• Journal of the Korean Magnetics Society
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• v.22 no.2
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• pp.37-41
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• 2012

The Ag nanoparticles attached $La_{0.7}Sr_{0.3}Co_{0.3}Fe_{0.7}O_{3-{\delta}}$ (LSCF) perovskites were prepared by plasma method. The Ag nanoparticles with size of several nanometers deposited from the Ag target were coated on the surface of LSCF powders with size range from 0.2 to 3 ${\mu}m$. The agglomeration of Ag particles annealed at $800^{\circ}C$ under inert gas of Ar were rarely observed. The inter-diffusion between surface Ag and core LSCF is effectively strong to prevent aggregation of Ag nanoparticles. The wave number of FT-IR spectra for LSCF were largely shifted as the concentration of Ag on LSCF up to 2.11 wt.%. The ionic states of irons in LSCF were measured by M$\ddot{o}$ssbauer spectroscopy. The small amount of $Fe^{4+}$ ions are converted to $Fe^{3+}$ ions after Ag nanopartcles were coated on LSCF.

• Journal of the Korean Applied Science and Technology
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• v.35 no.4
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• pp.1197-1205
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• 2018

UV protection cosmetics belong to functional cosmetics and contain organic or inorganic UV blocking pigments. The inorganic UV blocking pigments are mainly zinc oxide and titanium dioxide. It is known that inorganic UV blocking pigment has a diameter of 60 to 100 nm and has good blocking ability of UVA and UVB. Also, it has high inactivity against sunlight including UV and is excellent in safety. In addition, it is not absorbed or accumulated on the skin like organic pigments and does not cause skin irritation or allergy. In this study, mica, a plate-shaped inorganic pigment, nanosized titanium dioxide, an UV blocking material, and hydrophobic silica were surface-treated with surfactants. And then, titanium dioxide nanoparticles and silica were physically adsorbed on the mica by non-chemical mutual attraction due to differences in charge. Thereafter, the mica complex was surface-treated with silane to prepare a hydrophobic UV blocking pigment complex. The plate-shaped UV blocking composite improves the cohesiveness of a general nanoparticle material titanium dioxide, enhances UV blocking effect due to uniform dispersion, and can greatly improve dispersion stability in cosmetic formulations by surface treatment with hydrophobic property. The surface charge of the pigment was evaluated by zeta potential. The properties of the UV blocking pigment complex were evaluated by FE-SEM, XRD, FT-IR and UV-VIS.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.11
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• pp.634-640
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• 2017

Toxicity and fate assessment is necessary in the evaluation of the environmental, health and safety risks of engineered nanomaaterials (ENMs). Therefore, in order to ensure the reproducibility, reliability and relevance of ENMs toxicity results, stable and monomodal dispersion protocols in toxicity test media are needed. Zinc oxide nanoparticles (nZnO) are widely used in various products such as cosmetic products, paper, paints etc. In this study, nZnO dispersions in ecotoxicity test media were produced by following a series of steps of modified National Institute of Standards and Technology (NIST) Special publication 1200-5. In addition, natural organic matter (humic acid (HA)) was used as a stabilizing agent to disperse nZnO in the test media. The hydrodynamic diameters (HDD) of the nZnO in dispersion ranged between 150 and 200 nm according to the dynamic light scattering (DLS) measurement. Based on these dispersions in ecotoxicity test using ecological species (Oryzias latipes, Daphnia magna, Pseudokirchneriella subcapitata and Chironomusus riparius), dispersion protocol was found to have a considerable potential in ecotoxicity test of ENMs.