airborne particles (< 100 nm in diameter) in air. Therefore, the condensation of the nanoparticles alongside of the size-classification is needed for their detection. This paper proposes a hybrid (aerodynamic+electrical) particle classification and condensation device using a micro virtual impactor (${\mu}VI$). The ${\mu}VI$ can classify the nanoparticles according to their size and condense the number concentration of nanoparticles interested. Firstly, the classification efficiency of the ${\mu}VI$ was measured for the particles, polystyrene latex (PSL), ranging from 80 to 250 nm in diameter. Secondly, the nanoparticles, NaCl of 50 nm in diameter, were condensed by 4 times higher. In consequence, the output signal was amplified by 4 times (before condensation: 4 fA, after condensation: 16 fA). It is expected that the proposed device will facilitate the detection of nanoparticles.

• 대한환경공학회지
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• 제31권12호
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• pp.1069-1074
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• 2009

본 연구에서는 CuO와 ZnO의 입자 크기가 옥수수의 성장과 토양 미생물 군집에 미치는 독성을 microcosm 실험을 통하여 살펴보았다. 나노 입자는 micro 입자에 비해 옥수수의 biomass를 약 30% 감소시켜 나노 입자가 옥수수의 성장을 저해하는 것으로 나타났다. 토양 미생물 활성 지표인 Dehydrogenase activity는 CuO 나노 입자에서는 낮게 나타났으나 ZnO 나노 입자에서는 높게 나타났다. Biolog test 결과, CuO 나노 입자와 ZnO micro 입자에서 토양 미생물 다양성이 감소하는 것으로 나타났다. 그러므로, metal oxide의 나노 입자가 micro 입자보다 항상 토양 미생물의 활성 및 다양성에 더 유해한 영향을 나타내는 것은 아니라고 판단된다.

• Bulletin of the Korean Chemical Society
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• 제33권12호
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• pp.4165-4168
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• 2012

Magnetic fluorescent silica nanotubes were fabricated using reverse micro-emulsions coupled with conventional sol-gel methods. Anodic aluminum oxide templates were used to separate spatially the magnetic and the fluorescent moieties on individual nanotubes and so prevent quenching of the fluorescence. C18 and fluorescent layers were deposited sequentially on silica. Magnetism was then obtained by the introduction of pre-made magnetic nanoparticles inside the nanotubes. The photo- and chemical stabilities of nanotubes were demonstrated through dye release and photobleaching tests. The produced nanotubes did not show fluorescence quenching upon the addition of the nanoparticles, an advantage over conventional spherical fluorescent magnetic nanoparticles. High photostability of nanotubes, magnetism and biocompatiblily make them potentially useful in bioanalysis.