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Sample records for cerium oxides

  1. Cerium Oxide and Cerium Compounds

    Integrated Risk Information System (IRIS)

    EPA / 635 / R - 08 / 002F www.epa.gov / iris TOXICOLOGICAL REVIEW OF Cerium Oxide and Cerium Compounds ( CAS No . 1306 - 38 - 3 ) In Support of Summary Information on the Integrated Risk Information System ( IRIS ) September 2009 U.S . Environmental Protection Agency Washington , DC ii DISCLAIMER Th

  2. IRIS Toxicological Review of Cerium Oxide and Cerium ...

    EPA Pesticide Factsheets

    EPA conducted a peer review of the scientific basis supporting the human health hazard and dose-response assessment of cerium oxide and cerium compounds that will appear on the Integrated Risk Information System (IRIS) database. The draft Toxicological Review of cerium oxide and cerium compounds provides scientific support and rationale for the hazard and dose-response assessment pertaining to chronic exposure to cerium oxide and cerium compounds.

  3. IRIS Toxicological Review of Cerium Oxide and Cerium ...

    EPA Pesticide Factsheets

    On September 29, 2009, the IRIS Summary and Toxicological Review of Cerium Oxide and Cerium Compounds was finalized and loaded onto the IRIS database. The Toxicological Review of Cerium Oxide and Cerium Compounds was reviewed internally by EPA, by other federal agencies and White House Offices, by expert external peer reviewers, and by the public. In the new IRIS process, introduced by the EPA Administrator, all written comments on IRIS assessments submitted by other federal agencies and White House Offices will be made publicly available. Accordingly, interagency comments and the interagency draft of the Cerium Oxide and Cerium Compounds IRIS assessment are posted on this site. The draft Toxicological Review of Cerium Oxide and Cerium Compounds provides scientific support and rationale for the hazard identification and dose-response assessment pertaining to chronic exposure to cerium oxide and cerium compounds.

  4. Nanoparticle cerium oxide and mixed cerium oxides for improved fuel cell lifetime

    NASA Astrophysics Data System (ADS)

    Stewart, Stephen Michael

    While there is a rich body of literature concerning of properties of bulk cerium oxide and cerium cations in solution, the discussion has been inappropriately applied to nanoscale cerium oxide resulting in many unexpected or unexplained results. In particular, there is very limited understanding about the properties of cerium oxide and its potential use as a radical scavenger, and how the catalytic properties of cerium oxide change as the particle size approaches the nanoscale. For example, the involvement of Ce+4 and Ce+3 cations in reactions such as hydrogen peroxide decomposition have been investigated for both cerium cations and bulk cerium oxide. However, while both are assumed to decompose hydrogen peroxide through the same mechanism, whereby Ce+4 is involved in peroxide decomposition while Ce +3 is involved in radical scavenging, there has been very little done to address how the selectivity and activity of these reactions are affected by changing the majority cation population, as cerium cations in solution are predominantly in the +3 oxidation state while cerium cations are predominantly in the +4 oxidation state in cerium oxide. This matter is further complicated in cerium oxide nanoparticles where the surface concentration of Ce +3 cations is increased due to particle curvature effects. Due to the potential of controlling the surface cerium oxidation state using particle size and using this control to change the catalytic properties, this project investigated the effect of particle size and composition and the activity and selectivity of cerium oxide nanoparticles, and has served to expand the understanding of the properties of pure and mixed nanoparticle cerium oxide. This work explains the metric developed for measuring the catalytic properties of pure and mixed cerium oxide nanoparticles, which is also good at predicting the immediate and long-term behavior of nanoparticles in hydrogen fuel cells. This work also directly demonstrates praseodymium

  5. Cerium oxide for sunscreen cosmetics

    NASA Astrophysics Data System (ADS)

    Yabe, Shinryo; Sato, Tsugio

    2003-02-01

    Ultrafine particles of Mn+ -doped ceria ( Mn+ =Mg 2+, Ca 2+, Sr 2+, Ba 2+, Y 3+, La 3+, Nd 3+, Sm 3+, Eu 3+, Tb 3+) for UV filter were prepared via soft solution chemical routes at 40°C. X-ray diffraction revealed that the prepared doped particles had the cubic fluorite structures although peak positions changed depending on the kind and amount of doped metal ion. Doping with 20 mol% Ca 2+ and 20 mol% Zn 2+ resulted in extremely decreasing the particle size (2-4 nm) and the catalytic activity of ceria for oxidation of castor oil. Ca 2+-doped cerium dioxide showed excellent UV absorbing effect and transparency in the visible ray region compared with undoped cerium dioxide.

  6. Formulation and method for preparing gels comprising hydrous cerium oxide

    SciTech Connect

    Collins, Jack L; Chi, Anthony

    2013-05-07

    Formulations useful for preparing hydrous cerium oxide gels contain a metal salt including cerium, an organic base, and a complexing agent. Methods for preparing gels containing hydrous cerium oxide include heating a formulation to a temperature sufficient to induce gel formation, where the formulation contains a metal salt including cerium, an organic base, and a complexing agent.

  7. IRIS Toxicological Review of Cerium Oxide and Cerium Compounds (External Review Draft)

    EPA Science Inventory

    EPA conducted a peer review of the scientific basis supporting the human health hazard and dose-response assessment of cerium oxide and cerium compounds that will appear on the Integrated Risk Information System (IRIS) database.

  8. Nanocrystalline cerium oxide materials for solid fuel cell systems

    DOEpatents

    Brinkman, Kyle S

    2015-05-05

    Disclosed are solid fuel cells, including solid oxide fuel cells and PEM fuel cells that include nanocrystalline cerium oxide materials as a component of the fuel cells. A solid oxide fuel cell can include nanocrystalline cerium oxide as a cathode component and microcrystalline cerium oxide as an electrolyte component, which can prevent mechanical failure and interdiffusion common in other fuel cells. A solid oxide fuel cell can also include nanocrystalline cerium oxide in the anode. A PEM fuel cell can include cerium oxide as a catalyst support in the cathode and optionally also in the anode.

  9. Cerium and yttrium oxide nanoparticles are neuroprotective.

    PubMed

    Schubert, David; Dargusch, Richard; Raitano, Joan; Chan, Siu-Wai

    2006-03-31

    The responses of cells exposed to nanoparticles have been studied with regard to toxicity, but very little attention has been paid to the possibility that some types of particles can protect cells from various forms of lethal stress. It is shown here that nanoparticles composed of cerium oxide or yttrium oxide protect nerve cells from oxidative stress and that the neuroprotection is independent of particle size. The ceria and yttria nanoparticles act as direct antioxidants to limit the amount of reactive oxygen species required to kill the cells. It follows that this group of nanoparticles could be used to modulate oxidative stress in biological systems.

  10. Photodissociation of Cerium Oxide Nanocluster Cations.

    PubMed

    Akin, S T; Ard, S G; Dye, B E; Schaefer, H F; Duncan, M A

    2016-04-21

    Cerium oxide cluster cations, CexOy(+), are produced via laser vaporization in a pulsed nozzle source and detected with time-of-flight mass spectrometry. The mass spectrum displays a strongly preferred oxide stoichiometry for each cluster with a specific number of metal atoms x, with x ≤ y. Specifically, the most prominent clusters correspond to the formula CeO(CeO2)n(+). The cluster cations are mass selected and photodissociated with a Nd:YAG laser at either 532 or 355 nm. The prominent clusters dissociate to produce smaller species also having a similar CeO(CeO2)n(+) formula, always with apparent leaving groups of (CeO2). The production of CeO(CeO2)n(+) from the dissociation of many cluster sizes establishes the relative stability of these clusters. Furthermore, the consistent loss of neutral CeO2 shows that the smallest neutral clusters adopt the same oxidation state (IV) as the most common form of bulk cerium oxide. Clusters with higher oxygen content than the CeO(CeO2)n(+) masses are present with much lower abundance. These species dissociate by the loss of O2, leaving surviving clusters with the CeO(CeO2)n(+) formula. Density functional theory calculations on these clusters suggest structures composed of stable CeO(CeO2)n(+) cores with excess oxygen bound to the surface as a superoxide unit (O2(-)).

  11. The formation of light emitting cerium silicates in cerium-doped silicon oxides

    SciTech Connect

    Li Jing; Zalloum, Othman; Roschuk, Tyler; Heng Chenglin; Wojcik, Jacek; Mascher, Peter

    2009-01-05

    Cerium-doped silicon oxides with cerium concentrations of up to 0.9 at. % were deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition. Bright cerium related photoluminescence, easily seen even under room lighting conditions, was observed from the films and found to be sensitive to film composition and annealing temperature. The film containing 0.9 at. % Ce subjected to anneal in N{sub 2} at 1200 deg. C for 3 h showed the most intense cerium-related emission, easily visible under bright room lighting conditions. This is attributed to the formation of cerium silicate [Ce{sub 2}Si{sub 2}O{sub 7} or Ce{sub 4.667} (SiO{sub 4}){sub 3}O], the presence of which was confirmed by high resolution transmission electron microscopy.

  12. The surface chemistry of cerium oxide

    SciTech Connect

    Mullins, David R.

    2015-01-29

    Our review covers the structure of, and chemical reactions on, well-defined cerium oxide surfaces. Ceria, or mixed oxides containing ceria, are critical components in automotive three-way catalysts due to their well-known oxygen storage capacity. Ceria is also emerging as an important material in a number of other catalytic processes, particularly those involving organic oxygenates and the water–gas shift reaction. Ceria's acid–base properties, and thus its catalytic behavior, are closely related to its surface structure where different oxygen anion and cerium cation environments are present on the low-index structural faces. The actual structure of these various faces has been the focus of a number of theoretical and experimental investigations. Ceria is also easily reducible from CeO2 to CeO2-X. The presence of oxygen vacancies on the surface often dramatically alters the adsorption and subsequent reactions of various adsorbates, either on a clean surface or on metal particles supported on the surface. We conducted surface science studies on the surfaces of thin-films rather than on the surfaces of bulk single crystal oxides. The growth, characterization and properties of these thin-films are also examined.

  13. The surface chemistry of cerium oxide

    DOE PAGES

    Mullins, David R.

    2015-01-29

    Our review covers the structure of, and chemical reactions on, well-defined cerium oxide surfaces. Ceria, or mixed oxides containing ceria, are critical components in automotive three-way catalysts due to their well-known oxygen storage capacity. Ceria is also emerging as an important material in a number of other catalytic processes, particularly those involving organic oxygenates and the water–gas shift reaction. Ceria's acid–base properties, and thus its catalytic behavior, are closely related to its surface structure where different oxygen anion and cerium cation environments are present on the low-index structural faces. The actual structure of these various faces has been the focusmore » of a number of theoretical and experimental investigations. Ceria is also easily reducible from CeO2 to CeO2-X. The presence of oxygen vacancies on the surface often dramatically alters the adsorption and subsequent reactions of various adsorbates, either on a clean surface or on metal particles supported on the surface. We conducted surface science studies on the surfaces of thin-films rather than on the surfaces of bulk single crystal oxides. The growth, characterization and properties of these thin-films are also examined.« less

  14. The surface chemistry of cerium oxide

    NASA Astrophysics Data System (ADS)

    Mullins, David R.

    2015-03-01

    This review covers the structure of, and chemical reactions on, well-defined cerium oxide surfaces. Ceria, or mixed oxides containing ceria, are critical components in automotive three-way catalysts due to their well-known oxygen storage capacity. Ceria is also emerging as an important material in a number of other catalytic processes, particularly those involving organic oxygenates and the water-gas shift reaction. Ceria's acid-base properties, and thus its catalytic behavior, are closely related to its surface structure where different oxygen anion and cerium cation environments are present on the low-index structural faces. The actual structure of these various faces has been the focus of a number of theoretical and experimental investigations. Ceria is also easily reducible from CeO2 to CeO2-X. The presence of oxygen vacancies on the surface often dramatically alters the adsorption and subsequent reactions of various adsorbates, either on a clean surface or on metal particles supported on the surface. Most surface science studies have been conducted on the surfaces of thin-films rather than on the surfaces of bulk single crystal oxides. The growth, characterization and properties of these thin-films are also examined.

  15. Liquid-phase oxidation of cyclohexanone over cerium oxide catalyst

    SciTech Connect

    Shen, H.C. ); Weng, H.S. )

    1990-05-01

    Catalytic oxidation of cyclohexanone in the liquid phase with glacial acetic acid as the solvent over cerium oxide was studied between 5 and 15 atm and 98 and 118 {degrees} C in a batch reactor. The products were adipic acid, glutaric acid, succinic acid, caprolactone, carbon oxides, etc. The reaction undergoes a short induction period prior to a rapid reaction regime. In both regimes, the reaction is independent of oxygen pressure when the system pressure is above 10 atm. The induction period is inversely proportional to both of the catalyst weight and cyclohexanone concentration.During the rapid reaction regime, the reaction rate was found to be proportional to the 0.5 power of the catalyst weight and to the 1.5 power of the cyclohexanone concentration. Reaction mechanisms and rate expressions are proposed. The carbon oxides produced in this study were much lower than those previously reported. The cerium oxide catalyst is stable during the reaction.

  16. Selective cytotoxicity effect of cerium oxide nanoparticles under UV irradiation.

    PubMed

    Zhang, Li; Jiang, Hui; Selke, Matthias; Wang, Xuemei

    2014-02-01

    During photodynamic therapy (PDT) of cancers, there are numerous side effects, accompanied by damage to normal cells/tissues caused by the abnormal elevation of reactive oxygen species (ROS). In this paper, we aim to provide an effective method to reduce the relevant side effects of PDT by using cerium oxide nanoparticles. The well-dispersed poly(vinyl pyrrolidone) stabilized cerium oxide nanoparticles were successfully synthesized by using a one-pot method at 60 degrees C in slightly alkaline environment. The morphological and structural characterizations clearly illustrate the excellent lattice structures of cerium oxide, nanoparticles. The MTT assay indicates that these cerium oxide nanoparticles show no intrinsic cytotoxicity even at a concentration up to 300 micro g/mL. More importantly, the results demonstrate that these nanoparticles can selectively protect human normal cells but not the cancer cells from ROS damage after exposure to UV-radiation, suggesting their potential applications for PDT treatment. The rationale behind the selective protection effect can be attributed to the hindrance of the Ce (III)/Ce (IV) redox reaction cycle on the surface of cerium oxide nanoparticles due to the abnormal intracellular pH in cancer cells. Furthermore, these cerium oxide nanoparticles can be used as effective drug carriers for enhancing drug delivery efficiency to target cancer cells like hepatoma HepG2 cells. This raises the possibility of applying cerium oxide nanoparticles for multifunctional therapeutic applications, i.e., combination of efficient PDT and chemotherapy.

  17. An efficient method for dephosphorylation of phosphopeptides by cerium oxide.

    PubMed

    Tan, Feng; Zhang, Yangjun; Wang, Jinglan; Wei, Junying; Cai, Yun; Qian, Xiaohong

    2008-05-01

    In this article, an effective method for dephosphorylation of phosphopeptides by cerium oxide is described. The dephosphorylation activity of cerium oxide was evaluated by two standard phosphopeptides and the phosphopeptides in digests of phosphoprotein alpha-casein and beta-casein. Results showed that the dephosphorylation of all the phosphopeptides was completed in 10 min, and temperature had little effect on the dephosphorylation, the dephosphorylation could be carried out at 0 degrees C, room temperature and 37 degrees C. The dephosphorylation mediated by cerium oxide can be attributed to Lewis acid and nucleophile activations. Advantages of using cerium oxide as catalyst for the dephosphorylation include: safe, simple, high catalytic activity, and no precise control of the treatment temperature. The method is valid for the phosphorylation of Ser, Thr and Tyr, and can be used for phosphoprotein analysis.

  18. Heteroaggregation of cerium oxide nanoparticles and nanoparticles of pyrolyzed biomass

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Heteroaggregation with indigenous particles is an important process controlling the mobility of engineered nanomaterials in the environment. We studied heteroaggregation of cerium oxide nanoparticles (n-CeO2), which are widely used commercially, with nanoparticles of pyrogenic carbonaceous material ...

  19. Characterization of cerium oxide nanoparticles-part 2: nonsize measurements.

    PubMed

    Baalousha, Mohammed; Ju-Nam, Yon; Cole, Paula A; Hriljac, Joseph A; Jones, Ian P; Tyler, Charles R; Stone, Vicki; Fernandes, Teresa F; Jepson, Mark A; Lead, Jamie R

    2012-05-01

    Part 1 (see companion paper) of the present study discussed the application of a multimethod approach in characterizing the size of cerium oxide nanoparticles (NPs). However, other properties less routinely investigated, such as shape and morphology, structure, chemical composition, and surface properties, are likely to play an important role in determining the behavior, reactivity, and potential toxicity of these NPs. The present study describes the measurement of the aforementioned physicochemical properties of NPs (applied also to nanomaterials [NMs]) compared with micrometer particles (MPs). The authors use a wide range of techniques, including high resolution-transmission electron microscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction, X-ray energy dispersive spectroscopy, electron energy loss spectroscopy, X-ray photoelectron spectroscopy, and electrophoresis, and compare these techniques, their advantages, and their limitations, along with recommendations about how best to approach NM characterization, using an application to commercial cerium oxide NPs and MPs. Results show that both cerium oxide NPs and MPs are formed of single polyhedron or truncated polyhedron crystals. Cerium oxide NPs contain a mixture of Ce(3+) and Ce(4+) cations, whereas the MPs contain mainly Ce(4+) , which is potentially important in understanding the toxicity of cerium oxide NPs. The isoelectric point of cerium oxide NPs was approximately pH 8, which explains their propensity to aggregate in aqueous media (see companion paper).

  20. Cerium oxide nanoparticles are more toxic than equimolar bulk cerium oxide in Caenorhabditis elegans.

    PubMed

    Arnold, M C; Badireddy, A R; Wiesner, M R; Di Giulio, R T; Meyer, J N

    2013-08-01

    Engineered cerium oxide nanoparticles (CeO2 NPs) are widely used in biomedical and engineering manufacturing industries. Previous research has shown the ability of CeO2 NPs to act as a redox catalyst, suggesting potential to both induce and alleviate oxidative stress in organisms. In this study, Caenorhabditis elegans and zebrafish (Danio rerio) were dosed with commercially available CeO2 NPs. Non-nano cerium oxide powder (CeO2) was used as a positive control for cerium toxicity. CeO2 NPs suspended in standard United States Environmental Protection Agency reconstituted moderately hard water, used to culture the C. elegans, quickly formed large polydisperse aggregates. Dosing solutions were renewed daily for 3 days. Exposure of wild-type nematodes resulted in dose-dependent growth inhibition detected for all 3 days (p < 0.0001). Non-nano CeO2 also caused significant growth inhibition (p < 0.0001), but the scale of inhibition was less at equivalent mass exposures compared with CeO2 NP exposure. Some metal and oxidative stress-sensitive mutant nematode strains showed mildly altered growth relative to the wild-type when dosed with 5 mg/L CeO2 NPs on days 2 and 3, thus providing weak evidence for a role for oxidative stress or metal sensitivity in CeO2 NP toxicity. Zebrafish microinjected with CeO2 NPs or CeO2 did not exhibit increased gross developmental defects compared with controls. Hyperspectral imaging showed that CeO2 NPs were ingested but not detectable inside the cells of C. elegans. Growth inhibition observed in C. elegans may be explained at least in part by a non-specific inhibition of feeding caused by CeO2 NPs aggregating around bacterial food and/or inside the gut tract.

  1. Uptake and accumulation of bulk and nanosized cerium oxide particles and ionic cerium by radish (Raphanus sativus L.).

    PubMed

    Zhang, Weilan; Ebbs, Stephen D; Musante, Craig; White, Jason C; Gao, Cunmei; Ma, Xingmao

    2015-01-21

    The potential toxicity and accumulation of engineered nanomaterials (ENMs) in agricultural crops has become an area of great concern and intense investigation. Interestingly, although below-ground vegetables are most likely to accumulate the highest concentrations of ENMs, little work has been done investigating the potential uptake and accumulation of ENMs for this plant group. The overall objective of this study was to evaluate how different forms of cerium (bulk cerium oxide, cerium oxide nanoparticles, and the cerium ion) affected the growth of radish (Raphanus sativus L.) and accumulation of cerium in radish tissues. Ionic cerium (Ce(3+)) had a negative effect on radish growth at 10 mg CeCl3/L, whereas bulk cerium oxide (CeO2) enhanced plant biomass at the same concentration. Treatment with 10 mg/L cerium oxide nanoparticles (CeO2 NPs) had no significant effect on radish growth. Exposure to all forms of cerium resulted in the accumulation of this element in radish tissues, including the edible storage root. However, the accumulation patterns and their effect on plant growth and physiological processes varied with the characteristics of cerium. This study provides a critical frame of reference on the effects of CeO2 NPs versus their bulk and ionic counterparts on radish growth.

  2. Control of cerium oxidation state through metal complex secondary structures

    SciTech Connect

    Levin, Jessica R.; Dorfner, Walter L.; Carroll, Patrick J.; Schelter, Eric J.

    2015-08-11

    A series of alkali metal cerium diphenylhydrazido complexes, Mx(py)y[Ce(PhNNPh)4], M = Li, Na, and K, x = 4 (Li and Na) or 5 (K), and y = 4 (Li), 8 (Na), or 7 (K), were synthesized to probe how a secondary coordination sphere would modulate electronic structures at a cerium cation. The resulting electronic structures of the heterobimetallic cerium diphenylhydrazido complexes were found to be strongly dependent on the identity of the alkali metal cations. When M = Li+ or Na+, the cerium(III) starting material was oxidized with concomitant reduction of 1,2-diphenylhydrazine to aniline. Reduction of 1,2-diphenylhydrazine was not observed when M = K+, and the complex remained in the cerium(III) oxidation state. Oxidation of the cerium(III) diphenylhydrazido complex to the Ce(IV) diphenylhydrazido one was achieved through a simple cation exchange reaction of the alkali metals. As a result, UV-Vis spectroscopy, FTIR spectroscopy, electrochemistry, magnetic susceptibility, and DFT studies were used to probe the oxidation state and the electronic changes that occurred at the metal centre.

  3. Control of cerium oxidation state through metal complex secondary structures

    DOE PAGES

    Levin, Jessica R.; Dorfner, Walter L.; Carroll, Patrick J.; ...

    2015-08-11

    A series of alkali metal cerium diphenylhydrazido complexes, Mx(py)y[Ce(PhNNPh)4], M = Li, Na, and K, x = 4 (Li and Na) or 5 (K), and y = 4 (Li), 8 (Na), or 7 (K), were synthesized to probe how a secondary coordination sphere would modulate electronic structures at a cerium cation. The resulting electronic structures of the heterobimetallic cerium diphenylhydrazido complexes were found to be strongly dependent on the identity of the alkali metal cations. When M = Li+ or Na+, the cerium(III) starting material was oxidized with concomitant reduction of 1,2-diphenylhydrazine to aniline. Reduction of 1,2-diphenylhydrazine was not observedmore » when M = K+, and the complex remained in the cerium(III) oxidation state. Oxidation of the cerium(III) diphenylhydrazido complex to the Ce(IV) diphenylhydrazido one was achieved through a simple cation exchange reaction of the alkali metals. As a result, UV-Vis spectroscopy, FTIR spectroscopy, electrochemistry, magnetic susceptibility, and DFT studies were used to probe the oxidation state and the electronic changes that occurred at the metal centre.« less

  4. Electrode electrolyte interlayers containing cerium oxide for electrochemical fuel cells

    DOEpatents

    Borglum, Brian P.; Bessette, Norman F.

    2000-01-01

    An electrochemical cell is made having a porous fuel electrode (16) and a porous air electrode (13), with solid oxide electrolyte (15) therebetween, where the air electrode surface opposing the electrolyte has a separate, attached, dense, continuous layer (14) of a material containing cerium oxide, and where electrolyte (16) contacts the continuous oxide layer (14), without contacting the air electrode (13).

  5. Optical and electrical studies of cerium mixed oxides

    SciTech Connect

    Sherly, T. R.; Raveendran, R.

    2014-10-15

    The fast development in nanotechnology makes enthusiastic interest in developing nanomaterials having tailor made properties. Cerium mixed oxide materials have received great attention due to their UV absorption property, high reactivity, stability at high temperature, good electrical property etc and these materials find wide applications in solid oxide fuel cells, solar control films, cosmetics, display units, gas sensors etc. In this study cerium mixed oxide compounds were prepared by co-precipitation method. All the samples were doped with Zn (II) and Fe (II). Preliminary characterizations such as XRD, SEM / EDS, TEM were done. UV - Vis, Diffuse reflectance, PL, FT-IR, Raman and ac conductivity studies of the samples were performed.

  6. Optical and electrical studies of cerium mixed oxides

    NASA Astrophysics Data System (ADS)

    Sherly, T. R.; Raveendran, R.

    2014-10-01

    The fast development in nanotechnology makes enthusiastic interest in developing nanomaterials having tailor made properties. Cerium mixed oxide materials have received great attention due to their UV absorption property, high reactivity, stability at high temperature, good electrical property etc and these materials find wide applications in solid oxide fuel cells, solar control films, cosmetics, display units, gas sensors etc. In this study cerium mixed oxide compounds were prepared by co-precipitation method. All the samples were doped with Zn (II) and Fe (II). Preliminary characterizations such as XRD, SEM / EDS, TEM were done. UV - Vis, Diffuse reflectance, PL, FT-IR, Raman and ac conductivity studies of the samples were performed.

  7. Synthesis and characterization of magnesium doped cerium oxide for the fuel cell application

    NASA Astrophysics Data System (ADS)

    Kumar, Amit; Kumari, Monika; Kumar, Mintu; Kumar, Sacheen; Kumar, Dinesh

    2016-05-01

    Cerium oxide has attained much attentions in global nanotechnology market due to valuable application for catalytic, fuel additive, and widely as electrolyte in solid oxide fuel cell. Doped cerium oxide has large oxygen vacancies that allow for greater reactivity and faster ion transport. These properties make cerium oxide suitable material for SOFCs application. Cerium oxide electrolyte requires lower operation temperature which shows improvement in processing and the fabrication technique. In our work, we synthesized magnesium doped cerium oxide by the co-precipitation method. With the magnesium doping catalytic reactivity of CeO2 was increased. Synthesized nanoparticle were characterized by the XRD and UV absorption techniques.

  8. The effective thermal conductivity of an adsorbent - Praseodymium cerium oxide

    NASA Technical Reports Server (NTRS)

    Secary, J. J.; Tong, T. W.

    1992-01-01

    The results of an experimental study to determine the effective thermal conductivity of praseodymium cerium oxide are reported. Praseodymium cerium oxide is an adsorbent used in the development of adsorption compressors for spaceborne refrigeration systems. A guarded-hot-plate apparatus was built for this study. Measurements were carried out for mean temperatures ranging from 300 to 600 C under a vacuum of 10 exp -5 torr. For the temperature range studied, the effective thermal conductivity increased from 0.14 to 0.76 W/m per C with increasing temperature, while displaying a cubic temperature dependency.

  9. IRIS TOXICOLOGICAL REVIEW AND SUMMARY DOCUMENTS FOR CERIUM OXIDE (STABLE) AND COMPOUNDS

    EPA Science Inventory

    Cerium is a member of the lanthanoid series of rare earth metals. It is also the most abundant and most reactive of the rare earth metals. Cerium oxidizes at room temperature and forms a variety of salt compounds including oxides, hydroxides, sulfates and chlorides. Cerium is ...

  10. Molecular and physiological responses to titanium dioxide and cerium oxide nanoparticles in arabidopsis

    EPA Science Inventory

    - Changes in tissue transcriptomes and productivity of Arabidopsis thaliana were investigated during exposure of plants to two widely-used engineered metal oxide nanoparticles, titanium dioxide (nano-titanium) and cerium dioxide (nano-cerium). Microarray analyses confirmed that e...

  11. Cerium fluoride nanoparticles protect cells against oxidative stress.

    PubMed

    Shcherbakov, Alexander B; Zholobak, Nadezhda M; Baranchikov, Alexander E; Ryabova, Anastasia V; Ivanov, Vladimir K

    2015-05-01

    A novel facile method of non-doped and fluorescent terbium-doped cerium fluoride stable aqueous sols synthesis is proposed. Intense green luminescence of CeF3:Tb nanoparticles can be used to visualize these nanoparticles' accumulation in cells using confocal laser scanning microscopy. Cerium fluoride nanoparticles are shown for the first time to protect both organic molecules and living cells from the oxidative action of hydrogen peroxide. Both non-doped and terbium-doped CeF3 nanoparticles are shown to provide noteworthy protection to cells against the vesicular stomatitis virus.

  12. Toxicity study of cerium oxide nanoparticles in human neuroblastoma cells.

    PubMed

    Kumari, Monika; Singh, Shailendra Pratap; Chinde, Srinivas; Rahman, Mohammed Fazlur; Mahboob, Mohammed; Grover, Paramjit

    2014-01-01

    The present study consisted of cytotoxic, genotoxic, and oxidative stress responses of human neuroblastoma cell line (IMR32) following exposure to different doses of cerium oxide nanoparticles (CeO2 NPs; nanoceria) and its microparticles (MPs) for 24 hours. Cytotoxicity was evaluated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide and lactate dehydrogenase assays whereas genotoxicity was assessed using the cytokinesis-block micronucleus and comet assays. A battery of assays including lipid peroxidation, reactive oxygen species (ROS), hydrogen peroxide, reduced glutathione, nitric oxide, glutathione reductase, glutathione peroxidase, superoxide dismutase, catalase, and glutathione S-transferase were performed to test the hypothesis that ROS was responsible for the toxicity of nanoceria. The results showed that nanosized CeO2 was more toxic than cerium oxide MPs. Hence, further study on safety evaluation of CeO2 NPs on other models is recommended.

  13. Processing and Characterization of Sol-Gel Cerium Oxide Microspheres

    SciTech Connect

    McClure, Zachary D.; Padilla Cintron, Cristina

    2016-09-27

    Of interest to space exploration and power generation, Radioisotope Thermoelectric Generators (RTGs) can provide long-term power to remote electronic systems without the need for refueling or replacement. Plutonium-238 (Pu-238) remains one of the more promising materials for thermoelectric power generation due to its high power density, long half-life, and low gamma emissions. Traditional methods for processing Pu-238 include ball milling irregular precipitated powders before pressing and sintering into a dense pellet. The resulting submicron particulates of Pu-238 quickly accumulate and contaminate glove boxes. An alternative and dust-free method for Pu-238 processing is internal gelation via sol-gel techniques. Sol-gel methodology creates monodisperse and uniform microspheres that can be packed and pressed into a pellet. For this study cerium oxide microspheres were produced as a surrogate to Pu-238. The similar electronic orbitals between cerium and plutonium make cerium an ideal choice for non-radioactive work. Before the microspheres can be sintered and pressed they must be washed to remove the processing oil and any unreacted substituents. An investigation was performed on the washing step to find an appropriate wash solution that reduced waste and flammable risk. Cerium oxide microspheres were processed, washed, and characterized to determine the effectiveness of the new wash solution.

  14. Fungus mediated synthesis of biomedically important cerium oxide nanoparticles

    SciTech Connect

    Khan, Shadab Ali; Ahmad, Absar

    2013-10-15

    Graphical abstract: - Highlights: • First time biological synthesis of cerium oxide oxide nanoparticles using fungus Humicola sp. • Complete characterization of cerium oxide nanoparticles. • Biosynthesis of naturally protein capped, luminescent and water dispersible CeO{sub 2} nanoparticles. • Biosynthesized CeO{sub 2} nanoparticles can be used for many biomedical applications. - Abstract: Nanomaterials can be synthesized by chemical, physical and the more recently discovered biological routes. The biological routes are advantageous over the chemical and physical ones as unlike these, the biological synthesis protocols occur at ambient conditions, are cheap, non-toxic and eco-friendly. Although purely biological and bioinspired methods for the synthesis of nanomaterials are environmentally benign and energy conserving processes, their true potential has not been explored yet and attempts are being made to extend the formation of technologically important nanoparticles using microorganisms like fungi. Though there have been reports on the biosynthesis of oxide nanoparticles by our group in the past, no attempts have been made to employ fungi for the synthesis of nanoparticles of rare earth metals or lanthanides. Here we report for the first time, the bio-inspired synthesis of biomedically important cerium oxide (CeO{sub 2}) nanoparticles using the thermophilic fungus Humicola sp. The fungus Humicola sp. when exposed to aqueous solutions of oxide precursor cerium (III) nitrate hexahydrate (CeN{sub 3}O{sub 9}·6H{sub 2}O) results in the extracellular formation of CeO{sub 2} nanoparticles containing Ce (III) and Ce (IV) mixed oxidation states, confirmed by X-ray Photoemission Spectroscopy (XPS). The formed nanoparticles are naturally capped by proteins secreted by the fungus and thus do not agglomerate, are highly stable, water dispersible and are highly fluorescent as well. The biosynthesized nanoparticles were characterized by UV–vis spectroscopy

  15. Fundamental aspects of regenerative cerium oxide nanoparticles and their applications in nanobiotechnology

    NASA Astrophysics Data System (ADS)

    Patil, Swanand D.

    Cerium oxide has been used extensively for various applications over the past two decades. The use of cerium oxide nanoparticles is beneficial in present applications and can open avenues for future applications. The present study utilizes the microemulsion technique to synthesize uniformly distributed cerium oxide nanoparticles. The same technique was also used to synthesize cerium oxide nanoparticles doped with trivalent elements (La and Nd). The fundamental study of cerium oxide nanoparticles identified variations in properties as a function of particle size and also due to doping with trivalent elements (La and Nd). It was found that the lattice parameter of cerium oxide nanoparticles increases with decrease in particle size. Also Raman allowed mode shift to lower energies and the peak at 464 cm-1 becomes broader and asymmetric. The size dependent changes in cerium oxide were correlated to increase in oxygen vacancy concentration in the cerium oxide lattice. The doping of cerium oxide nanoparticles with trivalent elements introduces more oxygen vacancies and expands the cerium oxide lattice further (in addition to the lattice expansion due to the size effect). The lattice expansion is greater for La-doped cerium oxide nanoparticles compared to Nd-doping due to the larger ionic radius of La compared to Nd, the lattice expansion is directly proportional to the dopant concentration. The synthesized cerium oxide nanoparticles were used to develop an electrochemical biosensor of hydrogen peroxide (H2O2). The sensor was useful to detect H2O2 concentrations as low as 1muM in water. Also the preliminary testing of the sensor on tomato stem and leaf extracts indicated that the sensor can be used in practical applications such as plant physiological studies etc. The nanomolar concentrations of cerium oxide nanoparticles were also found to be useful in decreasing ROS (reactive oxygen species) mediated cellular damages in various in vitro cell cultures. Cerium oxide

  16. Engineered cerium oxide nanoparticles: Effects on bacterial growth and viability

    SciTech Connect

    Pelletier, Dale A; Suresh, Anil K; Holton, Gregory A; McKeown, Catherine K; Wang, Wei; Gu, Baohua; Mortensen, Ninell P; Allison, David P; Joy, David Charles; Allison, Martin R; Brown, Steven D; Phelps, Tommy Joe; Doktycz, Mitchel John

    2010-01-01

    Interest in engineered nanostructures has risen in recent years due to their use in energy conservation strategies and biomedicine. To ensure prudent development and use of nanomaterials, the fate and effects of such engineered structures on the environment should be understood. Interactions of nanomaterials with environmental microorganisms are inevitable, but the general consequences of such interactions remain unclear. Further, standardized methods for assessing such interactions are lacking. Therefore, we have initiated a multianalytical approach to understand the interactions of synthesized nanoparticles with bacterial systems. These efforts are focused initially on cerium oxide nanoparticles and model bacteria in order to evaluate characterization procedures and the possible fate of such materials in the environment. In this study the effects of cerium oxide nanoparticles on the growth and viability of Gram-negative Escherichia coli and Shewanella oneidensis, a metal-reducing bacteria, and Gram-positive Bacillus subtilis were examined relative to particle size, growth media, pH, and dosage. A hydrothermal based synthesis procedure was used to prepare cerium oxide nanoparticles of defined sizes in order to eliminate complications originating from the use of organic solvents and surfactants. Bactericidal effects were determined by minimum inhibitory concentration, colony forming units, disc diffusion tests and Live/Dead assays. In growth inhibition experiments involving E. coli and B. subtilis, a clear strain and size-dependent inhibition was observed. S. oneidensis appeared to be unaffected by the cerium oxide nanoparticles. Transmission electron microscopy along with microarray-based transcriptional profiling have been used to understand the response mechanism of the bacteria. The use of multiple analytical approaches adds confidence to toxicity assessments while the use of different bacterial systems highlights the potential wide-ranging effects of

  17. Antibacterial Activity of Polymer Coated Cerium Oxide Nanoparticles

    PubMed Central

    Shah, Vishal; Shah, Shreya; Shah, Hirsh; Rispoli, Fred J.; McDonnell, Kevin T.; Workeneh, Selam; Karakoti, Ajay; Kumar, Amit; Seal, Sudipta

    2012-01-01

    Cerium oxide nanoparticles have found numerous applications in the biomedical industry due to their strong antioxidant properties. In the current study, we report the influence of nine different physical and chemical parameters: pH, aeration and, concentrations of MgSO4, CaCl2, KCl, natural organic matter, fructose, nanoparticles and Escherichia coli, on the antibacterial activity of dextran coated cerium oxide nanoparticles. A least-squares quadratic regression model was developed to understand the collective influence of the tested parameters on the anti-bacterial activity and subsequently a computer-based, interactive visualization tool was developed. The visualization allows us to elucidate the effect of each of the parameters in combination with other parameters, on the antibacterial activity of nanoparticles. The results indicate that the toxicity of CeO2 NPs depend on the physical and chemical environment; and in a majority of the possible combinations of the nine parameters, non-lethal to the bacteria. In fact, the cerium oxide nanoparticles can decrease the anti-bacterial activity exerted by magnesium and potassium salts. PMID:23110109

  18. Induction of pulmonary fibrosis by cerium oxide nanoparticles

    SciTech Connect

    Ma, Jane Y.; Mercer, Robert R.; Barger, Mark; Schwegler-Berry, Diane; Scabilloni, James; Ma, Joseph K.; Castranova, Vincent

    2012-08-01

    Cerium compounds have been used as a diesel engine catalyst to lower the mass of diesel exhaust particles, but are emitted as cerium oxide (CeO{sub 2}) nanoparticles in the diesel exhaust. In a previous study, we have demonstrated a wide range of CeO{sub 2}-induced lung responses including sustained pulmonary inflammation and cellular signaling that could lead to pulmonary fibrosis. In this study, we investigated the fibrogenic responses induced by CeO{sub 2} in a rat model at various time points up to 84 days post-exposure. Male Sprague Dawley rats were exposed to CeO{sub 2} by a single intratracheal instillation. Alveolar macrophages (AM) were isolated by bronchial alveolar lavage (BAL). AM-mediated cellular responses, osteopontin (OPN) and transform growth factor (TGF)-β1 in the fibrotic process were investigated. The results showed that CeO{sub 2} exposure significantly increased fibrotic cytokine TGF-β1 and OPN production by AM above controls. The collagen degradation enzymes, matrix metalloproteinase (MMP)-2 and -9 and the tissue inhibitor of MMP were markedly increased in the BAL fluid at 1 day- and subsequently declined at 28 days after exposure, but remained much higher than the controls. CeO{sub 2} induced elevated phospholipids in BAL fluid and increased hydroxyproline content in lung tissue in a dose- and time-dependent manner. Immunohistochemical analysis showed MMP-2, MMP-9 and MMP-10 expressions in fibrotic regions. Morphological analysis noted increased collagen fibers in the lungs exposed to a single dose of 3.5 mg/kg CeO{sub 2} and euthanized at 28 days post-exposure. Collectively, our studies show that CeO{sub 2} induced fibrotic lung injury in rats, suggesting it may cause potential health effects. -- Highlights: ► Cerium oxide exposure significantly affected the following parameters in the lung. ► Induced fibrotic cytokine OPN and TGF-β1 production and phospholipidosis. ► Caused imbalance of the MMP-9/ TIMP-1 ratio that favors fibrosis

  19. Environmental Geochemistry of Cerium: Applications and Toxicology of Cerium Oxide Nanoparticles

    PubMed Central

    Dahle, Jessica T.; Arai, Yuji

    2015-01-01

    Cerium is the most abundant of rare-earth metals found in the Earth’s crust. Several Ce-carbonate, -phosphate, -silicate, and -(hydr)oxide minerals have been historically mined and processed for pharmaceutical uses and industrial applications. Of all Ce minerals, cerium dioxide has received much attention in the global nanotechnology market due to their useful applications for catalysts, fuel cells, and fuel additives. A recent mass flow modeling study predicted that a major source of CeO2 nanoparticles from industrial processing plants (e.g., electronics and optics manufactures) is likely to reach the terrestrial environment such as landfills and soils. The environmental fate of CeO2 nanoparticles is highly dependent on its physcochemical properties in low temperature geochemical environment. Though there are needs in improving the analytical method in detecting/quantifying CeO2 nanoparticles in different environmental media, it is clear that aquatic and terrestrial organisms have been exposed to CeO2 NPs, potentially yielding in negative impact on human and ecosystem health. Interestingly, there has been contradicting reports about the toxicological effects of CeO2 nanoparticles, acting as either an antioxidant or reactive oxygen species production-inducing agent). This poses a challenge in future regulations for the CeO2 nanoparticle application and the risk assessment in the environment. PMID:25625406

  20. Environmental geochemistry of cerium: applications and toxicology of cerium oxide nanoparticles.

    PubMed

    Dahle, Jessica T; Arai, Yuji

    2015-01-23

    Cerium is the most abundant of rare-earth metals found in the Earth's crust. Several Ce-carbonate, -phosphate, -silicate, and -(hydr)oxide minerals have been historically mined and processed for pharmaceutical uses and industrial applications. Of all Ce minerals, cerium dioxide has received much attention in the global nanotechnology market due to their useful applications for catalysts, fuel cells, and fuel additives. A recent mass flow modeling study predicted that a major source of CeO2 nanoparticles from industrial processing plants (e.g., electronics and optics manufactures) is likely to reach the terrestrial environment such as landfills and soils. The environmental fate of CeO2 nanoparticles is highly dependent on its physcochemical properties in low temperature geochemical environment. Though there are needs in improving the analytical method in detecting/quantifying CeO2 nanoparticles in different environmental media, it is clear that aquatic and terrestrial organisms have been exposed to CeO2 NPs, potentially yielding in negative impact on human and ecosystem health. Interestingly, there has been contradicting reports about the toxicological effects of CeO2 nanoparticles, acting as either an antioxidant or reactive oxygen species production-inducing agent). This poses a challenge in future regulations for the CeO2 nanoparticle application and the risk assessment in the environment.

  1. Functionalization of nanostructured cerium oxide films with histidine.

    PubMed

    Tsud, Nataliya; Bercha, Sofiia; Acres, Robert G; Vorokhta, Mykhailo; Khalakhan, Ivan; Prince, Kevin C; Matolín, Vladimír

    2015-01-28

    The surfaces of polycrystalline cerium oxide films were modified by histidine adsorption under vacuum and characterized by the synchrotron based techniques of core and valence level photoemission, resonant photoemission and near edge X-ray absorption spectroscopy, as well as atomic force microscopy. Histidine is strongly bound to the oxide surface in the anionic form through the deprotonated carboxylate group, and forms a disordered molecular adlayer. The imidazole ring and the amino side group do not form bonds with the substrate but are involved in the intermolecular hydrogen bonding which stabilizes the molecular adlayer. The surface reaction with histidine results in water desorption accompanied by oxide reduction, which is propagated into the bulk of the film. Previously studied, well-characterized surfaces are a guide to the chemistry of the present polycrystalline surface and histidine bonds via the carboxylate group in both cases. In contrast, bonding via the imidazole group occurs on the well-ordered surface but not in the present case. The morphology and structure of the cerium oxide are decisive factors which define the adsorption geometry of the histidine adlayer.

  2. Superconductive articles including cerium oxide layer

    DOEpatents

    Wu, Xin D.; Muenchausen, Ross E.

    1993-01-01

    A ceramic superconductor comprising a metal oxide substrate, a ceramic high temperature superconductive material, and a intermediate layer of a material having a cubic crystal structure, said layer situated between the substrate and the superconductive material is provided, and a structure for supporting a ceramic superconducting material is provided, said structure comprising a metal oxide substrate, and a layer situated over the surface of the substrate to substantially inhibit interdiffusion between the substrate and a ceramic superconducting material deposited upon said structure.

  3. Superconductive articles including cerium oxide layer

    DOEpatents

    Wu, X.D.; Muenchausen, R.E.

    1993-11-16

    A ceramic superconductor comprising a metal oxide substrate, a ceramic high temperature superconductive material, and a intermediate layer of a material having a cubic crystal structure, said layer situated between the substrate and the superconductive material is provided, and a structure for supporting a ceramic superconducting material is provided, said structure comprising a metal oxide substrate, and a layer situated over the surface of the substrate to substantially inhibit interdiffusion between the substrate and a ceramic superconducting material deposited upon said structure. 7 figures.

  4. Role of nanocrystalline cerium oxide coatings on austenitic stainless steels

    NASA Astrophysics Data System (ADS)

    Zhang, Haiying

    Protective nanocrystalline cerium oxide coating has been applied to ASTM grade 304L and 304 austenitic stainless steels to improve its oxidation resistance at elevated temperatures. Experimentally, the selected alloy was exposed to 800°C/1000°C under dry air conditions. Weight changes (DeltaW/A) were monitored as a function of time and the results were compared with uncoated alloys tested under similar conditions. It was found that the oxidation resistances of 304L and 304 stainless steels were significantly improved. A comparison of the oxidation rates indicated that the nanocrystalline cerium oxide coating reduced the rate of oxidation by more than two orders of magnitude. Nevertheless, a comprehensive understanding of the mechanisms responsible for the reduction in the oxidation rate is not clear. Consequently, this work is aimed at investigating the mechanisms involved during scale growth in the presence or absence of nanocrystalline coatings. For this purpose, density functional theory was carried out in order to predict oxygen and iron diffusion microscopic activation energies and reveal the intrinsic characteristics of nanocrystalline coatings. A numerical simulation of corrosion process has also been conducted to predict the corrosion rates of alloys with and without coatings. Hence, the results from simulations are compared with the experimental outcome, and possible explanations are given to account for the reduction in the exhibited oxidation rates. The simulation results will provide a highly valuable tool for the realization of functional nanostructures and architectures "by design", particularly in the development of novel coatings, and a new approach of life assessment.

  5. Design better cerium-based oxidation catalysts

    SciTech Connect

    Trovarelli, A.; Leitenburg, C. de; Dolcetti, G.

    1997-06-01

    Structural and energetic factors play an important role in the development of a new generation of automobile exhaust catalysts containing CeO{sub 2} doped with ZrO{sub 2} and/or other rare earth oxides such as PrO{sub x}, Y{sub 2}O{sub 3}, and La{sub 2}O{sub 3}. These new catalysts possess high oxygen storage capacity, improved thermal stability, and enhanced catalytic properties. These properties are discussed.

  6. Green synthesized cerium oxide nanoparticle: A prospective drug against oxidative harm.

    PubMed

    Dutta, Debanjan; Mukherjee, Riya; Patra, Mousumi; Banik, Milon; Dasgupta, Rakhi; Mukherjee, Manabendra; Basu, Tarakdas

    2016-11-01

    Cerium oxide nanoparticle (CeONP) of size 2-3nm was synthesized by a new, simple and green method at ambient temperature, using cerium nitrate as prime precursor and Aloe vera leaf extract as stabilizing agent. Of the two oxidation states (+3) and (+4) of cerium, it was dominantly present in (+3) state in CeONP and cyclic conversion of Ce(III)O→Ce(IV)O→Ce(III)O by reaction with H2O2 implied uninterrupted antioxidant property of CeONP. Moreover, the higher oxygen defect in the crystal lattice produced particles with higher antioxidant activity. CeONP was found to neutralize the deleterious effects of H2O2 viz., cell death, generation of intracellular reactive oxygen species and loss of connectivity in mouse neural cells. Therefore, CeONP might have potential use in future as an anti-oxidant drug.

  7. Fabrication of Cerium Oxide and Uranium Oxide Microspheres for Space Nuclear Power Applications

    SciTech Connect

    Jeffrey A. Katalenich; Michael R. Hartman; Robert C. O'Brien

    2013-02-01

    Cerium oxide and uranium oxide microspheres are being produced via an internal gelation sol-gel method to investigate alternative fabrication routes for space nuclear fuels. Depleted uranium and non-radioactive cerium are being utilized as surrogates for plutonium-238 (Pu-238) used in radioisotope thermoelectric generators and for enriched uranium required by nuclear thermal rockets. While current methods used to produce Pu-238 fuels at Los Alamos National Laboratory (LANL) involve the generation of fine powders that pose a respiratory hazard and have a propensity to contaminate glove boxes, the sol-gel route allows for the generation of oxide microsphere fuels through an aqueous route. The sol-gel method does not generate fine powders and may require fewer processing steps than the LANL method with less operator handling. High-quality cerium dioxide microspheres have been fabricated in the desired size range and equipment is being prepared to establish a uranium dioxide microsphere production capability.

  8. Altering properties of cerium oxide thin films by Rh doping

    SciTech Connect

    Ševčíková, Klára; Nehasil, Václav; Vorokhta, Mykhailo; Haviar, Stanislav; Matolín, Vladimír; and others

    2015-07-15

    Highlights: • Thin films of ceria doped by rhodium deposited by RF magnetron sputtering. • Concentration of rhodium has great impact on properties of Rh–CeO{sub x} thin films. • Intensive oxygen migration in films with low concentration of rhodium. • Oxygen migration suppressed in films with high amount of Rh dopants. - Abstract: Ceria containing highly dispersed ions of rhodium is a promising material for catalytic applications. The Rh–CeO{sub x} thin films with different concentrations of rhodium were deposited by RF magnetron sputtering and were studied by soft and hard X-ray photoelectron spectroscopies, Temperature programmed reaction and X-ray powder diffraction techniques. The sputtered films consist of rhodium–cerium mixed oxide where cerium exhibits a mixed valency of Ce{sup 4+} and Ce{sup 3+} and rhodium occurs in two oxidation states, Rh{sup 3+} and Rh{sup n+}. We show that the concentration of rhodium has a great influence on the chemical composition, structure and reducibility of the Rh–CeO{sub x} thin films. The films with low concentrations of rhodium are polycrystalline, while the films with higher amount of Rh dopants are amorphous. The morphology of the films strongly influences the mobility of oxygen in the material. Therefore, varying the concentration of rhodium in Rh–CeO{sub x} thin films leads to preparing materials with different properties.

  9. Pilot demonstration of cerium oxide coated anodes

    SciTech Connect

    Gregg, J.S.; Frederick, M.S.; Shingler, M.J.; Alcorn, T.R.

    1992-10-01

    Cu cermet anodes were tested for 213 to 614 hours with an in-situ deposited CEROX coating in a pilot cell operated by Reynolds Manufacturing Technology Laboratory. At high bath ratio ([approximately]1.5) and low current density (0.5 A/cm[sup 2]), a [ge]1 mm thick dense CEROX coating was deposited on the anodes. At lower bath ratios and higher current density, the CEROX coating was thinner and less dense, but no change in corrosion rate was noted. Regions of low current density on the anodes and sides adjacent to the carbon anode sometimes had thin or absent CEROX coatings. Problems with cracking and oxidation of the cermet substrates led to higher corrosion rates in a pilot cell than would be anticipated from lab scale results.

  10. Effects of cerium oxide nanoparticles on the proliferation, differentiation, and mineralization function of primary osteoblasts in vitro.

    PubMed

    Zhou, Guoqiang; Gu, Guangqi; Li, Yang; Zhang, Qun; Wang, Wenying; Wang, Shuxiang; Zhang, Jinchao

    2013-06-01

    The effects of cerium oxide nanoparticles on the proliferation, differentiation, and mineralization function of primary osteoblasts in vitro were evaluated. The results showed that the cell biological effects of cerium oxide nanoparticles varied with different diameters. The cytotoxicity of cerium oxide nanoparticles on primary osteoblasts varies with the size and incubation time. Sixty-nanometer cerium oxide nanoparticles show significant cytotoxicity on primary osteoblasts at 48 h exposure. Cerium oxide nanoparticles with diameters of 40 nm promoted the differentiation of osteoblasts and the promotion rate was enhanced with increasing concentration. Cerium oxide nanoparticles with diameters of 60 nm promoted the differentiation of osteoblasts at lower concentrations, but turned to inhibit the differentiation at higher concentrations. Cerium oxide nanoparticles promoted the adipogenic transdifferentiation of osteoblasts at all tested concentrations. Moreover, the effects of 60-nm cerium oxide nanoparticles were stronger than that of 40-nm cerium oxide nanoparticles. Cerium oxide nanoparticles promoted the formation of mineralized matrix nodules of osteoblasts at all tested concentrations in a dose-dependent manner and the promotion rate increased with decreasing size. The results showed that cerium oxide nanoparticles had no acute cytotoxic effects on osteoblasts and could promote the osteogenic differentiation and mineralization of osteoblasts. Moreover, the size, concentration, and culture time of nanoparticles have significant influence on the proliferation, differentiation, and mineralization of osteoblasts.

  11. Enhanced electrochromism in cerium doped molybdenum oxide thin films

    SciTech Connect

    Dhanasankar, M.; Purushothaman, K.K.; Muralidharan, G.

    2010-12-15

    Cerium (5-15% by weight) doped molybdenum oxide thin films have been prepared on FTO coated glass substrate at 250 {sup o}C using sol-gel dip coating method. The structural and morphological changes were observed with the help of XRD, SEM and EDS analysis. The amorphous structure of the Ce doped samples, favours easy intercalation and deintercalation processes. Mo oxide films with 10 wt.% of Ce exhibit maximum anodic diffusion coefficient of 24.99 x 10{sup -11} cm{sup 2}/s and the change in optical transmittance of ({Delta}T at 550 nm) of 79.28% between coloured and bleached state with the optical density of ({Delta}OD) 1.15.

  12. Cerium oxide nanoparticles accelerate the decay of peroxynitrite (ONOO(-)).

    PubMed

    Dowding, Janet M; Seal, Sudipta; Self, William T

    2013-08-01

    Cerium oxide nanoparticles (CeO2 NPs) have been shown to possess a substantial oxygen storage capacity via the interchangeable surface reduction and oxidation of cerium atoms, cycling between the Ce(4+) and Ce(3+) redox states. It has been well established in many studies that depending on their reactivity and surface chemistry, CeO2 NPs can effectively convert both reactive oxygen species (superoxide, O2 (•-), and hydrogen peroxide) into more inert species and scavenge reactive nitrogen species (RNS)(nitric oxide, •NO), both in vitro and in vivo. Since much of damage attributed to •NO and O2 (•-) is actually the result of oxidation or nitration by peroxynitrite or its breakdown products and due to the multiple species that these nanoparticles target in vivo, it was logical to test their interaction with the highly reactive molecule peroxynitrite (ONOO(-)). Here, we report that CeO2 NPs significantly accelerated the decay of ONOO(-) by three independent methods. Additionally, our data suggest the ability of CeO2 NPs to interact with ONOO(-) is independent of the Ce(3+)/Ce(4+) ratio on the surface of the CeO2 NPs. The accelerated decay was not observed when reactions were carried out in an inert gas (argon), suggesting strongly that the decay of peroxynitrite is being accelerated due to a reaction of CeNPs with the carbonate radical anion. These results suggest that one of the protective effects of CeO2 NPs during RNS is likely due to reduction in peroxynitrite or its reactive breakdown products.

  13. Fast synthesis of cerium oxide nanoparticles and nanorods.

    PubMed

    Gao, Feng; Lu, Qingyi; Komarneni, Sridhar

    2006-12-01

    The microwave-hydrothermal method has been investigated for the fast synthesis of rare earth cerium oxide (CeO2) nanoparticles and nanorods. This approach combines the advantages of both hydrothermal and microwave heating techniques. It is facile, rapid, energy-saving, and environmentally-benign and leads to high-yields. The average sizes of the obtained CeO2 nanoparticles could be adjusted from approximatrly 1.6 nm to approximately 20 nm. Moreover, by changing cerium source and adjusting the amount of the added ammonia water, CeO2 nanorods could be synthesized under microwave-assisted conditions for the first time. No calcination process or surfactant is required in our experiments for both CeO2 nanoparticles and nanorods. The ultraviolet and visible (UV-vis) spectra show the obvious size-dependence of the position of the absorbance peak. The Brunaur Emmett Teller (BET) nitrogen adsorption indicates that these nanoparticles and nanorods have high specific surface areas, which are needed for potential applications in many fields. Compared with conventional hydrothermal method, microwave-assisted hydrothermal method shows its advantages of rapidity, convenience and perhaps cost-effectiveness and could be extended to the synthesis of other nanoparticles and nanorods.

  14. Toxicity of Cerium Oxide Nanoparticles in Human Lung Cancer Cells

    SciTech Connect

    Weisheng, Lin; Huang, Yue-wern; Zhou, Xiao Dong; Ma, Yinfa

    2006-12-31

    With the fast development of nanotechnology, the nanomaterials start to cause people's attention for potential toxic effect. In this paper, the cytotoxicity and oxidative stress caused by 20-nm cerium oxide (CeO2) nanoparticles in cultured human lung cancer cells was investigated. The sulforhodamine B method was employed to assess cell viability after exposure to 3.5, 10.5, and 23.3 μg/ml of CeO2 nanoparticles for 24, 48, and 72 h. Cell viability decreased significantly as a function of nanoparticle dose and exposure time. Indicators of oxidative stress and cytotoxicity, including total reactive oxygen species, glutathione, malondialdehyde, α-tocopherol, and lactate dehydrogenase, were quantitatively assessed. It is concluded from the results that free radicals generated by exposure to 3.5 to 23.3 μg/ml CeO2 nanoparticles produce significant oxidative stress in the cells, as reflected by reduced glutathione and α-tocopherol levels; the toxic effects of CeO2 nanoparticles are dose dependent and time dependent; elevated oxidative stress increases the production of malondialdehyde and lactate dehydrogenase, which are indicators of lipid peroxidation and cell membrane damage, respectively.

  15. Cerium oxide nanoparticles: a 'radical' approach to neurodegenerative disease treatment.

    PubMed

    Naz, Shuguftha; Beach, James; Heckert, Blaze; Tummala, Tanuja; Pashchenko, Oleksandra; Banerjee, Tuhina; Santra, Santimukul

    2017-03-01

    Despite advances in understanding the factors that cause many neurodegenerative diseases (NDs), no current therapies have yielded significant results. Cerium oxide nanoparticles (CeONPs) have recently emerged as therapeutics for the treatment of NDs due to their antioxidant properties. This report summarizes the recent findings regarding CeONPs in treatment of various NDs, including Alzheimer's disease, Parkinson's disease, multiple sclerosis, ischemic stroke and amyotrophic lateral sclerosis. Interest in CeONPs as a potential nanomedicine for NDs has increased due to: their ability to alter signaling pathways, small diameter allowing passage through the blood-brain barrier and scavenging of reactive oxygen species. Due to these properties, CeONPs could eventually revolutionize existing treatments for NDs.

  16. Inhaled Diesel Emissions Generated with Cerium Oxide Nanoparticle Fuel Additive Induce Adverse Pulmonary and Systemic Effects

    EPA Science Inventory

    Diesel exhaust (DE) exposure induces adverse cardiopulmonary effects. Cerium oxide nanoparticles added to diesel fuel (DECe) increases fuel burning efficiency but leads to altered emission characteristics and potentially altered health effects. Here, we evaluated whether DECe res...

  17. Recent advances (2010-2015) in studies of cerium oxide nanoparticles' health effects.

    PubMed

    Li, Yan; Li, Peng; Yu, Hua; Bian, Ying

    2016-06-01

    Cerium oxide nanoparticles, widespread applied in our life, have attracted much concern for their human health effects. However, most of the works addressing cerium oxide nanoparticles toxicity have only used in vitro models or in vivo intratracheal instillation methods. The toxicity studies have varied results and not all are conclusive. The information about risk assessments derived from epidemiology studies is severely lacking. The knowledge of occupational safety and health (OSH) for exposed workers is very little. Thus this review focuses on recent advances in studies of toxicokinetics, antioxidant activity and toxicity. Additionally, aim to extend previous health effects assessments of cerium oxide nanoparticles, we summarize the epidemiology studies of engineered cerium oxide nanoparticles used as automotive diesel fuel additive, aerosol particulate matter in air pollution, other industrial ultrafine and nanoparticles (e.g., fumes particles generated in welding and flame cutting processes).

  18. Transformation of Cerium Oxide Nanoparticles from a Diesel Fuel Additive during Combustion in a Diesel Engine.

    PubMed

    Dale, James G; Cox, Steven S; Vance, Marina E; Marr, Linsey C; Hochella, Michael F

    2017-02-21

    Nanoscale cerium oxide is used as a diesel fuel additive to reduce particulate matter emissions and increase fuel economy, but its fate in the environment has not been established. Cerium oxide released as a result of the combustion of diesel fuel containing the additive Envirox, which utilizes suspended nanoscale cerium oxide to reduce particulate matter emissions and increase fuel economy, was captured from the exhaust stream of a diesel engine and was characterized using a combination of bulk analytical techniques and high resolution transmission electron microscopy. The combustion process induced significant changes in the size and morphology of the particles; ∼15 nm aggregates consisting of 5-7 nm faceted crystals in the fuel additive became 50-300 nm, near-spherical, single crystals in the exhaust. Electron diffraction identified the original cerium oxide particles as cerium(IV) oxide (CeO2, standard FCC structure) with no detectable quantities of Ce(III), whereas in the exhaust the ceria particles had additional electron diffraction reflections indicative of a CeO2 superstructure containing ordered oxygen vacancies. The surfactant coating present on the cerium oxide particles in the additive was lost during combustion, but in roughly 30% of the observed particles in the exhaust, a new surface coating formed, approximately 2-5 nm thick. The results of this study suggest that pristine, laboratory-produced, nanoscale cerium oxide is not a good substitute for the cerium oxide released from fuel-borne catalyst applications and that future toxicity experiments and modeling will require the use/consideration of more realistic materials.

  19. Effects of uncoated and citric acid coated cerium oxide nanoparticles, bulk cerium oxide, cerium acetate, and citric acid on tomato plants.

    PubMed

    Barrios, Ana Cecilia; Rico, Cyren M; Trujillo-Reyes, Jesica; Medina-Velo, Illya A; Peralta-Videa, Jose R; Gardea-Torresdey, Jorge L

    2016-09-01

    Little is known about the physiological and biochemical responses of plants exposed to surface modified nanomaterials. In this study, tomato (Solanum lycopersicum L.) plants were cultivated for 210days in potting soil amended with uncoated and citric acid coated cerium oxide nanoparticles (nCeO2, CA+nCeO2) bulk cerium oxide (bCeO2), and cerium acetate (CeAc). Millipore water (MPW), and citric acid (CA) were used as controls. Physiological and biochemical parameters were measured. At 500mg/kg, both the uncoated and CA+nCeO2 increased shoot length by ~9 and ~13%, respectively, while bCeO2 and CeAc decreased shoot length by ~48 and ~26%, respectively, compared with MPW (p≤0.05). Total chlorophyll, chlo-a, and chlo-b were significantly increased by CA+nCeO2 at 250mg/kg, but reduced by bCeO2 at 62.5mg/kg, compared with MPW. At 250 and 500mg/kg, nCeO2 increased Ce in roots by 10 and 7 times, compared to CA+nCeO2, but none of the treatments affected the Ce concentration in above ground tissues. Neither nCeO2 nor CA+nCeO2 affected the homeostasis of nutrient elements in roots, stems, and leaves or catalase and ascorbate peroxidase in leaves. CeAc at 62.5 and 125mg/kg increased B (81%) and Fe (174%) in roots, while at 250 and 500mg/kg, increased Ca in stems (84% and 86%, respectively). On the other hand, bCeO2 at 62.5 increased Zn (152%) but reduced P (80%) in stems. Only nCeO2 at 62.5mg/kg produced higher total number of tomatoes, compared with control and the rest of the treatments. The surface coating reduced Ce uptake by roots but did not affect its translocation to the aboveground organs. In addition, there was no clear effect of surface coating on fruit production. To our knowledge, this is the first study comparing the effects of coated and uncoated nCeO2 on tomato plants.

  20. Pits confined in ultrathin cerium(IV) oxide for studying catalytic centers in carbon monoxide oxidation

    NASA Astrophysics Data System (ADS)

    Sun, Yongfu; Liu, Qinghua; Gao, Shan; Cheng, Hao; Lei, Fengcai; Sun, Zhihu; Jiang, Yong; Su, Haibin; Wei, Shiqiang; Xie, Yi

    2013-11-01

    Finding ideal material models for studying the role of catalytic active sites remains a great challenge. Here we propose pits confined in an atomically thin sheet as a platform to evaluate carbon monoxide catalytic oxidation at various sites. The artificial three-atomic-layer thin cerium(IV) oxide sheet with approximately 20% pits occupancy possesses abundant pit-surrounding cerium sites having average coordination numbers of 4.6 as revealed by X-ray absorption spectroscopy. Density-functional calculations disclose that the four- and five-fold coordinated pit-surrounding cerium sites assume their respective role in carbon monoxide adsorption and oxygen activation, which lowers the activation barrier and avoids catalytic poisoning. Moreover, the presence of coordination-unsaturated cerium sites increases the carrier density and facilitates carbon monoxide diffusion along the two-dimensional conducting channels of surface pits. The atomically thin sheet with surface-confined pits exhibits lower apparent activation energy than the bulk material (61.7 versus 122.9 kJ mol-1), leading to reduced conversion temperature and enhanced carbon monoxide catalytic ability.

  1. Antioxidant Cerium Oxide Nanoparticles in Biology and Medicine

    PubMed Central

    Nelson, Bryant C.; Johnson, Monique E.; Walker, Marlon L.; Riley, Kathryn R.; Sims, Christopher M.

    2016-01-01

    Previously, catalytic cerium oxide nanoparticles (CNPs, nanoceria, CeO2-x NPs) have been widely utilized for chemical mechanical planarization in the semiconductor industry and for reducing harmful emissions and improving fuel combustion efficiency in the automobile industry. Researchers are now harnessing the catalytic repertoire of CNPs to develop potential new treatment modalities for both oxidative- and nitrosative-stress induced disorders and diseases. In order to reach the point where our experimental understanding of the antioxidant activity of CNPs can be translated into useful therapeutics in the clinic, it is necessary to evaluate the most current evidence that supports CNP antioxidant activity in biological systems. Accordingly, the aims of this review are three-fold: (1) To describe the putative reaction mechanisms and physicochemical surface properties that enable CNPs to both scavenge reactive oxygen species (ROS) and to act as antioxidant enzyme-like mimetics in solution; (2) To provide an overview, with commentary, regarding the most robust design and synthesis pathways for preparing CNPs with catalytic antioxidant activity; (3) To provide the reader with the most up-to-date in vitro and in vivo experimental evidence supporting the ROS-scavenging potential of CNPs in biology and medicine. PMID:27196936

  2. Growth and composition of nanostructured and nanoporous cerium oxide thin films on a graphite foil.

    PubMed

    Lavkova, Jaroslava; Khalakhan, Ivan; Chundak, Mykhailo; Vorokhta, Mykhailo; Potin, Valerie; Matolin, Vladimir; Matolinova, Iva

    2015-03-07

    The morphology and composition of CeOx films prepared by r.f. magnetron sputtering on a graphite foil have been investigated mainly by using microscopy methods. This study presents the formation of nanocrystalline layers with porous structure due to the modification of a carbon support and the formation of cerium carbide crystallites as a result of the deposition process. Chemical analyses of the layers with different thicknesses performed by energy dispersive X-ray spectroscopy, electron energy loss spectroscopy and X-ray photoelectron spectroscopy have pointed to the reduction of the cerium oxide layers. In the deposited layers, cerium was present in mixed Ce(3+) and Ce(4+) valence. Ce(3+) species were located mainly at the graphite foil-CeOx interface and the chemical state of cerium was gradually changing to Ce(4+) going to the layer surface. It became more stoichiometric in the case of thicker layers except for the surface region, where the presence of Ce(3+) was associated with oxygen vacancies on the surface of cerium oxide grains. The degree of cerium oxide reduction is discussed in the context of particle size.

  3. Antioxidant properties of cerium oxide nanocrystals as a function of nanocrystal diameter and surface coating.

    PubMed

    Lee, Seung Soo; Song, Wensi; Cho, Minjung; Puppala, Hema L; Nguyen, Phuc; Zhu, Huiguang; Segatori, Laura; Colvin, Vicki L

    2013-11-26

    This work examines the effect of nanocrystal diameter and surface coating on the reactivity of cerium oxide nanocrystals with H2O2 both in chemical solutions and in cells. Monodisperse nanocrystals were formed in organic solvents from the decomposition of cerium precursors, and subsequently phase transferred into water using amphiphiles as nanoparticle coatings. Quantitative analysis of the antioxidant capacity of CeO2-x using gas chromatography and a luminol test revealed that 2 mol of H2O2 reacted with every mole of cerium(III), suggesting that the reaction proceeds via a Fenton-type mechanism. Smaller diameter nanocrystals containing more cerium(III) were found to be more reactive toward H2O2. Additionally, the presence of a surface coating did not preclude the reaction between the nanocrystal surface cerium(III) and hydrogen peroxide. Taken together, the most reactive nanoparticles were the smallest (e.g., 3.8 nm diameter) with the thinnest surface coating (e.g., oleic acid). Moreover, a benchmark test of their antioxidant capacity revealed these materials were 9 times more reactive than commercial antioxidants such as Trolox. A unique feature of these antioxidant nanocrystals is that they can be applied multiple times: over weeks, cerium(IV) rich particles slowly return to their starting cerium(III) content. In nearly all cases, the particles remain colloidally stable (e.g., nonaggregated) and could be applied multiple times as antioxidants. These chemical properties were also observed in cell culture, where the materials were able to reduce oxidative stress in human dermal fibroblasts exposed to H2O2 with efficiency comparable to their solution phase reactivity. These data suggest that organic coatings on cerium oxide nanocrystals do not limit the antioxidant behavior of the nanocrystals, and that their redox cycling behavior can be preserved even when stabilized.

  4. Catalytic Properties and Biomedical Applications of Cerium Oxide Nanoparticles

    PubMed Central

    Walkey, Carl; Das, Soumen; Seal, Sudipta; Erlichman, Joseph; Heckman, Karin; Ghibelli, Lina; Traversa, Enrico; McGinnis, James F.; Self, William T.

    2014-01-01

    Cerium oxide nanoparticles (Nanoceria) have shown promise as catalytic antioxidants in the test tube, cell culture models and animal models of disease. However given the reactivity that is well established at the surface of these nanoparticles, the biological utilization of Nanoceria as a therapeutic still poses many challenges. Moreover the form that these particles take in a biological environment, such as the changes that can occur due to a protein corona, are not well established. This review aims to summarize the existing literature on biological use of Nanoceria, and to raise questions about what further study is needed to apply this interesting catalytic material to biomedical applications. These questions include: 1) How does preparation, exposure dose, route and experimental model influence the reported effects of Nanoceria in animal studies? 2) What are the considerations to develop Nanoceria as a therapeutic agent in regards to these parameters? 3) What biological targets of reactive oxygen species (ROS) and reactive nitrogen species (RNS) are relevant to this targeting, and how do these properties also influence the safety of these nanomaterials? PMID:26207185

  5. Anti-angiogenic activity of heparin functionalised cerium oxide nanoparticles.

    PubMed

    Lord, Megan S; Tsoi, Bonny; Gunawan, Cindy; Teoh, Wey Yang; Amal, Rose; Whitelock, John M

    2013-11-01

    Cerium oxide nanoparticles (nanoceria) are widely reported to be non-cytotoxic and modulate intracellular reactive oxygen species (ROS). In this study, nanoceria (dxRD = 12 nm) were functionalised with either 130 or 880 molecules of unfractionated heparin using the organosilane linker, 3-aminopropyltriethoxysilane. Nanoceria with a low level of heparin functionalisation were found to scavenge intracellular ROS to the same extent as unfunctionalised nanoceria and significantly more than cells exposed to medium only. In contrast, nanoceria with the highest level of heparin functionalisation were not as effective at scavenging intracellular ROS. Nanoceria were localised predominantly in the cytoplasm, while heparin-nanoceria were localised in both the cytoplasm and lysosomes. Together these data demonstrated that the level of nanoceria surface functionalisation with heparin determined the intracellular localisation and ROS scavenging ability of these particles. Additionally, heparin-nanoceria were effective in reducing endothelial cell proliferation indicating that they may find application in the control of angiogenesis in cancer in the future.

  6. Diffuse vacuum arc with cerium oxide hot cathode

    NASA Astrophysics Data System (ADS)

    Amirov, R. Kh; Vorona, N. A.; Gavrikov, A. V.; Liziakin, G. D.; Polistchook, V. P.; Samoylov, I. S.; Smirnov, V. P.; Usmanov, R. A.; Yartsev, I. M.; Ivanov, A. S.

    2016-11-01

    Diffuse vacuum arc with hot cathode is one of the perspective plasma sources for the development of spent nuclear fuel plasma reprocessing technology. Experimental data is known for such type of discharges on metal cathodes. In this work discharge with cerium dioxide hot cathode was studied. Cerium dioxide properties are similar to uranium dioxide. Its feature as dielectric is that it becomes conductive in oxygen-free atmosphere. Vacuum arc was studied at following parameters: cathode temperatures were between 2.0 and 2.2 kK, discharge currents was between 30 and 65 A and voltages was in range from 15 to 25 V. Power flows from plasma to cathode were estimated in achieved regimes. Analysis of generated plasma component composition was made by radiation spectrum diagnostics. These results were compared with calculations of equilibrium gaseous phase above solid sample of cerium dioxide in close to experimental conditions. Cerium dioxide vacuum evaporation rate and evaporation rate in arc were measured.

  7. Variations in Reactivity on Different Crystallographic Orientations of Cerium Oxide

    SciTech Connect

    Mullins, David R; Albrecht, Peter M; Calaza, Florencia C

    2013-01-01

    Cerium oxide is a principal component in many heterogeneous catalytic processes. One of its key characteristics is the ability to provide or remove oxygen in chemical reactions. The different crystallographic faces of ceria present significantly different surface structures and compositions that may alter the catalytic reactivity. The structure and composition determine the number of coordination vacancies surrounding surface atoms, the availability of adsorption sites, the spacing between adsorption sites and the ability to remove O from the surface. To investigate the role of surface orientation on reactivity, CeO2 films were grown with two different orientations. CeO2(100) films were grown ex situ by pulsed laser deposition on Nb-doped SrTiO3(100). CeO2(111) films were grown in situ by thermal deposition of Ce metal onto Ru(0001) in an oxygen atmosphere. The chemical reactivity was characterized by the adsorption and decomposition of various molecules such as alcohols, aldehydes and organic acids. In general the CeO2(100) surface was found to be more active, i.e. molecules adsorbed more readily and reacted to form new products, especially on a fully oxidized substrate. However the CeO2(100) surface was less selective with a greater propensity to produce CO, CO2 and water as products. The differences in chemical reactivity are discussed in light of possible structural terminations of the two surfaces. Recently nanocubes and nano-octahedra have been synthesized that display CeO2(100) and CeO2(111) faces, respectively. These nanoparticles enable us to correlate reactions on high surface area model catalysts at atmospheric pressure with model single crystal films in a UHV environment.

  8. Soil organic matter influences cerium translocation and physiological processes in kidney bean plants exposed to cerium oxide nanoparticles.

    PubMed

    Majumdar, Sanghamitra; Peralta-Videa, Jose R; Trujillo-Reyes, Jesica; Sun, Youping; Barrios, Ana C; Niu, Genhua; Margez, Juan P Flores-; Gardea-Torresdey, Jorge L

    2016-11-01

    Soil organic matter plays a major role in determining the fate of the engineered nanomaterials (ENMs) in the soil matrix and effects on the residing plants. In this study, kidney bean plants were grown in soils varying in organic matter content and amended with 0-500mg/kg cerium oxide nanoparticles (nano-CeO2) under greenhouse condition. After 52days of exposure, cerium accumulation in tissues, plant growth and physiological parameters including photosynthetic pigments (chlorophylls and carotenoids), net photosynthesis rate, transpiration rate, and stomatal conductance were recorded. Additionally, catalase and ascorbate peroxidase activities were measured to evaluate oxidative stress in the tissues. The translocation factor of cerium in the nano-CeO2 exposed plants grown in organic matter enriched soil (OMES) was twice as the plants grown in low organic matter soil (LOMS). Although the leaf cover area increased by 65-111% with increasing nano-CeO2 concentration in LOMS, the effect on the physiological processes were inconsequential. In OMES leaves, exposure to 62.5-250mg/kg nano-CeO2 led to an enhancement in the transpiration rate and stomatal conductance, but to a simultaneous decrease in carotenoid contents by 25-28%. Chlorophyll a in the OMES leaves also decreased by 27 and 18% on exposure to 125 and 250mg/kg nano-CeO2. In addition, catalase activity increased in LOMS stems, and ascorbate peroxidase increased in OMES leaves of nano-CeO2 exposed plants, with respect to control. Thus, this study provides clear evidence that the properties of the complex soil matrix play decisive roles in determining the fate, bioavailability, and biological transport of ENMs in the environment.

  9. Electrooxidation of nitrite on a silica-cerium mixed oxide carbon paste electrode.

    PubMed

    Silveira, Gustavo; de Morais, Andréia; Villis, Paulo César Mendes; Maroneze, Camila Marchetti; Gushikem, Yoshitaka; Lucho, Alzira Maria Serpa; Pissetti, Fábio Luiz

    2012-03-01

    A silica-cerium mixed oxide (SiCe) was prepared by the sol-gel process, using tetraethylorthosilicate and cerium nitrate as precursors and obtained as an amorphous solid possessing a specific surface area of 459 m(2) g(-1). Infrared spectroscopy of the SiCe material showed the formation of the Si-O-Ce linkage in the mixed oxide. Scanning electron microscopy/energy dispersive spectroscopy indicated that the cerium oxide particles were homogenously dispersed on the matrix surface. X-ray diffraction and (29)Si solid-state nuclear magnetic resonance implied non-crystalline silica matrices with chemical environments that are typical for silica-based mixed oxides. X-ray photoelectron spectroscopy showed that Ce was present in approximately equal amounts of both the 3+ and 4+ oxidation states. Cyclic voltammetry data of electrode prepared from the silica-cerium mixed oxide showed a peak for oxidation of Ce(3+)/Ce(4+) at 0.76 V and electrochemical impedance spectroscopy equivalent circuit indicated a porous structure with low charge transfer resistance. In the presence of nitrite, the SiCe electrode shows an anodic oxidation peak at 0.76 V with a linear response as the concentration of the analyte increases from 3×10(-5) at 3.9×10(-3) mol L(-1).

  10. THERMAL EFFECTS ON MASS AND SPATIAL RESOLUTION DURING LASER PULSE ATOM PROBE TOMOGRAPHY OF CERIUM OXIDE

    SciTech Connect

    Rita Kirchhofer; Melissa C. Teague; Brian P. Gorman

    2013-05-01

    Cerium oxide (CeO2) is an ideal surrogate material for trans-uranic elements and fission products found in nuclear fuels due to similarities in their thermal properties; therefore, cerium oxide was used to determine the best run condition for atom probe tomography (APT). Laser pulse APT is a technique that allows for spatial resolution in the nm scale and isotopic/elemental chemical identification. A systematic study of the impact of laser pulse energy and specimen base temperature on the mass resolution, measurement of stoichiometry, multiples, and evaporation mechanisms are reported in this paper. It was demonstrated that using laser pulse APT stoichiometric field evaporation of cerium oxide was achieved at 1 pJ laser pulse energy and 20 K specimen base temperature.

  11. Synthesis and catalytic properties of microemulsion-derived cerium oxide nanoparticles

    SciTech Connect

    Kockrick, Emanuel; Schrage, Christian; Grigas, Anett; Geiger, Dorin; Kaskel, Stefan

    2008-07-15

    The synthesis of cerium dioxide nanoparticles using an inverse microemulsion technique and precipitation method was investigated. Cerium hydroxide nanoparticles were synthesized by adding diluted ammonia to n-heptane-surfactant-cerium nitrate system. The micelle and particle size in the range of 5-12 nm were controlled by varying the molar water to surfactant ratio and analyzed by dynamic light scattering (DLS), small angle X-ray scattering (SAXS) and high-resolution transmission electron microscopy (HRTEM). Cerium hydroxide nanoparticles were isolated and subsequently treated at 100-600 deg. C to obtain nanoscale ceria. Crystallite sizes of cerium dioxide in the range of 6-16 nm were estimated by Scherrer analysis by X-ray diffraction (XRD) and HRTEM. The catalytic activity of particles annealed at 400 and 600 deg. C in soot combustion reactions was characterized by temperature-programmed oxidation (TPO) indicating a size-dependant activity. Crystallite sizes and catalytic stability of elevated ceria systems were tested in second combustion cycles. - Graphical abstract: The synthesis of cerium dioxide nanoparticles using an inverse microemulsion technique and precipitation method was investigated using small angle X-ray scattering, dynamic light scattering and high-resolution transmission electron microscopy. Catalytic activity of ceria nanoparticles was tested in soot combustion reaction indicating size-dependent reactivity.

  12. Effects of Cerium Oxide Nanoparticles on Sorghum Plant Traits

    NASA Astrophysics Data System (ADS)

    Mu, L.; Chen, Y.; Darnault, C. J. G.; Rauh, B.; Kresovich, S.; Korte, C.

    2015-12-01

    Nanotechnology and nanomaterials are considered as the development of the modern science. However, besides with that wide application, nanoparticles arouse to the side effects on the environment and human health. As the catalyst of ceramics and fuel industry, Cerium (IV) oxide nanoparticles (CeO2 NPs) can be found in the environment following their use and life-cycle. Therefore, it is critical to assess the potential effects that CeO2 NPs found in soils may have on plants. In this study, CeO2 NPs were analyzed for the potential influence on the sorghum [Sorghum bicolor (L.) Moench] (Reg. no. 126) (PI 154844) growth and traits. The objectives of this research were to determine whether CeO2 NPs impact the sorghum germination and growth characteristics. The sorghum was grown in the greenhouse located at Biosystems Research Complex, Clemson University under different CeO2 NPs treatments (0mg; 100mg; 500mg; 1000mg CeO2 NPs/Kg soil) and harvested around each month. At the end of the each growing period, above ground vegetative tissue was air-dried, ground to 2mm particle size and compositional traits estimated using near-infrared spectroscopy. Also, the NPK value of the sorghum tissue was tested by Clemson Agriculture Center. After the first harvest, the result showed that the height of above ground biomass under the nanoparticles stress was higher than that of control group. This difference between the control and the nanoparticles treatments was significant (F>F0.05; LSD). Our results also indicated that some of the compositional traits were impacted by the different treatments, including the presence and/or concentrations of the nanoparticles.

  13. Cerium oxide nanoparticle treatment ameliorates peritonitis-induced diaphragm dysfunction.

    PubMed

    Asano, Shinichi; Arvapalli, Ravikumar; Manne, Nandini D P K; Maheshwari, Mani; Ma, Bing; Rice, Kevin M; Selvaraj, Vellaisamy; Blough, Eric R

    2015-01-01

    The severe inflammation observed during sepsis is thought to cause diaphragm dysfunction, which is associated with poor patient prognosis. Cerium oxide (CeO2) nanoparticles have been posited to exhibit anti-inflammatory and antioxidative activities suggesting that these particles may be of potential use for the treatment of inflammatory disorders. To investigate this possibility, Sprague Dawley rats were randomly assigned to the following groups: sham control, CeO2 nanoparticle treatment only (0.5 mg/kg iv), sepsis, and sepsis+CeO2 nanoparticles. Sepsis was induced by the introduction of cecal material (600 mg/kg) directly into the peritoneal cavity. Nanoparticle treatment decreased sepsis-associated impairments in diaphragmatic contractile (P(o)) function (sham: 25.6±1.6 N/cm(2) vs CeO2: 23.4±0.8 N/cm(2) vs Sep: 15.9±1.0 N/cm(2) vs Sep+CeO2: 20.0±1.0 N/cm(2), P<0.05). These improvements in diaphragm contractile function were accompanied by a normalization of protein translation signaling (Akt, FOXO-1, and 4EBP1), diminished proteolysis (caspase 8 and ubiquitin levels), and decreased inflammatory signaling (Stat3 and iNOS). Histological analysis suggested that nanoparticle treatment was associated with diminished sarcolemma damage and diminished inflammatory cell infiltration. These data indicate CeO2 nanoparticles may improve diaphragmatic function in the septic laboratory rat.

  14. Phenotypic and genomic responses to titanium dioxide and cerium oxide nanoparticles in Arabidopsis germinants

    EPA Science Inventory

    The effects of exposure to two nanoparticles (NPs) -titanium dioxide (nano-titania) and cerium oxide (nano-ceria) at 500 mg NPs L-1 on gene expression and growth in Arabidopsis thaliana germinants were studied using microarrays and phenotype studies. After 12 days post treatment,...

  15. Intergenerational responses of wheat (Triticum aestivum L.) to cerium oxide nanoparticles exposure

    EPA Science Inventory

    The intergenerational impact of engineered nanomaterials in plants is a key knowledge gap in the literature. A soil microcosm study was performed to assess the effects of multi-generational exposure of wheat (Triticum aestivum L.) to cerium oxide nanoparticles (CeO2-NPs). Seeds f...

  16. Influences of the main anodic electroplating parameters on cerium oxide films

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Yang, Yumeng; Du, Xiaoqing; Chen, Yu; Zhang, Zhao; Zhang, Jianqing

    2014-06-01

    Cerium oxide thin films were fabricated onto 316 L stainless steel via a potentiostatically anodic electrodeposition approach in the solutions containing cerium(III) nitrate (0.05 M), ammonia acetate (0.1 M) and ethanol (10% V/V). The electrochemical behaviors and deposition parameters (applied potential, bath temperature, dissolving O2 and bath pH) have been investigated. Results show that, the electrochemical oxidation of Ce3+ goes through one electrochemical step, which is under charge transfer control. The optimum applied potential for film deposition is 0.8 V. Bath temperature plays a significant effect on the deposition rate, composition (different colors of the film) and surface morphology of the deposits. Due to the hydrolysis of Ce3+, cerous hydroxide is facility to form when the bath temperature is higher than 60 °C. The electroplating bath pH is another key role for the anodic deposition of cerium oxide thin films, and the best bath pH is around 6.20. N2 or O2 purged into the bath will result in film porosities and O2 favors cerium oxide particles and film generation.

  17. Pre-eminence of the Indirect Channel in the Resonant Inverse Photoelectron Spectroscopy of Cerium Oxide

    SciTech Connect

    Tobin, J. G.; Yu, S. -W.; Chung, B. W.; Waddill, G. D.

    2012-04-01

    We recently reported a strong resonance in the inverse photoelectron spectroscopy (IPES) of cerium oxide. Here, we showed that dominance of the indirect channel of the resonant inverse photoelectron spectroscopy (RIPES) is so complete that the photon energy dependence can be explained in terms of emission associated with a single photon energy.

  18. Photocatalytic action of cerium molybdate and iron-titanium oxide hollow nanospheres on Escherichia coli

    NASA Astrophysics Data System (ADS)

    Kartsonakis, I. A.; Kontogiani, P.; Pappas, G. S.; Kordas, G.

    2013-06-01

    This study is focused on the production of hollow nanospheres that reveal antibacterial action. Cerium molybdate and iron-titanium oxide hollow nanospheres with a diameter of 175 ± 15 and 221 ± 10 nm, respectively, were synthesized using emulsion polymerization and the sol-gel process. Their morphology characterization was accomplished using scanning electron microscopy. Their antibacterial action was examined on pure culture of Escherichia coli considering the loss of their viability. Both hollow nanospheres presented photocatalytic action after illumination with blue-black light, but those of cerium molybdate also demonstrated photocatalytic action in the dark. Therefore, the produced nanospheres can be used for antibacterial applications.

  19. Exposure of cerium oxide nanoparticles to kidney bean shows disturbance in the plant defense mechanisms.

    PubMed

    Majumdar, Sanghamitra; Peralta-Videa, Jose R; Bandyopadhyay, Susmita; Castillo-Michel, Hiram; Hernandez-Viezcas, Jose-Angel; Sahi, Shivendra; Gardea-Torresdey, Jorge L

    2014-08-15

    Overwhelming use of engineered nanoparticles demands rapid assessment of their environmental impacts. The transport of cerium oxide nanoparticles (nCeO2) in plants and their impact on cellular homeostasis as a function of exposure duration is not well understood. In this study, kidney bean plants were exposed to suspensions of ∼ 8 ± 1 nm nCeO2 (62.5 to 500 mg/L) for 15 days in hydroponic conditions. Plant parts were analyzed for cerium accumulation after one, seven, and 15 days of nCeO2 exposure. The primary indicators of stress like lipid peroxidation, antioxidant enzyme activities, total soluble protein and chlorophyll contents were studied. Cerium in tissues was localized using scanning electron microscopy and synchrotron μ-XRF mapping, and the chemical forms were identified using μ-XANES. In the root epidermis, cerium was primarily shown to exist as nCeO2, although a small fraction (12%) was biotransformed to Ce(III) compound. Cerium was found to reach the root vascular tissues and translocate to aerial parts with time. Upon prolonged exposure to 500 mg nCeO2/L, the root antioxidant enzyme activities were significantly reduced, simultaneously increasing the root soluble protein by 204%. In addition, leaf's guaiacol peroxidase activity was enhanced with nCeO2 exposure in order to maintain cellular homeostasis.

  20. Synthesis and catalytic properties of microemulsion-derived cerium oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Kockrick, Emanuel; Schrage, Christian; Grigas, Anett; Geiger, Dorin; Kaskel, Stefan

    2008-07-01

    The synthesis of cerium dioxide nanoparticles using an inverse microemulsion technique and precipitation method was investigated. Cerium hydroxide nanoparticles were synthesized by adding diluted ammonia to n-heptane-surfactant-cerium nitrate system. The micelle and particle size in the range of 5-12 nm were controlled by varying the molar water to surfactant ratio and analyzed by dynamic light scattering (DLS), small angle X-ray scattering (SAXS) and high-resolution transmission electron microscopy (HRTEM). Cerium hydroxide nanoparticles were isolated and subsequently treated at 100-600 °C to obtain nanoscale ceria. Crystallite sizes of cerium dioxide in the range of 6-16 nm were estimated by Scherrer analysis by X-ray diffraction (XRD) and HRTEM. The catalytic activity of particles annealed at 400 and 600 °C in soot combustion reactions was characterized by temperature-programmed oxidation (TPO) indicating a size-dependant activity. Crystallite sizes and catalytic stability of elevated ceria systems were tested in second combustion cycles.

  1. Reactive removal of 2-chloroethyl ethyl sulfide vapors under visible light irradiation by cerium oxide modified highly porous zirconium (hydr) oxide

    NASA Astrophysics Data System (ADS)

    Mitchell, Joshua K.; Arcibar-Orozco, Javier A.; Bandosz, Teresa J.

    2016-12-01

    Highly porous cerium oxide modified Zr(OH)4 samples were synthesized using a simple one stage urea precipitation method. The amorphicity level of zirconium hydroxide did not change upon addition of cerium oxide particles. A unique aspect of the cerium oxide-modified materials is the presence of both the oxide (CeO2) and hydroxide (Zr(OH)4) phases resulting in a unique microporous structure of the final material. Extensive characterization using various chemical and physical methods revealed significant differences in the surface features. All synthesized materials were microporous and small additions of cerium oxide affected the surface chemistry. These samples were found as effective catalysts for a decontamination of mustard gas surrogate, 2-chloroethyl ethyl sulfide (CEES). Cerium oxide addition significantly decreased the band gap of zirconium hydroxide. Ethyl vinyl sulfide and 1,2-bis (Ethyl thio) ethane were identified as surface reaction products.

  2. Exposure, Health and Ecological Effects Review of Engineered Nanoscale Cerium and Cerium Oxide Associated with its Use as a Fuel Additive

    EPA Science Inventory

    Advances of nanoscale science have produced nanomaterials with unique physical and chemical properties at commercial levels which are now incorporated into over 1000 products. Nanoscale cerium (di) oxide (CeO(2)) has recently gained a wide range of applications which includes coa...

  3. Effects of cerium oxide supplementation to laying hen diets on performance, egg quality, some antioxidant enzymes in serum and lipid oxidation in egg yolk.

    PubMed

    Bölükbaşı, S C; Al-Sagan, A A; Ürüşan, H; Erhan, M K; Durmuş, O; Kurt, N

    2016-08-01

    This study was conducted to determine the effects of dietary cerium oxide levels (0, 100, 200, 300 or 400 mg/kg) on the laying performance, egg quality, some blood serum parameters and egg lipid peroxidation of laying hen. In total, one hundred and twenty 22-week-old brown Lohman LSL laying hens were randomly assigned to five groups equally (n = 24). Each treatment was replicated six times. Dietary supplementation of cerium oxide had no significant effect on feed intake and egg weight. The addition of cerium oxide to the laying hens' feed improved feed conversion ratio and increased (p < 0.05) egg production. Quality criteria of egg for except shell breaking strength were not affected by supplementing cerium oxide. In particular, supplementation of 200 and 300 mg/kg cerium oxide to the laying hens feed led to a significant (p < 0. 01) increase in egg shell breaking strength. Calcium and phosphorus concentration of serum increased significantly (p < 0.05) with supplementation of 100 mg/kg cerium oxide to laying hen diets. It was also observed that serum superoxide dismutase (SOD) activity and malondialdehyde (MDA) concentration decreased significantly with supplementation of cerium oxide in diets. Inclusion of cerium oxide resulted in a significant reduction in thiobarbituric acid reactive substance (TBARS) values in egg yolk in this study. It can be concluded that the addition of cerium oxide had positive effects on egg production, feed conversion ratio and egg shelf life. Based on the results of this study, it could be advised to supplement laying hens feed with cerium oxide as feed additives.

  4. Antiapoptotic effects of cerium oxide and yttrium oxide nanoparticles in isolated rat pancreatic islets.

    PubMed

    Hosseini, A; Baeeri, M; Rahimifard, M; Navaei-Nigjeh, M; Mohammadirad, A; Pourkhalili, N; Hassani, S; Kamali, M; Abdollahi, M

    2013-05-01

    Type I diabetes mellitus is a metabolic disease caused by the impairment of pancreatic β-cells mainly mediated through oxidative stress and related apoptosis. Islets transplantation seems a promising treatment for these patients, but during islets transplant, various types of stresses related to the isolation and transplantation procedure compromise the function and viability of islets. We recently hypothesized that the combination of cerium oxide (CeO2) and yttrium oxide (Y2O3) nanoparticles with a potential free radical scavenger behavior should be useful to make isolated islets survive until transplanted. In the present study, oxidative stress-induced apoptosis in isolated rat pancreatic islets exposed to hydrogen peroxide (H2O2) and the protective effects of CeO2 and Y2O3 nanoparticles were investigated. Exposure of islets to H2O2 (50 µm, 2 h) increased intracellular oxidant formation such as reactive oxygen species and subsequently apoptosis and decreased viability, glucose-induced adenosine triphosphate (ATP) production and glucose-stimulated insulin secretion. Pretreatment with CeO2 and/or Y2O3 nanoparticles reduced the oxidant formation and apoptosis and increased viability, glucose-induced ATP production and glucose-stimulated insulin secretion. These results suggest that this combination may protect β-cell apoptosis by improving the oxidative stress-mediated apoptotic pathway.

  5. Improvement of isolated rat pancreatic islets function by combination of cerium oxide nanoparticles/sodium selenite through reduction of oxidative stress.

    PubMed

    Pourkhalili, Nazila; Hosseini, Asieh; Nili-Ahmadabadi, Amir; Rahimifard, Mahban; Navaei-Nigjeh, Mona; Hassani, Shokoufeh; Baeeri, Maryam; Abdollahi, Mohammad

    2012-07-01

    Insulin Dependent Diabetes Mellitus (IDDM) is a disease with high incidence with no pure cure therapy yet. In most of cases, these patients need pancreatic islets transplantation that is not completely successful because of oxidative stress happening during isolation and transplantation procedures. In the present study, effective factors in transplantation procedure such as viability, insulin secretion, production of reactive oxygen molecules (ROM), and mitochondrial energy as ATP/ADP ratio were examined in the isolated islets exposed to sodium selenite (Na₂SeO₃; 0 30 nmol/L), metal form of cerium oxide (100 nm), cerium oxide nanoparticles (100 nm) and combination of Na₂SeO₃ (30 nmol/L)/cerium oxide nanoparticles (100 nm) in a time course (1, 2, 4 and 6 days posttreatment) manner. The results showed a significant increase of cells viability, secretion of insulin, and ATP/ADP ratio and a reduction in ROM by use of sodium selenite, cerium oxide nanoparticles, and especially combination of cerium oxide nanoparticles/sodium selenite. Interestingly, not only no improvement was found with metal form of cerium oxide but also deterioration occurred in tested markers. Results suggest that pretreatment with combination of cerium oxide nanoparticles/sodium selenite can improve transplantation outcome and graft function by control of oxidative stress damage.

  6. Shifts in oxidation states of cerium oxide nanoparticles detected inside intact hydrated cells and organelles

    SciTech Connect

    Szymanski, Craig J.; Munusamy, Prabhakaran; Mihai, Cosmin; Xie, Yumei; Hu, Dehong; Gilles, Marry K.; Tyliszczak, T.; Thevuthasan, Suntharampillai; Baer, Donald R.; Orr, Galya

    2015-09-01

    Cerium oxide nanoparticles (CNPs) have been shown to induce diverse biological effects, ranging from toxic to beneficial. The beneficial effects have been attributed to the potential antioxidant activity of CNPs via certain redox reactions, depending on their oxidation state or Ce3+/Ce4+ ratio. However, this ratio is strongly dependent on the environment and age of the nanoparticles and it is unclear whether and how the complex intracellular environment impacts this ratio and the possible redox reactions of CNPs. To identify any changes in the oxidation state of CNPs in the intracellular environment and better understand their intracellular reactions, we directly quantified the oxidation states of CNPs outside and inside intact hydrated cells and organelles using correlated scanning transmission x-ray and super resolution fluorescence microscopies. By analyzing hundreds of small CNP aggregates, we detected a shift to a higher Ce3+/Ce4+ ratio in CNPs inside versus outside the cells, indicating a net reduction of CNPs in the intracellular environment. We further found a similar ratio in the cytoplasm and in the lysosomes, indicating that the net reduction occurs earlier in the internalization pathway. Together with oxidative stress and toxicity measurements, our observations identify a net reduction of CNPs in the intracellular environment, which is consistent with their involvement in potentially beneficial oxidation reactions, but also point to interactions that can negatively impact the health of cells.

  7. Shifts in oxidation states of cerium oxide nanoparticles detected inside intact hydrated cells and organelles

    PubMed Central

    Szymanski, Craig J.; Munusamy, Prabhakaran; Mihai, Cosmin; Xie, Yumei; Hu, Dehong; Gilles, Mary K.; Tyliszczak, Tolek; Thevuthasan, Suntharampillai; Baer, Donald R.; Orr, Galya

    2015-01-01

    Cerium oxide nanoparticles (CNPs) have been shown to induce diverse biological effects, ranging from toxic to beneficial. The beneficial effects have been attributed to the potential antioxidant activity of CNPs via certain redox reactions, depending on their oxidation state or Ce3+/Ce4+ ratio. However, this ratio is strongly dependent on the environment and age of the nanoparticles and it is unclear whether and how the complex intracellular environment impacts this ratio and the possible redox reactions of CNPs. To identify any changes in the oxidation state of CNPs in the intracellular environment and better understand their intracellular reactions, we directly quantified the oxidation states of CNPs outside and inside intact hydrated cells and organelles using correlated scanning transmission x-ray and super resolution fluorescence microscopies. By analyzing hundreds of small CNP aggregates, we detected a shift to a higher Ce3+/Ce4+ ratio in CNPs inside versus outside the cells, indicating a net reduction of CNPs in the intracellular environment. We further found a similar ratio in the cytoplasm and in the lysosomes, indicating that the net reduction occurs earlier in the internalization pathway. Together with oxidative stress and toxicity measurements, our observations identify a net reduction of CNPs in the intracellular environment, which is consistent with their involvement in potentially beneficial oxidation reactions, but also point to interactions that can negatively impact the health of cells. PMID:26056725

  8. Shifts in oxidation states of cerium oxide nanoparticles detected inside intact hydrated cells and organelles.

    PubMed

    Szymanski, Craig J; Munusamy, Prabhakaran; Mihai, Cosmin; Xie, Yumei; Hu, Dehong; Gilles, Mary K; Tyliszczak, Tolek; Thevuthasan, Suntharampillai; Baer, Donald R; Orr, Galya

    2015-09-01

    Cerium oxide nanoparticles (CNPs) have been shown to induce diverse biological effects, ranging from toxic to beneficial. The beneficial effects have been attributed to the potential antioxidant activity of CNPs via certain redox reactions, depending on their oxidation state or Ce(3+)/Ce(4+) ratio. However, this ratio is strongly dependent on the environment and age of the nanoparticles and it is unclear whether and how the complex intracellular environment impacts this ratio and the possible redox reactions of CNPs. To identify any changes in the oxidation state of CNPs in the intracellular environment and better understand their intracellular reactions, we directly quantified the oxidation states of CNPs outside and inside intact hydrated cells and organelles using correlated scanning transmission x-ray and super resolution fluorescence microscopies. By analyzing hundreds of small CNP aggregates, we detected a shift to a higher Ce(3+)/Ce(4+) ratio in CNPs inside versus outside the cells, indicating a net reduction of CNPs in the intracellular environment. We further found a similar ratio in the cytoplasm and in the lysosomes, indicating that the net reduction occurs earlier in the internalization pathway. Together with oxidative stress and toxicity measurements, our observations identify a net reduction of CNPs in the intracellular environment, which is consistent with their involvement in potentially beneficial oxidation reactions, but also point to interactions that can negatively impact the health of the cells.

  9. Phosphate ester hydrolysis of biologically relevant molecules by cerium oxide nanoparticles.

    PubMed

    Kuchma, Melissa Hirsch; Komanski, Christopher B; Colon, Jimmie; Teblum, Andrew; Masunov, Artëm E; Alvarado, Beatrice; Babu, Suresh; Seal, Sudipta; Summy, Justin; Baker, Cheryl H

    2010-12-01

    In an effort to characterize the interaction of cerium oxide nanoparticles (CNPs) in biological systems, we explored the reactivity of CNPs with the phosphate ester bonds of p-nitrophenylphosphate (pNPP), ATP, o-phospho-l-tyrosine, and DNA. The activity of the bond cleavage for pNPP at pH 7 is calculated to be 0.860 ± 0.010 nmol p-nitrophenol/min/μg CNPs. Interestingly, when CNPs bind to plasmid DNA, no cleavage products are detected. While cerium(IV) complexes generally exhibit the ability to break phosphorus-oxygen bonds, the reactions we report appear to be dependent on the availability of cerium(III) sites, not cerium(IV) sites. We investigated the dephosphorylation mechanism from the first principles and find the reaction proceeds through inversion of the phosphate group similar to an S(N)2 mechanism. The ability of CNPs to interact with phosphate ester bonds of biologically relevant molecules has important implications for their use as potential therapeutics.

  10. Aqueous Co-precipitation of Pd-doped Cerium Oxide Nanoparticles: Chemistry Structure and Particle Growth

    SciTech Connect

    Liang H.; Zhang L.; Raitano J.M.; He G.; Akey A.J.; Herman I.P.; Chan S.-W.

    2012-01-01

    Nanoparticles of palladium-doped cerium oxide (Pd-CeO{sub 2}) have been prepared by aqueous co-precipitation resulting in a single phase cubic structure after calcination according to X-ray diffraction (XRD). Inhomogeneous strain, calculated using the Williamson-Hall method, was found to increase with palladium content, and the lattice contracts slightly, relative to nano-cerium oxide, as palladium content is increased. Moreover, high resolution transmission electron microscopy reveals some instances of defective microstructure. These factors combined imply that palladium is in solid solution with CeO{sub 2} in these nanoparticles, but palladium (II) oxide (PdO) peaks in the Raman spectra indicate that solid solution formation is partial and that highly dispersed PdO is present as well as the solid solution. Nevertheless, the addition of palladium to the CeO{sub 2} lattice inhibits the growth of the 6% Pd-CeO{sub 2} particles compared to pure CeO{sub 2} between 600 and 850 C. Activation energies for grain growth of 54 {+-} 7 and 79 {+-} 8 kJ/mol were determined for 6% Pd-CeO{sub 2} and pure CeO{sub 2}, respectively, along with pre-exponential Arrhenius factors of 10 for the doped sample and 600 for pure cerium oxide.

  11. Cerium Oxide Nanoparticles Reduce Microglial Activation and Neurodegenerative Events in Light Damaged Retina

    PubMed Central

    Fiorani, Lavinia; Passacantando, Maurizio; Santucci, Sandro; Di Marco, Stefano; Bisti, Silvia; Maccarone, Rita

    2015-01-01

    The first target of any therapy for retinal neurodegeneration is to slow down the progression of the disease and to maintain visual function. Cerium oxide or ceria nanoparticles reduce oxidative stress, which is known to play a pivotal role in neurodegeneration. Our aim was to investigate whether cerium oxide nanoparticles were able to mitigate neurodegeneration including microglial activation and related inflammatory processes induced by exposure to high intensity light. Cerium oxide nanoparticles were injected intravitreally or intraveinously in albino Sprague-Dawley rats three weeks before exposing them to light damage of 1000 lux for 24 h. Electroretinographic recordings were performed a week after light damage. The progression of retinal degeneration was evaluated by measuring outer nuclear layer thickness and TUNEL staining to quantify photoreceptors death. Immunohistochemical analysis was used to evaluate retinal stress, neuroinflammatory cytokines and microglial activation. Only intravitreally injected ceria nanoparticles were detected at the level of photoreceptor outer segments 3 weeks after the light damage and electoretinographic recordings showed that ceria nanoparticles maintained visual response. Moreover, this treatment reduced neuronal death and “hot spot” extension preserving the outer nuclear layer morphology. It is noteworthy that in this work we demonstrated, for the first time, the ability of ceria nanoparticles to reduce microglial activation and their migration toward outer nuclear layer. All these evidences support ceria nanoparticles as a powerful therapeutic agent in retinal neurodegenerative processes. PMID:26469804

  12. Cerium Oxide Nanoparticles Reduce Microglial Activation and Neurodegenerative Events in Light Damaged Retina.

    PubMed

    Fiorani, Lavinia; Passacantando, Maurizio; Santucci, Sandro; Di Marco, Stefano; Bisti, Silvia; Maccarone, Rita

    2015-01-01

    The first target of any therapy for retinal neurodegeneration is to slow down the progression of the disease and to maintain visual function. Cerium oxide or ceria nanoparticles reduce oxidative stress, which is known to play a pivotal role in neurodegeneration. Our aim was to investigate whether cerium oxide nanoparticles were able to mitigate neurodegeneration including microglial activation and related inflammatory processes induced by exposure to high intensity light. Cerium oxide nanoparticles were injected intravitreally or intraveinously in albino Sprague-Dawley rats three weeks before exposing them to light damage of 1000 lux for 24 h. Electroretinographic recordings were performed a week after light damage. The progression of retinal degeneration was evaluated by measuring outer nuclear layer thickness and TUNEL staining to quantify photoreceptors death. Immunohistochemical analysis was used to evaluate retinal stress, neuroinflammatory cytokines and microglial activation. Only intravitreally injected ceria nanoparticles were detected at the level of photoreceptor outer segments 3 weeks after the light damage and electoretinographic recordings showed that ceria nanoparticles maintained visual response. Moreover, this treatment reduced neuronal death and "hot spot" extension preserving the outer nuclear layer morphology. It is noteworthy that in this work we demonstrated, for the first time, the ability of ceria nanoparticles to reduce microglial activation and their migration toward outer nuclear layer. All these evidences support ceria nanoparticles as a powerful therapeutic agent in retinal neurodegenerative processes.

  13. Crystallization kinetics of cerium oxide nanoparticles formed by spontaneous, room-temperature hydrolysis of cerium(iv) ammonium nitrate in light and heavy water.

    PubMed

    Pettinger, Natasha W; Williams, Robert E A; Chen, Jinquan; Kohler, Bern

    2017-02-01

    A stable sol of cerium oxide nanoparticles forms spontaneously when cerium(iv) ammonium nitrate (CAN) is dissolved in room-temperature water at mM concentrations. Electron microscopy experiments reveal the formation of highly crystalline cerium oxide particles several nm in diameter and suggest that they are formed from amorphous particles that are similar in size. Under the low pH conditions of the experiments, the nanoparticles form a stable dispersion and show no evidence of aggregation, even many months after synthesis. The absence of particles large enough to scatter light significantly makes it possible to observe the crystallization kinetics through dramatic changes in the UV-visible absorption spectra that occur during solution aging. Measurements show that the cerium oxide nanocrystals are formed roughly an order of magnitude more slowly in D2O than in H2O solution. This large solvent kinetic isotope effect (kH/kD ∼ 10), which is reported here for the first time for the crystallization of a solid metal oxide phase, indicates a rate-determining proton transfer reaction, which is assigned to the conversion of hydroxy to oxo bridges. In D2O solution, the absorption per mole of cerium ions increases by over 400% at 290 nm as the weakly absorbing precursor phase is transformed into nanocrystalline cerium oxide. An isosbestic point is detected at 368 nm, and the absorption spectra can be modeled throughout aging by the sum of spectra of just two interconverting species. Preliminary ultrafast transient absorption experiments confirm that the optical properties of the amorphous precursors differ greatly from those of the final, nanocrystalline phase. Crystallization of CeO2 from CAN in water has much in common with the crystallization of iron oxides from iron(iii) salts, including the importance of non-classical nucleation and growth pathways. It is an outstanding system for studying the poorly understood events that cause molecularly solvated ions to self

  14. High temperature stability of a 316 austenitic stainless steel coated with cerium oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Mendoza Del Angel, Humberto

    Cerium oxide (CeO2-x) nanoparticles were used for coating protection on a 316 Austenitic Stainless Steel (Aust. SS) to enhance the thermal stability of the oxide films formed at high temperatures. Three simple coating methods were used, dipping, spraying and spinning in order to explore the coating film morphology, nanoparticle distribution and its effect on thermal stability of the steel substrates. Experimentally, the selected steel was exposed to 800°C/1000°C under dry air conditions. Weight changes (DeltaW/A) were monitored as a function of time and the results were compared with uncoated alloys tested under similar conditions. The cerium oxide nanoparticles used on the three methods were synthesized in the laboratory obtaining nanoparticles in the range of 3.5 to 6.2 nanometers. It was found that cerium oxide particle size is affected by temperature. In this case, the activation energy for particle growth was estimated to be around 21,1 kJ/mol. Characterization of the film morphologies before and after oxidation were carried out using Atomic Force Microscopy (AFM), Surface Profilometry, Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). A comparison of the three coating methods was carried out for the particular case of the 316 Aust. SS coupons. In addition, the oxidation kinetics was experimentally investigated for the coated samples. For this purpose thermal gravimetric determinations were made at 800°C, 900°C, and 1000°C and oxidation rate constants were calculated at each temperature.

  15. Cerium and yttrium oxide nanoparticles against lead-induced oxidative stress and apoptosis in rat hippocampus.

    PubMed

    Hosseini, Asieh; Sharifi, Ali Mohammad; Abdollahi, Mohammad; Najafi, Rezvan; Baeeri, Maryam; Rayegan, Samira; Cheshmehnour, Jamshid; Hassani, Shokoufeh; Bayrami, Zahra; Safa, Majid

    2015-03-01

    Due to numerous industrial applications, lead has caused widespread pollution in the environment; it seems that the central nervous system (CNS) is the main target for lead in the human body. Oxidative stress and programmed cell death in the CNS have been assumed as two mechanisms related to neurotoxicity of lead. Cerium oxide (CeO2) and yttrium oxide (Y2O3) nanoparticles have recently shown antioxidant effects, particularly when used together, through scavenging the amount of reactive oxygen species (ROS) required for cell apoptosis. We looked into the neuroprotective effects of the combinations of these nanoparticles against acute lead-induced neurotoxicity in rat hippocampus. We used five groups in this study: control, lead, CeO2 nanoparticles + lead, Y2O3 nanoparticles + lead, and CeO2 and Y2O3 nanoparticles + lead. Nanoparticles of CeO2 (1000 mg/kg) and Y2O3 (230 mg/kg) were administered intraperitoneally during 2 days prior to intraperitoneal injection of the lead (25 mg/kg for 3 days). At the end of the treatments, oxidative stress markers, antioxidant enzymes activity, and apoptosis indexes were investigated. The results demonstrated that pretreatments with CeO2 and/or Y2O3 nanoparticles recovered lead-caused oxidative stress markers (ROS, lipid peroxidation, and total thiol molecules) and apoptosis indexes (Bax/Bcl-2 and caspase-3 protein expression). Besides, these nanoparticles reduced the activities of lead-induced superoxide dismutase and catalase as well as the ADP/ATP ratio. Interestingly, the best recovery resulted from the compound of these nanoparticles. Based on these outcomes, it appears that this combination may potentially be beneficial for protection against lead-caused acute toxicity in the brain through improving the oxidative stress-mediated programmed cell death pathway.

  16. Oxidation behaviour and electrical properties of cobalt/cerium oxide composite coatings for solid oxide fuel cell interconnects

    NASA Astrophysics Data System (ADS)

    Harthøj, Anders; Holt, Tobias; Møller, Per

    2015-05-01

    This work evaluates the performance of cobalt/cerium oxide (Co/CeO2) composite coatings and pure Co coatings to be used for solid oxide fuel cell (SOFC) interconnects. The coatings are electroplated on the ferritic stainless steels Crofer 22 APU and Crofer 22H. Coated and uncoated samples are exposed in air at 800 °C for 3000 h and oxidation rates are measured and oxide scale microstructures are investigated. Area-specific resistances (ASR) in air at 850 °C of coated and uncoated samples are also measured. A dual layered oxide scale formed on all coated samples. The outer layer consisted of Co, Mn, Fe and Cr oxide and the inner layer consisted of Cr oxide. The CeO2 was present as discrete particles in the outer oxide layer after exposure. The Cr oxide layer thicknesses and oxidations rates were significantly reduced for Co/CeO2 coated samples compared to for Co coated and uncoated samples. The ASR of all Crofer 22H samples increased significantly faster than of Crofer 22 APU samples which was likely due to the presence of SiO2 in the oxide/metal interface of Crofer 22H.

  17. Microstructural characteristics of cerium oxide conversion coatings obtained by various aqueous deposition methods

    SciTech Connect

    Johnson, B.Y.; Edington, J.; Williams, A.; O'Keefe, M.J. . E-mail: mjokeefe@umr.edu

    2005-01-15

    Microstructural characteristics of cerium oxide conversion coatings obtained by electrolytic, dip-immersion and spray deposition methods from aqueous solutions were studied by transmission electron microscopy and electron diffraction analysis. The coatings were applied to aluminum alloy 7075-T6 panels and the pretreatment conditions were the same for all coating methods. The results indicated that the as-deposited coatings were all composed of nanocrystalline particles with narrow size distributions. Electron diffraction analysis revealed that the electrolytic and the spray coatings developed the same crystal structure, possibly Ce{sub 7}O{sub 12}, while the dip-immersion coating had a different structure that has not been reported in the literature. After post-treatment in phosphate solution, all three as-deposited coatings were converted to hydrated cerium phosphate.

  18. Modification of solid oxide fuel cell anodes with cerium oxide coatings

    NASA Astrophysics Data System (ADS)

    Tang, Ling

    A priority for research in solid oxide fuel cells (SOFCs) is to develop cells that can maintain adequate performance in sulfur-containing fuel streams. There has been evidence that cerium oxide in the anode or electrolyte is associated with sulfur tolerance of the cell, but the mechanism underlying this effect is not well understood. The objective of the present research is to show that the porous cermet SOFC anodes can be coated with cerium oxide films, so that the cell performance can be evaluated as a function of the anode structure and the microstructure of the film. Three types of anodes---Ni/yttria-stabilized zirconia (YSZ), Ni/gadolinia-doped ceria (GDC), and Ni/GDC with GDC interlayer were infiltrated with an aqueous solution to deposit nanocrystalline ceria films. The cells were then tested in hydrogen/nitrogen fuel containing hydrogen sulfide at levels up to 500 ppm. Modification of the anodes with thiol-terminated and trichlorosilane-terminated surfactants was explored. Different ceria film morphology was achieved for each surface treatment. In the cells that underwent performance testing, the thiol treatment promoted ceria film deposition, while the sulfonate treatment suppressed ceria deposition. Uniform ceria films up to 100 nm thick could be deposited in 48 h. Results on cell testing conditions, e.g. current, time, and H2S exposure were related to different anode structures and ceria coating morphologies. In general, the Ni/GDC anodes showed better performance than the Ni/YSZ anode. The introduction of ceria films often resulted in higher cell current and longer testing time, including operation under H2S exposure. Post-testing characterization revealed that, for some anodes, microstructure changes such as coarsening of Ni in the anode, migration of Ni to the anode surface, and depletion of Ni occurred. These changes in microstructure were irreversible and might account for permanent loss of cell performance. The presence of ceria films delayed these

  19. Redox-active cerium oxide nanoparticles protect human dermal fibroblasts from PQ-induced damage.

    PubMed

    von Montfort, Claudia; Alili, Lirija; Teuber-Hanselmann, Sarah; Brenneisen, Peter

    2015-01-01

    Recently, it has been published that cerium (Ce) oxide nanoparticles (CNP; nanoceria) are able to downregulate tumor invasion in cancer cell lines. Redox-active CNP exhibit both selective pro-oxidative and antioxidative properties, the first being responsible for impairment of tumor growth and invasion. A non-toxic and even protective effect of CNP in human dermal fibroblasts (HDF) has already been observed. However, the effect on important parameters such as cell death, proliferation and redox state of the cells needs further clarification. Here, we present that nanoceria prevent HDF from reactive oxygen species (ROS)-induced cell death and stimulate proliferation due to the antioxidative property of these particles.

  20. Controlling the physics and chemistry of binary and ternary praseodymium and cerium oxide systems.

    PubMed

    Niu, Gang; Zoellner, Marvin Hartwig; Schroeder, Thomas; Schaefer, Andreas; Jhang, Jin-Hao; Zielasek, Volkmar; Bäumer, Marcus; Wilkens, Henrik; Wollschläger, Joachim; Olbrich, Reinhard; Lammers, Christian; Reichling, Michael

    2015-10-14

    Rare earth praseodymium and cerium oxides have attracted intense research interest in the last few decades, due to their intriguing chemical and physical characteristics. An understanding of the correlation between structure and properties, in particular the surface chemistry, is urgently required for their application in microelectronics, catalysis, optics and other fields. Such an understanding is, however, hampered by the complexity of rare earth oxide materials and experimental methods for their characterisation. Here, we report recent progress in studying high-quality, single crystalline, praseodymium and cerium oxide films as well as ternary alloys grown on Si(111) substrates. Using these well-defined systems and based on a systematic multi-technique surface science approach, the corresponding physical and chemical properties, such as the surface structure, the surface morphology, the bulk-surface interaction and the oxygen storage/release capability, are explored in detail. We show that specifically the crystalline structure and the oxygen stoichiometry of the oxide thin films can be well controlled by the film preparation method. This work leads to a comprehensive understanding of the properties of rare earth oxides and highlights the applications of these versatile materials. Furthermore, methanol adsorption studies are performed on binary and ternary rare earth oxide thin films, demonstrating the feasibility of employing such systems for model catalytic studies. Specifically for ceria systems, we find considerable stability against normal environmental conditions so that they can be considered as a "materials bridge" between surface science models and real catalysts.

  1. The effect of lanthanum(III) and cerium(III) ions between layers of manganese oxide on water oxidation.

    PubMed

    Najafpour, Mohammad Mahdi; Isaloo, Mohsen Abbasi; Hołyńska, Małgorzata; Shen, Jian-Ren; Allakhverdiev, Suleyman I; Allakhverdiev, Suleyman

    2015-12-01

    Manganese oxide structure with lanthanum(III) or cerium(III) ions between the layers was synthesized by a simple method. The ratio of Mn to Ce or La in samples was 0.00, 0.04, 0.08, 0.16, 0.32, 0.5, 0.82, or 1.62. The compounds were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction studies, and atomic absorption spectroscopy. The compounds show efficient catalytic activity of water oxidation in the presence of cerium(IV) ammonium nitrate with a turnover frequency of 1.6 mmol O2/mol Mn.s. In contrast to the water-oxidizing complex in Photosystem II, calcium(II) has no specific role to enhance the water-oxidizing activity of the layered manganese oxides and other cations can be replaced without any significant decrease in water-oxidizing activities of these layered Mn oxides. Based on this and previously reported results from oxygen evolution in the presence of H 2 (18) O, we discuss the mechanism and the important factors influencing the water-oxidizing activities of the manganese oxides.

  2. Cerium oxide nanoparticles induce oxidative stress in the sediment-dwelling amphipod Corophium volutator.

    PubMed

    Dogra, Yuktee; Arkill, Kenton P; Elgy, Christine; Stolpe, Bjorn; Lead, Jamie; Valsami-Jones, Eugenia; Tyler, Charles R; Galloway, Tamara S

    2016-01-01

    Cerium oxide nanoparticles (CeO2 NPs) exhibit fast valence exchange between Ce(IV) and Ce(III) associated with oxygen storage and both pro and antioxidant activities have been reported in laboratory models. The reactivity of CeO2 NPs once they are released into the aquatic environment is virtually unknown, but this is important to determine for assessing their environmental risk. Here, we show that amphipods (Corophium volutator) grown in marine sediments containing CeO2 NPs showed a significant increase in oxidative damage compared to those grown in sediments without NPs and those containing large-sized (bulk) CeO2 particles. There was no exposure effect on survival, but significant increases in single-strand DNA breaks, lipid peroxidation and superoxide dismutase activity were observed after a 10-day exposure to 12.5 mg L(-1) CeO2. Characterisation of the CeO2 NPs dispersed in deionised or saline exposure waters revealed that more radicals were produced by CeO2 NPs compared with bulk CeO2. Electron energy loss spectroscopy (EELS) analysis revealed that both CeO2 NPs were predominantly Ce(III) in saline waters compared to deionised waters where they were predominantly Ce(IV). In both types of medium, the bulk CeO2 consisted mainly of Ce(IV). These results support a model whereby redox cycling of CeO2 NPs between Ce(III) and Ce(IV) is enhanced in saline waters, leading to sublethal oxidative damage to tissues in our test organism.

  3. Cerium oxide nanoparticles protect primary mouse bone marrow stromal cells from apoptosis induced by oxidative stress

    NASA Astrophysics Data System (ADS)

    Zhang, Qun; Ge, Kun; Duan, Jianlei; Chen, Shizhu; Zhang, Ran; Zhang, Cuimiao; Wang, Shuxiang; Zhang, Jinchao

    2014-11-01

    Cerium oxide nanoparticles (nanoceria) have been widely used in industries and biomedical fields due to its unique properties. Previous biodistribution studies of nanoceria in vivo have shown that they are accumulated in the bone of mice after intravenous administration, about 20 % of the total intake, however, the potential effect and the mechanism of nanoceria on bone metabolism are not well-understood. Our results showed that both 25 and 50 nm nanceria decreased the damage of cell viability induced by H2O2 in a dose-dependent manner. The apoptosis ratio of pre-incubated group with nanoceria was lower than the H2O2 group. The cellular uptake studies indicated that there was a dose-dependent accumulation of both two size nanoparticles in bone marrow stromal cells. Nanoceria could be uptaken by cells due to the synergistic effect of multiple endocytosis mechanisms, and then evenly distributed in the cytoplasm without entering the nucleus. Our results suggest that nanoceria could reduce intracellular ROS level induced by H2O2 in a dose-dependent manner, moreover, maintain the normal function of mitochondria, suggesting nanoceria may have potent applications for preventing or treating osteoporosis.

  4. Cerium Oxide Nanoparticles Induce Oxidative Stress and Genotoxicity in Human Skin Melanoma Cells.

    PubMed

    Ali, Daoud; Alarifi, Saud; Alkahtani, Saad; AlKahtane, Abdullah A; Almalik, Abdulaziz

    2015-04-01

    Extensive applications of cerium oxide (CeO2) nanoparticles require a better understanding of their possible effects on human health. However, data demonstrating the effect of CeO2 nanoparticles on the human skin melanoma cell remain scanty. In the current study, we determined the mechanism through which CeO2 nanoparticles (APS <25 nm) induce toxicity in human skin melanoma cells (A375). The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] and neutral red uptake assays showed concentration and time-dependent cytotoxicity of CeO2 nanoparticles in A375 cells. CeO2 nanoparticles significantly induced the generation reactive oxygen species (ROS) and malondialdehyde, superoxide dismutase, and decreased glutathione levels in A375 cells. It was also observed that the CeO2 nanoparticles induced chromosomal condensation and caspase-3 activity. CeO2 nanoparticles exposed cells revealed the formation of DNA double-strand breakage as measured by percent tail DNA and olive tail moment through comet assay. The decline of cell viability, production of ROS, and DNA damage in A375 cells specifies that CeO2 nanoparticles have less capable to induce cyto and genotoxicity.

  5. Effects of Engineered Cerium Oxide Nanoparticles on Bacterial Growth and Viability▿†

    PubMed Central

    Pelletier, Dale A.; Suresh, Anil K.; Holton, Gregory A.; McKeown, Catherine K.; Wang, Wei; Gu, Baohua; Mortensen, Ninell P.; Allison, David P.; Joy, David C.; Allison, Martin R.; Brown, Steven D.; Phelps, Tommy J.; Doktycz, Mitchel J.

    2010-01-01

    Interest in engineered nanostructures has risen in recent years due to their use in energy conservation strategies and biomedicine. To ensure prudent development and use of nanomaterials, the fate and effects of such engineered structures on the environment should be understood. Interactions of nanomaterials with environmental microorganisms are inevitable, but the general consequences of such interactions remain unclear, due to a lack of standard methods for assessing such interactions. Therefore, we have initiated a multianalytical approach to understand the interactions of synthesized nanoparticles with bacterial systems. These efforts are focused initially on cerium oxide nanoparticles and model bacteria in order to evaluate characterization procedures and the possible fate of such materials in the environment. The growth and viability of the Gram-negative species Escherichia coli and Shewanella oneidensis, a metal-reducing bacterium, and the Gram-positive species Bacillus subtilis were examined relative to cerium oxide particle size, growth media, pH, and dosage. A hydrothermal synthesis approach was used to prepare cerium oxide nanoparticles of defined sizes in order to eliminate complications originating from the use of organic solvents and surfactants. Bactericidal effects were determined from MIC and CFU measurements, disk diffusion tests, and live/dead assays. For E. coli and B. subtilis, clear strain- and size-dependent inhibition was observed, whereas S. oneidensis appeared to be unaffected by the particles. Transmission electron microscopy along with microarray-based transcriptional profiling was used to understand the response mechanism of the bacteria. Use of multiple analytical approaches adds confidence to toxicity assessments, while the use of different bacterial systems highlights the potential wide-ranging effects of nanomaterial interactions in the environment. PMID:20952651

  6. Silicate-free growth of high-quality ultrathin cerium oxide films on Si(111)

    SciTech Connect

    Flege, Jan Ingo; Kaemena, Bjoern; Wilkens, Torsten; Schmidt, Thomas; Falta, Jens; Gevers, Sebastian; Bruns, Daniel; Wollschlaeger, Joachim; Bertram, Florian; Baetjer, Jan

    2011-12-15

    Ultrathin Ce{sub 2}O{sub 3} layers have been grown on Si(111) by reactive metal deposition in an oxygen background and characterized by x-ray standing waves, x-ray diffraction, x-ray photoelectron spectroscopy, and low-energy electron diffraction to elucidate and quantify both atomic structure and chemical composition. It is demonstrated that highly ordered, mostly B-oriented, epitaxial ceria films can be achieved by preadsorption of a monolayer of atomic chlorine, effectively passivating the substrate and thereby suppressing cerium silicate and silicon oxide formation at the interface.

  7. Fabrication of condensate microdrop self-propelling porous films of cerium oxide nanoparticles on copper surfaces.

    PubMed

    Luo, Yuting; Li, Juan; Zhu, Jie; Zhao, Ye; Gao, Xuefeng

    2015-04-13

    Condensate microdrop self-propelling (CMDSP) surfaces have attracted intensive interest. However, it is still challenging to form metal-based CMDSP surfaces. We design and fabricate a type of copper-based CMDSP porous nanoparticle film. An electrodeposition method based on control over the preferential crystal growth of isotropic nanoparticles and synergistic utilization of tiny hydrogen bubbles as pore-making templates is adopted for the in situ growth of cerium oxide porous nanoparticle films on copper surfaces. After characterizing their microscopic morphology, crystal structure and surface chemistry, we explore their CMDSP properties. The nanostructure can realize the efficient ejection of condensate microdrops with sizes below 50 μm.

  8. Anti-reflection coating of Cerium oxide on a plastic substrate

    NASA Astrophysics Data System (ADS)

    Kang, Hyunil; Choi, Wonseok; Kim, Doyoung

    2015-01-01

    Cerium oxide (CeO2) films are suitable for use as anti-reflective coatings for display panels, touch screens, and silicon solar cells. The CeO2 films grown by using a reactive radio frequency sputtering method under various deposition conditions was investigated. The CeO2 films were deposited at room temperature because the plastic substrate was too weak for use at higher temperatures. The films exhibited a strong (111) preferred orientation with properties varying as a function of the process conditions. We present the properties of CeO2 anti-reflective coatings on plastic substrates.

  9. Negative cerium anomalies in manganese (hydr)oxide precipitates due to cerium oxidation in the presence of dissolved siderophores

    NASA Astrophysics Data System (ADS)

    Kraemer, Dennis; Tepe, Nathalie; Pourret, Olivier; Bau, Michael

    2017-01-01

    We present experimental results on the sorption behavior of rare earth elements and yttrium (REY) on precipitating manganese (hydr)oxide in the presence of the biogenic siderophore desferrioxamine B (DFOB). In marked contrast to inorganic systems, where preferential adsorption of HREY and depletion of LREY is commonly observed in manganese (hydr)oxide precipitates, sorption of REY in presence of the DFOB siderophore leads to HREY-depleted and LREY-enriched patterns in the precipitates. Moreover, our data indicate that surface oxidation of Ce(III) to Ce(IV) during sorption onto manganese (hydr)oxides and the resulting development of a positive Ce anomaly, which are commonly observed in inorganic experiments, are prevented in the presence of DFOB. Instead, Ce(III) is oxidized to Ce(IV) but associated with the dissolved desferrioxamine B which forms complexes with Ce(IV), that are at least twenty orders of magnitude more stable than those with Ce(III) and REY(III). The overall result is the formation of a positive Ce anomaly in the solution and a negative Ce anomaly in the Mn (hydr)oxides. The distribution of the strictly trivalent REY and Eu(III) between the manganese (hydr)oxide phase and the remaining ambient solution mimics the distribution of published stability constants for complexes of REY(III) with DFOB, i.e. the heavy REY form more stable complexes with the ligand and hence are better shielded from sorption than the LREY. Surface complexation modeling corroborates our experimental results. Negative Ce anomalies in Mn precipitates have been described from biogenic Mn oxides. Our results provide experimental evidence for the development of negative Ce anomalies in abiogenic Mn (hydr)oxide precipitates and show that the presence of the widespread siderophore desferrioxamine B during mineral precipitation results in HREY-depleted Mn (hydr)oxides with negative Ce anomalies.

  10. An emulsifier-free RAFT-mediated process for the efficient synthesis of cerium oxide/polymer hybrid latexes.

    PubMed

    Garnier, Jérôme; Warnant, Jérôme; Lacroix-Desmazes, Patrick; Dufils, Pierre-Emmanuel; Vinas, Jérôme; Vanderveken, Yves; van Herk, Alex M

    2012-08-28

    Hybrid latexes based on cerium oxide nanoparticles are synthesized via an emulsifier-free process of emulsion polymerization employing amphiphatic macro-RAFT agents. Poly(butyl acrylate-co-acrylic acid) random oligomers of various compositions and chain lengths are first obtained by RAFT copolymerization in the presence of a trithiocarbonate as controlling agent. In a second step, the seeded emulsion copolymerization of styrene and methyl acrylate is carried out in the presence of nanoceria with macro-RAFT agents adsorbed at their surface, resulting in a high incorporation efficiency of cerium oxide nanoparticles in the final hybrid latexes, as evidenced by cryo-transmission electron microscopy.

  11. The evolution mechanism of the dislocation loops in irradiated lanthanum doped cerium oxide

    NASA Astrophysics Data System (ADS)

    Miao, Yinbin; Aidhy, Dilpuneet; Chen, Wei-Ying; Mo, Kun; Oaks, Aaron; Wolf, Dieter; Stubbins, James F.

    2014-02-01

    Cerium dioxide, a non-radioactive surrogate of uranium dioxide, is useful for simulating the radiation responses of uranium dioxide and mixed oxide fuel (MOX). Controlled additions of lanthanum can also be used to form various levels of lattice oxide or anion vacancies. In previous transmission electron microscopy (TEM) experimental studies, the growth rate of dislocation loops in irradiated lanthanum doped ceria was reported to vary with lanthanum concentration. This work reports findings of the evolution mechanisms of the dislocation loops in cerium oxide with and without lanthanum dopants based on a combination of molecular statics and molecular dynamics simulations. These dislocation loops are found to be b = 1 / 3 < 1 1 1 > interstitial type Frank loops. Calculations of the defect energy profiles of the dislocation loops with different structural configurations and radii reveal the basis for preference of nucleation as well as the driving force of growth. Frenkel pair evolution simulations and displacement cascade overlaps simulations were conducted for a variety of lanthanum doping conditions. The nucleation and growth processes of the Frank loop were found to be controlled by the mobility of cation interstitials, which is significantly influenced by the lanthanum doping concentration. Competition mechanisms coupled with the mobility of cation point defects were discovered, and can be used to explain the lanthanum effects observed in experiments.

  12. Determination of Ideal Broth Formulations Needed to Prepare Hydrous Cerium Oxide Microspheres via the Internal Gelation Process

    SciTech Connect

    Collins, Jack Lee; Chi, Anthony

    2009-02-01

    A simple test tube methodology was used to determine optimum process parameters for preparing hydrous cerium oxide microspheres via the internal gelation process.1 Broth formulations of cerium ammonium nitrate [(NH4)2Ce(NO3)6], hexamethylenetetramine, and urea were found that can be used to prepare hydrous cerium oxide gel spheres in the temperature range of 60 to 90 C. A few gel-forming runs were made in which microspheres were prepared with some of these formulations to be able to equate the test-tube gelation times to actual gelation times. These preparations confirmed that the test-tube methodology is reliable for determining the ideal broth formulations.

  13. Oxidative modification of native protein residues using cerium(IV) ammonium nitrate.

    PubMed

    Seim, Kristen L; Obermeyer, Allie C; Francis, Matthew B

    2011-10-26

    A new protein modification strategy has been developed that is based on an oxidative coupling reaction that targets electron-rich amino acids. This strategy relies on cerium(IV) ammonium nitrate (CAN) as an oxidation reagent and results in the coupling of tyrosine and tryptophan residues to phenylene diamine and anisidine derivatives. The methodology was first identified and characterized on peptides and small molecules, and was subsequently adapted for protein modification by determining appropriate buffer conditions. Using the optimized procedure, native and introduced solvent-accessible residues on proteins were selectively modified with polyethylene glycol (PEG) and small peptides. This unprecedented bioconjugation strategy targets these under-utilized amino acids with excellent chemoselectivity and affords good-to-high yields using low concentrations of the oxidant and coupling partners, short reaction times, and mild conditions.

  14. Porous microspheres of manganese-cerium mixed oxides by a polyvinylpyrrolidone assisted solvothermal method

    NASA Astrophysics Data System (ADS)

    Schmit, F.; Bois, L.; Chiriac, R.; Toche, F.; Chassagneux, F.; Descorme, C.; Besson, M.; Khrouz, L.

    2017-04-01

    Mixed cerium manganese oxides were synthesized using a polyvinylpyrrolidone (PVP) assisted solvothermal method. Materials obtained after calcination at 400 °C were characterized by X-ray diffraction, scanning and transmission electron microscopies, electron paramagnetic resonance (EPR), Raman spectroscopy, thermal analysis and nitrogen adsorption/desorption isotherms. The influence of the synthesis parameters on the oxide structure, such as the Mn:Ce ratio or the amount of PVP, was discussed. Micrometric spheres of mixed Mn-Ce oxides, resulting from the aggregation of 100 nm porous snowflakes, were successfully synthesized. These snowflakes were formed from the aggregation of smaller oriented crystallites (size 4 nm). The hydrothermal stability of these materials was also investigated.

  15. Cerium oxide-chitosan based nanobiocomposite for food borne mycotoxin detection

    NASA Astrophysics Data System (ADS)

    Kaushik, Ajeet; Solanki, Pratima R.; Pandey, M. K.; Ahmad, Sharif; Malhotra, Bansi D.

    2009-10-01

    Cerium oxide nanoparticles (NanoCeO2) and chitosan (CH) based nanobiocomposite film deposited onto indium-tin-oxide coated glass substrate has been used to coimmobilize rabbit immunoglobin (r-IgGs) and bovine serum albumin (BSA) for food borne mycotoxin [ochratoxin-A (OTA)] detection. Electrochemical studies reveal that presence of NanoCeO2 increases effective electro-active surface area of CH-NanoCeO2/indium tin oxide (ITO) nanobiocomposite resulting in high loading of r-IgGs. BSA/r-IgGs/CH-NanoCeO2/ITO immunoelectrode exhibits improved linearity (0.25-6.0 ng/dl), detection limit (0.25 ng/dl), response time (25 s), sensitivity (18 μA/ng dl-1 cm-2), and regression coefficient (r2˜0.997).

  16. Titanium-doped cerium oxide nanoparticles protect cells from hydrogen peroxide-induced apoptosis

    PubMed Central

    Clark, Andrea; Zhu, Aiping; Petty, Howard R.

    2014-01-01

    To develop new nanoparticle materials possessing anti-oxidative capacity with improved physical characteristics, we have studied titanium-doped cerium oxide (CeTiO2) nanoparticles. CeTiO2 nanoparticles had a mode diameter of 15-20 nm. These nanoparticles demonstrated catalase activity, and did not promote the activation of hemolytic or cytolytic pathways in living cells. Using surface plasmon resonance enhanced microscopy, we find that these nanoparticles associate with cells. Transmission electron microscopy studies demonstrated that these nanoparticles accumulate within the vacuolar compartment of cells. Importantly, CeTiO2 nanoparticles decrease hydrogen peroxide-mediated apoptosis of cells as judged by the reduced cleavage of a caspase 3-sensitive label. CeTiO2 nanoparticles may contribute to deflecting tissue damage in a broad spectrum of oxidant-mediated diseases, such as macular degeneration and Alzheimer's disease. PMID:24791147

  17. Phenotypic and genomic responses to titanium dioxide and cerium oxide nanoparticles in Arabidopsis germinants.

    PubMed

    Tumburu, Laxminath; Andersen, Christian P; Rygiewicz, Paul T; Reichman, Jay R

    2015-01-01

    The effects of exposure to nanoparticles of titanium dioxide (nano-titanium) and cerium oxide (nano-cerium) on gene expression and growth in Arabidopsis thaliana germinants were studied by using microarrays and quantitative real-time polymerase chain reaction (qPCR), and by evaluating germinant phenotypic plasticity. Exposure to 12 d of either nano-titania or nano-ceria altered the regulation of 204 and 142 genes, respectively. Genes induced by the nanoparticles mainly include ontology groups annotated as stimuli responsive, including both abiotic (oxidative stress, salt stress, water transport) and biotic (respiratory burst as a defense against pathogens) stimuli. Further analysis of the differentially expressed genes indicates that both nanoparticles affected a range of metabolic processes (deoxyribonucleic acid [DNA] metabolism, hormone metabolism, tetrapyrrole synthesis, and photosynthesis). Individual exposures to the nanoparticles increased percentages of seeds with emergent radicles, early development of hypocotyls and cotyledons, and those with fully grown leaves. Although there were distinct differences between the nanoparticles in their affect on molecular mechanisms attributable to enhancing germinant growth, both particles altered similar suites of genes related to various pathways and processes related to enhanced growth.

  18. Cerium oxide nanoparticles stimulate proliferation of primary mouse embryonic fibroblasts in vitro.

    PubMed

    Popov, Anton L; Popova, Nelly R; Selezneva, Irina I; Akkizov, Azamat Y; Ivanov, Vladimir K

    2016-11-01

    The increasing application of cell therapy technologies in the treatment of various diseases requires the development of new effective methods for culturing primary cells. The major limitation for the efficient use of autologous cell material is the low rate of cell proliferation. Successful cell therapy requires sufficient amounts of cell material over a short period of time with the preservation of their differentiation and proliferative potential. In this regard, the development of novel, highly efficient stimulators of proliferative activity in stem cells is a truly urgent task. In this paper we have demonstrated that citrate-stabilized cerium oxide nanoparticles (nanoceria) enhance the proliferative activity of primary mouse embryonic fibroblasts in vitro. Cerium oxide nanoparticles stimulate cell proliferation in a wide range of concentrations (10(-3)М-10(-9)M) through reduction of intracellular levels of reactive oxygen species (ROS) during the lag phase of cell growth and by modulating the expression level of the major antioxidant enzymes. We found the optimal concentration of nanoceria, which provides the greatest acceleration of cell proliferation in vitro, while maintaining the levels of intracellular ROS and mRNA of antioxidant enzymes in the physiological range. Our results confirm that nanocrystalline ceria can be considered as a basis for effective and inexpensive supplements in cell culturing.

  19. Low Temperature Constrained Sintering of Cerium Gadolinium OxideFilms for Solid Oxide Fuel Cell Applications

    SciTech Connect

    Nicholas, Jason Dale

    2007-01-01

    Cerium gadolinium oxide (CGO) has been identified as an acceptable solid oxide fuel cell (SOFC) electrolyte at temperatures (500-700 C) where cheap, rigid, stainless steel interconnect substrates can be used. Unfortunately, both the high sintering temperature of pure CGO, >1200 C, and the fact that constraint during sintering often results in cracked, low density ceramic films, have complicated development of metal supported CGO SOFCs. The aim of this work was to find new sintering aids for Ce0.9Gd0.1O1.95, and to evaluate whether they could be used to produce dense, constrained Ce0.9Gd0.1O1.95 films at temperatures below 1000 C. To find the optimal sintering aid, Ce0.9Gd0.1O1.95 was doped with a variety of elements, of which lithium was found to be the most effective. Dilatometric studies indicated that by doping CGO with 3mol% lithium nitrate, it was possible to sinter pellets to a relative density of 98.5% at 800 C--a full one hundred degrees below the previous low temperature sintering record for CGO. Further, it was also found that a sintering aid's effectiveness could be explained in terms of its size, charge and high temperature mobility. A closer examination of lithium doped Ce0.9Gd0.1O1.95 indicated that lithium affects sintering by producing a Li2O-Gd2O3-CeO2 liquid at the CGO grain boundaries. Due to this liquid phase sintering, it was possible to produce dense, crack-free constrained films of CGO at the record low temperature of 950 C using cheap, colloidal spray deposition processes. This is the first time dense constrained CGO films have been produced below 1000 C and could help commercialize metal supported ceria based solid oxide fuel cells.

  20. Inhaled diesel emissions generated with cerium oxide nanoparticle fuel additive induce adverse pulmonary and systemic effects.

    PubMed

    Snow, Samantha J; McGee, John; Miller, Desinia B; Bass, Virginia; Schladweiler, Mette C; Thomas, Ronald F; Krantz, Todd; King, Charly; Ledbetter, Allen D; Richards, Judy; Weinstein, Jason P; Conner, Teri; Willis, Robert; Linak, William P; Nash, David; Wood, Charles E; Elmore, Susan A; Morrison, James P; Johnson, Crystal L; Gilmour, Matthew Ian; Kodavanti, Urmila P

    2014-12-01

    Diesel exhaust (DE) exposure induces adverse cardiopulmonary effects. Cerium oxide nanoparticles added to diesel fuel (DECe) increases fuel burning efficiency but leads to altered emission characteristics and potentially altered health effects. Here, we evaluated whether DECe results in greater adverse pulmonary effects compared with DE. Male Sprague Dawley rats were exposed to filtered air, DE, or DECe for 5 h/day for 2 days. N-acetyl glucosaminidase activity was increased in bronchial alveolar lavage fluid (BALF) of rats exposed to DECe but not DE. There were also marginal but insignificant increases in several other lung injury biomarkers in both exposure groups (DECe > DE for all). To further characterize DECe toxicity, rats in a second study were exposed to filtered air or DECe for 5 h/day for 2 days or 4 weeks. Tissue analysis indicated a concentration- and time-dependent accumulation of lung and liver cerium followed by a delayed clearance. The gas-phase and high concentration of DECe increased lung inflammation at the 2-day time point, indicating that gas-phase components, in addition to particles, contribute to pulmonary toxicity. This effect was reduced at 4 weeks except for a sustained increase in BALF γ-glutamyl transferase activity. Histopathology and transmission electron microscopy revealed increased alveolar septa thickness due to edema and increased numbers of pigmented macrophages after DECe exposure. Collectively, these findings indicate that DECe induces more adverse pulmonary effects on a mass basis than DE. In addition, lung accumulation of cerium, systemic translocation to the liver, and delayed clearance are added concerns to existing health effects of DECe.

  1. Inhaled Diesel Emissions Generated with Cerium Oxide Nanoparticle Fuel Additive Induce Adverse Pulmonary and Systemic Effects

    PubMed Central

    Snow, Samantha J.; McGee, John; Miller, Desinia B.; Bass, Virginia; Schladweiler, Mette C.; Thomas, Ronald F.; Krantz, Todd; King, Charly; Ledbetter, Allen D.; Richards, Judy; Weinstein, Jason P.; Conner, Teri; Willis, Robert; Linak, William P.; Nash, David; Wood, Charles E.; Elmore, Susan A.; Morrison, James P.; Johnson, Crystal L.; Gilmour, Matthew Ian; Kodavanti, Urmila P.

    2014-01-01

    Diesel exhaust (DE) exposure induces adverse cardiopulmonary effects. Cerium oxide nanoparticles added to diesel fuel (DECe) increases fuel burning efficiency but leads to altered emission characteristics and potentially altered health effects. Here, we evaluated whether DECe results in greater adverse pulmonary effects compared with DE. Male Sprague Dawley rats were exposed to filtered air, DE, or DECe for 5 h/day for 2 days. N-acetyl glucosaminidase activity was increased in bronchial alveolar lavage fluid (BALF) of rats exposed to DECe but not DE. There were also marginal but insignificant increases in several other lung injury biomarkers in both exposure groups (DECe > DE for all). To further characterize DECe toxicity, rats in a second study were exposed to filtered air or DECe for 5 h/day for 2 days or 4 weeks. Tissue analysis indicated a concentration- and time-dependent accumulation of lung and liver cerium followed by a delayed clearance. The gas-phase and high concentration of DECe increased lung inflammation at the 2-day time point, indicating that gas-phase components, in addition to particles, contribute to pulmonary toxicity. This effect was reduced at 4 weeks except for a sustained increase in BALF γ-glutamyl transferase activity. Histopathology and transmission electron microscopy revealed increased alveolar septa thickness due to edema and increased numbers of pigmented macrophages after DECe exposure. Collectively, these findings indicate that DECe induces more adverse pulmonary effects on a mass basis than DE. In addition, lung accumulation of cerium, systemic translocation to the liver, and delayed clearance are added concerns to existing health effects of DECe. PMID:25239632

  2. Cerium-modified doped strontium titanate compositions for solid oxide fuel cell anodes and electrodes for other electrochemical devices

    DOEpatents

    Marina, Olga A [Richland, WA; Stevenson, Jeffry W [Richland, WA

    2010-11-23

    The present invention provides novel compositions that find advantageous use in making electrodes for electrochemical cells and electrochemical devices such as solid oxide fuel cells, electrolyzers, sensors, pumps and the like, the compositions comprising cerium-modified doped strontium titanate. The invention also provides novel methods for making and using anode material compositions and solid oxide fuel cells and solid oxide fuel cell assemblies having anodes comprising the compositions.

  3. Cerium-modified doped strontium titanate compositions for solid oxide fuel cell anodes and electrodes for other electrochemical devices

    DOEpatents

    Marina, Olga A [Richland, WA; Stevenson, Jeffry W [Richland, WA

    2010-03-02

    The present invention provides novel compositions that find advantageous use in making electrodes for electrochemical cells and electrochemical devices such as solid oxide fuel cells, electrolyzers, sensors, pumps and the like, the compositions comprising cerium-modified doped strontium titanate. The invention also provides novel methods for making and using anode material compositions and solid oxide fuel cells and solid oxide fuel cell assemblies having anodes comprising the compositions.

  4. Germination and early plant development of ten plant species exposed to titanium dioxide and cerium oxide nanoparticles

    EPA Science Inventory

    Ten agronomic plant species were exposed to different concentrations of nano titanium dioxide (nTiO2) or nano cerium oxide (nCeO2) (0, 250, 500 and 1000 mg/L) to examine potential effects on germination and early seedling development. We modified a standard test protocol develop...

  5. Evidence for an oxygen evolving iron-oxo-cerium intermediate in iron-catalysed water oxidation.

    PubMed

    Codolà, Zoel; Gómez, Laura; Kleespies, Scott T; Que, Lawrence; Costas, Miquel; Lloret-Fillol, Julio

    2015-01-22

    The non-haem iron complex α-[Fe(II)(CF3SO3)2(mcp)] (mcp=(N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)-1,2-cis-diaminocyclohexane) reacts with Ce(IV) to oxidize water to O2, representing an iron-based functional model for the oxygen evolving complex of photosystem II. Here we trap an intermediate, characterized by cryospray ionization high resolution mass spectrometry and resonance Raman spectroscopy, and formulated as [(mcp)Fe(IV)(O)(μ-O)Ce(IV)(NO3)3](+), the first example of a well-characterized inner-sphere complex to be formed in cerium(IV)-mediated water oxidation. The identification of this reactive Fe(IV)-O-Ce(IV) adduct may open new pathways to validate mechanistic notions of an analogous Mn(V)-O-Ca(II) unit in the oxygen evolving complex that is responsible for carrying out the key O-O bond forming step.

  6. Titanium-doped cerium oxide nanoparticles protect cells from hydrogen peroxide-induced apoptosis

    NASA Astrophysics Data System (ADS)

    Clark, Andrea; Zhu, Aiping; Petty, Howard R.

    2013-12-01

    To develop new nanoparticle materials possessing antioxidative capacity with improved physical characteristics, we have studied titanium-doped cerium oxide (CeTiO2) nanoparticles. CeTiO2 nanoparticles had mode diameters in the range of 15-20 nm. These nanoparticles demonstrated catalase activity, and did not promote the activation of hemolytic or cytolytic pathways in living cells. Using surface plasmon resonance-enhanced microscopy, we find that these nanoparticles associate with cells. Transmission electron microscopy studies demonstrated that these nanoparticles accumulate within the vacuolar compartment of cells. Importantly, CeTiO2 nanoparticles decrease hydrogen peroxide-mediated apoptosis of cells as judged by the reduced cleavage of a caspase 3-sensitive label. CeTiO2 nanoparticles may contribute to deflecting tissue damage in a broad spectrum of oxidant-mediated diseases, such as macular degeneration and Alzheimer's disease.

  7. Corrosion resistance of flaky aluminum pigment coated with cerium oxides/hydroxides in chloride and acidic electrolytes

    NASA Astrophysics Data System (ADS)

    Niroumandrad, S.; Rostami, M.; Ramezanzadeh, B.

    2015-12-01

    The objective of this study was to enhance the corrosion resistance of lamellar aluminum pigment through surface treatment by cerium oxides/hydroxides. The surface composition of the pigments was studied by energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of the pigment was evaluated by conventional hydrogen evolution measurements in acidic solution and electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution. Results showed that the Ce-rich coating composed of Ce2O3 and CeO2 was precipitated on the pigment surface after immersion in the cerium solution. The corrosion resistance of pigment was significantly enhanced after modification with cerium layer.

  8. Computational and Experimental Study of the Thermodynamics of Uranium-Cerium Mixed Oxides

    NASA Astrophysics Data System (ADS)

    Hanken, Benjamin Edward

    The thermophysical properties of mixed oxide (MOX) fuels, and how they are influenced by the incorporation of fission products and other actinides, must be well understood for their safe use in an advanced fuel cycle. Cerium is a common plutonium surrogate in experimental studies of MOX, as it closely matches plutonium's ionic radii in the 3+ and 4+ oxidation states, and is soluble in fluorite-structured UO2. As a fission product, cerium's effects on properties of MOX are also of practical interest. To provide additional insights on structure-dependent behavior, urania solid solutions can be studied via density functional theory (DFT), although approaches beyond standard DFT are needed to properly account for the localized nature of the ƒ-electrons. In this work, DFT with Hubbard-U corrections (DFT+U) was employed to study the energetics of fluorite-structured U1-yCe yO2 mixtures. The employed computational approach makes use of a procedure which facilitates convergence of the calculations to multiple self-consistent DFT+U solutions for a given cation arrangement, corresponding to different charge states for the U and Ce ions in several prototypical cation arrangements. Results indicate a significant dependence of the structural and energetic properties of U1-yCeyO2 on the nature of both charge and cation ordering. With the effective Hubbard-U parameters that reproduce well the measured oxidation-reduction energies for urania and ceria, it was found that charge transfer between U4+ and Ce4+ ions, leading to the formation of U5+ and Ce3+, gives rise to an increase in the mixing energy in the range of 4-14 kJ/mol of the formula unit, depending on the nature of the cation ordering. In conjunction with the computational approach, high-temperature oxide-melt drop-solution calorimetry experiments were performed on eight samples spanning compositions of y = 0.119 to y = 0.815. Room temperature mixing enthalpies of U1-yCeyO2 determined from these experiments show near

  9. Antioxidation of Cerium Oxide Nanoparticles to Several Series of Oxidative Damage Related to Type II Diabetes Mellitus In Vitro

    PubMed Central

    Zhai, Jing-hui; Wu, Yi; Wang, Xiao-ying; Cao, Yue; Xu, Kan; Xu, Li; Guo, Yi

    2016-01-01

    Background It is well known that cerium oxide nanoparticles (CeNPs) have intense antioxidant activity. The antioxidant property of CeNPs are widely used in different areas of research, but little is known about the oxidative damage of Cu2+ associated with Type II diabetes mellitus (T2DM). Material/Methods In our research, the function of CeNPs was tested for its protection of β-cells from the damage of Cu2+ or H2O2. We detected hydroxyl radicals using terephthalic acid assay, hydrogen peroxide using Amplex Ultra Red assay, and cell viability using MTT reduction. Results We found that CeNPs can persistently inhibit Cu2+/H2O2 evoked hydroxyl radicals and hydrogen peroxide in oxidative stress of β-cells. Conclusions CeNPs will be useful in developing strategies for the prevention of T2DM. PMID:27752033

  10. Freshwater dispersion stability of PAA-stabilised cerium oxide nanoparticles and toxicity towards Pseudokirchneriella subcapitata.

    PubMed

    Booth, Andy; Størseth, Trond; Altin, Dag; Fornara, Andrea; Ahniyaz, Anwar; Jungnickel, Harald; Laux, Peter; Luch, Andreas; Sørensen, Lisbet

    2015-02-01

    An aqueous dispersion of poly (acrylic acid)-stabilised cerium oxide (CeO₂) nanoparticles (PAA-CeO₂) was evaluated for its stability in a range of freshwater ecotoxicity media (MHRW, TG 201 and M7), with and without natural organic matter (NOM). In a 15 day dispersion stability study, PAA-CeO₂ did not undergo significant aggregation in any media type. Zeta potential varied between media types and was influenced by PAA-CeO₂ concentration, but remained constant over 15 days. NOM had no influence on PAA-CeO₂ aggregation or zeta potential. The ecotoxicity of the PAA-CeO₂ dispersion was investigated in 72 h algal growth inhibition tests using the freshwater microalgae Pseudokirchneriella subcapitata. PAA-CeO₂ EC₅₀ values for growth inhibition (GI; 0.024 mg/L) were 2-3 orders of magnitude lower than pristine CeO₂ EC₅₀ values reported in the literature. The concentration of dissolved cerium (Ce(3+)/Ce(4+)) in PAA-CeO₂ exposure suspensions was very low, ranging between 0.5 and 5.6 μg/L. Free PAA concentration in the exposure solutions (0.0096-0.0384 mg/L) was significantly lower than the EC10 growth inhibition (47.7 mg/L) value of pure PAA, indicating that free PAA did not contribute to the observed toxicity. Elemental analysis indicated that up to 38% of the total Cerium becomes directly associated with the algal cells during the 72 h exposure. TOF-SIMS analysis of algal cell wall compounds indicated three different modes of action, including a significant oxidative stress response to PAA-CeO₂ exposure. In contrast to pristine CeO₂ nanoparticles, which rapidly aggregate in standard ecotoxicity media, PAA-stabilised CeO₂ nanoparticles remain dispersed and available to water column species. Interaction of PAA with cell wall components, which could be responsible for the observed biomarker alterations, could not be excluded. This study indicates that the increased dispersion stability of PAA-CeO₂ leads to an increase in toxicity compared to

  11. The induction of angiogenesis by cerium oxide nanoparticles through the modulation of oxygen in intracellular environments

    PubMed Central

    Das, Soumen; Singh, Sanjay; Dowding, Janet M.; Oommen, Saji; Kumar, Amit; Sayle, Thi X. T.; Saraf, Shashank; Patra, Chitta Ranjan; Vlahakis, Nicholas E.; Sayle, Dean C.; Self, William T.; Seal, Sudipta

    2012-01-01

    Angiogenesis is the formation of new blood vessels from existing blood vessels and is critical for many physiological and pathophysiological processes. In this study we have shown the unique property of cerium oxide nanoparticle (CNPs) to induce angiogenesis, observed using both in vitro and in vivo model systems. In particular, CNPs trigger angiogenesis by modulating the intracellular oxygen environment and stabilizing hypoxia inducing factor 1α endogenously. Furthermore, correlations between angiogenesis induction and CNPs physicochemical properties including: surface Ce3+/Ce4+ ratio, surface charge, size, and shape were also explored. High surface area and increased Ce3+/Ce4+ ratio make CNPs more catalytically active towards regulating intracellular oxygen, which in turn led to more robust induction of angiogenesis. Atomistic simulation was also used, in partnership with in vitro and in vivo experimentation, to reveal that the surface reactivity of CNPs and facile oxygen transport promotes pro-angiogenesis. PMID:22858004

  12. Brain suppression of AP-1 by inhaled diesel exhaust and reversal by cerium oxide nanoparticles.

    PubMed

    Lung, Shyang; Cassee, Flemming R; Gosens, Ilse; Campbell, Arezoo

    2014-08-01

    One of the uses of cerium oxide nanoparticles (nanoceria, CeO2) is as a diesel fuel additive to improve fuel efficiency. Gene/environment interactions are important determinants in the etiology of age-related disorders. Thus, it is possible that individuals on high-fat diet and genetic predisposition to vascular disease may be more vulnerable to the adverse health effects of particle exposure. The aim of this pilot study was to test the hypothesis that inhalation of diesel exhaust (DE) or diesel exhaust-containing cerium oxide nanoparticles (DCeE) induces stress in the brain of a susceptible animal model. Atherosclerotic prone, apolipoprotein E knockout (ApoE(-/-)) mice fed a high-fat diet, were exposed by inhalation to purified air (control), DE or DCeE. The stress-responsive transcription factor, activator protein-1 (AP-1), was significantly decreased in the cortical and subcortical fraction of the brain after DE exposure. The addition of nanoceria to the diesel fuel reversed this effect. The activation of another stress-related transcription factor (NF-κB) was not inhibited. AP-1 is composed of complexes of the Jun and/or Fos family of proteins. Exposure to DCeE caused c-Jun activation and this may be a mechanism by which addition of nanoceria to the fuel reversed the effect of DE exposure on AP-1 activation. This pilot study demonstrates that exposure to DE does impact the brain and addition of nanoceria may be protective. However, more extensive studies are necessary to determine how DE induced reduction of AP-1 activity and compensation by nanoceria impacts normal function of the brain.

  13. Destruction of commercial pesticides by cerium redox couple mediated electrochemical oxidation process in continuous feed mode.

    PubMed

    Balaji, Subramanian; Chung, Sang Joon; Ryu, Jae-Yong; Moon, Il Shik

    2009-12-30

    Mediated electrochemical oxidation was carried out for the destruction of commercial pesticide formulations using cerium(IV) in nitric acid as the mediator electrolyte solution in a bench scale set up. The mediator oxidant was regenerated in situ using an electrochemical cell. The real application of this sustainable process for toxic organic pollutant destruction lies in its ability for long term continuous operation with continuous organic feeding and oxidant regeneration with feed water removal. In this report we present the results of fully integrated MEO system. The task of operating the continuous feed MEO system for a long time was made possible by continuously removing the feed water using an evaporator set up. The rate of Ce(IV) regeneration in the electrochemical cell and the consumption for the pesticide destruction was matched based on carbon content of the pesticides. It was found that under the optimized experimental conditions for Ce(III) oxidation, organic addition and water removal destruction efficiency of ca. 99% was obtained for all pesticides studied. It was observed that the Ce(IV) concentration was maintained nearly the same throughout the experiment. The stable operation for 6h proved that the process can be used for real applications and for possible scale up for the destruction of larger volumes of toxic organic wastes.

  14. Catalyst support of mixed cerium zirconium titanium oxide, including use and method of making

    DOEpatents

    Willigan, Rhonda R [Manchester, CT; Vanderspurt, Thomas Henry [Glastonbury, CT; Tulyani, Sonia [Manchester, CT; Radhakrishnan, Rakesh [Vernon, CT; Opalka, Susanne Marie [Glastonbury, CT; Emerson, Sean C [Broad Brook, CT

    2011-01-18

    A durable catalyst support/catalyst is capable of extended water gas shift operation under conditions of high temperature, pressure, and sulfur levels. The support is a homogeneous, nanocrystalline, mixed metal oxide of at least three metals, the first being cerium, the second being Zr, and/or Hf, and the third importantly being Ti, the three metals comprising at least 80% of the metal constituents of the mixed metal oxide and the Ti being present in a range of 5% to 45% by metals-only atomic percent of the mixed metal oxide. The mixed metal oxide has an average crystallite size less than 6 nm and forms a skeletal structure with pores whose diameters are in the range of 4-9 nm and normally greater than the average crystallite size. The surface area of the skeletal structure per volume of the material of the structure is greater than about 240 m.sup.2/cm.sup.3. The method of making and use are also described.

  15. Reaction chemistry of cerium

    SciTech Connect

    1997-01-01

    It is truly ironic that a synthetic organic chemist likely has far greater knowledge of the reaction chemistry of cerium(IV) than an inorganic colleague. Cerium(IV) reagents have long since been employed as oxidants in effecting a wide variety of organic transformations. Conversely, prior to the late 1980s, the number of well characterized cerium(IV) complexes did not extend past a handful of known species. Though in many other areas, interest in the molecular chemistry of the 4f-elements has undergone an explosive growth over the last twenty years, the chemistry of cerium(IV) has for the most part been overlooked. This report describes reactions of cerium complexes and structure.

  16. Potential of using cerium oxide nanoparticles for protecting healthy tissue during accelerated partial breast irradiation (APBI)

    PubMed Central

    Ouyang, Zi; Mainali, Madan Kumar; Sinha, Neeharika; Strack, Guinevere; Altundal, Yucel; Hao, Yao; Winningham, Thomas Andrew; Sajo, Erno; Celli, Jonathan; Ngwa, Wilfred

    2016-01-01

    The purpose of this study is to investigate the feasibility of using cerium oxide nanoparticles (CONPs) as radical scavengers during accelerated partial breast irradiation (APBI) to protect normal tissue. We hypothesize that CONPs can be slowly released from the routinely used APBI balloon applicators—via a degradable coating—and protect the normal tissue on the border of the lumpectomy cavity over the duration of APBI. To assess the feasibility of this approach, we analytically calculated the initial concentration of CONPs required to protect normal breast tissue from reactive oxygen species (ROS) and the time required for the particles to diffuse to various distances from the lumpectomy wall. Given that cerium has a high atomic number, we took into account the possible inadvertent dose enhancement that could occur due to the photoelectric interactions with radiotherapy photons. To protect against a typical MammoSite treatment fraction of 3.4 Gy, 5 ng-g−1 of CONPs is required to scavenge hydroxyl radicals and hydrogen peroxide. Using 2 nm sized NPs, with an initial concentration of 1 mg-g−1, we found that 2–10 days of diffusion is required to obtain desired concentrations of CONPs in regions 1–2 cm away from the lumpectomy wall. The resultant dose enhancement factor (DEF) is less than 1.01 under such conditions. Our results predict that CONPs can be employed for radioprotection during APBI using a new design in which balloon applicators are coated with the NPs for sustained/controlled in-situ release from within the lumpectomy cavity. PMID:27053452

  17. Interactive effects of cerium oxide and diesel exhaust nanoparticles on inducing pulmonary fibrosis.

    PubMed

    Ma, Jane Y C; Young, Shih-Houng; Mercer, Robert R; Barger, Mark; Schwegler-Berry, Diane; Ma, Joseph K; Castranova, Vincent

    2014-07-15

    Cerium compounds have been used as a fuel-borne catalyst to lower the generation of diesel exhaust particles (DEPs), but are emitted as cerium oxide nanoparticles (CeO2) along with DEP in the diesel exhaust. The present study investigates the effects of the combined exposure to DEP and CeO2 on the pulmonary system in a rat model. Specific pathogen-free male Sprague-Dawley rats were exposed to CeO2 and/or DEP via a single intratracheal instillation and were sacrificed at various time points post-exposure. This investigation demonstrated that CeO2 induces a sustained inflammatory response, whereas DEP elicits a switch of the pulmonary immune response from Th1 to Th2. Both CeO2 and DEP activated AM and lymphocyte secretion of the proinflammatory cytokines IL-12 and IFN-γ, respectively. However, only DEP enhanced the anti-inflammatory cytokine IL-10 production in response to ex vivo LPS or Concanavalin A challenge that was not affected by the presence of CeO2, suggesting that DEP suppresses host defense capability by inducing the Th2 immunity. The micrographs of lymph nodes show that the particle clumps in DEP+CeO2 were significantly larger than CeO2 or DEP, exhibiting dense clumps continuous throughout the lymph nodes. Morphometric analysis demonstrates that the localization of collagen in the lung tissue after DEP+CeO2 reflects the combination of DEP-exposure plus CeO2-exposure. At 4 weeks post-exposure, the histological features demonstrated that CeO2 induced lung phospholipidosis and fibrosis. DEP induced lung granulomas that were not significantly affected by the presence of CeO2 in the combined exposure. Using CeO2 as diesel fuel catalyst may cause health concerns.

  18. Potential of using cerium oxide nanoparticles for protecting healthy tissue during accelerated partial breast irradiation (APBI).

    PubMed

    Ouyang, Zi; Mainali, Madan Kumar; Sinha, Neeharika; Strack, Guinevere; Altundal, Yucel; Hao, Yao; Winningham, Thomas Andrew; Sajo, Erno; Celli, Jonathan; Ngwa, Wilfred

    2016-04-01

    The purpose of this study is to investigate the feasibility of using cerium oxide nanoparticles (CONPs) as radical scavengers during accelerated partial breast irradiation (APBI) to protect normal tissue. We hypothesize that CONPs can be slowly released from the routinely used APBI balloon applicators-via a degradable coating-and protect the normal tissue on the border of the lumpectomy cavity over the duration of APBI. To assess the feasibility of this approach, we analytically calculated the initial concentration of CONPs required to protect normal breast tissue from reactive oxygen species (ROS) and the time required for the particles to diffuse to various distances from the lumpectomy wall. Given that cerium has a high atomic number, we took into account the possible inadvertent dose enhancement that could occur due to the photoelectric interactions with radiotherapy photons. To protect against a typical MammoSite treatment fraction of 3.4Gy, 5ng·g(-1) of CONPs is required to scavenge hydroxyl radicals and hydrogen peroxide. Using 2nm sized NPs, with an initial concentration of 1mg·g(-1), we found that 2-10days of diffusion is required to obtain desired concentrations of CONPs in regions 1-2cm away from the lumpectomy wall. The resultant dose enhancement factor (DEF) is less than 1.01 under such conditions. Our results predict that CONPs can be employed for radioprotection during APBI using a new design in which balloon applicators are coated with the NPs for sustained/controlled in-situ release from within the lumpectomy cavity.

  19. Effect of polyvinylpyrrolidone on cerium oxide nanoparticle characteristics prepared by a facile heat treatment technique

    NASA Astrophysics Data System (ADS)

    Baqer, Anwar Ali; Matori, Khamirul Amin; Al-Hada, Naif Mohammed; Shaari, Abdul Halim; Saion, Elias; Chyi, Josephine Liew Ying

    An aqueous medium composed of polyvinylpyrrolidone (PVP) and cerium nitrates at calcination temperature was utilised in the production of cerium oxide (CeO2) semiconductor nanoparticles. A variety of analytical approaches was utilized to examine the structural, morphological and optical characteristics of the resulting nanoparticles. Differential thermal (DTA) and thermogravimetric (TGA) analyses, indicated that the best calcination temperatures for achieving CeO2 nanoparticle production were more than 485 °C. The results from Fourier-transform infrared (FTIR) verified the formation of a crystalline structure after calcination procedures were performed to remove residual organic compounds. Additionally, results from X-ray diffraction (XRD) analysis confirmed the cubic fluorite structure of the CeO2 produced. Samples were also analysed by energy dispersive spectroscopy (EDXA) which indicated the existence of O and Ce in the samples. Field emission scanning electron microscopy (FESEM) was used in the characterisation of nanoparticle morphological features. Transmission electron microscopy (TEM) was employed to estimate typical nanoparticle and distribution within sample. This analysis indicated that mean particle sizes were inversely correlated with PVP concentration, with nanoparticle sizes ranging between 12 ± 7 nm at 0.03 g/mL PVP and 6 ± 2 nm at 0.05 g/mL PVP. These results corroborated those obtained by XRD analysis. A UV-vis spectrophotometer was utilised in the demonstration of optical properties and to examine the band gap energy of samples. The potential UV-shielding properties of the nanoparticles were demonstrated by the observed blue shift of the estimated optical energy band, i.e. from 3.35 to 3.43 eV, whilst PL spectra results indicated that decreasing particle size was associated with diminishing photoluminescence intensity.

  20. Interactive effects of cerium oxide and diesel exhaust nanoparticles on inducing pulmonary fibrosis

    PubMed Central

    Ma, Jane Y.C.; Young, Shih-Houng; Mercer, Robert R.; Barger, Mark; Schwegler-Berry, Diane; Ma, Joseph K.; Castranova, Vincent

    2015-01-01

    Cerium compounds have been used as a fuel-borne catalyst to lower the generation of diesel exhaust particles (DEPs), but are emitted as cerium oxide nanoparticles (CeO2) along with DEP in the diesel exhaust. The present study investigates the effects of the combined exposure to DEP and CeO2 on the pulmonary system in a rat model. Specific pathogen-free male Sprague–Dawley rats were exposed to CeO2 and/or DEP via a single intratracheal instillation and were sacrificed at various time points post-exposure. This investigation demonstrated that CeO2 induces a sustained inflammatory response, whereas DEP elicits a switch of the pulmonary immune response from Th1 to Th2. Both CeO2 and DEP activated AM and lymphocyte secretion of the proinflammatory cytokines IL-12 and IFN-γ respectively. However, only DEP enhanced the anti-inflammatory cytokine IL-10 production in response to ex vivo LPS or Concanavalin A challenge that was not affected by the presence of CeO2, suggesting that DEP suppresses host defense capability by inducing the Th2 immunity. The micrographs of lymph nodes show that the particle clumps in DEP + CeO2 were significantly larger than CeO2 or DEP, exhibiting dense clumps continuous throughout the lymph nodes. Morphometric analysis demonstrates that the localization of collagen in the lung tissue after DEP + CeO2 reflects the combination of DEP-exposure plus CeO2-exposure. At 4 weeks post-exposure, the histological features demonstrated that CeO2 induced lung phospholipidosis and fibrosis. DEP induced lung granulomas that were not significantly affected by the presence of CeO2 in the combined exposure. Using CeO2 as diesel fuel catalyst may cause health concerns. PMID:24793434

  1. Untangling the biological effects of cerium oxide nanoparticles: the role of surface valence states

    PubMed Central

    Pulido-Reyes, Gerardo; Rodea-Palomares, Ismael; Das, Soumen; Sakthivel, Tamil Selvan; Leganes, Francisco; Rosal, Roberto; Seal, Sudipta; Fernández-Piñas, Francisca

    2015-01-01

    Cerium oxide nanoparticles (nanoceria; CNPs) have been found to have both pro-oxidant and anti-oxidant effects on different cell systems or organisms. In order to untangle the mechanisms which underlie the biological activity of nanoceria, we have studied the effect of five different CNPs on a model relevant aquatic microorganism. Neither shape, concentration, synthesis method, surface charge (ζ-potential), nor nominal size had any influence in the observed biological activity. The main driver of toxicity was found to be the percentage of surface content of Ce3+ sites: CNP1 (58%) and CNP5 (40%) were found to be toxic whereas CNP2 (28%), CNP3 (36%) and CNP4 (26%) were found to be non-toxic. The colloidal stability and redox chemistry of the most and least toxic CNPs, CNP1 and CNP2, respectively, were modified by incubation with iron and phosphate buffers. Blocking surface Ce3+ sites of the most toxic CNP, CNP1, with phosphate treatment reverted toxicity and stimulated growth. Colloidal destabilization with Fe treatment only increased toxicity of CNP1. The results of this study are relevant in the understanding of the main drivers of biological activity of nanoceria and to define global descriptors of engineered nanoparticles (ENPs) bioactivity which may be useful in safer-by-design strategies of nanomaterials. PMID:26489858

  2. Cerium oxide nanoparticles prevent apoptosis in primary cortical culture by stabilizing mitochondrial membrane potential.

    PubMed

    Arya, A; Sethy, N K; Das, M; Singh, S K; Das, A; Ujjain, S K; Sharma, R K; Sharma, M; Bhargava, K

    2014-07-01

    Cerium oxide nanoparticles (CNPs) of spherical shape have unique antioxidant capacity primarily due to alternating + 3 and + 4 oxidation states and crystal defects. Several studies revealed the protective efficacies of CNPs in cells and tissues against the oxidative damage. However, its effect on mitochondrial functioning, downstream effectors of radical burst and apoptosis remains unknown. In this study, we investigated whether CNPs treatment could protect the primary cortical cells from loss of mitochondrial membrane potential (Δψm) and Δψm-dependent cell death. CNPs with spherical morphology and size range 7-10 nm were synthesized and utilized at a concentration of 25 nM on primary neuronal culture challenged with 50 μM of hydrogen peroxide (H2O2). We showed that optimal dose of CNPs minimized ROS content of the cells and also curbed related surge in cellular calcium flux. Importantly, CNPs treatment prevented apoptotic loss of cell viability. Reduction in the apoptosis could be successfully attributed to the maintenance of Δψm and restoration of major redox equivalents NADH/NAD(+) ratio and cellular ATP. These findings, therefore, suggest possible route of CNPs protective efficacies in primary cortical culture.

  3. Untangling the biological effects of cerium oxide nanoparticles: the role of surface valence states

    NASA Astrophysics Data System (ADS)

    Pulido-Reyes, Gerardo; Rodea-Palomares, Ismael; Das, Soumen; Sakthivel, Tamil Selvan; Leganes, Francisco; Rosal, Roberto; Seal, Sudipta; Fernández-Piñas, Francisca

    2015-10-01

    Cerium oxide nanoparticles (nanoceria; CNPs) have been found to have both pro-oxidant and anti-oxidant effects on different cell systems or organisms. In order to untangle the mechanisms which underlie the biological activity of nanoceria, we have studied the effect of five different CNPs on a model relevant aquatic microorganism. Neither shape, concentration, synthesis method, surface charge (ζ-potential), nor nominal size had any influence in the observed biological activity. The main driver of toxicity was found to be the percentage of surface content of Ce3+ sites: CNP1 (58%) and CNP5 (40%) were found to be toxic whereas CNP2 (28%), CNP3 (36%) and CNP4 (26%) were found to be non-toxic. The colloidal stability and redox chemistry of the most and least toxic CNPs, CNP1 and CNP2, respectively, were modified by incubation with iron and phosphate buffers. Blocking surface Ce3+ sites of the most toxic CNP, CNP1, with phosphate treatment reverted toxicity and stimulated growth. Colloidal destabilization with Fe treatment only increased toxicity of CNP1. The results of this study are relevant in the understanding of the main drivers of biological activity of nanoceria and to define global descriptors of engineered nanoparticles (ENPs) bioactivity which may be useful in safer-by-design strategies of nanomaterials.

  4. Adsorption and Reaction of Methanethiol on Thin-Film Cerium Oxide

    SciTech Connect

    Mullins, David R; McDonald, Tom S

    2008-01-01

    The adsorption and reaction of methanethiol, CH{sub 3}SH, have been studied on cerium oxide thin films that were vapor deposited on Ru(0 0 0 1). The behavior of the CH{sub 3}SH was examined as a function of the Ce oxidation state. CH{sub 3}SH weakly interacts with fully oxidized CeO{sub 2}(1 1 1) forming both chemisorbed CH{sub 3}SH and CH{sub 3}S + OH. OH forms through the reaction of the sulfhydrol H with the surface O. These species recombine and desorb near 180 K leaving the surface virtually clean. When the ceria is ca. 50% reduced, the chemisorbed CH{sub 3}SH desorbs near 150 K while the CH{sub 3}S + OH are stable to 400 K. These species react above 450 K to produce predominantly CH{sub 4} and CH{sub 3}SH. A small amount of CH{sub 2}O and water are also formed through reaction with the O in the ceria. Atomic S is left on the surface. S 2p, C 1s and O 1s soft X-ray photoelectron spectroscopy were used to identify the nature of the chemisorbed species and the adsorption site of the CH{sub 3}S or S.

  5. Adsorption and reaction of methanethiol on thin-film cerium oxide

    NASA Astrophysics Data System (ADS)

    Mullins, D. R.; McDonald, T. S.

    2008-03-01

    The adsorption and reaction of methanethiol, CH 3SH, have been studied on cerium oxide thin films that were vapor deposited on Ru(0 0 0 1). The behavior of the CH 3SH was examined as a function of the Ce oxidation state. CH 3SH weakly interacts with fully oxidized CeO 2(1 1 1) forming both chemisorbed CH 3SH and CH 3S + OH. OH forms through the reaction of the sulfhydrol H with the surface O. These species recombine and desorb near 180 K leaving the surface virtually clean. When the ceria is ca. 50% reduced, the chemisorbed CH 3SH desorbs near 150 K while the CH 3S + OH are stable to 400 K. These species react above 450 K to produce predominantly CH 4 and CH 3SH. A small amount of CH 2O and water are also formed through reaction with the O in the ceria. Atomic S is left on the surface. S 2p, C 1s and O 1s soft X-ray photoelectron spectroscopy were used to identify the nature of the chemisorbed species and the adsorption site of the CH 3S or S.

  6. Effective medium approximation of the optical properties of electrochromic cerium-titanium oxide compounds

    SciTech Connect

    Rottkay, K. von; Richardson, T.; Rubin, M.; Slack, J.

    1997-07-01

    Cerium titanium oxide samples derived from a solution have been compared against sputtered films over a wide range of different compositions. X-ray diffraction was used to investigate the structural properties of the compound material existing in a two-phase mixture M{sub A}O{sub 2}-M{sub B}O{sub 2}. The optical properties were evaluated over the whole solar spectrum by variable angle spectroscopic ellipsometry combined with spectrophotometry. The spectral complex refractive index was determined for CeO{sub 2} and TiO{sub 2}, as well as for their compounds. To reduce the large number of permutations in composition of multi-component oxides it would be useful to be able to predict the properties of the mixtures from the pure oxide components. Therefore these results were compared to those obtained by effective medium theory utilizing the optical constants of CeO{sub 2} and TiO{sub 2}. In order to investigate the performance as passive counter-electrode in Li{sup +} based electrochromic devices the films were tested by cyclic voltammetry with in-situ transmission control. Chemical composition was measured by Rutherford backscattering spectrometry. Surface morphology was analyzed by atomic force microscopy.

  7. Real-time observation of dynamic process of oxygen vacancy migration in cerium oxides under electric field

    SciTech Connect

    Li, Xiaomin; Qi, Kuo; Sun, Muhua; Huang, Qianming; Xu, Zhi E-mail: xdbai@iphy.ac.cn; Wang, Wenlong; Bai, Xuedong E-mail: xdbai@iphy.ac.cn

    2015-11-23

    The dynamic process of oxygen vacancy migration driven by the external electric field is directly observed at atomic scale in the cerium oxides (CeO{sub 2}) thin film by in-situ transmission electron microscopy method. When a bias voltage of a proper value is applied across the CeO{sub 2} film, the oxygen vacancies are formed near the interface of CeO{sub 2}/anode, followed by their migration along the direction of the external electric field. The structural modulation occurs in the [110] zone axis due to the ordering of oxygen vacancies. The migration of oxygen vacancies results in the reversible structural transformation, i.e., releasing and storing oxygen processes in CeO{sub 2}, which is of great significance for the ionic and electronic applications of the cerium oxides materials, such as oxygen pump, gas sensor, resistive random access memory, etc.

  8. Enzyme-free Detection of Hydrogen Peroxide from Cerium Oxide Nanoparticles Immobilized on Poly(4-vinylpyridine) Self-Assembled Monolayers

    SciTech Connect

    Gaynor, James D.; Karakoti, Ajay S.; Inerbaev, Talgat; Sanghavi, Shail P.; Nachimuthu, Ponnusamy; Shutthanandan, V.; Seal, Sudipta; Thevuthasan, Suntharampillai

    2013-05-02

    A single layer of oxygen-deficient cerium oxide nanoparticles (CNPs) are immobilized on microscopic glass slide using poly(4-vinylpyridine) (PVP) self-assembled monolayers (SAMs). A specific colorimetric property of CNPs when reacted with hydrogen peroxide allows for the direct, single-step peroxide detection which can be used in medical diagnosis and explosives detection. Multiple PVP-CNP immobilized layers improve sensitivity of detection and the sensor can be regenerated for reuse.

  9. Getting the most out of your cerium oxide glass polishing slurry: reducing risk and improving performance with plasma produced particles

    NASA Astrophysics Data System (ADS)

    Murray, Patrick G.; Hooper, Abigail; Keleher, Jason; Kaiser, Jordan; Nichol, Meghan

    2013-09-01

    Recent dramatic price volatility and assurance of supply concerns with cerium oxide have left many users of this material in an uncertain and vulnerable position. Since few viable alternatives to ceria for precision glass polishing exist, and much of the supply is very concentrated geographically, technology which conserves ceria, improves absolute removal rate and promotes slurry longevity becomes extremely attractive under these circumstances. Using a plasma-based process to produce cerium oxide confers some unique attributes to the particles which make them particularly well suited for precision glass polishing operations. Many of those same particle characteristics, such as full crystallinity, near theoretical density, very high surface and bulk purity and extremely high zeta potentials in water can also be useful in mitigating the risks associated with a limited and costly ceria supply. This paper will explore how plasma-derived particles, in combination with a high performance chemistry package, can together constitute a fully formulated precision glass polishing slurry with very high activity, extended slurry lifetime, ability to recycle, and excellent overall process economics. Results showing the effect of particle longevity and chemical additives on removal rate and process stability will be discussed in detail, and selected examples which distinguish the benefits of a fully formulated, plasma-derived cerium oxide polishing slurry over conventional milled ceria will be shown.

  10. Simultaneous oxidation and adsorption of As(III) from water by cerium modified chitosan ultrafine nanobiosorbent.

    PubMed

    Zhang, Lingfan; Zhu, Tianyi; Liu, Xin; Zhang, Wenqing

    2016-05-05

    Since most existing arsenic removal adsorbents are difficult to effectively remove arsenite (As(III)), an urgent need is to develop an efficient adsorbent for removing As(III) from contaminated water. In this study, a novel ultrafine nanobiosorbent of cerium modified chitosan (Ce-CNB) with simultaneous oxidation and adsorption As(III) performance has been successfully developed. The resulting Ce-CNB with or without As(III) adsorption was characterized by FTIR, XRD, SEM, EDS, TEM, EMI and XPS analysis. Batch of adsorption experiments were performed to investigate the effects of various conditions on the As(III) adsorption. The adsorption behaviors were well described by the Langmuir isotherm and the pseudo-second-order kinetic model, with the maximum adsorption capacities of 57.5 mg g(-1). The adsorption mechanisms for As(III) were (i) formed monodentate and bidentate complexes between hydroxyl groups and arsenite; and (ii) partial As(III) oxidized to As(V) followed by simultaneously adsorbed on the surface of Ce-CNB. This novel nanocomposite can be reused while maintaining a high removal efficiency and can be applied to treat 5.8L of As(III)-polluted water with the effluent concentration lower than the World Health Organization standard, which suggests its great potential to remove As(III) from contaminated water.

  11. Evidence for an oxygen evolving iron–oxo–cerium intermediate in iron-catalysed water oxidation

    PubMed Central

    Codolà, Zoel; Gómez, Laura; Kleespies, Scott T.; Que, Lawrence; Costas, Miquel; Lloret-Fillol, Julio

    2016-01-01

    The non-haem iron complex α-[FeII(CF3SO3)2(mcp)] (mcp = (N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)-1,2-cis-diaminocyclohexane) reacts with CeIV to oxidize water to O2, representing an iron-based functional model for the oxygen evolving complex of photosystem II. Here we trap an intermediate, characterized by cryospray ionization high resolution mass spectrometry and resonance Raman spectroscopy, and formulated as [(mcp)FeIV(O) (μ-O)CeIV(NO3)3]+, the first example of a well-characterized inner-sphere complex to be formed in cerium(IV)-mediated water oxidation. The identification of this reactive FeIV–O–CeIV adduct may open new pathways to validate mechanistic notions of an analogous MnV–O–CaII unit in the oxygen evolving complex that is responsible for carrying out the key O–O bond forming step. PMID:25609387

  12. Gold-supported cerium-doped NiOx catalysts for water oxidation

    NASA Astrophysics Data System (ADS)

    Ng, Jia Wei Desmond; García-Melchor, Max; Bajdich, Michal; Chakthranont, Pongkarn; Kirk, Charlotte; Vojvodic, Aleksandra; Jaramillo, Thomas F.

    2016-05-01

    The development of high-performance catalysts for the oxygen-evolution reaction (OER) is paramount for cost-effective conversion of renewable electricity to fuels and chemicals. Here we report the significant enhancement of the OER activity of electrodeposited NiOx films resulting from the combined effects of using cerium as a dopant and gold as a metal support. This NiCeOx-Au catalyst delivers high OER activity in alkaline media, and is among the most active OER electrocatalysts yet reported. On the basis of experimental observations and theoretical modelling, we ascribe the activity to a combination of electronic, geometric and support effects, where highly active under-coordinated sites at the oxide support interface are modified by the local chemical binding environment and by doping the host Ni oxide with Ce. The NiCeOx-Au catalyst is further demonstrated in a device context by pairing it with a nickel-molybdenum hydrogen evolution catalyst in a water electrolyser, which delivers 50 mA consistently at 1.5 V over 24 h of continuous operation.

  13. Electrochemical Urea Biosensor Based on Sol-gel Derived Nanostructured Cerium Oxide

    NASA Astrophysics Data System (ADS)

    Ansari, Anees A.; Azahar, Md; Malhotra, B. D.

    2012-04-01

    Urease (Urs) and glutamate dehydrogenase (GLDH) have been co-immobilized onto a nanostructured-cerium oxide (Nano-CeO2) film deposited onto a indium-tin-oxide (ITO) coated glass substrate by dip-coating via sol-gel process for urea detection. This nanostructured film has characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR), Scanning electron microscope (SEM) and electrochemical techniques, respectively. The particle size of the Nano-CeO2 film has been found to be 23 nm. Electrochemcial response (CV) studies show that Ur-GLDH/Nano-CeO2/ITO bioelectrode is found to be sensitive in the 10-80 mg/dL urea concentration range and can detect urea concentration upto 0.1 mg/dL level. The value of Michaelis-Menten constant (Km) estimated using Lineweaver-Burke plot found as 6.09 mg/dL indicates enhancement in the affinity and/or activity of enzyme attached to their nanobiocomposite. This bioelectrode retained 95% of enzyme activity after 6 months at 4°C.

  14. Bio-therapeutic Potential and Cytotoxicity Assessment of Pectin-Mediated Synthesized Nanostructured Cerium Oxide.

    PubMed

    Patil, Sandeep N; Paradeshi, Jayasinh S; Chaudhari, Prapti B; Mishra, Satyendra J; Chaudhari, Bhushan L

    2016-10-01

    In the present studies, renewable and nontoxic biopolymer, pectin, was extracted from Indian red pomelo fruit peels and used for the synthesis of cerium oxide nanoparticles (CeO2-NPs) having bio-therapeutic potential. The structural information of extracted pectin was investigated by FTIR and NMR spectroscopic techniques. Physicochemical characteristics of this pectin suggested its application in the synthesis of metal oxide nanoparticles. Using this pectin as a template, CeO2-NPs were synthesized by simple, one step and eco-friendly approach. The UV-Vis spectrum of synthesized CeO2-NPs exhibited a characteristic absorption peak at wavelength 345 nm, which can be assigned to its intrinsic band gap (3.59 eV) absorption. Photoluminescence measurements of CeO2-NPs revealed that the broad emission was composed of seven different bands. FTIR analysis ensured involvement of pectin in the formation and stabilization of CeO2-NPs. FT-Raman spectra showed a sharp Raman active mode peak at 461.8 cm(-1) due to a symmetrical stretching mode of Ce-O vibration. DLS, FESEM, EDX, and XRD analysis showed that the CeO2-NPs prepared were polydispersed, spherical shaped with a cubic fluorite structure and average particle size ≤40 nm. These CeO2-NPs displayed broad spectrum antimicrobial activity, antioxidant potential, and non-cytotoxic nature.

  15. A nanostructured cerium oxide film-based immunosensor for mycotoxin detection

    NASA Astrophysics Data System (ADS)

    Kaushik, Ajeet; Rathee Solanki, Pratima; Ansari, Anees Ahmad; Ahmad, Sharif; Dhar Malhotra, Bansi

    2009-02-01

    Rabbit-immunoglobulin antibodies (r-IgGs) and bovine serum albumin (BSA) have been immobilized onto sol-gel-derived nanostructured cerium oxide (nanoCeO2) film fabricated onto an indium-tin-oxide (ITO) coated glass plate to detect ochratoxin-A (OTA). Broad reflection planes obtained in x-ray diffraction (XRD) patterns reveal the formation of CeO2 nanostructures. Electrochemical studies reveal that nanoCeO2 particles provide an increased electroactive surface area for loading of r-IgGs with desired orientation, resulting in enhanced electron communication between r-IgGs and electrode. BSA/r-IgGs/nano CeO2/ITO immunoelectrode exhibits improved characteristics such as linear range (0.5-6 ng dl-1), low detection limit (0.25 ng dl-1), fast response time (30 s) and high sensitivity (1.27 µA ng-1 dl-1 cm-2). The high value of the association constant (Ka, 0.9 × 1011 l mol-1) indicates the high affinity of the BSA/r-IgGs/nanoCeO2/ITO immunoelectrode to OTA.

  16. Evaluation of cerium oxide coated Cu cermets as inert anodes for aluminum electrowinning

    SciTech Connect

    Not Available

    1992-08-01

    Cu/NiFe{sub 2}O{sub 4} cermets were evaluated, with and without an in-situ deposited CEROX (TM; cerium oxide) coating, in 100 h laboratory A1 electrowinning tests. Bath ratio and current density were varied between tests and corrosion was determined by contamination of the aluminum and cryolite by cermet components (Cu, Fe, and Ni). Higher bath ratios of 1.5 to 1.6 led to less corrosion and thicker CEROX coatings. Lower current densities led to slightly less corrosion but much less oxidation of the Cu cermet substrate. At identical test conditions, the corrosion of the CEROX coated cermets was 1/7 that of an uncoated cermet. Corrosion was increased in CEROX coated cermets tested under unsaturated alumina conditions. The electrical conductivity of the CEROX coating was measured to be {approximately}0.2 ohm{sup {minus}1}cm{sup {minus}1}, resulting in a slight voltage penalty, depending on the thickness of the coating.

  17. Cerium Dioxide Nanoparticle Exposure Improves Microvascular Dysfunction and Reduces Oxidative Stress in Spontaneously Hypertensive Rats

    PubMed Central

    Minarchick, Valerie C.; Stapleton, Phoebe A.; Sabolsky, Edward M.; Nurkiewicz, Timothy R.

    2015-01-01

    The elevated production of reactive oxygen species (ROS) in the vascular wall is associated with cardiovascular diseases such as hypertension. This increase in oxidative stress contributes to various mechanisms of vascular dysfunction, such as decreased nitric oxide bioavailability. Therefore, anti-oxidants are being researched to decrease the high levels of ROS, which could improve the microvascular dysfunction associated with various cardiovascular diseases. From a therapeutic perspective, cerium dioxide nanoparticles (CeO2 NP) hold great anti-oxidant potential, but their in vivo activity is unclear. Due to this potential anti-oxidant action, we hypothesize that injected CeO2 NP would decrease microvascular dysfunction and oxidative stress associated with hypertension. In order to simulate a therapeutic application, spontaneously hypertensive (SH) and Wistar-Kyoto (WKY) rats were intravenously injected with either saline or CeO2 NP (100 μg suspended in saline). Twenty-four hours post-exposure mesenteric arteriolar reactivity was assessed via intravital microscopy. Endothelium-dependent and –independent function was assessed via acetylcholine and sodium nitroprusside. Microvascular oxidative stress was analyzed using fluorescent staining in isolated mesenteric arterioles. Finally, systemic inflammation was examined using a multiplex analysis and venular leukocyte flux was counted. Endothelium-dependent dilation was significantly decreased in the SH rats (29.68 ± 3.28%, maximal response) and this microvascular dysfunction was significantly improved following CeO2 NP exposure (43.76 ± 4.33%, maximal response). There was also an increase in oxidative stress in the SH rats, which was abolished following CeO2 NP treatment. These results provided evidence that CeO2 NP act as an anti-oxidant in vivo. There were also changes in the inflammatory profile in the WKY and SH rats. In WKY rats, IL-10 and TNF-α were increased following CeO2 NP treatment. Finally, leukocyte

  18. Tissue distribution of inhaled micro- and nano-sized cerium oxide particles in rats: results from a 28-day exposure study.

    PubMed

    Geraets, Liesbeth; Oomen, Agnes G; Schroeter, Jeffry D; Coleman, Victoria A; Cassee, Flemming R

    2012-06-01

    In order to obtain more insight into the tissue distribution, accumulation, and elimination of cerium oxide nanoparticles after inhalation exposure, blood and tissue kinetics were investigated during and after a 28-day inhalation study in rats with micro- and nanocerium oxide particles (nominal primary particle size: < 5000, 40, and 5-10 nm). Powder aerosolization resulted in comparable mass median aerodynamic diameter (1.40, 1.17, and 1.02 μm). After single exposure, approximately 10% of the inhaled dose was measured in lung tissue, as was also estimated by a multiple path particle dosimetry model (MPPD). Though small differences in pulmonary deposition efficiencies of cerium oxide were observed, no consistent differences in pulmonary deposition between the micro- and nanoparticles were observed. Each cerium oxide sample was also distributed to tissues other than lung after a single 6-h exposure, such as liver, kidney, and spleen and also brain, testis, and epididymis. No clear particle size-dependent effect on extrapulmonary tissue distribution was observed. Repeated exposure to cerium oxide resulted in significant accumulation of the particles in the (extra)pulmonary tissues. In addition, tissue clearance was shown to be slow, and, overall, insignificant amounts of cerium oxide were eliminated from the body at 48- to 72-h post-exposure. In conclusion, no clear effect of the primary particle size or surface area on pulmonary deposition and extrapulmonary tissue distribution could be demonstrated. This is most likely explained by similar aerodynamic diameter of the cerium oxide particles in air because of the formation of aggregates and irrespective possible differences in surface characteristics. The implications of the accumulation of cerium oxide particles for systemic toxicological effects after repeated chronic exposure via ambient air are significant and require further exploration.

  19. Exposure, health and ecological effects review of engineered nanoscale cerium and cerium oxide associated with its use as a fuel additive.

    PubMed

    Cassee, Flemming R; van Balen, Erna C; Singh, Charanjeet; Green, David; Muijser, Hans; Weinstein, Jason; Dreher, Kevin

    2011-03-01

    Advances of nanoscale science have produced nanomaterials with unique physical and chemical properties at commercial levels which are now incorporated into over 1000 products. Nanoscale cerium (di) oxide (CeO(2)) has recently gained a wide range of applications which includes coatings, electronics, biomedical, energy and fuel additives. Many applications of engineered CeO(2) nanoparticles are dispersive in nature increasing the risk of exposure and interactions with a variety of environmental media with unknown health, safety and environmental implications. As evident from a risk assessment perspective, the health effects of CeO(2) nanoparticles are not only dependent on their intrinsic toxicity but also on the level of exposure to these novel materials. Although this may seem logical, numerous studies have assessed the health effects of nanoparticles without this simple but critical risk assessment perspective. This review extends previous exposure and toxicological assessments for CeO(2) particles by summarizing the current state of micro and nano-scale cerium exposure and health risks derived from epidemiology, air quality monitoring, fuel combustion and toxicological studies to serve as a contemporary comprehensive and integrated toxicological assessment. Based on the new information presented in this review there is an ongoing exposure to a large population to new diesel emissions generated using fuel additives containing CeO2 nanoparticles for which the environmental (air quality and climate change) and public health impacts of this new technology are not known. Therefore, there is an absolute critical need for integrated exposure and toxicological studies in order to accurately assess the environmental, ecological and health implications of nanotechnology enabled diesel fuel additives with existing as well as new engine designs and fuel formulations.

  20. A phosphate-dependent shift in redox state of cerium oxide nanoparticles and its effects on catalytic properties

    SciTech Connect

    Singh, Sanjay; Dosani, Talib; Karakoti, Ajay S.; Kumar, Amit; Seal, Sudipta; Self, William

    2011-10-01

    Cerium oxide nanoparticles (CeNPs) have shown promise as catalytic antioxidants in cell culture and animal models as both superoxide dismutase and catalase mimetics. The reactivity of the cerium (Ce) atoms at the surface of its oxide particle is critical to such therapeutic properties, yet little is known about the potential for a protein or small molecule corona to form on these materials in vivo. Moreover Ce atoms in these active sites have the potential to interact with small molecule anions, peptides, or sugars when administered in culture or animal models. Several nanomaterials have been shown to alter or aggregate under these conditions, rendering them less useful for biomedical applications. In this work we have studied the change in catalytic properties of CeNPs when exposed to various biologically relevant conditions in vitro. We have found that CeNPs are resistant to broad changes in pH and also not altered by incubation in cell culture medium. However to our surprise phosphate anions significantly altered the characteristics of these nanomaterials and shifted the catalytic behavior due to the binding of phosphate anions to cerium. Given the abundance of phosphate in biological systems in an inorganic form, it is likely that the action of CeNPs as a catalyst may be strongly influenced by the local concentration of phosphate in the cells and/or tissues in which it has been introduced.

  1. Influence of agglomeration of cerium oxide nanoparticles and speciation of cerium(III) on short term effects to the green algae Chlamydomonas reinhardtii.

    PubMed

    Röhder, Lena A; Brandt, Tanja; Sigg, Laura; Behra, Renata

    2014-07-01

    Cerium oxide nanoparticles (CeO2 NP) are increasingly used in industrial applications and may be released to the aquatic environment. The fate of CeO2 NP and effects on algae are largely unknown. In this study, the short term effects of CeO2 NP in two different agglomeration states on the green algae Chlamydomonas reinhardtii were examined. The role of dissolved cerium(III) on toxicity, its speciation and the dissolution of CeO2 NP were considered. The role of cell wall of C. reinhardtii as a barrier and its influence on the sensitivity to CeO2 NP and cerium(III) was evaluated by testing both, the wild type and the cell wall free mutant of C. reinhardtii. Characterization showed that CeO2 NP had a surface charge of ∼0mV at physiological pH and agglomerated in exposure media. Phosphate stabilized CeO2 NP at pH 7.5 over 24h. This effect was exploited to test CeO2 NP dispersed in phosphate with a mean size of 140nm and agglomerated in absence of phosphate with a mean size of 2000nm. The level of dissolved cerium(III) in CeO2 NP suspensions was very low and between 0.1 and 27nM in all tested media. Exposure of C. reinhardtii to Ce(NO3)3 decreased the photosynthetic yield in a concentration dependent manner with EC50 of 7.5±0.84μM for wild type and EC50 of 6.3±0.53μM for the cell wall free mutant. The intracellular level of reactive oxygen species (ROS) increased upon exposure to Ce(NO3)3 with effective concentrations similar to those inhibiting photosynthesis. The agglomerated CeO2 NP caused a slight decrease of photosynthetic yield at the highest concentrations (100μM), while no effect was observed for dispersed CeO2 NP. The low toxicity of agglomerated CeO2 NP was attributed quantitatively to Ce(3+) ions co-occurring in the nanoparticle suspension whereas for dispersed CeO2 NP, dissolved Ce(3+) was precipitated with phosphate and not bioavailable. Furthermore CeO2 NP did not affect the intracellular ROS level. The cell wall free mutant and wild type of C

  2. The biological effects of subacute inhalation of diesel exhaust following addition of cerium oxide nanoparticles in atherosclerosis-prone mice☆

    PubMed Central

    Cassee, Flemming R.; Campbell, Arezoo; Boere, A. John F.; McLean, Steven G.; Duffin, Rodger; Krystek, Petra; Gosens, Ilse; Miller, Mark R.

    2012-01-01

    Background Cerium oxide (CeO2) nanoparticles improve the burning efficiency of fuel, however, little is known about health impacts of altered emissions from the vehicles. Methods Atherosclerosis-prone apolipoprotein E knockout (ApoE−/−) mice were exposed by inhalation to diluted exhaust (1.7 mg/m3, 20, 60 or 180 min, 5 day/week, for 4 weeks), from an engine using standard diesel fuel (DE) or the same diesel fuel containing 9 ppm cerium oxide nanoparticles (DCeE). Changes in hematological indices, clinical chemistry, atherosclerotic burden, tissue levels of inflammatory cytokines and pathology of the major organs were assessed. Results Addition of CeO2 to fuel resulted in a reduction of the number (30%) and surface area (10%) of the particles in the exhaust, whereas the gaseous co-pollutants were increased (6–8%). There was, however, a trend towards an increased size and complexity of the atherosclerotic plaques following DE exposure, which was not evident in the DCeE group. There were no clear signs of altered hematological or pathological changes induced by either treatment. However, levels of proinflammatory cytokines were modulated in a brain region and liver following DCeE exposure. Conclusions These results imply that addition of CeO2 nanoparticles to fuel decreases the number of particles in exhaust and may reduce atherosclerotic burden associated with exposure to standard diesel fuel. From the extensive assessment of biological parameters performed, the only concerning effect of cerium addition was a slightly raised level of cytokines in a region of the central nervous system. Overall, the use of cerium as a fuel additive may be a potentially useful way to limit the health effects of vehicle exhaust. However, further testing is required to ensure that such an approach is not associated with a chronic inflammatory response which may eventually cause long-term health effects. PMID:22507957

  3. The biological effects of subacute inhalation of diesel exhaust following addition of cerium oxide nanoparticles in atherosclerosis-prone mice

    SciTech Connect

    Cassee, Flemming R.; Campbell, Arezoo; Boere, A. John F.; McLean, Steven G.; Krystek, Petra; Gosens, Ilse; Miller, Mark R.

    2012-05-15

    Background: Cerium oxide (CeO{sub 2}) nanoparticles improve the burning efficiency of fuel, however, little is known about health impacts of altered emissions from the vehicles. Methods: Atherosclerosis-prone apolipoprotein E knockout (ApoE{sup -/-}) mice were exposed by inhalation to diluted exhaust (1.7 mg/m{sup 3}, 20, 60 or 180 min, 5 day/week, for 4 weeks), from an engine using standard diesel fuel (DE) or the same diesel fuel containing 9 ppm cerium oxide nanoparticles (DCeE). Changes in hematological indices, clinical chemistry, atherosclerotic burden, tissue levels of inflammatory cytokines and pathology of the major organs were assessed. Results: Addition of CeO{sub 2} to fuel resulted in a reduction of the number (30%) and surface area (10%) of the particles in the exhaust, whereas the gaseous co-pollutants were increased (6-8%). There was, however, a trend towards an increased size and complexity of the atherosclerotic plaques following DE exposure, which was not evident in the DCeE group. There were no clear signs of altered hematological or pathological changes induced by either treatment. However, levels of proinflammatory cytokines were modulated in a brain region and liver following DCeE exposure. Conclusions: These results imply that addition of CeO{sub 2} nanoparticles to fuel decreases the number of particles in exhaust and may reduce atherosclerotic burden associated with exposure to standard diesel fuel. From the extensive assessment of biological parameters performed, the only concerning effect of cerium addition was a slightly raised level of cytokines in a region of the central nervous system. Overall, the use of cerium as a fuel additive may be a potentially useful way to limit the health effects of vehicle exhaust. However, further testing is required to ensure that such an approach is not associated with a chronic inflammatory response which may eventually cause long-term health effects.

  4. CO Responses of Sensors Based on Cerium Oxide Thick Films Prepared from Clustered Spherical Nanoparticles

    PubMed Central

    Izu, Noriya; Matsubara, Ichiro; Itoh, Toshio; Akamatsu, Takafumi; Shin, Woosuck

    2013-01-01

    Various types of CO sensors based on cerium oxide (ceria) have been reported recently. It has also been reported that the response speed of CO sensors fabricated from porous ceria thick films comprising nanoparticles is extremely high. However, the response value of such sensors is not suitably high. In this study, we investigated methods of improving the response values of CO sensors based on ceria and prepared gas sensors from core-shell ceria polymer hybrid nanoparticles. These hybrid nanoparticles have been reported to have a unique structure: The core consists of a cluster of ceria crystallites several nanometers in size. We compared the characteristics of the sensors based on thick films prepared from core-shell nanoparticles with those of sensors based on thick films prepared from conventionally used precipitated nanoparticles. The sensors prepared from the core-shell nanoparticles exhibited a resistance that was ten times greater than that of the sensors prepared from the precipitated nanoparticles. The response values of the gas sensors based on the core-shell nanoparticles also was higher than that of the sensors based on the precipitated nanoparticles. Finally, improvements in sensor response were also noticed after the addition of Au nanoparticles to the thick films used to fabricate the two types of sensors. PMID:23529123

  5. Spectrophotometric determination of H 2-receptor antagonists via their oxidation with cerium(IV)

    NASA Astrophysics Data System (ADS)

    Darwish, Ibrahim A.; Hussein, Samiha A.; Mahmoud, Ashraf M.; Hassan, Ahmed I.

    2008-01-01

    A simple, accurate and sensitive spectrophotometric method has been developed and validated for determination of H 2-receptor antagonists: cimetidine, famotidine, nizatidine and ranitidine hydrochloride. The method was based on the oxidation of these drugs with cerium(IV) in presence of perchloric acid and subsequent measurement of the excess Ce(IV) by its reaction with p-dimethylaminobenzaldehyde to give a red colored product ( λmax at 464 nm). The decrease in the absorption intensity of the colored product (Δ A), due to the presence of the drug was correlated with its concentration in the sample solution. Different variables affecting the reaction were carefully studied and optimized. Under the optimum conditions, linear relationships with good correlation coefficients (0.9990-0.9994) were found between Δ A values and the concentrations of the drugs in a concentration range of 1-20 μg ml -1. The assay limits of detection and quantitation were 0.18-0.60 and 0.54-1.53 μg ml -1, respectively. The method was validated, in terms of accuracy, precision, ruggedness and robustness; the results were satisfactory. The proposed method was successfully applied to the determination of the investigated drugs in pure and pharmaceutical dosage forms (recovery was 98.3-102.6 ± 0.57-1.90%) without interference from the common excipients. The results obtained by the proposed method were comparable with those obtained by the official methods.

  6. Grain size dependence of dielectric relaxation in cerium oxide as high-k layer

    PubMed Central

    2013-01-01

    Cerium oxide (CeO2) thin films used liquid injection atomic layer deposition (ALD) for deposition and ALD procedures were run at substrate temperatures of 150°C, 200°C, 250°C, 300°C, and 350°C, respectively. CeO2 were grown on n-Si(100) wafers. Variations in the grain sizes of the samples are governed by the deposition temperature and have been estimated using Scherrer analysis of the X-ray diffraction patterns. The changing grain size correlates with the changes seen in the Raman spectrum. Strong frequency dispersion is found in the capacitance-voltage measurement. Normalized dielectric constant measurement is quantitatively utilized to characterize the dielectric constant variation. The relationship extracted between grain size and dielectric relaxation for CeO2 suggests that tuning properties for improved frequency dispersion can be achieved by controlling the grain size, hence the strain at the nanoscale dimensions. PMID:23587419

  7. Physiological and biochemical response of soil-grown barley (Hordeum vulgare L.) to cerium oxide nanoparticles.

    PubMed

    Rico, Cyren M; Barrios, Ana C; Tan, Wenjuan; Rubenecia, Rosnah; Lee, Sang Chul; Varela-Ramirez, Armando; Peralta-Videa, Jose R; Gardea-Torresdey, Jorge L

    2015-07-01

    A soil microcosm study was performed to examine the impacts of cerium oxide nanoparticles (nCeO2) on the physiology, productivity, and macromolecular composition of barley (Hordeum vulgare L.). The plants were cultivated in soil treated with nCeO2 at 0, 125, 250, and 500 mg kg(-1) (control, nCeO2-L, nCeO2-M, and nCeO2-H, respectively). Accumulation of Ce in leaves/grains and its effects on plant stress and nutrient loading were analyzed. The data revealed that nCeO2-H promoted plant development resulting in 331 % increase in shoot biomass compared with the control. nCeO2 treatment modified the stress levels in leaves without apparent signs of toxicity. However, plants exposed to nCeO2-H treatment did not form grains. Compared with control, nCeO2-M enhanced grain Ce accumulation by as much as 294 % which was accompanied by remarkable increases in P, K, Ca, Mg, S, Fe, Zn, Cu, and Al. Likewise, nCeO2-M enhanced the methionine, aspartic acid, threonine, tyrosine, arginine, and linolenic acid contents in the grains by up to 617, 31, 58, 141, 378, and 2.47 % respectively, compared with the rest of the treatments. The findings illustrate the beneficial and harmful effects of nanoceria in barley.

  8. Neuroprotective potential of cerium oxide nanoparticles for focal cerebral ischemic stroke.

    PubMed

    Zhou, Da; Fang, Ting; Lu, Lin-Qing; Yi, Li

    2016-08-01

    During the previous years, with the emerging of nanotechnology, the enormous capabilities of nanoparticles have drawn great attention from researchers in terms of their potentials in various aspects of pharmacology. Cerium oxide nanoparticles (nanoceria), considered as one of the most widely used nanomaterials, due to its tempting catalytic antioxidant properties, show a promising potential in diverse disorders, such as cerebral ischemic stroke (CIS), cancer, neurodegenerative and inflammatory diseases. Overwhelming generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) during cerebral ischemia and reperfusion periods is known to aggravate brain damage via sophisticated cellular and molecular mechanisms, and therefore exploration of the antioxidant capacities of nanoceria becomes a new approach in reducing cerebral ischemic injury. Furthermore, utilizing nanoceria as a drug carrier might display the propensity to overcome limitations or inefficacy of other conceivable neuroprotectants and exhibit synergistic effects. In this review, we emphasize on the principle features of nanoceria and current researches concerning nanoceria as a potential therapeutic agent or carrier in improving the prognosis of CIS.

  9. Impact of cerium oxide nanoparticles shape on their in vitro cellular toxicity.

    PubMed

    Forest, Valérie; Leclerc, Lara; Hochepied, Jean-François; Trouvé, Adeline; Sarry, Gwendoline; Pourchez, Jérémie

    2017-02-01

    Cerium oxides (CeO2) nanoparticles, also referred to as nanoceria, are extensively used with a wide range of applications. However, their impact on human health and on the environment is not fully elucidated. The aim of this study was to investigate the influence of the CeO2 nanoparticles morphology on their in vitro toxicity. CeO2 nanoparticles of similar chemical composition and crystallinity were synthesized, only the shape varied (rods or octahedrons/cubes). Macrophages from the RAW264.7 cell line were exposed to these different samples and the toxicity was evaluated in terms of lactate dehydrogenase (LDH) release, Tumor Necrosis Factor alpha (TNF-α) production and reactive oxygen species (ROS) generation. Results showed no ROS production, whatever the nanoparticle shape. The LDH release and the TNF-α production were significantly and dose-dependently enhanced by rod-like nanoparticles, whereas they did not vary with cubic/octahedral nanoparticles. In conclusion, a strong impact of CeO2 nanoparticle morphology on their in vitro toxicity was clearly demonstrated, underscoring that nanoceria shape should be carefully taken in consideration, especially in a "safer by design" context.

  10. Cerium oxide nanoparticles impact yield and modify nutritional parameters in wheat (Triticum aestivum L.).

    PubMed

    Rico, Cyren M; Lee, Sang Chul; Rubenecia, Rosnah; Mukherjee, Arnab; Hong, Jie; Peralta-Videa, Jose R; Gardea-Torresdey, Jorge L

    2014-10-08

    The implications of engineered nanomaterials on crop productivity and food quality are not yet well understood. The impact of cerium oxide nanoparticles (nCeO2) on growth and yield attributes and nutritional composition in wheat (Triticum aestivum L.) was examined. Wheat was cultivated to grain production in soil amended with 0, 125, 250, and 500 mg of nCeO2/kg (control, nCeO2-L, nCeO2-M, and nCeO2-H, respectively). At harvest, grains and tissues were analyzed for mineral, fatty acid, and amino acid content. Results showed that, relative to the control, nCeO2-H improved plant growth, shoot biomass, and grain yield by 9.0%, 12.7%, and 36.6%, respectively. Ce accumulation in roots increased at increased nCeO2 concentration but did not change across treatments in leaves, hull, and grains, indicating a lack of Ce transport to the above-ground tissues. nCeO2 modified S and Mn storage in grains. nCeO2-L modified the amino acid composition and increased linolenic acid by up to 6.17% but decreased linoleic acid by up to 1.63%, compared to the other treatments. The findings suggest the potential of nanoceria to modify crop physiology and food quality with unknown consequences for living organisms.

  11. Cerium oxide nanoparticles inhibit the migration and proliferation of gastric cancer by increasing DHX15 expression.

    PubMed

    Xiao, Yu-Feng; Li, Jian-Mei; Wang, Su-Min; Yong, Xin; Tang, Bo; Jie, Meng-Meng; Dong, Hui; Yang, Xiao-Chao; Yang, Shi-Ming

    2016-01-01

    Gastric cancer is one of the leading causes of tumor-related deaths in the world. Current treatment options do not satisfy doctors and patients, and new therapies are therefore needed. Cerium oxide nanoparticles (CNPs) have been studied as a potential therapeutic approach for treating many diseases. However, their effects on human gastric cancer are currently unknown. Therefore, in this study, we aimed to characterize the effects of CNPs on human gastric cancer cell lines (MKN28 and BGC823). Gastric cancer cells were cocultured with different concentrations of CNPs, and proliferation and migration were measured both in vitro and in vivo. We found that CNPs inhibited the migration of gastric cancer cells when applied at different concentrations, but only a relatively high concentration (10 µg/mL) of CNPs suppressed proliferation. Furthermore, we found that CNPs increased the expression of DHX15 and its downstream signaling pathways. We therefore provide evidence showing that CNPs may be a promising approach to suppress malignant activity of gastric cancer by increasing the expression of DHX15.

  12. Role of phosphate on stability and catalase mimetic activity of cerium oxide nanoparticles.

    PubMed

    Singh, Ragini; Singh, Sanjay

    2015-08-01

    Cerium oxide nanoparticles (CeNPs) have been recently shown to scavenge reactive oxygen and nitrogen species (ROS and RNS) in different experimental model systems. CeNPs (3+) and CeNPs (4+) have been shown to exhibit superoxide dismutase (SOD) and catalase mimetic activity, respectively. Due to their nanoscale dimension, CeNPs are expected to interact with the components of biologically relevant buffers and medium, which could alter their catalytic properties. We have demonstrated earlier that CeNPs (3+) interact with phosphate and lose the SOD activity. However, very little is known about the interaction of CeNPs (4+) with the phosphate and other anions, predominantly present in biological buffers and their effects on the catalase mimetic-activity of these nanoparticles. In this study, we report that catalase mimetic-activity of CeNPs (4+) is resistant to the phosphate anions, pH changes and composition of cell culture media. Given the abundance of phosphate anions in the biological system, it is likely that internalized CeNPs would be influenced by cytoplasmic and nucleoplasmic concentration of phosphate.

  13. CO responses of sensors based on cerium oxide thick films prepared from clustered spherical nanoparticles.

    PubMed

    Izu, Noriya; Matsubara, Ichiro; Itoh, Toshio; Akamatsu, Takafumi; Shin, Woosuck

    2013-03-08

    Various types of CO sensors based on cerium oxide (ceria) have been reported recently. It has also been reported that the response speed of CO sensors fabricated from porous ceria thick films comprising nanoparticles is extremely high. However, the response value of such sensors is not suitably high. In this study, we investigated methods of improving the response values of CO sensors based on ceria and prepared gas sensors from core-shell ceria polymer hybrid nanoparticles. These hybrid nanoparticles have been reported to have a unique structure: The core consists of a cluster of ceria crystallites several nanometers in size. We compared the characteristics of the sensors based on thick films prepared from core-shell nanoparticles with those of sensors based on thick films prepared from conventionally used precipitated nanoparticles. The sensors prepared from the core-shell nanoparticles exhibited a resistance that was ten times greater than that of the sensors prepared from the precipitated nanoparticles. The response values of the gas sensors based on the core-shell nanoparticles also was higher than that of the sensors based on the precipitated nanoparticles. Finally, improvements in sensor response were also noticed after the addition of Au nanoparticles to the thick films used to fabricate the two types of sensors.

  14. Effects of cerium oxide nanoparticles on soil enzymatic activities and wheat grass nutrients uptake

    NASA Astrophysics Data System (ADS)

    Li, Biting; Chen, Yirui; Bai, Lingyun; Jacobson, Astrid; Darnault, Christophe

    2015-04-01

    The US National Science Foundation estimated that the use of nanomaterials and nanotechnology would reach a global market value of 1 million this year. Concomitant with the wide applications of nanoparticles is an increasing risk of adverse effects to the environment and human health. As a common nanomaterial used as a fuel catalyst and polish material, cerium (IV) oxide nanoparticles (CeO2 NP) were tested for their potential impact on soil health and plant growth. Through exposure by air, water, and solid deposition, nanoparticles may accumulate in soils and impact agricultural systems. The objectives of this research were to determine whether CeO2 NPs affect the growth of wheat grass and selected soil enzyme activities chose as indicators of soil health. Wheat grass was grown in plant boxes containing CeO2 NPs mixed with agricultural soil at different concentrations. Two control groups were included: one consisting of soil with plants but no CeO2 NPs, and one containing only soil, i.e., no NP or wheat plants added. The plants were grown for 10 weeks and harvested every two weeks in a laboratory under sodium growth lights. At the end of the each growing period, two weeks, soils were assayed for phosphatase, β-glucosidase, and urease activities, and NPK values. Spectrophotometer analyses were used to assess enzyme activities, and NPK values were tested by Clemson Agricultural Center. Wheat yields were estimated by shoot and root lengths and weights.

  15. Preparation and evaluation of cerium oxide-bovine hydroxyapatite composites for biomedical engineering applications.

    PubMed

    Gunduz, O; Gode, C; Ahmad, Z; Gökçe, H; Yetmez, M; Kalkandelen, C; Sahin, Y M; Oktar, F N

    2014-07-01

    The fabrication and characterization of bovine hydroxyapatite (BHA) and cerium oxide (CeO2) composites are presented. CeO2 (at varying concentrations 1, 5 and 10wt%) were added to calcinated BHA powder. The resulting mixtures were shaped into green cylindrical samples by powder pressing (350MPa) followed by sintering in air (1000-1300°C for 4h). Density, Vickers microhardness (HV), compression strength, scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies were performed on the products. The sintering behavior, microstructural characteristics and mechanical properties were evaluated. Differences in the sintering temperature (for 1wt% CeO2 composites) between 1200 and 1300°C, show a 3.3% increase in the microhardness (564 and 582.75HV, respectively). Composites prepared at 1300°C demonstrate the greatest compression strength with comparable results for 5 and 10wt% CeO2 content (106 and 107MPa) which are significantly better than those for 1wt% and those that do not include any CeO2 (90 and below 60MPa, respectively). The results obtained suggest optimal parameters to be used in preparation of BHA and CeO2 composites, while also highlighting the potential of such materials in several biomedical engineering applications.

  16. Effects of amorphous silica coating on cerium oxide nanoparticles induced pulmonary responses

    PubMed Central

    Ma, Jane; Mercer, Robert R.; Barger, Mark; Schwegler-Berry, Diane; Cohen, Joel M.; Demokritou, Philip; Castranova, Vincent

    2015-01-01

    Recently cerium compounds have been used in a variety of consumer products, including diesel fuel additives, to increase fuel combustion efficiency and decrease diesel soot emissions. However, cerium oxide (CeO2) nanoparticles have been detected in the exhaust, which raises a health concern. Previous studies have shown that exposure of rats to nanoscale CeO2 by intratracheal instillation (IT) induces sustained pulmonary inflammation and fibrosis. In the present study, male Sprague–Dawley rats were exposed to CeO2 or CeO2 coated with a nano layer of amorphous SiO2 (aSiO2/CeO2) by a single IT and sacrificed at various times post-exposure to assess potential protective effects of the aSiO2 coating. The first acellular bronchoalveolar lavage (BAL) fluid and BAL cells were collected and analyzed from all exposed animals. At the low dose (0.15 mg/kg), CeO2 but not aSiO2/CeO2 exposure induced inflammation. However, at the higher doses, both particles induced a dose-related inflammation, cytotoxicity, inflammatory cytokines, matrix metalloproteinase (MMP)-9, and tissue inhibitor of MMP at 1 day post-exposure. Morphological analysis of lung showed an increased inflammation, surfactant and collagen fibers after CeO2 (high dose at 3.5 mg/kg) treatment at 28 days post-exposure. aSiO2 coating significantly reduced CeO2-induced inflammatory responses in the airspace and appeared to attenuate phospholipidosis and fibrosis. Energy dispersive X-ray spectroscopy analysis showed Ce and phosphorous (P) in all particle-exposed lungs, whereas Si was only detected in aSiO2/CeO2-exposed lungs up to 3 days after exposure, suggesting that aSiO2 dissolved off the CeO2 core, and some of the CeO2 was transformed to CePO4 with time. These results demonstrate that aSiO2 coating reduce CeO2-induced inflammation, phospholipidosis and fibrosis. PMID:26210349

  17. Interactive effects of cerium oxide and diesel exhaust nanoparticles on inducing pulmonary fibrosis

    SciTech Connect

    Ma, Jane Y.C.; Young, Shih-Houng; Mercer, Robert R.; Barger, Mark; Schwegler-Berry, Diane; Ma, Joseph K.; Castranova, Vincent

    2014-07-15

    Cerium compounds have been used as a fuel-borne catalyst to lower the generation of diesel exhaust particles (DEPs), but are emitted as cerium oxide nanoparticles (CeO{sub 2}) along with DEP in the diesel exhaust. The present study investigates the effects of the combined exposure to DEP and CeO{sub 2} on the pulmonary system in a rat model. Specific pathogen-free male Sprague–Dawley rats were exposed to CeO{sub 2} and/or DEP via a single intratracheal instillation and were sacrificed at various time points post-exposure. This investigation demonstrated that CeO{sub 2} induces a sustained inflammatory response, whereas DEP elicits a switch of the pulmonary immune response from Th1 to Th2. Both CeO{sub 2} and DEP activated AM and lymphocyte secretion of the proinflammatory cytokines IL-12 and IFN-γ, respectively. However, only DEP enhanced the anti-inflammatory cytokine IL-10 production in response to ex vivo LPS or Concanavalin A challenge that was not affected by the presence of CeO{sub 2}, suggesting that DEP suppresses host defense capability by inducing the Th2 immunity. The micrographs of lymph nodes show that the particle clumps in DEP + CeO{sub 2} were significantly larger than CeO{sub 2} or DEP, exhibiting dense clumps continuous throughout the lymph nodes. Morphometric analysis demonstrates that the localization of collagen in the lung tissue after DEP + CeO{sub 2} reflects the combination of DEP-exposure plus CeO{sub 2}-exposure. At 4 weeks post-exposure, the histological features demonstrated that CeO{sub 2} induced lung phospholipidosis and fibrosis. DEP induced lung granulomas that were not significantly affected by the presence of CeO{sub 2} in the combined exposure. Using CeO{sub 2} as diesel fuel catalyst may cause health concerns. - Highlights: • DEP induced acute lung inflammation and switched immune response from Th1 to Th2. • DEP induced lung granulomas were not affected by the presence of CeO{sub 2}. • CeO{sub 2} induced sustained lung

  18. Effects of amorphous silica coating on cerium oxide nanoparticles induced pulmonary responses.

    PubMed

    Ma, Jane; Mercer, Robert R; Barger, Mark; Schwegler-Berry, Diane; Cohen, Joel M; Demokritou, Philip; Castranova, Vincent

    2015-10-01

    Recently cerium compounds have been used in a variety of consumer products, including diesel fuel additives, to increase fuel combustion efficiency and decrease diesel soot emissions. However, cerium oxide (CeO2) nanoparticles have been detected in the exhaust, which raises a health concern. Previous studies have shown that exposure of rats to nanoscale CeO2 by intratracheal instillation (IT) induces sustained pulmonary inflammation and fibrosis. In the present study, male Sprague-Dawley rats were exposed to CeO2 or CeO2 coated with a nano layer of amorphous SiO2 (aSiO2/CeO2) by a single IT and sacrificed at various times post-exposure to assess potential protective effects of the aSiO2 coating. The first acellular bronchoalveolar lavage (BAL) fluid and BAL cells were collected and analyzed from all exposed animals. At the low dose (0.15mg/kg), CeO2 but not aSiO2/CeO2 exposure induced inflammation. However, at the higher doses, both particles induced a dose-related inflammation, cytotoxicity, inflammatory cytokines, matrix metalloproteinase (MMP)-9, and tissue inhibitor of MMP at 1day post-exposure. Morphological analysis of lung showed an increased inflammation, surfactant and collagen fibers after CeO2 (high dose at 3.5mg/kg) treatment at 28days post-exposure. aSiO2 coating significantly reduced CeO2-induced inflammatory responses in the airspace and appeared to attenuate phospholipidosis and fibrosis. Energy dispersive X-ray spectroscopy analysis showed Ce and phosphorous (P) in all particle-exposed lungs, whereas Si was only detected in aSiO2/CeO2-exposed lungs up to 3days after exposure, suggesting that aSiO2 dissolved off the CeO2 core, and some of the CeO2 was transformed to CePO4 with time. These results demonstrate that aSiO2 coating reduce CeO2-induced inflammation, phospholipidosis and fibrosis.

  19. Cerium oxide nanoparticles alleviate oxidative stress and decreases Nrf-2/HO-1 in D-GALN/LPS induced hepatotoxicity.

    PubMed

    Hashem, Reem M; Rashd, Laila A; Hashem, Khalid S; Soliman, Hatem M

    2015-07-01

    Translocation of the master regulator of antioxidant-response element-driven antioxidant gene, nuclear factor erythroid 2 (Nrf-2) from the cytoplasm into the nucleus and triggering the transcription of hemoxygenase-1 (HO-1) to counteract the oxidative stress is a key feature in D-galactoseamine and lipopolysaccharide (D-GALN/LPS) induced hepatotoxicity. We mainly aimed to study the effect of cerium oxide (CeO2) nanoparticles on Nrf-2/HO-1 pathway whereas; it has previously shown to have an antioxidant effect in liver models. Administration of CeO2 nanoparticles significantly decreased the translocation of the cytoplasmic Nrf-2 with a concomitant decrement in the gene expression of HO-1 as it reveals a powerful antioxidative effect as indicated by the significant increase in the levels of glutathione (GSH), glutathione peroxidase (GPX1), glutathione reductase (GR), superoxide dismutase (SOD) and catalase. In synchronization, a substantial decrement in the levels of inducible nitric oxide synthase (iNOS), TBARS and percentage of DNA fragmentation was established. These results were confirmed by histopathology examination which showed a severe degeneration, haemorrhages, widened sinusoids and focal leukocyte infiltration in D-GALN/LPS treatment and these features were alleviated with CeO2 administration. In conclusion, CeO2 is a potential antioxidant that can effectively decrease the translocation of the cytoplasmic Nrf-2 into the nucleus and decrease HO-1 in D-GALN/LPS induced hepatotoxicity.

  20. Influence of the surface pre-treatment of aluminum on the processes of formation of cerium oxides protective films

    NASA Astrophysics Data System (ADS)

    Andreeva, R.; Stoyanova, E.; Tsanev, A.; Stoychev, D.

    2016-03-01

    It is known that there is special interest in the contemporary investigations on conversion treatment of aluminum aimed at promoting its corrosion stability, which is focused on electrolytes on the basis of salts of metals belonging to the group of rare-earth elements. Their application is especially attractive, as it enables a successful substitution of the presently applied highly efficient, but at the same time toxic Cr6+-containing electrolytes. The present paper presents a study on the influence of the preliminary alkaline activation and acidic de-oxidation of the aluminum surface on the processes of immersion formation of protective cerium oxides films on Al 1050. The results obtained show that their deposition from simple electrolytes (containing only salts of Ce3+ ions) on the Al surface, treated only in alkaline solution, occurs at a higher rate, which leads to preparing thicker oxide films having a better protective ability. In the cases when the formation of oxide films is realized in a complex electrolyte (containing salts of Ce3+ and Cu2+ ions), better results are obtained with respect to the morphology and protective action of cerium oxides film on samples that have been consecutively activated in alkaline solution and deoxidized in acidic solution. Electrochemical investigations were carried out in a model corrosion medium (0.1 M NaCl); it was shown that the cerium protective films, deposited by immersion, have a cathodic character with regard to the aluminum support and inhibit the occurrence of the depolarizing corrosion process -- the reaction of oxygen reduction.

  1. The impact of cerium oxide nanoparticles on the salt stress responses of Brassica napus L.

    PubMed

    Rossi, Lorenzo; Zhang, Weilan; Lombardini, Leonardo; Ma, Xingmao

    2016-12-01

    Dwindling high quality water resources and growing population are forcing growers to irrigate crops with water of high salinity. It is well recognized that salinity negatively affects plant physiology and biochemistry, and represents one of the most serious threats to crop production and food security. Meanwhile, engineered nanoparticles (ENPs) are increasingly detected in irrigation water and agricultural soils due to the rapid advancement of nanotechnology. Previous research has demonstrated that ENPs such as cerium oxide nanoparticles (CeO2-NPs) exert significant impact on plant growth and production. However, almost all previous studies were conducted in well controlled environment. Knowledge on how ENPs affect plant development in a stressed condition is almost empty. The goal of the present study was to understand the physiological and biochemical changes in Brassica napus L. (canola) cv. 'Dwarf Essex' under synergistic salt stress and CeO2-NPs effects. Two salinity levels: 0 (control) and 100 mM NaCl, and three CeO2-NPs concentrations: 0 (control), 200 and 1000 mg kg(-1) dry sand and clay mixture, were employed. As expected, 100 mM of NaCl significantly hindered plant growth and negatively affected the physiological processes of canola. Plants treated with CeO2-NPs had higher plant biomass, exhibited higher efficiency of the photosynthetic apparatus and less stress in both fresh water and saline water irrigation conditions Overall, our results demonstrated that CeO2-NPs led to changes in canola growth and physiology which improved the plant salt stress response but did not completely alleviate the salt stress of canola.

  2. Pulmonary toxicity of well-dispersed cerium oxide nanoparticles following intratracheal instillation and inhalation

    NASA Astrophysics Data System (ADS)

    Morimoto, Yasuo; Izumi, Hiroto; Yoshiura, Yukiko; Tomonaga, Taisuke; Oyabu, Takako; Myojo, Toshihiko; Kawai, Kazuaki; Yatera, Kazuhiro; Shimada, Manabu; Kubo, Masaru; Yamamoto, Kazuhiro; Kitajima, Shinichi; Kuroda, Etsushi; Kawaguchi, Kenji; Sasaki, Takeshi

    2015-11-01

    We performed inhalation and intratracheal instillation studies of cerium dioxide (CeO2) nanoparticles in order to investigate their pulmonary toxicity, and observed pulmonary inflammation not only in the acute and but also in the chronic phases. In the intratracheal instillation study, F344 rats were exposed to 0.2 mg or 1 mg of CeO2 nanoparticles. Cell analysis and chemokines in bronchoalveolar lavage fluid (BALF) were analyzed from 3 days to 6 months following the instillation. In the inhalation study, rats were exposed to the maximum concentration of inhaled CeO2 nanoparticles (2, 10 mg/m3, respectively) for 4 weeks (6 h/day, 5 days/week). The same endpoints as in the intratracheal instillation study were examined from 3 days to 3 months after the end of the exposure. The intratracheal instillation of CeO2 nanoparticles caused a persistent increase in the total and neutrophil number in BALF and in the concentration of cytokine-induced neutrophil chemoattractant (CINC)-1, CINC-2, chemokine for neutrophil, and heme oxygenase-1 (HO-1), an oxidative stress marker, in BALF during the observation time. The inhalation of CeO2 nanoparticles also induced a persistent influx of neutrophils and expression of CINC-1, CINC-2, and HO-1 in BALF. Pathological features revealed that inflammatory cells, including macrophages and neutrophils, invaded the alveolar space in both studies. Taken together, the CeO2 nanoparticles induced not only acute but also chronic inflammation in the lung, suggesting that CeO2 nanoparticles have a pulmonary toxicity that can lead to irreversible lesions.

  3. Molecular and physiological responses to titanium dioxide and cerium oxide nanoparticles in Arabidopsis.

    PubMed

    Tumburu, Laxminath; Andersen, Christian P; Rygiewicz, Paul T; Reichman, Jay R

    2017-01-01

    Changes in tissue transcriptomes and productivity of Arabidopsis thaliana were investigated during exposure of plants to 2 widely used engineered metal oxide nanoparticles, titanium dioxide (nano-titania) and cerium dioxide (nano-ceria). Microarray analyses confirmed that exposure to either nanoparticle altered the transcriptomes of rosette leaves and roots, with comparatively larger numbers of differentially expressed genes found under nano-titania exposure. Nano-titania induced more differentially expressed genes in rosette leaves, whereas roots had more differentially expressed genes under nano-ceria exposure. MapMan analyses indicated that although nano-titania up-regulated overall metabolism in both tissues, metabolic processes under nano-ceria remained mostly unchanged. Gene enrichment analysis indicated that both nanoparticles mainly enriched ontology groups such as responses to stress (abiotic and biotic), and defense responses (pathogens), and responses to endogenous stimuli (hormones). Nano-titania specifically induced genes associated with photosynthesis, whereas nano-ceria induced expression of genes related to activating transcription factors, most notably those belonging to the ethylene responsive element binding protein family. Interestingly, there were also increased numbers of rosette leaves and plant biomass under nano-ceria exposure, but not under nano-titania. Other transcriptomic responses did not clearly relate to responses observed at the organism level, possibly because of functional and genomic redundancy in Arabidopsis, which may mask expression of morphological changes, despite discernable responses at the transcriptome level. In addition, transcriptomic changes often relate to transgenerational phenotypic development, and hence it may be productive to direct further experimental work to integrate high-throughput genomic results with longer term changes in subsequent generations. Environ Toxicol Chem 2017;36:71-82. Published 2016 Wiley

  4. Stability and spinodal decomposition of the solid-solution phase in the ruthenium-cerium-oxide electro-catalyst.

    PubMed

    Li, Yanmei; Wang, Xin; Shao, Yanqun; Tang, Dian; Wu, Bo; Tang, Zhongzhi; Lin, Wei

    2015-01-14

    The phase diagram of Ru-Ce-O was calculated by a combination of ab initio density functional theory and thermodynamic calculations. The phase diagram indicates that the solubility between ruthenium oxide and cerium oxide is very low at temperatures below 1100 K. Solid solution phases, if existing under normal experimental conditions, are metastable and subject to a quasi-spinodal decomposition to form a mixture of a Ru-rich rutile oxide phase and a Ce-rich fluorite oxide phase. To study the spinodal decomposition of Ru-Ce-O, Ru0.6Ce0.4O2 samples were prepared at 280 °C and 450 °C. XRD and in situ TEM characterization provide proof of the quasi-spinodal decomposition of Ru0.6Ce0.4O2. The present study provides a fundamental reference for the phase design of the Ru-Ce-O electro-catalyst.

  5. Radioprotective cerium oxide nanoparticles: Molecular imaging investigations of conps' pharmacokinetics, efficacy, and mechanisms of action

    NASA Astrophysics Data System (ADS)

    McDonagh, Philip Reed Wills, III

    Cerium oxide nanoparticles (CONPs) are being investigated for several anti-oxidant applications in medicine. One of their most promising applications is as a radioprotective drug, an area of research in need due to the severe side effects from radiation therapy. In this work, the potential of CONPs as a radioprotective drug is examined using four criteria: favorable biodistribution/pharmacokinetics, low toxicity, ability to protect normal tissue from radiation damage, and lack of protection of tumor. The mechanisms of action of CONPs are also studied. Biodistribution was determined in radiolabeled CONPs with surface coatings including citrate, dextran T10-amine (DT10-NH2), dextran T10-polyethylene glycol (DT10-PEG), dextran T10-sulfobetaine (DT10-SB) and poly(acrylic acid) (PAA), and compared to uncoated. 89Zr was incorporated into CONPs for positron emission tomography (PET) imaging and ex vivo tissue analysis in tumor bearing mice. Compared to uncoated [ 89Zr]CONPs, coated [89Zr]CONPs showed improved biodistribution, including significantly enhanced renal clearance of PAA- [89Zr]CONPs. The toxicity of CONPs was evaluated in vitro and in vivo, with low toxicity at therapeutic doses. After clinically mimetic radiation therapy, pre-treatment of mice with coated and uncoated CONPs showed greater than 50% reduction of cell death in normal colon tissue, comparable to the clinically available radioprotective drug amifostine. Tumor control after irradiation of spontaneous colon tumors was unchanged with PAA-CONP pre-treatment, while citrate, DT10-PEG, and uncoated CONP pre-treatment had slightly less tumor control. Xenograft tumors were irradiated after pH normalizing treatment with sodium bicarbonate and PAA-CONP pre-treatment. Treatment of these tumors showed slightly less tumor control than irradiation alone or PAA-CONP plus irradiation, demonstrating that the acidic pH of the tumor microenvironment may be the basis of preventing CONPs' radioprotective properties in

  6. Imaging nanostructural modifications induced by electronic metal-support interaction effects at Au||cerium-based oxide nanointerfaces.

    PubMed

    López-Haro, Miguel; Cíes, José M; Trasobares, Susana; Pérez-Omil, José A; Delgado, Juan J; Bernal, Serafín; Bayle-Guillemaud, Pascale; Stéphan, Odile; Yoshida, Kenta; Boyes, Edward D; Gai, Pratibha L; Calvino, José J

    2012-08-28

    A variety of advanced (scanning) transmission electron microscopy experiments, carried out in aberration-corrected equipment, provide direct evidence about subtle structural changes taking place at nanometer-sized Au||ceria oxide interfaces, which agrees with the occurrence of charge transfer effects between the reduced support and supported gold nanoparticles suggested by macroscopic techniques. Tighter binding of the gold nanoparticles onto the ceria oxide support when this is reduced is revealed by the structural analysis. This structural modification is accompanied by parallel deactivation of the CO chemisorption capacity of the gold nanoparticles, which is interpreted in exact quantitative terms as due to deactivation of the gold atoms at the perimeter of the Au||cerium oxide interface.

  7. Complete oxidation of methane over Ag- and Cu-modified cerium and zirconium oxides

    NASA Astrophysics Data System (ADS)

    Kundakovic, Ljiljana

    Low temperature oxidation of methane is an area in catalysis that, despite the large number of catalytic systems studied, does not yet have an adequate solution. The exhaust gas from natural gas burning devices (gas turbines and natural gas vehicles), contains unconverted methane which is emitted into the atmosphere (currently unregulated). Methane is the most refractory of all hydrocarbons, and its activation requires temperatures higher than the typical exhaust temperatures (350-400sp°C). In this work, ceria- and zirconia-supported Ag and CuO catalysts were studied for the complete oxidation of methane. Catalysts were typically tested under excess oxygen and high space velocity (72,000 hsp{-1}). The reaction kinetics were measured over selected catalysts. Hsb2- and CHsb4- TPR and oxygen uptake measurements were used to characterize the catalyst reduction properties. XRD, STEM/EDX and HRTEM were used to characterize the catalyst structure. The oxidation state of various active species present was identified by XPS and UV-VIS DR spectrometry. Ceria- and zirconia-supported Ag and CuO catalysts are very active and stable catalysts for the complete oxidation of carbon monoxide and methane. When ceria is used as an active catalyst support, its activity depends strongly on its structure. Nanocrystalline ceria, stabilized by dopants such as La or Zr, is highly reducible and structurally defective. Our results indicate that surface oxygen species present under reaction conditions are the active sites for methane activation. Activity in the complete oxidation of methane is related to ceria crystal size and reducibility of surface oxygen species. The addition of a transition metal (Ag) or a metal oxide (CuO) in low amounts increases the low temperature reducibility of ceria and enhances the catalyst oxidation activity. On the other hand, both Ag and CuO are active catalysts for the complete oxidation of methane. These were studied separately on inert zirconia support. A

  8. Oxidative Stress, Inflammation, and DNA Damage Responses Elicited by Silver, Titanium Dioxide, and Cerium Oxide Nanomaterials

    EPA Science Inventory

    Previous literature on the biological effects of engineered nanomaterials has focused largely on oxidative stress and inflammation endpoints without further investigating potential pathways. Here we examine time-sensitive biological response pathways affected by engineered nanoma...

  9. Nafion-porous cerium oxide nanotubes composite membrane for polymer electrolyte fuel cells operated under dry conditions

    NASA Astrophysics Data System (ADS)

    Ketpang, Kriangsak; Oh, Kwangjin; Lim, Sung-Chul; Shanmugam, Sangaraju

    2016-10-01

    A composite membrane operated in polymer electrolyte fuel cells (PEFCs) under low relative humidity (RH) is developed by incorporating cerium oxide nanotubes (CeNT) into a perfluorosulfonic acid (Nafion®) membrane. Porous CeNT is synthesized by direct heating a precursor impregnated polymer fibers at 500 °C under an air atmosphere. Compared to recast Nafion and commercial Nafion (NRE-212) membranes, the Nafion-CeNT composite membrane generates 1.1 times higher power density at 0.6 V, operated at 80 °C under 100% RH. Compared to Nafion-cerium oxide nanoparticles (Nafion-CeNP) membrane, the Nafion-CeNT provides 1.2 and 1.7 times higher PEFC performance at 0.6 V when operated at 80 °C under 100% and 18% RH, respectively. Additionally, the Nafion-CeNT composite membrane exhibits a good fuel cell operation under 18% RH at 80 °C. Specifically, the fluoride emission rate of Nafion-CeNT composite membrane is 20 times lower than that of the commercial NRE-212 membrane when operated under 18% RH at 80 °C for 96 h. The outstanding PEFC performance and durability operated under dry conditions is mainly attributed to the facile water diffusion capability as well as the effective hydroxyl radical scavenging property of the CeNT filler, resulting in significantly mitigating both the ohmic resistance and Nafion membrane degradation.

  10. Catalytic wet oxidation of 2,4-dichlorophenol solutions: activity of the manganese-cerium composite catalyst and biodegradability of the effluent stream.

    PubMed

    Lee, Bing-Nan; Lou, Jie-Chung; Yen, Po-Chung

    2002-01-01

    Aqueous solutions containing 100 to 1000 mg/L of 2,4-dichlorophenol (2,4-DCP) were oxidized in an upflowing fixed-bed reactor in this study of manganese-cerium composite catalysts, which were prepared by the coprecipitation of both manganese nitrate and ceric nitrate at various molar concentrations. Results showed that 2,4-DCP conversion by wet oxidation in the presence of the manganese-cerium composite catalysts was a function of the molar ratio of the manganese-cerium catalyst. The kinetic behavior of 2,4-DCP oxidation with catalysis could be explained by using a zero-order rate expression. Total organic carbon (TOC) removal by wet oxidation in the absence of any catalyst was nil, while approximately 68% TOC reduction was achieved during wet oxidation over a manganese-cerium (7:3 mol/mol) catalyst at 160 degrees C and an oxygen partial pressure of 1.0 MPa. Moreover, the 5-day biochemical oxygen demand/chemical oxygen demand ratios of all the effluent streams were determined to be greater than 0.45 as the wet catalytic processes were carried out at a liquid hourly space velocity less than 24 h (-1), indicating that they could be made more amenable to further biological treatment.

  11. Anti-cancer effects of cerium oxide nanoparticles and its intracellular redox activity.

    PubMed

    Pešić, Milica; Podolski-Renić, Ana; Stojković, Sonja; Matović, Branko; Zmejkoski, Danica; Kojić, Vesna; Bogdanović, Gordana; Pavićević, Aleksandra; Mojović, Miloš; Savić, Aleksandar; Milenković, Ivana; Kalauzi, Aleksandar; Radotić, Ksenija

    2015-05-05

    Data on medical applications of cerium oxide nanoparticles CeO2 (CONP) are promising, yet information regarding their action in cells is incomplete and there are conflicting reports about in vitro toxicity. Herein, we have studied cytotoxic effect of CONP in several cancer and normal cell lines and their potential to change intracellular redox status. The IC50 was achieved only in two of eight tested cell lines, melanoma 518A2 and colorectal adenocarcinoma HT-29. Self-propagating room temperature method was applied to produce CONP with an average crystalline size of 4 nm. The results confirmed presence of Ce(3+) and O(2-) vacancies. The induction of cell death by CONP and the production of reactive oxygen species (ROS) were analyzed by flow-cytometry. Free radicals related antioxidant capacity of the cells was studied by the reduction of stable free radical TEMPONE using electron spin resonance spectroscopy. CONP showed low or moderate cytotoxicity in cancer cell lines: adenocarcinoma DLD1 and multi-drug resistant DLD1-TxR, non-small cell lung carcinoma NCI-H460 and multi-drug resistant NCI-H460/R, while normal cell lines (keratinocytes HaCaT, lung fetal fibroblasts MRC-5) were insensitive. The most sensitive were 518A2 melanoma and HT-29 colorectal adenocarcinoma cell lines, with the IC50 values being between 100 and 200 μM. Decreased rate of TEMPONE reduction and increased production of certain ROS species (peroxynitrite and hydrogen peroxide anion) indicates that free radical metabolism, thus redox status was changed, and antioxidant capacity damaged in the CONP treated 518A2 and HT-29 cells. In conclusion, changes in intracellular redox status induced by CONP are partly attributed to the prooxidant activity of the nanoparticles. Further, ROS induced cell damages might eventually lead to the cell death. However, low inhibitory potential of CONP in the other human cell lines tested indicates that CONP may be safe for human usage in industry and medicine.

  12. Genotoxicity assessment of cerium oxide nanoparticles in female Wistar rats after acute oral exposure.

    PubMed

    Kumari, Monika; Kumari, Srinivas Indu; Kamal, Sarika Srinivas Kalyan; Grover, Paramjit

    2014-12-01

    Cerium oxide nanoparticles (CeO2 NPs; nanoceria) have demonstrated excellent potential for commercial use in various arenas, such as in biomedical industry in cosmetics and as a fuel additive. However, limited knowledge exists regarding their potential toxicity. In this study, acute oral toxicity of CeO2 NPs and their microparticles (MPs; bulk) was carried out in female albino Wistar rats. The CeO2 NPs and CeO2 MPs were characterized utilizing transmission electron microscopy (TEM), dynamic light scattering (DLS) and laser Doppler velocimetry (LDV) for the size, distribution and surface charge respectively. The genotoxicity studies were conducted using micronucleus test (MNT), comet and chromosomal aberration (CA) assays. Results revealed that at high dose (1000mg/kg bw) CeO2 NPs induced significant DNA damage in peripheral blood leukocytes (PBL) and liver cells, micronucleus formation in bone marrow and blood cells and total cytogenetic changes in bone marrow. However, significant genotoxicity was not observed at 500 and 100mg/kg bw of CeO2 NPs. The findings from biochemical assays depicted significant alterations in ALP and LDH activity in serum and GSH content in liver, kidneys and brain only at the high dose of CeO2 NPs. Tissue biodistribution of both particles was analyzed by inductively coupled plasma optical emission spectrometer (ICP-OES). Bioaccumulation of nanoceria in all tissues was significant and dose-, time- and organ-dependent. Moreover, CeO2 NPs exhibited higher tissue distribution along with greater clearance in large fractions through urine and feces than CeO2 bulk, whereas, maximum amount of micro-sized CeO2 got excreted in feces. The histopathological examination documented alterations in the liver due to exposure with CeO2 NPs only. Hence, the results suggest that bioaccumulation of CeO2 NPs may induce genotoxic effects. However, further research on long term fate and adverse effects of CeO2 NPs is warranted.

  13. SU-E-T-279: Dose Enhancement Effect Due to Cerium Oxide Nanoparticles Employed as Radiation Protectants

    SciTech Connect

    Ouyang, Z; Altundal, Y; Sajo, E; Ngwa, W

    2015-06-15

    Purpose: The goal of radiotherapy is to maximize radiation dose to diseased cells while minimizing radiation damage to normal tissues. In order to minimize damage to normal tissues, cerium oxide nanoparticles (nanoceria) are currently considered as a radioprotectant. However, some studies have reported concerns that nanoceria can also lead to radiotherapy dose enhancement due to the high atomic number of cerium, especially when used in conjunction with kV energy and brachytherapy sources. In this study, this concern is investigated to determine if the concentrations of nanoceria employed in in-vivo studies to confer radioprotection can engender a significant dose enhancement. Methods: Radiation with energies ranging from 50kVp to 140kVp is investigated in this work along with brachytherapy sources Pd-103 and I-125. A previously established theoretical model is used to calculate the dose enhancement factor (DEF). In this model, each cell is assumed to be a voxel of size (10 µm, 10 µm, 10 µm) with nanoceria homogeneously distributed among them. Electron energy loss formula of Cole is used to calculate energy (and hence dose) deposited by photoelectrons and Auger electrons in each tissue voxel due to irradiation of nanoceria. The DEF is defined as the ratio of the dose with and without nanoparticles. Results: DEF calculation results are smaller than 1.02 with dosages of nanoceria smaller than 0.645 mg/g, which is shown to be sufficiently protective by some previous in-vitro and in-vivo experiments. The brachytherapy sources show higher DEF’s than kVp radiations. DEF peaks are consistent with K shell and L shell energies of cerium, 40 keV and 6 keV, respectively. Conclusion: The results show that for sufficiently radioprotective concentrations of nanoceria, there will be minimal DEF when used in conjunction with clinically applicable kV energy radiotherapy sources or brachytherapy sources.

  14. Oxidation of SO2 to SO3 by Cerium Oxide Cluster Cations Ce2O4(+) and Ce3O6(.).

    PubMed

    Zhou, Zhen-Xun; Wang, Li Na; Li, Zi-Yu; He, Sheng-Gui; Ma, Tong-Mei

    2016-06-09

    Cerium oxide cationic clusters (CeO2)1-3(+) were generated through laser ablation and then reacted with sulfur dioxide (SO2) at ambient conditions in an ion trap reactor and those reactions were studied and characterized by combining the art of time-of-flight mass spectrometry (TOF-MS) with density functional theory (DFT) calculations. Molecule association and oxygen atom transfer (OAT) were observed for the CeO2(+) and (CeO2)2,3(+) reaction systems, respectively. The mechanistic analysis indicates that the weak Ce-O bond strength associated with the oxygen release capacity of cerium oxide clusters is considered as the key factor to achieve the oxidation of SO2. To our best knowledge, this research should be the first example to identify the OAT reactivity of metal oxide cluster ions toward sulfur dioxide under thermal collision conditions, and a fundamental understanding of the elementary oxidation of SO2 to SO3 is provided.

  15. The Chemical Behavior and Degradation Mitigation Effect of Cerium Oxide Nanoparticles in Perfluorosulfonic Acid Polymer Electrolyte Membranes

    SciTech Connect

    Pearman, Benjamin P; Mohajeri, Nahid; Slattery, Darlene; Hampton, Michael; Seal, Sudipta; Cullen, David A

    2013-01-01

    Perfluorosulfonic acid membranes, the polymer of choice for polymer electrolyte hydrogen fuel cells, are susceptible to degradation due to attacks on polymer chains from radicals. Mitigation of this attack by cerium-based radical scavengers is an approach that has shown promise. In this work, two formulations of single-crystal cerium oxide nanoparticles, with an order of magnitude difference in particle size, are incorporated into said membranes and subjected to proton conductivity measurements and ex-situ durability tests. We found that ceria is reduced to Ce(III) ions in the acidic environment of a heated, humidified membrane which negatively impacts proton conductivity. In liquid and gas Fenton testing, fluoride emission is reduced by an order of magnitude, drastically increasing membrane longevity. Side-product analysis demonstrated that in the liquid Fenton test, the main point of attack are weak polymer end groups, while in the gas Fenton test, there is additional side-chain attack. Both mechanisms are mitigated by the addition of the ceria nanoparticles, whereby the extent of the durability improvement is found to be independent of particle size.

  16. Structural analysis of nickel doped cerium oxide catalysts for fuel reforming in solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Cavendish, Rio

    As world energy demands increase, research into more efficient energy production methods has become imperative. Heterogeneous catalysis and nanoscience are used to promote chemical transformations important for energy production. These concepts are important in solid oxide fuel cells (SOFCs) which have attracted attention because of their potential to provide an efficient and environmentally favorable power generation system. The SOFC is also fuel-flexible with the ability to run directly on many fuels other than hydrogen. Internal fuel reforming directly in the anode of the SOFC would greatly reduce the cost and complexity of the device. Methane is the simplest hydrocarbon and a main component in natural gas, making it useful when testing catalysts on the laboratory scale. Nickel (Ni) and gadolinium (Gd) doped ceria (CeO 2) catalysts for potential use in the SOFC anode were synthesized with a spray drying method and tested for catalytic performance using partial oxidation of methane and steam reforming. The relationships between catalytic performance and structure were then investigated using X-ray diffraction, transmission electron microscopy, and environmental transmission electron microscopy. The possibility of solid solutions, segregated phases, and surface layers of Ni were explored. Results for a 10 at.% Ni in CeO2 catalyst reveal a poor catalytic behavior while a 20 at.% Ni in CeO2 catalyst is shown to have superior activity. The inclusion of both 10 at.% Gd and 10 at.% Ni in CeO2 enhances the catalytic performance. Analysis of the presence of Ni in all 3 samples reveals Ni heterogeneity and little evidence for extensive solid solution doping. Ni is found in small domains throughout CeO2 particles. In the 20 at.% Ni sample a segregated, catalytically active NiO phase is observed. Overall, it is found that significant interaction between Ni and CeO2 occurs that could affect the synthesis and functionality of the SOFC anode.

  17. Laser induced densification of cerium gadolinium oxide: Application to single-chamber solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Mariño, Mariana; Rieu, Mathilde; Viricelle, Jean-Paul; Garrelie, Florence

    2016-06-01

    In single-chamber solid oxide fuel cells (SC-SOFC), anode and cathode are placed in a gas chamber where they are exposed to a fuel/air mixture. Similarly to conventional dual-chamber SOFC, the anode and the cathode are separated by an electrolyte. However, as in the SC-SOFC configuration the electrolyte does not play tightness role between compartments, this one can be a porous layer. Nevertheless, it is necessary to have a diffusion barrier to prevent the transportation of hydrogen produced locally at the anode to the cathode that reduces fuel cell performances. This study aims to obtain directly a diffusion barrier through the surface densification of the electrolyte Ce0.9Gd0.1O1.95 (CGO) by a laser treatment. KrF excimer laser and Yb fiber laser irradiations were used at different fluences and number of pulses to modify the density of the electrolyte coating. Microstructural characterizations confirmed the modifications on the surface of the electrolyte for appropriate experimental conditions showing either grain growth or densified but cracked surfaces. Gas permeation and electrical conductivities of the modified electrolyte were evaluated. Finally SC-SOFC performances were improved for the cells presenting grain growth at the electrolyte surface.

  18. Preliminary study of phosphate adsorption onto cerium oxide nanoparticles for use in water purification; nanoparticles synthesis and characterization.

    PubMed

    Recillas, Sonia; García, Ana; González, Edgar; Casals, Eudald; Puntes, Victor; Sánchez, Antoni; Font, Xavier

    2012-01-01

    In this study, the synthesis and characterization of cerium oxide nanoparticles (CeO(2)-NPs) and their adsorption potential for removing phosphate from water was evaluated using a multi-factor experimental design to explore the effect of various factors on adsorption. The objective function selected was the percentage of phosphate removed from water, in which the phosphate concentration and the CeO(2)-NP concentration are quantitative variables (factors in the experimental design). A lineal polynomial fitted the experimental results well (R(2) = 0.9803). The nanostructure was studied by transmission electron microscopy (TEM) and high-resolution TEM techniques before and after the adsorption process. During the adsorption and desorption processes several changes in the morphology and surface chemistry of the CeO(2)-NPs were observed.

  19. Evaluation of the effect of valence state on cerium oxide nanoparticle toxicity following intratracheal instillation in rats

    PubMed Central

    Dunnick, Katherine M.; Morris, Anna M.; Badding, Melissa A.; Barger, Mark; Stefaniak, Aleksandr B.; Sabolsky, Edward M.; Leonard, Stephen S.

    2016-01-01

    Cerium (Ce) is becoming a popular metal for use in electrochemical applications. When in the form of cerium oxide (CeO2), Ce can exist in both 3 + and 4 + valence states, acting as an ideal catalyst. Previous in vitro and in vivo evidence have demonstrated that CeO2 has either anti- or pro-oxidant properties, possibly due to the ability of the nanoparticles to transition between valence states. Therefore, we chose to chemically modify the nanoparticles to shift the valence state toward 3+. During the hydrothermal synthesis process, 10 mol% gadolinium (Gd) and 20 mol% Gd, were substituted into the lattice of the CeO2 nanoparticles forming a perfect solid solution with various A-site valence states. These two Gd-doped CeO2 nanoparticles were compared to pure CeO2 nanoparticles. Preliminary characteristics indicated that doping results in minimal size and zeta potential changes but alters valence state. Following characterization, male Sprague-Dawley rats were exposed to 0.5 or 1.0 mg/kg nanoparticles via a single intratracheal instillation. Animals were sacrificed and bronchoalveolar lavage fluid and various tissues were collected to determine the effect of valence state and oxygen vacancies on toxicity 1-, 7-, or 84-day post-exposure. Results indicate that damage, as measured by elevations in lactate dehydrogenase, occurred within 1-day post-exposure and was sustained 7-day post-exposure, but subsided to control levels 84-day post-exposure. Furthermore, no inflammatory signaling or lipid peroxidation occurred following exposure with any of the nanoparticles. Our results implicate that valence state has a minimal effect on CeO2 nanoparticle toxicity in vivo. PMID:26898289

  20. Stability and mobility of cerium oxide nanoparticles in soils: effects of humic substances, pH and ionic strength

    NASA Astrophysics Data System (ADS)

    Chen, Yirui; Mu, Linlin; Li, Chunyan; Bai, Lingyun; Jacobson, Astrid; Darnault, Christophe

    2015-04-01

    Among the large number of types of nanomaterials used in the field of nanotechnology, cerium oxide nanoparticles (CeO2 NPs) are among the top five most commonly utilized by industry, agriculture and nanomedicine for their unique physico-chemical properties. They are used, for example, in the production of catalysts, as fuel additives, and as polishing agents. Therefore, the release and encounter of CeO2 NPs in the environment following their application, waste disposal, life-cycle and accidents is inevitable. It is critical to examine the behavior of CeO2 NPs released in the environment to assess the risk they pose to the environmental and public health. In particular, little is known about the fate and transport of CeO2 NPs in soils and groundwater. To assess the behavior of CeO2 NPs, it is important to investigate the factors that affect their stability and mobility. Humic substances are a major component of soils and have been shown to have the potential to impact the transport and retention of nanoparticles in soils. Consequently, our study characterizes the impacts of humic and fulvic acids on the stability and mobility of cerium oxides in model porous media under various pH and ionic strength conditions. Batch experiments conducted at various concentrations of humic and fulvic acids coupled with a wide range of pHs and ionic strengths were investigated. Selected parameters from these batch studies were then used as experimental conditions representative of environmental systems to perform column transport experiments to assess of the mobility of CeO2 NPs in saturated porous media, which is the first step in simulating their behavior in soil and groundwater systems.

  1. Influence of alloy content and a cerium surface treatment on the oxidation behavior of Fe-Cr ferritic stainless steels

    SciTech Connect

    Alman, D.E.; Jablonski, P.D.

    2006-01-01

    The cost of solid oxide fuel cells (SOFC) can be significantly reduced by using interconnects made from ferritic stainless steels. In fact, several alloys have been developed specifically for this application (Crofer 22APU and Hitachi ZMG323). However, these steels lack environmental stability in SOFC environments, and as a result, degrade the performance of the SOFC. A steel interconnect can contribute to performance degradation through: (i) Cr poisoning of electrochemically active sites within the cathode; (ii) formation of non-conductive oxides, such as SiO2 or Al2O3 from residual or minor alloying elements, at the base metal-oxide scale interface; and/or (iii) excessive oxide scale growth, which may also retard electrical conductivity. Consequently, there has been considerable attention on developing coatings to protect steel interconnects in SOFC environments and controlling trace elements during alloy production. Recently, we have reported on the development of a Cerium surface treatment that improves the oxidation behavior of a variety alloys, including Crofer 22APU [1-5]. Initial results indicated that the treatment may improve the performance of Crofer 22APU for SOFC application by: (i) retarding scale growth resulting in a thinner oxide scale; and (ii) suppressing the formation of a deleterious continuous SiO2 layer that can form at the metal-oxide scale interface in materials with high residual Si content [5]. Crofer 22 APU contains Fe-22Cr-0.5Mn-0.1Ti (weight percent). Depending on current market prices and the purity of raw materials utilized for ingot production, Cr can contribute upwards of 90 percent of the raw materials cost. The present research was undertaken to determine the influence of Cr content and minor element additions, especially Ti, on the effectiveness of the Ce surface treatment. Particular emphasis is placed on the behavior of low Cr alloys.

  2. Cerium oxide nanoparticles promote neurogenesis and abrogate hypoxia-induced memory impairment through AMPK-PKC-CBP signaling cascade.

    PubMed

    Arya, Aditya; Gangwar, Anamika; Singh, Sushil Kumar; Roy, Manas; Das, Mainak; Sethy, Niroj Kumar; Bhargava, Kalpana

    2016-01-01

    Structural and functional integrity of the brain is adversely affected by reduced oxygen saturation, especially during chronic hypoxia exposure and often encountered by altitude travelers or dwellers. Hypoxia-induced generation of reactive nitrogen and oxygen species reportedly affects the cortex and hippocampus regions of the brain, promoting memory impairment and cognitive dysfunction. Cerium oxide nanoparticles (CNPs), also known as nanoceria, switch between +3 and +4 oxidation states and reportedly scavenge superoxide anions, hydrogen peroxide, and peroxynitrite in vivo. In the present study, we evaluated the neuroprotective as well as the cognition-enhancing activities of nanoceria during hypobaric hypoxia. Using polyethylene glycol-coated 3 nm nanoceria (PEG-CNPs), we have demonstrated efficient localization of PEG-CNPs in rodent brain. This resulted in significant reduction of oxidative stress and associated damage during hypoxia exposure. Morris water maze-based memory function tests revealed that PEG-CNPs ameliorated hypoxia-induced memory impairment. Using microscopic, flow cytometric, and histological studies, we also provide evidences that PEG-CNPs augmented hippocampus neuronal survival and promoted neurogenesis. Molecular studies revealed that PEG-CNPs promoted neurogenesis through the 5'-adenine monophosphate-activated protein kinase-protein kinase C-cyclic adenosine monophosphate response element-binding protein binding (AMPK-PKC-CBP) protein pathway. Our present study results suggest that nanoceria can be translated as promising therapeutic molecules for neurodegenerative diseases.

  3. Cerium oxide nanoparticles promote neurogenesis and abrogate hypoxia-induced memory impairment through AMPK–PKC–CBP signaling cascade

    PubMed Central

    Arya, Aditya; Gangwar, Anamika; Singh, Sushil Kumar; Roy, Manas; Das, Mainak; Sethy, Niroj Kumar; Bhargava, Kalpana

    2016-01-01

    Structural and functional integrity of the brain is adversely affected by reduced oxygen saturation, especially during chronic hypoxia exposure and often encountered by altitude travelers or dwellers. Hypoxia-induced generation of reactive nitrogen and oxygen species reportedly affects the cortex and hippocampus regions of the brain, promoting memory impairment and cognitive dysfunction. Cerium oxide nanoparticles (CNPs), also known as nanoceria, switch between +3 and +4 oxidation states and reportedly scavenge superoxide anions, hydrogen peroxide, and peroxynitrite in vivo. In the present study, we evaluated the neuroprotective as well as the cognition-enhancing activities of nanoceria during hypobaric hypoxia. Using polyethylene glycol-coated 3 nm nanoceria (PEG-CNPs), we have demonstrated efficient localization of PEG-CNPs in rodent brain. This resulted in significant reduction of oxidative stress and associated damage during hypoxia exposure. Morris water maze-based memory function tests revealed that PEG-CNPs ameliorated hypoxia-induced memory impairment. Using microscopic, flow cytometric, and histological studies, we also provide evidences that PEG-CNPs augmented hippocampus neuronal survival and promoted neurogenesis. Molecular studies revealed that PEG-CNPs promoted neurogenesis through the 5′-adenine monophosphate-activated protein kinase–protein kinase C–cyclic adenosine monophosphate response element-binding protein binding (AMPK-PKC-CBP) protein pathway. Our present study results suggest that nanoceria can be translated as promising therapeutic molecules for neurodegenerative diseases. PMID:27069362

  4. Carbon nanotubes supported cerium dioxide and platinum nanohybrids: Layer-by-layer synthesis and enhanced electrocatalytic activity for methanol oxidation

    NASA Astrophysics Data System (ADS)

    Lou, Xinyuan; Chen, Jiayi; Wang, Mengdi; Gu, Jialei; Wu, Ping; Sun, Dongmei; Tang, Yawen

    2015-08-01

    We successfully synthesize carbon nanotubes (CNTs) supported cerium dioxide and platinum (Pt/CeO2/CNTs) nanohybrids via layer-by-layer assembly. The composition, morphology and structure of the as-prepared Pt/CeO2/CNTs nanohybrids are characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectrometer (EDX), selected-area electron diffraction (SAED), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and inductively coupled plasma atomic emission spectrometry (ICP-AES). By comparison of the electrocatalytic properties of the Pt/CeO2/CNTs with the Pt/CNTs, we systematically investigate the promotion effect of CeO2 on the Pt/CeO2/CNTs catalysts towards methanol oxidation. It is found that the introduction of CeO2 not only enhances the electrocatalytic activity and stability of the Pt/CeO2/CNTs catalyst for methanol oxidation but also minimizes the CO poisoning, probably accounting for the good oxygen carrying capacity of CeO2 and its high stability in acidic solution.

  5. Elimination of Flammable Gas Effects in Cerium Oxide Semiconductor-Type Resistive Oxygen Sensors for Monitoring Low Oxygen Concentrations

    PubMed Central

    Itoh, Toshio; Izu, Noriya; Akamatsu, Takafumi; Shin, Woosuck; Miki, Yusuke; Hirose, Yasuo

    2015-01-01

    We have investigated the catalytic layer in zirconium-doped cerium oxide, Ce0.9Zr0.1O2 (CeZr10) resistive oxygen sensors for reducing the effects of flammable gases, namely hydrogen and carbon monoxide. When the concentration of flammable gases is comparable to that of oxygen, the resistance of CeZr10 is affected by the presence of these gases. We have developed layered thick films, which consist of an oxygen sensor layer (CeZr10), an insulation layer (Al2O3), and a catalytic layer consisting of CeZr10 with 3 wt% added platinum, which was prepared via the screen printing method. The Pt-CeZr10 catalytic layer was found to prevent the detrimental effects of the flammable gases on the resistance of the sensor layer. This effect is due to the catalytic layer promoting the oxidation of hydrogen and carbon monoxide through the consumption of ambient O2 and/or the lattice oxygen atoms of the Pt-CeZr10 catalytic layer. PMID:25905705

  6. Effects of lanthanum, cerium, and neodymium on the nuclei and mitochondria of hepatocytes: accumulation and oxidative damage.

    PubMed

    Huang, Peili; Li, Jianxin; Zhang, Shuhua; Chen, Chunxia; Han, Ying; Liu, Na; Xiao, Yang; Wang, Hui; Zhang, Man; Yu, Qiuhong; Liu, Yuting; Wang, Wei

    2011-01-01

    The aim of this study was to investigate the contents of lanthanum (La), cerium (Ce), and neodymium (Nd) that accumulate in nuclei and mitochondria isolated from the liver and their corresponding potential oxidative damage effects on nuclei and mitochondria. Five-week-old male imprinting control region (ICR) mice were exposed to chlorides of La, Ce, or Nd by oral gavage with one of three doses: 10, 20, or 40 mg/kgBW/day for 6 weeks. The concentrations of administered elements in hepatocyte nuclei and mitochondria were determined with inductively coupled plasma-mass (ICP-MS) spectrometry. The accumulation of La, Ce, and Nd in hepatocyte nuclei and mitochondria gradually increased in a dose-dependent manner with exposure to the elements, although the concentrations of La, Ce, and Nd in hepatocyte mitochondria were lower than those in their counterpart nuclei. In hepatocyte nuclei, superoxide dismutase (SOD) and catalase (CAT) activities decreased, whereas glutathione peroxidase (GPx) activity, glutathione (GSH) and malondialdehyde (MDA) levels increased. In hepatocyte mitochondria, SOD, CAT, and GPx activities and GSH levels were significantly decreased, and MDA levels were significantly increased. These results suggest that La, Ce, and Nd presumably enter hepatocytes and mainly accumulate in the nuclei and induce oxidative damage in hepatic nuclei and mitochondria.

  7. Modulation of surface structure and catalytic properties of cerium oxide nanoparticles by thermal and microwave synthesis techniques

    NASA Astrophysics Data System (ADS)

    He, Jian; Zhou, Lan; Liu, Jie; Yang, Lu; Zou, Ling; Xiang, Junyu; Dong, Shiwu; Yang, Xiaochao

    2017-04-01

    Cerium oxide nanoparticles (CNPs) have been intensively explored for biomedical applications in recent few years due to the versatile enzyme mimetic activities of the nanoparticles. However, the control of CNPs quality through the optimization of synthesis conditions remains largely unexplored as most of the previous studies only focus on utilizing the catalytic activities of the nanoparticles. In the present study, CNPs with size about 5 nm were synthesized by thermal decomposition method using traditional convective heating and recently developed microwave irradiation as heating source. The quality of CNPs synthesized by the two heating manner was evaluated. The CNPs synthesized by convective heating were slightly smaller than that synthesized by microwave irradiation heating. The cores of the CNPs synthesized by the two heating manner have similar crystal structure. While the surface subtle structures of the CNPs synthesized by two heating manner were different. The CNPs synthesized by microwave irradiation have more surface reactive hot spot than that synthesized by convective heating as the nanoparticles responded more actively to the redox environment variation. This difference resulted in the higher superoxide dismutase (SOD) mimetic activity of CNPs synthesized by microwave irradiation heating than that of the convective heating. Preliminary experiments indicated that the CNPs synthesized by microwave irradiation heating could better protect cells from oxidative stress due to the higher SOD mimetic activity of the nanoparticles.

  8. Evaluation of cerium oxide coated Cu cermets as inert anodes for aluminum electrowinning. Final report, August 1990--March 1992

    SciTech Connect

    Not Available

    1992-08-01

    Cu/NiFe{sub 2}O{sub 4} cermets were evaluated, with and without an in-situ deposited CEROX (TM; cerium oxide) coating, in 100 h laboratory A1 electrowinning tests. Bath ratio and current density were varied between tests and corrosion was determined by contamination of the aluminum and cryolite by cermet components (Cu, Fe, and Ni). Higher bath ratios of 1.5 to 1.6 led to less corrosion and thicker CEROX coatings. Lower current densities led to slightly less corrosion but much less oxidation of the Cu cermet substrate. At identical test conditions, the corrosion of the CEROX coated cermets was 1/7 that of an uncoated cermet. Corrosion was increased in CEROX coated cermets tested under unsaturated alumina conditions. The electrical conductivity of the CEROX coating was measured to be {approximately}0.2 ohm{sup {minus}1}cm{sup {minus}1}, resulting in a slight voltage penalty, depending on the thickness of the coating.

  9. Combination of conventional chemotherapeutics with redox-active cerium oxide nanoparticles--a novel aspect in cancer therapy.

    PubMed

    Sack, Maren; Alili, Lirija; Karaman, Elif; Das, Soumen; Gupta, Ankur; Seal, Sudipta; Brenneisen, Peter

    2014-07-01

    Nanotechnology is becoming an important field of biomedical and clinical research and the application of nanoparticles in disease may offer promising advances in treatment of many diseases, especially cancer. Malignant melanoma is one of the most aggressive forms of cancer and its incidence is rapidly increasing. Redox-active cerium oxide nanoparticles (CNP) are known to exhibit significant antitumor activity in cells derived from human skin tumors in vitro and in vivo, whereas CNP is nontoxic and beyond that even protective (antioxidative) in normal, healthy cells of the skin. As the application of conventional chemotherapeutics is associated with harmful side effects on healthy cells and tissues, the clinical use is restricted. In this study, we addressed the question of whether CNP supplement a classical chemotherapy, thereby enhancing its efficiency without additional damage to normal cells. The anthracycline doxorubicin, one of the most effective cancer drugs, was chosen as reference for a classical chemotherapeutic agent in this study. Herein, we show that CNP enhance the antitumor activity of doxorubicin in human melanoma cells. Synergistic effects on cytotoxicity, reactive oxygen species generation, and oxidative damage in tumor cells were observed after co-incubation. In contrast to doxorubicin, CNP do not cause DNA damage and even protect human dermal fibroblasts from doxorubicin-induced cytotoxicity. A combination of classical chemotherapeutics with nongenotoxic but antitumor active CNP may provide a new strategy against cancer by improving therapeutic outcome and benefit for patients.

  10. Superiority of DFT+U with non-linear core correction for open-shell binary rare-earth metal oxides: a case study of native point defects in cerium oxides

    NASA Astrophysics Data System (ADS)

    Huang, Bolong

    2014-09-01

    We successfully proposed a newly corrected density functional theory plus Hubbard U parameter (DFT + U) based on partial core correction on the orbitals within norm-conserving lanthanide atomic pseudopotentials. A related and comprehensive investigation of native point defects in cerium oxides has also been performed as an examine by practice.

  11. Nanocasted synthesis of magnetic mesoporous iron cerium bimetal oxides (MMIC) as an efficient heterogeneous Fenton-like catalyst for oxidation of arsenite.

    PubMed

    Wen, Zhipan; Zhang, Yalei; Dai, Chaomeng; Sun, Zhen

    2015-04-28

    Magnetic mesoporous iron cerium bimetal oxides (MMIC) with large surface area and pore volume was synthesized via the hard template approach. This obtained MMIC was easily separated from aqueous solution with an external magnetic field and was proposed as a heterogeneous Fenton-like catalyst for oxidation of As(III). The MMIC presented excellent catalytic activity for the oxidation of As(III), achieving almost complete oxidation of 1000ppb As(III) after 60min and complete removal of arsenic species after 180min with reaction conditions of 0.4g/L catalyst, pH of 3.0 and 0.4mM H2O2. Kinetics analysis showed that arsenic removal followed the pseudo-first order, and the pseudo-first-order rate constants increased from 0.0014min(-1) to 0.0548min(-1) as the H2O2 concentration increased from 0.04mM to 0.4mM. On the basis of the effects of XPS analysis and reactive oxidizing species, As(III) in aqueous solution was mainly oxidized by OH radicals, including the surface-bound OHads generated on the MMIC surface which were involved in Fe(2+) and Ce(3+), and free OHfree generation by soluble iron ions which were released from the MMIC into the bulk solution, and the generated As(V) was finally removed by MMIC through adsorption.

  12. Comparison of the Mechanism of Toxicity of Zinc Oxide and Cerium Oxide Nanoparticles Based on Dissolution and Oxidative Stress Properties

    PubMed Central

    Xia, Tian; Kovochich, Michael; Liong, Monty; Mädler, Lutz; Gilbert, Benjamin; Shi, Haibin; Yeh, Joanne I.; Zink, Jeffrey I.; Nel, Andre E.

    2014-01-01

    Nanomaterials (NM) exhibit novel physicochemical properties that determine their interaction with biological substrates and processes. Three metal oxides nanoparticles that are currently being produced in high tonnage, TiO2, ZnO and CeO2, were synthesized by flame spray pyrolysis process and compared in a mechanistic study to elucidate the physicochemical characteristics that determine cellular uptake, subcellular localization, and toxic effects based on a test paradigm that was originally developed for oxidative stress and cytotoxicity in RAW 264.7 and BEAS-2B cell lines. ZnO induced toxicity in both cells, leading to the generation of reactive oxygen species (ROS), oxidant injury, excitation of inflammation and cell death. Using ICP-MS and fluorescent-labeled ZnO, it is found that ZnO dissolution could happen in culture medium and endosomes. Non-dissolved ZnO nanoparticles enter caveolae in BEAS-2B, but enter lysosomes in RAW 264.7 cells in which smaller particle remnants dissolve. In contrast, fluorescent-labeled CeO2 nanoparticles were taken up intact into caveolin-1 and LAMP-1 positive endosomal compartments, respectively, in BEAS-2B and RAW 264.7 cells, without inflammation or cytotoxicity. Instead, CeO2 suppressed ROS production and induced cellular resistance to an exogenous source of oxidative stress. Fluorescent-labeled TiO2 was processed by the same uptake pathways as CeO2 but did not elicit any adverse or protective effects. These results demonstrate that metal oxide nanoparticles induce a range of biological responses that vary from cytotoxic to cytoprotective and can only be properly understood by using a tiered test strategy such as we developed for oxidative stress and adapted to study other aspects of nanoparticle toxicity. PMID:19206459

  13. Polyacrylic acid-coated cerium oxide nanoparticles: An oxidase mimic applied for colorimetric assay to organophosphorus pesticides.

    PubMed

    Zhang, Shi-Xiang; Xue, Shi-Fan; Deng, Jingjing; Zhang, Min; Shi, Guoyue; Zhou, Tianshu

    2016-11-15

    It is important and urgent to develop reliable and highly sensitive methods that can provide on-site and rapid detection of extensively used organophosphorus pesticides (OPs) for their neurotoxicity. In this study, we developed a novel colorimetric assay for the detection of OPs based on polyacrylic acid-coated cerium oxide nanoparticles (PAA-CeO2) as an oxidase mimic and OPs as inhibitors to suppress the activity of acetylcholinesterase (AChE). Firstly, highly dispersed PAA-CeO2 was prepared in aqueous solution, which could catalyze the oxidation of TMB to produce a color reaction from colorless to blue. And the enzyme of AChE was used to catalyze the substrate of acetylthiocholine (ATCh) to produce thiocholine (TCh). As a thiol-containing compound with reducibility, TCh can decrease the oxidation of TMB catalyzed by PAA-CeO2. Upon incubated with OPs, the enzymatic activity of AChE was inhibited to produce less TCh, resulting in more TMB catalytically oxidized by PAA-CeO2 to show an increasing blue color. The two representative OPs, dichlorvos and methyl-paraoxon, were tested using our proposed assay. The novel assay showed notable color change in a concentration-dependent manner, and as low as 8.62 ppb dichlorvos and 26.73 ppb methyl-paraoxon can be readily detected. Therefore, taking advantage of such oxidase-like activity of PAA-CeO2, our proposed colorimetric assay can potentially be a screening tool for the precise and rapid evaluation of the neurotoxicity of a wealth of OPs.

  14. Method of applying a cerium diffusion coating to a metallic alloy

    SciTech Connect

    Jablonski, Paul D.; Alman, David E.

    2009-06-30

    A method of applying a cerium diffusion coating to a preferred nickel base alloy substrate has been discovered. A cerium oxide paste containing a halide activator is applied to the polished substrate and then dried. The workpiece is heated in a non-oxidizing atmosphere to diffuse cerium into the substrate. After cooling, any remaining cerium oxide is removed. The resulting cerium diffusion coating on the nickel base substrate demonstrates improved resistance to oxidation. Cerium coated alloys are particularly useful as components in a solid oxide fuel cell (SOFC).

  15. Construction of A Triple-Stimuli-Responsive System Based on Cerium Oxide Coated Mesoporous Silica Nanoparticles

    PubMed Central

    Wen, Jia; Yang, Kui; Xu, Yongqian; Li, Hongjuan; Liu, Fengyu; Sun, Shiguo

    2016-01-01

    In this work, a triple-stimuli (GSH, pH and light irradiation) responsive system were designed based on CeO2 nanoparticles (CeO2 NPs) coated doxorubicin (DOX) and photosensitizer hematoporphyrin (HP) dual-loaded mesoporous silica nanoparticles (MSN). Upon entering into cancer cells, both high concentration of intracellular GSH and low pH environment would reduce CeO2 NPs to cerium ions, accompanied with the degradation of CeO2 NPs and the conformational change of HP under light irradiation, the preloaded DOX are thus released from the nanocarrier, resulting in a contrast fluorescence enhancement. Meanwhile, 1O2 generated from HP for potential photodynamic therapy (PDT) upon light irradiation. In comparison, not much influence can be observed for normal cells. This nanosystem not only has a significantly enhanced efficacy for cancer cells but also broad the scope for the future design and applications of multifunctional platforms for synergetic chemotherapy and PDT. PMID:27941942

  16. Morphology control of cerium oxide particles synthesized via a supercritical solvothermal method.

    PubMed

    Devaraju, M Kempaiah; Yin, Shu; Sato, Tsugio

    2009-11-01

    Rod and sphere-like CeO(2) particles were obtained via a supercritical solvothermal method using CeCl(3).7H(2)O and Ce(NO(3))(3).6H(2)O as cerium sources in ethanol and methanol at 400 degrees C for 15 min followed by calcination in air. The rodlike particles were 200-400 nm in diameter and 1-2 mum in length. The spherical particles were 300-500 nm in diameter. The as-prepared rodlike particles using CeCl(3).7H(2)O consisted of mixtures of Ce(OH)(3) and Ce(CH(3)COO)(3) and were converted to rodlike CeO(2) by calcination in air at 500 degrees C. In contrast, the spherical particles prepared using Ce(NO(3))(3).6H(2)O consisted of fluorite-structured CeO(2). The possible formation mechanism was discussed on the basis of the effect of reaction time on the morphology at 400 degrees C. The rod- and spherelike CeO(2) particles exhibited strong UV absorption below 400 nm, and the absorbance edges extend to nearly 500 nm. The rod- and spherelike CeO(2) particles exhibited near-UV emission at 360 nm and blue emission at 465 nm with higher emission intensity compared to the commercial CeO(2) sample.

  17. Dissolution and transformation of cerium oxide nanoparticles in plant growth media

    NASA Astrophysics Data System (ADS)

    Schwabe, Franziska; Schulin, Rainer; Rupper, Patrick; Rotzetter, Aline; Stark, Wendelin; Nowack, Bernd

    2014-10-01

    From environmental modeling of engineered nanomaterial (ENM) release, it is clear that ENMs will enter soils, where they interact with soil compounds as well as plant roots. We analyzed three different size groups of cerium dioxide nanoparticles (CeO2-NPs) in respect to chemical changes in the most common plant growth medium, Hoagland solution. We created a simple environmental model using liquid dispersions of 9-, 23-, and 64-nm-uncoated CeO2-NPs. We found that CeO2-NPs release dissolved Ce when the pH of the medium is below 4.6 and in the presence of strong chelating agents even at pH of 8. In addition, we found that in reaction with Fe2+-ions, equimolar amounts of Ce were released from NPs. We could elucidate the involvement of the CeO2-NPs surface redox cycle between Ce3+ and Ce4+ to explain particle transformation. The chemical transformation of CeO2-NPs was summarized in four probable reactions: dissolution, surface reduction, complexation, and precipitation on the NP surface. The results show that CeO2-NPs are clearly not insoluble as often stated but can release significant amounts of Ce depending on the composition of the surrounding medium.

  18. Toxicity assessment of aggregated/agglomerated cerium oxide nanoparticles in an in vitro 3D airway model: the influence of mucociliary clearance.

    PubMed

    Frieke Kuper, C; Gröllers-Mulderij, Mariska; Maarschalkerweerd, Thérèse; Meulendijks, Nicole M M; Reus, Astrid; van Acker, Frédérique; Zondervan-van den Beuken, Esther K; Wouters, Mariëlle E L; Bijlsma, Sabina; Kooter, Ingeborg M

    2015-03-01

    We investigated the toxicity of aggregated nanoparticles of cerium oxide (CeO2) using an in vitro 3D human bronchial epithelial model that included a mucociliary apparatus (MucilAir™). CeO2 was dispersed in saline and applied to the apical surface of the model. CeO2 did not induce distinct effects in the model, whereas it did in BEAS-2B and A549 cell cultures. The absence of effects of CeO2 was not because of the model's insensitivity. Nanoparticles of zinc oxide (ZnO) elicited positive responses in the toxicological assays. Respiratory mucus (0.1% and 1%) added to dispersions increased aggregation/agglomeration to such an extent that most CeO2 sedimented within a few minutes. Also, the mucociliary apparatus of the model removed CeO2 from the central part of the apical surface to the borders. This 'clearance' may have prevented the majority of CeO2 from reaching the epithelial cells. Chemical analysis of cerium in the basal tissue culture medium showed only minimal translocation of cerium across the 3D barrier. In conclusion, mucociliary defence appeared to prevent CeO2 reaching the respiratory epithelial cells in this 3D in vitro model. This model and approach can be used to study compounds of specific toxicological concern in airway defence mechanisms in vitro.

  19. The Degradation Mitigation Effect of Cerium Oxide in Polymer Electrolyte Membranes in Extended Fuel Cell Durability Tests

    SciTech Connect

    Pearman, Benjamin P; Mohajeri, Nahid; Brooker, R. Paul; Rodgers, Marianne; Slattery, Darlene; Hampton, Michael; Cullen, David A; Seal, Sudipta

    2013-01-01

    In this work, two formulations of single-crystal cerium oxide nanoparticles of varying particle sizes were incorporated into perfluorosulfonic acid membrane electrode assemblies (MEAs) and their ability to improve the in-situ membrane durability was studied by subjecting them to 94 and 500 hours open-circuit voltage hold accelerated durability tests . In the shorter test the open circuit voltage decay rate was reduced by half and the fluoride emission by at least one order of magnitude, though no effect on hydrogen crossover or performance of the baseline MEAs was measured. The presence of the additive increased the particle size but decreased the number of platinum catalyst particles that were deposited in the membrane. The main Pt band was found at the predicted location; however, the incorporation of ceria caused a broadening with particles reaching further into the membrane. In 500 h tests, ceria-containing MEAs demonstrated a seven-fold decrease in open-circuit voltage decay and three order of magnitude reduction in fluoride emission rates with unchanged performance and hydrogen crossover, remaining effectively pristine whilst the baseline MEA underwent catastrophic failure.

  20. Transport of cerium oxide nanoparticles in saturated silica media: influences of operational parameters and aqueous chemical conditions

    NASA Astrophysics Data System (ADS)

    Zhang, Zhaohan; Gao, Peng; Qiu, Ye; Liu, Guohong; Feng, Yujie; Wiesner, Mark

    2016-10-01

    This paper aimed to investigate the influences of operational parameters and aqueous chemical conditions on transport behaviors of cerium oxides nanoparticles (CeO2-NPs) in saturated silica media. Results indicated that increasing rates of attachment efficiency (α) were related with cationic types, and critical deposition concentration (CDC) for divalent cation (Ca2+ and Mg2+) were more than 31-fold of that for monovalent cation (Na+ and K+). Increase or reduction of electrolyte pH could both promote the mobility of CeO2-NPs in glass beads, while influence was more evident at alkaline conditions. α increased linearly with NPs concentrations, while decreased linearly with flow velocity in the column, and effects were related with electrolyte contents. Presence of surfactants could sharply decreased α, and SDS was more effective to facilitate CeO2-NPs transport than Triton X–100. With DOMs concentrations increasing, α firstly kept constant, then sharply declined, and finally reduced very slowly. The influence of DOMs on NPs deposition was in order of SA > HA > TA >  BSA. Overall, this study revealed that aqueous chemical conditions was crucial to NPs transport in porous media, and would provide significant information for our understanding on the fate and transport of nanoparticles in natural environment.

  1. The degradation mitigation effect of cerium oxide in polymer electrolyte membranes in extended fuel cell durability tests

    NASA Astrophysics Data System (ADS)

    Pearman, Benjamin P.; Mohajeri, Nahid; Brooker, R. Paul; Rodgers, Marianne P.; Slattery, Darlene K.; Hampton, Michael D.; Cullen, David A.; Seal, Sudipta

    2013-03-01

    In this work, two formulations of cerium oxide nanoparticles were incorporated into perfluorosulfonic acid membrane electrode assemblies (MEAs) and their ability to improve the in-situ membrane durability was studied by subjecting them to 94 and 500 h open-circuit voltage hold accelerated durability tests. In the shorter test the open circuit voltage decay rate was reduced by half and the fluoride emission by at least one order of magnitude, though no effect on hydrogen crossover or performance on the baseline MEAs was measured. The presence of the additive increased the particle size but decreased the number of platinum catalyst particles that were deposited in the membrane. The main Pt band was found at the predicted location; however, the incorporation of ceria caused a broadening with particles reaching further into the membrane. In 500 h tests, ceria-containing MEAs demonstrated a seven-fold decrease in open-circuit voltage decay and three orders of magnitude reduction in fluoride emission rates with unchanged performance and hydrogen crossover, remaining effectively pristine whilst the baseline MEA underwent catastrophic failure.

  2. Transport of cerium oxide nanoparticles in saturated silica media: influences of operational parameters and aqueous chemical conditions

    PubMed Central

    Zhang, Zhaohan; Gao, Peng; Qiu, Ye; Liu, Guohong; Feng, Yujie; Wiesner, Mark

    2016-01-01

    This paper aimed to investigate the influences of operational parameters and aqueous chemical conditions on transport behaviors of cerium oxides nanoparticles (CeO2-NPs) in saturated silica media. Results indicated that increasing rates of attachment efficiency (α) were related with cationic types, and critical deposition concentration (CDC) for divalent cation (Ca2+ and Mg2+) were more than 31-fold of that for monovalent cation (Na+ and K+). Increase or reduction of electrolyte pH could both promote the mobility of CeO2-NPs in glass beads, while influence was more evident at alkaline conditions. α increased linearly with NPs concentrations, while decreased linearly with flow velocity in the column, and effects were related with electrolyte contents. Presence of surfactants could sharply decreased α, and SDS was more effective to facilitate CeO2-NPs transport than Triton X–100. With DOMs concentrations increasing, α firstly kept constant, then sharply declined, and finally reduced very slowly. The influence of DOMs on NPs deposition was in order of SA > HA > TA >  BSA. Overall, this study revealed that aqueous chemical conditions was crucial to NPs transport in porous media, and would provide significant information for our understanding on the fate and transport of nanoparticles in natural environment. PMID:27694968

  3. Microwave synthesis of pure and doped cerium (IV) oxide (CeO2) nanoparticles for methylene blue degradation.

    PubMed

    El Rouby, W M A; Farghali, A A; Hamdedein, A

    2016-11-01

    Cerium (IV) oxide (CeO2), samarium (Sm) and gadolinium (Gd) doped CeO2 nanoparticles were prepared using microwave technique. The effect of microwave irradiation time, microwave power and pH of the starting solution on the structure and crystallite size were investigated. The prepared nanoparticles were characterized using X-ray diffraction, FT-Raman spectroscopy, and transmission electron microscope. The photocatalytic activity of the as-prepared CeO2, Sm and Gd doped CeO2 toward degradation of methylene blue (MB) dye was investigated under UV light irradiation. The effect of pH, the amount of catalyst and the dye concentration on the degradation extent were studied. The photocatalytic activity of CeO2 was kinetically enhanced by trivalent cation (Gd and Sm) doping. The results revealed that Gd doped CeO2 nanoparticles exhibit the best catalytic degradation activity on MB under UV irradiation. For clarifying the environmental safety of the by products produced from the degradation process, the pathways of MB degradation were followed using liquid chromatography/mass spectroscopy (LC/MS). The total organic carbon content measurements confirmed the results obtained by LC/MS. Compared to the same nanoparticles prepared by another method, it was found that Gd doped CeO2 prepared by hydrothermal process was able to mineralize MB dye completely under UV light irradiation.

  4. Cerium Oxide Nanoparticle Modified Scaffold Interface Enhances Vascularization of Bone Grafts by Activating Calcium Channel of Mesenchymal Stem Cells.

    PubMed

    Xiang, Junyu; Li, Jianmei; He, Jian; Tang, Xiangyu; Dou, Ce; Cao, Zhen; Yu, Bo; Zhao, Chunrong; Kang, Fei; Yang, Lu; Dong, Shiwu; Yang, Xiaochao

    2016-02-01

    Insufficient blood perfusion is one of the critical problems that hamper the clinical application of tissue engineering bone (TEB). Current methods for improving blood vessel distribution in TEB mainly rely on delivering exogenous angiogenic factors to promote the proliferation, migration, differentiation, and vessel formation of endothelial cells (ECs) and/or endothelial progenitor cells (EPCs). However, obstacles including limited activity preservation, difficulty in controlled release, and high cost obstructed the practical application of this strategy. In this study, TEB scaffold were modified with cerium oxide nanoparticles (CNPs) and the effects of CNPs existed at the scaffold surface on the growth and paracrine behavior of mesenchymal stem cells (MSCs) were investigated. The CNPs could improve the proliferation and inhibit the apoptosis of MSCs. Meanwhile, the interaction between the cell membrane and the nanoparticle surface could activate the calcium channel of MSCs leading to the rise of intracellular free Ca(2+) level, which subsequently augments the stability of HIF-1α. These chain reactions finally resulted in high expression of angiogenic factor VEGF. The improved paracrine of VEGF could thereby promote the proliferation, differentiation, and tube formation ability of EPCs. Most importantly, in vivo ectopic bone formation experiment demonstrated this method could significantly improve the blood vessel distribution inside of TEB.

  5. Effects of cerium oxide nanoparticles on the species and distribution of phosphorus in enhanced phosphorus removal sequencing batch biofilm reactor.

    PubMed

    Xu, Yi; Wang, Chao; Hou, Jun; Wang, Peifang; You, Guoxiang; Miao, Lingzhan; Lv, Bowen; Yang, Yangyang

    2017-03-01

    The short term (8h) influences of cerium oxide nanoparticles (CeO2NPs) on the process of phosphorus removal in biofilm were investigated. At concentration of 0.1mg/L, CeO2 NPs posed no impacts on total phosphorus (TP) removal. While at 20mg/L, TP removal efficiency reduced from 85.16% to 59.62%. Results of P distribution analysis and (31)P nuclear magnetic resonance spectroscopy implied that the anaerobic degradation of polyphosphate (polyP) and the release of orthophosphate in extracellular polymeric substances (EPS) were inhibited. After aerobic exposure, the average chain length of polyP in microbial cells and EPS was shorter than control, and monoester and diester phosphates in cells were observed to release into EPS. Moreover, the EPS production and its contribution to P removal increased, while the capacity of EPS in P storage declined. X-ray diffraction analysis and saturation index calculation revealed that the formation of inorganic P precipitation in biofilm was inhibited.

  6. Comparative hazard identification of nano- and micro-sized cerium oxide particles based on 28-day inhalation studies in rats.

    PubMed

    Gosens, Ilse; Mathijssen, Liesbeth E A M; Bokkers, Bas G H; Muijser, Hans; Cassee, Flemming R

    2014-09-01

    There are many uncertainties regarding the hazard of nanosized particles compared to the bulk material of the parent chemical. Here, the authors assess the comparative hazard of two nanoscale (NM-211 and NM-212) and one microscale (NM-213) cerium oxide materials in 28-day inhalation toxicity studies in rats (according to Organisation for Economic Co-operation and Development technical guidelines). All three materials gave rise to a dose-dependent pulmonary inflammation and lung cell damage but without gross pathological changes immediately after exposure. Following NM-211 and NM-212 exposure, epithelial cell injury was observed in the recovery groups. There was no evidence of systemic inflammation or other haematological changes following exposure of any of the three particle types. The comparative hazard was quantified by application of the benchmark concentration approach. The relative toxicity was explored in terms of three exposure metrics. When exposure levels were expressed as mass concentration, nanosized NM-211 was the most potent material, whereas when expression levels were based on surface area concentration, micro-sized NM-213 material induced the greatest extent of pulmonary inflammation/damage. Particles were equipotent based on particle number concentrations. In conclusion, similar pulmonary toxicity profiles including inflammation are observed for all three materials with little quantitative differences. Systemic effects were virtually absent. There is little evidence for a dominant predicting exposure metric for the observed effects.

  7. Fate of engineered cerium oxide nanoparticles in an aquatic environment and their toxicity toward 14 ciliated protist species.

    PubMed

    Zhang, Wei; Pu, Zhichao; Du, Songyan; Chen, Yongsheng; Jiang, Lin

    2016-05-01

    The potential environmental impacts of engineered cerium oxide nanoparticles (CeO2 NPs) on aquatic organisms have remained largely unknown. Therefore, the laboratory study featured herein was performed to determine the fate of CeO2 NPs in an aquatic environment and their toxicity towards 14 different ciliated protist species at a specified population level. An investigation of 48 h aggregation kinetics in the Dryl's solution showed the CeO2 NPs to be relatively stable. The pH values in three test medium were too far away from PZC, which explained the stability of CeO2 NPs. CeO2 NPs generally elicited more toxicity with increasing NP concentration, following certain dose-response relationships. Nano-CeO2 resulted in greater toxicity in a particle state than when added as bulk material. LC50 values showed a negative correlation with the surface-to-volume ratio for these protists, suggesting that surface adsorption of CeO2 NPs might contribute to the observed toxicity. Additionally, acute toxic responses of 14 ciliated protist species to CeO2 NPs were not significantly phylogenetically conserved. The results of these observations provide a better insight into the potential risks of CeO2 NPs in an aquatic environment.

  8. Particle-specific toxicity and bioavailability of cerium oxide (CeO2) nanoparticles to Arabidopsis thaliana.

    PubMed

    Yang, Xinping; Pan, Haopeng; Wang, Peng; Zhao, Fang-Jie

    2017-01-15

    The use of manufactured cerium oxide nanoparticles (CeO2-NPs) in consumer products has increased markedly over the past decade, and their release into natural ecosystems is unavoidable. This study investigated the phytotoxicity and uptake of CeO2-NPs in Arabidopsis thaliana grown in an agar medium. Although low concentrations of CeO2-NPs had stimulatory effects on plant growth, at higher concentrations, CeO2-NPs reduced growth and had adverse effects on the antioxidant systems and photosystem. Importantly, the toxicity resulted from the nanoparticles per se, rather than from the dissolved Ce ions. CeO2-NPs were taken up and subsequently translocated to shoot tissues, and transmission electron microscopy (TEM) showed the presence of a large number of needle-like particle aggregations in the intercellular regions and the cytoplasm of leaf cells. The up-translocation factor to shoots was independent of the concentrations of Ce in the roots and the supplied forms of Ce (i.e. CeO2-NPs, CeO2-bulk, and ionic Ce), suggesting that endocytosis is likely to be a general mechanism responsible for the translocation of these Ce compounds. These findings provide important information regarding the toxicity and uptake of CeO2-NPs in plants, which needs to be considered in environmental risk assessment for the safe use and disposal of CeO2-NPs.

  9. Synthesis, characterization and photocatalytic study of graphene oxide and cerium co-doped in TiO2

    NASA Astrophysics Data System (ADS)

    Li, Jia; Zhang, Quan; Zeng, Liping; He, Deliang

    2016-02-01

    The nanocomposite of titanium dioxide (TiO2) combined with graphene oxide (GO) and cerium (Ce) was successfully synthesized via sol-gel method followed by calcining at 300 °C for 2 h. The composite was characterized by X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy, scanning electron microscopy (SEM) and Brunauer-Emmett-Teller. The photocatalytic activity was evaluated by photodegradation of methylene blue (MB) under the irradiation of xenon lamp. This study demonstrated that GO and Ce co-doped in TiO2 could broaden absorption edge to the visible light and increase surface area of samples. SEM observation showed that addition of Ce could solve the problem of the agglomeration of GO under the same experimental conditions. Moreover, the MB photocatalytic degradation rate of the composite with GO doped for 0.2 % and Ce doped for 0.6 % (mass ratio) was up to 97.7 %, which was largely attributed to the synergistic effects in the GO, Ce and TiO2 system.

  10. Porous nano-cerium oxide wood chip biochar composites for aqueous levofloxacin removal and sorption mechanism insights.

    PubMed

    Yi, Shengze; Sun, Yuanyuan; Hu, Xin; Xu, Hongxia; Gao, Bin; Wu, Jichun

    2017-01-14

    The adsorption removal of levofloxacin (LEV), a widely used fluoroquinolone antibiotic, by using the biochars derived from the pyrolysis of pine wood chip pretreated with cerium trichloride was investigated through batch sorption experiments and multiple characterization techniques. The differences in the basic physicochemical properties between Ce-impregnated biochars and the pristine biochars were confirmed by the analysis of elemental compositions, specific surface areas, energy dispersive spectrometry, X-ray diffraction, and thermo-gravimetry. FT-IR spectra of the pre- and post-sorption biochars confirmed the chemical adsorption for LEV sorption onto the biochars. Large shifts in the binding energy of Ce3d, O1s, C1s, and N1s regions on the pre- and post-sorption biochars indicated the surface complexation of LEV molecule onto the biochars. The binding species of Ce(4+) and Ce(3+) identified by X-ray photoelectron spectroscopy reflect the role of Ce oxides during sorption. Batch adsorption showed the significant enhancement of adsorption capacity for LEV after the Ce modification. Batch adsorption kinetic data fitted well with the pseudo-second-order model. Both the Langmuir and the Freundlich models reproduced the isotherm data well. Findings from this work indicated that Ce-impregnated biochars can be effective for the removal of aqueous LEV.

  11. Transport of cerium oxide nanoparticles in saturated silica media: influences of operational parameters and aqueous chemical conditions.

    PubMed

    Zhang, Zhaohan; Gao, Peng; Qiu, Ye; Liu, Guohong; Feng, Yujie; Wiesner, Mark

    2016-10-03

    This paper aimed to investigate the influences of operational parameters and aqueous chemical conditions on transport behaviors of cerium oxides nanoparticles (CeO2-NPs) in saturated silica media. Results indicated that increasing rates of attachment efficiency (α) were related with cationic types, and critical deposition concentration (CDC) for divalent cation (Ca(2+) and Mg(2+)) were more than 31-fold of that for monovalent cation (Na(+) and K(+)). Increase or reduction of electrolyte pH could both promote the mobility of CeO2-NPs in glass beads, while influence was more evident at alkaline conditions. α increased linearly with NPs concentrations, while decreased linearly with flow velocity in the column, and effects were related with electrolyte contents. Presence of surfactants could sharply decreased α, and SDS was more effective to facilitate CeO2-NPs transport than Triton X-100. With DOMs concentrations increasing, α firstly kept constant, then sharply declined, and finally reduced very slowly. The influence of DOMs on NPs deposition was in order of SA > HA > TA >  BSA. Overall, this study revealed that aqueous chemical conditions was crucial to NPs transport in porous media, and would provide significant information for our understanding on the fate and transport of nanoparticles in natural environment.

  12. Cerium oxide nanoparticles/multi-wall carbon nanotubes composites: Facile synthesis and electrochemical performances as supercapacitor electrode materials

    NASA Astrophysics Data System (ADS)

    Deng, Dongyang; Chen, Nan; Li, Yuxiu; Xing, Xinxin; Liu, Xu; Xiao, Xuechun; Wang, Yude

    2017-02-01

    Cerium oxide nanoparticles/multi-wall carbon nanotubes (MWCNTs) composites are synthesized by a facile hydrothermal method without any surfactant or template. The morphology and microstructure of samples are examined by scanning electron microscopy (SEM), transition electron microscopy (TEM), X-ray diffraction (XRD), Raman spectrum and X-ray photoelectron spectroscopy (XPS). Electrochemical properties of the MWCNTs, the pure CeO2, and the CeO2/MWCNTs nanocomposites electrodes are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge (GDC) and electrochemical impedance spectroscopy (EIS) measurements. The CeO2/MWCNTs nanocomposite (at the mole ratio of 1:1) electrode exhibits much larger specific capacitance compared with both the MWCNTs electrode and the pure CeO2 electrode and significantly improves cycling stability compared to the pure CeO2 electrode. The CeO2/MWCNTs nanocomposite (at the mole ratio of 1:1) achieves a specific capacitance of 455.6 F g-1 at the current density of 1 A g-1. Therefore, the as prepared CeO2/MWCNTs nanocomposite is a promising electrode material for high-performance supercapacitors.

  13. Effects of cerium oxide nanoparticles to fish and mammalian cell lines: An assessment of cytotoxicity and methodology.

    PubMed

    Rosenkranz, P; Fernández-Cruz, M L; Conde, E; Ramírez-Fernández, M B; Flores, J C; Fernández, M; Navas, J M

    2012-09-01

    Two cerium oxide nanoparticles (CeO(2) NPs) and one micro-sized CeO(2) particle were thoroughly characterized in their pristine form, in water and in cell culture medium. The particles were tested for cytotoxicity to the H4IIE rat hepatoma cell line or the RTG-2 rainbow trout gonadal cell line by means of four standard cytotoxicity assays. Nominal concentrations were verified by inductively coupled plasma mass spectrometry (ICP-MS) and methods were assessed for their suitability to detect reliably adverse effects due to particle exposure. All three particles showed aggregation in water and media. In the H4IIE cell line, the MTT cytotoxicity test revealed that negative effects could be observed for the CeO(2) NPs after 24h and for all particles after 72h of exposure, making the effects size, concentration and time dependent. No negative effect for the concentrations tested was detected for the remaining three assays and the RTG-2 cell line, making the MTT assay and the H4IIE cell line an appropriate system to assess adverse effects of CeO(2) NPs. A verification of the nominal concentration through ICP-MS revealed that there was a discrepancy between nominal and measured concentration depending on concentration and particle tested. Interferences of particles with assays were found to be present and need to be taken into consideration.

  14. Effect of nano-sized cerium-zirconium oxide solid solution on far-infrared emission properties of tourmaline powders

    NASA Astrophysics Data System (ADS)

    Guo, Bin; Yang, Liqing; Hu, Weijie; Li, Wenlong; Wang, Haojing

    2015-10-01

    Far-infrared functional nanocomposites were prepared by the co-precipitation method using natural tourmaline (XY3Z6Si6O18(BO3)3V3W, where X is Na+, Ca2+, K+, or vacancy; Y is Mg2+, Fe2+, Mn2+, Al3+, Fe3+, Mn3+, Cr3+, Li+, or Ti4+; Z is Al3+, Mg2+, Cr3+, or V3+; V is O2-, OH-; and W is O2-, OH-, or F-) powders, ammonium cerium(IV) nitrate and zirconium(IV) nitrate pentahydrate as raw materials. The reference sample, tourmaline modified with ammonium cerium(IV) nitrate alone was also prepared by a similar precipitation route. The results of Fourier transform infrared spectroscopy show that tourmaline modified with Ce and Zr has a better far-infrared emission property than tourmaline modified with Ce alone. Through characterization by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), the mechanism for oxygen evolution during the heat process in the two composite materials was systematically studied. The XPS spectra show that Fe3+ ratio inside tourmaline modified with Ce alone can be raised by doping Zr. Moreover, it is showed that there is a higher Ce3+ ratio inside the tourmaline modified with Ce and Zr than tourmaline modified with Ce alone. In addition, XRD results indicate the formation of CeO2 and Ce1-xZrxO2 crystallites during the heat treatment and further TEM observations show they exist as nanoparticles on the surface of tourmaline powders. Based on these results, we attribute the improved far-infrared emission properties of Ce-Zr doped tourmaline to the enhanced unit cell shrinkage of the tourmaline arisen from much more oxidation of Fe2+ to Fe3+ inside the tourmaline caused by the change in the catalyst redox properties of CeO2 brought about by doping with Zr4+. In all samples, tourmaline modified with 7.14 wt.% Ce and 1.86 wt.% Zr calcined at 800∘C for 5 h has the best far-infrared emission property with the maximum emissivity value of 98%.

  15. Fabrication of lactate biosensor based on lactate dehydrogenase immobilized on cerium oxide nanoparticles.

    PubMed

    Nesakumar, Noel; Sethuraman, Swaminathan; Krishnan, Uma Maheswari; Rayappan, John Bosco Balaguru

    2013-11-15

    An electrochemical biosensor was developed to determine lactate that plays an important role in clinical diagnosis, fermentation and food quality analysis. Abnormal concentration of lactate has been related to diseases such as hypoxia, acute heart disorders, lactic acidosis, muscle fatigue and meningitis. Also, lactate concentration in blood helps to evaluate the athletic performance in sports. The main aim of the work is to fabricate NADH/LDH/Nano-CeO2/GCE bio-electrode for sensing lactate in human blood samples. Toward this, CeO2 nanoparticles were synthesized by a hydroxide mediated approach using cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and NaOH as precursors. X-ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FE-SEM) studies were carried out to determine the structural and morphological characteristics of CeO2 nanoparticles. XRD pattern indicated the formation of highly crystalline CeO2 nanoparticles with face centered cubic structure. The FE-SEM studies revealed the formation of nanospherical particles of size 29.73±2.59 nm. The working electrode was fabricated by immobilizing nicotinamide adenine dinucleotide (NADH) and lactate dehydrogenase (LDH) on GCE surface with CeO2 nanoparticles as an interface. Electrochemical studies were carried out through cyclic voltammetry using a three electrode system with NADH/LDH/NanoCeO2/GCE as a working electrode, Ag/AgCl saturated with 0.1M KCl as a reference electrode and Pt wire as a counter electrode. From the amperometric study, the linearity was found to be in the range of 0.2-2 mM with the response time of less than 4s.

  16. Cerium Oxide-Incorporated Calcium Silicate Coating Protects MC3T3-E1 Osteoblastic Cells from H2O2-Induced Oxidative Stress.

    PubMed

    Li, Kai; Xie, Youtao; You, Mingyu; Huang, Liping; Zheng, Xuebin

    2016-11-01

    Oxidative stress regulates cellular functions in multiple pathological conditions, including bone formation by osteoblastic cells. In this work, the protective effects of cerium oxide (CeO2)-incorporated calcium silicate (CeO2-CS) coating on the response of osteoblasts to H2O2-induced oxidative stress and the related mechanism were examined. CeO2 incorporation significantly improved osteoblast viability and reduced cell apoptosis caused by H2O2 when compared with the control. H2O2-induced reduction of differentiation marker alkaline phosphatase (ALP) was recovered in the presence of the CeO2-CS coating. The above effects were mediated by the antioxidant effect of CeO2. The CeO2-CS coating immersed in 0.1 mM H2O2 aqueous solution was able to degrade 64 % of it in 1 week. In addition, CeO2 incorporation decreased reactive oxygen species (ROS) production and suppressed malondialdehyde (MDA) formation in H2O2-treated osteoblasts. Taken together, CeO2-CS biomedical coatings with antioxidant property would be promising for bone regeneration under oxidative stress.

  17. Effects of Cerium and Titanium Oxide Nanoparticles in Soil on the Nutrient Composition of Barley (Hordeum vulgare L.) Kernels

    PubMed Central

    Pošćić, Filip; Mattiello, Alessandro; Fellet, Guido; Miceli, Fabiano; Marchiol, Luca

    2016-01-01

    The implications of metal nanoparticles (MeNPs) are still unknown for many food crops. The purpose of this study was to evaluate the effects of cerium oxide (nCeO2) and titanium oxide (nTiO2) nanoparticles in soil at 0, 500 and 1000 mg·kg−1 on the nutritional parameters of barley (Hordeum vulgare L.) kernels. Mineral nutrients, amylose, β-glucans, amino acid and crude protein (CP) concentrations were measured in kernels. Whole flour samples were analyzed by ICP-AES/MS, HPLC and Elemental CHNS Analyzer. Results showed that Ce and Ti accumulation under MeNPs treatments did not differ from the control treatment. However, nCeO2 and nTiO2 had an impact on composition and nutritional quality of barley kernels in contrasting ways. Both MeNPs left β-glucans unaffected but reduced amylose content by approximately 21%. Most amino acids and CP increased. Among amino acids, lysine followed by proline saw the largest increase (51% and 37%, respectively). Potassium and S were both negatively impacted by MeNPs, while B was only affected by 500 mg nCeO2·kg−1. On the contrary Zn and Mn concentrations were improved by 500 mg nTiO2·kg−1, and Ca by both nTiO2 treatments. Generally, our findings demonstrated that kernels are negatively affected by nCeO2 while nTiO2 can potentially have beneficial effects. However, both MeNPs have the potential to negatively impact malt and feed production. PMID:27294945

  18. Study of Degradation Kinetics of Parathion Methyl On Mixed Nanocrystalline Titania-Zirconium and Titania-Cerium Oxides

    NASA Astrophysics Data System (ADS)

    Kuráň, Pavel; Pšenička, Martin; Šťastný, Martin; Benkocká, Monika; Janoš, Pavel

    2016-10-01

    The unique surface properties of some nanocrystalline metal oxides and their application for removal of various toxic compounds were reported in early 1990s. Recently, a reliable method for the preparation of reactive cerium dioxide sorbent and its application for degradation of the organophosphate pesticides, such as parathion methyl, chlorpyrifos, dichlofenthion, fenchlorphos, and prothiofos, as well as of some chemical warfare agents-nerve gases soman and O-ethyl S-[2-(diisopropylamino) ethyl] methylphosphonothioate (VX) was published. This paper reports on the kinetics study of degradation of parathion methyl as a representative organophosphate on nanocrystalline metal oxides TiO2, ZrO2, CeO2 and their mixtures in different molar ratios of particular elements. The tested sorbents except of CeO2 were prepared by different methods (e.g. sol-gel, precipitation) in cooperation with Institute of Inorganic Chemistry (Rez, Czech Republic). The degradation kinetics of parathion methyl on tested sorbents was followed by HPLC equipped with diode array detector. The basic kinetics parameters (half-lives of parathion methyl degradation, rate constants of degradation product formation) were calculated for each sorbent from Weber-Morris equation of 1st order diffusion kinetic model. The results proved the ability of prepared sorbents to degrade parathion methyl under formation of 4-nitrophenol as the main degradation product. The most efficient sorbents were TiCe (2:8), TiCe (1:1), TiCe (0:1) (50-70 %) followed by TiZr (1:1), TiCe (8:2), TiZr (8:2), TiZr (2:8) (20-30%) and TiO2, ZrO2 (less than 5 %).

  19. The state of the components in copper-cerium catalysts supported on different oxides

    NASA Astrophysics Data System (ADS)

    Kosmambetova, G. R.; Kriventsov, V. V.; Moroz, E. M.; Pakharukova, V. P.; Strizhak, P. E.; Zyuzin, D. A.

    2009-05-01

    The phase composition and the state of the active components in the catalysts used for preferential oxidation (PROX) of CO in hydrogen-containing mixtures are considered. Cu-Ce catalysts supported on different oxides (ZrO 2, TiO 2, Al 2O 3, MnO 2) before and after PROX reaction are characterized.

  20. Influence of a Cerium surface treatment on the oxidation behavior of type 347 stainless steel

    SciTech Connect

    Alman, D.E.; Jablonski, P.D.

    2007-04-01

    A surface treatment was applied to the surface of Type 347 stainless steel to enhance oxidation resistance. The treatment consisted of dip coating coupons in a CeO2 and halide activator slurry, followed by a thermal treatment at 900C in an inert atmosphere for 12 hours. Cyclical oxidation tests were conducted at 800C in either dry air or air+3%H2O. In dry air, the treatment reduced the oxidation rate (reduced the magnitude of weight gain) of the alloy by a factor of three. Protective chromium based oxide and spinel ((Mn,Cr)3O4 and (Cr,Fe)2O3) phases formed on the surface of the untreated and treated alloy. More significantly, the treatment suppressed the oxide scale spallation that occurred upon cyclical exposure of this alloy to moist air. In moist air, less protective chromite (FeCr2O4), magnetite (Fe+2Fe2+3O4), and hematite (Fe2O3) formed as oxide products on the surface of the base alloy. The treated alloy did not spall during exposure to moist air, and interestingly, the treated alloy possessed similar oxidation rates (magnitude of weight gain) in both moist and dry air. The same protective chromium based oxide and spinel ((Mn,Cr)3O4 and (Cr,Fe)2O3) phases formed on the surface of the treated alloy exposed to both moist and dry air. In the aggressive moist environment, the Ce surface treatment suppressed the formation of less protective iron-oxides, and concomitant oxide scale spallation during thermal cycling.

  1. Storage capacity and oxygen mobility in mixed oxides from transition metals promoted by cerium

    NASA Astrophysics Data System (ADS)

    Perdomo, Camilo; Pérez, Alejandro; Molina, Rafael; Moreno, Sonia

    2016-10-01

    The oxygen mobility and storage capacity of Ce-Co/Cu-MgAl or Ce-MgAl mixed oxides, obtained by hydrotalcite precursors, were evaluated using Toluene-temperature-programmed-reaction, 18O2 isotopic exchange and O2-H2 titration. The presence of oxygen vacancies-related species was evaluated by means of Electron Paramagnetic Resonance. A correlation was found between the studied properties and the catalytic activity of the oxides in total oxidation processes. It was evidenced that catalytic activity depends on two related processes: the facility with which the solid can be reduced and its ability to regenerate itself in the presence of molecular oxygen in the gas phase. These processes are enhanced by Cu-Co cooperative effect in the mixed oxides. Additionally, the incorporation of Ce in the Co-Cu catalysts improved their oxygen transport properties.

  2. The growth and structure of thin oxide films on nickel superficially modified with ceria and cerium

    NASA Astrophysics Data System (ADS)

    Czerwinski, Franciszek

    A small addition of elements with a high affinity to oxygen can have a profound effect on the high temperature oxidation behaviour of many metals and alloys. In order to explain the improvement in oxidation resistance, the research was conducted using Ni-NiO as a model system of cation-diffusing oxides, and Ce as a typical reactive element. Three essential techniques were employed to modify the surface of Ni with Ce and CeO2: ion implantation, sol-gel technology, and reactive sputtering. The improvement of Ni oxidation resistance was assessed by oxygen uptake measurements mainly during the early stages but also for long-term exposures at temperatures between 873 and 1073 K in pure oxygen, both at low and atmospheric pressures. The variety of oxides produced were examined in detail by several advanced techniques including Rutherford backscattering spectrometry, Auger electron spectroscopy, secondary ion-mass spectrometry, transmission- and scanning-transmission electron microscopy equipped with electron and x-ray analyzers, atomic force microscopy, infrared spectroscopy, and x-ray diffraction techniques. In order to provide direct evidence regarding the mechanism of oxide growth, a sequential oxidation using oxygen isotopes 16O2/18O2 was conducted. After conversion to the form of ceramic coating, superficially applied CeO2 sol-gel significantly reduced the Ni oxidation rate as well as changing the NiO morphology and internal microstructure. The extent of the effect depended on coating thickness, size of CeO2 particles, substrate surface finishing and preoxidation before coating. Under optimum conditions, the reduction in the Ni oxidation rate achieved by sol-gel, reactive sputtering, and ion implantation, was similar. It was found that Ni oxidation resistance is controlled by a well-defined NiO sublayer that is composed of randomly-oriented NiO grains and CeO2 particles. Moreover, in this sublayer, the Ce4+ ions segregate to the NiO grain boundaries. At high

  3. A nitrilo-tri-acetic-acid/acetic acid route for the deposition of epitaxial cerium oxide films as high temperature superconductor buffer layers

    SciTech Connect

    Thuy, T.T.; Lommens, P.; Narayanan, V.; Van de Velde, N.; De Buysser, K.; Herman, G.G.; Cloet, V.; Van Driessche, I.

    2010-09-15

    A water based cerium oxide precursor solution using nitrilo-tri-acetic-acid (NTA) and acetic acid as complexing agents is described in detail. This precursor solution is used for the deposition of epitaxial CeO{sub 2} layers on Ni-5at%W substrates by dip-coating. The influence of the complexation behavior on the formation of transparent, homogeneous solutions and gels has been studied. It is found that ethylenediamine plays an important role in the gelification. The growth conditions for cerium oxide films were Ar-5% gas processing atmosphere, a solution concentration level of 0.25 M, a dwell time of 60 min at 900 {sup o}C and 5-30 min at 1050 {sup o}C. X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscopy (AFM), pole figures and spectroscopic ellipsometry were used to characterize the CeO{sub 2} films with different thicknesses. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) was used to determine the carbon residue level in the surface of the cerium oxide film, which was found to be lower than 0.01%. Textured films with a thickness of 50 nm were obtained. - Graphical abstract: Study of the complexation and hydrolysis behavior of Ce{sup 4+} ions in the presence of nitrilo-tri-acetic acid and the subsequent development of an aqueous chemical solution deposition route suited for the processing of textured CeO{sub 2} buffer layers on Ni-W tapes.

  4. The influence of Cerium doping on the crystal and electronic properties of FeBO3 oxides

    NASA Astrophysics Data System (ADS)

    Özkendir, Osman Murat

    2017-02-01

    Cerium substituted FeBO3 samples were investigated according to their crystal and electronic properties via the general formula CexCuFe1-x BO3. With the doping of the heavy fermion "Cerium", samples were determined in polycrystalline structure. With the incressing Ce in the samples, disturbances on the Cu-Fe planes became more clear that supports the formation of geometrically different crystal structures. To obtain the electronic mechanisms in the crystals, X-ray Absorption Fine Structure Spectroscopy (XAFS) technique were used to study the electronic properties of the samples in coordination with the X-ray diffraction (XRD) patterns. As a result of the analysis, f-levels of the Cerium atoms were determined as the main playground of interplays and strongly correlated electrons of 4f-3d levels were determined to emerge dominant interactions causing phase transitions.

  5. Engineering scoping study of the production of hydrogen and oxygen from the cerium oxide-sodium phosphate/carbonate thermochemical cycle

    SciTech Connect

    Goeller, H.E.

    1984-04-01

    One potential industrial application of solar energy is for the production of hydrogen (and oxygen) using a cycle of thermochemical reactions. This report provides a preliminary evaluation of the engineering feasibility of such an operation based on the cerium oxide-sodium phosphate/carbonate thermochemical cycle to produce 2 metric tons of hydrogen per day. Material and heat balances were developed, and equipment was sized. The preliminary pilot plant layout was then compared with a plant of the same capacity for producing hydrogen by the electrolysis of water. The use of water electrolysis seems superior and cheaper in all respects. 7 figures, 4 tables.

  6. Characteristics and mechanism study of cerium oxide based random access memories

    SciTech Connect

    Hsieh, Cheng-Chih; Roy, Anupam; Rai, Amritesh; Chang, Yao-Feng; Banerjee, Sanjay K.

    2015-04-27

    In this work, low operating voltage and high resistance ratio of different resistance states of binary transition metal oxide based resistive random access memories (RRAMs) are demonstrated. Binary transition metal oxides with high dielectric constant have been explored for RRAM application for years. However, CeO{sub x} is considered as a relatively new material to other dielectrics. Since research on CeO{sub x} based RRAM is still at preliminary stage, fundamental characteristics of RRAM such as scalability and mechanism studies need to be done before moving further. Here, we show very high operation window and low switching voltage of CeO{sub x} RRAMs and also compare electrical performance of Al/CeO{sub x}/Au system between different thin film deposition methods and discuss characteristics and resistive switching mechanism.

  7. Investigation of ionic conductivity of lanthanum cerium oxide nano crystalline powder synthesized by co precipitation method

    NASA Astrophysics Data System (ADS)

    Tinwala, Hozefa; Shah, Patij; Siddhapara, Kirit; Shah, Dimple; Menghani, Jyoti

    2016-10-01

    Lanthanum (La) doped Ceria (CeO2) electrolyte has attracted considerable interest, as a candidate material for solid oxide fuel cells (SOFCs). The ionic conductivity of La doped CeO2 system (La2Ce2O7) nano-particles synthesized by the co-precipitation method has been investigated. The cubic fluorite structure was observed from the structural analysis of the material. Morphology of the sintered pellets are observed by scanning electron microscope (SEM), respectively. From the results of impedance spectroscopy from temperature range of room temperature to 400 °C, the oxide ion conductivity due to proton charge carrier was observed. Thermogravimetric analysis (TGA) was performed on the material to check stability of phase at high temperature.

  8. Toxicity and bio-accumulation of inhaled cerium oxide nanoparticles in CD1 mice.

    PubMed

    Aalapati, Srinivas; Ganapathy, Selvam; Manapuram, Saikumar; Anumolu, Goparaju; Prakya, Balakrishna Murthy

    2014-11-01

    Male CD1 mice were subjected to nose-inhalation exposure of CeO2 nanoparticles (NPs) for 0, 7, 14 or 28 days with 14 or 28 days of recovery time at an aerosol concentration of 2 mg/m(3). Markers of lung injury and pro-inflammatory cytokines (interleukin-1beta, tumour necrosis factor-alpha, interleukin-6 and macrophage inflammatory protein-2) in bronchoalveolar lavage fluid (BALF), oxidative stress in lungs, bio-accumulation, and histopathology of pulmonary and extrapulmonary tissues were assessed. BALF analysis revealed the induction of pulmonary inflammation, as evident by an increase in the influx of neutrophils with a significant secretion of pro-inflammatory cytokines that lead to generation of oxidative stress and cytotoxicity, as is evident by induction of lipid peroxidation, depletion of glutathione and increased BALF lactate dehydrogenase and protein. The histopathological examination revealed that these inhaled CeO2 NPs were located all over the pulmonary parenchyma, inducing a severe, chronic, active inflammatory response characterised by necrosis, proteinosis, fibrosis and well-formed discrete granulomas in the pulmonary tissue and tubular degeneration leading to coagulative necrosis in kidneys. Inductively coupled plasma optical emission spectrometer results showed a significant bio-accumulation of these particles in the pulmonary and extrapulmonary tissues, even after one month of post-inhalation exposure. Together, these findings suggest that inhalation exposure of CeO2 NPs can induce pulmonary and extrapulmonary toxicity.

  9. Role of the oxidation state of cerium on the ceria surfaces for silicate adsorption

    NASA Astrophysics Data System (ADS)

    Seo, Jihoon; Moon, Jinok; Kim, Joo Hyun; Lee, Kangchun; Hwang, Junha; Yoon, Heesung; Yi, Dong Kee; Paik, Ungyu

    2016-12-01

    In this study, we have investigated the role of the Ce oxidation state (Ce3+/Ce4+) on the CeO2 surfaces for silicate adsorption. In aqueous medium, the Ce3+ sites lead to the formation of -OH groups at the CeO2 surface through H2O dissociation. Silicate ions can adsorb onto the CeO2 surface through interaction with the -OH groups (-Ce-OH- + -Si-O- ↔ -Ce-O-Si- + OH-). As the Ce3+ concentration increased from 19.3 to 27.6%, the surface density of -OH group increased from 0.34 to 0.72 OH/nm2. To evaluate the adsorption behaviors of silicate ions onto CeO2 NPs, we carried out an adsorption isothermal analysis, and the adsorption isotherm data followed the Freundlich model. The Freundlich constant for the relative adsorption capacity (KF) and adsorption intensity (1/n) indicated that CeO2 NPs with high Ce3+ concentration show higher adsorption affinity with silicate ions. As a result, we have demonstrated that the Ce oxidation state (Ce3+/Ce4+) on the CeO2 surface can have a significant influence on the silicate adsorption.

  10. Interactions between sub-10-nm iron and cerium oxide nanoparticles and 3T3 fibroblasts: the role of the coating and aggregation state

    NASA Astrophysics Data System (ADS)

    Safi, M.; Sarrouj, H.; Sandre, O.; Mignet, N.; Berret, J.-F.

    2010-04-01

    Recent nanotoxicity studies revealed that the physico-chemical characteristics of engineered nanomaterials play an important role in the interactions with living cells. Here, we report on the toxicity and uptake of cerium and iron oxide sub-10-nm nanoparticles by NIH/3T3 mouse fibroblasts. Coating strategies include low-molecular weight ligands (citric acid) and polymers (poly(acrylic acid), MW = 2000 g mol - 1). Electrostatically adsorbed on the surfaces, the organic moieties provide a negatively charged coating in physiological conditions. We find that most particles were biocompatible, as exposed cells remained 100% viable relative to controls. Only the bare and the citrate-coated nanoceria exhibit a slight decrease in mitochondrial activity at very high cerium concentrations (>1 g l - 1). We also observe that the citrate-coated particles are internalized/adsorbed by the cells in large amounts, typically 250 pg/cell after 24 h incubation for iron oxide. In contrast, the polymer-coated particles are taken up at much lower rates (<30 pg/cell). The strong uptake shown by the citrated particles is related to the destabilization of the dispersions in the cell culture medium and their sedimentation down to the cell membranes. In conclusion, we show that the uptake of nanomaterials by living cells depends on the coating of the particles and on its ability to preserve the colloidal nature of the dispersions.

  11. Pilot demonstration of cerium oxide coated anodes. Final report, April 1990--October 1992

    SciTech Connect

    Gregg, J.S.; Frederick, M.S.; Shingler, M.J.; Alcorn, T.R.

    1992-10-01

    Cu cermet anodes were tested for 213 to 614 hours with an in-situ deposited CEROX coating in a pilot cell operated by Reynolds Manufacturing Technology Laboratory. At high bath ratio ({approximately}1.5) and low current density (0.5 A/cm{sup 2}), a {ge}1 mm thick dense CEROX coating was deposited on the anodes. At lower bath ratios and higher current density, the CEROX coating was thinner and less dense, but no change in corrosion rate was noted. Regions of low current density on the anodes and sides adjacent to the carbon anode sometimes had thin or absent CEROX coatings. Problems with cracking and oxidation of the cermet substrates led to higher corrosion rates in a pilot cell than would be anticipated from lab scale results.

  12. Effect of cerium oxide nanoparticles on inflammation in vascular endothelial cells

    PubMed Central

    Gojova, Andrea; Lee, Jun-Tae; Jung, Heejung S.; Guo, Bing; Barakat, Abdul I.; Kennedy, Ian M.

    2010-01-01

    Because vascular endothelial cell inflammation is critical in the development of cardiovascular pathology, we hypothesized that direct exposure of human aortic endothelial cells (HAECs) to ultrafine particles induces an inflammatory response. To test the hypothesis, we incubated HAECs for 4 h with different concentrations (0.001–50 μg/ml) of CeO2 nanoparticles and subsequently measured mRNA levels of the three inflammatory markers intercellular adhesion molecule 1 (ICAM-1), interleukin (IL)-8, and monocyte chemotactic protein (MCP-1) using real-time polymerase chain reaction (PCR). Ceria nanoparticles caused very little inflammatory response in HAECs, even at the highest dose. This material is apparently rather benign in comparison with Y2O3 and ZnO nanoparticles that we have studied previously. These results suggest that inflammation in HAECs following acute exposure to metal oxide nanoparticles depends strongly on particle composition. PMID:19558244

  13. Effect of cerium oxide nanoparticles on inflammation in vascular endothelial cells.

    PubMed

    Gojova, Andrea; Lee, Jun-Tae; Jung, Heejung S; Guo, Bing; Barakat, Abdul I; Kennedy, Ian M

    2009-07-01

    Because vascular endothelial cell inflammation is critical in the development of cardiovascular pathology, we hypothesized that direct exposure of human aortic endothelial cells (HAECs) to ultrafine particles induces an inflammatory response. To test the hypothesis, we incubated HAECs for 4 h with different concentrations (0.001-50 microg/ml) of CeO(2) nanoparticles and subsequently measured mRNA levels of the three inflammatory markers intercellular adhesion molecule 1 (ICAM-1), interleukin (IL)-8, and monocyte chemotactic protein (MCP-1) using real-time polymerase chain reaction (PCR). Ceria nanoparticles caused very little inflammatory response in HAECs, even at the highest dose. This material is apparently rather benign in comparison with Y(2)O(3) and ZnO nanoparticles that we have studied previously. These results suggest that inflammation in HAECs following acute exposure to metal oxide nanoparticles depends strongly on particle composition.

  14. Assessment the Exposure Level of Rare Earth Elements in Workers Producing Cerium, Lanthanum Oxide Ultrafine and Nanoparticles.

    PubMed

    Li, Yan; Yu, Hua; Li, Peng; Bian, Ying

    2017-02-01

    In order to assess occupational exposure level of 15 rare earth elements (REEs) and identify the associated influence, we used inductively coupled plasma mass spectrometry (ICP-MS) based on closed-vessel microwave-assisted wet digestion procedure to determinate the concentration of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu in urinary samples obtained from workers producing ultrafine and nanoparticles containing cerium and lanthanum oxide. The results suggest that La and Ce were the primary component, together accounting for 97 % of total REEs in workers. The urinary levels of La, and Ce among the workers (6.36, 15.32 μg.g(-1) creatinine, respectively) were significantly enriched compared to those levels measured in the control subjects (1.52, 4.04 μg.g(-1) creatinine, respectively) (p < 0.05). This study simultaneously identified the associated individual factors, the results indicate that the concentrations in over 5 years group (11.64 ± 10.93 for La, 27.83 ± 24.38 for Ce) were significantly elevated compared to 1-5 years group (2.58 ± 1.51 for La, 6.87 ± 3.90 for Ce) (p < 0.05). Compared the urinary levels of La and Ce at the separation and packaging locations (9.10 ± 9.51 for La, 22.29 ± 21.01 for Ce) with the other locations (2.85 ± 0.98 for La, 6.37 ± 2.12 for Ce), the results show urinary concentrations were significantly higher in workers at separation and packaging locations (p < 0.01). Inter-individual variation in levels of La and Ce in urine is the result of multi-factorial comprehensive action. Further researches should focus on the multiple factors contributing to the REEs levels of the occupationally exposed workers.

  15. Combination of supported bimetallic rhodium–molybdenum catalyst and cerium oxide for hydrogenation of amide

    PubMed Central

    Nakagawa, Yoshinao; Tamura, Riku; Tamura, Masazumi; Tomishige, Keiichi

    2015-01-01

    Hydrogenation of cyclohexanecarboxamide to aminomethylcyclohexane was conducted with silica-supported bimetallic catalysts composed of noble metal and group 6–7 elements. The combination of rhodium and molybdenum with molar ratio of 1:1 showed the highest activity. The effect of addition of various metal oxides was investigated on the catalysis of Rh–MoOx/SiO2, and the addition of CeO2 much increased the activity and selectivity. Higher hydrogen pressure and higher reaction temperature in the tested range of 2–8 MPa and 393–433 K, respectively, were favorable in view of both activity and selectivity. The highest yield of aminomethylcyclohexane obtained over Rh–MoOx/SiO2 + CeO2 was 63%. The effect of CeO2 addition was highest when CeO2 was not calcined, and CeO2 calcined at >773 K showed a smaller effect. The use of CeO2 as a support rather decreased the activity in comparison with Rh–MoOx/SiO2. The weakly-basic nature of CeO2 additive can affect the surface structure of Rh–MoOx/SiO2, i.e. reducing the ratio of Mo–OH/Mo–O− sites. PMID:27877749

  16. Combination of supported bimetallic rhodium-molybdenum catalyst and cerium oxide for hydrogenation of amide

    NASA Astrophysics Data System (ADS)

    Nakagawa, Yoshinao; Tamura, Riku; Tamura, Masazumi; Tomishige, Keiichi

    2015-02-01

    Hydrogenation of cyclohexanecarboxamide to aminomethylcyclohexane was conducted with silica-supported bimetallic catalysts composed of noble metal and group 6-7 elements. The combination of rhodium and molybdenum with molar ratio of 1:1 showed the highest activity. The effect of addition of various metal oxides was investigated on the catalysis of Rh-MoOx/SiO2, and the addition of CeO2 much increased the activity and selectivity. Higher hydrogen pressure and higher reaction temperature in the tested range of 2-8 MPa and 393-433 K, respectively, were favorable in view of both activity and selectivity. The highest yield of aminomethylcyclohexane obtained over Rh-MoOx/SiO2 + CeO2 was 63%. The effect of CeO2 addition was highest when CeO2 was not calcined, and CeO2 calcined at >773 K showed a smaller effect. The use of CeO2 as a support rather decreased the activity in comparison with Rh-MoOx/SiO2. The weakly-basic nature of CeO2 additive can affect the surface structure of Rh-MoOx/SiO2, i.e. reducing the ratio of Mo-OH/Mo-O- sites.

  17. Oxidation-state sensitive imaging of cerium dioxide by atomic-resolution low-angle annular dark field scanning transmission electron microscopy

    PubMed Central

    Johnston-Peck, Aaron C.; Winterstein, Jonathan P.; Roberts, Alan D.; DuChene, Joseph S.; Qian, Kun; Sweeny, Brendan C.; Wei, Wei David; Sharma, Renu; Stach, Eric A.; Herzing, Andrew A.

    2016-01-01

    Low-angle annular dark field (LAADF) scanning transmission electron microscopy (STEM) imaging is presented as a method that is sensitive to the oxidation state of cerium ions in CeO2 nanoparticles. This relationship was validated through electron energy loss spectroscopy (EELS), in situ measurements, as well as multislice image simulations. Static displacements caused by the increased ionic radius of Ce3+ influence the electron channeling process and increase electron scattering to low angles while reducing scatter to high angles. This process manifests itself by reducing the high-angle annular dark field (HAADF) signal intensity while increasing the LAADF signal intensity in close proximity to Ce3+ ions. This technique can supplement STEM-EELS and in so doing, relax the experimental challenges associated with acquiring oxidation state information at high spatial resolutions. PMID:26744830

  18. Oxidation-state sensitive imaging of cerium dioxide by atomic-resolution low-angle annular dark field scanning transmission electron microscopy.

    PubMed

    Johnston-Peck, Aaron C; Winterstein, Jonathan P; Roberts, Alan D; DuChene, Joseph S; Qian, Kun; Sweeny, Brendan C; Wei, Wei David; Sharma, Renu; Stach, Eric A; Herzing, Andrew A

    2016-03-01

    Low-angle annular dark field (LAADF) scanning transmission electron microscopy (STEM) imaging is presented as a method that is sensitive to the oxidation state of cerium ions in CeO2 nanoparticles. This relationship was validated through electron energy loss spectroscopy (EELS), in situ measurements, as well as multislice image simulations. Static displacements caused by the increased ionic radius of Ce(3+) influence the electron channeling process and increase electron scattering to low angles while reducing scatter to high angles. This process manifests itself by reducing the high-angle annular dark field (HAADF) signal intensity while increasing the LAADF signal intensity in close proximity to Ce(3+) ions. This technique can supplement STEM-EELS and in so doing, relax the experimental challenges associated with acquiring oxidation state information at high spatial resolutions.

  19. Studies on Synthesis, Microstructure and Transport Properties of Doped Cerium Oxides

    NASA Astrophysics Data System (ADS)

    Handal, Hala Talaat Abd El-Samei

    Acceptor-doped ceria exhibits mixed ionic electronic conduction in reducing conditions and chemical stability against sulfur poisoning and coking. This thesis's primary goal is to explore new anode materials based on ceria--solid solutions for solid oxide fuel cells (SOFCs). The physicochemical and electrochemical performance of Ce0.9-xY 0.1MnxO2-delta ( x = 0 to 15 mol%) (CYMO) and Ce0.87Y0.1Mn 0.01N0.02O2-delta (N = Mg or Ca) were studied. Among the materials investigated in this study, Ce0.89Y 0.1Mn0.01Mg0.02O2-delta (Mg-CYMO) showed the highest total conductivity of 0.2 S cm-1 at 700°C in H2. An area specific polarization resistance of 0.23 O cm2 was observed for both Mg-CYMO and Ce0.8Y 0.1Mn0.1O2-delta (10CYMO) at 800°C, in wet H2. Chronoamperometric measurement for the symmetrical cell configuration based on 10CYMO electrodes showed stable performance upon exposure to 10 ppm H2S/H2. In a full cell configuration, 10CYMO (anode)/YSZ (electrolyte)/La0.8Sr0.2MnO3 (LSM)-YSZ cathode, polarization resistance of 1.4 O cm2 and power density of 75 mW/cm2 were obtained at 800°C in wet H2. The main challenge of employing proton-conducting electrolytes in SOFC is their poor chemical stability in the presence of steam and hydrocarbon fuels. Another goal of this thesis is to develop a chemically stable proton-conducting electrolyte for SOFCs. The effects of Fe and Co substitution on the electrical and physicochemical properties of BaCe0.9Sm0.1O 3-delta (BCS) were evaluated. Thermogravimetric analysis showed that incorporation of 5 to 10 mol% Fe or Co in BCS did not improve the chemical stability in CO2 at elevated temperatures. The BCSC10 sample sintering at 1400°C showed the highest electrical conductivity of 0.02 S cm -1 at 600°C in air, but it did not show any appreciable proton mobility under humidified atmosphere.

  20. Properties of cerium-zirconium mixed oxides partially substituted by neodymium: Comparison with Zr-Ce-Pr-O ternary oxides

    SciTech Connect

    Mikulova, Jana; Rossignol, Sylvie . E-mail: Sylvie.rossignol@univ-poitiers.fr; Gerard, Francois; Mesnard, Danielle; Kappenstein, Charles; Duprez, Daniel

    2006-08-15

    CeO{sub 2} doped with praseodymium, neodymium and/or zirconium atoms were prepared by coprecipitation and by the sol-gel method. Structural properties were investigated by in situ XRD and Raman spectroscopy while oxygen storage capacity (OSC) was measured by transient CO oxidation. All the compounds, except pure Nd{sub 2}O{sub 3}, have a fluorite-type structure as well as a Raman band at 560 cm{sup -1} characteristic of the oxygen vacancies involving non-stoichiometric oxides. The lattice parameter under hydrogen, being dependent on the temperature, revealed two reduction mechanisms: one at a low temperature at the surface and another at a high temperature in the bulk. Ce-Nd binary oxides show a strong tendency towards crystallite aggregation, which reduces accessibility to gases and OSC properties. Zirconium improves the thermal resistance to sintering of both Ce-Nd and Ce-Pr oxides. The Zr-Ce-Pr-O followed by Zr-Ce-Nd-O compounds displaying high oxygen mobility at a low temperature, appear to be very promising for practical applications such as OSC materials. - Graphical abstract: Variation of oxygen vacancies under hydrogen on ternary oxides.

  1. Development and Validation of Spectrofluorimetric Method for Determination of Biotin in Bulk and Pharmaceutical Preparations via its Oxidation with Cerium (IV).

    PubMed

    Walash, M I; Rizk, M; Sheribah, Z A; Salim, M M

    2010-09-01

    A simple and sensitive spectrofluorimetric method was developed for the determination of biotin in pure form and in pharmaceutical preparations. The proposed method is based on the oxidation of the drug with cerium (IV) ammonium sulfate in acidic medium. The fluorescence of the produced Cerium (III) was measured at 365 nm after excitation at 255 nm. The different experimental parameters affecting the development and stability of the reaction were carefully studied and optimized. The method is applicable over the concentration range of 30-120 ng/mL with correlation coefficient of 0.9998. The detection limit (LOD) of biotin was 2.41 ng/mL while quantitation limit (LOQ) was 7.29 ng/mL. The proposed procedure was successfully applied for the determination of biotin in pharmaceutical preparations with mean recoveries of 99.55 ± 0.83 and 101.67 ± 1.53 for biotin ampoules and capsules, respectively. The results obtained were in good agreement with those obtained using the official method.

  2. Cerium Oxide Nanoparticles in Lung Acutely Induce Oxidative Stress, Inflammation, and DNA Damage in Various Organs of Mice

    PubMed Central

    Yuvaraju, Priya; Beegam, Sumaya; Fahim, Mohamed A.; Ali, Badreldin H.

    2017-01-01

    CeO2 nanoparticles (CeO2 NPs) which are used as a diesel fuel additive are emitted in the particulate phase in the exhaust, posing a health concern. However, limited information exists regarding the in vivo acute toxicity of CeO2 NPs on multiple organs. Presently, we investigated the acute (24 h) effects of intratracheally instilled CeO2 NPs in mice (0.5 mg/kg) on oxidative stress, inflammation, and DNA damage in major organs including lung, heart, liver, kidneys, spleen, and brain. Lipid peroxidation measured by malondialdehyde production was increased in the lungs only, and reactive oxygen species were increased in the lung, heart, kidney, and brain. Superoxide dismutase activity was decreased in the lung, liver, and kidney, whereas glutathione increased in lung but it decreased in the kidney. Total nitric oxide was increased in the lung and spleen but it decreased in the heart. Tumour necrosis factor-α increased in all organs studied. Interleukin- (IL-) 6 increased in the lung, heart, liver, kidney, and spleen. IL-1β augmented in the lung, heart, kidney, and spleen. Moreover, CeO2 NPs induced DNA damage, assessed by COMET assay, in all organs studied. Collectively, these findings indicate that pulmonary exposure to CeO2 NPs causes oxidative stress, inflammation, and DNA damage in multiple organs. PMID:28392888

  3. Determining the Source of Water Vapor in a Cerium Oxide Electrochemical Oxygen Separator to Achieve Aviator Grade Oxygen

    NASA Technical Reports Server (NTRS)

    Graf, John; Taylor, Dale; Martinez, James

    2014-01-01

    More than a metric ton of water is transported to the International Space Station (ISS) each year to provide breathing oxygen for the astronauts. Water is a safe and compact form of stored oxygen. The water is electrolyzed on ISS and ambient pressure oxygen is delivered to the cabin. A much smaller amount of oxygen is used each year in spacesuits to conduct Extra Vehicular Activities (EVAs). Space suits need high pressure (>1000 psia) high purity oxygen (must meet Aviator Breathing Oxygen "ABO" specifications, >99.5% O2). The water / water electrolysis system cannot directly provide high pressure, high purity oxygen, so oxygen for EVAs is transported to ISS in high pressure gas tanks. The tanks are relatively large and heavy, and the majority of the system launch weight is for the tanks and not the oxygen. Extracting high purity oxygen from cabin air and mechanically compressing the oxygen might enable on-board production of EVA grade oxygen using the existing water / water electrolysis system. This capability might also benefit human spaceflight missions, where oxygen for EVAs could be stored in the form of water, and converted into high pressure oxygen on-demand. Cerium oxide solid electrolyte-based ion transport membranes have been shown to separate oxygen from air, and a supported monolithic wafer form of the CeO2 electrolyte membrane has been shown to deliver oxygen at pressures greater than 300 psia. These supported monolithic wafers can withstand high pressure differentials even though the membrane is very thin, because the ion transport membrane is supported on both sides (Fig 1). The monolithic supported wafers have six distinct layers, each with matched coefficients of thermal expansion. The wafers are assembled into a cell stack which allows easy air flow across the wafers, uniform current distribution, and uniform current density (Fig 2). The oxygen separation is reported to be "infinitely selective" to oxygen [1] with reported purity of 99.99% [2

  4. Study of the cerium(IV)-picrate system in acetonitrile.

    PubMed

    Kratochvil, B; Tipler, M; McKay, B

    1966-07-01

    A potentiometric and spectrophotometric study has been made of the reaction between hexanitratocerate and picrate in dry acetonitrile. Several cerium(IV)-picrate complexes are formed; the formation constant for the first is estimated to be 4 from spectrophotometric measurements. The catalytic effect of picrate on hydroquinone oxidation by nitratocerate is postulated to be due to more rapid electron transfer by cerium picrate complexes.

  5. Cerium anomaly at microscale in fossils.

    PubMed

    Gueriau, Pierre; Mocuta, Cristian; Bertrand, Loïc

    2015-09-01

    Patterns in rare earth element (REE) concentrations are essential instruments to assess geochemical processes in Earth and environmental sciences. Excursions in the "cerium anomaly" are widely used to inform on past redox conditions in sediments. This proxy resources to the specificity of cerium to adopt both the +III and +IV oxidation states, while most rare earths are purely trivalent and share very similar reactivity and transport properties. In practical terms, the level of cerium anomaly is established through elemental point quantification and profiling. All these models rely on a supposed homogeneity of the cerium oxidation state within the samples. However, this has never been demonstrated, whereas the cerium concentration can significantly vary within a sample, as shown for fossils, which would vastly complicate interpretation of REE patterns. Here, we report direct micrometric mapping of Ce speciation through synchrotron X-ray absorption spectroscopy and production of local rare earth patterns in paleontological fossil tissues through X-ray fluorescence mapping. The sensitivity of the approach is demonstrated on well-preserved fishes and crustaceans from the Late Cretaceous (ca. 95 million years (Myr) old). The presence of Ce under the +IV form within the fossil tissues is attributed to slightly oxidative local conditions of burial and agrees well with the limited negative cerium anomaly observed in REE patterns. The [Ce(IV)]/[Ce(tot)] ratio appears remarkably stable at the microscale within each fossil and is similar between fossils from the locality. Speciation maps were obtained from an original combination of synchrotron microbeam X-ray fluorescence, absorption spectroscopy, and diffraction, together with light and electron microscopy. This work also highlights the need for more systematic studies of cerium geochemistry at the microscale in paleontological contexts, in particular across fossil histologies.

  6. Size determination and quantification of engineered cerium oxide nanoparticles by flow field-flow fractionation coupled to inductively coupled plasma mass spectrometry.

    PubMed

    Sánchez-García, L; Bolea, E; Laborda, F; Cubel, C; Ferrer, P; Gianolio, D; da Silva, I; Castillo, J R

    2016-03-18

    Facing the lack of studies on characterization and quantification of cerium oxide nanoparticles (CeO2 NPs), whose consumption and release is greatly increasing, this work proposes a method for their sizing and quantification by Flow Field-flow Fractionation (FFFF) coupled to Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Two modalities of FFFF (Asymmetric Flow- and Hollow Fiber-Flow Field Flow Fractionation, AF4 and HF5, respectively) are compared, and their advantages and limitations discussed. Experimental conditions (carrier composition, pH, ionic strength, crossflow and carrier flow rates) are studied in detail in terms of NP separation, recovery, and repeatability. Size characterization of CeO2 NPs was addressed by different approaches. In the absence of feasible size standards of CeO2 NPs, suspensions of Ag, Au, and SiO2 NPs of known size were investigated. Ag and Au NPs failed to show a comparable behavior to that of the CeO2 NPs, whereas the use of SiO2 NPs provided size estimations in agreement to those predicted by the theory. The latter approach was thus used for characterizing the size of CeO2 NPs in a commercial suspension. Results were in adequate concordance with those achieved by transmission electron microscopy, X-ray diffraction and dynamic light scattering. The quantification of CeO2 NPs in the commercial suspension by AF4-ICP-MS required the use of a CeO2 NPs standards, since the use of ionic cerium resulted in low recoveries (99 ± 9% vs. 73 ± 7%, respectively). A limit of detection of 0.9 μg L(-1) CeO2 corresponding to a number concentration of 1.8 × 1012 L(-1) for NPs of 5 nm was achieved for an injection volume of 100 μL.

  7. PLUTONIUM-CERIUM ALLOY

    DOEpatents

    Coffinberry, A.S.

    1959-01-01

    An alloy is presented for use as a reactor fuel. The binary alloy consists essentially of from about 5 to 90 atomic per cent cerium and the balance being plutonium. A complete phase diagram for the cerium--plutonium system is given.

  8. Inhibition of MAP kinase/NF-kB mediated signaling and attenuation of lipopolysaccharide induced severe sepsis by cerium oxide nanoparticles

    PubMed Central

    Selvaraj, Vellaisamy; Nepal, Niraj; Rogers, Steven; Manne, Nandini D.P.K.; Arvapalli, Ravikumar; Rice, Kevin M.; Asano, Shinichi; Fankhanel, Erin; Ma, Jane J.; Shokuhfar, Tolou; Maheshwari, Mani; Blough, Eric R.

    2015-01-01

    Sepsis is a life threatening disease that is associated with high mortality. Existing treatments have failed to improve survivability in septic patients. The purpose of this present study is to evaluate whether cerium oxide nanoparticles (CeO2NPs) can prevent lipopolysaccharide (LPS) induced severe sepsis mortality by preventing hepatic dysfunction in male Sprague Dawley rats. Administration of a single dose (0.5 mg/kg) of CeO2NPs intravenously to septic rats significantly improved survival rates and functioned to restore body temperature, respiratory rate and blood pressure towards baseline. Treatment-induced increases in animal survivability were associated with decreased hepatic damage along with reductions in serum cytokines/chemokines, and diminished inflammatory related signaling. Kupffer cells and macrophage cells exposed to CeO2NPs exhibited decreases in LPS-induced cytokine release (TNF-α, IL-1β, IL-6, HMGB1) which were associated with diminished cellular ROS, reduced levels of nitric oxide synthase (iNOS), cyclooxygenase 2 (COX-2), and decreased nuclear factor-kappa light chain enhancer of activated B cells (NF-kB) transcriptional activity. The findings of this study indicate that CeO2NPs may be useful as a therapeutic agent for sepsis. PMID:25968464

  9. Inhibition of MAP kinase/NF-kB mediated signaling and attenuation of lipopolysaccharide induced severe sepsis by cerium oxide nanoparticles.

    PubMed

    Selvaraj, Vellaisamy; Nepal, Niraj; Rogers, Steven; Manne, Nandini D P K; Arvapalli, Ravikumar; Rice, Kevin M; Asano, Shinichi; Fankhanel, Erin; Ma, Jane J; Shokuhfar, Tolou; Maheshwari, Mani; Blough, Eric R

    2015-08-01

    Sepsis is a life threatening disease that is associated with high mortality. Existing treatments have failed to improve survivability in septic patients. The purpose of this present study is to evaluate whether cerium oxide nanoparticles (CeO2NPs) can prevent lipopolysaccharide (LPS) induced severe sepsis mortality by preventing hepatic dysfunction in male Sprague Dawley rats. Administration of a single dose (0.5 mg/kg) of CeO2NPs intravenously to septic rats significantly improved survival rates and functioned to restore body temperature, respiratory rate and blood pressure towards baseline. Treatment-induced increases in animal survivability were associated with decreased hepatic damage along with reductions in serum cytokines/chemokines, and diminished inflammatory related signaling. Kupffer cells and macrophage cells exposed to CeO2NPs exhibited decreases in LPS-induced cytokine release (TNF-α, IL-1β, IL-6, HMGB1) which were associated with diminished cellular ROS, reduced levels of nitric oxide synthase (iNOS), cyclooxygenase 2 (COX-2), and decreased nuclear factor-kappa light chain enhancer of activated B cells (NF-kB) transcriptional activity. The findings of this study indicate that CeO2NPs may be useful as a therapeutic agent for sepsis.

  10. Cerium oxide nanoparticles alter the antioxidant capacity but do not impact tuber ionome in Raphanus sativus (L).

    PubMed

    Corral-Diaz, Baltazar; Peralta-Videa, Jose R; Alvarez-Parrilla, Emilio; Rodrigo-García, Joaquin; Morales, Maria Isabel; Osuna-Avila, Pedro; Niu, Genhua; Hernandez-Viezcas, Jose A; Gardea-Torresdey, Jorge L

    2014-11-01

    The effects of nCeO2 on food quality are not well known yet. This research was performed to determine the impact of nCeO2 on radish (Raphanus sativus L.). Plants were cultivated to full maturity in potting soil treated with nCeO2 at concentrations of 0, 62.5, 125, 250, and 500 mg/kg. Germination, growth, photosynthesis, ionome, and antioxidants were evaluated at different growth stages. Results showed that at 500 mg/kg, nCeO2 significantly retarded seed germination but did not reduce the number of germinated seeds. None of the treatments affected gas exchange, photosynthesis, growth, phenols, flavonoids, and nutrients' accumulation in tubers and leaves of adult plants. However, tubers' antioxidant capacity, expressed as FRAP, ABTS(•-) and DPPH, increased by 30%, 32%, and 85%, respectively, in plants treated with 250 mg nCeO2kg(-1) soil. In addition, cerium accumulation in tubers of plants treated with 250 and 500 mg/kg reached 72 and 142 mg/kg d wt, respectively. This suggests that nCeO2 could improve the radical scavenging potency of radish but it might introduce nCeO2 into the food chain with unknown consequences.

  11. The potential toxic effects of cerium on organism: cerium prolonged the developmental time and induced the expression of Hsp70 and apoptosis in Drosophila melanogaster.

    PubMed

    Wu, Bin; Zhang, Di; Wang, Dan; Qi, Chunyan; Li, Zongyun

    2012-10-01

    Due to the widespread application of cerium, a rare earth element, the risk of exposure to cerium has increased. Therefore, understanding the physiological effects of cerium is of great importance. Our previous work showed that cerium caused significant lifespan shortening accompanied by oxidative damage in Drosophila melanogaster, however, little is known about the detailed mechanism of cerium-induced cytotoxicity. Thus, we examined the developmental time during metamorphosis, and assessed the toxic effects of cerium by evaluating heat shock protein 70 (Hsp70), DNA damage markers and apoptosis in D. melanogaster. We found that cerium extended the developmental time of D. melanogaster and up-regulated the expression of Hsp70 when the concentration of cerium was increased (especially concentrations over 26.3 μg/g). Up-regulation of the cell cycle checkpoint p53 and cell signaling protein p38 were also observed when the concentration of cerium was over 104 μg/g. In addition, the activities of caspase-3 and caspase-9, markers of apoptosis, were significantly higher when the larvae were exposed to ceric sulfate. These results suggest that high concentrations of cerium may result in DNA damage and ultimately apoptosis in D. melanogaster, and strongly indicate that cerium should be applied with caution and the potential toxic effects in humans should also be taken into consideration.

  12. Evaluation of the role of oxidative stress, inflammation and apoptosis in the pulmonary and the hepatic toxicity induced by cerium oxide nanoparticles following intratracheal instillation in male Sprague-Dawley rats

    NASA Astrophysics Data System (ADS)

    Nalabotu, Siva Krishna

    The field of nanotechnology is rapidly progressing with potential applications in the automobile, healthcare, electronics, cosmetics, textiles, information technology, and environmental sectors. Nanomaterials are engineered structures with at least one dimension of 100 nanometers or less. With increased applications of nanotechnology, there are increased chances of exposure to manufactured nanomaterials. Recent reports on the toxicity of engineered nanomaterials have given scientific and regulatory agencies concerns over the safety of nanomaterials. Specifically, the Organization for Economic Co-operation and Development (OECD) has identified fourteen high priority nanomaterials for study. Cerium oxide (CeO2) nanoparticles are one among the high priority group. Recent data suggest that CeO2 nanoparticles may be toxic to lung cell lines in vitro and lung tissues in vivo. Other work has proposed that oxidative stress may play an important role in the toxicity; however, the exact mechanism of the toxicity, has to our knowledge, not been investigated. Similarly, it is not clear whether CeO2 nanoparticles exhibit systemic toxicity. Here, we investigate whether pulmonary exposure to CeO2 nanoparticles is associated with oxidative stress, inflammation and apoptosis in the lungs and liver of adult male Sprague-Dawley rats. Our data suggest that the intratracheal instillation of CeO2 nanoparticles can cause an increased lung weight to body weight ratio. Changes in lung weights were associated with the accumulation of cerium in the lungs, elevations in serum inflammatory markers, an increased Bax to Bcl-2 ratio, elevated caspase-3 protein levels, increased phosphorylation of p38-MAPK and diminished phosphorylation of ERK1/2-MAPK. Our findings from the study evaluating the possible translocation of CeO2 nanoparticles from the lungs to the liver suggest that CeO 2 nanoparticle exposure was associated with increased liver ceria levels, elevations in serum alanine transaminase

  13. Effects of Cerium Oxide Nanoparticles on the Proliferation, Osteogenic Differentiation and Adipogenic Differentiation of Primary Mouse Bone Marrow Stromal Cells In Vitro.

    PubMed

    Zhang, Qun; Ge, Kun; Ren, Huihui; Zhang, Cuimiao; Zhang, Jinchao

    2015-09-01

    The effects of cerium oxide nanoparticles (nanoceria) on the proliferation, osteogenic and adipogenic differentiation of primary mouse bone marrow stromal cells (BMSCs) were studied by employing 3-(4,5-dimethylthiazol-2-yl)-2,5-dipheny tetrazolium bromide (MTT), alkaline phosphatase (ALP) activity, collagen production, alizarin red-S (ARS) and oil red o stain assays. The results indicated that nanoceria increased the viability of BMSCs at all tested concentrations with evident dose dependence for 24 and 72 h. On day 14, nanoceria inhibited the osteogenic differentiation of BMSCs at all tested concentrations. On day 19 and 24, nanoceria inhibited the formation of mineralized matrix nodules of BMSCs at all tested concentrations. On day 17, nanoceria inhibited the adipogenic differentiation of BMSCs at all tested concentrations. This suggests that the effects of nanoceria on the proliferation, osteogenic differentiation and adipogenic differentiation of BMSCs are very complicated. Both the concentration and culture time have significant influence on the proliferation, osteogenic differentiation and adipogenic differentiation of BMSCs. These results will be helpful for rational applications of nanoceria in the future.

  14. [application of the analytical transmission electron microscopy techniques for detection, identification and visualization of localization of nanoparticles of titanium and cerium oxides in mammalian cells].

    PubMed

    Shebanova, A S; Bogdanov, A G; Ismagulova, T T; Feofanov, A V; Semenyuk, P I; Muronets, V I; Erokhina, M V; Onishchenko, G E; Kirpichnikov, M P; Shaitan, K V

    2014-01-01

    This work represents the results of the study on applicability of the modern methods of analytical transmission electron microscopy for detection, identification and visualization of localization of nanoparticles of titanium and cerium oxides in A549 cell, human lung adenocarcinoma cell line. A comparative analysis of images of the nanoparticles in the cells obtained in the bright field mode of transmission electron microscopy, under dark-field scanning transmission electron microscopy and high-angle annular dark field scanning transmission electron was performed. For identification of nanoparticles in the cells the analytical techniques, energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy, were compared when used in the mode of obtaining energy spectrum from different particles and element mapping. It was shown that the method for electron tomography is applicable to confirm that nanoparticles are localized in the sample but not coated by contamination. The possibilities and fields of utilizing different techniques for analytical transmission electron microscopy for detection, visualization and identification of nanoparticles in the biological samples are discussed.

  15. Structure and corrosion behavior of sputter deposited cerium oxide based coatings with various thickness on Al 2024-T3 alloy substrates

    NASA Astrophysics Data System (ADS)

    Liu, Yuanyuan; Huang, Jiamu; Claypool, James B.; Castano, Carlos E.; O'Keefe, Matthew J.

    2015-11-01

    Cerium oxide based coatings from ∼100 to ∼1400 nm in thickness were deposited onto Al 2024-T3 alloy substrates by magnetron sputtering of a 99.99% pure CeO2 target. The crystallite size of CeO2 coatings increased from 15 nm to 46 nm as the coating thickness increased from ∼100 nm to ∼1400 nm. The inhomogeneous lattice strain increased from 0.36% to 0.91% for the ∼100 nm to ∼900 nm thick coatings and slightly decreased to 0.89% for the ∼1400 nm thick coating. The highest adhesion strength to Al alloy substrates was for the ∼210 nm thick coating, due to a continuous film coverage and low internal stress. Electrochemical measurements indicated that sputter deposited crystalline CeO2 coatings acted as physical barriers that provide good cathodic inhibition for Al alloys in saline solution. The ∼900 nm thick CeO2 coated sample had the best corrosion performance that increased the corrosion resistance by two orders magnitude and lowered the cathodic current density 30 times compared to bare Al 2024-T3 substrates. The reduced defects and exposed surface, along with suppressed charge mobility, likely accounts for the improved corrosion performance as coating thickness increased from ∼100 nm to ∼900 nm. The corrosion performance decreased for ∼1400 nm thick coatings due in part to an increase in coating defects and porosity along with a decrease in adhesion strength.

  16. XANES (X-ray Absorption Near Edge Structure) investigation of cerium as an inhibitor for Al alloys

    SciTech Connect

    Davenport, A.J.; Isaacs, H.S. ); Kendig, M.W. . Science Center)

    1991-01-01

    Cerium ions are under investigation as possible replacements for toxic chromates. The use of cerium ions as corrosion inhibitors for aluminum alloys is investigated using XANES (x-ray absorption near edge structure). On immersion in a dilute solution of cerium ions, cerium is incorporated into the oxide films on aluminum alloys in either the 3- or 4-valent state depending upon the alloy and on the surface preparation. 7 refs., 2 figs.

  17. Mixed cerium-platinum oxides: Electronic structure of [CeO]Ptn (n = 1, 2) and [CeO2]Pt complex anions and neutrals

    NASA Astrophysics Data System (ADS)

    Ray, Manisha; Kafader, Jared O.; Topolski, Josey E.; Jarrold, Caroline Chick

    2016-07-01

    The electronic structures of several small Ce-Pt oxide complexes were explored using a combination of anion photoelectron (PE) spectroscopy and density functional theory calculations. Pt and Pt2 both accept electron density from CeO diatomic molecules, in which the cerium atom is in a lower-than-bulk oxidation state (+2 versus bulk +4). Neutral [CeO]Pt and [CeO]Pt2 complexes are therefore ionic, with electronic structures described qualitatively as [CeO+2]Pt-2 and [CeO+]Pt2-, respectively. The associated anions are described qualitatively as [CeO+]Pt-2 and [CeO+]Pt2-2, respectively. In both neutrals and anions, the most stable molecular structures determined by calculations feature a distinct CeO moiety, with the positively charged Ce center pointing toward the electron rich Pt or Pt2 moiety. Spectral simulations based on calculated spectroscopic parameters are in fair agreement with the spectra, validating the computationally determined structures. In contrast, when Pt is coupled with CeO2, which has no Ce-localized electrons that can readily be donated to Pt, the anion is described as [CeO2]Pt-. The molecular structure predicted computationally suggests that it is governed by charge-dipole interactions. The neutral [CeO2]Pt complex lacks charge-dipole stabilizing interactions, and is predicted to be structurally very different from the anion, featuring a single Pt-O-Ce bridge bond. The PE spectra of several of the complexes exhibit evidence of photodissociation with Pt- daughter ion formation. The electronic structures of these complexes are related to local interactions in Pt-ceria catalyst-support systems.

  18. Virus Removal by Biogenic Cerium

    SciTech Connect

    De Gusseme, B.; Du Laing, G; Hennebel, T; Renard, P; Chidambaram, D; Fitts, J; Bruneel, E; Van Driessche, I; Verbeken, K; et. al.

    2010-01-01

    The rare earth element cerium has been known to exert antifungal and antibacterial properties in the oxidation states +III and +IV. This study reports on an innovative strategy for virus removal in drinking water by the combination of Ce(III) on a bacterial carrier matrix. The biogenic cerium (bio-Ce) was produced by addition of aqueous Ce(III) to actively growing cultures of either freshwater manganese-oxidizing bacteria (MOB) Leptothrix discophora or Pseudomonas putida MnB29. X-ray absorption spectroscopy results indicated that Ce remained in its trivalent state on the bacterial surface. The spectra were consistent with Ce(III) ions associated with the phosphoryl groups of the bacterial cell wall. In disinfection assays using a bacteriophage as model, it was demonstrated that bio-Ce exhibited antiviral properties. A 4.4 log decrease of the phage was observed after 2 h of contact with 50 mg L{sup -1} bio-Ce. Given the fact that virus removal with 50 mg L{sup -1} Ce(III) as CeNO{sub 3} was lower, the presence of the bacterial carrier matrix in bio-Ce significantly enhanced virus removal.

  19. Cerium sequestration and accumulation in fractured crystalline bedrock: The role of Mn-Fe (hydr-)oxides and clay minerals

    NASA Astrophysics Data System (ADS)

    Yu, Changxun; Drake, Henrik; Mathurin, Frédéric A.; Åström, Mats E.

    2017-02-01

    This study focuses on the mechanisms of Ce sequestration and accumulation in the fracture network of the upper kilometer of the granitoid bedrock of the Baltic Shield in southeast Sweden (Laxemar area, Sweden). The material includes 81 specimens of bulk secondary mineral precipitates (;fracture coatings;) collected on fracture walls identified in 17 drill cores, and 66 groundwater samples collected from 21 deep boreholes with equipment designed for retrieval of representative groundwater at controlled depths. The concentrations of Ce in the fracture coatings, although varying considerably (10-90th percentiles: 67-438 mg kg-1), were frequently higher than those of the wall rock (10-90th percentiles: 70-118 mg kg-1). Linear combination fitting analysis of Ce LIII-edge X-ray absorption near-edge structure (XANES) spectra, obtained for 19 fracture coatings with relatively high Ce concentrations (⩾145 mg kg-1) and a wide range of Ce-anomaly values, revealed that Ce(IV) occurs frequently in the upper 10 m of the fracture network (Ce(IV)/Cetotal = 0.06-1.00 in 8 out of 11 specimens) and is mainly associated with Mn oxides (modeled as Ce oxidatively scavenged by birnessite). These features are in line with the strong oxidative and sorptive capacities of Mn oxide as demonstrated by previous studies, and abundant todorokite and birnessite-like Mn oxides identified in 3 out of 4 specimens analyzed by Mn K-edge X-ray absorption spectroscopy (XAS) in the upper parts of the fracture network (down to 5 m). For a specimen with very high Ce concentration (1430 mg kg-1) and NASC-normalized Ce anomaly (3.63), the analysis of Ce XANES and Mn XAS data revealed (i) a predominance of Ce oxide in addition to Ce scavenged by Mn oxide; and (ii) a large fraction of poorly-crystalline hexagonal birnessite and aqueous Mn2+, suggesting a recent or on-going oxidation of Mn2+ in this fracture. In addition, the Ce oxide precipitates on this fracture observed by in situ SEM-EDS contained

  20. Humic Substances-dependent Aggregation and Transport of Cerium Oxide Nanoparticles in Porous Media at Different pHs and Ionic Strengths

    NASA Astrophysics Data System (ADS)

    Mu, L.; Jacobson, A. R.; Darnault, C. J. G.

    2015-12-01

    Cerium oxide nanoparticles (CeO2 NPs) are commonly used in several fields and industries, such as chemical and pharmaceutical, due to both their physical and chemical properties. For example, they are employed in the manufacturing of catalysts, as fuel additives, and as polishing agents. The release and exposure to CeO2 NPs can occur during their fabrication, application, and waste disposal, as well as through their life-cycle and accidents. Therefore, the assessment of the dynamic nature of CeO2 NPs stability and mobilty in the environment is of paramount importance to establish the environmental and public health risks associated with their inevitable release in the environment. Humic substances are a key element of soils and have been revealed to possibly affect the fate and transport of nanoparticles in soils. Consequently, our present research aims at investigating the influence that different pHs, monovalent and divalent cations, Suwannee River humic acid, and Suwanee River fulvic acid have on the aggregation, transport, and deposition of CeO2 NPs. Batch studies performed with different concentrations of humic and fulvic acids associated with a wide spectrum of pHs and ionic strengths were examined. Key variables from these batch studies were then examined to simulate experimental conditions commonly encountered in the soil-water system to conduct column transport experiments in order to establish the fate and transport of CeO2 NPs in saturated porous media, which is a critical phase in characterizing the behavior of CeO2 NPs in subsurface environmental systems.

  1. Tuning reactivity and electronic properties through ligand reorganization within a cerium heterobimetallic framework.

    PubMed

    Robinson, Jerome R; Gordon, Zachary; Booth, Corwin H; Carroll, Patrick J; Walsh, Patrick J; Schelter, Eric J

    2013-12-18

    Cerium compounds have played vital roles in organic, inorganic, and materials chemistry due to their reversible redox chemistry between trivalent and tetravalent oxidation states. However, attempts to rationally access molecular cerium complexes in both oxidation states have been frustrated by unpredictable reactivity in cerium(III) oxidation chemistry. Such oxidation reactions are limited by steric saturation at the metal ion, which can result in high energy activation barriers for electron transfer. An alternative approach has been realized using a rare earth/alkali metal/1,1'-BINOLate (REMB) heterobimetallic framework, which uses redox-inactive metals within the secondary coordination sphere to control ligand reorganization. The rational syntheses of functionalized cerium(IV) products and a mechanistic examination of the role of ligand reorganization in cerium(III) oxidation are presented.

  2. Tuning Reactivity and Electronic Properties through Ligand Reorganization within a Cerium Heterobimetallic Framework

    SciTech Connect

    Robinson, Jerome R.; Gordon, Zachary; Booth, Corwin H.; Carroll, Patrick J.; Walsh, Patrick J.; Schelter, Eric J.

    2014-06-24

    Cerium compounds have played vital roles in organic, inorganic, and materials chemistry due to their reversible redox chemistry between trivalent and tetravalent oxidation states. However, attempts to rationally access molecular cerium complexes in both oxidation states have been frustrated by unpredictable reactivity in cerium(III) oxidation chemistry. Such oxidation reactions are limited by steric saturation at the metal ion, which can result in high energy activation barriers for electron transfer. An alternative approach has been realized using a rare earth/alkali metal/1,1'-BINOLate (REMB) heterobimetallic framework, which uses redox-inactive metals within the secondary coordination sphere to control ligand reorganization. The rational syntheses of functionalized cerium(IV) products and a mechanistic examination of the role of ligand reorganization in cerium(III) oxidation are presented.

  3. The oxidation of water by cerium(IV) catalysed by nanoparticulate RuO2 on mesoporous silica.

    PubMed

    King, Nicola C; Dickinson, Calum; Zhou, Wuzong; Bruce, Duncan W

    2005-03-21

    Mesoporous silicates are prepared by templating on the hexagonal (H1) mesophase of surfactant bipyridine complexes of ruthenium(II) using a true liquid-crystal templating approach. On calcination, the surfactant template is removed except for the central metal ion that is oxidised, forming nanoparticles of RuO2 that deposit within the pores. RuO2 is a known oxidation catalyst and, despite its anhydrous nature in these silicates, is found to be very active in catalyzing the oxidation of water by acidic CeIV.

  4. Pharmacological potential of cerium oxidenanoparticles

    NASA Astrophysics Data System (ADS)

    Celardo, Ivana; Pedersen, Jens Z.; Traversa, Enrico; Ghibelli, Lina

    2011-04-01

    Nanotechnology promises a revolution in pharmacology to improve or create ex novo therapies. Cerium oxidenanoparticles (nanoceria), well-known as catalysts, possess an astonishing pharmacological potential due to their antioxidant properties, deriving from a fraction of Ce3+ ions present in CeO2. These defects, compensated by oxygen vacancies, are enriched at the surface and therefore in nanosized particles. Reactions involving redox cycles between the Ce3+ and Ce4+oxidation states allow nanoceria to react catalytically with superoxide and hydrogen peroxide, mimicking the behavior of two key antioxidant enzymes, superoxide dismutase and catalase, potentially abating all noxious intracellularreactive oxygen species (ROS) via a self-regenerating mechanism. Hence nanoceria, apparently well tolerated by the organism, might fight chronic inflammation and the pathologies associated with oxidative stress, which include cancer and neurodegeneration. Here we review the biological effects of nanoceria as they emerge from in vitro and in vivo studies, considering biocompatibility and the peculiar antioxidant mechanisms.

  5. Determination of chemical speciations of cerium in nuclear waste glasses

    SciTech Connect

    Gong, Meiling; Li, Hong

    1996-12-31

    Cerium oxides have been widely used as a surrogate for plutonium in the investigation of the melt and durability behavior of simulated nuclear waste glasses. It is well known that there is a cerous-ceric equilibrium in silicate glasses under normal melting conditions. The position of this equilibrium depends on glass composition, melting temperature, furnace atmosphere, and possibly the total amounts of cerium in glass. The oxidation state of cerium affects total solubility of cerium in glass, solubilities of other components in glass, viscosities and liquidus temperatures of the melts, and the chemical durability of the glasses. A procedure was developed for the determination of the ceric and cerous distribution. The glass was ground to small particles of less than 300 meshes and was dissolved in mixture of HF and H{sub 2}SO{sub 4}. The ceric oxide was graduately reduced to cerous species in the presence of HF acid during the dissolution. To compensate the change of the equilibrium during the dissolution, a calibration curve is made with a mixture of standard solution of ceric sulphate and one gram of glass of the same composition containing no cerium. Boric acid was added to complex the fluoride ions, and the resultant solution was titrated potentiometrically with 0.01 N ferrous ammonium sulphate solution. The corrected ceric concentration was obtained on the calibration curve. The total cerium content in the above solution was analyzed using ICP-AES and the cerous content was the difference between the total Ce and Ce(+4).

  6. Cerium neodymium oxide solid solution synthesis as a potential analogue for substoichiometric AmO2 for radioisotope power systems

    NASA Astrophysics Data System (ADS)

    Watkinson, E. J.; Ambrosi, R. M.; Williams, H. R.; Sarsfield, M. J.; Stephenson, K.; Weston, D. P.; Marsh, N.; Haidon, C.

    2017-04-01

    The European Space Agency (ESA) is sponsoring a research programme on the development of americium oxides for radioisotope generators and heater units. Cubic AmO2-(x/2) with an O/Am ratio between 1.65 and 1.75 is a potentially suitable compound for pellet sintering. C-type (Ia-3) Ce1-xNdxO2-(x/2) oxides with 0.5 < x < 0.7 could be used as a surrogate for some Ia-3 AmO2-(x/2). A new Ce1-xNdxO2-(x/2) production process has been investigated where a nominally selected x value of 0.6 was targeted: Ce and Nd nitrates and oxalic acid were added drop-wise into a vessel, where they continuously reacted to create oxalate precipitates. The effect of temperature (25 °C, 60 °C) of the reactants (mixed at 250 revolutions per minute) on oxalate particle shape and size were investigated. Oxalates were calcined at 900 °C to produce oxide particles. Oxalate particle properties were characterised as these are expected to influence oxides particle properties and fuel pellet sintering.

  7. Influence of a Cerium Surface Treatment on the Oxidation Behavior of Cr2O3-Forming Alloys (title on slides varies: Oxidation Behavior of Cerium Surface Treated Chromia Forming Alloys)

    SciTech Connect

    Alman, D.E.; Holcomb, G.R.; Adler, T.A.; Jablonski, P.D.

    2007-04-01

    Current goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives include coal generation at 60% efficiency, which would require steam temperatures of up to 760°C. This temperature will require the construction of boiler and turbine components from austenitic stainless steels and nickel alloys. Many of the alloys being considered for use are primarily Cr2O3 forming alloys [1-4]. It is well known that the addition of a small amount of reactive elements, such as the rare earths elements Ce, La, and Y, can significantly improve the high temperature oxidation resistance of both iron- and nickel- base alloys. A list of the benefits of the reactive element effect include: (i) slowing scale growth, (ii) enhancing scale adhesion; and (iii) stabilizing Cr2O3 formation at lower Cr levels. The incorporation of the reactive element can be made in the melt or through a surface infusion or surface coating. Surface modifications allow for the concentration of the reactive element at the surface where it can provide the most benefit. This paper will detail a Ce surface treatment developed at NETL that improves the high temperature oxidation resistance of Cr2O3 forming alloys. The treatment consists of painting, dip coating, or spraying the alloy surface with a slurry containing CeO2 and a halide activator followed by a thermal treatment in a mild (x10-3 Torr) vacuum. During treatment the CeO2 reacts with the alloy to for a thin CrCeO3-type scale on the alloy surface. Upon subsequent oxidation, scale growth occurs at a reduced rate on alloys in the surface treated condition compared to those in the untreated condition.

  8. Thermoelectric properties of cerium monopnictides

    NASA Technical Reports Server (NTRS)

    Danielson, L. R.; Alexander, M. N.; Wood, C.; Lockwood, R. A.; Vandersande, J. W.

    1987-01-01

    Several cerium pnictides have been synthesized from the pure elements and hot pressed into test samples. Measurements of Seebeck coefficients and electrical resistivities were performed on these samples from room temperature to 1000 C. Cerium arsenide and cerium antimonide are n-type; cerium nitride changes from p-type to n-type conduction at 800 C. The materials are semimetals with resistivities below 1 mohm/cm. Cerium arsenide is the most favorable of the pnictides studied for high-temperature thermoelectric energy conversion, with an average power factor of 15 microW/cm K sq from 500 to 1000 C.

  9. A cerium oxide nanoparticle-based device for the detection of chronic inflammation via optical and magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Kaittanis, Charalambos; Santra, Santimukul; Asati, Atul; Perez, J. Manuel

    2012-03-01

    Monitoring of microenvironmental parameters is critical in healthcare and disease management. Harnessing the antioxidant activity of nanoceria and the imaging capabilities of iron oxide nanoparticles in a device setup, we were able to image changes in the device's aqueous milieu. The device was able to convey and process changes in the microenvironment's pH and reactive oxygen species' concentration, distinguishing physiological from abnormal levels. As a result under physiological and transient inflammatory conditions, the device's fluorescence and magnetic resonance signals, emanating from multimodal iron oxide nanoparticles, were similar. However, under chronic inflammatory conditions that are usually associated with high local concentrations of reactive oxygen species and pH decrease, the device's output was considerably different. Specifically, the device's fluorescence emission significantly decreased, while the magnetic resonance signal T2 increased. Further studies identified that the changes in the device's output are attributed to inactivation of the sensing component's nanoceria that prevents it from successfully scavenging the generated free radicals. Interestingly, the buildup of free radical excess led to polymerization of the iron oxide nanoparticle's coating, with concomitant formation of micron size aggregates. Our studies indicate that a nanoceria-based device can be utilized for the monitoring of pro-inflammatory biomarkers, having important applications in the management of numerous ailments while eliminating nanoparticle toxicity issues.Monitoring of microenvironmental parameters is critical in healthcare and disease management. Harnessing the antioxidant activity of nanoceria and the imaging capabilities of iron oxide nanoparticles in a device setup, we were able to image changes in the device's aqueous milieu. The device was able to convey and process changes in the microenvironment's pH and reactive oxygen species' concentration

  10. Strain Field in Ultrasmall Gold Nanoparticles Supported on Cerium-Based Mixed Oxides. Key Influence of the Support Redox State.

    PubMed

    López-Haro, Miguel; Yoshida, Kenta; Del Río, Eloy; Pérez-Omil, José A; Boyes, Edward D; Trasobares, Susana; Zuo, Jian-Min; Gai, Pratibha L; Calvino, José J

    2016-05-03

    Using a method that combines experimental and simulated Aberration-Corrected High Resolution Electron Microscopy images with digital image processing and structure modeling, strain distribution maps within gold nanoparticles relevant to real powder type catalysts, i.e., smaller than 3 nm, and supported on a ceria-based mixed oxide have been determined. The influence of the reduction state of the support and particle size has been examined. In this respect, it has been proven that reduction even at low temperatures induces a much larger compressive strain on the first {111} planes at the interface. This increase in compression fully explains, in accordance with previous DFT calculations, the loss of CO adsorption capacity of the interface area previously reported for Au supported on ceria-based oxides.

  11. Synthesis of praseodymium doped cerium oxides by the polymerization-combustion method for application as anodic component in SOFC devices

    NASA Astrophysics Data System (ADS)

    Cruz Pacheco, A. F.; Gómez Cuaspud, J. A.; López, E. Vera

    2016-02-01

    This work reports the synthesis and the characterization of six oxides; it is based on Ce1-xPrxO2 (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) system, which is obtained by the polymerization- combustion technique for potential applications on design of advanced electrodic components, for solid oxide fuel cells (SOFC). Initially the solid precursors are characterized by infrared spectroscopy (FTIR) and thermal analysis (TGA-DTA), allowing to determine the formation of prevalent citrate species and the optimal temperature for the consolidation of the desired crystalline phases. The X-ray diffraction (XRD) and the transmission electron microscopy analysis (TEM) are performed over calcined samples which provided information about the formation of a fluorite phase with grain distribution, surface, textural and morphological properties consistent with the nanometric obtaining crystallites (30nm), it is oriented along the (1 1 1) facet, with d spacings of 0.31nm for the main diffraction signal. These results indicate the effectiveness of the proposed synthesis method for potential applications in the design of advanced anodic materials for solid oxide fuel cells.

  12. Redox Reactivity of Cerium Oxide Nanoparticles Induces the Formation of Disulfide Bridges in Thiol-Containing Biomolecules.

    PubMed

    Rollin-Genetet, Françoise; Seidel, Caroline; Artells, Ester; Auffan, Mélanie; Thiéry, Alain; Vidaud, Claude

    2015-12-21

    The redox state of disulfide bonds is implicated in many redox control systems, such as the cysteine-cystine couple. Among proteins, ubiquitous cysteine-rich metallothioneins possess thiolate metal binding groups susceptible to metal exchange in detoxification processes. CeO2 NPs are commonly used in various industrial applications due to their redox properties. These redox properties that enable dual oxidation states (Ce(IV)/Ce(III)) to exist at their surface may act as oxidants for biomolecules. The interaction among metallothioneins, cysteine, and CeO2 NPs was investigated through various biophysical approaches to shed light on the potential effects of the Ce(4+)/Ce(3+) redox system on the thiol groups of these biomolecules. The possible reaction mechanisms include the formation of a disulfide bridge/Ce(III) complex resulting from the interaction between Ce(IV) and the thiol groups, leading to metal unloading from the MTs, depending on their metal content and cluster type. The formation of stable Ce(3+) disulfide complexes has been demonstrated via their fluorescence properties. This work provides the first evidence of thiol concentration-dependent catalytic oxidation mechanisms between pristine CeO2 NPs and thiol-containing biomolecules.

  13. Cerium oxide nanoparticles, combining antioxidant and UV shielding properties, prevent UV-induced cell damage and mutagenesis

    NASA Astrophysics Data System (ADS)

    Caputo, Fanny; de Nicola, Milena; Sienkiewicz, Andrzej; Giovanetti, Anna; Bejarano, Ignacio; Licoccia, Silvia; Traversa, Enrico; Ghibelli, Lina

    2015-09-01

    Efficient inorganic UV shields, mostly based on refracting TiO2 particles, have dramatically changed the sun exposure habits. Unfortunately, health concerns have emerged from the pro-oxidant photocatalytic effect of UV-irradiated TiO2, which mediates toxic effects on cells. Therefore, improvements in cosmetic solar shield technology are a strong priority. CeO2 nanoparticles are not only UV refractors but also potent biological antioxidants due to the surface 3+/4+ valency switch, which confers anti-inflammatory, anti-ageing and therapeutic properties. Herein, UV irradiation protocols were set up, allowing selective study of the extra-shielding effects of CeO2vs. TiO2 nanoparticles on reporter cells. TiO2 irradiated with UV (especially UVA) exerted strong photocatalytic effects, superimposing their pro-oxidant, cell-damaging and mutagenic action when induced by UV, thereby worsening the UV toxicity. On the contrary, irradiated CeO2 nanoparticles, via their Ce3+/Ce4+ redox couple, exerted impressive protection on UV-treated cells, by buffering oxidation, preserving viability and proliferation, reducing DNA damage and accelerating repair; strikingly, they almost eliminated mutagenesis, thus acting as an important tool to prevent skin cancer. Interestingly, CeO2 nanoparticles also protect cells from the damage induced by irradiated TiO2, suggesting that these two particles may also complement their effects in solar lotions. CeO2 nanoparticles, which intrinsically couple UV shielding with biological and genetic protection, appear to be ideal candidates for next-generation sun shields.

  14. Visible light activated photocatalytic degradation of tetracycline by a magnetically separable composite photocatalyst: Graphene oxide/magnetite/cerium-doped titania.

    PubMed

    Cao, Muhan; Wang, Peifang; Ao, Yanhui; Wang, Chao; Hou, Jun; Qian, Jin

    2016-04-01

    In this study, magnetic graphene oxide-loaded Ce-doped titania (MGO-Ce-TiO2) hybridized composite was prepared by a facile method. The as-prepared samples exhibited good adsorption capacity, high visible-light photoactive and magnetic separability as a novel photocatalyst in the degradation of tetracyclines (TC). The intermediate products and photocatalytic route of TC were proposed based on the analysis results of LC-MS. Moreover, the repeatability of the photoactivity with the use of MGO-Ce-TiO2 was investigated in the multi-round experiments with the assistance of an applied magnetic field. Therefore, the prepared composite photocatalysts were considered as a kind of promising photocatalyst in a suspension reaction system, in which they can offer effectively recovery ability. The effect of MGO content on the photocatalytic performance was also studied, and an optimum content was obtained.

  15. Comparison of the high-pressure behavior of the cerium oxides Ce2O3 and CeO2

    DOE PAGES

    Lipp, M. J.; Jeffries, J. R.; Cynn, H.; ...

    2016-02-09

    We studied the high-pressure behavior of Ce2O3 using angle-dispersive x-ray diffraction to 70 GPa and compared with that of CeO2. Up to the highest pressure Ce2O3 remains in the hexagonal phase (space group 164, P ¯32/m1) typical for the lanthanide sesquioxides. We did not observe a theoretically predicted phase instability for 30 GPa. The isothermal bulk modulus and its pressure derivative for the quasihydrostatic case are B0 = 111 ± 2 GPa, B'0 = 4.7 ± 0.3, and for the case without pressure-transmitting medium B0 = 104 ±4 GPa, B'0 = 6.5 ± 0.4. Starting from ambient-pressure magnetic susceptibility measurementsmore » for both oxides in highly purified form,we find that the Ce atom in Ce2O3 behaves like a trivalent Ce3+ ion (2.57μB per Ce atom) in contrast to previously published data. Since x-ray emission spectroscopy of the Lγ (4d3/2 → 2p1/2) transition is sensitive to the 4f -electron occupancy, we also followed the high-pressure dependence of this line for both oxides up to 50 GPa. We observed no change of the respective line shape, indicating that the 4f -electron configuration is stable for both materials. We posit from this data that the 4f electrons do not drive the volume collapse of CeO2 from the high-symmetry, low-pressure fluorite structure to the lower-symmetry orthorhombic phase.« less

  16. Oxidation of glyoxylic acid by cerium(IV): Oxygen-induced enhancement of the primary radical concentration

    SciTech Connect

    Neumann, B. ||; Steinbock, O.; Dalal, N.S. |; Mueller, S.C. |||

    1996-07-25

    In order to help understand the role of oxygen in Ce(IV)-induced oxidation of small carbonic acids, we investigated the reaction of glyoxylic acid (HCOCOOH) and Ce(IV) in 1 M sulfuric acid. Spectrophotometric data showed that in excess of glyoxylic acid the consumption of Ce(IV) obeys pseudo-first-order kinetics, with a rate constant of 8.8 L mol{sup -1} s{sup -1} at 25{degree}C and an activation energy of 80 kJ mol{sup -1}. Rapid-flow EPR measurements revealed an approximately 1:2:1 triplet with a g value of 2.0071{+-}0.0005 and a hyperfine splitting of 7.1{+-}0.2 G, assignable to the primary radical formed by abstraction of a hydrogen atom from hydrated glyoxylic acid. The rate constant for the anaerobic self-decay of the radical was measured as approximately 3.7x10{sup 9} L mol{sup -1} s{sup -1}. Surprisingly, oxygen had no effect on the Ce(IV) kinetics, while the radical decay was significantly inhibited under aerobic conditions (ratio of experimental rate constants = 6.3). Amperometric measurements revealed accompanying oxygen consumption. Analyses based on numerical simulations show that the observed oxygen-induced increase in radical concentration cannot be explained in the framework of standard autooxidation mechanisms. An alternative reaction scheme is suggested which reproduces the observed aerobic radical kinetics and which thus could be relevant to similar oxidation reactions. 30 refs., 7 figs., 2 tabs.

  17. Direct Quantification of Rare Earth Elements Concentrations in Urine of Workers Manufacturing Cerium, Lanthanum Oxide Ultrafine and Nanoparticles by a Developed and Validated ICP-MS.

    PubMed

    Li, Yan; Yu, Hua; Zheng, Siqian; Miao, Yang; Yin, Shi; Li, Peng; Bian, Ying

    2016-03-22

    Rare earth elements (REEs) have undergone a steady spread in several industrial, agriculture and medical applications. With the aim of exploring a sensitive and reliable indicator of estimating exposure level to REEs, a simple, accurate and specific ICP-MS method for simultaneous direct quantification of 15 REEs ((89)Y, (139)La, (140)Ce, (141)Pr, (146)Nd, (147)Sm, (153)Eu, (157)Gd, (159)Tb, (163)Dy, (165)Ho, (166)Er, (169)Tm, (172)Yb and (175)Lu) in human urine has been developed and validated. The method showed good linearity for all REEs in human urine in the concentrations ranging from 0.001-1.000 μg ∙ L(-1) with r² > 0.997. The limits of detection and quantification for this method were in the range of 0.009-0.010 μg ∙ L(-1) and 0.029-0.037 μg ∙ L(-1), the recoveries on spiked samples of the 15 REEs ranged from 93.3% to 103.0% and the relative percentage differences were less than 6.2% in duplicate samples, and the intra- and inter-day variations of the analysis were less than 1.28% and less than 0.85% for all REEs, respectively. The developed method was successfully applied to the determination of 15 REEs in 31 urine samples obtained from the control subjects and the workers engaged in work with manufacturing of ultrafine and nanoparticles containing cerium and lanthanum oxide. The results suggested that only the urinary levels of La (1.234 ± 0.626 μg ∙ L(-1)), Ce (1.492 ± 0.995 μg ∙ L(-1)), Nd (0.014 ± 0.009 μg ∙ L(-1)) and Gd (0.023 ± 0.010 μg ∙ L(-1)) among the exposed workers were significantly higher (p < 0.05) than the levels measured in the control subjects. From these, La and Ce were the primary components, and accounted for 88% of the total REEs. Lanthanum comprised 27% of the total REEs while Ce made up the majority of REE content at 61%. The remaining elements only made up 1% each, with the exception of Dy which was not detected. Comparison with the previously published data, the levels of urinary La and Ce in workers and

  18. TU-F-CAMPUS-T-01: Potential of Using Cerium Oxide Nanoparticles (CONP) for Protecting Healthy Tissue During Accelerated Partial Breast Irradiation (APBI)

    SciTech Connect

    Mainali, M; Cifter, G

    2015-06-15

    Purpose: The purpose of this research is to investigate the feasibility of using targeted cerium oxide nanoparticles (CONP) during APBI to protect healthy cells. Methods: In one approach, CONP are assumed to be incorporated in a micrometer-thick polymer film on the surface of routinely used mammosite balloon applicators for sustained in-situ release of the CONP. In case two, CONPs are administered directly into the lumpectomy cavity. The concentration of H{sub 2}O{sub 2} produced by ionizing radiation was estimated from previously published work using short range linear extrapolation. The assessment of CONPs concentration required to absorb corresponding H{sub 2}O{sub 2} to protect healthy tissue was calculated. Fick’s Second law of diffusion was employed to determine the initial concentration of CONP needed to achieve the minimum concentration for radioprotection at distance 1 cm and 2 cm from the lumpectomy cavity during APBI. The study was carried out for different nanoparticle sizes. Results: The initial concentration of CONPs required to get desired radioprotection concentration at 1 cm and 2 cm after 7 days was found to be 0.4089 mg per Kg and 59.7605 g per Kg respectively for 2 nm size nanoparticles. Using concentrations of 5 mg per kg of CONP that have been shown to be used to confer radioprotection (for about 7.97 Gy) in experiments it was observed that 4.5631, 8.5286, 10.9247, 22.0408, 43.6796 and 65.5618 number of days are required to achieve radioprotection at 1 cm for CONP of sizes 2 nm, 3.8 nm, 5 nm, 10 nm, 20 nm, 30 nm, respectively. Conclusion: Our preliminary results show that smaller size (2 nm and 3.8 nm) CONP would be suitable as radio protectant during APBI because they took a reasonable number of days, i.e. less than 10 days to reach tissues of 1 cm or 2 cm thickness.

  19. Direct Quantification of Rare Earth Elements Concentrations in Urine of Workers Manufacturing Cerium, Lanthanum Oxide Ultrafine and Nanoparticles by a Developed and Validated ICP-MS

    PubMed Central

    Li, Yan; Yu, Hua; Zheng, Siqian; Miao, Yang; Yin, Shi; Li, Peng; Bian, Ying

    2016-01-01

    Rare earth elements (REEs) have undergone a steady spread in several industrial, agriculture and medical applications. With the aim of exploring a sensitive and reliable indicator of estimating exposure level to REEs, a simple, accurate and specific ICP-MS method for simultaneous direct quantification of 15 REEs (89Y, 139La, 140Ce, 141Pr, 146Nd, 147Sm, 153Eu, 157Gd, 159Tb, 163Dy, 165Ho, 166Er, 169Tm, 172Yb and 175Lu) in human urine has been developed and validated. The method showed good linearity for all REEs in human urine in the concentrations ranging from 0.001–1.000 μg∙L−1 with r2 > 0.997. The limits of detection and quantification for this method were in the range of 0.009–0.010 μg∙L−1 and 0.029–0.037 μg∙L−1, the recoveries on spiked samples of the 15 REEs ranged from 93.3% to 103.0% and the relative percentage differences were less than 6.2% in duplicate samples, and the intra- and inter-day variations of the analysis were less than 1.28% and less than 0.85% for all REEs, respectively. The developed method was successfully applied to the determination of 15 REEs in 31 urine samples obtained from the control subjects and the workers engaged in work with manufacturing of ultrafine and nanoparticles containing cerium and lanthanum oxide. The results suggested that only the urinary levels of La (1.234 ± 0.626 μg∙L−1), Ce (1.492 ± 0.995 μg∙L−1), Nd (0.014 ± 0.009 μg∙L−1) and Gd (0.023 ± 0.010 μg∙L−1) among the exposed workers were significantly higher (p < 0.05) than the levels measured in the control subjects. From these, La and Ce were the primary components, and accounted for 88% of the total REEs. Lanthanum comprised 27% of the total REEs while Ce made up the majority of REE content at 61%. The remaining elements only made up 1% each, with the exception of Dy which was not detected. Comparison with the previously published data, the levels of urinary La and Ce in workers and the control subjects show a higher trend

  20. Multi-wall carbon nanotubes as support of copper-cerium composite for preferential oxidation of carbon monoxide

    NASA Astrophysics Data System (ADS)

    Zeng, Shanghong; Zhang, Lu; Jiang, Nan; Gao, Meiyi; Zhao, Xiaozhou; Yin, Yueling; Su, Haiquan

    2015-10-01

    The CuxO/MWCNTs, CeO2/MWCNTs and CuxO-CeO2/MWCNTs catalysts were synthesized by a simple impregnation method, and characterized via X-ray diffraction, N2 adsorption-desorption, Fourier transformed infrared spectroscopy, transmission electron microscopy, H2 temperature-programmed reduction and X-ray photoelectron spectra. The catalytic performance for preferential CO oxidation was carried out in the hydrogen-rich gasses. It is found that the hydrophilic functional groups of hydroxyl and carboxyl in the samples are favorable for the incorporation of CuxO and CeO2 into the tubes of the MWCNTs. Most of CuxO particles and CeO2 nanowires are filled in the tubes of MWCNTs, and a small amount of nanoparticles are deposited on the surface of MWCNTs. The MWCNTs have high BET surface area, which is helpful for the dispersion of CuxO and CeO2 to expose more active surface for CO-PROX reaction over the CuxO-CeO2/MWCNTs catalysts. The CuxO-CeO2/MWCNTs-C catalyst shows good catalytic activity and the temperature window of CO total conversion is from 135 °C to 175 °C. MWCNTs with high BET surface area weaken poisoning effect of H2O and CO2 after 135 °C.

  1. Hydrocarbon-based polymer electrolyte cerium composite membranes for improved proton exchange membrane fuel cell durability

    NASA Astrophysics Data System (ADS)

    Lee, Hyejin; Han, Myungseong; Choi, Young-Woo; Bae, Byungchan

    2015-11-01

    Hydrocarbon-based cerium composite membranes were prepared for proton exchange membrane fuel cell applications to increase oxidative stability. Different amounts of cerium ions were impregnated in sulfonated poly(arylene ether sulfone) (SPES) membranes and their physicochemical properties were investigated according to the cerium content. Field-emission scanning electron microscopy and inductively coupled plasma analyses confirmed the presence of cerium ions in the composite membranes and 1H NMR indicated the successful coordination of sulfonic acid groups with the metal ions. Increasing amounts of cerium ions resulted in decreases in the proton conductivity and water uptake, but enhanced oxidative stability. The oxidative stability of the composite membranes was proven via a hydrogen peroxide exposure experiment which mimicked fuel cell operating conditions. In addition, more than 2200 h was achieved with the composite membrane under in situ accelerated open circuit voltage (OCV) durability testing (DOE protocol), whereas the corresponding pristine SPES membrane attained only 670 h.

  2. In vitro skin decontamination of the organophosphorus pesticide Paraoxon with nanometric cerium oxide CeO2.

    PubMed

    Salerno, Alicia; Devers, Thierry; Bolzinger, Marie-Alexandrine; Pelletier, Jocelyne; Josse, Denis; Briançon, Stéphanie

    2017-04-01

    Organophosphorus compounds (OP), which mainly penetrate via the percutaneous pathway, represent a threat for both military and civilians. Body surface decontamination is vital to prevent victims poisoning. The development of a cost-effective formulation, which could be efficient and easy to handle in case of mass contamination, is therefore crucial. Metal oxides nanoparticles, due their large surface areas and the large amount of highly reactive sites, present high reactivity towards OP. First, this study aimed at evaluating the reaction of CeO2 nanoparticles, synthetized by microwave path and calcined at 500 or 600 °C, with Paraoxon (POX) in aqueous solution. Results showed that both nanoparticles degraded 60%-70% of POX. CeO2 calcined at 500 °C, owing to its larger specific area, was the most effective. Moreover, the degradation was significantly increased under Ultra-Violet irradiation (initial degradation rate doubled). Then, skin decontamination was studied in vitro using the Franz cell method with pig-ear skin samples. CeO2 powder and an aqueous suspension of CeO2 (CeO2-W) were applied 1 h after POX exposure. The efficiency of decontamination, including removal and/or degradation of POX, was compared to Fuller's earth (FE) and RSDL lotion which are, currently, the most efficient systems for skin decontamination. CeO2-W and RSDL were the most efficient to remove POX from the skin surface and decrease skin absorption by 6.4 compared to the control not decontaminated. FE reduced significantly (twice) the absorbed fraction of POX, contrarily to CeO2 powder. Considering only the degradation rate of POX, the products ranged in the order CeO2 > RSDL > CeO2-W > FE (no degradation). This study showed that CeO2 nanoparticles are a promising material for skin decontamination of OP if formulated as a dispersion able to remove POX like CeO2-W and to degrade it as CeO2 powder.

  3. Photoemission study of cerium silicate model systems

    NASA Astrophysics Data System (ADS)

    Skála, Tomáš; Matolín, Vladimír

    2013-01-01

    Interaction of silicon with cerium oxide was studied by photoelectron spectroscopy using two model systems CeOx/Si(1 1 1) and Si/CeO2(1 1 1)/Cu(1 1 1) which can be used for fundamental studies in the field of microelectronics and heterogeneous catalysis. The interaction was found to be strong and lead to a formation of cerium silicate films of the proposed stoichiometry Ce4.67Si3O13. Their maximum thickness was limited by diffusion of silicon. Beside silicate other compounds were growing on the surface - SiO2, Si2O, Si, and CeO2. The assignment of the formed species is based on the interpretation of photoemission spectra involving the measurements of various reference O/Si and Sisbnd O/Cu systems.

  4. Ultrathin, epitaxial cerium dioxide on silicon

    SciTech Connect

    Flege, Jan Ingo Kaemena, Björn; Höcker, Jan; Schmidt, Thomas; Falta, Jens; Bertram, Florian; Wollschläger, Joachim

    2014-03-31

    It is shown that ultrathin, highly ordered, continuous films of cerium dioxide may be prepared on silicon following substrate prepassivation using an atomic layer of chlorine. The as-deposited, few-nanometer-thin Ce{sub 2}O{sub 3} film may very effectively be converted at room temperature to almost fully oxidized CeO{sub 2} by simple exposure to air, as demonstrated by hard X-ray photoemission spectroscopy and X-ray diffraction. This post-oxidation process essentially results in a negligible loss in film crystallinity and interface abruptness.

  5. Fenton-Like Reaction Catalyzed by the Rare Earth Inner Transition Metal Cerium

    PubMed Central

    HECKERT, ERIC G.; SEAL, SUDIPTA; SELF, WILLIAM T.

    2011-01-01

    Cerium (Ce) is a rare earth metal that is not known to have any biological role. Cerium oxide materials of several sizes and shapes have been developed in recent years as a scaffold for catalysts. Indeed even cerium oxide nanoparticles themselves have displayed catalytic activities and antioxidant properties in tissue culture and animal models. Because of ceria's ability to cycle between the +3 and +4 states at oxygen vacancy sites, we investigated whether cerium metal would catalyze a Fenton-like reaction with hydrogen peroxide. Indeed, cerium chloride did exhibit radical production in the presence of hydrogen peroxide, as assessed by relaxation of supercoiled plasmid DNA. Radical production in this reaction was also followed by production of radical cation of 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS). Radical scavengers and spin traps were capable of competing with ABTS for radicals produced in this cerium dependent Fenton-like reaction. Electron paramagnetic resonance experiments reveal both hydroxyl radical and superoxide anion in a reaction containing cerium and hydrogen peroxide. Based on these results we propose that cerium is capable of redox-cycling with peroxide to generate damaging oxygen radicals. PMID:18678042

  6. Fenton-like reaction catalyzed by the rare earth inner transition metal cerium.

    PubMed

    Heckert, Eric G; Seal, Sudipta; Self, William T

    2008-07-01

    Cerium (Ce) is a rare earth metal that is not known to have any biological role. Cerium oxide materials of several sizes and shapes have been developed in recent years as a scaffold for catalysts. Indeed even cerium oxide nanoparticles themselves have displayed catalytic activities and antioxidant properties in tissue culture and animal models. Because of ceria's ability to cycle between the +3 and +4 states at oxygen vacancy sites, we investigated whether cerium metal would catalyze a Fenton-like reaction with hydrogen peroxide. Indeed, cerium chloride did exhibit radical production in the presence of hydrogen peroxide, as assessed by relaxation of supercoiled plasmid DNA. Radical production in this reaction was also followed by production of radical cation of 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS). Radical scavengers and spin traps were capable of competing with ABTS for radicals produced in this cerium dependent Fenton-like reaction. Electron paramagnetic resonance experiments reveal both hydroxyl radical and superoxide anion in a reaction containing cerium and hydrogen peroxide. Based on these results we propose that cerium is capable of redox-cycling with peroxide to generate damaging oxygen radicals.

  7. Lanthanum Cerium Manganese Hexaaluminate Combustion Catalysts for Compact Steam Reformers

    DTIC Science & Technology

    2005-12-07

    monoxide, and ethylene as partial oxidation products. Of the metals tested, iron is best, followed by cobalt and cerium. Our results concur with Wang et...that of Groppi et al., which marginally outperformed LaMnAl11O19 [15]. Our bimetallic manganese- cobalt catalyst was similarly lacking and did not...LaCo0.5Mn0.5Al11O19 are nearly identical and that in the absence of manganese, cobalt - and cerium-substituted hexaaluminates are equivalent catalysts. It

  8. Potential for recovery of cerium contained in automotive catalytic converters

    USGS Publications Warehouse

    Bleiwas, Donald I.

    2013-01-01

    Catalytic converters (CATCONs) are required by Federal law to be installed in nearly all gasoline- and diesel-fueled onroad vehicles used in the United States. About 85 percent of the light-duty vehicles and trucks manufactured worldwide are equipped with CATCONs. Portions of the CATCONs (called monoliths) are recycled for their platinum-group metal (PGM) content and for the value of the stainless steel they contain. The cerium contained in the monoliths, however, is disposed of along with the slag produced from the recycling process. Although there is some smelter capacity in the United States to treat the monoliths in order to recover the PGMs, a great percentage of monoliths is exported to Europe and South Africa for recycling, and a lesser amount is exported to Japan. There is presently no commercial-scale capacity in place domestically to recover cerium from the monoliths. Recycling of cerium or cerium compounds from the monoliths could help ensure against possible global supply shortages by increasing the amount that is available in the supply chain as well as the number and geographic distribution of the suppliers. It could also reduce the amount of material that goes into landfills. Also, the additional supply could lower the price of the commodity. This report analyzes how much cerium oxide is contained in CATCONs and how much could be recovered from used CATCONs.

  9. Cerium doped red mud catalytic ozonation for bezafibrate degradation in wastewater: Efficiency, intermediates, and toxicity.

    PubMed

    Xu, Bingbing; Qi, Fei; Sun, Dezhi; Chen, Zhonglin; Robert, Didier

    2016-03-01

    In this study, the performance of bezafibrate (BZF) degradation and detoxification in the aqueous phase using cerium-modified red mud (RM) catalysts prepared using different cerium sources and synthesis methods were evaluated. Experimental results showed that the surface cerium modification was responsible for the development of the catalytic activity of RM and this was influenced by the cerium source and the synthesis method. Catalyst prepared from cerium (IV) by precipitation was found to show the best catalytic activity in BZF degradation and detoxification. Reactive oxygen species including peroxides, hydroxyl radicals, and super oxide ions were identified in all reactions and we proposed the corresponding catalytic reaction mechanism for each catalyst that prepared from different cerium source and method. This was supported by the intermediates profiles that were generated upon BZF degradation. The surface and the structural properties of cerium-modified RM were characterized in detail by several analytical methods. Two interesting findings were made: (1) the surface texture (specific surface area and mesoporous volume) influenced the catalytic reaction pathway; and (2) Ce(III) species and oxygen vacancies were generated on the surface of the catalyst after cerium modification. This plays an important role in the development of the catalytic activity.

  10. Thermodynamic Calculation among Cerium, Oxygen, and Sulfur in Liquid Iron

    NASA Astrophysics Data System (ADS)

    Pan, Fei; Zhang, Jian; Chen, Hao-Long; Su, Yen-Hsun; Su, Yen-Hao; Hwang, Weng-Sing

    2016-10-01

    Thermodynamic calculation has been applied to predict the inclusion formation in molten SS400 steel. When the Cerium addition in liquid iron is 70 ppm and the initial Oxygen and Sulphur are both 110 ppm, the formation of oxides containing Cerium would experience the transformation from Ce2O3 to CeO2 and also the formation of sulfides containing Cerium would experience the transformation from CeS to Ce2S3 and then to Ce3S4. Below 2000 K the most thermodynamic stable matter is CeO2 and the less thermodynamic stable inclusion is CeS. Only when the amount of [O] is extremely low and the amount of [S] and [Ce] is relatively high, Ce2S3 has the possibility to form.

  11. Thermodynamic Calculation among Cerium, Oxygen, and Sulfur in Liquid Iron

    PubMed Central

    Pan, Fei; Zhang, Jian; Chen, Hao-Long; Su, Yen-Hsun; Su, Yen-Hao; Hwang, Weng-Sing

    2016-01-01

    Thermodynamic calculation has been applied to predict the inclusion formation in molten SS400 steel. When the Cerium addition in liquid iron is 70 ppm and the initial Oxygen and Sulphur are both 110 ppm, the formation of oxides containing Cerium would experience the transformation from Ce2O3 to CeO2 and also the formation of sulfides containing Cerium would experience the transformation from CeS to Ce2S3 and then to Ce3S4. Below 2000 K the most thermodynamic stable matter is CeO2 and the less thermodynamic stable inclusion is CeS. Only when the amount of [O] is extremely low and the amount of [S] and [Ce] is relatively high, Ce2S3 has the possibility to form. PMID:27767092

  12. The influence of the nature of the metal on the performance of cerium oxide supported catalysts in the partial oxidation of ethanol

    NASA Astrophysics Data System (ADS)

    Mattos, L. V.; Noronha, F. B.

    This work studied the effect of the nature of the metal on the performance of Co/CeO 2, Pd/CeO 2 and Pt/CeO 2 catalysts in the partial oxidation of ethanol. Infrared spectroscopy of adsorbed ethanol and temperature programmed desorption of ethanol were performed in order to establish the reaction mechanism. Catalytic experiments revealed that the product distribution is strongly affected by the nature of the metal. Acetaldehyde was practically the only product formed on a Co/CeO 2 catalyst while methane was also produced on Pt/CeO 2 and Pd/CeO 2 catalysts. These results were explained through a reaction mechanism proposed by the characterization techniques. Co/CeO 2 and Pt/CeO 2 catalysts show mainly ethoxy species at room temperature whereas acetate species is mainly formed on the Pd/CeO 2 catalyst. The ethoxy species can undergo further dehydrogenation and desorb as acetaldehyde. This effect is more significant with the Co/CeO 2 catalyst and could explain the higher selectivity to acetaldehyde observed on supported Co and Pt catalysts.

  13. Molecular and electronic structures of cerium and cerium suboxide clusters

    NASA Astrophysics Data System (ADS)

    Kafader, Jared O.; Topolski, Josey E.; Jarrold, Caroline Chick

    2016-10-01

    The anion photoelectron (PE) spectra of Ce2Oy- (y = 1, 2), Ce3Oy- (y = 0-4), Ce4Oy- (y = 0-2), and Ce5Oy- (y = 1, 2) are reported and analyzed with supporting results from density functional theory calculations. The PE spectra all exhibit an intense electronic transition to the neutral ground state, all falling in the range of 0.7 to 1.1 eV electron binding energy, with polarization dependence consistent with detachment from diffuse Ce 6s-based molecular orbitals. There is no monotonic increase in electron affinity with increasing oxidation. A qualitative picture of how electronic structure evolves with an oxidation state emerges from comparison between the spectra and the computational results. The electronic structure of the smallest metallic cluster observed in this study, Ce3, is similar to the bulk structure in terms of atomic orbital occupancy (4f 5d2 6s). Initial cerium cluster oxidation involves largely ionic bond formation via Ce 5d and O 2p orbital overlap (i.e., larger O 2p contribution), with Ce—O—Ce bridge bonding favored over Ce=O terminal bond formation. With subsequent oxidation, the Ce 5d-based molecular orbitals are depleted of electrons, with the highest occupied orbitals described as diffuse Ce 6s based molecular orbitals. In the y ≤ (x + 1) range of oxidation states, each Ce center has a singly occupied non-bonding 4f orbital. The PE spectrum of Ce3O4- is unique in that it exhibits a single nearly vertical transition. The highly symmetric structure predicted computationally is the same structure determined from Ce3O4+ IR predissociation spectra [A. M. Burow et al., Phys. Chem. Chem. Phys. 13, 19393 (2011)], indicating that this structure is stable in -1, 0, and +1 charge states. Spectra of clusters with x ≥ 3 exhibit considerable continuum signal above the ground state transition; the intensity of the continuum signal decreases with increasing oxidation. This feature is likely the result of numerous quasi-bound anion states or two

  14. Microstructure of surface cerium hydride growth sites

    SciTech Connect

    Brierley, Martin; Knowles, John; Montgomery, Neil; Preuss, Michael

    2014-05-15

    Samples of cerium were exposed to hydrogen under controlled conditions causing cerium hydride sites to nucleate and grow on the surface. The hydriding rate was measured in situ, and the hydrides were characterised using secondary ion mass spectrometry, scanning electron microscopy, and optical microscopy. The results show that the hydriding rate proceeded more quickly than earlier studies. Characterisation confirmed that the hydrogen is confined to the sites. The morphology of the hydrides was confirmed to be oblate, and stressed material was observed surrounding the hydride, in a number of cases lathlike features were observed surrounding the hydride sites laterally with cracking in the surface oxide above them. It is proposed that during growth the increased lattice parameter of the CeH{sub 2} induces a lateral compressive stress around the hydride, which relieves by the ca. 16% volume collapse of the γ-Ce to α-Ce pressure induced phase transition. Cracking of the surface oxide above the laths reduces the diffusion barrier to hydrogen reaching the metal/oxide interface surrounding the hydride site and contributes to the anisotropic growth of the hydrides.

  15. Purification of cerium, neodymium and gadolinium for low background experiments

    NASA Astrophysics Data System (ADS)

    Boiko, R. S.; Barabash, A. S.; Belli, P.; Bernabei, R.; Cappella, F.; Cerulli, R.; Danevich, F. A.; Incicchitti, A.; Laubenstein, M.; Mokina, V. M.; Nisi, S.; Poda, D. V.; Polischuk, O. G.; Tretyak, V. I.

    2014-01-01

    Cerium, neodymium and gadolinium contain double beta active isotopes. The most interesting are 150Nd and 160Gd (promising for 0ν2β search), 136Ce (2β+ candidate with one of the highest Q2β). The main problem of compounds containing lanthanide elements is their high radioactive contamination by uranium, radium, actinium and thorium. The new generation 2β experiments require development of methods for a deep purification of lanthanides from the radioactive elements. A combination of physical and chemical methods was applied to purify cerium, neodymium and gadolinium. Liquid-liquid extraction technique was used to remove traces of Th and U from neodymium, gadolinium and for purification of cerium from Th, U, Ra and K. Co-precipitation and recrystallization methods were utilized for further reduction of the impurities. The radioactive contamination of the samples before and after the purification was tested by using ultra-low-background HPGe gamma spectrometry. As a result of the purification procedure the radioactive contamination of gadolinium oxide (a similar purification efficiency was reached also with cerium and neodymium oxides) was decreased from 0.12 Bq/kg to 0.007 Bq/kg in 228Th, from 0.04 Bq/kg to <0.006 Bq/kg in 226Ra, and from 0.9 Bq/kg to 0.04 Bq/kg in 40K. The purification methods are much less efficient for chemically very similar radioactive elements like actinium, lanthanum and lutetium.

  16. Preparation of cerium halide solvate complexes

    SciTech Connect

    Vasudevan, Kalyan V; Smith, Nickolaus A; Gordon, John C; McKigney, Edward A; Muenchaussen, Ross E

    2013-08-06

    Crystals of a solvated cerium(III) halide solvate complex resulted from a process of forming a paste of a cerium(III) halide in an ionic liquid, adding a solvent to the paste, removing any undissolved solid, and then cooling the liquid phase. Diffusing a solvent vapor into the liquid phase also resulted in crystals of a solvated cerium(III) halide complex.

  17. PLUTONIUM-CERIUM-COBALT AND PLUTONIUM-CERIUM-NICKEL ALLOYS

    DOEpatents

    Coffinberry, A.S.

    1959-08-25

    >New plutonium-base teroary alloys useful as liquid reactor fuels are described. The alloys consist of 10 to 20 atomic percent cobalt with the remainder plutonium and cerium in any desired proportion, with the plutonium not in excess of 88 atomic percent; or, of from 10 to 25 atomic percent nickel (or mixture of nickel and cobalt) with the remainder plutonium and cerium in any desired proportion, with the plutonium not in excess of 86 atomic percent. The stated advantages of these alloys over unalloyed plutonium for reactor fuel use are a lower melting point and a wide range of permissible plutonium dilution.

  18. Cyclic thermochemical process for producing hydrogen using cerium-titanium compounds

    DOEpatents

    Bamberger, Carlos E.

    1980-01-01

    A thermochemical cyclic process for producing hydrogen employs the reaction between ceric oxide and titanium dioxide to form cerium titanate and oxygen. The titanate is treated with an alkali metal hydroxide to give hydrogen, ceric oxide, an alkali metal titanate and water. Alkali metal titanate and water are boiled to give titanium dioxide which, along with ceric oxide, is recycled.

  19. Cyclic thermochemical process for producing hydrogen using cerium-titanium compounds

    DOEpatents

    Bamberger, C.E.

    A thermochemical cyclic process for producing hydrogen employs the reaction between ceric oxide and titanium dioxide to form cerium titanate and oxygen. The titanate is treated with an alkali metal hydroxide to give hydrogen, ceric oxide, an alkali metal titanate and water. Alkali metal titanate and water are boiled to give titanium dioxide which, along with ceric oxide, is recycled.

  20. An investigation on the influence of milling time and calcination temperature on the characterization of nano cerium oxide powder synthesized by mechanochemical route

    SciTech Connect

    Aminzare, M.; Amoozegar, Z.; Sadrnezhaad, S.K.

    2012-11-15

    Highlights: ► Synthesis of nanosized CeO{sub 2} was carried out using mechanochemical reactions plus sequential calcinations procedure. ► The effect of milling time and calcinations procedure on crystallite size and surface area of the as-synthesized powders was investigated. ► The extended milling times were exposed to result in the smaller crystallite size, and hence higher surface area for the as-synthesized powder. ► Higher calcinations temperatures, on the other hand, led to the as-synthesized powder with a larger crystallite size and therefore, lower surface area. ► Activation energy for nanocrystallite growth was calculated during the calcinations procedure and the aforementioned crystallite growth was found to be conducted in the light of interfacial reactions. -- Abstract: The synthesis of nano-sized CeO{sub 2} powder was investigated via mechanochemical reactions between hydrate cerium chloride and sodium hydroxide as the starting materials. The process was followed by a subsequent calcination procedure. Characterization of as-synthesized powder was performed using X-ray diffraction, FTIR spectroscopy, Brunner–Emmett–Teller (BET) nitrogen gas absorption, scanning electron microscopy (SEM) and particle size analyzer (PSA). The precursors were milled for different milling times and then were subjected to different heat treatment procedure at variable temperatures from 100 to 700 °C. According to the results, milling time and calcination temperatures induce paramountal effects on crystallite size and surface area of as-synthesized powders. In addition, the average activation energy for the growth of nanocrystals during calcination was determined to be about 12.53 kJ/mol, suggesting the influence of interfacial reactions on the crystallite growth during the calcination procedure.

  1. PLUTONIUM-CERIUM-COPPER ALLOYS

    DOEpatents

    Coffinberry, A.S.

    1959-05-12

    A low melting point plutonium alloy useful as fuel is a homogeneous liquid metal fueled nuclear reactor is described. Vessels of tungsten or tantalum are useful to contain the alloy which consists essentially of from 10 to 30 atomic per cent copper and the balance plutonium and cerium. with the plutontum not in excess of 50 atomic per cent.

  2. Synthesis, electrochemistry, and reactivity of cerium(III/IV) methylene-bis-phenolate complexes.

    PubMed

    Mahoney, Brian D; Piro, Nicholas A; Carroll, Patrick J; Schelter, Eric J

    2013-05-20

    A series of cerium complexes containing a 2,2'-methylenebis(6-tert-butyl-4-methylphenolate) (MBP(2-)) ligand framework is described. Electrochemical studies of the compound [Li(THF)2Ce(MBP)2(THF)2] (1) reveal that the metal based oxidation wave occurs at -0.93 V vs Fc/Fc(+). This potential demonstrates significant stabilization of the cerium(IV) ion in the MBP(2-) framework with a shift of ∼2.25 V from the typically reported value for the cerium(III/IV) couple of E°' = +1.30 V vs Fc/Fc(+) for Ce(ClO4)3 in HClO4 solutions. Compound 1 undergoes oxidation to form stable cerium(IV) species in the presence of a variety of common oxidants. The coordination of the redox-active ligands 2,2'-bipyridine and benzophenone to 1 result in complexes in which no apparent metal-to-ligand charge transfer occurs and the cerium ion remains in the +3 oxidation state.

  3. Photoionization of the cerium isonuclear sequence and cerium endohedral fullerene

    NASA Astrophysics Data System (ADS)

    Habibi, Mustapha

    This dissertation presents an experimental photoionization study of the cerium isonuclear sequence ions in the energy range of the 4d inner-shell giant resonance. In addition, single and double photoionization and photofragmentation cross sections of the cerium endohedral ion Ce C+82 were also measured and studied in the 4d excitation-ionization energy range of cerium. Relative and absolute cross-section measurements were performed at undulator beamline 10.0.1 of the Advanced Light Source (ALS) for nine parent cerium ions: Ce+ - Ce9+. Double-to-single ionization cross-section ratios were measured for photoionization of the endohedral Ce C+82 and empty fullerene C C+82 molecular ions. The merged ion and photon beams technique was used to conduct the experiments. Multiconfiguration Hartree-Fock calculations were performed as an aid to interpret the experimental data. Four Rydberg series for 4d → nf (n ≥ 4) and 4d → np (n ≥ 6) autoionizing excitations were assigned using the quantum defect theory for the Ce3+ photoionization cross section. The experimental data show the collapse of the nf wavefunctions (n ≥ 4) with increasing ionization stage as outer-shell electrons are stripped from the parent ion. The nf orbital collapse occurs partially for Ce2+ and Ce3+ ion and completely for Ce4+, where these wavefunctions penetrate the core region of the ion. A strong contribution to the total oscillator strength was observed in the double and triple photoionization channels for low charge states (Ce +, Ce2+, and Ce3+), whereas most of the 4d excitations of the higher charge states decay by ejection of one electron.

  4. Oxidation of alginate and pectate biopolymers by cerium(IV) in perchloric and sulfuric acid solutions: A comparative kinetic and mechanistic study.

    PubMed

    Fawzy, Ahmed

    2016-03-15

    The kinetics of oxidation of alginate (Alg) and pectate (Pec) carbohydrate biopolymers was studied by spectrophotometry in aqueous perchloric and sulfuric acid solutions at fixed ionic strengths and temperature. In both acids, the reactions showed a first order dependence on [Ce(IV)], whereas the orders with respect to biopolymer concentrations are less than unity. In perchloric acid, the reactions exhibited less than unit orders with respect to [H(+)] whereas those proceeded in sulfuric acid showed negative fractional-first order dependences on [H(+)]. The effect of ionic strength and dielectric constant was studied. Probable mechanistic schemes for oxidation reactions were proposed. In both acids, the final oxidation products were characterized as mono-keto derivatives of both biopolymers. The activation parameters with respect to the slow step of the mechanisms were computed and discussed. The rate laws were derived and the reaction constants involved in the different steps of the mechanisms were calculated.

  5. Preparation of yttrium, lanthanum, cerium, and neodymium basic carbonate particles by homogeneous precipitation

    SciTech Connect

    Akinc, M.; Sordelet, D. )

    1987-07-01

    Uniform yttrium, lanthanum, cerium, and neodymium basic carbonate particles were prepared by homogeneous precipitation. Powders were characterized with respect to size, shape, crystal structure, and thermal decomposition behavior. Yttria precursor particles were spherical, monosized (0.4 {mu}m), and amorphous; whereas lanthana, neodymia, and ceria precursors were prismatic (ranging from 1 to 6 {mu}m in size) and crystalline. Crystal structure was found to be ancylite-type orthorhombic symmetry in all three cases. Upon heating in air, yttrium, lanthanum, and neodymium precursors underwent two-step decomposition to first form oxycarbonate and then oxide. Cerium hydroxycarbonate decomposed in a single step to form the oxide.

  6. Exposure and Health Effects Review of Engineered Nanoscale Cerium and Cerium Dioxide Associated with its Use as a Fuel Additive - NOW IN PRINT IN THE JOURNAL

    EPA Science Inventory

    Advances of nanoscale science have produced nanomaterials with unique physical and chemical properties at commercial levels that are now incorporated into over 1000 products. Nanoscale cerium (di) oxide (Ce02) has recently gained a wide range of applications which includes coatin...

  7. Investigation of the Effect of Yttrium Oxide Nanoparticles Doped with Cerium and Neodymium on Electro-Optics of Liquid Crystal Polymer Composites

    NASA Astrophysics Data System (ADS)

    Zharkova, G. M.; Osipov, V. V.; Platonov, V. V.; Podkin, A. V.; Strel'tsov, S. A.

    2016-12-01

    Morphology and properties of liquid crystal polymer composites doped with inorganic nanoparticles are described. These composites comprised nematic liquid crystal 5CB, polyvinyl acetate, and nanoparticles of oxides (Y2O3, CeO2:Y2O3, and Nd2O3:Y2O3). Nanopowders were synthesized by the laser method of vaporization of a solid target under CO2-laser or fiber ytterbium laser irradiation. The effect of oxides on the electro-optical properties of the composites and times of response to an electrical pulse is investigated. It is shown that incorporation of CeO2:Y2O3 nanopowder in liquid crystal polymer composites affects the decrease of the control field and the increase of light transmission in an electric field stronger than incorporation of Nd2O3:Y2O3 nanoparticles.

  8. Decomposition kinetics of ammonia in gaseous stream by a nanoscale copper-cerium bimetallic catalyst.

    PubMed

    Hung, Chang-Mao

    2008-01-15

    This study performance is to examine the kinetics over nanoscale copper-cerium bimetallic catalyst under selective catalytic oxidation (SCO) of ammonia to N(2) in a tubular fixed-bed reactor (TFBR) at temperatures from 150 to 400 degrees C in the presence of oxygen. The nanoscale copper-cerium bimetallic catalyst was prepared by co-precipitation with Cu(NO(3))(2) and Ce(NO(3))(3) at molar ratio of 6:4. Experimental results showed that the catalyst with transmission electron microscopy (TEM) revealed that copper and cerium are well dispersed and catalyst in the form of nanometer-sized particles. Moreover, the kinetic behavior of NH(3) oxidation with catalysis can be accounted by using the rate expression of the Langmuir-Hinshelwood type kinetic model. Kinetic parameters are also developed on the basis of the differential reactor data. Also, experimental results are compared with those of the model predicted.

  9. ADSORPTION OF CERIUM VALUES FROM AQUEOUS SOLUTIONS

    DOEpatents

    Roberts, F.P.

    1963-08-13

    Cerium can be removed from aqueous nitric acid (2 to 13 M) solutions by passing the latter over a PbO/sub 2/-containing anion exchange resin. The cerium is taken up by the resin, while any lanthanides, yttrium, and strontium present remain in the solution. (AEC)

  10. A model cerium oxide matrix composite reinforced with a homogeneous dispersion of silver particulate - prepared using the glycine-nitrate process

    SciTech Connect

    Weil, K. Scott; Hardy, John S.

    2005-01-31

    Recently a new method of ceramic brazing has been developed. Based on a two-phase liquid composed of silver and copper oxide, brazing is conducted directly in air without the need of an inert cover gas or the use of surface reactive fluxes. Because the braze displays excellent wetting characteristics on a number ceramic surfaces, including alumina, various perovskites, zirconia, and ceria, we were interested in investigating whether a metal-reinforced ceramic matrix composite (CMC) could be developed with this material. In the present study, two sets of homogeneously mixed silver/copper oxide/ceria powders were synthesized using a combustion synthesis technique. The powders were compacted and heat treated in air above the liquidus temperature for the chosen Ag-CuO composition. Metallographic analysis indicates that the resulting composite microstructures are extremely uniform with respect to both the size of the metallic reinforcement as well as its spatial distribution within the ceramic matrix. The size, morphology, and spacing of the metal particulate in the densified composite appears to be dependent on the original size and the structure of the starting combustion synthesized powders.

  11. Oxidative mobilization of cerium and uranium and enhanced release of "immobile" high field strength elements from igneous rocks in the presence of the biogenic siderophore desferrioxamine B

    NASA Astrophysics Data System (ADS)

    Kraemer, Dennis; Kopf, Sebastian; Bau, Michael

    2015-09-01

    Polyvalent trace elements such as the high field strength elements (HFSE) are commonly considered rather immobile during low-temperature water-rock interaction. Hence, they have become diagnostic tools that are widely applied in geochemical studies. We present results of batch leaching experiments focused on the mobilization of certain HFSE (Y, Zr, Hf, Th, U and rare earth elements) from mafic, intermediate and felsic igneous rocks in the presence and absence, respectively, of the siderophore desferrioxamine B (DFOB). Our data show that DFOB strongly enhances the mobility of these trace elements during low-temperature water-rock interaction. The presence of DFOB produces two distinct features in the Rare Earths and Yttrium (REY) patterns of leaching solutions, regardless of the mineralogical and chemical composition or the texture of the rock type studied. Bulk rock-normalized REY patterns of leaching solutions with DFOB show (i) a very distinct positive Ce anomaly and (ii) depletion of La and other light REY relative to the middle REY, with a concave downward pattern between La and Sm. These features are not observed in experiments with hydrochloric acid, acetic acid or deionized water. In DFOB-bearing leaching solutions Ce and U are decoupled from and selectively enriched relative to light REY and Th, respectively, due to oxidation to Ce(IV) and U(VI). Oxidation of Ce3+ and U4+ is promoted by the significantly higher stability of the Ce(IV) and U(VI) DFOB complexes as compared to the Ce(III) and U(IV) DFOB complexes. This is similar to the relationship between the Ce(IV)- and Ce(III)-pentacarbonate complexes that cause positive Ce anomalies in alkaline lakes. However, while formation of Ce(IV) carbonate complexes is confined to alkaline environments, Ce(IV) DFOB complexes may produce positive Ce anomalies even in mildly acidic and near-neutral natural waters. Siderophore-promoted dissolution processes also significantly enhance mobility of other 'immobile' HFSE

  12. The effects of cerium doping on the size, morphology, and optical properties of α-hematite nanoparticles for ultraviolet filtration

    SciTech Connect

    Cardillo, Dean; Konstantinov, Konstantin; Devers, Thierry

    2013-11-15

    Highlights: • Possible application of cerium-doped α-hematite as ultraviolet filter. • Nanoparticles obtained through co-precipitation technique using various cerium doping levels followed by annealing. • Comprehensive materials characterisation utilizing XRD, DSC/TGA, STEM, UV–vis spectroscopy. • Increasing cerium content reduces particle sizing and alters morphology. • Solubility of cerium in hematite seen between 5 and 10% doping, 10% cerium doping greatly enhances attenuation in ultraviolet region and increases optical bandgap. - Abstract: Metal oxide nanoparticles have potential use in energy storage, electrode materials, as catalysts and in the emerging field of nanomedicine. Being able to accurately tailor the desirable properties of these nanoceramic materials, such as particle size, morphology and optical bandgap (E{sub g}) is integral in the feasibility of their use. In this study we investigate the altering of both the structure and physical properties through the doping of hematite (α-Fe{sub 2}O{sub 3}) nanocrystals with cerium at a range of concentrations, synthesised using a one-pot co-precipitation method. This extremely simple synthesis followed by thermal treatment results in stable Fe{sub 2−x}Ce{sub x}O{sub y} nanoceramics resulting from the burning of any unreacted precursors and transformation of goethite-cerium doped nanoparticle intermediate. The inclusion of Ce into the crystal lattice of these α-Fe{sub 2}O{sub 3} nanoparticles causes a significantly large reduction in mean crystalline size and alteration in particle morphology with increasing cerium content. Finally we report an increase optical semiconductor bandgap, along with a substantial increase in the ultraviolet attenuation found for a 10% Ce-doping concentration which shows the potential application of cerium-doped hematite nanocrystals to be used as a pigmented ultraviolet filter for cosmetic products.

  13. Cerium and niobium doped SrCoO3-δ as a potential cathode for intermediate temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Huang, Shouguo; Feng, Shuangjiu; Lu, Qiliang; Li, Yide; Wang, Hong; Wang, Chunchang

    2014-04-01

    Sr0.9Ce0.1Co0.9Nb0.1O3-δ (SCCN) has been synthesized using solid state reaction, and investigated as a new cathode material for intermediate temperature solid oxide fuel cells (ITSOFCs). SCCN material exhibits sufficiently high electronic conductivity and excellent chemical compatibility with SDC electrolyte. Highly charged Ce4+ and Nb5+ successfully stabilize the perovskite structure to avoid order-disorder phase transition. The electrical conductivity reaches a high value of 516 S cm-1 at 300 °C in air. The area specific resistances of the SCCN-50 wt.% Ce0.8Sm0.2O1.9 (SDC) cathode are as low as 0.027, 0.049, and 0.094 Ω cm2 at 700, 650, and 600 °C, respectively, with the corresponding peak power densities of 1074, 905, and 589 mW cm-2. A relatively low thermal expansion coefficient of SCCN-SDC is 14.3 × 10-6 K-1 in air. All these results imply that SCCN holds tremendous promise as a cathode material for ITSOFCs.

  14. Electrical conductivity and impedance spectroscopy studies of cerium based aeschynite type semiconducting oxides: CeTiMO6 (M=Nb or Ta)

    NASA Astrophysics Data System (ADS)

    Sumi, S.; Rao, P. Prabhakar; Deepa, M.; Koshy, Peter

    2010-09-01

    Complex ceramic oxides, CeTiMO6 (M=Nb or Ta) having aeschynite type mineral structure were prepared by the conventional ceramic route. Complex impedance analysis in the frequency range 10 Hz-1 MHz over a wide temperature range (30-600 °C) indicates the presence of grain boundary effect along with the bulk contribution and also confirms the presence of non-Debye type of multiple relaxations in the material. The frequency dependent conductivity plots exhibit double power law dependence suggesting three types of conduction mechanisms: low frequency (10 Hz-1 kHz) conductivity owing to long range translational motion of electrons (frequency independent), mid-frequency conductivity (1-10 kHz) due to short-range hopping, and high frequency (10 kHz-1 MHz) conduction due to localized orientation hopping mechanism. The hopping model can explain the nature of the conduction mechanism completely. The electrical conductivity measurements with temperature suggest the negative temperature coefficient of resistance behavior. The activation energy studies allow insight into the nature of the conduction mechanisms.

  15. Effects of Cerium Oxide and Ferrocene Nanoparticles Addition As Fuel-Borne Catalysts on Diesel Engine Particulate Emissions: Environmental and Health Implications.

    PubMed

    Zhang, Zhi-Hui; Balasubramanian, Rajasekhar

    2017-04-06

    This study systematically examined the potential impacts of doping CeO2 and Fe(C5H5)2 nanoparticles as fuel-borne catalysts (FBCs) to ultralow sulfur diesel (ULSD) fuel on the physical, chemical and toxicological characteristics of diesel particulate matter (DPM). The FBCs-doped fuels are effective in promoting soot oxidation and reducing the DPM mass emissions, but lead to a significant increase in the total particle counts due to the formation of self-nucleated metallic nanoparticles. Compared to undoped ULSD, the FBCs-doped fuels result in higher concentrations of particle-phase polycyclic aromatic hydrocarbons (PAHs) and n-alkanes, higher fractions of organic carbon (OC) and water-soluble organic carbon (WSOC) in particles, show slight alterations in soot nanostructure, reduce soot ignition temperature and activation energy. Exposure of the human-type II cell alveolar epithelial cells (A549) to DPM derived from FBCs-doped fuels shows a decrease in cell viability and alterations in the global gene expression with a broad range of biochemical pathways. The overall variations in DPM characteristics are mainly caused by the catalytic combustion process, and are related to the type, properties and contents of FBCs used in diesel fuel as well as the engine operating conditions. Environmental and health implications of the study are highlighted.

  16. A Study of Electrocatalytic and Photocatalytic Activity of Cerium Molybdate Nanocubes Decorated Graphene Oxide for the Sensing and Degradation of Antibiotic Drug Chloramphenicol.

    PubMed

    Karthik, Raj; Vinoth Kumar, Jeyaraj; Chen, Shen-Ming; Karuppiah, Chelladurai; Cheng, Yi-Hui; Muthuraj, Velluchamy

    2017-02-22

    In this present work, "killing two birds with one stone" strategy was performed for the electrochemical trace level detection and photocatalytic degradation of antibiotic drug chloramphenicol (CAP) using Ce(MoO4)2 nanocubes/graphene oxide (CeM/GO) composite for the first time. The CeM/GO composite was synthesized via simple hydrothermal treatment followed by sonication process. The successful formation of CeM/GO composite was confirmed by several analytical and spectroscopic techniques. The CeM/GO composite modified glassy carbon electrode (GCE) showed excellent electrocatalytic activity toward the reduction of CAP in terms of decrease the potential and increase the cathodic peak current in comparison with different modified and unmodified electrodes. The electrocatalytic reduction of CAP based on the CeM/GO modified GCE exhibited high selectivity, wide linear ranges, lower detection limit, and good sensitivity of 0.012-20 and 26-272 μM, 2 nM ,and 1.8085 μA μM(-1) cm(-2), respectively. Besides, when CeM/GO/GCE was used to analyze the CAP in real samples, such as honey and milk, the satisfactory recovery results were obtained. On the other hand, the CeM/GO composite played excellent catalyst toward the photodegradation of CAP. The obtained results from the UV-vis spectroscopy clearly suggested that CeM/GO composite had high photocatalytic activity compared to pristine Ce(MoO4)2 nanocubes. The degradation efficiency of CeM/GO toward CAP is observed about 99% within 50 min under visible irradiation and it shows a good stability by observing the reusability of the catalyst. The enhanced photocatalytic performance was attributed to the increased migration efficiency of photoinduced electrons and holes.

  17. Lung retention of cerium in humans.

    PubMed Central

    Pairon, J C; Roos, F; Iwatsubo, Y; Janson, X; Billon-Galland, M A; Bignon, J; Brochard, P

    1994-01-01

    A retrospective study was conducted to evaluate lung retention of particles containing cerium in subjects with and without previous occupational exposure to mineral dusts. Analytical transmission electron microscopy was performed on 459 samples of bronchoalveolar lavage (BAL) fluid and 75 samples of lung tissue. Study of the distribution of mineralogical species in human samples showed that particles containing cerium were encountered in less than 10% of subjects. The proportion of subjects with particles containing cerium in their biological samples was not different between controls and subjects with previous occupational exposure to fibrous or nonfibrous mineral dusts. This was considered as the background level of lung retention of cerium in the general population. By contrast, determination of the absolute concentration of particles containing cerium in BAL fluid and lung tissue samples showed that 1.2% (from BAL fluid) and 1.5% (from lung tissue) of subjects with previous exposure to mineral particles had high lung retention of particles containing cerium. This study is believed to be the first one in which lung retention of cerium was estimated in the general population. PMID:8130849

  18. Remarkable changes in the photoluminescent properties of Y2Ce2O7:Eu(3+) red phosphors through modification of the cerium oxidation states and oxygen vacancy ordering.

    PubMed

    Raj, Athira K V; Prabhakar Rao, P; Sreena, T S; Sameera, S; James, Vineetha; Renju, U A

    2014-11-21

    A new series of red phosphors based on Eu(3+)-doped yttrium cerate [Y1.9Ce2O7:0.1Eu(3+), Y2Ce1.9O7:0.1Eu(3+) and Y2Ce2-xO7:xEu(3+) (x = 0.05, 0.10, 0.15, 0.20, 0.25 and 0.50)] was prepared via a conventional solid-state method. The influence of the substitution of Eu(3+) at the aliovalent site on the photoluminescent properties was determined by powder X-ray diffraction, FT Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy with energy-dispersive spectroscopy, UV-visible absorption spectroscopy, photoluminescence spectroscopy and lifetime measurements. The substitution of Eu(3+) at the Ce(4+) site induces a structural transition from a defect fluorite to a C-type structure, which increases the oxygen vacancy ordering and the distortion of the Eu(3+) environment, and decreases the formation of Ce(3+) states. In contrast, phosphors with isovalent substitution at the Y(3+) site exhibit the biphasic nature of defect fluorite and a C-type structure, thereby increasing the number of Ce(3+) oxidation states. These modifications resulted in remarkable changes in the photoluminescent properties of Y2Ce1.9O7:0.1Eu(3+) red phosphors, with emission intensities 3.8 times greater than those of the Ce0.9O2:0.1Eu(3+) and Y1.9Ce2O7:0.1Eu(3+). The photoluminescent properties of Y2Ce2-xO7:xEu(3+) were studied at different Eu(3+) concentrations under excitation with blue light. These phosphors emit intense red light due to the (5)D0-(7)F2 transition under excitation at 466 nm and no concentration quenching is observed with up to 50 mol% Eu(3+). They show increased lifetimes in the range 0.62-0.72 ms at Eu(3+) concentrations. The cation ordering linked to the oxygen vacancy ordering led to the uniform distribution of Eu(3+) ions in the lattice, thus allowing higher doping concentrations without quenching and consequently increasing the lifetime of the (5)D0 states. Our results demonstrate that significant improvements in

  19. Optical properties of cerium doped oxyfluoroborate glass.

    PubMed

    Bahadur, A; Dwivedi, Y; Rai, S B

    2013-06-01

    Cerium doped oxyfluoroborate glasses have been prepared and its spectroscopic properties have been discussed. It is found that the absorption edge shifts towards the lower energy side for the higher concentration of cerium dopant. Optical band gap for these glasses have been calculated and it is found that the number of non-bridging oxygen increases with cerium content. The emission spectra of these glasses have been recorded using UV laser radiations (266 and 355 nm) and it is observed that these glasses show bright blue emission. On the basis of excitation and emission spectra we have reported the existence of at least two different emission centers of Ce(3+)ions.

  20. Enhanced chemiluminescence of cerium(IV)-Tween 85 system and the analytical application.

    PubMed

    Li, Shifeng; Qian, Li; Zhu, Yan; Liu, Manman; Gao, Yinping; Ni, Yonghong

    2013-01-01

    The oxidation reaction between cerium(IV) and Tween 85 in sulfuric acid medium produced weak chemiluminescence (CL). In this paper, it was found that citrate could strongly enhance the CL of cerium(IV)-Tween 85-polyphenol system. Based on studies of ultraviolet-visible spectra and CL spectra, the CL enhancement mechanism had been proposed. It was surmised that the light emission was from an excited oxygen molecular pair O2((1)Δg)O2((1)∑g(-)). The maximum emission wavelength was about 478 nm. The effects of 17 amino acids and 29 organic compounds on cerium(IV)-Tween 85-citrate CL were investigated by a flow injection procedure. This study showed the present system had a wide application for the determination of these compounds.

  1. Synthesis and characterization of cerium and yttrium alkoxide complexes supported by ferrocene-based chelating ligands.

    PubMed

    Broderick, Erin M; Thuy-Boun, Peter S; Guo, Neng; Vogel, Carola S; Sutter, Jörg; Miller, Jeffrey T; Meyer, Karsten; Diaconescu, Paula L

    2011-04-04

    Two series of Schiff base metal complexes were investigated, where each series was supported by an ancillary ligand incorporating a ferrocene backbone and different N=X functionalities. One ligand is based on an imine, while the other is based on an iminophosphorane group. Cerium(IV), cerium(III), and yttrium(III) alkoxide complexes supported by the two ligands were synthesized. All metal complexes were characterized by cyclic voltammetry. Additionally, NMR, Mössbauer, X-ray absorption near-edge structure (XANES), and absorption spectroscopies were used. The experimental data indicate that iron remains in the +2 oxidation state and that cerium(IV) does not engage in a redox behavior with the ancillary ligand.

  2. Cerium clustering and radiation damage resistance in aluminophosphate and silicophosphate glasses

    NASA Astrophysics Data System (ADS)

    Rygel, Jennifer Lynn

    Cerium oxide is a well-known additive for increasing resistance to radiation damage in glass by preventing electrons and holes freed by irradiation from becoming trapped at defect sites and inducing optical absorption bands which can severely darken the glass. Phosphate glasses provide a unique opportunity for studying radiation damage resistance due to their high rare-earth solubility, ˜25 mol%. Two series of glasses, nominally AlP3O9-CeP 3O9 and CeP3O9-SiP2O 7, were synthesized to investigate structure-property relationships in a range of compositions near the metaphosphate. The presence of cerium clustering, or sharing of oxygen between cerium cations, was predicted using the chain fragment cluster model, an extension of earlier models for rare-earth phosphate glasses. Using the atom% composition determined by XPS from vacuum fracture surfaces, and cation coordination measured by Ce K-edge EXAFS, 29Si CPMG NMR, and 27Al MAS NMR, it was determined that clustering occurs for glasses containing ≥ 14 mol% Ce2O3 in the aluminophosphate glass series and ≥ 18 mol% Ce2O3 in the silicophosphate glass series. Many measured properties have been observed to correlate with the presence or absence of cerium clustering, cluster size, or other concomitant structural changes, including: visible coloration, density, refractive index, Ce3+ photoluminescence, and Ce3+ paramagnetic resonance. Additionally, radiation damage resistance was identified in the aluminophosphate and silicophosphate glasses which were predicted to have clustered cerium cations through the absence of radiation-induced phosphorus-related paramagnetic defects. This resistance is attributed to a structural implication of clustering. Specifically, cerium cations will be in close proximity to defect precursor sites at the concentrations required for clustering and are thus able to prevent localization of electrons and holes on those sites. Finally, irradiation-induced optical absorption was measured in all

  3. DFT study of the active site of the XoxF-type natural, cerium-dependent methanol dehydrogenase enzyme.

    PubMed

    Bogart, Justin A; Lewis, Andrew J; Schelter, Eric J

    2015-01-19

    Rare-earth metal cations have recently been demonstrated to be essential co-factors for the growth of the methanotrophic bacterium Methylacidiphilum fumariolicum SolV. A crystal structure of the rare-earth-dependent methanol dehydrogenase (MDH) includes a cerium cation in the active site. Herein, the Ce-MDH active site has been analyzed through DFT calculations. The results show the stability of the Ce(III)-pyrroloquinoline quinone (PQQ) semiquinone configuration. Calculations on the active oxidized form of this complex indicate a 0.81 eV stabilization of the PQQ(0) LUMO at cerium versus calcium, supporting the observation that the cerium cation in the active site confers a competitive advantage to Methylacidiphilum fumariolicum SolV. Using reported aqueous electrochemical data, a semi-empirical correlation was established based on cerium(IV/III) redox potentials. The correlation allowed estimation of the cerium oxidation potential of +1.35 V versus saturated calomel electrode (SCE) in the active site. The results are expected to guide the design of functional model complexes and alcohol-oxidation catalysts based on lanthanide complexes of biologically relevant quinones.

  4. Pulmonary toxicity in mice following exposure to cerium chloride.

    PubMed

    Hong, Jie; Yu, Xiaohong; Pan, Xiaoyu; Zhao, Xiaoyang; Sheng, Lei; Sang, Xuezi; Lin, Anan; Zhang, Chi; Zhao, Yue; Gui, Suxin; Sun, Qingqing; Wang, Ling; Hong, Fashui

    2014-06-01

    The widespread application of lanthanoids (Lns) in manufacturing industries has raised occupational and environmental health concerns about the possible increased health risks to humans exposed to Lns in their working and living environments. Numerous studies have shown that exposures to Ln cause pulmonary injury in animals, but very little is known about the molecular mechanisms of the pulmonary inflammation caused by cerium chloride (CeCl3) exposure. In this study, we evaluated the oxidative stress and molecular mechanism underlying with the pulmonary inflammation associated with chronic lung toxicity in mice treated with nasally instilled CeCl3 for 90 consecutive days. Our findings suggest that significant cerium accumulated in the lung, leading the obvious increase of the lung indices, significant increases in inflammatory cells and levels of lactate dehydrogenase, alkaline phosphate, and total protein, overproduction of reactive oxygen species and peroxidation of lipids, reduced antioxidant capacity, and pulmonary inflammation. CeCl3 exposure also activated nuclear factor κB, increased the expression of tumor necrosis factor α, cyclooxygenase-2, heme oxygenase 1, interleukin 2, interleukin 4, interleukin 6, interleukin 8, interleukin 10, interleukin 18, interleukin 1β, and CYP1A1. However, CeCl3 reduced the expression of nuclear factor κB (NF-κB)-inhibiting factor and heat shock protein 70. These findings suggest that the pulmonary inflammation caused by CeCl3 in mice is closely associated with oxidative stress and inflammatory cytokine expression.

  5. Kinetics of thermal synthesis of cerium sulfides

    NASA Astrophysics Data System (ADS)

    Gibbard, Kevin B.; Allahar, Kerry N.; Kolman, David; Butt, Darryl P.

    2008-09-01

    One of the most promising applications for cerium sulfide is as a refractory for molten metal processing, particularly for reactive actinides. Separate processes were used to synthesize cerium monosulfide, cerium sesquisulfide (Ce 2S 3) and cerium hydride (CeH 2). High purity Ce 2S 3 was produced by reacting ceria (CeO 2) and hydrogen sulfide (H 2S) in an induction furnace using a carbon catalyst at temperatures above 2000 °C. CeH 2 was synthesized from cerium metal and hydrogen gas at 100 °C. Ce 2S 3 and CeH 2 were subsequently reacted together in an induction furnace at temperatures above 1700 °C to produce CeS. X-ray diffraction was used to analyze synthesized samples and the kinetics of the CeS synthesis reaction was modeled using a diffusion-limited reaction model. The activation energy for the process was estimated to be 190 kJ/mol.

  6. α-Radioactivity of cerium-142

    USGS Publications Warehouse

    Senftle, F.E.; Stern, T.W.; Alekna, V.P.

    1959-01-01

    JOHNSON AND NIER1 have measured the atomic masses of some of the rare-earth isotopes and have shown that the mass difference cerium-142—(barium-138 + helium-4) is equivalent to 1.68 ± 0.10 MeV. Similar results for the naturally occurring samarium and neodymium isotopes show that the α-active isotope of each element is the one having the largest possible decay energy. Rasmussen and others2 suggest that the two or three neutrons just beyond the closed shell of 82 neutrons have decreased binding energies and hence the α-energy has a maximum about 84 neutrons. Johnson and Nier suggest that the α-decay of cerium-142 may take place with enough energy to be experimentally observable. Porschen and Riezler3 examined a sample of un-enriched cerium ammonium citrate using nuclear track plates sensitive to α-particles. No α-activity was observed after a 30-day exposure of 1.2 mgm. of the cerium salt. In 1957 Riezler and Kauw4 reported an alpha activity for an enriched sample of cerium-142. From their results they calculated a half-life of 5.1 × 1015 years with an uncertainty factor of 2.

  7. EPDM composite membranes modified with cerium doped lead zirconate titanate

    NASA Astrophysics Data System (ADS)

    Zaharescu, T.; Dumitru, A.; Lungulescu, M. E.; Velciu, G.

    2016-01-01

    This study was performed on γ-irradiated ethylene-propylene diene terpolymer (EPDM) loaded with lead zirconate titanate. The inorganic phase has a perovskite structure with general formula Pb(Zr0.65-xCexTi0.35)O3. The three composites with different Ce dopant concentrations revealed the stabilization activity of filler against oxidation proved by chemiluminescence investigation in respect to pristine polymer. The presence of cerium low concentrations in the solid lead zirconate titanate nanoparticles causes significant slowing of oxidation rate during radiation exposure. The improvement in the stabilization feature of filler is correlated with the existence of traps, whose interaction with free radicals assumes medium energy due to their convenient depth.

  8. Cerium migration during PEM fuel cell accelerated stress testing

    SciTech Connect

    Baker, Andrew M.; Mukundan, Rangachary; Borup, Rodney L.; Spernjak, Dusan; Judge, Elizabeth J.; Advani, Suresh G.; Prasad, Ajay K.

    2016-01-01

    Cerium is a radical scavenger which improves polymer electrolyte membrane (PEM) fuel cell durability. During operation, however, cerium rapidly migrates in the PEM and into the catalyst layers (CLs). In this work, membrane electrode assemblies (MEAs) were subjected to accelerated stress tests (ASTs) under different humidity conditions. Cerium migration was characterized in the MEAs after ASTs using X-ray fluorescence. During fully humidified operation, water flux from cell inlet to outlet generated in-plane cerium gradients. Conversely, cerium profiles were flat during low humidity operation, where in-plane water flux was negligible, however, migration from the PEM into the CLs was enhanced. Humidity cycling resulted in both in-plane cerium gradients due to water flux during the hydration component of the cycle, and significant migration into the CLs. Fluoride and cerium emissions into effluent cell waters were measured during ASTs and correlated, which signifies that ionomer degradation products serve as possible counter-ions for cerium emissions. Fluoride emission rates were also correlated to final PEM cerium contents, which indicates that PEM degradation and cerium migration are coupled. Lastly, it is proposed that cerium migrates from the PEM due to humidification conditions and degradation, and is subsequently stabilized in the CLs by carbon catalyst supports.

  9. Cerium migration during PEM fuel cell accelerated stress testing

    DOE PAGES

    Baker, Andrew M.; Mukundan, Rangachary; Borup, Rodney L.; ...

    2016-01-01

    Cerium is a radical scavenger which improves polymer electrolyte membrane (PEM) fuel cell durability. During operation, however, cerium rapidly migrates in the PEM and into the catalyst layers (CLs). In this work, membrane electrode assemblies (MEAs) were subjected to accelerated stress tests (ASTs) under different humidity conditions. Cerium migration was characterized in the MEAs after ASTs using X-ray fluorescence. During fully humidified operation, water flux from cell inlet to outlet generated in-plane cerium gradients. Conversely, cerium profiles were flat during low humidity operation, where in-plane water flux was negligible, however, migration from the PEM into the CLs was enhanced. Humiditymore » cycling resulted in both in-plane cerium gradients due to water flux during the hydration component of the cycle, and significant migration into the CLs. Fluoride and cerium emissions into effluent cell waters were measured during ASTs and correlated, which signifies that ionomer degradation products serve as possible counter-ions for cerium emissions. Fluoride emission rates were also correlated to final PEM cerium contents, which indicates that PEM degradation and cerium migration are coupled. Lastly, it is proposed that cerium migrates from the PEM due to humidification conditions and degradation, and is subsequently stabilized in the CLs by carbon catalyst supports.« less

  10. Divalent fluoride doped cerium fluoride scintillator

    DOEpatents

    Anderson, David F.; Sparrow, Robert W.

    1991-01-01

    The use of divalent fluoride dopants in scintillator materials comprising cerium fluoride is disclosed. The preferred divalent fluoride dopants are calcium fluoride, strontium fluoride, and barium fluoride. The preferred amount of divalent fluoride dopant is less than about two percent by weight of the total scintillator. Cerium fluoride scintillator crystals grown with the addition of a divalent fluoride have exhibited better transmissions and higher light outputs than crystals grown without the addition of such dopants. These scintillators are useful in radiation detection and monitoring applications, and are particularly well suited for high-rate applications such as positron emission tomography (PET).

  11. Near-road modeling and measurement of cerium-containing particles generated by nanoparticle diesel fuel additive use

    EPA Science Inventory

    Cerium oxide nanoparticles (nCe) are used as a fuel-borne catalyst in diesel engines to reduce particulate emissions, yet the environmental and human health impacts of the exhaust particles are not well understood. To bridge the gap between emission measurements and ambient impac...

  12. Cerium(III) and neodymium(III) complexes as scavengers of X/XO-derived superoxide radical.

    PubMed

    Kostova, Irena; Traykova, Maria

    2006-09-01

    The cerium (III) and neodymium (III) complexes with 3,3'-benzylidenebis[4-hydroxycoumarin] were synthesized and characterized by different analytical and spectral methods. The synthesis of these complexes is taken into consideration with cytotoxic screening and study of their antioxidant effect. Their cytotoxicity toward cancerous cell cultures correlated with the weakness of the coordinative bond between the cation and organic ligand and with the capability to scavenge superoxide radicals as well. On the basis of the data reported by us earlier and our new results, it was proposed that cerium (III) complex with 3,3'-benzylidenebis[4-hydroxycoumarin] might induce intracellular acidification along with control over the extracellular oxidative stress.

  13. Near-road modeling and measurement of cerium-containing particles generated by nanoparticle diesel fuel additive use.

    PubMed

    Gantt, Brett; Hoque, Shamia; Willis, Robert D; Fahey, Kathleen M; Delgado-Saborit, Juana Mari; Harrison, Roy M; Erdakos, Garnet B; Bhave, Prakash V; Zhang, K Max; Kovalcik, Kasey; Pye, Havala O T

    2014-09-16

    Cerium oxide nanoparticles (nCe) are used as a fuel-borne catalyst in diesel engines to reduce particulate emissions, yet the environmental and human health impacts of the exhaust particles are not well understood. To bridge the gap between emission measurements and ambient impacts, size-resolved measurements of particle composition and mass concentration have been performed in Newcastle-upon-Tyne, United Kingdom, where buses have used an nCe additive since 2005. These observations show that the noncrustal cerium fraction thought to be associated with the use of nCe has a mass concentration ∼ 0.3 ng m(-3) with a size distribution peaking at 100-320 nm in aerodynamic diameter. Simulations with a near-roadway multicomponent sectional aerosol dynamic model predict that the use of nCe additives increases the number concentration of nuclei mode particles (<50 nm in diameter) while decreasing the total mass concentration. The near-road model predicts a downwind mass size distribution of cerium-containing particles peaking at 150 nm in aerodynamic diameter, a value similar to that measured for noncrustal cerium in Newcastle. This work shows that both the emission and atmospheric transformation of cerium-containing particles needs to be taken into account by regional modelers, exposure scientists, and policymakers when determining potential environmental and human health impacts.

  14. Assessment of the abatement of acelsulfame K using cerium doped ZnO as photocatalyst.

    PubMed

    Calza, P; Gionco, C; Giletta, M; Kalaboka, M; Sakkas, V A; Albanis, T; Paganini, M C

    2017-02-05

    In the present study, we investigated the possibility to abate Acesulfame K, a persistent emerging contaminant, in aqueous media using zinc oxide based materials. For this purpose, bare and Ce-doped zinc oxide was prepared via an easy and cheap hydrothermal process using different cerium salts as precursors. Their photocatalytic performance was evaluated in different media, namely ultrapure and river water under both UV-vis and visible light. Commercial TiO2 P25 was also employed and used as a reference photocatalyst for comparison purposes. The obtained results pointed out that cerium doped zinc oxide composites exhibit higher performance than TiO2 P25, especially under visible light and in the presence of organic matter, when the activity of the latter is greatly depressed. In particular, ZnO doped with cerium (1%) was the most effective material, and could be a promising alternative to TiO2 P25, especially in the treatment of natural waters.

  15. Synthesis of cerium rich intermetallics using molten metal eutectics

    NASA Astrophysics Data System (ADS)

    Tucker, Patricia Christine

    Metal eutectic fluxes are useful for exploratory synthesis of new intermetallic phases. In this work the use of cerium/transition metal eutectics such as: Ce/Co, Ce/Ni, and Ce/Fe have yielded many new synthetically and magnetically complex phases. Structural units that were previously observed in phases grown in La/Ni eutectic reactions have also been observed in new structures and analogs grown from cerium/transition metal eutectics. These structural units include a main group element coordinated by 9 rare-earth atoms (such as the Al Ce9 clusters seen in Ce31.0(2)Fe11.8(5)Al6.5(6) B13C4), trigonal planar FeC3 units (also seen in Ce31.0(2)Fe11.8(5)Al6.5(6)B 13C4), iron clusters capped by light elements (Fe4C 6 frustrated tetrahedral in Ce21Fe8M7C 14, and larger Fe clusters in Ce33Fe14B25 C34). Variants of these building blocks were observed in Ce10Co2B7C16 with square Co units and chains of B and C connected to them, Fe2C8 units observed in Ce7Fe2C9, and FeC4 observed in Ce4FeGa0.85Al0.15C4 and Ce4FeAlC4. Two new phases were grown from Ce/Fe eutectic, Ce33Fe 14B25C34 and Ce33Fe13B 18C34 which exhibits very similar structures, but significantly different magnetic behavior. Structurally these two phases are similar. Both crystallize in the Im-3m space group, but differ by the centering of the Fe clusters. Ce33Fe14B25C34 contains Fe clusters centered by B atoms and Al doped on the Fe2 site. In Ce33Fe13B18C34, the Fe cluster is a perfect cuboctahedron. Ce33Fe14B25 C34 exhibits mixed valent behavior of cerium at 75K and no magnetic moment on iron, where-as Ce33Fe13B18C 34 exhibits tetravalent cerium and its iron clusters undergo a ferromagnetic transition at 180K. Another borocarbide, Ce10Co2B7C 16 was synthesized from Ce/Co eutectic flux. This structure features squares of Co surrounded by chains of C and B and a sea of cerium atoms. Temperature dependent magnetic susceptibility measurements at 1 Tesla were fit to a modified Curie-Weiss law and a moment per Ce was

  16. Template-free synthesis of uniform single-crystal hollow cerium dioxide nanocubes and their catalytic activity

    NASA Astrophysics Data System (ADS)

    Han, Xiguang; Li, Liang; Wang, Chao

    2013-07-01

    Monodisperse single-crystal hollow cerium dioxide nanocubes with exposed (001) facets have been synthesized with the assistance of ammonium chloride (NH4Cl) and polyvinylpyrrolidone (PVP) in a water and ethanol system. A series of experiments indicate that ammonium ion plays an important role in the formation of the hollow structure and PVP plays a key role in the formation of a cubic shape. The hollow cerium dioxide nanocubes exhibit excellent CO catalytic oxidation activity.Monodisperse single-crystal hollow cerium dioxide nanocubes with exposed (001) facets have been synthesized with the assistance of ammonium chloride (NH4Cl) and polyvinylpyrrolidone (PVP) in a water and ethanol system. A series of experiments indicate that ammonium ion plays an important role in the formation of the hollow structure and PVP plays a key role in the formation of a cubic shape. The hollow cerium dioxide nanocubes exhibit excellent CO catalytic oxidation activity. Electronic supplementary information (ESI) available: the preparation and characterization of CeO2 and measurement details for the CO oxidation reaction. See DOI: 10.1039/c3nr01948a

  17. Study of cerium phase transitions in shock wave experiments

    SciTech Connect

    Zhernokletov, M. V. Kovalev, A. E.; Komissarov, V. V.; Novikov, M. G.; Zocher, M. A. Cherne, F. J.

    2011-02-15

    Cerium has a complex phase diagram that is explained by the presence of structural phase transitions. Experiments to measure the sound velocities in cerium by two methods were carried out to determine the onset of cerium melting on the Hugoniot. In the pressure range 4-37 GPa, the sound velocity in cerium samples was measured by the counter release method using manganin-based piezoresistive gauges. In the pressure range 35-140 GPa, the sound velocity in cerium was measured by the overtaking release method using carbogal and tetrachloromethane indicator liquids. The samples were loaded with plane shock wave generators using powerful explosive charges. The onset of cerium melting on the Hugoniot at a pressure of about 13 GPa has been ascertained from the measured elastic longitudinal and bulk sound velocities.

  18. Thermochemical Modeling of the Uranium-Cerium-Oxygen System

    SciTech Connect

    Voit, Stewart L; Besmann, Theodore M

    2010-10-01

    The objective of the Fuel Cycle R&D Program, Advanced Fuels campaign is to provide the research and development necessary to develop low loss, high quality nuclear fuels for ultra-high burnup reactor operation. Primary work in this area will be focused on the ceramic and metallic fuel systems. The goal of the current work is to enhance the understanding of ceramic nuclear fuel thermochemistry to support fuel research and development efforts. The thermochemical behavior of oxide nuclear fuel under irradiation is dependent on the oxygen to metal ratio (O:M). In fluorite-structured fuel, the actinide metal cation is bonded with {approx}2 oxygen atoms on a crystal lattice and as the metal atoms fission, fission fragments and free oxygen are created. The resulting fission fragments will contain some oxide forming elements, however these are insufficient to bind to all the liberated oxygen and therefore, there is an average increase in O:M with fuel burnup. Some of the fission products also form species that will migrate to and react with the cladding surface in a phenomenon known as Fuel Clad Chemical Interaction (FCCI). Cladding corrosion is life-limiting so it is desirable to understand influencing factors, such as oxide thermochemistry, which can be used to guide the design and fabrication of higher burn up fuel. A phased oxide fuel thermochemical model development effort is underway within the Advanced Fuels Campaign. First models of binary oxide systems are developed. For nuclear fuel system this means U-O and transuranic systems such as Pu-O, Np-O and Am-O. Next, the binary systems will be combined to form pseudobinary systems such as U-Pu-O, etc. The model development effort requires the use of data to allow optimization based on known thermochemical parameters as a function of composition and temperature. Available data is mined from the literature and supplemented by experimental work as needed. Due to the difficulty of performing fuel fabrication development

  19. Gamma-alpha Isostructural Transition in Cerium

    SciTech Connect

    Lanata, Nicola; Yao, Yong-Xin; Wang, Cai-Zhuang; Ho, Kai-Ming; Schmalian, Jorg; Haule, Kristjan; Kotliar, Gabriel

    2013-11-05

    We present zero-temperature first-principles calculations of elemental cerium and we compute its pressure-volume phase diagram within a theoretical framework able to describe simultaneously both the α and the γ phases. A surprising result revealed by our study is the presence of a clear signature of the transition at zero temperature and that this signature can be observed if and only if the spin-orbit coupling is taken into account. Our calculations indicate that the transition line in the pressure-temperature phase diagram of this material has a low-T critical point at negative pressures, placed very close to zero temperature. This suggests that cerium is very close to being “quantum critical,” in agreement with recent experiments.

  20. Phonons of the anomalous element cerium

    PubMed Central

    Krisch, Michael; Farber, D. L.; Xu, R.; Antonangeli, Daniele; Aracne, C. M.; Beraud, Alexandre; Chiang, Tai-Chang; Zarestky, J.; Kim, Duck Young; Isaev, Eyvaz I.; Ahuja, Rajeev; Johansson, Börje

    2011-01-01

    Many physical and chemical properties of the light rare-earths and actinides are governed by the active role of f electrons, and despite intensive efforts the details of the mechanisms of phase stability and transformation are not fully understood. A prominent example which has attracted a lot of interest, both experimentally and theoretically over the years is the isostructural γ - α transition in cerium. We have determined by inelastic X-ray scattering, the complete phonon dispersion scheme of elemental cerium across the γ → α transition, and compared it with theoretical results using ab initio lattice dynamics. Several phonon branches show strong changes in the dispersion shape, indicating large modifications in the interactions between phonons and conduction electrons. This is reflected as well by the lattice Grüneisen parameters, particularly around the X point. We derive a vibrational entropy change , illustrating the importance of the lattice contribution to the transition. Additionally, we compare first principles calculations with the experiments to shed light on the mechanism underlying the isostructural volume collapse in cerium under pressure. PMID:21597000

  1. Atomic Transition Probabilities for Neutral Cerium

    NASA Astrophysics Data System (ADS)

    Lawler, J. E.; den Hartog, E. A.; Wood, M. P.; Nitz, D. E.; Chisholm, J.; Sobeck, J.

    2009-10-01

    The spectra of neutral cerium (Ce I) and singly ionized cerium (Ce II) are more complex than spectra of other rare earth species. The resulting high density of lines in the visible makes Ce ideal for use in metal halide (MH) High Intensity Discharge (HID) lamps. Inclusion of cerium-iodide in a lamp dose can improve both the Color Rendering Index and luminous efficacy of a MH-HID lamp. Basic spectroscopic data including absolute atomic transition probabilities for Ce I and Ce II are needed for diagnosing and modeling these MH-HID lamps. Recent work on Ce II [1] is now being augmented with similar work on Ce I. Radiative lifetimes from laser induced fluorescence measurements [2] on neutral Ce are being combined with emission branching fractions from spectra recorded using a Fourier transform spectrometer. A total of 14 high resolution spectra are being analyzed to determine branching fractions for 2000 to 3000 lines from 153 upper levels in neutral Ce. Representative data samples and progress to date will be presented. [4pt] [1] J. E. Lawler, C. Sneden, J. J. Cowan, I. I. Ivans, and E. A. Den Hartog, Astrophys. J. Suppl. Ser. 182, 51-79 (2009). [0pt] [2] E. A. Den Hartog, K. P. Buettner, and J. E. Lawler, J. Phys. B: Atomic, Molecular & Optical Physics 42, 085006 (7pp) (2009).

  2. Coupled redox transformations of catechol and cerium at the surface of a cerium(III) phosphate mineral

    NASA Astrophysics Data System (ADS)

    Cervini-Silva, Javiera; Gilbert, Benjamin; Fakra, Sirine; Friedlich, Stephan; Banfield, Jillian

    2008-05-01

    Highly insoluble Ce-bearing phosphate minerals form by weathering of apatite [Ca5(PO4)3.(OH,F,Cl)], and are important phosphorous repositories in soils. Although these phases can be dissolved via biologically-mediated pathways, the dissolution mechanisms are poorly understood. In this paper we report spectroscopic evidence to support coupling of redox transformations of organic carbon and cerium during the reaction of rhabdophane (CePO4·H2O) and catechol, a ubiquitous biogenic compound, at pH 5. Results show that the oxic-anoxic conditions influence the mineral dissolution behavior. Under anoxic conditions, the release of P and Ce occurs stoichiometrically. In contrast, under oxic conditions, the mineral dissolution behavior is incongruent, with dissolving Ce3+ ions oxidizing to CeO2. Reaction product analysis shows the formation of CO2, polymeric C, and oxalate and malate. The presence of more complex forms of organic carbon was also confirmed. Near edge X-ray absorption fine structure spectroscopy measurements at Ce-M4,5 and C-K absorption edges on reacted CePO4·H2O samples in the absence or presence of catechol and dissolved oxygen confirm that (1) the mineral surface converts to the oxide during this reaction, while full oxidation is limited to the near-surface region only; (2) the Ce valence remains unchanged when the reaction between CePO4·H2O and O2 but in the absence of catechol. Carbon K-edge spectra acquired from rhabdophane reacted with catechol under oxic conditions show spectral features before and after reaction that are considerably different from catechol, indicating the formation of more complex organic molecules. Decreases in intensity of characteristic catechol peaks are accompanied by the appearance of new π∗ resonances due to carbon in carboxyl (ca. 288.5 eV) and carbonyl (ca. 289.3 eV) groups, and the development of broad structure in the σ∗ region characteristic of aliphatic carbon. Evolution of the C K-edge spectra is consistent

  3. RECOVERY OF Pu FROM CERIUM TRIFLUORIDE BY FLUORINATION

    DOEpatents

    Brown, H.S.; Bohlmann, E.G.

    1959-02-10

    An improved process is prcsented for selectively recovering plutonium from a solution containing fission products comprising precipitating cerium trifluoride in the solution for effccting carrier precipitation of plutonium. The resulting carrier precipitate is dried and subjected to fluorination at about 600 C. The plutonium forms a volatile fiuoridc and is so separated from the nonvolatile cerium fluoride.

  4. 40 CFR 721.8657 - Cerium, hydroxy oleate propionate complexes.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Cerium, hydroxy oleate propionate... Specific Chemical Substances § 721.8657 Cerium, hydroxy oleate propionate complexes. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as...

  5. 40 CFR 721.8657 - Cerium, hydroxy oleate propionate complexes.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Cerium, hydroxy oleate propionate... Specific Chemical Substances § 721.8657 Cerium, hydroxy oleate propionate complexes. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as...

  6. 40 CFR 721.8657 - Cerium, hydroxy oleate propionate complexes.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Cerium, hydroxy oleate propionate... Specific Chemical Substances § 721.8657 Cerium, hydroxy oleate propionate complexes. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as...

  7. 40 CFR 721.8657 - Cerium, hydroxy oleate propionate complexes.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Cerium, hydroxy oleate propionate... Specific Chemical Substances § 721.8657 Cerium, hydroxy oleate propionate complexes. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as...

  8. 40 CFR 721.8657 - Cerium, hydroxy oleate propionate complexes.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Cerium, hydroxy oleate propionate... Specific Chemical Substances § 721.8657 Cerium, hydroxy oleate propionate complexes. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as...

  9. Local Structure of Cerium in Aluminophosphate and Silicophosphate Glasses

    SciTech Connect

    J Rygel; Y Chen; C Pantano; T Shibata; J Du; L Kokou; R Woodman; J Belcher

    2011-12-31

    The local structure of cerium in two systematic compositional series of glasses, nominally CeP{sub 3}O{sub 9}-AlP{sub 3}O{sub 9} and CeP{sub 3}O{sub 9}-SiP{sub 2}O{sub 7}, was interrogated using X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) spectroscopy. XPS revealed that, for glasses melted in air, {>=}95% of cerium ions are Ce{sup 3+}. This was independently confirmed using X-ray absorption near edge spectroscopy (XANES). Ce K-edge extended X-ray absorption fine structure (EXAFS) has been used to determine the local structure of Ce{sup 3+}. Near the metaphosphate composition, cerium was found to have an average cerium coordination number of {approx}7.0 and an average cerium-oxygen bond length of 2.41 {angstrom}. The average cerium coordination number and average cerium-oxygen bond distance were found to increase with decreasing cerium concentration in both compositional series. Rare-earth clustering is suggested based on numerical calculations for glasses containing {>=}14 and {>=}15 mol% Ce{sub 2}O{sub 3} for the aluminophosphate and silicophosphate series, respectively.

  10. Local Structure of Cerium in Aluminophosphate and Silicophosphate Glasses

    SciTech Connect

    Rygel, Jennifer L.; Chen, Yongsheng; Pantano, Carlo G.; Shibata, Tomohiro; Du, Jincheng; Kokou, Leopold; Woodman, Robert; Belcher, James

    2011-09-20

    The local structure of cerium in two systematic compositional series of glasses, nominally CeP{sub 3}O{sub 9}-AlP{sub 3}O{sub 9} and CeP{sub 3}O{sub 9}-SiP{sub 2}O{sub 7}, was interrogated using X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) spectroscopy. XPS revealed that, for glasses melted in air, {>=}95% of cerium ions are Ce{sup 3+}. This was independently confirmed using X-ray absorption near edge spectroscopy (XANES). Ce K-edge extended X-ray absorption fine structure (EXAFS) has been used to determine the local structure of Ce{sup 3+}. Near the metaphosphate composition, cerium was found to have an average cerium coordination number of {approx}7.0 and an average cerium-oxygen bond length of 2.41 {angstrom}. The average cerium coordination number and average cerium-oxygen bond distance were found to increase with decreasing cerium concentration in both compositional series. Rare-earth clustering is suggested based on numerical calculations for glasses containing {>=}14 and {>=}15 mol% Ce{sub 2}O{sub 3} for the aluminophosphate and silicophosphate series, respectively.

  11. Cerium migration during PEM fuel cell assembly and operation

    SciTech Connect

    Baker, Andrew M.; Torraco, Dennis; Judge, Elizabeth J.; Spernjak, Dusan; Mukundan, Rangachary; Borup, Rod L.; Advani, Suresh G.; Prasad, Ajay K.

    2015-09-14

    Cerium migration between PEM fuel cell components is influenced by potential-driven mobility, ionic diffusion, and gradients in water content. These factors were investigated in ex situ experiments and in operating fuel cells. Potential-induced migration was measured ex situ in hydrated window cells. Cerium-containing MEAs were also fabricated and tested under ASTs. MEA disassembly and subsequent XRF analysis were used to observe rapid cerium migration during cell assembly and operation. During MEA hot pressing, humidification, and low RH operation at OCV, ionic diffusion causes uniform migration from the membrane into the catalyst layers. During high RH operation at OCV, in-plane cerium gradients arise due to variations in water content. These gradients may diminish the scavenging efficacy of cerium by reducing its proximity to generated radicals.

  12. Cerium Biomagnification in a Terrestrial Food Chain: Influence of Particle Size and Growth Stage.

    PubMed

    Majumdar, Sanghamitra; Trujillo-Reyes, Jesica; Hernandez-Viezcas, Jose A; White, Jason C; Peralta-Videa, Jose R; Gardea-Torresdey, Jorge L

    2016-07-05

    Mass-flow modeling of engineered nanomaterials (ENMs) indicates that a major fraction of released particles partition into soils and sediments. This has aggravated the risk of contaminating agricultural fields, potentially threatening associated food webs. To assess possible ENM trophic transfer, cerium accumulation from cerium oxide nanoparticles (nano-CeO2) and their bulk equivalent (bulk-CeO2) was investigated in producers and consumers from a terrestrial food chain. Kidney bean plants (Phaseolus vulgaris var. red hawk) grown in soil contaminated with 1000-2000 mg/kg nano-CeO2 or 1000 mg/kg bulk-CeO2 were presented to Mexican bean beetles (Epilachna varivestis), which were then consumed by spined soldier bugs (Podisus maculiventris). Cerium accumulation in plant and insects was independent of particle size. After 36 days of exposure to 1000 mg/kg nano- and bulk-CeO2, roots accumulated 26 and 19 μg/g Ce, respectively, and translocated 1.02 and 1.3 μg/g Ce, respectively, to shoots. The beetle larvae feeding on nano-CeO2 exposed leaves accumulated low levels of Ce since ∼98% of Ce was excreted in contrast to bulk-CeO2. However, in nano-CeO2 exposed adults, Ce in tissues was higher than Ce excreted. Additionally, Ce content in tissues was biomagnified by a factor of 5.3 from the plants to adult beetles and further to bugs.

  13. Predicting the effects of nanoscale cerium additives in diesel fuel on regional-scale air quality.

    PubMed

    Erdakos, Garnet B; Bhave, Prakash V; Pouliot, George A; Simon, Heather; Mathur, Rohit

    2014-11-04

    Diesel vehicles are a major source of air pollutant emissions. Fuel additives containing nanoparticulate cerium (nCe) are currently being used in some diesel vehicles to improve fuel efficiency. These fuel additives also reduce fine particulate matter (PM2.5) emissions and alter the emissions of carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbon (HC) species, including several hazardous air pollutants (HAPs). To predict their net effect on regional air quality, we review the emissions literature and develop a multipollutant inventory for a hypothetical scenario in which nCe additives are used in all on-road and nonroad diesel vehicles. We apply the Community Multiscale Air Quality (CMAQ) model to a domain covering the eastern U.S. for a summer and a winter period. Model calculations suggest modest decreases of average PM2.5 concentrations and relatively larger decreases in particulate elemental carbon. The nCe additives also have an effect on 8 h maximum ozone in summer. Variable effects on HAPs are predicted. The total U.S. emissions of fine-particulate cerium are estimated to increase 25-fold and result in elevated levels of airborne cerium (up to 22 ng/m3), which might adversely impact human health and the environment.

  14. Application of Cerium (IV) as an Oxidimetric Agent for the Determination of Ethionamide in Pharmaceutical Formulations

    PubMed Central

    2016-01-01

    Two simple methods are described for the determination of ethionamide (ETM) in bulk drug and tablets using cerium (IV) sulphate as the oxidimetric agent. In both methods, the sample solution is treated with a measured excess of cerium (IV) solution in H2SO4 medium, and after a fixed standing time, the residual oxidant is determined either by back titration with standard iron (II) solution to a ferroin end point in titrimetry or by reacting with o-dianisidine followed by measurement of the absorbance of the orange-red coloured product at 470 nm in spectrophotometry. In titrimetry, the reaction proceeded with a stoichiometry of 1 : 2 (ETM : Ce (IV)) and the amount of cerium (IV) consumed by ETM was related to the latter's amount, and the method was applicable over 1.0–8.0 mg of drug. In spectrophotometry, Beer's law was obeyed over the concentration range of 0.5–5.0 μg/mL ETM with a molar absorptivity value of 2.66 × 104 L/(mol·cm). The limits of detection (LOD) and quantification (LOQ) calculated according to ICH guidelines were 0.013 and 0.043 μg/mL, respectively. The proposed titrimetric and spectrophotometric methods were found to yield reliable results when applied to bulk drug and tablets analysis, and hence they can be applied in quality control laboratories. PMID:27818836

  15. Cerium Regulates Expression of Alternative Methanol Dehydrogenases in Methylosinus trichosporium OB3b

    PubMed Central

    Farhan Ul Haque, Muhammad; Kalidass, Bhagyalakshmi; Bandow, Nathan; Turpin, Erick A.; DiSpirito, Alan A.

    2015-01-01

    Methanotrophs have multiple methane monooxygenases that are well known to be regulated by copper, i.e., a “copper switch.” At low copper/biomass ratios the soluble methane monooxygenase (sMMO) is expressed while expression and activity of the particulate methane monooxygenase (pMMO) increases with increasing availability of copper. In many methanotrophs there are also multiple methanol dehydrogenases (MeDHs), one based on Mxa and another based on Xox. Mxa-MeDH is known to have calcium in its active site, while Xox-MeDHs have been shown to have rare earth elements in their active site. We show here that the expression levels of Mxa-MeDH and Xox-MeDH in Methylosinus trichosporium OB3b significantly decreased and increased, respectively, when grown in the presence of cerium but the absence of copper compared to the absence of both metals. Expression of sMMO and pMMO was not affected. In the presence of copper, the effect of cerium on gene expression was less significant, i.e., expression of Mxa-MeDH in the presence of copper and cerium was slightly lower than in the presence of copper alone, but Xox-MeDH was again found to increase significantly. As expected, the addition of copper caused sMMO and pMMO expression levels to significantly decrease and increase, respectively, but the simultaneous addition of cerium had no discernible effect on MMO expression. As a result, it appears Mxa-MeDH can be uncoupled from methane oxidation by sMMO in M. trichosporium OB3b but not from pMMO. PMID:26296730

  16. Cerium regulates expression of alternative methanol dehydrogenases in Methylosinus trichosporium OB3b.

    PubMed

    Farhan Ul Haque, Muhammad; Kalidass, Bhagyalakshmi; Bandow, Nathan; Turpin, Erick A; DiSpirito, Alan A; Semrau, Jeremy D

    2015-11-01

    Methanotrophs have multiple methane monooxygenases that are well known to be regulated by copper, i.e., a "copper switch." At low copper/biomass ratios the soluble methane monooxygenase (sMMO) is expressed while expression and activity of the particulate methane monooxygenase (pMMO) increases with increasing availability of copper. In many methanotrophs there are also multiple methanol dehydrogenases (MeDHs), one based on Mxa and another based on Xox. Mxa-MeDH is known to have calcium in its active site, while Xox-MeDHs have been shown to have rare earth elements in their active site. We show here that the expression levels of Mxa-MeDH and Xox-MeDH in Methylosinus trichosporium OB3b significantly decreased and increased, respectively, when grown in the presence of cerium but the absence of copper compared to the absence of both metals. Expression of sMMO and pMMO was not affected. In the presence of copper, the effect of cerium on gene expression was less significant, i.e., expression of Mxa-MeDH in the presence of copper and cerium was slightly lower than in the presence of copper alone, but Xox-MeDH was again found to increase significantly. As expected, the addition of copper caused sMMO and pMMO expression levels to significantly decrease and increase, respectively, but the simultaneous addition of cerium had no discernible effect on MMO expression. As a result, it appears Mxa-MeDH can be uncoupled from methane oxidation by sMMO in M. trichosporium OB3b but not from pMMO.

  17. Influence of Collector Surface Composition and Water Chemistry on the Deposition of Cerium Dioxide Nanoparticles: QCM-D and Column Experiment Approaches

    EPA Science Inventory

    The deposition behavior of cerium dioxide (CeO2) nanoparticles (NPs) in dilute NaCl solutions was investigated as a function of collector surface composition, pH, ionic strength, and organic matter (OM). Sensors coated separately with silica, iron oxide, and alumina were applied ...

  18. Atomic Transition Probabilities for Neutral Cerium

    NASA Astrophysics Data System (ADS)

    Chisholm, John; Nitz, D.; Sobeck, J.; Den Hartog, E. A.; Wood, M. P.; Lawler, J. E.

    2010-01-01

    Among the rare earth species, the spectra of neutral cerium (Ce I) and singly ionized cerium (Ce II) are some of the most complex. Like other rare earth species, Ce has many lines in the visible which are suitable for elemental abundance studies. Recent work on Ce II transition probabilities [1] is now being augmented with similar work on Ce I for future studies using such lines from astrophysical sources. Radiative lifetimes from laser induced fluorescence measurements [2] on neutral Ce are being combined with emission branching fractions from spectra recorded using a Fourier transform spectrometer. A total of 14 high resolution spectra are being analyzed to determine branching fractions for 2500 to 3000 lines from 153 upper levels in neutral Ce. Representative data samples and progress to date will be presented. This work was supported by the National Science Foundation's REU program and the Department of Defense's ASSURE program through NSF Award AST-0453442 and NSF Grant CTS0613277. [1] J. E. Lawler, C. Sneden, J. J. Cowan, I. I. Ivans, and E. A. Den Hartog, Astrophys. J. Suppl. Ser. 182, 51-79 (2009). [2] E. A. Den Hartog, K. P. Buettner, and J. E. Lawler, J. Phys. B: Atomic, Molecular & Optical Physics 42, 085006 (7pp) (2009).

  19. Blue/pink/purple electroluminescence from metal-oxide-semiconductor devices fabricated by spin-coating of [tantalum:(gadolinium/praseodymium)] and (praseodymium:cerium) organic compounds on silicon

    NASA Astrophysics Data System (ADS)

    Ohzone, Takashi; Matsuda, Toshihiro; Fukuoka, Ryouhei; Hattori, Fumihiro; Iwata, Hideyuki

    2016-08-01

    Blue/pink/purple electroluminescence (EL) from metal-oxide-semiconductor (MOS) devices with an indium tin oxide (ITO)/[Gd/(Ta + Gd/Pr)/(Pr + Ce)-Si-O] insulator layer/n+-Si substrate surface is reported. The insulator layers were fabricated from organic liquid sources of Gd or (Ta + Gd/Pr)/(Pr + Ce) mixtures, which were spin-coated on the n+-Si substrate and annealed at 950 °C for 30 min in air. The EL emission could be observed by the naked eye in the dark in the Fowler-Nordheim (FN) tunnel current regions. Peak wavelengths in the measured EL spectra were independent of the positive current. The EL intensity ratio of ultraviolet (UV) to the visible range varied with the composition ratio of the (Ta + Gd) liquids, and an optimum Ta to Gd ratio existed for the strongest blue emission, which could be attributed to the Ta-related oxide/silicate. The pink EL of the device fabricated with the (\\text{Ta}:\\text{Pr} = 6:4) mixture ratio can be explained by EL emission peaks related to the Pr3+ ions. The purple EL observed from the (\\text{Pr}:\\text{Ce} = 6:4) device corresponds to the strong and broad emission profile near the 357 nm peak, which cannot be assigned to Ce3+ ions. The results suggest that the EL can be attributed to the double-layer oxides with different compositions in the MOS devices. The upper layer consists of various Ta-, Gd-, Pr-, and Ce-related oxides and their silicates, while the lower SiO x -rich layer contributes to the FN current due to the high electric field, and thus the various EL colors.

  20. Cerium migration during PEM fuel cell assembly and operation

    DOE PAGES

    Baker, Andrew M.; Torraco, Dennis; Judge, Elizabeth J.; ...

    2015-09-14

    Cerium migration between PEM fuel cell components is influenced by potential-driven mobility, ionic diffusion, and gradients in water content. These factors were investigated in ex situ experiments and in operating fuel cells. Potential-induced migration was measured ex situ in hydrated window cells. Cerium-containing MEAs were also fabricated and tested under ASTs. MEA disassembly and subsequent XRF analysis were used to observe rapid cerium migration during cell assembly and operation. During MEA hot pressing, humidification, and low RH operation at OCV, ionic diffusion causes uniform migration from the membrane into the catalyst layers. During high RH operation at OCV, in-plane ceriummore » gradients arise due to variations in water content. These gradients may diminish the scavenging efficacy of cerium by reducing its proximity to generated radicals.« less

  1. Nickel aluminides and nickel-iron aluminides for use in oxidizing environments

    DOEpatents

    Liu, Chain T.

    1988-03-15

    Nickel aluminides and nickel-iron aluminides treated with hafnium or zirconium, boron and cerium to which have been added chromium to significantly improve high temperature ductility, creep resistance and oxidation properties in oxidizing environments.

  2. Predicting Cerium + H2O Cluster Formation with Simulated and Experimental Spectroscopy

    NASA Astrophysics Data System (ADS)

    Topolski, Josey E.; Kafader, Jared O.; Ray, Manisha; Chick Jarrold, Caroline

    2016-06-01

    Ceria (CeO2) has been established as a good support in heterogeneous catalysts for the water gas shift reaction. This study looks into cerium's reactivity with water, a water gas shift reagent, and aims to build an understanding of the three reactions which can occur: direct oxidation, -OH abstraction, and H2O addition. Through the use of anion photoelectron spectroscopy and density functional theory calculations we have been able to determine that the reactivity is dependent on (1) the oxidation states of the metal centers, (2) the availability of 5d orbitals to form metal oxide bonds, and (3) the presence of electrons in the 6s* orbital. The results of this study can be used to inform design of catalytic materials for the water gas shift reaction.

  3. Panthenol-stabilized cerium dioxide nanoparticles for cosmeceutic formulations against ROS-induced and UV-induced damage.

    PubMed

    Zholobak, N M; Shcherbakov, A B; Bogorad-Kobelska, A S; Ivanova, O S; Baranchikov, A Ye; Spivak, N Ya; Ivanov, V K

    2014-01-05

    A method of panthenol-stabilized cerium dioxide nanoparticles synthesis was developed and their effect on the survival rate of human epidermoid cancer cells HEp-2 and diploid epithelial swine testicular cell line (ST-cells) under oxidative stress conditions induced by hydrogen peroxide introduction and UV irradiation was studied. The results obtained indicate that the use of panthenol as a stabilizer supposedly provides a substantial increase in the efficiency of protection. The degree of protection is determined by panthenol-to-ceria molar ratio. The combination of panthenol and nano-ceria protects biological objects under study from reactive oxygen species (ROS) and UV-irradiation more effectively than individual panthenol or ceria. The protective action of panthenol-stabilized cerium dioxide nanoparticles depends strongly on their composition and the means of their application.

  4. Cerium-based conversion coatings on magnesium alloys

    NASA Astrophysics Data System (ADS)

    Castano Londono, Carlos Eduardo

    This research is primarily focused on gaining a better understanding of the deposition and corrosion behavior of cerium-based conversion coatings (CeCCs) on AZ31B and AZ91D Mg alloys. Deposition of homogenous and protective CeCCs was highly dependent on the surface preparation steps. The best results were obtained when Mg samples underwent grinding, acid cleaning, and alkaline cleaning processes. This reduced the number of active cathodic sites and promoted the formation of a protective Al-rich Mg oxide/hydroxide layer. Electrochemical properties of the CeCCs were also strongly correlated with morphological, microstructural, and chemical characteristics. Protective CeCCs were deposited on both AZ31 and AZ91 Mg alloys using a range of deposition times (5 to 180 s) and temperatures (10 to 80 °C). However, shorter deposition times (5 s) and lower deposition temperatures (~10 °C) showed higher impedance and longer bath stability than other deposition conditions. The increase in impedance was related with fewer cracks and smaller nodule sizes. Additional investigations of post-treated CeCCs exposed to NaCl environments showed an increased in the total impedance. The increase in corrosion protection of the CeCCs was associated with an overall increase in coating thickness from 400 to 800 nm. A microstructural evolution from ~3 nm nodular nanocrystals of CeO2/CePO4*H2O embedded in an amorphous matrix to >50 nm CePO4*H2O nanocrystals was responsible for the electrochemically active corrosion protection. Exposure of CeCCs to sunlight in humid environments promoted the reduction of Ce(IV) into Ce(III) species compared to unexposed coatings. This reduction process was related with photocatalytic water oxidation reaction.

  5. Mechanisms of larval midgut damage following exposure to phoxim and repair of phoxim-induced damage by cerium in Bombyx mori.

    PubMed

    Yu, Xiaohong; Sun, Qingqing; Li, Bing; Xie, Yi; Zhao, Xiaoyang; Hong, Jie; Sheng, Lei; Sang, Xuezi; Gui, Suxin; Wang, Ling; Shen, Weide; Hong, Fashui

    2015-04-01

    Bombyx mori is an important economic animal for silk production. However, it is liable to be infected by organophosphorus pesticide that can contaminate its food and growing environment. It has been known that organophosphorus pesticide including phoxim exposure may damage the digestive systems, produce oxidative stress and neurotoxicity in silkworm B. mori, whereas cerium treatment has been demonstrated to relieve phoxim-induced toxicity in B. mori. However, very little is known about the molecular mechanisms of midgut injury due to phoxim exposure and B. mori protection after cerium pretreatment. The aim of this study was to evaluate the midgut damage and its molecular mechanisms, and the protective role of cerium in B. mori following exposure to phoxim. The results showed that phoxim exposure led to severe midgut damages and oxidative stress; whereas cerium relieved midgut damage and oxidative stress caused by phoxim in B. mori. Furthermore, digital gene expression suggested that phoxim exposure led to significant up-regulation of 94 genes and down-regulation of 52 genes. Of these genes, 52 genes were related with digestion and absorption, specifically, the significant alterations of esterase, lysozyme, amylase 48, and lipase expressions. Cerium pretreatment resulted in up-regulation of 116 genes, and down-regulation of 29 genes, importantly, esterase 48, lipase, lysozyme, and α-amylase were up-regulated. Treatment with Phoxim + CeCl3 resulted in 66 genes up-regulation and 39 genes down-regulation; specifically, levels of esterase 48, lipase, lysozyme, and α-amylase expression in the midgut of silkworms were significantly increased. Therefore, esterase 48, lipase, lysozyme, and α-amylase may be potential biomarkers of midgut toxicity caused by phoxim exposure. These findings may expand the application of rare earths in sericulture.

  6. On the system cerium-platinum-silicon

    SciTech Connect

    Gribanov, Alexander Grytsiv, Andriy; Royanian, Esmaeil; Rogl, Peter; Bauer, Ernst; Giester, Gerald; Seropegin, Yurii

    2008-11-15

    Phase relations in the ternary system Ce-Pt-Si have been established for the isothermal section at 800 deg. C based on X-ray powder diffraction, metallography, scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) techniques on about 120 alloys, which were prepared by various methods employing arc-melting under argon or powder reaction sintering. Nineteen ternary compounds were observed. Atom order in the crystal structures of {tau}{sub 18}-Ce{sub 5}(Pt,Si){sub 4} (Pnma; a=0.77223(3) nm, b=1.53279(8) nm c=0.80054(5) nm), {tau}{sub 3}-Ce{sub 2}Pt{sub 7}Si{sub 4} (Pnma; a=1.96335(8) nm, b=0.40361(4) nm, c=1.12240(6) nm) and {tau}{sub 10}-CePtSi{sub 2} (Cmcm; a=0.42943(2) nm, b=1.67357(5) nm, c=0.42372(2) nm) was determined by direct methods from X-ray single-crystal CCD data and found to be isotypic with the Sm{sub 5}Ge{sub 4}-type, the Ce{sub 2}Pt{sub 7}Ge{sub 4}-type and the CeNiSi{sub 2}-type, respectively. Rietveld refinements established the atom arrangement in the structures of Pt{sub 3}Si (Pt{sub 3}Ge-type, C2/m, a=0.7724(2) nm, b=0.7767(2) nm, c=0.5390(2) nm, {beta}=133.86(2){sup o}), {tau}{sub 16}-Ce{sub 3}Pt{sub 5}Si (Ce{sub 3}Pd{sub 5}Si-type, Imma, a=0.74025(8) nm, b=1.2951(2) nm, c=0.7508(1) nm) and {tau}{sub 17}-Ce{sub 3}PtSi{sub 3} (Ba{sub 3}Al{sub 2}Ge{sub 2}-type, Immm, a=0.41065(5) nm, b=0.43221(5) nm, c=1.8375(3) nm). Phase equilibria in Ce-Pt-Si are characterised by the absence of cerium solubility in platinum silicides. Cerium silicides and cerium platinides, however, dissolve significant amounts of the third component, whereby random substitution of the almost equally sized atom species platinum and silicon is reflected in extended homogeneous regions at constant Ce content such as for {tau}{sub 13}-Ce(Pt{sub x}Si{sub 1-x}){sub 2}, {tau}{sub 6}-Ce{sub 2}Pt{sub 3+x}Si{sub 5-x} or {tau}{sub 7}-CePt{sub 2-x}Si{sub 2+x}. - Graphical abstract: Phase relations in the ternary system Ce-Pt-Si have been established for the isothermal

  7. Cerium fluoride, a new fast, heavy scintillator

    SciTech Connect

    Moses, W.W.; Derenzo, S.E.

    1988-11-01

    We describe the scintillation properties of Cerium Fluoride (CeF/sub 3/), a newly discovered, heavy (6.16 g/cm/sup 3/), inorganic scintillator. Its fluorescence decay lifetime, measured with the delayed coincidence method, is described by a single exponential with a 27 /+-/ ns time constant. The emission spectrum peaks at a wavelength of 340 nm, and drops to less than 10% of its peak value at 315 nm and 460 nm. When a 1 cm optical quality cube of CeF/sub 3/ is excited with 511 keV photons, a photopeak with a 20% full width at half maximum is observed at approximately half the light output of a Bismuth Germanate (BGO) crystal with similar geometry. We also present measurements of the decay time and light output of CeF/sub 3/ doped with three rare-earth elements (Dy, Er, and Pr). The short fluorescence lifetime, high density, and reasonable light output of this new scintillator suggest that it would be useful for applications where high counting rates, good stopping power, and nanosecond timing are important, such as medical imaging and nuclear science. 5 refs., 6 figs., 1 tab.

  8. Cerium-iron-based magnetic compounds

    DOEpatents

    Zhou, Chen; Pinkerton, Frederick E.; Herbst, Jan F.

    2017-01-17

    New magnetic materials containing cerium, iron, and small additions of a third element are disclosed. These materials comprise compounds Ce(Fe.sub.12-xM.sub.x) where x=1-4, having the ThMn.sub.12 tetragonal crystal structure (space group I4/mmm, #139). Compounds with M=B, Al, Si, P, S, Sc, Co, Ni, Zn, Ga, Ge, Zr, Nb, Hf, Ta, and W are identified theoretically, and one class of compounds based on M=Si has been synthesized. The Si cognates are characterized by large magnetic moments (4.pi.M.sub.s greater than 1.27 Tesla) and high Curie temperatures (264.ltoreq.T.sub.c.ltoreq.305.degree. C.). The Ce(Fe.sub.12-xM.sub.x) compound may contain one or more of Ti, V, Cr, and Mo in combination with an M element. Further enhancement in T.sub.c is obtained by nitriding the Ce compounds through heat treatment in N.sub.2 gas while retaining the ThMn.sub.12 tetragonal crystal structure; for example CeFe.sub.10Si.sub.2N.sub.1.29 has T.sub.c=426.degree. C.

  9. Characterization of cerium fluoride nanocomposite scintillators

    SciTech Connect

    Stange, Sy; Esch, Ernst I; Brown, Leif O; Couture, Aaron J; Mckigney, Edward A; Muenchausen, Ross E; Del Sesto, Rico E; Gilbertson, Robert D; Mccleskey, T Mark; Reifarth, Rene

    2009-01-01

    Measurement of the neutron capture cross-sections of a number of short-lived isotopes would advance both pure and applied scientific research. These cross-sections are needed for calculation of criticality and waste production estimates for the Advanced Fuel Cycle Initiative, for analysis of data from nuclear weapons tests, and to improve understanding of nucleosynthesis. However, measurement of these cross-sections would require a detector with a faster signal decay time than those used in existing neutron capture experiments. Crystals of faster detector materials are not available in sufficient sizes and quantities to supply these large-scale experiments. Instead, we propose to use nanocomposite detectors, consisting of nanoscale particles of a scintillating material dispersed in a matrix material. We have successfully fabricated cerium fluoride (CeF{sub 3}) nanoparticles and dispersed them in a liquid matrix. We have characterized this scintillator and have measured its response to neutron capture. Results of the optical, structural, and radiation characterization will be presented.

  10. Catalytic wet peroxidation of pyridine bearing wastewater by cerium supported SBA-15.

    PubMed

    Subbaramaiah, V; Srivastava, Vimal Chandra; Mall, Indra Deo

    2013-03-15

    Cerium supported SBA-15 (Ce/SBA-15) was synthesized by two-step synthesis method in acidic medium. It was further characterized by various characterization techniques such as X-ray diffraction, field-emission scanning electron microscopy, Fourier transform infrared spectroscopy and N2 adsorption-desorption pore size distribution analysis. The Ce/SBA-15 showed highly ordered meso-structure with pore diameter≈70-100Ǻ and pore volume≈0.025cm(3)/g. Ce/SBA-15 was further evaluated as a catalyst for the oxidation of highly toxic and non-biodegradable material, pyridine, by catalytic wet-peroxidation method. The effects of various operating parameters such as catalyst dose (0.5-6g/l), stoichiometric ratio of H2O2/pyridine (1-6), initial pyridine concentration (50-800mg/l) and temperature (313-358K) have been evaluated and optimized. Ce/SBA-15 showed stable performance during reuse for six cycles with negligible cerium leaching. Kinetic and thermodynamic parameters and operation cost have also been determined.

  11. Gene-Expression Changes in Cerium Chloride-Induced Injury of Mouse Hippocampus

    PubMed Central

    Sheng, Lei; Zhu, Liyuan; Guan, Ning; Gui, Suxin; Sang, Xuezi; Zhao, Xiaoyang; Sun, Qingqing; Wang, Ling; Cheng, Jie; Hu, Renping; Hong, Fashui

    2013-01-01

    Cerium is widely used in many aspects of modern society, including agriculture, industry and medicine. It has been demonstrated to enter the ecological environment, is then transferred to humans through food chains, and causes toxic actions in several organs including the brain of animals. However, the neurotoxic molecular mechanisms are not clearly understood. In this study, mice were exposed to 0.5, 1, and 2 mg/kg BW cerium chloride (CeCl3) for 90 consecutive days, and their learning and memory ability as well as hippocampal gene expression profile were investigated. Our findings suggested that exposure to CeCl3 led to hippocampal lesions, apoptosis, oxidative stress and impairment of spatial recognition memory. Furthermore, microarray data showed marked alterations in the expression of 154 genes involved in learning and memory, immunity and inflammation, signal transduction, apoptosis and response to stress in the 2 mg/kg CeCl3 exposed hippocampi. Specifically, the significant up-regulation of Axud1, Cdc37, and Ube2v1 caused severe apoptosis, and great suppression of Adcy8, Fos, and Slc5a7 expression led to impairment of mouse cognitive ability. Therefore, Axud1, Cdc37, Ube2v1, Adcy8, Fos, and Slc5a7 may be potential biomarkers of hippocampal toxicity caused by CeCl3 exposure. PMID:23573234

  12. In vivo protective role against water contamination with cerium via chronic administration of omega 3.

    PubMed

    Beltifa, Asma; Borgi, Mohamed Ali; Ferieni, Anouar; Elfekih, Abdelfettah; Mansour, Hedi Ben; Allagui, Mohamed Sallah

    2017-01-01

    In the present study, adult, healthy male Wistar rats (120 ± 10 g) were pre-treated by intragastric administration of cerium chloride (CeCl3) 10 mg/kg (BW) each day during 60 days. Control animal were treated with omega 3, a polyunsaturated fatty acid (ω-3), by an intragastric administration at 10 mg/kg of BW for 60 days. Our results showed that CeCl3-induced alterations in all tested oxidative stress markers. In fact, CeCl3-induced the increase the level of both the creatinine concentration and the expression of lactate dehydrogenase, alkaline phosphatase, and transaminase activities in serum. On the other hand, CeCl3 significantly increased the levels of lipid peroxidation in the renal and hepatic tissues. The capacity of CeCl3 to generate reactive oxygen species (ROS) could explain his ability to induce morphological alterations, such as centrilobular hemorrhage, hepatic necrosis, and vacuolization of the cytoplasm in hepatic tissues, and the atrophy of the glomerulus and dilatation of urinary space in renal tissues. However, omega 3, after gastric administration, reduced significantly the toxic effect caused by CeCl3 according to his high ability to scavenge ROS. The present study indicates that omega 3 is a significant compound with protective activity against intoxication with heavy metal, the cerium, and thus may be useful for chemoprevention.

  13. Study on the adsorptive stripping voltammetric determination of trace cerium at a carbon paste electrode modified in situ with cetyltrimethylammonium bromide

    NASA Astrophysics Data System (ADS)

    Liu, Shumei; Li, Junan; Zhang, Shijie; Zhao, Jianqing

    2005-12-01

    A procedure was developed for the determination of trace cerium based on the oxidation of the absorbed cerium (III)-alizarin complexon (ALC) complex at a carbon paste electrode (CPE) modified in situ with cetyltrimethylammonium bromide (CTAB). Optimum experiment conditions included 2.0 × 10 -6 mol l -1 ALC, 6.0 × 10 -5 mol l -1 CTAB , 0.1 mol l -1 acetic acid and sodium acetate (HAc-NaAc) and 0.2 mol l -1 potassium biphthalate (KHP), pH 5.0, an accumulation potential of -0.1 V, and a scan rate of 100 mV s -1. Linearity between peak currents and concentrations existed for 8.0 × 10 -10 to 8.0 × 10 -9 mol l -1 for 120 s accumulation and 8.0 × 10 -9 to 1.0 × 10 -7 mol l -1 for 60 s accumulation. The detection limit after a 120 s preconcentration was 6.0 × 10 -10 mol l -1 (S/N = 3). The relative standard deviation was 4.9% for eight successive determinations on the same electrode surface at 2.0 × 10 -8 mol l -1 level. The procedure was expected to determine trace cerium with elevated selectivity. The results were quite consistent with the certified values for the determination of cerium in rare earth nodular cast iron samples.

  14. The ternary system cerium-palladium-silicon

    SciTech Connect

    Lipatov, Alexey; Gribanov, Alexander; Grytsiv, Andriy; Rogl, Peter; Murashova, Elena; Seropegin, Yurii; Giester, Gerald; Kalmykov, Konstantin

    2009-09-15

    Phase relations in the ternary system Ce-Pd-Si have been established for the isothermal section at 800 deg. C based on X-ray powder diffraction and EMPA techniques on about 130 alloys, which were prepared by arc-melting under argon or powder reaction sintering. Eighteen ternary compounds have been observed to participate in the phase equilibria at 800 deg. C. Atom order was determined by direct methods from X-ray single-crystal counter data for the crystal structures of tau{sub 8}-Ce{sub 3}Pd{sub 4}Si{sub 4} (U{sub 3}Ni{sub 4}Si{sub 4}-type, Immm; a=0.41618(1), b=0.42640(1), c=2.45744(7) nm), tau{sub 16}-Ce{sub 2}Pd{sub 14}Si (own structure type, P4/nmm; a=0.88832(2), c=0.69600(2) nm) and also for tau{sub 18}-CePd{sub 1-x}Si{sub x} (x=0.07; FeB-type, Pnma; a=0.74422(5), b=0.45548(3), c=0.58569(4) nm). Rietveld refinements established the atom arrangement in the structures of tau{sub 5}-Ce{sub 3}PdSi{sub 3} (Ba{sub 3}Al{sub 2}Ge{sub 2}-type, Immm; a=0.41207(1), b=0.43026(1), c=1.84069(4) nm) and tau{sub 13}-Ce{sub 3-x}Pd{sub 20+x}Si{sub 6} (0<=x<=1, Co{sub 20}Al{sub 3}B{sub 6}-type, Fm3-barm; a=1.21527(2) nm). The ternary compound Ce{sub 2}Pd{sub 3}Si{sub 3} (structure-type Ce{sub 2}Rh{sub 1.35}Ge{sub 4.65}, Pmmn; a=0.42040(1), b=0.42247(1), c=1.72444(3) nm) was detected as a high-temperature compound, however, does not participate in the equilibria at 800 deg. C. Phase equilibria in Ce-Pd-Si are characterized by the absence of cerium solubility in palladium silicides. Mutual solubility among cerium silicides and cerium-palladium compounds are significant whereby random substitution of the almost equally sized atom species palladium and silicon is reflected in extended homogeneous regions at constant Ce-content such as for tau{sub 2}-Ce(Pd{sub x}Si{sub 1-x}){sub 2} (AlB{sub 2}-derivative type), tau{sub 6}-Ce(Pd{sub x}Si{sub 1-x}){sub 2} (ThSi{sub 2}-type) and tau{sub 7}-CePd{sub 2-x}Si{sub 2+x}. The crystal structures of compounds tau{sub 4}-Ce{sub a}pprox{sub 8}Pd

  15. Synthesis, characterization and magnetic evaluation of praseodymium modified cerium oxide

    NASA Astrophysics Data System (ADS)

    Cruz Pacheco, A. F.; Gómez Cuaspud, J. A.; Parra Vargas, C. A.

    2017-01-01

    This paper report the synthesis, characterization and magnetic evaluation of Ce0.6Pr0.4O2 system using a chemical route that involves the combustion of citrate species. The precursors were characterized by Fourier transform infrared spectroscopy (FTIR), to identify, the main vibrational bands associated with the organic material after combustion process. The structural analysis by X-ray diffraction (XRD) revealed the obtaining of an Fm-3m (225) cubic phase with a particle size around 10nm. Finally, the measurement of the magnetization as a function of applied magnetic field and of susceptibility showed a perfect paramagnetic behaviour.

  16. Cerium oxide nanoparticles: green synthesis and biological applications

    PubMed Central

    Charbgoo, Fahimeh; Ahmad, Mansor Bin; Darroudi, Majid

    2017-01-01

    CeO2 nanoparticles (NPs) have shown promising approaches as therapeutic agents in biology and medical sciences. The physicochemical properties of CeO2-NPs, such as size, agglomeration status in liquid, and surface charge, play important roles in the ultimate interactions of the NP with target cells. Recently, CeO2-NPs have been synthesized through several bio-directed methods applying natural and organic matrices as stabilizing agents in order to prepare biocompatible CeO2-NPs, thereby solving the challenges regarding safety, and providing the appropriate situation for their effective use in biomedicine. This review discusses the different green strategies for CeO2-NPs synthesis, their advantages and challenges that are to be overcome. In addition, this review focuses on recent progress in the potential application of CeO2-NPs in biological and medical fields. Exploiting biocompatible CeO2-NPs may improve outcomes profoundly with the promise of effective neurodegenerative therapy and multiple applications in nanobiotechnology. PMID:28260887

  17. Aqueous medium induced optical transitions in cerium oxide nanoparticles

    SciTech Connect

    Inerbaev, Talgat M.; Karakoti, Ajay S.; Kuchibhatla, S. V. N. T.; Kumar, Amit; Masunov, Artem E.; Seal, Sudipta

    2015-03-07

    Experimental and theoretical investigations were performed to investigate the effect of water on optical properties of nanoceria as a function of Ce3+ concentration. Theoretical studies based on density functional plane-wave calculations reveal that the indirect optical transitions in bare ceria nanoparticles are red-shifted with an increase in the concentration of Ce3+. However, ceria nanoparticles model with adsorbed water molecules show a blue shift in the indirect optical spectra under identical conditions. Direct optical transitions are almost independent of Ce3+ concentration but show a pronounced blue shift in the aqueous environment relative to the bare nanoparticles. The theoretical study is consistent with our experimental observation in difference of shift behaviour in bare and aqueous suspended ceria nanoparticles. This change from red- to blue-shift in indirect optical transitions is associated with the polarization effect of water molecules on f-electron states.

  18. Cerium oxide nanoparticles: green synthesis and biological applications.

    PubMed

    Charbgoo, Fahimeh; Ahmad, Mansor Bin; Darroudi, Majid

    2017-01-01

    CeO2 nanoparticles (NPs) have shown promising approaches as therapeutic agents in biology and medical sciences. The physicochemical properties of CeO2-NPs, such as size, agglomeration status in liquid, and surface charge, play important roles in the ultimate interactions of the NP with target cells. Recently, CeO2-NPs have been synthesized through several bio-directed methods applying natural and organic matrices as stabilizing agents in order to prepare biocompatible CeO2-NPs, thereby solving the challenges regarding safety, and providing the appropriate situation for their effective use in biomedicine. This review discusses the different green strategies for CeO2-NPs synthesis, their advantages and challenges that are to be overcome. In addition, this review focuses on recent progress in the potential application of CeO2-NPs in biological and medical fields. Exploiting biocompatible CeO2-NPs may improve outcomes profoundly with the promise of effective neurodegenerative therapy and multiple applications in nanobiotechnology.

  19. Density functional studies of model cerium oxide nanoparticles.

    PubMed

    Loschen, Christoph; Migani, Annapaola; Bromley, Stefan T; Illas, Francesc; Neyman, Konstantin M

    2008-10-01

    Density functional plane-wave calculations have been performed to investigate a series of ceria nanoparticles (CeO2-x)(n), n Ce3+ reduction have been accounted for through the use of an effective on-site Coulomb repulsive interaction within the so-called DFT+U approach. Twelve nanoparticles of up to 2 nm in diameter and of both cuboctahedral and octahedral forms are chosen as representative model systems. Energetic and structural effects of oxygen vacancy formation in these nanoparticles are discussed with respect to those in the bulk and on extended surfaces. We show that the average interatomic distances of the nanoparticles are most significantly affected by the creation of oxygen vacancies. The formation energies of non-stoichiometric nanoparticles (CeO2-x)(n) are found to scale linearly with the average coordination number of Ce atoms; where x < 0 species, containing partially reduced O atoms, are less stable. The stability of octahedral ceria particles at small sizes, and the predicted strong propensity of Ce cations to acquire a reduced state at lower coordinated sites, is supported by interatomic potential-based global optimisations probing the low energy isomers of the Ce19O32 nanoparticle.

  20. Impact of cerium oxide nanoparticles on cilantro ( Coriandrum sativum)

    NASA Astrophysics Data System (ADS)

    Morales, Maria Isabel

    Studies have shown that plants exposed to ENPs suffer different types of stress. Other studies have revealed that plants can take up and accumulate CeO2 NPs without modification. Thus, these NPs could enter the food chain through edible plants, posing a threat for human health. Cilantro (Coriandrum sativum) is a worldwide culinary and medicinal plant consumed either as a fresh herb or a spice. In this research, cilantro plants were germinated and cultivated for 30 days in organic soil treated with CeO2 NPs at concentrations varying from 0 to 500 mg kg -1. Subsequently, plant organs were analyzed by using spectroscopic techniques and biochemical assays. Results indicate that at 125 mg kg -1, the CeO2 NPs significantly increased the root size compared with the other treatments. The ICP-OES results showed that plants exposed to 500 mg kg-1 had significantly (p ≤ 0.05) more Ce in shoots and roots compared to the other treatments. Results from the biochemical assays showed that at 125 mg kg-1, catalese activity significantly increased in shoots and ascorbate peroxidase in roots (p ≤ 0.05). In addition, the FTIR analyses revealed that at 125 mg kg-1, the CeO2 NPs changed the chemical environment of the carbohydrates within the cilantro shoots, for which changes in the area of the stretching frequencies were observed. Moreover, analyses of antioxidant compounds showed a significant ( p ≤ 0.05) reduction on total phenolic content in shoots of cilantro plants treated with 500 mg CeO2 NPs kg-1 . This suggests that the CeO2 NPs have the potential to diminish the ability of cilantro plants to scavenge reactive oxygen species. The multi-elemental analysis showed that plants treated with CeO2 at the 500 mg kg-1 treatment had a significant ( p ≤ 0.05) reduction in shoots' sulfur, silicon, and zinc accumulation. The results of this research indicate that the CeO2 NPs at 500 mg CeO2 kg-1 concentration cause a reduction in the antioxidant ability and nutritional properties of cilantro plants.

  1. Cerium Oxide Nanoparticle Nose-Only Inhalation Exposures ...

    EPA Pesticide Factsheets

    There is a critical need to assess the health effects associated with exposure of commercially produced NPs across the size ranges reflective of that detected in the industrial sectors that are generating, as well as incorporating, NPs into products. Generation of stable and low concentrations of size-fractionated nanoscale aerosols in nose-only chambers can be difficult, and when the aerosol agglomerates during generation, the problems are significantly increased. One problem is that many nanoscale aerosol generators have higher aerosol output and/or airflow than can be accommodated by a nose-only inhalation chamber, requiring much of the generated aerosol to be diverted to exhaust. Another problem is that mixing vessels used to modulate the fluctuating output from aerosol generators can cause substantial wall losses, consuming much of the generated aerosol. Other available aerosol generation systems can produce nanoscale aerosols from nanoparticles (NPs), however these NPs are generated in real time and do not approximate the physical and chemical characteristics of NPs that are commercially produced exposing the workers and the public. The health effects associated with exposure to commercial NP production, which are more morphologically and size heterogeneous, is required for risk assessment. To overcome these problems, a low-consumption dry-particulate nanoscale aerosol generator was developed to deliver stable concentrations in the range of 10–5000 µg

  2. Cerium; crystal structure and position in the periodic table.

    PubMed

    Johansson, Börje; Luo, Wei; Li, Sa; Ahuja, Rajeev

    2014-09-17

    The properties of the cerium metal have intrigued physicists and chemists for many decades. In particular a lot of attention has been directed towards its high pressure behavior, where an isostructural volume collapse (γ phase → α phase) has been observed. Two main models of the electronic aspect of this transformation have been proposed; one where the 4f electron undergoes a change from being localized into an itinerant metallic state, and one where the focus is on the interaction between the 4f electron and the conduction electrons, often referred to as the Kondo volume collapse model. However, over the years it has been repeatedly questioned whether the cerium collapse really is isostructural. Most recently, detailed experiments have been able to remove this worrisome uncertainty. Therefore the isostructural aspect of the α-γ transition has now to be seriously addressed in the theoretical modeling, something which has been very much neglected. A study of this fundamental characteristic of the cerium volume collapse is made in present paper and we show that the localized [rlhar2 ] delocalized 4f electron picture provides an adequate description of this unique behavior. This agreement makes it possible to suggest that an appropriate crossroad position for cerium in The Periodic Table.

  3. Progress on Radiative Transition Probabilities in Neutral Cerium

    NASA Astrophysics Data System (ADS)

    Curry, J. J.

    2009-10-01

    Cerium is a rare-earth atom that is currently used in energy-efficient metal-halide lamps because of its rich visible emission spectrum. More than 20,000 lines have been observed and classified for neutral cerium in the wavelength range of 340 nm to 1 μm (Bill Martin, unpublished). We recently derived more than 500 absolute transition probabilities from existing experimental data (J. Phys. D: Appl. Phys. 2009). Lawler and Den Hartog at the University of Wisconsin have made measurements that are expected to produce a few thousand transition probabilities. These advances, however, leave the data situation far short of what is needed to simulate an accurate global emission spectrum in numerical models of metal-halide lamps containing cerium. One possibility for closing this gap is through atomic structure calculations. Although it may be difficult for calculations to match the accuracy of measurements for any given transition, the global spectral distribution produced with calculated transition probabilities may still be satisfactory. For such a large number of lines, calculations may be the only realistic way to produce a reasonably complete set of data. We will discuss our recent atomic structure calculations of neutral cerium with the Cowan code based on a parametric fit of calculated energy level values to experimental values.

  4. Cerium; Crystal Structure and Position in The Periodic Table

    PubMed Central

    Johansson, Börje; Luo, Wei; Li, Sa; Ahuja, Rajeev

    2014-01-01

    The properties of the cerium metal have intrigued physicists and chemists for many decades. In particular a lot of attention has been directed towards its high pressure behavior, where an isostructural volume collapse (γ phase → α phase) has been observed. Two main models of the electronic aspect of this transformation have been proposed; one where the 4f electron undergoes a change from being localized into an itinerant metallic state, and one where the focus is on the interaction between the 4f electron and the conduction electrons, often referred to as the Kondo volume collapse model. However, over the years it has been repeatedly questioned whether the cerium collapse really is isostructural. Most recently, detailed experiments have been able to remove this worrisome uncertainty. Therefore the isostructural aspect of the α-γ transition has now to be seriously addressed in the theoretical modeling, something which has been very much neglected. A study of this fundamental characteristic of the cerium volume collapse is made in present paper and we show that the localized ⇌ delocalized 4f electron picture provides an adequate description of this unique behavior. This agreement makes it possible to suggest that an appropriate crossroad position for cerium in The Periodic Table. PMID:25227991

  5. Structural, optical and photocatalytic activity of cerium doped zinc aluminate

    NASA Astrophysics Data System (ADS)

    Sumathi, Shanmugam; Kavipriya, A.

    2017-03-01

    Zinc aluminate and cerium-doped zinc aluminate nanoparticles are synthesised by co-precipitation method. Ammonium hydroxide is used as a precipitating agent. The synthesised compounds are characterised by powder X-ray diffraction (XRD), Fourier transform Infrared spectroscopy (FT-IR), Ultraviolet diffuse reflectance spectroscopy (UV-DRS), Thermogravimetric analysis (TGA), Scanning electron microscopy (SEM) and Surface area measurements. The photocatalytic activity of zinc aluminate and cerium doped zinc aluminate nanoparticles are studied under the UV light and visible light taking methylene blue as a model pollutant. The amount of catalyst, concentration of dye solution and time are optimised under UV-light. Degradation of methylene blue under the UV-light is found to be 99% in 20 min with 10 mg of cerium doped catalyst. Compared to visible light degradation, the degradation of dye under UV-light is higher. Cerium doping in zinc aluminate (ZnAl2O4:Ce3+) increased the photocatalytic activity of zinc aluminate.

  6. Nanostructured manganese oxide on silica aerogel: a new catalyst toward water oxidation.

    PubMed

    Najafpour, Mohammad Mahdi; Salimi, Saeideh; Madadkhani, Sepideh; Hołyńska, Małgorzata; Tomo, Tatsuya; Allakhverdiev, Suleyman I

    2016-12-01

    Herein we report on the synthesis and characterization of nano-sized Mn oxide/silica aerogel with low density as a good catalyst toward water oxidation. The composite was synthesized by a simple and low-cost hydrothermal procedure. In the next step, we studied the composite in the presence of cerium(IV) ammonium nitrate and photo-produced Ru(bpy) 3(3+) as a water-oxidizing catalyst. The low-density composite is a good Mn-based catalyst with turnover frequencies of ~0.3 and 0.5 (mmol O2/(mol Mn·s)) in the presence of Ru(bpy) 3(3+) and cerium(IV) ammonium nitrate, respectively. In addition to the water-oxidizing activities of the composite under different conditions, its self-healing reaction in the presence of cerium(IV) ammonium nitrate was also studied.

  7. Ruthenium carbonyl catalyst supported on ceric oxide for preparation of olefins from synthesis gas

    DOEpatents

    Pierantozzi, Ronald

    1985-01-01

    A catalyst comprising a ruthenium carbonyl compound deposited on a cerium oxide-containing support material provides for the selective synthesis of low molecular weight olefinic hydrocarbons from mixtures of hydrogen and carbon monoxide.

  8. Preparation of olefins from synthesis gas using ruthenium supported on ceric oxide

    DOEpatents

    Pierantozzi, Ronald

    1985-01-01

    A catalyst comprising a ruthenium carbonyl compound deposited on a cerium oxide-containing support material provides for the selective synthesis of low molecular weight olefinic hydrocarbons from mixtures of hydrogen and carbon monoxide.

  9. Preparation of olefins from synthesis gas using ruthenium supported on ceric oxide

    DOEpatents

    Pierantozzi, R.

    1985-04-09

    A catalyst comprising a ruthenium carbonyl compound deposited on a cerium oxide-containing support material provides for the selective synthesis of low molecular weight olefinic hydrocarbons from mixtures of hydrogen and carbon monoxide.

  10. Ruthenium carbonyl catalyst supported on ceric oxide for preparation of olefins from synthesis gas

    DOEpatents

    Pierantozzi, R.

    1985-04-02

    A catalyst comprising a ruthenium carbonyl compound deposited on a cerium oxide-containing support material provides for the selective synthesis of low molecular weight olefinic hydrocarbons from mixtures of hydrogen and carbon monoxide.

  11. Deuterium isotope effect on the induction period of the cerium catalyzed Belousov-Zhabotinsky reaction

    NASA Astrophysics Data System (ADS)

    Rossi, Federico; Simoncini, Eugenio; Marchettini, Nadia; Tiezzi, Enzo

    2009-02-01

    In this work we present results about the deuterium isotopic effect on the global kinetics of a cerium catalyzed Belousov-Zhabotinsky reaction. A nonlinear dependence of the induction period upon the percentage of deuterated reactants was found in batch conditions. In order to understand this result, we investigated two reaction pathways responsible for the length of the induction period, namely: (a) the reaction between the enolic form of the malonic acid with molecular bromine and (b) the oxidation of malonic acid by the Ce(IV) ion. In both cases we obtained a linear dependence of the kinetic constants on the percentage of deuterated reactants. Nevertheless, by inserting the experimental values in the MBM (Marburg-Budapest-Missoula) model, we were able to qualitatively simulate the observed trend of the induction period.

  12. Apparatus and method for oxidizing organic materials

    DOEpatents

    Surma, Jeffrey E.; Bryan, Garry H.; Geeting, John G. H.; Butner, R. Scott

    1998-01-01

    The invention is a method and apparatus using high cerium concentration in the anolyte of an electrochemical cell to oxidize organic materials. The method and apparatus further use an ultrasonic mixer to enhance the oxidation rate of the organic material in the electrochemical cell.

  13. Apparatus and method for oxidizing organic materials

    DOEpatents

    Surma, J.E.; Bryan, G.H.; Geeting, J.G.H.; Butner, R.S.

    1998-01-13

    The invention is a method and apparatus using high cerium concentration in the anolyte of an electrochemical cell to oxidize organic materials. The method and apparatus further use an ultrasonic mixer to enhance the oxidation rate of the organic material in the electrochemical cell. 6 figs.

  14. Changes in Physiological and Agronomical Parameters of Barley (Hordeum vulgare) Exposed to Cerium and Titanium Dioxide Nanoparticles.

    PubMed

    Marchiol, Luca; Mattiello, Alessandro; Pošćić, Filip; Fellet, Guido; Zavalloni, Costanza; Carlino, Elvio; Musetti, Rita

    2016-03-17

    The aims of our experiment were to evaluate the uptake and translocation of cerium and titanium oxide nanoparticles and to verify their effects on the growth cycle of barley (Hordeum vulgare L.). Barley plants were grown to physiological maturity in soil enriched with either 0, 500 or 1000 mg · kg(-1) cerium oxide nanoparticles (nCeO₂) or titanium oxide nanoparticles (nTiO₂) and their combination. The growth cycle of nCeO₂ and nTiO₂ treated plants was about 10 days longer than the controls. In nCeO₂ treated plants the number of tillers, leaf area and the number of spikes per plant were reduced respectively by 35.5%, 28.3% and 30% (p ≤ 0.05). nTiO₂ stimulated plant growth and compensated for the adverse effects of nCeO₂. Concentrations of Ce and Ti in aboveground plant fractions were minute. The fate of nanomaterials within the plant tissues was different. Crystalline nTiO₂ aggregates were detected within the leaf tissues of barley, whereas nCeO₂ was not present in the form of nanoclusters.

  15. Changes in Physiological and Agronomical Parameters of Barley (Hordeum vulgare) Exposed to Cerium and Titanium Dioxide Nanoparticles

    PubMed Central

    Marchiol, Luca; Mattiello, Alessandro; Pošćić, Filip; Fellet, Guido; Zavalloni, Costanza; Carlino, Elvio; Musetti, Rita

    2016-01-01

    The aims of our experiment were to evaluate the uptake and translocation of cerium and titanium oxide nanoparticles and to verify their effects on the growth cycle of barley (Hordeum vulgare L.). Barley plants were grown to physiological maturity in soil enriched with either 0, 500 or 1000 mg·kg−1 cerium oxide nanoparticles (nCeO2) or titanium oxide nanoparticles (nTiO2) and their combination. The growth cycle of nCeO2 and nTiO2 treated plants was about 10 days longer than the controls. In nCeO2 treated plants the number of tillers, leaf area and the number of spikes per plant were reduced respectively by 35.5%, 28.3% and 30% (p ≤ 0.05). nTiO2 stimulated plant growth and compensated for the adverse effects of nCeO2. Concentrations of Ce and Ti in aboveground plant fractions were minute. The fate of nanomaterials within the plant tissues was different. Crystalline nTiO2 aggregates were detected within the leaf tissues of barley, whereas nCeO2 was not present in the form of nanoclusters. PMID:26999181

  16. Perovskite catalysts for oxidative coupling

    DOEpatents

    Campbell, K.D.

    1991-06-25

    Perovskites of the structure A[sub 2]B[sub 2]C[sub 3]O[sub 10] are useful as catalysts for the oxidative coupling of lower alkane to heavier hydrocarbons. A is alkali metal; B is lanthanide or lanthanum, cerium, neodymium, samarium, praseodymium, gadolinium or dysprosium; and C is titanium.

  17. Perovskite catalysts for oxidative coupling

    DOEpatents

    Campbell, Kenneth D.

    1991-01-01

    Perovskites of the structure A.sub.2 B.sub.2 C.sub.3 O.sub.10 are useful as catalysts for the oxidative coupling of lower alkane to heavier hydrocarbons. A is alkali metal; B is lanthanide or lanthanum, cerium, neodymium, samarium, praseodymium, gadolinium or dysprosium; and C is titanium.

  18. Oxide modified air electrode surface for high temperature electrochemical cells

    DOEpatents

    Singh, Prabhakar; Ruka, Roswell J.

    1992-01-01

    An electrochemical cell is made having a porous cermet electrode (16) and a porous lanthanum manganite electrode (14), with solid oxide electrolyte (15) between them, where the lanthanum manganite surface next to the electrolyte contains a thin discontinuous layer of high surface area cerium oxide and/or praseodymium oxide, preferably as discrete particles (30) in contact with the air electrode and electrolyte.

  19. Ab initio electronic and lattice dynamical properties of cerium dihydride

    NASA Astrophysics Data System (ADS)

    Gurel, Tanju; Eryigit, Resul

    2007-03-01

    The rare-earth metal hydrides are interesting systems because of the dramatic structural and electronic changes due to the hydrogen absorption and desorption. Among them, cerium dihydride (CeH2) is one of the less studied rare-earth metal-hydride. To have a better understanding, we have performed an ab initio study of electronic and lattice dynamical properties of CeH2 by using pseudopotential density functional theory within local density approximation (LDA) and a plane-wave basis. Electronic band structure of CeH2 have been obtained within LDA and as well as GW approximation. Lattice dynamical properties are calculated using density functional perturbation theory. The phonon spectrum is found to contain a set of high-frequency (˜ 850-1000 cm-1) optical bands, mostly hydrogen related, and low frequency cerium related acoustic modes climbing to 160 cm^ -1 at the zone boundary.

  20. Shock wave experiments to examine the multiphase properties of cerium

    SciTech Connect

    Jensen, Brian James

    2009-01-01

    There is a scientific need to obtain new data to constrain and refine next generation multi-phase equation-of-state (EOS) for metals. Experiments are needed to locate phase boundaries, determine transition kinetic times, and to obtain EOS and Hugoniot data for relevant phases. The objectives of the current work was to examine the multiphase properties for cerium including the dynamic melt boundary and the low-pressure solid-solid phase transition through the critical point. These objectives were addressed by performing plate impact experiment that used multiple experimental configuration including front-surface impact experiments to directly measure transition kinetics, multislug experiments that used the overtake method to measure sound speeds at pressure, and preheat experiments to map out phase boundaries. Preliminary data and analysis obtained for cerium will be presented.

  1. Dissociation of cerium(III) and neodymium(III) phthalocyanines

    NASA Astrophysics Data System (ADS)

    Lomova, T. N.

    2015-07-01

    The kinetics of dissociation of phthalocyanine complexes with cerium(III) and neodymium(III) (X)LnPc (X = Cl-, Br-, AcO-) under the action of acetic acid in ethanol with isolation of the macrocyclic ligand depending on the temperature was studied. The kinetic equations with the numerical values of rate constants, activation parameters, and the stoichiometric mechanisms with the limiting simple reaction between the nonionized AcOH molecule and (phthalocyaninato)lanthanide(III) in the axially coordinated ((X)LnPc, cerium complexes) or axially ionized ([(AcOH)LnPc]+X-, neodymium complexes) state were derived by solving the direct and inverse problems. As shown by a comparative analysis of quantitative kinetic data, the state is determined by the electronic structure of the metal cation and the mutual effect of the axial and equatorial ligands in the first coordination sphere.

  2. Optical Response of Shocked Cerium-Doped Lutetium Oxyorthosilicate

    SciTech Connect

    G. D. Stevens

    2003-03-01

    Shock experiments were performed in order to characterize the triboluminescent signature of cerium-doped lutetium oxyorthosilicate (LSO:Ce). This material shows prompt, nano-second timescale light emission when driven by explosive detonation. When properly applied to a surface, it may be used as a shock arrival sensor, and also for imaging the propagation of a shock front. Triboluminescent rise times, spectral content, and spatial resolution measurements are presented.

  3. Jet formation in cerium metal to examine material strength

    SciTech Connect

    Jensen, B. J. Cherne, F. J.; Prime, M. B.; Yeager, J. D.; Ramos, K. J.; Hooks, D. E.; Cooley, J. C.; Dimonte, G.; Fezzaa, K.; Iverson, A. J.; Carlson, C. A.

    2015-11-21

    Examining the evolution of material properties at extreme conditions advances our understanding of numerous high-pressure phenomena from natural events like meteorite impacts to general solid mechanics and fluid flow behavior. Recent advances in synchrotron diagnostics coupled with dynamic compression platforms have introduced new possibilities for examining in-situ, spatially resolved material response with nanosecond time resolution. In this work, we examined jet formation from a Richtmyer-Meshkov instability in cerium initially shocked into a transient, high-pressure phase, and then released to a low-pressure, higher-temperature state. Cerium's rich phase diagram allows us to study the yield stress following a shock induced solid-solid phase transition. X-ray imaging was used to obtain images of jet formation and evolution with 2–3 μm spatial resolution. From these images, an analytic method was used to estimate the post-shock yield stress, and these results were compared to continuum calculations that incorporated an experimentally validated equation-of-state (EOS) for cerium coupled with a deviatoric strength model. Reasonable agreement was observed between the calculations and the data illustrating the sensitivity of jet formation on the yield stress values. The data and analysis shown here provide insight into material strength during dynamic loading which is expected to aid in the development of strength aware multi-phase EOS required to predict the response of matter at extreme conditions.

  4. Cerium Substitution in Yttrium Iron Garnet: Valence State, Structure, and Energetics

    SciTech Connect

    Guo, Xiaofeng; Tavakoli, Amir H.; Sutton, Steve; Kukkadapu, Ravi K.; Qi, Liang; Lanzirotti, Anthony; Newville, Mathew; Asta, Mark D.; Navrotsky, Alexandra

    2014-01-28

    The garnet structure is a promising nuclear waste form because it can accommodate various actinide elements. Y3Fe5O12 (YIG) is a model composition for such substitutions. Since cerium (Ce) can be considered an analogue of actinide elements such as thorium (Th), plutonium (Pu), and uranium (U), studying the local structure and thermodynamic stability of Ce-substituted YIG (Ce:YIG) can provide insights into the structural and energetic aspects of large ion substitution in garnets. Single phases of yttrium iron garnet with Ce substitution up to 20 mol % (Y3-xCexFe5O12 with 0 ≤ x ≤ 0.2) were synthesized through a citrate-nitrate combustion method. The oxidation state of cerium was examined by X-ray absorption near edge structure spectroscopy (XANES); the oxidation state and site occupancy of Fe as a function of Ce loading also was monitored by 57Fe-Mössbauer spectroscopy. These measurements establish that Ce is predominantly in the trivalent state at low substitution levels, while a mixture of trivalent and tetravalent states are observed at higher concentrations. Fe was predominately trivalent and exists in multiple environments. High temperature oxide melt solution calorimetry was used to determine the enthalpy of formation of these Ce-substituted YIG garnets. The thermodynamic analysis demonstrated that, although there is an entropic driving force for the substitution of Ce for Y, the substitution reaction is enthalpically unfavorable. The experimental results are complemented by electronic structure calculations performed within the framework of density functional theory (DFT) with Hubbard-U corrections, which reproduce the observed increase in the tendency for tetravalent Ce to be present with higher loading of Ce. The DFT+U results suggest that the energetics underlying the formation of tetravalent Ce involves a competition between an unfavorable energy to oxidize Ce and reduce Fe, and a favorable contribution due to strain-energy reduction. The structural

  5. Potential of a Hydrometallurgical Recycling Process for Catalysts to Cover the Demand for Critical Metals, Like PGMs and Cerium

    NASA Astrophysics Data System (ADS)

    Steinlechner, Stefan; Antrekowitsch, Jürgen

    2015-02-01

    The metals from the platinum group are used in many different industries, for example dental, jewelry, and chemicals. Nevertheless, the most important use is based on their catalytic properties. Approximately 50% of platinum and palladium are used as automotive and industrial catalysts. In case of rhodium, an even higher percentage (around 80-90%) is used as an alloying element in the active layer of different catalysts. The high required amount of 300-900 kg of treated ore to obtain approximately 1 g of PGM is responsible for the high prices. On average, the contents in the ore of Pt and Pd are 5-10 times higher than Rh and Ru and around 50 times higher than Ir and Os. Additionally, the regional limitation of ore bodies leads to a strong dependence on mainly South Africa and Russia as PGM suppliers. Based on the strong discrepancy in supply and demand of PGM's around the world, recycling of catalysts is mandatory and meaningful from the ecological and economical point of view. Based on the high prices of PGM, the industry is forced to improve the efficiency of catalysts, which is done by improving the wash coat technology. By using rare-earth elements, like cerium oxide, the surface can be increased and the ability to supply oxygen is secured. As a side effect, cerium as an additional critical element is introduced into the recycling circuit of catalytic converters, forming a further valuable component and forming a major challenge for common pyrometallurgical converter recycling. Therefore, this article introduces a hydrometallurgical process, developed together with Railly&Hill Inc., for PGM as well as cerium recovery from catalytic converters.

  6. Cerium valence in cerium-exchanged Preyssler`s heteropolyanion through x-ray absorption near-edge structure

    SciTech Connect

    Antonio, M.R.; Soderholm, L.

    1994-12-21

    The sodium ion in the heteropolytungstate known as the Preyssler anion, [NaP{sub 5}W{sub 30}O{sub 110}]{sup 14{minus}}, was exchanged with cerium from aqueous solutions of ammonium ceric nitrate, [NH{sub 4}]{sub 2}Ce{sup IV}(NO{sub 3}){sub 6}, as described by Creaser et al. The valence of cerium in this heteropolyanion was determined through Ce L-edge XANES, X-ray absorption near-edge structure. The XANES results demonstrate that cerium is trivalent in the Ce-exchanged Preyssler heteropolyanion in the solid state and in aqueous solution (1 M H{sub 2}SO{sub 4}) at rest potential and after constant-potential, bulk electrolysis at-0.55 V vs SCE. The encapsulated sodium ion of the Preyssler anion was shown to be directly exchangeable with Ce{sup III} by prolonged (48 h), high temperature (165 {degrees}C) aqueous treatments with either Ce(NO{sub 3}){sub 3}{lg_bullet}6H{sub 2}O or CeCl{sub 3}{lg_bullet}7H{sub 2}O in Teflon-lined pressure vessels.

  7. Modified cermet fuel electrodes for solid oxide electrochemical cells

    DOEpatents

    Ruka, Roswell J.; Spengler, Charles J.

    1991-01-01

    An exterior porous electrode (10), bonded to a solid oxygen ion conducting electrolyte (13) which is in contact with an interior electrode (14), contains coarse metal particles (12) of nickel and/or cobalt, having diameters from 3 micrometers to 35 micrometers, where the coarse particles are coated with a separate, porous, multiphase layer (17) containing fine metal particles of nickel and/or cobalt (18), having diameters from 0.05 micrometers to 1.75 micrometers and conductive oxide (19) selected from cerium oxide, doped cerium oxide, strontium titanate, doped strontium titanate and mixtures thereof.

  8. Antioxidant and antigenotoxic properties of CeO2 NPs and cerium sulphate: Studies with Drosophila melanogaster as a promising in vivo model.

    PubMed

    Alaraby, Mohamed; Hernández, Alba; Annangi, Balasubramanyam; Demir, Esref; Bach, Jordi; Rubio, Laura; Creus, Amadeu; Marcos, Ricard

    2015-01-01

    Although in vitro approaches are the most used for testing the potential harmful effects of nanomaterials, in vivo studies produce relevant information complementing in vitro data. In this context, we promote the use of Drosophila melanogaster as a suitable in vivo model to characterise the potential risks associated to nanomaterials exposure. The main aim of this study was to evaluate different biological effects associated to cerium oxide nanoparticles (Ce-NPs) and cerium (IV) sulphate exposure. The end-points evaluated were egg-to-adult viability, particles uptake through the intestinal barrier, gene expression and intracellular reactive oxygen species (ROS) production by haemocytes, genotoxicity and antigenotoxicity. Transmission electron microscopy images showed internalisation of Ce-NPs by the intestinal barrier and haemocytes, and significant expression of Hsp genes was detected. In spite of these findings, neither toxicity nor genotoxicity related to both forms of cerium were observed. Interestingly, Ce-NPs significantly reduced the genotoxic effect of potassium dichromate and the intracellular ROS production. No morphological malformations were detected after larvae treatment. This study highlights the importance of D. melanogaster as animal model in the study of the different biological effects caused by nanoparticulated materials, at the time that shows its usefulness to study the role of the intestinal barrier in the transposition of nanomaterials entering via ingestion.

  9. Molecular mechanisms of silk gland damage caused by phoxim exposure and protection of phoxim-induced damage by cerium chloride in Bombyx mori.

    PubMed

    Li, Bing; Sun, Qingqing; Yu, Xiaohong; Xie, Yi; Hong, Jie; Zhao, Xiaoyang; Sang, Xuezi; Shen, Weide; Hong, Fashui

    2015-09-01

    It is known that exposure to organophosphorus pesticides (OP) including phoxim can produce oxidative stress, neurotoxicity, and greatly attenuate cocooning rate in the silkworm, Bombyx mori. Cerium treatment has been demonstrated to relieve phoxim-induced toxicity in B. mori; however, very little is known about the molecular mechanisms of silk gland injury due to OP exposure and protection of gland damage due to cerium pretreatment. The aim of this study was to evaluate silk gland damage and its molecular mechanisms in phoxim-induced silkworm toxicity and the protective mechanisms of cerium following exposure to phoxim. The results showed that phoxim exposure resulted in severe gland damage, reductions in protein synthesis and the cocooning rate of silkworms. Cerium (Ce) attenuated gland damage caused by phoxim, promoted protein synthesis, increased the antioxidant capacity of the gland and increased the cocooning rate of B. mori. Furthermore, digital gene expression data suggested that phoxim exposure led to significant up-regulation of 714 genes and down-regulation of 120 genes. Of these genes, 122 were related to protein metabolism, specifically, the down-regulated Ser2, Ser3, Fib-L, P25, and CYP450. Ce pretreatment resulted in up-regulation of 162 genes, and down-regulation of 141 genes, importantly, Ser2, Ser3, Fib-L, P25, and CYP333B8 were up-regulated. Treatment with CeCl3 + phoxim resulted in higher levels of Fib-L, P25, Ser2, Ser3, CAT, TPx, and CYP333B8 expression in the silk gland of silkworms. These findings indicated that Ce increased cocooning rate via the promotion of silk protein synthesis-related gene expression in the gland under phoxim-induced toxicity. These findings may expand the application of rare earths in sericulture.

  10. Doppler-shifted optical absorption characterization of plume-lateral expansion in laser ablation of a cerium target

    NASA Astrophysics Data System (ADS)

    Miyabe, M.; Oba, M.; Iimura, H.; Akaoka, K.; Maruyama, Y.; Ohba, H.; Tampo, M.; Wakaida, I.

    2012-12-01

    The temporal evolution of the ablation plume of cerium was investigated by absorption spectroscopy. Cerium oxide pellets were ablated in a helium atmosphere by second-harmonic radiation (532 nm) from a Nd:YAG laser at a fluence of 0.5 J/cm2. The lateral velocity (expansion velocity horizontal to the sample surface) of the plume was determined from the magnitude of the Doppler splitting of the absorption spectra measured close to the sample surface. The lateral velocities of neutral and singly ionized atoms were systematically investigated by varying several parameters, such as ambient gas pressure, ablation laser fluence, observation timing, and observation height. In addition, temporal profiles of the absorption signal were measured by detuning the probe laser frequency from the atomic resonant frequency in order to obtain the temporal variation of the velocity. On the basis of the drag force model, the slowing coefficients for atomic and ionic species in a helium atmosphere were evaluated along with lateral velocity in a vacuum. This study may help in understanding the plume dynamics effect on deposited film properties as well as optimizing experimental conditions for ablation-based spectroscopic analysis.

  11. Effect of ultrasound treatment on the morpho-structural and luminescent characteristics of cerium doped yttrium silicate phosphors

    SciTech Connect

    Muresan, L.E.; Cadis, A.I.; Perhaita, I.; Silipas, D.T.; Tudoran, L. Barbu

    2015-08-15

    Highlights: • Y{sub 2}SiO{sub 5}:Ce is prepared by gel combustion in ultrasound conditions (US). • Morpho-structural characteristics are revealed based on FTIR, SEM, XRD, BET. • Incorporation of Ce{sup 3+} in X1/X2 type centers depends on preparative conditions. • US treatment increases the luminescent performances up to 151%. - Abstract: Cerium activated yttrium silicate (Y{sub 2}SiO{sub 5}:Ce) phosphors were prepared by gel-combustion, using yttrium–cerium nitrate as oxidizer, aspartic acid as fuel and TEOS as source of silicon. Two modalities for samples preparation were approached namely: the classical gel-combustion and sonication gel-combustion. The ultrasound treatment during the gelling stage has a positive effect on the structural and luminescent characteristics of the final product. Therefore, a well crystallized single X2–Y{sub 2}SiO{sub 5} phase phosphor was obtained at 1200 °C. Based on FT-IR and XRD investigations, conversion of X1 to X2–Y{sub 2}SiO{sub 5} phases is observed as the firing temperature is varied (1100 °C, 1200 °C, 1300 °C 1400 °C). The ultrasound treatment leads to smaller particle size and enhances the luminescent performances up to 151% in comparison with samples prepared by classical way.

  12. Cerium redox cycles and rare earth elements in the Sargasso Sea

    SciTech Connect

    Sholkovitz, E.R.; Schneider, D.L. )

    1991-10-01

    Two profiles of the rare earth elements (REEs) are reported for the upper water column of the Sargasso Sea. The trivalent-only REEs have remarkably constant concentrations in the upper 500m of an April 1989 profile and in the upper 200m of a May 1989 profile. In contrast, Ce concentrations decrease smoothly with increasing depth. In April 1989 Ce decreases from 15.7 pmol/kg at 20 m to 5.1 pmol/kg at 750 m. Cerium, which has Redox transformations in seawater, behaves anomalously with respect to its REE(III) neighbors. While both dissolved Ce and Mn have elevated concentrations in the upper 200m, their vertical gradients are distinctly different. In contrast to Mn, which reaches a minimum dissolved concentration near the zone (150-250 m) of a particulate Mn maximum, Ce is being removed both near this zone and to depths of at least 750m. These new profiles indicate that Ce is involved in an upper ocean redox cycle. This interpretation is consistent with the MOFFETT (1990) incubation tracer experiments on the same May 1989 seawater. He showed that Ce(III) oxidation is biologically mediated, probably light inhibited, increases with depth, and 3-4 times slower than Mn(II) oxidation in the 100-200 m zone. CERoclines provide new information into the fine scale zonation of redox process operating in the upper columns of oligotrophic oceans.

  13. Test beam results of a cerium fluoride crystal matrix

    NASA Astrophysics Data System (ADS)

    Auffray, E.; Bourotte, J.; Beckers, T.; Chipaux, M.; Commichau, V.; Dafinei, I.; Depasse, P.; Djambazov, L.; Dydak, U.; El Mamouni, H.; Fay, J.; Felcini, M.; Goyot, M.; Haguenauer, M.; Hillemans, H.; Hofer, H.; Ille, B.; Kirn, T.; Kryn, D.; Lebrun, P.; Lecomte, P.; Lecoq, P.; Martin, J. P.; Maurelli, G.; Mattioli, M.; Melnikov, I.; Nessi-Tedaldi, F.; Pacciani, L.; Pirro, S.; Raghavan, R.; Ren, D.; Reynaud, M.; Röser, U.; Sahuc, P.; Schmitz, D.; Schneegans, M.; Schwenke, J.; Soric, I.; Viertel, G.; von Gunten, H. P.; Walder, J. P.; Waldmeier-Wicki, S.

    1995-11-01

    A Cerium Fluoride matrix of 3 × 3 towers with Silicon photodiode readout has been tested in electron and pion beams from 10 to 150 GeV energy. The matrix was assembled with a selection of crystals out of a total of over 40 large crystals (up to 20 cm long and 3 cm × 3 cm in cross section) from various producers. Despite less than optimal geometry and crystal quality, an energy resolution of 0.5% for energies ≥ 50 GeV has been obtained. Fast shaping amplifier prototypes were tested and their performance was found to be appropriate for operation in an LHC-like environment.

  14. Dissolution of Neptunium and Plutonium Oxides Using a Catalyzed Electrolytic Process

    SciTech Connect

    Hylton, TD

    2004-10-25

    This report discusses the scoping study performed to evaluate the use of a catalyzed electrolytic process for dissolving {sup 237}Np oxide targets that had been irradiated to produce {sup 238}Pu oxide. Historically, these compounds have been difficult to dissolve, and complete dissolution was obtained only by adding hydrofluoric acid to the nitric acid solvent. The presence of fluoride in the mixture is undesired because the fluoride ions are corrosive to tank and piping systems and the fluoride ions cause interferences in the spectrophotometric analyses. The goal is to find a dissolution method that will eliminate these issues and that can be incorporated into a processing system to support the domestic production and purification of {sup 238}Pu. This study evaluated the potential of cerium(IV) ions, a strong oxidant, to attack and dissolve the oxide compounds. In the dissolution process, the cerium(IV) ions are reduced to cerium(III) ions, which are not oxidants. Therefore, an electrolytic process was incorporated to continuously convert cerium(III) ions back to cerium(IV) ions so that they can dissolve more of the oxide compounds. This study showed that the neptunium and plutonium oxides were successfully dissolved and that more development work should be performed to optimize the procedure.

  15. Catalyst for reduction of nitrogen oxides

    DOEpatents

    Ott, Kevin C.

    2010-04-06

    A Selective Catalytic Reduction (SCR) catalyst was prepared by slurry coating ZSM-5 zeolite onto a cordierite monolith, then subliming an iron salt onto the zeolite, calcining the monolith, and then dipping the monolith either into an aqueous solution of manganese nitrate and cerium nitrate and then calcining, or by similar treatment with separate solutions of manganese nitrate and cerium nitrate. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).

  16. Novel borothermal route for the synthesis of lanthanum cerium hexaborides and their field emission properties

    SciTech Connect

    Menaka; Patra, Rajkumar; Ghosh, Santanu; Ganguli, Ashok K.

    2012-10-15

    The present study describes the development of a simple approach to stabilize polycrystalline lanthanum cerium hexaborides without using any flux and at ambient pressure. The nanostructured lanthanum-cerium borides were synthesized using hydroxide precursors. These precursors (La{sub 1-x}Ce{sub x}(OH){sub 3}, x=0.1, 0.2, 0.3 and 0.5) were synthesized via hydrothermal route in the presence of Tergitol (surfactant, nonylphenol ethoxylate) as a capping agent. The precursors on heating with boron at 1300 Degree-Sign C lead to the formation of nanostructures (cubes, rods and pyramids) of lanthanum cerium hexaboride. We have investigated the field emission behaviour of the hexaboride films fabricated by spin coating. It was observed that the pyramidal shaped nanostructures of La{sub 0.5}Ce{sub 0.5}B{sub 6} shows excellent field emission characteristics with high field enhancement factor of 4502. - Graphical abstract: Nanostructured lanthanum cerium hexaboride with efficient field emission have fabricated by low temperature hydroxide precursor mediated route. Highlights: Black-Right-Pointing-Pointer New methodology to prepare lanthanum cerium hexaboride at 1300 Degree-Sign C via borothermal route. Black-Right-Pointing-Pointer Nanostructured lanthanum cerium hexaboride film by spin coating process. Black-Right-Pointing-Pointer Nanopyramids based lanthanum cerium hexaboride shows excellent field emission.

  17. Hydrothermal synthesis of cerium titanate nanorods and its application in visible light photocatalysis

    SciTech Connect

    Pei, L.Z. Liu, H.D.; Lin, N.; Yu, H.Y.

    2015-01-15

    Highlights: • Cerium titanate nanorods have been synthesized by a simple hydrothermal process. • The size of the cerium titanate nanorods can be controlled by growth conditions. • Cerium titanate nanorods exhibit good photocatalytic activities for methyl blue. - Abstract: Cerium titanate nanorods have been prepared via a hydrothermal process using sodium dodecyl sulfate (SDS) as the surfactant. The cerium titanate nanorods have been analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and ultraviolet–visible (UV–vis) diffuse reflectance spectrum. XRD shows that the nanorods are composed of CeTi{sub 21}O{sub 38} phase. Electron microscopy observations indicate that the nanorods have good single crystalline nature. The diameter and length of the nanorods are about 50–200 nm and 1–2 μm, respectively. Cerium titanate nanorods have a band gap of 2.65 eV. The photocatalytic activities of the nanorods have been investigated by degrading methylene blue (MB) under visible light irradiation. MB solution with the concentration of 10 mg L{sup −1} can be degraded totally with the irradiation time increasing to 240 min. Cerium titanate nanorods exhibit great potential in photocatalytic degradation of MB under visible light irradiation.

  18. Formation of δ-Lactones with anti-Baeyer-Villiger Regiochemistry - Investigations into the Mechanism of the Cerium-Catalyzed Aerobic Coupling of β-Oxoesters with Enol Acetates.

    PubMed

    Christoffers, Jens; Geibel, Irina; Dierks, Anna; Müller, Thomas

    2017-02-23

    The cerium-catalyzed, aerobic coupling of β-oxoesters with enol acetates and dioxygen yields δ-lactones with a 1,4-diketone moiety. In contrast to the Baeyer-Villiger oxidation (BVO), where the higher substituted residue migrates, in this case of an oxidative C-C coupling reaction the less substituted alkyl residue undergoes a 1,2-shift. An endoperoxidic oxycarbenium ion comparable to the Criegee intermediate in the BVO is proposed as a reaction intermediate and submitted to conformational analysis by computational methods. As a result, the inverse regiochemistry is explained by a primary stereoelectronic effect. A Hammett analysis using different donor and acceptor substituted enol esters provides support for the oxycarbenium ion being the crucial intermediate in the rate determining step of the conversion. An overall mechanism is suggested with a radical chain reaction for the formation of endoperoxides from β-oxoesters, enol acetates and dioxygen with a cerium(IV) species as initiating reagent.

  19. Toxicity of cerium and thorium on Daphnia magna.

    PubMed

    Ma, Yuhui; Wang, Jingkun; Peng, Can; Ding, Yayun; He, Xiao; Zhang, Peng; Li, Na; Lan, Tu; Wang, Dongqi; Zhang, Zhaohui; Sun, Fuhong; Liao, Haiqing; Zhang, Zhiyong

    2016-12-01

    Cerium (Ce) and thorium (Th) are always thought to be chemically similar and have comparable toxic properties on living organisms. In the present study, the acute and chronic toxicity of these two elements to freshwater crustacean Daphnia magna were investigated in the modified reconstituted water (6mg/L KCl, 123mg/L MgSO4·7H2O, and 294mg/L CaCl2·2H2O in Milli-Q water, pH 7.8). It seemed that Ce and Th had comparable acute toxicity on Daphnia: 24/48h EC50 for Th and Ce were 7.3/4.7μM and 16.4/10.7μM, respectively. However, Ce was present as soluble ions while all of Th was present as particulate ThO2 in the exposure medium. Considering their different chemical forms and bioavailability, the toxic mechanisms of Ce(3+) and ThO2 on Daphnia would be totally different. To our knowledge, this is the first time to investigate the aquatic toxicity of thorium and cerium based on their actual chemical speciation in the exposure medium. The results also suggest that more attention should be paid on the detrimental effect of Th in the form of particulate ThO2.

  20. Cerium-Based Magnets: Novel High Energy Permanent Magnet Without Critical Elements

    SciTech Connect

    2012-01-01

    REACT Project: Ames Laboratory will develop a new class of permanent magnets based on the more commonly available element cerium for use in both EVs and renewable power generators. Cerium is 4 times more abundant and significantly less expensive than the rare earth element neodymium, which is frequently used in today’s most powerful magnets. Ames Laboratory will combine other metal elements with cerium to create a new magnet that can remain stable at the high temperatures typically found in electric motors. This new magnetic material will ultimately be demonstrated in a prototype electric motor, representing a cost-effective and efficient alternative to neodymium-based motors.

  1. Effect of cerium on temper embrittlement of P-doped Mn structural steels

    SciTech Connect

    Zhexi, Yuan; Shenhua, Song; Faulkner, R.G.; Tingdong, Xu

    1994-01-01

    The effect of cerium on temper embrittlement of P-doped Mn structural steels has been investigated by measurements of the ductile-brittle transition temperature and observations by AES, SIMS and SEM of the fracture surfaces of isothermally embrittled steels. It is shown that P can bring about the temper embrittlement of Mn structural steels; cerium may reduce the temper embrittlement of the steels and the segregation of cerium to grain boundaries may play an important part in reducing the temper embrittlement of the steels.

  2. Structural, topographical and electrical properties of cerium doped strontium barium niobate (Ce:SBN60) ceramics

    NASA Astrophysics Data System (ADS)

    Raj, S. Gokul; Mathivanan, V.; Kumar, G. Ramesh; Yathavan, S.; Mohan, R.

    2016-05-01

    Tungsten bronze type cerium doped strontium barium niobate (Ce:SBN - Sr0.6B0.4Nb2O6) ceramics were synthesized by solid state process. Cerium was used as dopant to improve its electrical properties. Influence of Ce+ ions on the photoluminescence properties was investigated in detail. The grain size topographical behavior of SBN powders and their associated abnormal grain growth (AGG) were completely analyzed through SEM studies. Finally dielectric, measurement discusses about the broad phase transition observed due to cerium dopant The results were discussed in detail.

  3. Magnetophotonic crystal with cerium substituted yttrium iron garnet and enhanced Faraday rotation angle.

    PubMed

    Yoshimoto, Takuya; Goto, Taichi; Isogai, Ryosuke; Nakamura, Yuichi; Takagi, Hiroyuki; Ross, C A; Inoue, M

    2016-04-18

    Magnetophotonic crystals (MPCs) comprising cerium-substituted yttrium iron garnet (CeYIG) sandwiched by two Bragg mirrors were fabricated by vacuum annealing. CeYIG was deposited on Bragg mirrors at room temperature and annealed in 5 Pa of residual air. No ceria or other non-garnet phases were detected. Cerium 3 + ions substituted on the yttrium sites and no cerium 4 + ions were found. The Faraday rotation angle of the MPC was -2.92° at a wavelength of λ = 1570 nm was 30 times larger than that of the CeYIG film. These results showed good agreement with calculated values derived using a matrix approach.

  4. Spatial Distribution Of Cerium Valence In Model Planar Pd/Ce0.7Zr0.3O2 Catalysts

    SciTech Connect

    Zhang, S.; Katz, M. B.; Sun, Kai; Ezekoye, Obiefune K.; Nandasiri, Manjula I.; Jen, H. W.; Graham, George W.; Pan, X. Q.

    2013-04-01

    The spatial distribution of cerium valence in H2-reduced model planar Pd/Ce0.7Zr0.3O2 catalysts was determined by electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM). Spherical reduction zones were found beneath each Pd particle, consistent with a Pd-catalyzed, oxygen anion diffusion-limited bulk oxide reduction process. Evidence was also found for a more extended surface reduction process, possibly associated with hydrogen spillover from the Pd particles.

  5. Stabilized tin-oxide-based oxidation/reduction catalysts

    NASA Technical Reports Server (NTRS)

    Jordan, Jeffrey D. (Inventor); Schryer, David R. (Inventor); Davis, Patricia P. (Inventor); Leighty, Bradley D. (Inventor); Watkins, Anthony Neal (Inventor); Schryer, Jacqueline L. (Inventor); Oglesby, Donald M. (Inventor); Gulati, Suresh T. (Inventor); Summers, Jerry C. (Inventor)

    2008-01-01

    The invention described herein involves a novel approach to the production of oxidation/reduction catalytic systems. The present invention serves to stabilize the tin oxide reducible metal-oxide coating by co-incorporating at least another metal-oxide species, such as zirconium. In one embodiment, a third metal-oxide species is incorporated, selected from the group consisting of cerium, lanthanum, hafnium, and ruthenium. The incorporation of the additional metal oxide components serves to stabilize the active tin-oxide layer in the catalytic process during high-temperature operation in a reducing environment (e.g., automobile exhaust). Moreover, the additional metal oxides are active components due to their oxygen-retention capabilities. Together, these features provide a mechanism to extend the range of operation of the tin-oxide-based catalyst system for automotive applications, while maintaining the existing advantages.

  6. Steric and electronic effects of 1,3-disubstituted cyclopentadienyl ligands on metallocene derivatives of Cerium, Titanium, Manganese, and Iron

    SciTech Connect

    Sofield, Chadwick Dean

    2000-05-01

    Sterically demanding 1,3-disubstituted cyclopentadienyl ligands were used to modify the physical properties of the corresponding metallocenes. Sterically demanding ligands provided kinetic stabilization for trivalent cerium compounds. Tris(di-t-butylcyclopentadienyl)cerium was prepared and anion competition between halides and cyclopentadienyl groups which had complicated synthesis of the tris(cyclopentadienyl)compound was qualitatively examined. Bis(di-t-butylcyclopentadienyl)cerium methyl was prepared and its rate of decomposition, by ligand redistribution, to tris(di-t-butylcyclopentadienyl)cerium was shown to be slower than the corresponding rate for less sterically demanding ligands. Asymmetrically substituted ligands provided a symmetry label for examination of chemical exchange processes. Tris[trimethylsilyl(t-butyl)cyclopentadienyl]cerium was prepared and the rate of interconversion between the C1 and C3 isomers was examined. The enthalpy difference between the two distereomers is 7.0 kJ/mol. The sterically demanding cyclopentadienyl ligands ansa-di-t-butylcyclopentadiene (Me2Si[(Me3C)2C5H3]2), ansa-bis(trimethylsilyl)cyclopentadiene (Me2Si[(Me3Si)2C5H3]2) and tetra-t-butylfulvalene and metallocene derivatives of the ligands were prepared and their structures were examined by single crystal X-ray crystallography. The effect that substituents on the cyclopentadienyl ring have on the pi-electron system of the ligand was examined through interaction between ligand and metal orbitals. A series of 1,3-disubstituted manganocenes was prepared and their electronic states were determined by solid-state magnetic susceptibility, electron paramagnetic resonance, X-ray crystallography, and variable temperature UV-vis spectroscopy. Spin-equilibria in [(Me3C)2C5H3]2Mn and [(Me3

  7. Determination of thorium and of rare earth elements in cerium earth minerals and ores

    USGS Publications Warehouse

    Carron, M.K.; Skinner, D.L.; Stevens, R.E.

    1955-01-01

    The conventional oxalate method for precipitating thorium and the rare earth elements in acid solution exhibits definite solubilities of these elements. The present work was undertaken to establish conditions overcoming these solubilities and to find optimum conditions for precipitating thorium and the rare earth elements as hydroxides and sebacates. The investigations resulted in a reliable procedure applicable to samples in which the cerium group elements predominate. The oxalate precipitations are made from homogeneous solution at pH 2 by adding a prepared solution of anhydrous oxalic acid in methanol instead of the more expensive crystalline methyl oxalate. Calcium is added as a carrier. Quantitative precipitation of thorium and the rare earth elements is ascertained by further small additions of calcium to the supernatant liquid, until the added calcium precipitates as oxalate within 2 minutes. Calcium is removed by precipitating the hydroxides of thorium and rare earths at room temperature by adding ammonium hydroxide to pH > 10. Thorium is separated as the sebacate at pH 2.5, and the rare earths are precipitated with ammonium sebacate at pH 9. Maximum errors for combined weights of thorium and rare earth oxides on synthetic mixtures are ??0.6 mg. Maximum error for separated thoria is ??0.5 mg.

  8. Press or pulse exposures determine the environmental fate of cerium nanoparticles in stream mesocosms.

    PubMed

    Baker, Leanne F; King, Ryan S; Unrine, Jason M; Castellon, Benjamin T; Lowry, Gregory V; Matson, Cole W

    2016-05-01

    Risk-assessment models indicate that stream ecosystems receiving municipal wastewater effluent may have the greatest potential for exposure to manufactured nanoparticles. The authors determined the fate of cerium oxide (CeO2 ) nanoparticles in outdoor stream mesocosms using 1) 1-time pulse addition of CeO2 nanoparticles, representative of accidental release, and 2) continuous, low-level press addition of CeO2 nanoparticles, representative of exposure via wastewater effluent. The pulse addition led to rapid nanoparticle floc formation, which appeared to preferentially deposit on periphyton in low-energy areas downstream from the location of the input, likely as a result of gravitational sedimentation. Floc formation limited the concentration of suspended nanoparticles in stream water to <5% of target and subsequent downstream movement. In contrast, press addition of nanoparticles led to higher suspended nanoparticle concentrations (77% of target) in stream water, possibly as a result of stabilization of suspended nanoparticles through interaction with dissolved organic carbon. Smaller nanoparticle aggregates appeared to preferentially adsorb to stream surfaces in turbulent sections, where Ce concentrations were highest in the press, likely a result of stochastic encounter with the surface. Streams receiving wastewater effluent containing nanoparticles may lead to exposure of aquatic organisms over a greater spatial extent than a similar amount of nanoparticles from an accidental release. Exposure models must take into account these mechanisms controlling transport and depositional processes.

  9. Microstructure, texture evolution and magnetic properties of strip-casting non-oriented 6.5 wt.% Si electrical steel doped with cerium

    SciTech Connect

    Li, Hao-Ze Liu, Hai-Tao; Liu, Zhen-Yu Wang, Guo-Dong

    2015-05-15

    A 0.3 mm thick non-oriented 6.5 wt.% Si electrical steel sheet doped with cerium is produced by twin-roll strip casting, hot rolling, warm rolling and annealing. A detailed study of the cerium precipitates in the as-cast strip, microstructure and texture evolution at different processing stages is carried out by electron probe micro-analysis, optical microscopy, X-ray diffraction and electron backscattered diffraction analysis. Grain interior distributing precipitates identified as Ce-oxides, Ce-oxysulfides and Ce-phosphides, and boundary distributing Ce-oxides and Ce-phosphides are observed in the as-cast strip. The initial as-cast strip is characterized by a much finer solidification microstructure and dominated by obvious < 001 >//ND texture through the strip thickness. After hot and warm rolling, inhomogeneous microstructure containing large amounts of in-grain shear bands is characterized by mixed < 110 >//RD and < 111 >//ND textures. The texture of the annealed sheet with a relatively large average grain size is far more optimized by the domination of the beneficial cube, rotated cube, (001)< 120 > to (001)< 130 > and Goss texture components, and the elimination of the detrimental γ-fiber texture, leading to a superior magnetic induction and improved iron loss. - Highlights: • An Fe–6.5 wt.% Si as-cast strip doped with cerium was produced. • A thin warm rolled sheet with limited edge cracks was obtained. • Microstructure and texture evolution at each stage were investigated. • Strong λ-fiber and Goss recrystallization textures were formed. • The magnetic properties of the annealed sheet were significantly improved.

  10. The Corrosion Behaviors of the Cerium Conversion Coatings on the Zinc Coating in a 5 % NaCl Solution

    NASA Astrophysics Data System (ADS)

    Zhang, Jianghong; Meng, Binfang; Wang, Xinying; Li, Wei

    2017-01-01

    The present paper investigated the impact of cerium on the corrosion resistance of zinc coating in a 5 % NaCl solution. Electrochemistry was used to measure the electrochemical parameters to compare the corrosion resistance of the zinc coating with that of the cerium conversion coating on the galvanized layer. SEM/EDS and XRD were adopted to analyze the appearance and phases of corrosion products of the cerium conversion coating and to probe the impact of cerium on the corrosion behavior of zinc coating in the Cl- media. The results showed that the cerium conversion coating formed on the zinc coating increased the zinc's corrosion resistance effectively, conversion coating with lower cerium content protected the substrate poorly, resulting in easy erosion of the zinc coating in the Cl- media. The corrosion products mainly consist of complexes, such as Zn(OH)xCly and Ce(OH)xCly.

  11. Measuring technique for thermal ionisation mass spectrometry of human tracer kinetic study with stable cerium isotopes.

    PubMed

    Keiser, Teresa; Höllriegl, Vera; Giussani, Augusto; Oeh, Uwe

    2011-06-01

    Thermal ionisation mass spectrometry (TIMS) method has been developed for the simultaneous detection of different cerium isotopes in biological samples (i.e., blood and urine) at very low concentrations. The work has been done in the frame of a biokinetic study, where different stable cerium isotopes have been administered orally and intravenously as tracers to the human body. In order to develop an appropriate detection method for the tracers in the biological samples, an optimum sample preparation technique has been set and adapted to the specific requirements of the analysis technique used, i.e., TIMS. For sample evaporation and ionisation, the double tantalum filament technique showed the best results. The ions produced were simultaneously collected on a secondary electron multiplier so that the isotopic ratios of the cerium isotopes in the biological samples could be measured. The technique has been optimised for the determination of cerium down to 1 ng loaded on the evaporation filament corresponding to cerium concentrations of down to 1 ng ml(-1) in the blood or urine samples. It has been shown that the technique is reliable in application and enables studies on cerium metabolism and biokinetics in humans without employing radioactive tracers.

  12. Effects of manganese deficiency and added cerium on nitrogen metabolism of maize.

    PubMed

    Gong, Xiaolan; Qu, Chunxiang; Liu, Chao; Hong, Mengmeng; Wang, Ling; Hong, Fashui

    2011-12-01

    Manganese is one of the essential microelements for plant growth, and cerium is a beneficial element for plant growth. However, whether manganese deficiency affects nitrogen metabolism of plants and cerium improves the nitrogen metabolism of plants by exposure to manganese-deficient media are still unclear. The main aim of the study was to determine the effects of manganese deficiency in nitrogen metabolism and the roles of cerium in the improvement of manganese-deficient effects in maize seedlings. Maize seedlings were cultivated in manganese present Meider's nutrient solution. They were subjected to manganese deficiency and to cerium chloride administered in the manganese-present and manganese-deficient media. Maize seedlings grown in the various media were measured for key enzyme activities involved in nitrogen metabolism, such as nitrate reductase, glutamate dehydrogenase, glutamine synthetase, and glutamic-oxaloace transaminase. We found that manganese deficiency restricted uptake and transport of NO(3)(-), inhibited activities of nitrogen-metabolism-related enzymes, such as nitrate reductase, glutamine synthetase, and glutamic-oxaloace transaminase, thus decreasing the synthesis of chlorophyll and soluble protein, and inhibited the growth of maize seedlings. Manganese deficiency promoted the activity of glutamate dehydrogenase and reduced the toxicity of excess ammonia to the plant, while added cerium relieved the damage to nitrogen metabolism caused by manganese deficiency in maize seedlings. However, cerium addition exerted positively to relieve the damage of nitrogen metabolism process in maize seedlings caused by exposure to manganese-deficient media.

  13. Interplay of spin-orbit and entropic effects in cerium

    SciTech Connect

    Lanata, Nicola; Yao, Yong-Xin; Wang, Cai-Zhuang; Ho, Kai-Ming; Kotliar, Gabriel

    2014-10-01

    We perform first-principles calculations of elemental cerium and compute its pressure-temperature phase diagram, finding good quantitative agreement with the experiments. Our calculations indicate that, while a signature of the volume-collapse transition appears in the free energy already at low temperatures, at higher temperatures this signature is enhanced because of the entropic effects, and originates an actual thermodynamical instability. Furthermore, we find that the catalyst determining this feature is—in all temperature regimes—a pressure-induced effective reduction of the f-level degeneracy due to the spin-orbit coupling. Our analysis suggests also that the lattice vibrations might be crucial in order to capture the behavior of the pressure-temperature transition line at large temperatures.

  14. Characterization of a zinc-cerium flow battery

    NASA Astrophysics Data System (ADS)

    Leung, P. K.; Ponce-de-León, C.; Low, C. T. J.; Shah, A. A.; Walsh, F. C.

    The performance of a divided, parallel-plate zinc-cerium redox flow battery using methanesulfonic acid electrolytes was studied. Eight two and three-dimensional electrodes were tested under both constant current density and constant cell voltage discharge. Carbon felt and the three-dimensional platinised titanium mesh electrodes exhibited superior performance over the 2-dimensional electrodes. The charge and discharge characteristics of the redox flow battery were studied under different operating conditions and Zn/Ce reactant, as well as methansulfonic acid concentration. The cell performance improved at higher operating temperatures and faster electrolyte flow velocities. The number of possible cycles increased at reduced states of charge. During 15 min charge/discharge per cycle experiment, 57 cycles were obtained and the zinc reaction was found to be the limiting process during long term operation.

  15. The Spin Glass-Kondo Competition in Disordered Cerium Systems

    NASA Astrophysics Data System (ADS)

    Magalhaes, S. G.; Zimmer, F.; Coqblin, B.

    2013-10-01

    We discuss the competition between the Kondo effect, the spin glass state and a magnetic order observed in disordered Cerium systems. We present firstly the experimental situation of disordered alloys such as CeNi1 - xCux and then the different theoretical approaches based on the Kondo lattice model, with different descriptions of the intersite exchange interaction for the spin glass. After the gaussian approach of the Sherrington-Kirkpatrick model, we discuss the Mattis and the van Hemmen models. Then, we present simple cluster calculations in order to describe the percolative evolution of the clusters from the cluster spin glass to the inhomogeneous ferromagnetic order recently observed in CeNi1 - xCux disordered alloys and finally we discuss the effect of random and transverse magnetic field.

  16. Structure and Electronic Properties of Cerium Orthophosphate: Theory and Experiment

    SciTech Connect

    Adelstein, Nicole; Mun, B. Simon; Ray, Hannah; Ross Jr, Phillip; Neaton, Jeffrey; De Jonghe, Lutgard

    2010-07-27

    Structural and electronic properties of cerium orthophosphate (CePO{sub 4}) are calculated using density functional theory (DFT) with the local spin-density approximation (LSDA+U), with and without gradient corrections (GGA-(PBE)+U), and compared to X-ray diffraction and photoemission spectroscopy measurements. The density of states is found to change significantly as the Hubbard parameter U, which is applied to the Ce 4f states, is varied from 0 to 5 eV. The calculated structural properties are in good agreement with experiment and do not change significantly with U. Choosing U = 3 eV for LDSA provides the best agreement between the calculated density of states and the experimental photoemission spectra.

  17. Magmatic oxygen fugacity estimated using zircon-melt partitioning of cerium

    NASA Astrophysics Data System (ADS)

    Smythe, Duane J.; Brenan, James M.

    2016-11-01

    Using a newly-calibrated relation for cerium redox equilibria in silicate melts (Smythe and Brenan, 2015), and an internally-consistent model for zircon-melt partitioning of Ce, we provide a method to estimate the prevailing redox conditions during crystallization of zircon-saturated magmas. With this approach, oxygen fugacities were calculated for samples from the Bishop tuff (USA), Toba tuff (Indonesia) and the Nain plutonic suite (Canada), which typically agree with independent estimates within one log unit or better. With the success of reproducing the fO2 of well-constrained igneous systems, we have applied our Ce-in-zircon oxygen barometer to estimating the redox state of Earth's earliest magmas. Using the composition of the Jack Hills Hadean zircons, combined with estimates of their parental magma composition, we determined the fO2 during zircon crystallization to be between FMQ -1.0 to +2.5 (where FMQ is the fayalite-magnetite-quartz buffer). Of the parental magmas considered, Archean tonalite-trondhjemite-granodiorite (TTG) compositions yield zircon-melt partitioning most similar to well-constrained modern suites (e.g., Sano et al., 2002). Although broadly consistent with previous redox estimates from the Jack Hills zircons, our results provide a more precise determination of fO2, narrowing the range for Hadean parental magmas by more than 8 orders of magnitude. Results suggest that relatively oxidized magmatic source regions, similar in oxidation state to that of 3.5 Ga komatiite suites, existed by ∼4.4 Ga.

  18. Manganese oxide supported on gold/iron as a water-oxidizing catalyst in artificial photosynthetic systems.

    PubMed

    Najafpour, Mohammad Mahdi; Hosseini, Seyedeh Maedeh; Zand, Zahra

    2016-05-31

    Herein, we reported that KMnO4 with iron nanoparticles coated with gold layers was a promising catalyst for water oxidation. The compound was characterized by scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, atomic absorption spectroscopy and electrochemistry. The new compound was a conductive, recyclable, highly dispersible, magnetically separable, environmentally friendly, and nano-sized catalyst for water oxidation via cerium(iv) ammonium nitrate or Ru(bpy)3(3+) and electrochemical water oxidation. The turnover frequency of Mn oxide/gold/iron for water oxidation via cerium(iv) ammonium nitrate is 0.4 mmol O2 per mol Mn per second, which shows that this catalyst is among the best Mn-based catalysts for water oxidation. We also showed a strategy for placing this catalyst on the surface of an electrode without adding any other compounds.

  19. Copper, Boron, and Cerium Additions in Type 347 Austenitic Steel to Improve Creep Rupture Strength

    NASA Astrophysics Data System (ADS)

    Laha, Kinkar; Kyono, J.; Shinya, Norio

    2012-04-01

    Type 347 austenitic stainless steel (18Cr-12Ni-Nb) was alloyed with copper (3 wt pct), boron (0.01 to 0.06 wt pct), and cerium (0.01 wt pct) with an aim to increase the creep rupture strength of the steel through the improved deformation and cavitation resistance. Short-term creep rupture strength was found to increase with the addition of copper in the 347 steel, but the long-term strength was inferior. Extensive creep cavitation deprived the steel of the beneficial effect of creep deformation resistance induced by nano-size copper particles. Boron and cerium additions in the copper-containing steel increased its creep rupture strength and ductility, which were more for higher boron content. Creep deformation, grain boundary sliding, and creep cavity nucleation and growth in the steel were found to be suppressed by microalloying the copper-containing steel with boron and cerium, and the suppression was more for higher boron content. An auger electron spectroscopic study revealed the segregation of boron instead of sulfur on the cavity surface of the boron- and cerium-microalloyed steel. Cerium acted as a scavenger for soluble sulfur in the steels through the precipitation of cerium sulfide (CeS). This inhibited the segregation of sulfur and facilitated the segregation of boron on cavity surface. Boron segregation on the nucleated cavity surface reduced its growth rate. Microalloying the copper-containing 347 steel with boron and cerium thus enabled to use the full extent of creep deformation resistance rendered by copper nano-size particle by increase in creep rupture strength and ductility.

  20. Apparatus and method for constant flow oxidizing of organic materials

    DOEpatents

    Surma, Jeffrey E.; Nelson, Norvell; Steward, G. Anthony; Bryan, Garry H.

    1999-01-01

    The invention is a method and apparatus using high cerium concentration in the anolyte of an electrochemical cell to oxidize organic materials. The method and apparatus further use an ultrasonic mixer to enhance the oxidation rate of the organic material in the electrochemical cell. A reaction vessel provides an advantage of independent reaction temperature control and electrochemical cell temperature control. A separate or independent reaction vessel may be used without an ultrasonic mixer to oxidize gaseous phase organic materials.

  1. Photocatalysis of S-metolachlor in aqueous suspension of magnetic cerium-doped mTiO2 core-shell under simulated solar light.

    PubMed

    Mermana, J; Sutthivaiyakit, P; Blaise, C; Gagné, F; Charnsethikul, S; Kidkhunthod, P; Sutthivaiyakit, S

    2017-02-01

    Magnetic cerium-doped mesoporous titanium dioxide was synthesized by combining sol-gel method and calcination using tetrabutanate and ammonium cerium nitrate as precursors and Pluronic P123 as a template coating on iron oxide covered with carbon in ethanol. The magnetic Ce-doped catalyst showed only anatase structure with a slight increase in lattice parameters compared to the undoped catalyst. The Ce LIII-edge X-ray absorption near-edge spectroscopy (XANES) spectra showed Ce(3+), and the cerium substitution doping into titanium dioxide was proposed. Degradation of S-metolachlor in aqueous magnetic photocatalyst suspension followed (pseudo) first-order kinetics in the presence of 0.5 g L(-1) of γ-Fe2O3@C@0.16 mol% Ce-mTiO2 with a half-life of 55.18 ± 1.63 min. Fifteen degradation products were identified, and their transformation routes of the photocatalytic degradation were then proposed. Complementary toxicity assessment of the treated S-metolachlor solution was undertaken with Environment Canada's algal microplate assay measuring growth inhibition (72-h IC50) in the freshwater chlorophyte Pseudokirchneriella subcapitata. This test method revealed a significant decrease in toxicity (1.7-fold reduction after 180 min of irradiation treatment), thereby confirming that the by-products formed following photocatalysis would be less harmful from an environmental point of view. Photocatalytic degradation of S-metolachlor thus appears to hold promise as a cost-effective treatment technology to diminish the presence of this herbicide in aquatic systems.

  2. Catalyst and method for reduction of nitrogen oxides

    DOEpatents

    Ott, Kevin C.

    2008-05-27

    A Selective Catalytic Reduction (SCR) catalyst was prepared by slurry coating ZSM-5 zeolite onto a cordierite monolith, then subliming an iron salt onto the zeolite, calcining the monolith, and then dipping the monolith either into an aqueous solution of manganese nitrate and cerium nitrate and then calcining, or by similar treatment with separate solutions of manganese nitrate and cerium nitrate. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).

  3. Catalyst and method for reduction of nitrogen oxides

    DOEpatents

    Ott, Kevin C.

    2008-08-19

    A Selective Catalytic Reduction (SCR) catalyst was prepared by slurry coating ZSM-5 zeolite onto a cordierite monolith, then subliming an iron salt onto the zeolite, calcining the monolith, and then dipping the monolith either into an aqueous solution of manganese nitrate and cerium nitrate and then calcining, or by similar treatment with separate solutions of manganese nitrate and cerium nitrate. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).

  4. Cerium relieves the inhibition of nitrogen metabolism of spinach caused by magnesium deficiency.

    PubMed

    Yin, Sitao; Ze, Yuguan; Liu, Chao; Li, Na; Zhou, Min; Duan, Yanmei; Hong, Fashui

    2009-12-01

    Magnesium is one of the essential elements for plant growth and cerium is a beneficial element for plant growth. However, the effects of the fact that cerium improves the nitrogen metabolism of plants under magnesium deficiency is poorly understood. The main aim of the study was to determine the role of cerium in the amelioration of magnesium-deficiency effects in spinach plants. Spinach plants were cultivated in Hoagland's solution. They were subjected to magnesium deficiency and to cerium chloride administered in the magnesium-present media and magnesium-deficient media. Spinach plants grown in the magnesium-present media and magnesium-deficient media were measured for key enzyme activities involved in nitrogen metabolism such as nitrate reductase, nitrite reductase, glutamate dehydrogenase, glutamate synthase, urease, glutamic–pyruvic transaminase, and glutamic–oxaloace protease transaminase. As the nitrogen metabolism in spinach was significantly inhibited by magnesium deficiency, it caused a significant reduction of spinach plant weight, leaf turning chlorosis. However, cerium treatment grown in magnesium-deficiency media significantly promoted the activities of the key enzymes as well as the contents of the free amino acids, chlorophyll, soluble protein, and spinach growth. It implied that Ce3+ could partly substitute for magnesium to facilitate the transformation from inorganic nitrogen to organic nitrogen, leading to the improvement of spinach growth, although the metabolism needs to be investigated further.

  5. Influences of calcium deficiency and cerium on growth of spinach plants.

    PubMed

    Chao, Liu; Bofu, Pan; Weiqian, Cao; Yun, Lu; Hao, Huang; Liang, Chen; Xiaoqing, Liu; Xiao, Wu; Fashui, Hong

    2008-03-01

    The main aim of the study was to determine the role of cerium in the amelioration of calcium-deficiency effects in spinach plants. Spinach plants were cultivated in Hoagland's solution. They were subjected to calcium-deficiency and to cerium chloride administered in the calcium-present Hoagland's media and calcium-deficient Hoagland's media. Within 3 weeks, young leaves developed distinct calcium-deficient symptoms, and plant growth significantly inhibited to calcium deprivation as would be expected; cerium-treated groups grown in the same conditions did not develop calcium-deficient symptoms; fresh weight, dry weight and chlorophyll content of spinach plants were increased by 35.9, 45 and 64.05% compared to those of plants cultivated in calcium-deficient media. In addition, calcium deprivation in spinach plants caused the reduction of photosynthetic rate, oxygen evolution rate and ribulose-1,5-bisphosphate carboxylase/oxygenase activity. The reduction of activities of nitrate reductase, glutamate dehydrogenase, glutamate synthase and glutamic-pyruvic transaminase was observed under calcium-deficient media. However, cerium treatment under calcium-deficient media could significantly improve photosynthesis and nitrogen metabolism of spinach plants. This is viewed as evidence that cerium added to calcium-deficient media in the spinach plants could substitute for calcium and improve spinach growth.

  6. [Characterization and analysis of direction extraction and precipitation of cerium loading organic phase by oxalic acid solution].

    PubMed

    Mei, Yan; Xia, Chuan; Chen, Xiao-Li; Sun, He; Nie, Zuo-Ren

    2011-11-01

    In the condition of sodium hydroxide saponification, the test results using direction extraction and precipitation of cerium from P507 loading organic phase by oxalic acid solution were studied. Infared (IR) spectrum, X-ray diffraction (XRD), transmission electron microscope (TEM) and thermogravimetry (TG-DSC) were used to study and characterize organic cerium precipitates and the final calcined products. The results showed that organic cerium precipitates and final calcined products were spheric organic cerium coordination and spheric cube CeO2 crystal, respectively, showing their morphologies were successive. IR made out that the structures of organic cerium precipitates and final calcined products were different. TG-DSC indicated that the final calcined products weightlessness was 3.5% and chemical composing was CeO2 x 1/3H2O.

  7. Intravenous and Gastric Cerium Dioxide Nanoparticle Exposure Disrupts Microvascular Smooth Muscle Signaling

    PubMed Central

    Minarchick, Valerie C.; Stapleton, Phoebe A.; Fix, Natalie R.; Leonard, Stephen S.; Sabolsky, Edward M.; Nurkiewicz, Timothy R.

    2015-01-01

    Cerium dioxide nanoparticles (CeO2 NP) hold great therapeutic potential, but the in vivo effects of non-pulmonary exposure routes are unclear. The first aim was to determine whether microvascular function is impaired after intravenous and gastric CeO2 NP exposure. The second aim was to investigate the mechanism(s) of action underlying microvascular dysfunction following CeO2 NP exposure. Rats were exposed to CeO2 NP (primary diameter: 4 ± 1 nm, surface area: 81.36 m2/g) by intratracheal instillation, intravenous injection, or gastric gavage. Mesenteric arterioles were harvested 24 h post-exposure and vascular function was assessed using an isolated arteriole preparation. Endothelium-dependent and independent function and vascular smooth muscle (VSM) signaling (soluble guanylyl cyclase [sGC] and cyclic guanosine monophosphate [cGMP]) were assessed. Reactive oxygen species (ROS) generation and nitric oxide (NO) production were analyzed. Compared with controls, endothelium-dependent and independent dilation were impaired following intravenous injection (by 61% and 45%) and gastric gavage (by 63% and 49%). However, intravenous injection resulted in greater microvascular impairment (16% and 35%) compared with gastric gavage at an identical dose (100 µg). Furthermore, sGC activation and cGMP responsiveness were impaired following pulmonary, intravenous, and gastric CeO2 NP treatment. Finally, nanoparticle exposure resulted in route-dependent, increased ROS generation and decreased NO production. These results indicate that CeO2 NP exposure route differentially impairs microvascular function, which may be mechanistically linked to decreased NO production and subsequent VSM signaling. Fully understanding the mechanisms behind CeO2 NP in vivo effects is a critical step in the continued therapeutic development of this nanoparticle. PMID:25481005

  8. Intravenous and gastric cerium dioxide nanoparticle exposure disrupts microvascular smooth muscle signaling.

    PubMed

    Minarchick, Valerie C; Stapleton, Phoebe A; Fix, Natalie R; Leonard, Stephen S; Sabolsky, Edward M; Nurkiewicz, Timothy R

    2015-03-01

    Cerium dioxide nanoparticles (CeO2 NP) hold great therapeutic potential, but the in vivo effects of non-pulmonary exposure routes are unclear. The first aim was to determine whether microvascular function is impaired after intravenous and gastric CeO2 NP exposure. The second aim was to investigate the mechanism(s) of action underlying microvascular dysfunction following CeO2 NP exposure. Rats were exposed to CeO2 NP (primary diameter: 4 ± 1 nm, surface area: 81.36 m(2)/g) by intratracheal instillation, intravenous injection, or gastric gavage. Mesenteric arterioles were harvested 24 h post-exposure and vascular function was assessed using an isolated arteriole preparation. Endothelium-dependent and independent function and vascular smooth muscle (VSM) signaling (soluble guanylyl cyclase [sGC] and cyclic guanosine monophosphate [cGMP]) were assessed. Reactive oxygen species (ROS) generation and nitric oxide (NO) production were analyzed. Compared with controls, endothelium-dependent and independent dilation were impaired following intravenous injection (by 61% and 45%) and gastric gavage (by 63% and 49%). However, intravenous injection resulted in greater microvascular impairment (16% and 35%) compared with gastric gavage at an identical dose (100 µg). Furthermore, sGC activation and cGMP responsiveness were impaired following pulmonary, intravenous, and gastric CeO2 NP treatment. Finally, nanoparticle exposure resulted in route-dependent, increased ROS generation and decreased NO production. These results indicate that CeO2 NP exposure route differentially impairs microvascular function, which may be mechanistically linked to decreased NO production and subsequent VSM signaling. Fully understanding the mechanisms behind CeO2 NP in vivo effects is a critical step in the continued therapeutic development of this nanoparticle.

  9. Pulmonary Cerium Dioxide Nanoparticles Exposure Differentially Impairs Coronary and Mesenteric Arteriolar Reactivity

    PubMed Central

    Minarchick, Valerie C; Stapleton, Phoebe A; Porter, Dale W; Wolfarth, Michael G; Çiftyürek, Engin; Barger, Mark; Sabolsky, Edward M.; Nurkiewicz, Timothy R

    2013-01-01

    Cerium dioxide nanoparticles (CeO2 NPs) are an engineered nanomaterial that possesses unique catalytic, oxidative and reductive properties. Currently, CeO2 NPs are being used as a fuel catalyst but these properties are also utilized in the development of potential drug treatments for radiation and stroke protection. These uses of CeO2 NPs present a risk for human exposure; however, to date no studies have investigated the effects of CeO2 NPs on the microcirculation following pulmonary exposure. Previous studies in our laboratory with other nanomaterials have shown impairments in normal microvascular function after pulmonary exposures. Therefore, we predicted that CeO2 NP exposure would cause microvascular dysfunction that is dependent on the tissue bed and dose. Twenty-four hour post exposure to CeO2 NPs (0–400 μg), mesenteric and coronary arterioles were isolated and microvascular function was assessed. Our results provided evidence that pulmonary CeO2 NP exposure impairs endothelium-dependent and -independent arteriolar dilation in a dose-dependent manner. The CeO2 NP exposure dose which causes a 50% impairment in arteriolar function (EC50) was calculated and ranged from 15 – 100 μg depending on the chemical agonist and microvascular bed. Microvascular assessments with acetylcholine revealed a 33–75% reduction in function following exposure. Additionally, there was a greater sensitivity to CeO2 NP exposure in the mesenteric microvasculature due to the 40% decrease in the calculated EC50 compared to the coronary microvasculature EC50. CeO2 NP exposure increased mean arterial pressure in some groups. Taken together these observed microvascular changes may likely have detrimental effects on local blood flow regulation and contribute to cardiovascular dysfunction associated with particle exposure. PMID:23645470

  10. Correlation of cerium anomalies with indicators of paleoenvironment

    SciTech Connect

    MacLeod, K.G.; Irving, A.J.

    1996-09-01

    Among 21 whole-rock samples of the Upper Cretaceous Niobrara Formation from Colorado, the abundance of cerium relative to other rate earth elements (Ce anomaly), the weight percent organic carbon (%C{sub org}), and the intensity of bioturbation all covary. This covariation is provocative because %C{sub org} and intensity of bioturbation track changes in the concentration of oxygen in the local water column at the time of deposition (Savrda and Bottjer 1989). Ce anomalies in apatite-rich fractions of the Maastrichtian Zumaya-Algorta Formation from France and Spain and the Miocene Monterey Formation from California show changes that also may coincide with changes in ancient oxygen levels. Results for the Niobrara samples are the closest correspondence demonstrated between paleo-redox conditions and Ce anomalies, but the authors cannot yet determine whether the correspondence reflects a cause-and-effect relationship. Variation in Ce anomalies is influenced by a number of factors, including terrigenous input, depositional environment, and diagenetic conditions. Potential interplay of these factors prevents a unique interpretation of the whole-rock data; dissecting whole-rock Ce anomalies through analysis of isolated sedimentary components, though, is a promising avenue of research.

  11. Denaturation of Human Serum Albumin by Cerium (iii) Chloride

    NASA Astrophysics Data System (ADS)

    Behbahani, G. Rezaei; Shalbafan, M.; Gheibi, N.; Barzegar, L.; Behbahani, H. Rezaei; Yaghdavaei, N.; Behbahani, Z. Rezaei

    2013-08-01

    Cerium (III) Chloride-induced conformational changes of human serum albumin, HSA, in phosphate buffer, 10 mM at pH 7.4 was investigated, using isothermal titration calorimetry (ITC), UV and fluorescence emission spectroscopic methods. The results indicate that CeCl3, Ce3+, induces irreversible denaturation of the HSA structure. The UV absorption intensity of HSA + Ce3+ shows a slight blueshift in the absorbance wavelength with increasing Ce3+ concentration. The fluorescence intensity was increased regularly and a slight redshift was observed in the emission wavelength. The HSA + Ce3+ complex quenches the fluorescence of HSA and changes the microenvironment of tryptophan residue. The emission intensity increases suggesting the loss of the tertiary structure of HSA. The results obtained from the ITC data are in agreement with the spectroscopic methods. The strong negative cooperativity of Ce3+ binding with HSA (Table 1) recovered from the extended solvation model, indicates that HSA has been denatured as a result of its interaction with Ce3+ ions.

  12. Cerium dioxide nanoparticles increase immunogenicity of the influenza vaccine.

    PubMed

    Zholobak, Nadezhda M; Mironenko, Alla P; Shcherbakov, Alexander B; Shydlovska, Olga A; Spivak, Mykola Ya; Radchenko, Larysa V; Marinin, Andrey I; Ivanova, Olga S; Baranchikov, Alexander E; Ivanov, Vladimir K

    2016-03-01

    We have demonstrated the influence of cerium dioxide nanoparticles on the immunogenicity of the influenza vaccine on an example of liquid split inactivated Vaxigrip vaccine. Antibody titers were analyzed using the hemagglutination inhibition (HI) assay. Seroprotection, seroconversion, the geometric mean titers (GMTs) and the factor increase (FI) in the GMTs were calculated. The effect of nano-ceria surface stabilizer on the enhancement of immunogenicity was shown. The vaccine modified by citrate-stabilized nano-ceria, in contrast to a non-modified Vaxigrip vaccine, did not provide an adequate level of seroprotection, and seroconversion after vaccination was 66.7% on days 49-63 for virus strain А(H1N1) and 100% on day 49 for virus strain B/Yamagata. For the low immunogenic influenza B virus, the rise in antibody titers (GMT/IF) was 24.38/3.28 after the first injection and 50.40/6.79 on day 49. For the vaccine modified by non-stabilized nano-ceria, for all virus strains under study, on day 63, upon immunization notable levels of seroprotection, seroconversion and GMT/IF were registered (higher than for the non-modified Vaxigrip vaccine). The successful attempt to modify the influenza vaccine demonstrates the possible ways of increasing the specific activity of vaccines using nano-ceria.

  13. Cerium negatively impacts the nutritional status in rapeseed.

    PubMed

    Pošćić, Filip; Schat, Henk; Marchiol, Luca

    2017-03-29

    Cerium (Ce) has been reported to be both beneficial and harmful to plants. This contradiction deserves explanation in the light of increased anthropogenic release of Ce in the environment. Ce tolerance and accumulation were evaluated in hydroponically cultivated Brassica napus L. (rapeseed). Ce and other nutrient concentrations were measured with increasing Ce concentration in the nutrient solution. Moreover, Ce and calcium (Ca) accumulation were evaluated at different Ca and Ce concentrations in nutrient solution and a Michaelis-Menten type inhibition model considering Ce and Ca competition was tested. Plants were also sprayed with Ce solution in Ca-deficient media. Ce decreased the growth and root function, which affected shoot nutritional status. Calcium was the most severely inhibited nutrient in both roots and shoots. High Ca concentrations in the nutrient solution inhibited Ce accumulation in a non-competitive way. Moreover, phosphorus (P) precipitated Ce inside root cells. Ce spraying did not alleviate Ca deficiency symptoms and the results were critically compared to the available literature.

  14. Synthesis and photocatalytic activity of mesoporous cerium doped TiO{sub 2} as visible light sensitive photocatalyst

    SciTech Connect

    Aman, Noor; Satapathy, P.K.; Mishra, T.; Mahato, M.; Das, N.N.

    2012-02-15

    Graphical abstract: Cerium doped titania having optimum 5 wt% of cerium can decompose methylene blue and reduce selenium (IV) efficiently under visible light. Highlights: Black-Right-Pointing-Pointer Effect of cerium doping on the surface properties and visible light mediated photocatalytic reaction is studied. Black-Right-Pointing-Pointer Cerium doping increases the anatase phase stability, surface area (up to 137 m{sup 2}/g) and visible light absorption. Black-Right-Pointing-Pointer Importance of Ce{sup 3+}/Ce{sup 4+}, oxygen vacancy, surface area and crystallinity is correlated with improved catalytic activity. Black-Right-Pointing-Pointer Material with 5 wt% Ce is found to be most active photocatalyst for methylene blue decomposition and Se (IV) reduction. -- Abstract: Cerium doped titania materials were synthesized varying the cerium concentration from 0 to 10 wt%. Materials are characterised by XRD, TEM, XPS and N{sub 2} adsorption desorption method. Surface area and visible light absorption substantially increases and crystallite size decreases with the increasing cerium content. Cerium doping stabilizes the anatase phase and surface area even at 600 Degree-Sign C calcination. Photocatalytic activity towards methylene blue decomposition and selenium (IV) reduction is found to increase with the cerium content up to 5 wt% and then decreases. Materials calcined at 600 Degree-Sign C shows better activity than that calcined at 400 Degree-Sign C, even though surface area decreases. Anatase crystallinity mostly decides the photocatalytic activity rather than only surface area. It can be concluded that the optimum visible light absorption and oxygen vacancy with 5% cerium doping enhances the photocatalytic activity. In addition photocatalytic performance is found to depend on the presence of Ce{sup 4+}/Ce{sup 3+} rather than only visible light absorption.

  15. Excitation induced spectroscopic study and quenching effect in cerium samarium codoped lithium aluminoborate glasses

    NASA Astrophysics Data System (ADS)

    Kaur, Parvinder; Kaur, Simranpreet; Singh, Gurinder Pal; Arora, Deepawali; Kumar, Sunil; Singh, D. P.

    2016-08-01

    Lithium aluminium borate host has been codoped with cerium and samarium to prepare glass by conventional melt quench technique. Their structural and spectroscopic investigation has been carried out using XRD, FTIR and density measurements. The UV-Vis absorption spectra and fluorescence spectra (λexc.=380 nm and 400 nm) have been studied for spectroscopic analysis. The amorphous nature of the prepared samples is shown by XRD. The density is increasing with addition of cerium at the expense of aluminium, keeping other components constant. FTIR study also shows the presence of compact and stable tetrahedral BO4 units thus supporting the density results. The UV- Vis absorption spectra show a shift of optical absorption edge towards longer wavelength along with an increase in intensity of peaks with rising samarium concentration. The fluorescence spectra show a blue shift and subsequent suppression of cerium peaks with addition of samarium.

  16. Eucalyptus tolerance mechanisms to lanthanum and cerium: subcellular distribution, antioxidant system and thiol pools.

    PubMed

    Shen, Yichang; Zhang, Shirong; Li, Sen; Xu, Xiaoxun; Jia, Yongxia; Gong, Guoshu

    2014-12-01

    Guanglin 9 (Eucalyptus grandis × Eucalyptus urophlla) and Eucalyptus grandis 5 are two eucalyptus species which have been found to grow normally in soils contaminated with lanthanum and cerium, but the tolerance mechanisms are not clear yet. In this study, a pot experiment was conducted to investigate the tolerance mechanisms of the eucalyptus to lanthanum and cerium. Cell walls stored 45.40-63.44% of the metals under lanthanum or cerium stress. Peroxidase and catalase activities enhanced with increasing soil La or Ce concentrations up to 200 mg kg(-1), while there were no obvious changes in glutathione and ascorbate concentrations. Non-protein thiols concentrations increased with increasing treatment levels up to 200 mg kg(-1), and then decreased. Phytochelatins concentrations continued to increase under La or Ce stress. Therefore, the two eucalyptus species are La and Ce tolerant plants, and the tolerance mechanisms include cell wall deposition, antioxidant system response, and thiol compound synthesis.

  17. The role of chemical interactions between thorium, cerium, and lanthanum in lymphocyte toxicity.

    PubMed

    Oliveira, Monica S; Duarte, Isabelle M; Paiva, Amanda V; Yunes, Samira N; Almeida, Carlos E; Mattos, Rita C; Sarcinelli, Paula N

    2014-01-01

    Thorium, cerium, and lanthanum are metals present in several types of minerals, the most common of which is monazite. Cerium and lanthanum are elements in the lanthanides series. Thorium, an actinide metal, is a hazardous element due to its radioactive characteristics. There is a lack of information describing the possible chemical interactions among these elements and the effects they may have on humans. Toxicological analyses were performed using cell viability, cell death, and DNA damage assays. Chemical interactions were evaluated based on the Loewe additivity model. The results indicate that thorium and cerium individually have no toxic effects on lymphocytes. However, thorium associated with lanthanum increases the toxicity of this element, thereby reducing the viability of lymphocytes at low concentrations of metals in the mixture.

  18. Cytotoxic activity of new cerium (III) complexes of bis-coumarins.

    PubMed

    Kostova, Irena; Manolov, Ilia; Momekov, Georgi; Tzanova, Tzvetomira; Konstantinov, Spiro; Karaivanova, Margarita

    2005-12-01

    Complexes of cerium (III) with bis-coumarins: 3,3'-benzylidene-bis(4-hydroxy-2H-1-benzopyran-2-one) and bis(4-hydroxy-2-oxo-2H-chromen-3-yl)-(1H-pyrazol-3-yl)-methane were synthesized by reaction of cerium (III) salt and the ligands, in amounts equal to metal/ligand molar ratio of 1:2. The complexes were prepared by adding an aqueous solution of cerium (III) salt to an aqueous solution of the ligand subsequently raising the pH of the mixture gradually to ca. 5.0 by adding dilute solution of sodium hydroxide. The cerium (III) complexes with bis-coumarins were characterized by different physicochemical methods--elemental analysis, IR-, 1H- and 13C-NMR-spectroscopies and mass-spectral data. The spectral data of cerium (III) complexes were interpreted on the basis of comparison with the spectra of the free ligands. This analysis showed that in the Ce (III) complexes the ligands coordinated to the metal ion through both deprotonated hydroxyl groups. On the basis of the nu(C=O) red shift observed, participation of the carbonyl groups in the coordination to the metal ion was also suggested. Cytotoxic screening by MTT assay was carried out. In the present study we performed comparative evaluation of the cytotoxic effects of the two newly synthesized cerium complexes against the acute myeloid leukemia derived HL-60 and the chronic myeloid leukemia (CML)-derived BV-173. In addition the cytotoxic effects of Ce (III) complex with 3,3'-benzylidene-bis(4-hydroxy-2H-1-benzopyran-2-one) were evaluated on the CML-derived K-562 and LAMA-84 cells, characterized by relative low responsiveness to chemotherapy. The DNA isolated from the cytosolic fraction of BV-173 cells after 24 h treatment with the same complex (at 100 and 200 microM) demonstrated a laddering phenomenon that is indicative for apoptotic cell death.

  19. Incidence of methemoglobinemia in patients receiving cerium nitrate and silver sulfadiazine for the treatment of burn wounds: a burn center's experience.

    PubMed

    Kath, Melissa A; Shupp, Jeffrey W; Matt, Sarah E; Shaw, Jesse D; Johnson, Laura S; Pavlovich, Anna R; Brant, Jennifer D; Mete, Mihriye; Jeng, James C; Jordan, Marion H

    2011-01-01

    In 1976, the combination of cerium nitrate and silver sulfadiazine was introduced as a topical therapy for burn wounds. Experience with a locally prepared combination agent has shown physical change of the eschar and delayed subeschar bacterial colonization. A potential systemic complication of this treatment is the development of methemoglobinemia (Met-Hba) due to the oxidizing nature of Ce(NO(3))(3). Met-Hba has a spectrum of clinical consequences, ranging from headache and cyanosis to cardiac ischemia, hypotension, and even death. Given the frequent use of this combination agent at our burn center, a retrospective review was conducted to evaluate the incidence of Met-Hba. A query of pharmacy records revealed 170 patients from January 2005 to October 2009 that had received this treatment. Eighteen patients (∼10%) developed Met-Hba as noted on arterial blood gas (methemoglobin>3%) and only three patients (∼2%) had methemoglobin levels >10%. In the majority of cases, there were no clinical symptoms of Met-Hba. Most patients' relative hypoxia resolved with cessation of treatment; however, five patients required treatment with methylene blue. The presence of Met-Hba associated with this topical therapy can be diagnosed early by vigilant monitoring, thereby reducing morbidity and mortality. In our experience, cerium combined with silver sulfadiazine is a valuable and safe treatment for deep partial and full-thickness burn wounds.

  20. Protection by Thermal and Chemical Activation with Cerium Salts of the Alloy AA2017 in Aqueous Solutions of NaCl

    NASA Astrophysics Data System (ADS)

    Bethencourt, Manuel; Botana, Francisco Javier; Cano, María José; González-Rovira, Leandro; Marcos, Mariano; Sánchez-Amaya, José María

    2012-01-01

    A wide variety of anticorrosive treatments for aluminum alloys that can be employed as "green" alternatives to those based on Cr(VI) are currently under development. This article reports a study of the morphological and anticorrosive characteristics of surface layers formed on the Al-Cu alloy AA2017 by immersion treatment in baths of cerium salt, accelerated by increased temperature and the employment of hydrogen peroxide. Scanning electron microscopy (SEM)/X-ray energy dispersive spectroscopy (XEDS) studies of the samples treated have demonstrated the existence of a heterogeneous layer formed by a film of aluminum oxide/hydroxide on the matrix, and a series of dispersed islands of cerium over the cathodic intermetallics. The protective efficacy has been evaluated using electrochemical techniques, linear polarizations (LP) and electrochemical impedance spectroscopy (EIS), and salt spray tests. The results obtained indicate that the layer provided good resistance to corrosion in media with chlorides, and the method gives a considerable reduction of the time required for the immersion treatments.

  1. Stabilization of 238Pu-contaminated combustible waste by molten salt oxidation

    NASA Astrophysics Data System (ADS)

    Stimmel, Jay J.; Remerowski, Mary Lynn; Ramsey, Kevin B.; Heslop, J. Mark

    2000-07-01

    Surrogate studies were conducted using the molten salt oxidation system at the Naval Surface Warfare Center-Indian Head Division. This system uses a rotary feed system and an alumina molten salt oxidation vessel. The combustible materials were tested individually and together in a homogenized mixture. A slurry containing pyrolyzed cheesecloth ash spiked with cerium oxide, which is used as a surrogate for plutonium, and ethylene glycol were also treated in the molten salt oxidation vessel.

  2. Systematic variation of rare-earth elements in cerium-earth minerals

    USGS Publications Warehouse

    Murata, K.J.; Rose, H.J.; Carron, M.K.; Glass, J.J.

    1957-01-01

    In a continuation of a study reported previously, rare-earth elements and thorium have been determined in monazite, allanite, cerite, bastnaesite, and a number of miscellaneous cerium-earth minerals. A quantity called sigma (???), which is the sum of the atomic percentages of La, Ce, and Pr, is proposed as an index of composition of all cerium-earth minerals with respect to the rare-earth elements. The value of ??? for all of the minerals analysed falls between 58 and 92 atomic per cent. Monazites, allanites, and cerites cover the entire observed range, whereas bastnaesites are sharply restricted to the range between 80 and 92 atomic per cent. The minimum value of ??? for a cerium-earth mineral corresponds to the smallest possible unit-cell size of the mineral. In monazite, this structurally controlled minimum value of ??? is estimated to be around 30 atomic per cent. Neodymium, because of its abundance, and yttrium, because of its small size, have dominant roles in contraction of the structure. In the other direction, the limit of variation in composition will be reached when lanthanum becomes the sole rare-earth element in a cerium-earth mineral. Cerium-earth minerals from alkalic rocks are all characterized by values of ??? greater than 80 atomic per cent, indicating that the processes that formed these rocks were unusually efficient in fractionating the rare-earth elements-efficient in the sense that a highly selected assemblage is produced without eliminating the bulk of these elements. Analyses of inner and outer parts of two large crystals of monazite from different deposits show no difference in ??? in one crystal and a slightly smaller value of ??? in the outer part of the other crystal compared to the inner part. The ??? of monazites from pegmatites that intrude genetically related granitic rocks in North Carolina is found to be either higher or lower than the ??? of monazites in the intruded host rock. These results indicate that the fractionation of the

  3. Synthesis and characterization of two dimensional metal organic framework of cerium with tetraaza macrocyclic

    SciTech Connect

    Bt Safiin, Nurul Atikah; Yarmo, Ambar; Yamin, Bohari M.

    2013-11-27

    A two dimensional metal organic framework containing cerium sufate layers and ethylenediaminium between layers was obtained by refluxing the mixture of cerium sulphate and 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-7, 14-diene bromide. The complex was characterized by infrared spectroscopy and microelemental analysis. X-ray study showed that the complex adopts eleven coordination environments about the central atom. Thermogravimetric study showed the removal of water molecules at about 70°C followed by a gradual mass loss until the whole structure collapsed at about 400°C.

  4. Behavior of cerium in boundary segregation and temper embrittlement of steels

    SciTech Connect

    Yuan, Z.; Li, J.; Feng, S.

    1986-01-01

    The co-segregation of manganese and phosphorus causes temper embrittlement. As the tempering is prolonged, the concentration of manganese in (Fe,Mn)/sub 3/C increases. It upsets the equilibrium of co-segregation and, in turn, reduces the degree of co-segregation of manganese and phosphorus, thus lessening the increase in FATT 50%. Cerium reduces the amounts of phosphorus and manganese segregated to the grain boundaries. As the grain-boundary concentration of cerium increases unceasingly, the resistance against co-segregation increases and the rate of embrittling decreases.

  5. METHOD OF SEPARATING TETRAVALENT PLUTONIUM VALUES FROM CERIUM SUB-GROUP RARE EARTH VALUES

    DOEpatents

    Duffield, R.B.; Stoughton, R.W.

    1959-02-01

    A method is presented for separating plutonium from the cerium sub-group of rare earths when both are present in an aqueous solution. The method consists in adding an excess of alkali metal carbonate to the solution, which causes the formation of a soluble plutonium carbonate precipitate and at the same time forms an insoluble cerium-group rare earth carbonate. The pH value must be adjusted to bctween 5.5 and 7.5, and prior to the precipitation step the plutonium must be reduced to the tetravalent state since only tetravalent plutonium will form the soluble carbonate complex.

  6. Treatment of Radioactive Organic Wastes by an Electrochemical Oxidation

    SciTech Connect

    Kim, K.H.; Ryue, Y.G.; Kwak, K.K.; Hong, K.P.; Kim, D.H.

    2007-07-01

    A waste treatment system by using an electrochemical oxidation (MEO, Mediated Electrochemical Oxidation) was installed at KAERI (Korea Atomic Energy Research Institute) for the treatment of radioactive organic wastes, especially EDTA (Ethylene Diamine Tetraacetic Acid) generated during the decontamination activity of nuclear installations. A cerium and silver mediated electrochemical oxidation technique method has been developed as an alternative for an incineration process. An experiment to evaluate the applicability of the above two processes and to establish the conditions to operate the pilot-scale system has been carried out by changing the concentration of the catalyst and EDTA, the operational current density, the operating temperature, and the electrolyte concentration. As for the results, silver mediated oxidation was more effective in destructing the EDTA wastes than the cerium mediated oxidation process. For a constant volume of the EDTA wastes, the treatment time for the cerium-mediated oxidation was 9 hours and its conversion ratio of EDTA to water and CO{sub 2} was 90.2 % at 80 deg. C, 10 A, but the treatment time for the silver-mediated oxidation was 3 hours and its conversion ratio was 89.2 % at 30 deg. C, 10 A. (authors)

  7. Fate of cerium dioxide nanoparticles in endothelial cells: exocytosis

    NASA Astrophysics Data System (ADS)

    Strobel, Claudia; Oehring, Hartmut; Herrmann, Rudolf; Förster, Martin; Reller, Armin; Hilger, Ingrid

    2015-05-01

    Although cytotoxicity and endocytosis of nanoparticles have been the subject of numerous studies, investigations regarding exocytosis as an important mechanism to reduce intracellular nanoparticle accumulation are rather rare and there is a distinct lack of knowledge. The current study investigated the behavior of human microvascular endothelial cells to exocytose cerium dioxide (CeO2) nanoparticles (18.8 nm) by utilization of specific inhibitors [brefeldin A; nocodazole; methyl-β-cyclodextrin (MβcD)] and different analytical methods (flow cytometry, transmission electron microscopy, inductively coupled plasma mass spectrometry). Overall, it was found that endothelial cells were able to release CeO2 nanoparticles via exocytosis after the migration of nanoparticle containing endosomes toward the plasma membrane. The exocytosis process occurred mainly by fusion of vesicular membranes with plasma membrane resulting in the discharge of vesicular content to extracellular environment. Nevertheless, it seems to be likely that nanoparticles present in the cytosol could leave the cells in a direct manner. MβcD treatment led to the strongest inhibition of the nanoparticle exocytosis indicating a significant role of the plasma membrane cholesterol content in the exocytosis process. Brefeldin A (inhibitor of Golgi-to-cell-surface-transport) caused a higher inhibitory effect on exocytosis than nocodazole (inhibitor of microtubules). Thus, the transfer from distal Golgi compartments to the cell surface influenced the exocytosis process of the CeO2 nanoparticles more than the microtubule-associated transport. In conclusion, endothelial cells, which came in contact with nanoparticles, e.g., after intravenously applied nano-based drugs, can regulate their intracellular nanoparticle amount, which is necessary to avoid adverse nanoparticle effects on cells.

  8. Degradation of nitrobenzene using titania photocatalyst co-doped with nitrogen and cerium under visible light illumination.

    PubMed

    Shen, Xiang-Zhong; Liu, Zhi-Cheng; Xie, Shan-Mei; Guo, Jun

    2009-03-15

    A type of nitrogen and cerium co-doped titania photocatalyst, which could degrade nitrobenzene under visible light irradiation, was prepared by the sol-gel route. Titanium isopropoxide, ammonium nitrate, and cerium nitrate were used as the sources of titanium, nitrogen, and cerium, respectively. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffusive reflectance spectroscopy (DRS), scanning electron microscopy (SEM), and N(2) adsorption-desorption isotherm were employed to characterize the as-prepared photocatalyst. The degradation of nitrobenzene under visible light illumination was taken as probe reaction to evaluate the photoactivity of the co-doped photocatalyst. The commercial TiO(2) photocatalyst (Degussa P25), which was thought as a high active photocatalyst, was chosen as standard photocatalyst to contrast the photoactivity of the nitrogen and cerium co-doped titania photocatalyst. The results showed that the photocatalytic performance of the nitrogen and cerium co-doped titania was related with the calcination temperature and the component. The nitrogen atoms were incorporated into the crystal of titania and could narrow the band gap energy. The doping cerium atoms existed in the forms of Ce(2)O(3) and dispersed on the surface of TiO(2). The improvement of the photocatalytic activity was ascribed to the synergistic effects of the nitrogen and cerium co-doping.

  9. Particulate Emissions from the Combustion of Diesel Fuel with a Fuel-Borne Nanoparticulate Cerium Catalyst

    NASA Astrophysics Data System (ADS)

    Conny, J. M.; Willis, R. D.; Weinstein, J. P.; Krantz, T.; King, C.

    2013-12-01

    To address the adverse impacts on health and climate from the use of diesel-fueled vehicles, a number of technological solutions have been developed for reducing diesel soot emissions and to improve fuel economy. One such solution is the use fuel-borne metal oxide catalysts. Of current interest are commercially-available fuel additives consisting of nanoparticulate cerium oxide (CeO2). In response to the possible use of CeO2-containing fuels in on-road vehicles in the U.S., the Environmental Protection Agency is conducting research to address the potential toxicity and environmental effects of particulate CeO2 emitted with diesel soot. In this study, emissions from a diesel-fueled electric generator were size-segregated on polished silicon wafers in a nanoparticle cascade impactor. The diesel fuel contained 10 ppm Ce by weight in the form of crystalline CeO2 nanoparticles 4 nm to 7.5 nm in size. Primary CeO2 nanoparticles were observed in the diesel emissions as well as CeO2 aggregates encompassing a broad range of sizes up to at least 200 nm. We report the characterization of individual particles from the size-resolved samples with focused ion-beam scanning electron microscopy and energy-dispersive x-ray spectroscopy. Results show a dependency between the impactor size range and CeO2 agglomeration state: in the larger size fractions of the impactor (e.g., 560 nm to 1000 nm) CeO2 nanoparticles were predominantly attached to soot particles. In the smaller size fractions of the impactor (e.g., 100 nm to 320 nm), CeO2 aggregates tended to be larger and unattached to soot. The result is important because the deposition of CeO2 nanoparticles attached to soot particles in the lung or on environmental surfaces such as plant tissue will likely present different consequences than the deposition of unagglomerated CeO2 particles. Disclaimer The U.S. Environmental Protection Agency through its Office of Research and Development funded and collaborated in the research described

  10. Cerium Anomalies in Fossil Fish Teeth Reveal Changes in Bottom Water Oxygenation

    NASA Astrophysics Data System (ADS)

    Chun, C. O.; Scher, H. D.; Delaney, M. L.

    2007-12-01

    Shale-normalized rare earths and yttrium (REY) concentrations of fossil fish teeth in deep sea sediments display prominent negative cerium (Ce) anomalies and positive yttrium (Y) anomalies. These features are ultimately inherited from seawater and strongly indicate that fossil fish teeth preserve a seawater REY signature. In seawater, Ce+3 is oxidized to Ce+4, and Ce becomes depleted relative to the other REY's as it partitions into other phases (e.g., ferromanganese oxyhydroxides). The magnitude of Ce depletion in a water mass is thus related to its oxygen content. We hypothesize that changes in the oxygenation of bottom waters may be revealed by examining downcore variability in the magnitude of the Ce anomaly of fossil fish teeth. To test this hypothesis, REY concentrations were measured on samples of cleaned fossil fish teeth recovered from the late Paleogene to early Eocene sections of Ocean Drilling Program (ODP) Sites 1262 and 1263 (lower and upper Walvis Ridge, ODP Leg 208, South Atlantic Ocean). These sites are vertically offset (early Eocene paleodepths were 3700 and 1700 meters, respectively) and have been extensively studied to characterize the oceanic response to the Paleocene/Eocene Thermal Maximum (PETM). Manganese enrichment factors (Mn EF) determined from total digestions of samples from these sites reveal abrupt changes in the oxygenation of bottom waters across the PETM interval. Mn EF's decrease to crustal values (~1) during the PETM, which reflects the reduction of Mn oxides as bottom water oxygen levels were depleted. Mn EF's begin to increase to 6-8 during the 'recovery phase' following the PETM. The Ce anomaly for these samples, Ce/Ce*, was calculated according to the geometric approach reported by Lawrence et al. (2006, Aquatic Geochemistry 12, 39-72), where Ce* represents an interpolation of the expected shale-normalized Ce concentration from near neighbors. In this notation, when Ce/Ce* = 1 no Ce anomaly is present. At upper Walvis Ridge

  11. Resonant photoemission study of the 4f spectral function of cerium in Ce/Fe(100) interfaces

    SciTech Connect

    Witkowski, N.; Bertran, F.; Gourieux, T.; Kierren, B.; Malterre, D.; Panaccione, G. |

    1997-11-01

    In this paper, we present a resonant photoemission study of the cerium 4f spectral function in Ce/Fe(100) interfaces. By covering cerium ultrathin films with lanthanum, we completely suppress the surface contribution of the spectra. Then we show that the cerium atoms at the interface are in an intermediate valent state, whereas the f{sup 1} configuration is stabilized in the top layer. This method allows us to obtain the genuine 4f spectral function of the interface, and could be extended to a study of Ce-based compounds. {copyright} {ital 1997} {ital The American Physical Society}

  12. Fabrication and characterization of cerium-doped barium titanate inverse opal by sol-gel method

    SciTech Connect

    Jin Yi; Zhu Yihua Yang Xiaoling; Li Chunzhong; Zhou Jinghong

    2007-01-15

    Cerium-doped barium titanate inverted opal was synthesized from barium acetate contained cerous acetate and tetrabutyl titanate in the interstitial spaces of a polystyrene (PS) opal. This procedure involves infiltration of precursors into the interstices of the PS opal template followed by hydrolytic polycondensation of the precursors to amorphous barium titanate and removal of the PS opal by calcination. The morphologies of opal and inverse opal were characterized by scanning electron microscope (SEM). The pores were characterized by mercury intrusion porosimetry (MIP). X-ray photoelectron spectroscopy (XPS) investigation showed the doping structure of cerium, barium and titanium. And powder X-ray diffraction allows one to observe the influence of doping degree on the grain size. The lattice parameters, crystal size and lattice strain were calculated by the Rietveld refinement method. The synthesis of cerium-doped barium titanate inverted opals provides an opportunity to electrically and optically engineer the photonic band structure and the possibility of developing tunable three-dimensional photonic crystal devices. - Graphical abstract: Cerium-doped barium titanate inverted opal was synthesized from barium acetate acid contained cerous acetate and tetrabutyl titanate in the interstitial spaces of a PS opal, which involves infiltration of precursors into the interstices of the PS opal template and removal of the PS opal by calcination.

  13. Long range ordered alloys modified by addition of niobium and cerium

    DOEpatents

    Liu, C.T.

    1984-08-22

    Long range ordered alloys are described having the nominal composition (Fe,Ni,Co)/sub 3/ (V,M) where M is a ductility enhancing metal selected from the group Ti, Zr, Hf with additions of small amounts of cerium and niobium to dramatically enhance the creep properties of the resulting alloys.

  14. Long range ordered alloys modified by addition of niobium and cerium

    DOEpatents

    Liu, Chain T.

    1987-01-01

    Long range ordered alloys are described having the nominal composition (Fe,Ni,Co).sub.3 (V,M) where M is a ductility enhancing metal selected from the group Ti, Zr, Hf with additions of small amounts of cerium and niobium to drammatically enhance the creep properties of the resulting alloys.

  15. Demonstration of enhanced K-edge angiography using a cerium target x-ray generator

    SciTech Connect

    Sato, Eiichi; Tanaka, Etsuro; Mori, Hidezo; Kawai, Toshiaki; Ichimaru, Toshio; Sato, Shigehiro; Takayama, Kazuyoshi; Ido, Hideaki

    2004-11-01

    The cerium target x-ray generator is useful in order to perform enhanced K-edge angiography using a cone beam because K-series characteristic x rays from the cerium target are absorbed effectively by iodine-based contrast mediums. The x-ray generator consists of a main controller, a unit with a Cockcroft-Walton circuit and a fixed anode x-ray tube, and a personal computer. The tube is a glass-enclosed diode with a cerium target and a 0.5-mm-thick beryllium window. The maximum tube voltage and current were 65 kV and 0.4 mA, respectively, and the focal-spot sizes were 1.0x1.3 mm. Cerium K{alpha} lines were left using a barium sulfate filter, and the x-ray intensity was 0.48 {mu}C/kg at 1.0 m from the source with a tube voltage of 60 kV, a current of 0.40 mA, and an exposure time of 1.0 s. Angiography was performed with a computed radiography system using iodine-based microspheres. In coronary angiography of nonliving animals, we observed fine blood vessels of approximately 100 {mu}m with high contrasts.

  16. Synthesis, electrical and dielectric characterization of cerium doped nano copper ferrites

    SciTech Connect

    Malana, Muhammad Aslam Qureshi, Raheela Beenish; Ashiq, Muhammad Naeem; Zafar, Zafar Iqbal

    2013-11-15

    Graphical abstract: Lattice constant (a) and activation energy (Ea) as a function of Ce (cerium) content. - Highlights: • The simple and economic method has been adopted for the synthesis of nanoferrites. • The electrical resistivity increases with cerium concentration. • DC electrical resistivity of these materials favours their use in microwave devices. • Dielectric measurements show semiconductor nature of the synthesized ferrites. - Abstract: The nanosized CuFe{sub 2−x}Ce{sub x}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6, 0.8) ferrites doped with cerium are synthesized by chemical co-precipitation method. The synthesized materials are characterized by XRD, FTIR, TGA and SEM. XRD analysis of cerium substituted copper ferrites confirms the cubic spinel structure. The average crystallite size calculated by using Scherrer's formula ranges from 37 to 53 nm. The values of cell constant and cell volume vary with the dopant concentration. These variations can be explained in terms of their ionic radii. The DC electrical resistivity, measured by two point probe method, increases with increase in dopant concentration while it decreases with rise in temperature exhibiting semiconductor behaviour. Energy of activation of these ferrites is calculated by using Arrhenius type resistivity plots. Dielectric measurements of the synthesized compounds show exponential decrease in dielectric constant and dielectric loss factor with increase in frequency. This indicates the normal dielectric behaviour of ferrites.

  17. Compact x-ray generator utilizing cerium-target tube for angiography

    NASA Astrophysics Data System (ADS)

    Sato, Eiichi; Tanaka, Etsuro; Mori, Hidezo; Kawai, Toshiaki; Ito, Fumihito; Ichimaru, Toshio; Sato, Shigehiro; Takayama, Kazuyoshi; Ido, Hideaki

    2004-11-01

    The cerium-target x-ray tube is useful in order to perform cone beam K-edge angiography because K-series characteristic x rays from the cerium target are absorbed effectively by iodine-based contrast mediums. The x-ray generator consists of a main controller and a unit with a high-voltage circuit and a fixed anode x-ray tube. The tube is a glass-enclosed diode with a cerium target and a 0.5 mm-thick beryllium window. The maximum tube voltage and current were 65 kV and 0.4 mA, respectively, and the focal-spot sizes were 1.3×0.9 mm. Cerium K-series characteristic x rays were left using a 3.0 mm-thick aluminum filter, and the x-ray intensity was 0.59 μC/kg at 1.0 m from the source with a tube voltage of 60 kV, a current of 0.40 mA, and an exposure time of 1.0 s. Angiography was performed with a computed radiography system using iodine-based microspheres 15 μm in diameter. In angiography of non-living animals, we observed fine blood vessels of approximately 100 μm with high contrasts.