• Particle and aerosol research
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• v.12 no.2
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• pp.37-42
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• 2016

$CeO_2$ nanoparticles were prepared by a flame spray pyrolysis from aqueous solution of cerium nitrate. The morphology, structure crystallinity and specific surface area of as-prepared nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and Brunauer-Emmett-Telle (BET). The $CeO_2$ nanoparticles about 5 nm in diameter showed a cubic fluorite structure and polyhedral morphology. The average particle size increased as the cerium nitrate concentration increased. UV absorption performance of the as-prepared nanoparticles was measured by UV-visible spectroscopy. UV absorption of $CeO_2$ nanoparticles was more effective than that of commercial $TiO_2$ nanoparticles. Effect of dopants such as Ti and Zn to $CeO_2$ nanoparticles on UV absorption properties was also investigated. In case of $Ti/CeO_2$, and $Zn/CeO_2$ nanoparticles, they showed a little higher UV absorption values compared with $CeO_2$ nanoparticles. The as-prepared nanoparticles can be promising materials with high UV absorption value.

• Korean Journal of Materials Research
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• v.15 no.2
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• pp.112-114
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• 2005

Dispersion stability of the $Sm_xCe_{1-x}O_{2-2/x}$ nanoparticles, which was produced by hydrothermal process, was studied in aqueous suspension using ESA (Eletrokinetic Sonic Amplitude). The average particle size of the synthesized $Sm_xCe_{1-x}O_{2-2/x}$ at nanoparticles was about $5{\pm}2nm$. The dispersion and rheological behavior of the $Sm_xCe_{1-x}O_{2-2/x}$ nanoparticles aqueous suspension was investigated using $NH_4OH\;and\;HNO_3$ as a disperse agent. The colloidal stability of aqueous suspensions with $Sm_xCe_{1-x}O_{2-2/x}$ nanoparticles at different pH values has been investigated by means of zeta potential, average particle size, and the distribution of synthesized $Sm_xCe_{1-x}O_{2-2/x}$ nanoparticles. The isoelectric point of the $Sm_xCe_{1-x}O_{2-2/x}$ nanoparticles was at pH around 11 and the value of zeta potential was at its maximum near pH 6.5.

• Environmental Analysis Health and Toxicology
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• v.23 no.2
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• pp.87-91
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• 2008

In this study, three different sizes of cerium oxide ($CeO_2$) nanoparticles were synthesized and exposed to Caenorhabditis elegans to investigate the potential harmful effect of $CeO_2$ nanoparticles on the environment. The effects of the $CeO_2$ nanoparticles on C. elegans were assessed at multiple levels, such as with respect to stress response gene expression, growth, reproduction and mortality. Moreover, to test the ecotoxicological relevance of $CeO_2$-induced gene expression. The overall results suggest that $CeO_2$ nanoparticles may provoke ecotoxicity in C. elegans especially with respect to gene expression, reproduction and survival, which can comprise an important contribution to knowledge on the ecotoxicity of $CeO_2$ nanoparticles, about which little data are available. This is particularly valuable in the biomarker research on ecotoxicology, as ecological relevance is a crucial criterion for the applicability of the biomarker in field biomonitoring and ecological risk assessment.

• Korean Journal of Materials Research
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• v.30 no.7
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• pp.376-382
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• 2020

CeO₂ nanoparticles, employed in a lot of fields due to their excellent oxidation and reduction properties, are synthesized through a solvothermal process, and a high specific surface area is shown by controlling, among various process parameters in the solvothermal process, the type of solvent. The synthesized CeO₂ nanoparticles are about 11~13 nm in the crystallite size and their specific surface area is about 65.38~84.65 ㎡/g, depending on the amount of ethanol contained in the solvent for the solvothermal process; all synthesized CeO₂ nanoparticles shows a fluorite structure. The dispersibility and microstructure of the synthesized CeO₂ nanoparticles are investigated according to the species of dispersant and the pH value of the solution; an improvement in dispersibility is shown with the addition of dispersants and control of the pH. Various dispersing properties appear according to the dispersant species and pH in the solution with the synthesized CeO₂ nanoparticles, indicating that improved dispersing properties in the synthesized CeO₂ nanoparticles can be secured by applying dispersant and pH control simultaneously.

• Advances in materials Research
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• v.3 no.2
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• pp.105-116
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• 2014

The microwave dielectric properties of $CeO_2$ nanoparticles (0.5, 1.0 & 1.5wt%) doped $Mg_2TiO_4$ (MTO) ceramics have been investigated at cryogenic temperatures. The XRD patterns of the samples were refined using the full proof program reveal the inverse spinel structure without any secondary phases. The addition of $CeO_2$ nanoparticles lowered the sintering temperature with enhancement in density and grain size as compared to pure MTO ceramics. This is attributed to the higher sintering velocity of the fine particles. Further, the microwave dielectric properties of the MTO ceramics were measured at cryogenic temperatures in the temperature range of 6.5-295 K. It is observed that the loss tangent ($tan{\delta}$) of all the samples increased with temperature. However, the $CeO_2$ nanoparticles doped MTO ceramics manifested lower loss tangents as compared to the pure MTO ceramics. The loss tangents of the pure and MTO ceramics doped with 1.5 wt% of $CeO_2$ nanoparticles measured at 6.5K are found to be $6.6{\times}10^{-5}$ and $5.4{\times}10^{-5}$, respectively. The addition of $CeO_2$ nanoparticles did not cause any changes on the temperature stability of the MTO ceramics at cryogenic temperatures. On the other hand, the temperature coefficient of the permittivity increased with rise in temperature and with the wt% of $CeO_2$ nanoparticles. The obtained lower loss tangent values at cryogenic temperatures can be attributed to the decrease in both intrinsic and extrinsic losses in the MTO ceramics.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.339-339
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• 2010

The metallic nanoparticles (Pt, Au, Ag. Cu, etc.) supported on ceria-titania mixed oxide exhibit a high catalytic activity for the water gas shift reaction ($H_2O\;+\;CO\;{\leftrightarrow}\;H_2\;+\;CO_2$) and the CO oxidation ($O_2\;+\;2CO\;{\leftrightarrow}\;2CO_2$). It has been speculated that the high catalytic activity is related to the easy exchange of the oxidation states of ceria ($Ce^{3+}$ and $Ce^{4+}$) on titania, but very little is known about the ceria titanium interaction, the growth mode of metal on ceria titania complex, and the reaction mechanism. In this work, the growth of $CeO_x$ and Au/$CeO_x$ on rutile $TiO_2$(110) have been investigated by Scanning Tunneling Microscopy (STM), Photoelectron Spectroscopy (PES), and DFT calculation. In the $CeO_x/TiO_2$(110) systems, the titania substrate imposes on the ceria nanoparticles non-typical coordination modes, favoring a $Ce^{3+}$ oxidation state and enhancing their chemical activity. The deposition of metal on a $CeO_x/TiO_2$(110) substrate generates much smaller nanoparticles with an extremely high activity. We proposed a mechanism that there is a strong coupling of the chemical properties of the admetal and the mixed-metal oxide: The adsorption and dissociation of water probably take place on the oxide, CO adsorbs on the admetal nanoparticles, and all subsequent reaction steps occur at the oxide-admetal interface.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.3
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• pp.118-122
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• 2018

Ceria ($CeO_2$) is a rare earth oxide, which has been widely investigated to improve the property. It is important to increase the surface area of $CeO_2$, because high surface area of $CeO_2$ can improve the catalytic ability. $CeO_2$ nanoparticles were synthesized by a solvothermal process. A discussion on the influence of solvent ratio and precursors on $CeO_2$ nanoparticles was performed. The size and degree of the agglomeration of the synthesized $CeO_2$ could be tuned by controlling those parameters. The average size and distribution of prepared $CeO_2$ powders was in the range of 3 to 13 nm and narrow, respectively. The XRD pattern showed that the synthesized $CeO_2$ powders were crystalline with cubic phase of $CeO_2$. The average particle size was calculated by Scherrer equation and FE-TEM images. The morphology of the synthesized $CeO_2$ particle was objected using FE-TEM and FE-SEM. Specific surface area of the synthesized $CeO_2$ was determined using BET (Brunauer-Emmett-Teller) equation.

• Journal of the Korean Applied Science and Technology
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• v.34 no.4
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• pp.746-755
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• 2017

In this study, $CeO_2/TiO_2$ nanoparticle with structure of core and shell was synthesized by growing $TiO_2$ onto the surface of $CeO_2$ according to hydrolysis of $Ti(SO_4)_2$. Reaction time, temperature, concentration of $CeO_2$ slurry, pH control of $Ti(SO_4)_2$ were optimized about synthesis of $CeO_2/TiO_2$ core-shell nanoparticle. It was found that optimal mole ratio range of $CeO_2:TiO_2$ was 1:0.2~1.1, the optimal concentration of $CeO_2$ slurry was 1 %, and the optimal reaction temperature was $50^{\circ}C$. The optimal concentration of $CeO_2$ slurry could be increased up to 10 % by adjusting the pH of $Ti(SO_4)_2$ to 1 using $NH_4OH$ and adding to $CeO_2$ slurry. If reaction was carried at $80^{\circ}C$ or higher, the separated $TiO_2$ particles were obtained instead of $CeO_2/TiO_2$ core-shell nanoparticles. The optimal reaction temperature was $50^{\circ}C$ at which good shaped core-shell structure of $CeO_2/TiO_2$ was obtained.

• Journal of Sensor Science and Technology
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• v.33 no.5
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• pp.288-297
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• 2024

Currently, numerous studies are being conducted on metal oxide semiconductor (MOS) gas sensors for hydrogen detection, using Palladium (Pd) and Pd-based alloy nanoparticles (NPs) owing to their hydrogen absorption ability. Furthermore, several studies have reported that Pd-Iridium (Ir) alloys possess high hydrogen absorption capabilities in their bulk state. However, Ir growth is limited to above 2 nm and it does not mix extensively with other metals. Furthermore, as the hydrogen absorption capacity decreases with the reduction in particle size, it is necessary to synthesize nanoparticles of an appropriate size. Therefore, the synthesis of Pd-Ir alloy NPs larger than 10 nm is challenging. In this study, we report the synthesis of Pd-Ir NPs with an average diameter of 19 nm using a hydrothermal technique for the first time and fabricated Pd-Ir alloy NPs through calcination at 500℃ in Ar and air. To confirm alloy formation and oxidation behavior, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were performed. In addition, we synthesized Pd-Ir@CeO₂ core-shell nanoparticles (CSNPs) as hydrogen gas-sensing materials. The Pd-Ir core was partially oxidized during heat treatment at 500℃ in air, and Pd-Ir@CeO₂ CSNPs were finally changed into Pd-Ir(alloy)/PdO-IrO₂@CeO₂ CSNPs, which exhibited higher sensitivity and selectivity toward H₂ gas compared to totally oxidized PdO-IrO₂@CeO₂ CSNPs and pure CeO₂ NPs. The enhanced gas-sensing performance was attributed to the hydrogen absorption effect of the Pd-Ir(alloy) NPs.

• Journal of Preventive Medicine and Public Health
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• v.48 no.3
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• pp.132-141
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• 2015

Objectives: With recent advances in nanoparticle manufacturing and applications, potential exposure to nanoparticles in various settings is becoming increasing likely. No investigation has yet been performed to assess whether respiratory tract exposure to cerium oxide ($CeO_2$) nanoparticles is associated with alterations in protein signaling, inflammation, and apoptosis in rat lungs. Methods: Specific-pathogen-free male Sprague-Dawley rats were instilled with either vehicle (saline) or $CeO_2$ nanoparticles at a dosage of 7.0 mg/kg and euthanized 1, 3, 14, 28, 56, or 90 days after exposure. Lung tissues were collected and evaluated for the expression of proteins associated with inflammation and cellular apoptosis. Results: No change in lung weight was detected over the course of the study; however, cerium accumulation in the lungs, gross histological changes, an increased Bax to Bcl-2 ratio, elevated cleaved caspase-3 protein levels, increased phosphorylation of p38 MAPK, and diminished phosphorylation of ERK-1/2-MAPK were detected after $CeO_2$ instillation (p<0.05). Conclusions: Taken together, these data suggest that high-dose respiratory exposure to $CeO_2$ nanoparticles is associated with lung inflammation, the activation of signaling protein kinases, and cellular apoptosis, which may be indicative of a long-term localized inflammatory response.