• Korean Journal of Environmental Biology
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• v.39 no.4
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• pp.550-558
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• 2021

In a radiotracer study, the bioaccumulation and efflux of metals in earthworms (Eisenia fetida) exposed to soil spiked with ZnO and Ag nanoparticles (AgNP) were compared to those exposed to soil spiked with ionic Zn and Ag. Additionally, the bioavailability and chemical mobility of nano- and ionic metals in the soil were estimated using the sequential extraction method and compared to the bioaccumulation factor(BAF). The BAF for ZnO (0.06) was 31 times lower than that for Zn ions (1.86), suggesting that ZnO was less bioavailable than the ionic form in contaminated soil. In contrast, the BAFs for two types of AgNPs coated with polyvinylpyrrolidone (0.12) or citrate (0.11) were comparable to those of ionic Ag (0.17). The sequential extraction of metals from the soil suggests that the chemically mobile fractions in the Zn ion treatment were higher(35%) than those (<20%) in the Ag ion treatment, which was consistent with the greater BAFs in the former than the latter. However, the chemical mobility in the ZnO treatments did not predict bioavailability. The efflux rates of Ag (3.2-3.8% d^-1) in the worms were 2-3×those(1.2-1.7% d^-1) for Zn.

• Journal of Powder Materials
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• v.28 no.2
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• pp.143-149
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• 2021

In this study, (GaN)_1-x(ZnO)_x solid solution nanoparticles with a high zinc content are prepared by ultrasonic spray pyrolysis and subsequent nitridation. The structure and morphology of the samples are investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The characterization results show a phase transition from the Zn and Ga-based oxides (ZnO or ZnGa₂O₄) to a (GaN)_1-x(ZnO)_x solid solution under an NH3 atmosphere. The effect of the precursor solution concentration and nitridation temperature on the final products are systematically investigated to obtain (GaN)_1-x(ZnO)_x nanoparticles with a high Zn concentration. It is confirmed that the powder synthesized from the solution in which the ratio of Zn and Ga was set to 0.8:0.2, as the initial precursor composition was composed of about 0.8-mole fraction of Zn, similar to the initially set one, through nitriding treatment at 700℃. Besides, the synthesized nanoparticles exhibited the typical XRD pattern of (GaN)_1-x(ZnO)_x, and a strong absorption of visible light with a bandgap energy of approximately 2.78 eV, confirming their potential use as a hydrogen production photocatalyst.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.25 no.3
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• pp.69-77
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• 2019

Agar-based nanocomposite films were prepared by incorporation of zinc oxide nanoparticles (ZnONP) and grapefruit seed extract (GSE). The composite films were characterized using FT-IR, UV-visible spectroscopy and thermalgravimetric analysis (TGA). The composite films showed light absorption peaks at 220 and 380 nm, characteristic for GSE and ZnONP, respectively. The UV-light transmittance of the agar film was markedly reduced from 54.4 ± 1.3% to 5.8 ± 2.5% with little sacrifice of transparency when 3 wt% ZnONP and 5 wt% GSE were added. The mechanical and water vapor barrier properties increased slightly though they were not significant statistically by the addition of ZnONP and GSE. The nanocomposite films showed stronger antibacterial activity against L. monocytogenes than E. coli O157: H7 and the antibacterial activity was affected by bacterial types as well as concentrations of ZnONP and GSE. The nano-composite film incorporated with 3 wt% of ZnONP and 5 wt% of GSE exhibited strong antibacterial activity against Listeria monocytogenes and E. coli O157: H7. The results indicate that 3 wt% of ZnONP and 5 wt% of GSE are the optimal concentrations for producing functional agar/ZnONP/GSE composite films.

• Journal of the Korean Chemical Society
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• v.59 no.5
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• pp.397-406
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• 2015

ZnO, II-VI group inorganic compound semi-conductor, has been receiving much attention due to its wide applications in various fields. Since the ZnO has 3.37 eV of a wide band gap and 60 meV of big excitation binding energy, it is well-known material for various uses such the optical property, a semi-conductor, magnetism, antibiosis, photocatalyst, etc. When applied in the field of photocatalyst, many research studies have been actively conducted regarding magnetic materials and the core-shell structure to take on the need of recycling used materials. In this paper, magnetic core-shell ZnFe₂O₄@SiO₂ nanoparticles (NPs) have been successfully synthesized through three steps. In order to analyze the structural characteristics of the synthesized substances, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR) were used. The spinel structure of ZnFe₂O₄ and the wurtzite structure of ZnO were confirmed by XRD, and ZnO production rate was confirmed through the analysis of different concentrations of the precursors. The surface change of the synthesized materials was confirmed by SEM. The formation of SiO₂ layer and the synthesis of ZnFe₂O₄@ZnO@SiO₂ NPs were finally verified through the bond of Fe-O, Zn-O and Si-O-Si by FT-IR. The magnetic property of the synthesized materials was analyzed through the vibrating sample magnetometer (VSM). The increase and decrease in the magnetism were respectively confirmed by the results of the formed ZnO and SiO₂ layer. The photocatalysis effect of the synthesized ZnFe₂O₄ @ZnO@SiO₂ NPs was experimented in a black box (dark room) using methylene blue (MB) under UV irradiation.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.386-386
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• 2011

sol-gel 및 hydrothermal growth method를 이용한 zinc oxide nanorod는 제작 시 고가의 장비가 필요치 않기에 저비용 대면적 박막을 제작하는데 적합하지만 rod들의 array 및 density 조절에서 어려움을 가지고 있다. 본 연구에서는 이러한 nanorod array 형상 조절을 위하여 zinc oxide seed layer 형성 과정 중 precursor solution에 이종 나노 입자를 첨가하였다. 첨가한 seed precursor solution을 spin coating한 이후에 후처리 하여 hydrothermal method를 이용해 성장시켰다. 합성한 rod들을 optic과 FE-SEM으로 측정해 rod들의 density 변화를 확인할 수 있었다.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.222-224
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• 2006

A non-vacuum process for $Cu(In,Ga)Se_2$ (CIGS) thin film solar cells from nanoparticle precursors was described in this work CIGS nanoparticle precursors was prepared by a low temperature colloidal route by reacting the starting materials $(CuI,\;InI_3,\;GaI_3\;and\;Na_2Se)$ in organic solvents, by which fine CIGS nanoparticles of about 20nm in diameter were obtained. The nanoparticle precursors were mixed with organic binder material for the rheology of the mixture to be adjusted for the doctor blade method. After depositing the mixture of CIGS with binder on Mo/glass substrate, the samples were preheated on the hot plate in air to evaporate remaining solvents ud to burn the organic binder material. Subsequently, the resultant (porous) CIGS/Mo/glass simple was selenized in a two-zone Rapid Thermal Process (RTP) furnace in order to get a solar ceil applicable dense CIGS absorber layer. Complete solar cell structure was obtained by depositing. The other layers including CdS buffer layer, ZnO window layer and Al electrodes by conventional methods. The resultant solar cell showed a conversion efficiency of 0.5%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.9 s.240
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• pp.1065-1073
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• 2005

The thermal conductivity of water- and ethylene glycol-based nanofluids containing alumina $(Al_2O_3)$, zinc oxide (ZnO) and titanium dioxide $(TiO_2)$ nanoparticles is measured by varying the particle diameter and volume fraction. The transient hot-wire method using an anodized tantalum wire for electrical insulation is employed for the measurement. The experimental results show that nanofluids have substantially higher thermal conductivities than those of the base fluid and the ratio of thermal conductivity enhancement increases linearly with the volume fraction. It has been found that the ratio of thermal conductivity enhancement increases with decreasing particle size but no empirical or theoretical correlation can explain the particle-size dependence of the thermal conductivity. This work provides, for the first time to our knowledge, a set of consistent experimental data over a wide range of nanofluid conditions and can therefore serve as a basis for developing theoretical models to predict thermal conduction phenomena in nanofluids.

• Journal of the Korean Ceramic Society
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• v.41 no.10 s.269
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• pp.742-748
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• 2004

Isopropanol of low boiling point was used as a solvent to prepare Al-doped ZnO(AZO) thin films. A homogeneous and stable sol was made from Zn acetate a solute whose mole concentration was 0.7mol/$\iota$ and Al chloride as a dopant. Al-doped ZnO thin films were prepared by sol-gel method as a function of post-heating temperature from 500 to $700^{\circ}C$ and the optical and electrical properties were investigated. The c-axis orientation along (002) plane was enhanced with the increasing of post-heating temperature and the surface morphology of the films showed a homogeneous and nano-sized microstructure. The optical transmittance of the films post-heated below $650^{\circ}C$ was over $86\%$, but decreased at $700^{\circ}C$. The electrical resistivity of the thin films decreased from 73 to 22 $\Omega$-cm as the post-heating temperature increased up to $650^{\circ}C$, but increased greatly to 580 $\Omega$-cm at $700^{\circ}C$. XPS analysis indicated that the deterioration of electrical and optical properties was attributed to the precipitation of $Al_2O_3$ phase on the surface of AZO thin film. This result suggests that the optimum post-heating temperature to improve electrical and optical properties is $600^{\circ}C$.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.23-23
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• 2009

CIGS 박막 태양전지는 제조단가가 낮고 박막 태양전지 중에서 변환효율이 가장 높아 발전 가능성이 큰 태양전지로 인식되고 있다. 이미 일본, 독일, 미국을 비롯한 선진국에서는 30-50 MW 급의 양산 라인이 구축되고 있어 2010년 이후에는 본격적인 상용화가 진행될 것으로 보인다. CIGS 광흡수층은 진공증발, 셀렌화, 나노입자, 전기도금등 다양한 방식으로 제조가 가능한데 이 중에서도 동시진공증발공정은 고효율 CIGS 박막 태양전지 제조에 적합하다. 본 연구에서는 동시진공증발법을 이용하여 CIGS 박막을 증착하였으며 소다회유리/Mo/CIGS/CdS/i-ZnO/n-ZnO/Al/AR 구조의 태양전지를 제조하였다. 기판온도 모니터링을 통한 Cu 이차상 조절 기술을 이용하여 결정립이 매우 큰 CIGS 박막을 증착하였으며 Ga/(In+Ga) 조성비의 조절을 통하여 밴드갭 에너지를 최적화하였다. 또한 QCM 장치를 활용하여 용액 속에서 성장되는 CdS 박막의 두께와 특성을 조절하였다. 이러한 공정최적화를 통하여 개방전압 0.65 V, 단락전류밀도 38.8 $mA/cm^2$, 충실도 0.74 그리고 변환효율 18.8% 의 CIGS 박막 태양전지를 얻었다.

• Journal of the Korean Magnetics Society
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• v.18 no.3
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• pp.120-125
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• 2008

In this study, NiCoZn ferrites with the variation of sintering temperature and chemical composition were prepared by the coprecipitation. Microstructures Crystal structure of NiCoZn ferrites were analyzed by XRD and their electric magnetic characteristics were analyzed by LCR meter and their morphology observed by SEM. We identified that these powders have a typical NiCoZn spinel structure and nanoparticles average size of 40 nm. The impurity, the initial permeability and the Q factor value are the lowest of sintered NiCoZn ferrite at $1250^{\circ}C$. Also, we measured S-parameter for $(Ni_{0.4}Co_{0.1}Zn_{0.5})Fe_2O_4$ which showed a maximum reflection loss of -3.1 dB at 6 GHz for the 2 mm thick sample. From this result, we found that the NiCoZn ferrite can be used in ferrite microwave-absorbing application at a higher frequency region (> 6 GHz).