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Sample records for cerium oxide films

  1. 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.

  2. 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

  3. Studies of Solution Deposited Cerium Oxide Thin Films on Textured Ni-Alloy Substractes for YBCO Superconductor

    SciTech Connect

    Stewart, Erin L; Bhuiyan, Md S; Sathyamurthy, Srivatsan; Paranthaman, Mariappan Parans

    2006-01-01

    Cerium oxide (CeO2) buffer layers play an important role for the development of YBa2Cu3O7-x (YBCO) based superconducting tapes using the rolling assisted biaxially textured substrates (RABiTS) approach. The chemical solution deposition (CSD) approach has been used to grow epitaxial CeO2 films on textured Ni-3 a 4% W alloy substrates with various starting precursors of ceria. Precursors such as cerium acetate, cerium acetylacetonate, cerium 2-ethylhexanoate, cerium nitrate, and cerium trifluoroacetate were prepared in suitable solvents. The optimum growth conditions for these cerium precursors were Ar-4% H2 gas processing atmosphere, solution concentration levels of 0.2-0.5 M, a dwell time of 15 min, and a process temperature range of 1050-1150 degrees C. X-ray diffraction, AFM, SEM, and optical microscopy were used to characterize the CeO2 films. Highly textured CeO2 layers were obtained on Ni-W substrates with both cerium acetate and cerium acetylacetonate as starting precursors. YBCO films with a Jc of 1.5 MA/cm2 were obtained on cerium acetylacetonate-based CeO2 films with sputtered YSZ and CeO2 cap layers.

  4. 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.

  5. 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.

  6. Metal-organic chemical vapor deposition of cerium oxide, gallium-indium-oxide, and magnesium oxide thin films: Precursor design, film growth, and film characterization

    NASA Astrophysics Data System (ADS)

    Edleman, Nikki Lynn

    A new class of volatile, low-melting, fluorine-free lanthanide metal-organic chemical vapor deposition (MOCVD) precursors has been developed. The neutral, monomeric cerium, neodymium, gadolinium, and erbium complexes are coordinatively saturated by a versatile, multidentate, ether-functionalized beta-ketoiminate ligand, and complex melting point and volatility characteristics can be tuned by altering the alkyl substituents on the ligand periphery. Direct comparison with lanthanide beta-diketonate complexes reveals that the present precursor class is a superior choice for lanthanide oxide MOCVD. Epitaxial CeO 2 buffer layer films have been grown on (001) YSZ substrates by MOCVD at significantly lower temperatures than previously reported using one of the newly developed cerium precursors. High-quality YBCO films grown on these CeO2 buffer layers by POMBE exhibit very good electrical transport properties. The cerium complex has therefore been explicitly demonstrated to be a stable and volatile precursor and is attractive for low-temperature growth of coated conductor multilayer structures by MOCVD. Gallium-indium-oxide thin films (GaxIn2-xO 3), x = 0.0˜1.1, have been grown by MOCVD using the volatile metal-organic precursors In(dpm)3 and Ga(dpm)3. The films have a homogeneously Ga-substituted, cubic In2O3 microstructure randomly oriented on quartz or heteroepitaxial on (100) YSZ single-crystal substrates. The highest conductivity of the as-grown films is found at x = 0.12. The optical transmission window and absolute transparency of the films rivals or exceeds that of the most transparent conductive oxides known. Reductive annealing results in improved charge transport characteristics with little loss of optical transparency. No significant difference in electrical properties is observed between randomly oriented and heteroepitaxial films, thus arguing that carrier scattering effects at high-angle grain boundaries play a minor role in the film conductivity mechanism

  7. 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

    2013-01-01

    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

  8. 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.

  9. 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.

  10. 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.

  11. 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

  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 PAGESBeta

    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. 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.

  16. 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.

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

    DOEpatents

    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.

  18. Corrosion resistance and durability of superhydrophobic surface formed on magnesium alloy coated with nanostructured cerium oxide film and fluoroalkylsilane molecules in corrosive NaCl aqueous solution.

    PubMed

    Ishizaki, Takahiro; Masuda, Yoshitake; Sakamoto, Michiru

    2011-04-19

    The corrosion resistant performance and durability of the superhydrophobic surface on magnesium alloy coated with nanostructured cerium oxide film and fluoroalkylsilane molecules in corrosive NaCl aqueous solution were investigated using electrochemical and contact angle measurements. The durability of the superhydrophobic surface in corrosive 5 wt% NaCl aqueous solution was elucidated. The corrosion resistant performance of the superhydrophobic surface formed on magnesium alloy was estimated by electrochemical impedance spectroscopy (EIS) measurements. The EIS measurements and appropriate equivalent circuit models revealed that the superhydrophobic surface considerably improved the corrosion resistant performance of magnesium alloy AZ31. American Society for Testing and Materials (ASTM) standard D 3359-02 cross cut tape test was performed to investigate the adhesion of the superhydrophobic film to the magnesium alloy surface. The corrosion formation mechanism of the superhydrophobic surface formed on the magnesium alloy was also proposed.

  19. 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.

  20. Nanocrystalline cerium oxide materials for solid fuel cell systems

    SciTech Connect

    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.

  1. 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(-)). PMID:27035210

  2. 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.

  3. An investigation of the continuum resonance effect in cerium and cerium oxide

    NASA Astrophysics Data System (ADS)

    Roberts, Mark W.

    1998-10-01

    Large x-ray emission resonances associated with the M shell in cerium and cerium oxide were investigated. The device used in this investigation consisted of an energy dispersive x-ray detector and a double-pass cylindrical mirror electron analyzer within an ultra-high vacuum system. Observations were made of the x-ray and electron emissions from samples bombarded by mono-energetic electrons from an electron gun. The x-ray and electron data were recorded with the system pressure in the low 10-9 torr range. X-ray data were obtained using incident electron energies from 865 eV to 925 eV; the binding energies of the cerium M5 and M4 subshells and the x-ray continuum resonances are contained within this energy range. The x- ray detector was set to count x-rays in a fixed energy window 120 eV wide, centered on 900 eV. Differentiated electron spectra from the samples were recorded using a lock-in amplifier. Vacuum evaporation and condensation were used to deposit cerium metal samples onto a wheel which was then rotated to position a given sample in front of the electron gun. Cerium oxide samples were obtained by exposing cerium metal deposits to room air at atmospheric pressure and then repumping the system. The x-ray yield spectra from the cerium and cerium oxide samples show large resonances for incident electron energies near the M5 and M4 level ionization energies. There are no features in the electron spectra which correspond to the large resonances observed in the x-ray yield spectra. These findings are in agreement with results previously obtained by Chamberlain et al. and by Mason. The maxima in the x-ray resonances for cerium oxide occur at slightly lower incident electron energy than those for cerium metal. There is also a large increase in the intensity of the x-ray continuum resonance yield in cerium oxide above that in the metal. Possible explanations for these observations are presented.

  4. Optical glass surfaces polishing by cerium oxide particles

    NASA Astrophysics Data System (ADS)

    Bouzid, D.; Belkhie, N.; Aliouane, T.

    2012-02-01

    The use of powders in metallic oxides as means of grinding and polishing of the optical glass components have seen recently a large application in optical industry. In fact, cerium oxide abrasive is more used in the optical glass polishing. It is used as grains abrasive in suspension or fixed abrasive (pellets); these pellets are manufactured from a mixture made of cerium oxide abrasive and a organic binder. The cerium oxide used in the experiments is made by (Logitech USA) of 99 % purity, the average grain size of the particle is 300 nm, the density being 6,74 g /cm3 and the specific surface is 3,3042 m2/g. In this study, we are interested in the surfaces quality of the optical glass borosilicate crown (BK7) polished by particles in cerium oxide bounded by epoxy. The surfaces of the optical glass treated are characterized by the roughness, the flatness by using the microscope Zygo and the SEM.

  5. 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 ...

  6. 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.

  7. In situ growth of epitaxial cerium tungstate (100) thin films.

    PubMed

    Skála, Tomáš; Tsud, Nataliya; Orti, Miguel Ángel Niño; Menteş, Tevfik Onur; Locatelli, Andrea; Prince, Kevin Charles; Matolín, Vladimír

    2011-04-21

    The deposition of ceria on a preoxidized W(110) crystal at 870 K has been studied in situ by photoelectron spectroscopy and low-energy electron diffraction. Formation of an epitaxial layer of crystalline cerium tungstate Ce(6)WO(12)(100), with the metals in the Ce(3+) and W(6+) chemical states, has been observed. The interface between the tungsten substrate and the tungstate film consists of WO suboxide. At thicknesses above 0.89 nm, cerium dioxide grows on the surface of Ce(6)WO(12), favoured by the limited diffusion of tungsten from the substrate. PMID:21399780

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

    DOE PAGESBeta

    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 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

  9. 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.

  10. 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).

  11. Nanoparticulate cerium dioxide and cerium dioxide-titanium dioxide composite thin films on glass by aerosol assisted chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Qureshi, Uzma; Dunnill, Charles W.; Parkin, Ivan P.

    2009-11-01

    Two series of composite thin films were deposited on glass by aerosol assisted chemical vapour deposition (AACVD)—nanoparticulate cerium dioxide and nanoparticulate cerium dioxide embedded in a titanium dioxide matrix. The films were analysed by a range of techniques including UV-visible absorption spectroscopy, X-ray diffraction, scanning electron microscopy and energy dispersive analysis by X-rays. The AACVD prepared films showed the functional properties of photocatalysis and super-hydrophilicity. The CeO 2 nanoparticle thin films displaying photocatalysis and photo-induced hydrophilicity almost comparable to that of anatase titania.

  12. 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.

  13. 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.

  14. 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.

  15. 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 ...

  16. 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.

  17. 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. PMID:26355535

  18. 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

  19. 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.

  20. 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

  1. Deposition and investigation of lanthanum-cerium hexaboride thin films

    SciTech Connect

    Kuzanyan, A.S. . E-mail: akuzan@ipr.sci.am; Harutyunyan, S.R.; Vardanyan, V.O.; Badalyan, G.R.; Petrosyan, V.A.; Kuzanyan, V.S.; Petrosyan, S.I.; Karapetyan, V.E.; Wood, K.S.; Wu, H.-D.

    2006-09-15

    Thin films of lanthanum-cerium hexaboride, the promising thermoelectric material for low-temperature applications, are deposited on various substrates by the electron-beam evaporation, pulsed laser deposition and magnetron sputtering. The influence of the deposition conditions on the films X-ray characteristics, composition, microstructure and physical properties, such as the resistivity and Seebeck coefficient, is studied. The preferred (100) orientation of all films is obtained from XRD traces. In the range of 780-800 deg. C deposition temperature the highest intensity of diffractions peaks and the highest degree of the preferred orientation are observed. The temperature dependence of the resistivity and the Seebeck coefficient of films are investigated in the temperature range of 4-300 K. The features appropriate to Kondo effect in the dependences {rho}(T) and S(T) are detected at temperatures below 20 K. Interplay between the value of the Seebeck coefficient, metallic parameters and Kondo scattering of investigated films is discussed. - Graphical abstract: Kondo scattering in (La,Ce)B{sub 6} films: temperature dependence of the resistivity of (La,Ce)B{sub 6} films on various substrates and the ceramics La{sub 0.99}Ce{sub 0.01}B{sub 6}.

  2. 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

  3. 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

  4. 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

  5. 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

  6. Synthesis and characterization of polyvinylpyrrolidone coated cerium oxide nanoparticles.

    PubMed

    Merrifield, Ruth C; Wang, Zhi Wei; Palmer, Richard E; Lead, Jamie R

    2013-01-01

    There is a pressing need for the development of standard and reference nanomaterials for environmental nanoscience and nanotoxicology. To that aim, suspensions of polyvinylpyrrolidone (PVP)-coated ceria nanoparticles (NPs) were produced. Four differently sized monodispersed samples were produced by using different PVP chain lengths. The chemical and physical properties of these NPs were characterized as prepared and in different ecotoxicology exposure media. Dynamic light scattering analysis showed that the samples were monodispersed, with an unchanged size when suspended in the different media over a 72 h period. Electron microscopy confirmed this and revealed that the larger (ca. 20 nm) particles were aggregates composed of the smaller individual particles (4-5 nm). Electron energy loss spectroscopy (EELS) showed that the smallest and largest samples were composed almost entirely of cerium(III) oxide, with only small amounts of cerium(IV) present in the largest sample. Dissolved cerium concentrations in media were low and constant, showing that the NPs did not dissolve over time. The simple synthesis of the these NPs and their physical and chemical stability in different environmental conditions make them potentially suitable for use as reference materials for (eco)toxicology and surface water environmental studies.

  7. 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.

  8. Redox reactivity of cerium oxide nanoparticles against dopamine.

    PubMed

    Hayat, Akhtar; Andreescu, Daniel; Bulbul, Gonca; Andreescu, Silvana

    2014-03-15

    The interaction between dopamine and the redox active cerium oxide nanoparticles, or nanoceria was studied using a suite of spectroscopic and surface characterization methods. Changes in the chemical reactivity and concentration of dopamine upon exposure to nanoceria was assessed in aqueous solutions and a human physiological fluid--human serum. The results indicate strong attachment of dopamine to the nanoparticle surface through oxidation followed by chemisorption of the oxidative product with formation of a charge transfer complex. Such oxidation/surface adsorption processes between nanoceria and dopamine lead to a reduction of the concentration of free dopamine in aqueous environments. These findings suggest that the redox reactivity of nanoceria may alter dopamine levels in biological systems exposed to these particles and indicate the need for a comprehensive assessment of the potential neurological consequences that might result from intended or unintended exposure to these particles. PMID:24461841

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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. PMID:27478962

  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. 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.

  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). PMID:27088851

  18. Direct growth of cerium oxide nanorods on diverse substrates for superhydrophobicity and corrosion resistance

    NASA Astrophysics Data System (ADS)

    Cho, Young Jun; Jang, Hanmin; Lee, Kwan-Soo; Kim, Dong Rip

    2015-06-01

    Superhydrophobic surfaces with anti-corrosion properties have attracted great interest in many industrial fields, particularly to enhance the thermal performance of offshore applications such as heat exchangers, pipelines, power plants, and platform structures. Nanostructures with hydrophobic materials have been widely utilized to realize superhydrophobicity of surfaces, and cerium oxide has been highlighted due to its good corrosion resistive and intrinsically hydrophobic properties. However, few studies of direct growth of cerium oxide nanostructures on diverse substrates have been reported. Herein we report a facile hydrothermal method to directly grow cerium oxide nanorods on diverse substrates, such as aluminum alloy, stainless steel, titanium, and silicon. Diverse substrates with cerium oxide nanorods exhibited superhydrophobicity with no hydrophobic modifiers on their surfaces, and showed good corrosion resistive properties in corrosive medium. We believe our method could pave the way for realization of scalable and sustainable corrosion resistive superhydrophobic surfaces in many industrial fields.

  19. 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...

  20. 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.

  1. 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. PMID:26672385

  2. Induction of pulmonary fibrosis by cerium oxide nanoparticles

    PubMed Central

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

    2015-01-01

    Cerium compounds have been used as a diesel engine catalyst to lower the mass of diesel exhaust particles, but are emitted as cerium oxide (CeO2) nanoparticles in the diesel exhaust. In a previous study, we have demonstrated a wide range of CeO2-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 CeO2 in a rat model at various time points up to 84 days post-exposure. Male Sprague Dawley rats were exposed to CeO2 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 CeO2 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. CeO2 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 CeO2 and euthanized at 28 days post-exposure. Collectively, our studies show that CeO2 induced fibrotic lung injury in rats, suggesting it may cause potential health effects. PMID:22613087

  3. 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.

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

    PubMed

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

    2013-01-01

    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.

  5. 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

  6. Antioxidant Cerium Oxide Nanoparticles in Biology and Medicine.

    PubMed

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

    2016-05-17

    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.

  7. Antioxidant cerium oxide nanoparticle hydrogels for cellular encapsulation.

    PubMed

    Weaver, Jessica D; Stabler, Cherie L

    2015-04-01

    Oxidative stress and the resulting radical by-products cause significant toxicity and graft loss in cellular transplantation. Here, the engineering of an auto-catalytic, antioxidant, self-renewing cerium oxide nanoparticle (CONP)-composite hydrogel is reported. This enzyme-mimetic material ubiquitously scavenges ambient free radicals, with the potential to provide indefinite antioxidant protection. The potential of this system to enhance the protection of encapsulated beta cells was evaluated. Co-incubation of CONPs free in solution with beta cells demonstrated potent cytoprotection from superoxide exposure; however, phagocytosis of the CONPs by the beta cells resulted in cytotoxicity at concentrations as low as 1mM. When CONPs were embedded within alginate hydrogels, the composite hydrogel provided cytoprotection to encapsulated beta cells from free radical attack without cytotoxicity, even up to 10mM. This nanocomposite hydrogel has wide applicability in cellular transplantation, with the unique advantage of localization of these potent antioxidant CONPs and their capacity for sustained, long-term scavenging. PMID:25620795

  8. Antioxidant Cerium Oxide Nanoparticle Hydrogels for Cellular Encapsulation

    PubMed Central

    Weaver, Jessica D; Stabler, Cherie L

    2015-01-01

    Oxidative stress and the resulting radical by-products cause significant toxicity and graft loss in cellular transplantation. Here, the engineering of an auto-catalytic, antioxidant, self-renewing cerium oxide nanoparticle (CONP)-composite hydrogel is reported. This enzyme-mimetic material ubiquitously scavenges ambient free radicals, with the potential to provide indefinite antioxidant protection. Here, we evaluated the potential of this system to enhance the protection of encapsulated beta cells. Co-incubation of CONPs, free in solution with beta cells, demonstrated potent cytoprotection from superoxide exposure; however, phagocytosis of the CONPs by the beta cells resulted in cytotoxicity at concentrations as low as 1 mM. When CONPs were embedded within alginate hydrogels, the composite hydrogel provided cytoprotection to encapsulated beta cells from free radical attack without cytotoxicity, even up to 10 mM concentrations. This nanocomposite hydrogel has wide applicability in cellular transplantation, with the unique advantage of localization of these potent antioxidant CONPs and their capacity for sustained, long-term scavenging. PMID:25620795

  9. 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

  10. 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. PMID:24079896

  11. Precipitation-Redispersion of Cerium Oxide Nanoparticles with Poly(acrylic acid): Toward Stable Dispersions

    SciTech Connect

    Sehgal,A.; Lalatonne, Y.; Berret, J.; Morvan, M.

    2005-01-01

    We exploit a precipitation-redispersion mechanism for complexation of short chain polyelectrolytes with cerium oxide nanoparticles to extend their stability ranges. As synthesized, cerium oxide sols at pH 1.4 consist of monodisperse cationic nanocrystalline particles having a hydrodynamic diameter of 10 nm and a molecular weight of 400 000 g mol{sup -1}. We show that short chain uncharged poly(acrylic acid) at low pH when added to a cerium oxide sols leads to macroscopic precipitation. As the pH is increased, the solution spontaneously redisperses into a clear solution of single particles with an anionic poly(acrylic acid) corona. The structure and dynamics of cerium oxide nanosols and their hybrid polymer-inorganic complexes in solution are investigated by static and dynamic light scattering, X-ray scattering, and chemical analysis. Quantitative analysis of the redispersed sol gives rise to an estimate of 40-50 polymer chains per particle for stable suspension. This amount represents 20% of the mass of the polymer-nanoparticle complexes. This complexation adds utility to the otherwise unstable cerium oxide dispersions by extending the range of stability of the sols in terms of pH, ionic strength, and concentration.

  12. 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.

  13. 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. PMID:27343939

  14. A new class of homogeneous visible-light photocatalysts: molecular cerium vanadium oxide clusters.

    PubMed

    Seliverstov, Andrey; Streb, Carsten

    2014-07-28

    The first systematic access to molecular cerium vanadium oxides is presented. A family of structurally related, di-cerium-functionalized vanadium oxide clusters and their use as visible-light-driven photooxidation catalysts is reported. Comparative analyses show that photocatalytic activity is controlled by the cluster architecture. Increased photoreactivity of the cerium vanadium oxides in the visible range compared with nonfunctionalized vanadates is observed. Based on the recent discovery of the first molecular cerium vanadate cluster, (nBu4 N)2 [(Ce(dmso)3 )2 V12 O33 Cl]⋅2 DMSO (1), two new di-cerium-containing vanadium oxide clusters [(Ce(dmso)4 )2 V11 O30 Cl]⋅DMSO (2) and [(Ce(nmp)4 )2 V12 O32 Cl]⋅NMP⋅Me2 CO (3; NMP=N-methyl-2-pyrrolidone) were obtained by using a novel fragmentation and reassembly route. Pentagonal building units {(V)M5 } (M=V, Ce) reminiscent of "Müller-type" pentagons are observed in 2 and 3. Compounds 1-3 feature high visible-light photooxidative activity, and quantum efficiencies >10 % for indigo photooxidation are observed. Photocatalytic performance increases in the order 1<3<2. Mechanistic studies show that the irradiation wavelength and the presence of oxygen strongly affect photoreactivity. Initial findings suggest that the photooxidation mechanism proceeds by intermediate formation of hydroxyl radicals. The findings open new avenues for the bottom-up design of sunlight-driven photocatalysts.

  15. Effect of cerium oxide nanoparticles on intestinal serotonin in zebrafish

    PubMed Central

    Özel, Rıfat Emrah; Hayat, Akhtar; Wallace, Kenneth N.; Andreescu, Silvana

    2013-01-01

    Cerium oxide nanoparticles or nanoceria are emerging as a new and promising class of nanoparticle technology for biomedical applications. The safe implementation of these particles in clinical applications requires evaluation of their redox properties and reactivity that might cause neurotoxic effects by interacting with redox components of the physiological environment. We report in vitro and in vivo studies to evaluate the impact of nanoceria exposure on serotonin (5-HT), an important neurotransmitter that plays a critical role in various physiological processes including motility and secretion in the digestive system. In vitro studies of 5-HT in the presence of nanoceria using spectroscopic, electrochemical and surface characterization methods demonstrate that nanoceria interacts with 5-HT and forms a surface adsorbed 5-HT-nanoceria complex. Further in vivo studies in live zebrafish embryos indicate depletion of the 5-HT level in the intestine for exposure periods longer than three days. Intestinal 5-HT was assessed quantitatively in live embryos using implantable carbon fiber microelectrodes and the results were compared to immunohistochemistry of the dissected intestine. 20 and 50 ppm nanoparticle exposure decreased the 5-HT level to 20.5 (±1.3) and 5.3 (±1.5) nM respectively as compared to 30.8 (±3.4) nM for unexposed control embryos. The results suggest that internalized nanoceria particles can concentrate 5-HT at the nanoparticle accumulation site depleting it from the surrounding tissue. This finding might have long term implications in the neurophysiology and functional development of organisms exposed to these particles through intended or unintended exposure. PMID:24015353

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

    PubMed Central

    Asano, Shinichi; Arvapalli, Ravikumar; Manne, Nandini DPK; 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 (Po) function (sham: 25.6±1.6 N/cm2 vs CeO2: 23.4±0.8 N/cm2 vs Sep: 15.9±1.0 N/cm2 vs Sep+CeO2: 20.0±1.0 N/cm2, 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. PMID:26491293

  17. Effect of cerium oxide nanoparticles on intestinal serotonin in zebrafish.

    PubMed

    Ozel, Rıfat Emrah; Hayat, Akhtar; Wallace, Kenneth N; Andreescu, Silvana

    2013-09-21

    Cerium oxide nanoparticles or nanoceria are emerging as a new and promising class of nanoparticle technology for biomedical applications. The safe implementation of these particles in clinical applications requires evaluation of their redox properties and reactivity that might cause neurotoxic effects by interacting with redox components of the physiological environment. We report in vitro and in vivo studies to evaluate the impact of nanoceria exposure on serotonin (5-HT), an important neurotransmitter that plays a critical role in various physiological processes including motility and secretion in the digestive system. In vitro studies of 5-HT in the presence of nanoceria using spectroscopic, electrochemical and surface characterization methods demonstrate that nanoceria interacts with 5-HT and forms a surface adsorbed 5-HT-nanoceria complex. Further in vivo studies in live zebrafish embryos indicate depletion of the 5-HT level in the intestine for exposure periods longer than three days. Intestinal 5-HT was assessed quantitatively in live embryos using implantable carbon fiber microelectrodes and the results were compared to immunohistochemistry of the dissected intestine. 20 and 50 ppm nanoparticle exposure decreased the 5-HT level to 20.5 (±1.3) and 5.3 (±1.5) nM respectively as compared to 30.8 (±3.4) nM for unexposed control embryos. The results suggest that internalized nanoceria particles can concentrate 5-HT at the nanoparticle accumulation site depleting it from the surrounding tissue. This finding might have long term implications in the neurophysiology and functional development of organisms exposed to these particles through intended or unintended exposure. PMID:24015353

  18. 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.

  19. 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.

  20. Photoemission of the Oxidation of Cerium Overlayers on GaSb(110) Surface

    NASA Astrophysics Data System (ADS)

    Liang, Qi; Wu, Jian-xin; Ji, Ming-rong; Ma, Mao-sheng; Liu, Xian-ming; Zhang, Yu-heng

    1997-10-01

    We have used x-ray photoelectron spectroscopy to study the oxidation of cerium overlayers on a semiconductor GaSb(110) surface. A GaSb(110) sample covered with 10 monolayers Ce was used to adsorb oxygen. When the exposure of O2 was up to 50 L, the oxide of cerium, Ce2O3, began to change into unstable CeO2. The dissociation of CeO2 resulted in strong oxidation of the substrate. The main products are Ga2O3, Sb2O3, and then Sb2O5. After annealing, a part of the oxygen atoms transferred from cerium dioxide toward Ga and Sb.

  1. Development of graphene-nanometre-sized cerium oxide-incorporated aluminium and its electrochemical evaluation

    NASA Astrophysics Data System (ADS)

    Ashraf, P. Muhamed; Thomas, Saly N.; Edwin, Leela

    2016-02-01

    Graphene-nanometre-sized cerium oxide-incorporated aluminium was prepared and its electrochemical and surface morphological characteristics were studied. The atomic force micrographs and scanning electron micrographs evaluation highlighted that the graphene and nanometre-sized cerium oxide in aluminium had decreased the surface roughness and improved the surface morphological characteristics. The graphene: nanometre-sized cerium oxide (ratios 1:2 or 2:1) with lesser amounts of particle in the matrix showed excellent corrosion resistance in the marine environment as evidenced by linear polarization, electrochemical impedance and weight loss studies. Introduction of graphene in the aluminium matrix showed a barrier separation between the outermost layer and inner layer, increased roughness and increased corrosion. The material is found to be a potential candidate for use in marine environment.

  2. 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.

  3. Cerium Oxide Nanoparticles and Bulk Cerium Oxide Leading to Different Physiological and Biochemical Responses in Brassica rapa.

    PubMed

    Ma, Xingmao; Wang, Qiang; Rossi, Lorenzo; Zhang, Weilan

    2016-07-01

    Cerium oxide nanoparticles (CeO2NPs) have been incorporated into many commercial products, and their potential release into the environment through the use and disposal of these products has caused serious concerns. Despite the previous efforts and rapid progress on elucidating the environmental impact of CeO2NPs, the long-term impact of CeO2NPs to plants, a key component of the ecosystem, is still not well understood. The potentially different impact of CeO2NPs and their bulk counterparts to plants is also unclear. The main objectives of this study were (1) to investigate whether continued irrigation with solutions containing different concentrations of CeO2NPs (0, 10, and 100 mg/L) would induce physiological and biochemical adjustments in Brassica rapa in soil growing conditions and (2) to determine whether CeO2NPs and bulk CeO2 particles exert different impacts on plants. The results indicated that bulk CeO2 at 10 and 100 mg/L enhanced plant biomass by 28% and 35%, respectively, while CeO2NPs at equivalent concentrations did not. While the bulk CeO2 treatment resulted in significantly higher concentrations of hydrogen peroxide (H2O2) in plant tissues at the vegetative stage, CeO2NPs led to significantly higher H2O2 levels in plant tissues at the floral stage. The activity of superoxide dismutase (SOD) in Brassica rapa also displayed a growth-stage dependent response to different sizes of CeO2 while catalase (CAT) activity was not affected by either size of CeO2 throughout the life cycle of Brassica rapa. Altogether, the results demonstrated that plant responses to CeO2 exposure varied with the particle sizes and the growth stages of plants.

  4. Cerium Oxide Nanoparticles and Bulk Cerium Oxide Leading to Different Physiological and Biochemical Responses in Brassica rapa.

    PubMed

    Ma, Xingmao; Wang, Qiang; Rossi, Lorenzo; Zhang, Weilan

    2016-07-01

    Cerium oxide nanoparticles (CeO2NPs) have been incorporated into many commercial products, and their potential release into the environment through the use and disposal of these products has caused serious concerns. Despite the previous efforts and rapid progress on elucidating the environmental impact of CeO2NPs, the long-term impact of CeO2NPs to plants, a key component of the ecosystem, is still not well understood. The potentially different impact of CeO2NPs and their bulk counterparts to plants is also unclear. The main objectives of this study were (1) to investigate whether continued irrigation with solutions containing different concentrations of CeO2NPs (0, 10, and 100 mg/L) would induce physiological and biochemical adjustments in Brassica rapa in soil growing conditions and (2) to determine whether CeO2NPs and bulk CeO2 particles exert different impacts on plants. The results indicated that bulk CeO2 at 10 and 100 mg/L enhanced plant biomass by 28% and 35%, respectively, while CeO2NPs at equivalent concentrations did not. While the bulk CeO2 treatment resulted in significantly higher concentrations of hydrogen peroxide (H2O2) in plant tissues at the vegetative stage, CeO2NPs led to significantly higher H2O2 levels in plant tissues at the floral stage. The activity of superoxide dismutase (SOD) in Brassica rapa also displayed a growth-stage dependent response to different sizes of CeO2 while catalase (CAT) activity was not affected by either size of CeO2 throughout the life cycle of Brassica rapa. Altogether, the results demonstrated that plant responses to CeO2 exposure varied with the particle sizes and the growth stages of plants. PMID:26691446

  5. Hydrothermal preparation of fractal dendrites: Cerium carbonate hydroxide and cerium oxide

    SciTech Connect

    Wu Mingzai; Zhang Qihua; Liu Yanmei; Fang Qingqing; Liu Xiansong

    2009-06-03

    The surfactant-assisted hydrothermal route was used to prepare fractal dendrite cerium carbonate hydroxide (CeOHCO{sub 3}) microstructures. After annealing at 600 deg. C for 4 h, the products were transformed to CeO{sub 2}. The crystal structures of the two compounds were determined by X-ray diffraction (XRD). The morphologies and microstructures were characterized by field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). Room temperature photoluminescence (PL) showed that a strong ultraviolet emission at 336 nm was observed for CeOHCO{sub 3}, and that centered at 415 nm for CeO{sub 2} microstructures. Both of these emission peaks are different from those reported for CeOHCO{sub 3} and CeO{sub 2} with other shapes. In addition, the possible growth mechanism of dendrite CeOHCO{sub 3} microstructures and the role of surfactant polyvinyl pyrrolidone (PVP) were also investigated in this paper.

  6. 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.

  7. 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.

  8. 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,...

  9. 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. PMID:24981679

  10. 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

  11. 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...

  12. Electrochemical & Thermochemical Behavior of Cerium(IV) Oxide delta

    NASA Astrophysics Data System (ADS)

    Chueh, William C.

    The mixed-valent nature of nonstoichiometric ceria (CeO2-delta ) gives rise to a wide range of intriguing properties, such as mixed ionic and electronic conduction and oxygen storage. Surface and transport behavior in rare-earth (samaria) doped and undoped ceria were investigated, with particular emphasis on applications in electrochemical and thermochemical energy conversion processes such as fuel cells and solar fuel production. The electrochemical responses of bulk-processed ceria with porous Pt and Au electrodes were analyzed using 1-D and 2-D transport models to decouple surface reactions, near-surface transport and bulk transport. Combined experimental and numerical results indicate that hydrogen electro-oxidation and hydrolysis near open-circuit conditions occur preferentially over the ceria | gas interface rather than over the ceria | gas | metal interface, with the rate-limiting step likely to be either surface reaction or transport through the surface oxygen vacancy depletion layer. In addition, epitaxial thin films of ceria were grown on zirconia substrates using pulsed-laser deposition to examine electrocatalysis over well-defined microstructures. Physical models were derived to analyze the electrochemical impedance response. By varying the film thickness, interfacial and chemical capacitance were decoupled, with the latter shown to be proportional to the small polaron densities. The geometry of microfabricated metal current collectors (metal = Pt, Ni) was also systematically varied to investigate the relative activity of the ceria | gas and the ceria | metal | gas interfaces. The data suggests that the electrochemical activity of the metal-ceria composite is only weakly dependent on the metal due to the relatively high activity of the ceria | gas interface. In addition to electrochemical experiments, thermochemical reduction-oxidation studies were performed on ceria. It was shown that thermally-reduced ceria, upon exposure to H 2O and/or CO2, can be

  13. 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.

  14. Stabilized chromium oxide film

    DOEpatents

    Garwin, Edward L.; Nyaiesh, Ali R.

    1988-01-01

    Stabilized air-oxidized chromium films deposited on high-power klystron ceramic windows and sleeves having a thickness between 20 and 150.ANG. are useful in lowering secondary electron emission yield and in avoiding multipactoring and window failure due to overheating. The ceramic substrate for the film is chosen from alumina, sapphire or beryllium oxide.

  15. Stabilized chromium oxide film

    DOEpatents

    Nyaiesh, A.R.; Garwin, E.L.

    1986-08-04

    Stabilized air-oxidized chromium films deposited on high-power klystron ceramic windows and sleeves having a thickness between 20 and 150A are useful in lowering secondary electron emission yield and in avoiding multipactoring and window failure due to overheating. The ceramic substrate for the film is chosen from alumina, sapphire or beryllium oxide.

  16. 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

  17. 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.

  18. 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.

  19. Stability and morphology of cerium oxide surfaces in an oxidizing environment: A first-principles investigation

    NASA Astrophysics Data System (ADS)

    Fronzi, Marco; Soon, Aloysius; Delley, Bernard; Traversa, Enrico; Stampfl, Catherine

    2009-09-01

    We present density functional theory investigations of the bulk properties of cerium oxides (CeO2 and Ce2O3) and the three low index surfaces of CeO2, namely, (100), (110), and (111). For the surfaces, we consider various terminations including surface defects. Using the approach of "ab initio atomistic thermodynamics," we find that the most stable surface structure considered is the stoichiometric (111) surface under "oxygen-rich" conditions, while for a more reducing environment, the same (111) surface, but with subsurface oxygen vacancies, is found to be the most stable one, and for a highly reducing environment, the (111) Ce-terminated surface becomes energetically favored. Interestingly, this latter surface exhibits a significant reconstruction in that it becomes oxygen terminated and the upper layers resemble the Ce2O3(0001) surface. This structure could represent a precursor to the phase transition of CeO2 to Ce2O3.

  20. 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.

  1. 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

  2. Unveiling the mechanism of uptake and sub-cellular distribution of cerium oxide nanoparticles†

    PubMed Central

    Singh, Sanjay; Kumar, Amit; Karakoti, Ajay; Seal, Sudipta; Self, William T.

    2011-01-01

    Cerium oxide nanoparticles (CNPs) have been recently studied for their potent superoxide scavenging properties in both cell and animal model systems. Data from these model systems have shown that exposure of cells to CNPs results in the protection against reactive oxygen species (ROS). Despite these exciting findings, very little is known regarding the uptake or subcellular distribution of these nanomaterials inside cells. In this study we utilized fluorophore (carboxyfluorescein) conjugated cerium oxide NPs (CCNPs) to study the mechanism of uptake and to elucidate the subcellular localization of CNPs using a keratinocyte model system. We observed rapid uptake (within 3 h) of CCNPs that was governed by energy-dependent, clathrin-mediated and caveolae-mediated endocytic pathways. We found CCNPs co-localized with mitochondria, lysosomes and endoplasmic reticulum as well as being abundant in the cytoplasm and the nucleus. Given the radical scavenging properties of cerium oxide and the widespread cellular disposition we observed, CNPs likely act as cellular antioxidants in multiple compartments of the cell imparting protection against a variety of oxidant injuries. PMID:20697616

  3. 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.

  4. Cerium oxide nanoparticles protect endothelial cells from apoptosis induced by oxidative stress.

    PubMed

    Chen, Shizhu; Hou, Yingjian; Cheng, Gong; Zhang, Cuimiao; Wang, Shuxiang; Zhang, Jinchao

    2013-07-01

    Oxidative stress is well documented to cause injury to endothelial cells (ECs), which in turn trigger cardiovascular diseases. Previous studies revealed that cerium oxide nanoparticles (nanoceria) had antioxidant property, but the protective effect of nanoceria on ROS injury to ECs and cardiovascular diseases has not been reported. In the current study, we investigated the protective effect and underlying mechanisms of nanoceria on oxidative injury to ECs. The cell viability, lactate dehydrogenase release, cellular uptake, intracellular localization and reactive oxygen species (ROS) levels, endocytosis mechanism, cell apoptosis, and mitochondrial membrane potential were performed. The results indicated that nanoceria had no cytotoxicity on ECs but had the ability to prevent injury by H2O2. Nanoceria could be uptaken into ECs through caveolae- and clathrin-mediated endocytosis and distributed throughout the cytoplasma. The internalized nanoceria effectively attenuated ROS overproduction induced by H2O2. Apoptosis was also alleviated greatly by nanoceria pretreatment. These results may be helpful for more rational application of nanoceria in biomedical fields in the future.

  5. 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.

  6. 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.

  7. Long-term testing of in-situ cerium oxide coated anodes for aluminum electrowinning

    SciTech Connect

    King, H.L.

    1989-10-01

    The ELTECH Anode Phase 2 Project (Contract Number AC07-86ID12655), as supported by the Department of Energy (DOE) from December 1988 through April 1989, focused on long-term testing of in-situ anodically deposited cerium oxide (CEROX) coatings on nickel ferrite/Cu cermets. The specific objective of this research was to determine the effectiveness of the CEROX coating in reducing the transfer of cermet components to the produced aluminum. A dosing regimen was first established for the minimum addition of cerium to the cell necessary to produce targeted CEROX coatings on the cermet anode and the periodic additions necessary to maintain coating thicknesses. The effects of the addition of CeF{sub 3} on CEROX coating formation was evaluated for targeted coating thicknesses at three different current densities. Analytical procedures were identified for determining alumina concentrations and the cryolite bath ratio for quasi-commercial baths.

  8. Neuroprotective mechanisms of cerium oxide nanoparticles in a mouse hippocampal brain slice model of ischemia.

    PubMed

    Estevez, A Y; Pritchard, S; Harper, K; Aston, J W; Lynch, A; Lucky, J J; Ludington, J S; Chatani, P; Mosenthal, W P; Leiter, J C; Andreescu, S; Erlichman, J S

    2011-09-15

    Cerium oxide nanoparticles (nanoceria) are widely used as catalysts in industrial applications because of their potent free radical-scavenging properties. Given that free radicals play a prominent role in the pathology of many neurological diseases, we explored the use of nanoceria as a potential therapeutic agent for stroke. Using a mouse hippocampal brain slice model of cerebral ischemia, we show here that ceria nanoparticles reduce ischemic cell death by approximately 50%. The neuroprotective effects of nanoceria were due to a modest reduction in reactive oxygen species, in general, and ~15% reductions in the concentrations of superoxide (O(2)(•-)) and nitric oxide, specifically. Moreover, treatment with nanoceria markedly decreased (~70% reduction) the levels of ischemia-induced 3-nitrotyrosine, a modification to tyrosine residues in proteins induced by the peroxynitrite radical. These findings suggest that scavenging of peroxynitrite may be an important mechanism by which cerium oxide nanoparticles mitigate ischemic brain injury. Peroxynitrite plays a pivotal role in the dissemination of oxidative injury in biological tissues. Therefore, nanoceria may be useful as a therapeutic intervention to reduce oxidative and nitrosative damage after a stroke. PMID:21704154

  9. 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. PMID:25701552

  10. Custom cerium oxide nanoparticles protect against a free radical mediated autoimmune degenerative disease in the brain.

    PubMed

    Heckman, Karin L; DeCoteau, William; Estevez, Ana; Reed, Kenneth J; Costanzo, Wendi; Sanford, David; Leiter, James C; Clauss, Jennifer; Knapp, Kylie; Gomez, Carlos; Mullen, Patrick; Rathbun, Elle; Prime, Kelly; Marini, Jessica; Patchefsky, Jamie; Patchefsky, Arthur S; Hailstone, Richard K; Erlichman, Joseph S

    2013-12-23

    Cerium oxide nanoparticles are potent antioxidants, based on their ability to either donate or receive electrons as they alternate between the +3 and +4 valence states. The dual oxidation state of ceria has made it an ideal catalyst in industrial applications, and more recently, nanoceria's efficacy in neutralizing biologically generated free radicals has been explored in biological applications. Here, we report the in vivo characteristics of custom-synthesized cerium oxide nanoparticles (CeNPs) in an animal model of immunological and free-radical mediated oxidative injury leading to neurodegenerative disease. The CeNPs are 2.9 nm in diameter, monodispersed and have a -23.5 mV zeta potential when stabilized with citrate/EDTA. This stabilizer coating resists being 'washed' off in physiological salt solutions, and the CeNPs remain monodispersed for long durations in high ionic strength saline. The plasma half-life of the CeNPs is ∼4.0 h, far longer than previously described, stabilized ceria nanoparticles. When administered intravenously to mice, the CeNPs were well tolerated and taken up by the liver and spleen much less than previous nanoceria formulations. The CeNPs were also able to penetrate the brain, reduce reactive oxygen species levels, and alleviate clinical symptoms and motor deficits in mice with a murine model of multiple sclerosis. Thus, CeNPs may be useful in mitigating tissue damage arising from free radical accumulation in biological systems.

  11. Adsorption and dissociation of methanol on the fully oxidized and partially reduced (111) cerium oxide surface: dependence on the configuration of the cerium 4f electrons

    SciTech Connect

    Beste, Ariana; Mullins, David R; Overbury, Steven {Steve} H; Harrison, Robert J

    2008-01-01

    The adsorption and dissociation of methanol on the fully oxidized and partially reduced (111) cerium oxide surface is studied using the PW91 functional as well as the PW91+U scheme. We investigate the influence of the detailed electronic structure of the Ce 4f band on the chemistry of methanol on the surface. For the partially reduced surface we obtain a spin delocalized, a ferromagnetic, and an anti-ferromagnetic solution. We find that the qualitative conclusions are independent of the surface type used. Methanol adsorption is exothermic on the fully oxidized as well as on the partially reduced surface. Also dissociation of methanol on the surface is exothermic but strongly enhanced by the presence of a vacancy. We localize an on-top methoxy species as a dissociation product on the fully oxidized surface and a triply bridged methoxy species on the partially reduced surface where the methoxy oxygen partly fills the oxygen vacancy in the surface. Adsorption energies are influenced by the introduction of the repulsive Hubbard (U) term. On the other hand, relative surface stabilities like dissociation energies are less sensitive.

  12. Surface structures of cerium oxide nanocrystalline particles from the size dependence of the lattice parameters

    NASA Astrophysics Data System (ADS)

    Tsunekawa, S.; Ito, S.; Kawazoe, Y.

    2004-10-01

    Cerium oxide nanocrystalline particles are synthesized and monodispersed in the size range from 2 to 8nm in diameter. The dependence of the lattice parameters on particle size is obtained by x-ray and electron diffraction analyses. The size dependence well coincides with the estimation based on the assumption that the surface is composed of one layer of Ce2O3 and the inside consists of CeO2. The effect of particle size on lattice parameters is discussed from the differences in the fabrication method and the surface structure.

  13. Preparation of Thin Melanin-Type Films by Surface-Controlled Oxidation.

    PubMed

    Salomäki, Mikko; Tupala, Matti; Parviainen, Timo; Leiro, Jarkko; Karonen, Maarit; Lukkari, Jukka

    2016-04-26

    The preparation of thin melanin films suitable for applications is challenging. In this work, we present a new alternative approach to thin melanin-type films using oxidative multilayers prepared by the sequential layer-by-layer deposition of cerium(IV) and inorganic polyphosphate. The interfacial reaction between cerium(IV) in the multilayer and 5,6-dihydroxyindole (DHI) in the adjacent aqueous solution leads to the formation of a thin uniform film. The oxidation of DHI by cerium(IV) proceeds via known melanin intermediates. We have characterized the formed DHI-melanin films using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), UV-vis spectroscopy, and spectroelectrochemistry. When a five-bilayer oxidative multilayer is used, the film is uniform with a thickness of ca. 10 nm. Its chemical composition, as determined using XPS, is typical for melanin. It is also redox active, and its oxidation occurs in two steps, which can be assigned to semiquinone and quinone formation within the indole structural motif. Oxidative multilayers can also oxidize dopamine, but the reaction stops at the dopamine quinone stage because of the limited amount of the multilayer-based oxidizing agent. However, dopamine oxidation by Ce(IV) was studied also in solution by UV-vis spectroscopy and mass spectrometry in order to verify the reaction mechanism and the final product. In solution, the oxidation of dopamine by cerium shows that the indole ring formation takes place already at low pH and that the mass spectrum of the final product is practically identical with that of commercial melanin. Therefore, layer-by-layer formed oxidative multilayers can be used to deposit functional melanin-type thin films on arbitrary substrates by a surface-controlled reaction.

  14. Cerium-based binary and ternary oxides in the transesterification of dimethylcarbonate with phenol.

    PubMed

    Dibenedetto, Angela; Angelini, Antonella; di Bitonto, Luigi; De Giglio, Elvira; Cometa, Stefania; Aresta, Michele

    2014-04-01

    Diphenyl carbonate (DPC) plays a key role in phosgene-free carbonylation processes. It can be produced by transesterification of dimethyl carbonate (DMC) with phenol in the presence of catalysts. Methyl phenyl carbonate (MPC) is first produced that is then converted into DPC by either disproportionation or further transesterification with phenol. Cerium-based bimetallic oxides (with the heterometal being niobium, iron, palladium, or aluminum) are used as catalysts in the transesterification of DMC to synthesize MPC. The catalytic activity is affected by the type and concentration of the heterometal. XPS, IR and elementary analyses are employed to characterize the new catalysts. Differently from pure oxides, the mixed oxides produce a significant increase of the conversion and selectivity towards MPC. PMID:24616260

  15. 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.

  16. Cyanex 923 as the extractant in a rare earth element impurity analysis of high-purity cerium oxide.

    PubMed

    Duan, Taicheng; Li, Hongfei; Kang, JianZhen; Chen, Hangting

    2004-06-01

    In this work, the feasibility of employing Cyanex 923 as an extractant into the non-cerium REE (rare earth elements) impurity analysis of high-purity cerium oxide was investigated. Through investigations on the choice of the extraction medium, the optimium extraction acidity, matrix Ce4+ effect on the non-cerium REE ion extraction, the optimium extractant concentration and suitable extracting time, and oscillation strengh, it was found that when the phase ratio was at 1:1 and the acicidity was about 2% H2SO4, by gently shaking by hand for about 2 min, 10 mL of 30% Cyanex 923 could not extract even for a 20 ng amount of non-cerium REE3+ ions. However, the extraction efficiency for Ce4+ of 100 mg total amount under the same conditions was about 96%, indicating that a 25-fold preconcentration factor could be achieved. Thus, it was concluded that Cyanex 923 could be used in a REE impurity analysis of 99.9999% or so pure cerium oxide for primary sepapation to elimilate matrix-induced interferences encountered in an ICP-MS (inductively coupled plasma mass spectroscopy) determination.

  17. Cerium oxide for the destruction of chemical warfare agents: A comparison of synthetic routes.

    PubMed

    Janoš, Pavel; Henych, Jiří; Pelant, Ondřej; Pilařová, Věra; Vrtoch, Luboš; Kormunda, Martin; Mazanec, Karel; Štengl, Václav

    2016-03-01

    Four different synthetic routes were used to prepare active forms of cerium oxide that are capable of destroying toxic organophosphates: a sol-gel process (via a citrate precursor), homogeneous hydrolysis and a precipitation/calcination procedure (via carbonate and oxalate precursors). The samples prepared via homogeneous hydrolysis with urea and the samples prepared via precipitation with ammonium bicarbonate (with subsequent calcination at 500°C in both cases) exhibited the highest degradation efficiencies towards the extremely dangerous nerve agents soman (O-pinacolyl methylphosphonofluoridate) and VX (O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate) and the organophosphate pesticide parathion methyl. These samples were able to destroy more than 90% of the toxic compounds in less than 10 min. The high degradation efficiency of cerium oxide is related to its complex surface chemistry (presence of surface OH groups and surface non-stoichiometry) and to its nanocrystalline nature, which promotes the formation of crystal defects on which the decomposition of organophosphates proceeds through a nucleophilic substitution mechanism that is not dissimilar to the mechanism of enzymatic hydrolysis of organic phosphates by phosphotriesterase. PMID:26561750

  18. Cerium oxide for the destruction of chemical warfare agents: A comparison of synthetic routes.

    PubMed

    Janoš, Pavel; Henych, Jiří; Pelant, Ondřej; Pilařová, Věra; Vrtoch, Luboš; Kormunda, Martin; Mazanec, Karel; Štengl, Václav

    2016-03-01

    Four different synthetic routes were used to prepare active forms of cerium oxide that are capable of destroying toxic organophosphates: a sol-gel process (via a citrate precursor), homogeneous hydrolysis and a precipitation/calcination procedure (via carbonate and oxalate precursors). The samples prepared via homogeneous hydrolysis with urea and the samples prepared via precipitation with ammonium bicarbonate (with subsequent calcination at 500°C in both cases) exhibited the highest degradation efficiencies towards the extremely dangerous nerve agents soman (O-pinacolyl methylphosphonofluoridate) and VX (O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate) and the organophosphate pesticide parathion methyl. These samples were able to destroy more than 90% of the toxic compounds in less than 10 min. The high degradation efficiency of cerium oxide is related to its complex surface chemistry (presence of surface OH groups and surface non-stoichiometry) and to its nanocrystalline nature, which promotes the formation of crystal defects on which the decomposition of organophosphates proceeds through a nucleophilic substitution mechanism that is not dissimilar to the mechanism of enzymatic hydrolysis of organic phosphates by phosphotriesterase.

  19. 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.

  20. 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. PMID:25242526

  1. Physical and chemical characterization of cerium(IV) oxide nanoparticles.

    PubMed

    Cepriá, Gemma; Córdova, Walvin R; Céspedes, Oscar; Sánchez-García, Laura; Ferrer, Pilar; Gianolio, Diego; Castillo, Juan R

    2016-09-01

    Chemical composition, size and structure of the nanoparticle are required to describe nanoceria. Nanoparticles of similar size and Ce(III) content might exhibit different chemical behaviour due to their differences in structure. A simple and direct procedure based on affordable techniques for all the laboratories is presented in this paper. The combination of Raman and UV-vis spectroscopy and particle impact coulometry (PIC) allows the characterization of nanoceria of small size from 4 to 65 nm at a concentration from micromolar to nanomolar, a concentration range suitable for the analysis of lab-prepared or commercial nanoparticle suspensions, but too high for most analytical purposes aimed at nanoparticle monitoring. While the PIC limits of size detection are too high to observe small nanoparticles unless catalytic amplification is used, the method provides a simple means to study aggregation of nanoparticles in the media they are needed to be dispersed for each application. Raman spectroscopy provided information about structure of the nanoparticle, and UV-vis about their chemical behaviour against some common reducing and oxidizing agents. Graphical Abstract To characterize nanoceria it is necessary to provide information about the shape, size and structure of the nanoparticles as well as the chemical composition.

  2. Heteroaggregation of Cerium Oxide Nanoparticles and Nanoparticles of Pyrolyzed Biomass.

    PubMed

    Yi, Peng; Pignatello, Joseph J; Uchimiya, Minori; White, Jason C

    2015-11-17

    Heteroaggregation with indigenous particles is critical to the environmental mobility of engineered nanomaterials (ENM). We studied heteroaggregation of ceria nanoparticles (n-CeO2), as a model for metal oxide ENM, with nanoparticles of pyrogenic carbonaceous material (n-PCM) derived from pecan shell biochar, a model for natural chars and human-made chars used in soil remediation and agriculture. The TEM and STEM images of n-PCM identify both hard and soft particles, both C-rich and C,O,Ca-containing particles (with CaCO3 crystals), both amorphous and "onion-skin" C-rich particles, and traces of nanotubes. Heteroaggregation was evaluated at constant n-CeO2, variable n-PCM concentration by monitoring hydrodynamic diameter by dynamic light scattering and ζ-potential under conditions where n-PCM is "invisible". At pH 5.3, where n-CeO2 and n-PCM are positively and negatively charged, respectively, and each stable to homoaggregation, heteroaggregation is favorable and occurs by a charge neutralization-charge reversal mechanism (CNCR): in this mechanism, primary heteroaggregates that form in the initial stage are stable at low or high n-PCM concentration due to electrostatic repulsion, but unstable at intermediate n-PCM concentration, leading to secondary heteroaggregation. The greatest instability coincides with full charge neutralization. At pH 7.1, where n-CeO2 is neutral and unstable alone, and n-PCM is negative and stable alone, heteroaggregation occurs by a charge-accumulation, core-shell stabilization (CACS) mechanism: n-PCM binds to and forms a negatively charged shell on the neutral surface of the nascent n-CeO2 core, stabilizing the core-shell heteraggregate at a size that decreases with n-PCM concentration. The CNCR and CACS mechanisms give fundamental insight into heteroaggregation between oppositely charged, and between neutral and charged nanoparticles. PMID:26461459

  3. 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

  4. 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

  5. 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.

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

    SciTech Connect

    Marina, Olga A; Stevenson, Jeffry W

    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.

  7. 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.

  8. 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...

  9. Air, aqueous and thermal stabilities of Ce3+ ions in cerium oxide nanoparticle layers with substrates.

    PubMed

    Naganuma, Tamaki; Traversa, Enrico

    2014-06-21

    Abundant oxygen vacancies coexisting with Ce(3+) ions in fluorite cerium oxide nanoparticles (CNPs) have the potential to enhance catalytic ability, but the ratio of unstable Ce(3+) ions in CNPs is typically low. Our recent work, however, demonstrated that the abundant Ce(3+) ions created in cerium oxide nanoparticle layers (CNPLs) by Ar ion irradiation were stable in air at room temperature. Ce valence states in CNPs correlate with the catalytic ability that involves redox reactions between Ce(3+) and Ce(4+) ions in given application environments (e.g. high temperature in carbon monoxide gas conversion and immersion conditions in biomedical applications). To better understand the mechanism by which Ce(3+) ions achieve stability in CNPLs, we examined (i) extra-long air-stability, (ii) thermal stability up to 500 °C, and (iii) aqueous stability of Ce(3+) ions in water, buffer solution and cell culture medium. It is noteworthy that air-stability of Ce(3+) ions in CNPLs persisted for more than 1 year. Thermal stability results showed that oxidation of Ce(3+) to Ce(4+) occurred at 350 °C in air. Highly concentrated Ce(3+) ions in ultra-thin CNPLs slowly oxidized in water within 1 day, but stability was improved in the cell culture medium. Ce(3+) stability of CNPLs immersed in the medium was associated with phosphorus adsorption on the Ce(3+) sites. This study also illuminates the potential interaction mechanisms of stable Ce(3+) ions in CNPLs. These findings could be utilized to understand catalytic mechanisms of CNPs with abundant oxygen vacancies in their application environments.

  10. 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.

  11. Vacuum annealed cerium-substituted yttrium iron garnet films on non-garnet substrates for integrated optical circuits

    SciTech Connect

    Goto, Taichi; Ross, C. A.; Eto, Yu; Kobayashi, Keiichi; Haga, Yoji; Inoue, Mitsuteru

    2013-05-07

    Polycrystalline cerium-substituted yttrium iron garnet (CeYIG) showing large Faraday rotation (FR) in the near-IR region was grown on non-garnet (synthetic fused silica, Si, and Si-on-insulator) substrates by sputtering followed by thermal annealing in vacuum. The FR of the films is comparable to the single crystal value. Structural characterization, magnetic properties, refractive index, extinction coefficient, surface topography, and FR vs. wavelength were measured and the magnetooptical figure of merit was compared with that of CeYIG films on garnet substrates.

  12. Magneto-optical properties of cerium substituted yttrium iron garnet films with reduced thermal budget for monolithic photonic integrated circuits.

    PubMed

    Goto, Taichi; Onbaşlı, Mehmet C; Ross, C A

    2012-12-17

    Thin films of polycrystalline cerium substituted yttrium iron garnet (CeYIG) were grown on an yttrium iron garnet (YIG) seed layer on Si and Si-on-insulator substrates by pulsed laser deposition, and their optical and magneto-optical properties in the near-IR region were measured. A YIG seed layer of ~30 nm thick processed by rapid thermal anneal at 800°C provided a virtual substrate to promote crystallization of the CeYIG. The effect of the thermal budget of the YIG/CeYIG growth process on the film structure, magnetic and magnetooptical properties was determined.

  13. 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

  14. 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

  15. Sensitization of Pancreatic Cancer Cells to Radiation by Cerium Oxide Nanoparticle-Induced ROS Production

    PubMed Central

    Wason, Melissa S.; Colon, Jimmie; Das, Soumen; Seal, Sudipta; Turkson, James; Zhao, Jihe; Baker, Cheryl H.

    2012-01-01

    Side effect of radiation therapy (RT) remains the most challenging issue for pancreatic cancer treatment. In this report we determined whether and how cerium oxide nanoparticles (CONPs) sensitize pancreatic cancer cells to RT. CONP pretreatment enhanced radiation-induced reactive oxygen species (ROS) production preferentially in acidic cell-free solutions as well as acidic human pancreatic cancer cells. In acidic environments, CONPs favor the scavenging of superoxide radical over the hydroxyl peroxide resulting in accumulation of the latter whereas in neutral pH CONPs scavenge both. CONP treatment prior to RT markedly potentiated the cancer cell apoptosis both in culture and in tumors and the inhibition of the pancreatic tumor growth without harming the normal tissues or host mice. Taken together, these results identify CONPs as a potentially novel RT-sensitizer as well as protectant for improving pancreatic cancer treatment. PMID:23178284

  16. Catalytic ozonation of oxalate with a cerium supported palladium oxide: an efficient degradation not relying on hydroxyl radical oxidation.

    PubMed

    Zhang, Tao; Li, Weiwei; Croué, Jean-Philippe

    2011-11-01

    The cerium supported palladium oxide (PdO/CeO(2)) at a low palladium loading was found very effective in catalytic ozonation of oxalate, a probe compound that is difficult to be efficiently degraded in water with hydroxyl radical oxidation and one of the major byproducts in ozonation of organic matter. The oxalate was degraded into CO(2) during the catalytic ozonation. The molar ratio of oxalate degraded to ozone consumption increased with increasing catalyst dose and decreasing ozone dosage and pH under the conditions of this study. The maximum molar ratio reached around 1, meaning that the catalyst was highly active and selective for oxalate degradation in water. The catalytic ozonation, which showed relatively stable activity, does not promote hydroxyl radical generation from ozone. Analysis with ATR-FTIR and in situ Raman spectroscopy revealed that 1) oxalate was adsorbed on CeO(2) of the catalyst forming surface complexes, and 2) O(3) was adsorbed on PdO of the catalyst and further decomposed to surface atomic oxygen (*O), surface peroxide (*O(2)), and O(2) gas in sequence. The results indicate that the high activity of the catalyst is related to the synergetic function of PdO and CeO(2) in that the surface atomic oxygen readily reacts with the surface cerium-oxalate complex. This kind of catalytic ozonation would be potentially effective for the degradation of polar refractory organic pollutants and hydrophilic natural organic matter.

  17. Ultrathin, epitaxial cerium dioxide on silicon

    NASA Astrophysics Data System (ADS)

    Flege, Jan Ingo; Kaemena, Björn; Höcker, Jan; Bertram, Florian; Wollschläger, Joachim; Schmidt, Thomas; Falta, Jens

    2014-03-01

    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 Ce2O3 film may very effectively be converted at room temperature to almost fully oxidized CeO2 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.

  18. 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.

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

    DOEpatents

    Willigan, Rhonda R.; Vanderspurt, Thomas Henry; Tulyani, Sonia; Radhakrishnan, Rakesh; Opalka, Susanne Marie; Emerson, Sean C.

    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.

  20. 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

  1. 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

  2. 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.

  3. 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. PMID:27053452

  4. Metal oxide films on metal

    DOEpatents

    Wu, Xin D.; Tiwari, Prabhat

    1995-01-01

    A structure including a thin film of a conductive alkaline earth metal oxide selected from the group consisting of strontium ruthenium trioxide, calcium ruthenium trioxide, barium ruthenium trioxide, lanthanum-strontium cobalt oxide or mixed alkaline earth ruthenium trioxides thereof upon a thin film of a noble metal such as platinum is provided.

  5. 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.

  6. 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

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

    PubMed

    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 Ce(3+) 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 Ce(3+) 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.

  8. Morphology of cerium oxide surfaces in an oxidzing enviroment:a first-principles investigation

    NASA Astrophysics Data System (ADS)

    Fronzi, Marco; Soon, Aloysius; Stampfl, Catherine; Delley, Bernard; Traversa, Enrico

    2007-03-01

    A good understanding of the stability and chemistry of CeO2 surfaces is crucial for a better designing of solid oxide fuel cells. As the first step, we use DFT [1] to study the structural and electronic ground state properties of bulk CeO2. various surface termination of the low-index surface of CeO2 are then investigated, namely the stoichiometric, metal- and oxygen- rich terminations, and defected surfaces. Using the concept of ab initio atomistic thermodynamics&[tilde;2], we calculate the surface free energy phase diagram. This allows us to identify and predict stable, and potentally catalytically important, structures. There is an evidence to suggest an interesting morphological change in the surface structures with varying oxygen concentration. Reaction pathways for methane oxidation on low energy cerium oxide surfaces are being investigated and will be reported.[1] Formulated in the DMol^3 code; B. Delley, J. Chem. Phys. 92, 508 (1990);ibid. 113, 7756 (2000).[2] K. Reuter, C. Stampfl and M. Scheffler, in Handbook of Materials Modeling, Volume 1, Fundamental Models and Methods, Sidney Yip (Ed)(2005).

  9. Cerium Oxide Nanoparticles Decorated Graphene Nanosheets for Selective Detection of Dopamine.

    PubMed

    Nayak, Pranati; Santhosh, P N; Ramaprabhu, S

    2015-07-01

    The fabrication of a novel amperometric biosensor based on selective determination of dopamine (DA) using nafion coated cerium oxide nanoparticles (NPs) decorated graphene nanosheets (CeO2-HEG-nafion) as a transducer candidate is reported. Graphene was synthesized by hydrogen exfoliation technique. Decoration of CeO2NPs over graphene nanosheets was done by chemical reduction method. The electrochemical impedance spectroscopy (EIS) study shows the enhanced electron transfer kinetics of the composite compared to HEG modified and bare glassy carbon electrode (GCE). The response of the composite towards dopamine displays a lower oxidation potential of 0.23 V and a high oxidation current. The sensor exhibits linearity from 10 µM to 780 µM with a detection limit of 1 µM. In the presence of nafion, it shows excellent selectivity for coexisting interference species like Ascorbic acid (AA) and Uric acid (UA). The excellent performance of the biosensor can be attributed to large active surface area, enhanced electron transfer kinetics and high catalytic activity of the composite.

  10. Enhanced field emission from cerium hexaboride coated multiwalled carbon nanotube composite films: A potential material for next generation electron sources

    SciTech Connect

    Patra, Rajkumar; Ghosh, S.; Sheremet, E.; Rodriguez, R. D.; Lehmann, D.; Gordan, O. D.; Zahn, D. R. T.; Jha, M.; Ganguli, A. K.; Schmidt, H.; Schulze, S.; Schmidt, O. G.

    2014-03-07

    Intensified field emission (FE) current from temporally stable cerium hexaboride (CeB{sub 6}) coated carbon nanotubes (CNTs) on Si substrate is reported aiming to propose the new composite material as a potential candidate for future generation electron sources. The film was synthesized by a combination of chemical and physical deposition processes. A remarkable increase in maximum current density, field enhancement factor, and a reduction in turn-on field and threshold field with comparable temporal current stability are observed in CeB{sub 6}-coated CNT film when compared to pristine CeB{sub 6} film. The elemental composition and surface morphology of the films, as examined by scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray measurements, show decoration of CeB{sub 6} nanoparticles on top and walls of CNTs. Chemical functionalization of CNTs by the incorporation of CeB{sub 6} nanoparticles is evident by a remarkable increase in intensity of the 2D band in Raman spectrum of coated films as compared to pristine CeB{sub 6} films. The enhanced FE properties of the CeB{sub 6} coated CNT films are correlated to the microstructure of the films.

  11. 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.

  12. 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.

  13. 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

  14. Plasma sprayed cerium oxide coating inhibits H2O2-induced oxidative stress and supports cell viability.

    PubMed

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

    2016-06-01

    Oxidative stress is a risk factor in the pathogenesis of osteoporosis, and plays a major role in bone regeneration of osteoporotic patients. Cerium oxide (CeO2) ceramics have the unique ability to protect various types of cells from oxidative damage, making them attractive for biomedical applications. In this study, we developed a plasma sprayed CeO2 coating with a hierarchical topography where ceria nanoparticles were superimposed in the micro-rough coating surface. The protective effects of the CeO2 coating on the response of osteoblasts to H2O2-induced oxidative stress have been demonstrated in terms of cell viability, apoptosis and differentiation. The CeO2 coating reversed the reduced superoxide dismutase activity, decreased reactive oxygen species production and suppressed malondialdehyde formation in H2O2-treated osteoblasts. It indicated that the CeO2 coating can preserve the intracellular antioxidant defense system. The cytocompatibility of the CeO2 coating was further assessed in vitro by cell viability assay and scanning electron microscopy analysis. Taken together, the CeO2 coating could provide an opportunity to be utilized as a potential candidate for bone regeneration under oxidative stress.

  15. 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

  16. 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

  17. 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

  18. 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.

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

    PubMed Central

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

    2011-01-01

    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. PMID:21704369

  20. Predicting contamination by the fuel additive cerium oxide engineered nanoparticles within the United Kingdom and the associated risks.

    PubMed

    Johnson, Andrew C; Park, Barry

    2012-11-01

    As a fuel additive, cerium oxide nanoparticles may become widely dispersed throughout the environment. Commercial information from the United Kingdom (UK) on the use of cerium oxide nanoparticles was used to perform a modeling and risk assessment exercise. Discharge from exhausts took into account the likely removal by filters fitted to these vehicles. For predicting current soil exposure, scenarios were examined, ranging from dispersion occurring across the entire UK landmass to only within the urban area to only 20 m on either side of road networks. For soils, the highest predicted contamination level was 0.016 mg/kg within 20 m of a road following seven years of continuous deposition. This value would represent 0.027% of reported natural background cerium. If usage were to double for five more years, levels would not be expected to exceed 0.04 mg/kg. River water contamination considered direct aerial deposition and indirect contamination via runoff in the water and entrained soil sediment, with the highest level of 0.02 ng/L predicted. The highest predicted water concentration of 300 ng/L was associated with water draining from a road surface, assuming a restricted deposition spread. These predictions are well below most toxicological levels of concern.

  1. Correlation of the oxidation state of cerium in sol?gel glasses as a function of thermal treatment via optical spectroscopy and XANES studies

    NASA Astrophysics Data System (ADS)

    Assefa, Zerihun; Haire, R. G.; Caulder, D. L.; Shuh, D. K.

    2004-07-01

    Sol-gel glass matrices containing lanthanides have numerous technological applications and their formation involves several chemical facets. In the case of cerium, its ability to exist in two different oxidation states or in mixed valence state provides additional complexities for the sol-gel process. The oxidation state of cerium present during different facets of preparation of sol-gel glasses, and also as a function of the starting oxidation state of cerium added, were studied both by optical spectroscopy and X-ray absorption near-edge structures (XANES). The findings acquired by each approach were compared. The primary focus was on the redox chemistries associated with sample preparation, gelation, and thermal treatment. When Ce 3+ is introduced into the starting sols, the trivalent state normally prevails in the wet and room temperature-dried gels. Heating in air at >100 °C can generate a light yellow coloration with partial oxidation to the tetravalent state. Above 200 °C and up to ˜1000 °C, cerium is oxidized to its tetravalent state. In contrast, when tetravalent cerium is introduced into the sol, both the wet and room temperature-dried gels lose the yellow-brown color of the initial ceric ammonium nitrate solution. When the sol-gel is heated to 110 °C it turns yellowish as the cerium tends to be re-oxidized. The yellow color is believed to represent the effect of oxidation and oligomerization of the cerium-silanol units in the matrix. The luminescence properties are also affected by these changes, the details of which are reported herein.

  2. Cellular uptake and activity of heparin functionalised cerium oxide nanoparticles in monocytes.

    PubMed

    Ting, S R Simon; Whitelock, John M; Tomic, Romana; Gunawan, Cindy; Teoh, Wey Yang; Amal, Rose; Lord, Megan S

    2013-06-01

    Cerium oxide nanoparticles (nanoceria) are effective in scavenging intracellular reactive oxygen species (ROS). In this study nanoceria synthesized by flame spray pyrolysis (dXRD = 12 nm) were functionalised with heparin via an organosilane linker, 3-aminopropyltriethoxysilane. Nanoceria were functionalised with approximately 130 heparin molecules per nanoparticle as determined by thermo gravimetric analysis. Heparin functionalised nanoceria were more effectively internalised by the human monocyte cell line, U937, and U937 cells that had been activated with phorbol 12 myristate 13-acetate (PMA) than bare nanoceria. The heparin functionalised nanoceria were also more effective in scavenging ROS than nanoceria in both activated and unactivated U937 cells. Heparin coupled nanoceria were found to be biologically active due to their ability to bind fibroblast growth factor 2 and signal through FGF receptor 1. Additionally, the heparin-coupled nanoceria, once internalised by the cells, were found to be degraded by 48 h. Together these data demonstrated that heparin enhanced the biological properties of nanoceria in terms of cellular uptake and ROS scavenging, while the nanoceria themselves were more effective at delivering heparin intracellularly than exposing cells to heparin in solution. PMID:23478040

  3. 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.

  4. Antioxidant Potential and Toxicity Study of the Cerium Oxide Nanoparticles Synthesized by Microwave-Mediated Synthesis.

    PubMed

    Soren, Siba; Jena, Soumya Ranjan; Samanta, Luna; Parhi, Purnendu

    2015-09-01

    Monodispersed cerium oxide nanoparticle has been synthesized by microwave-mediated hydrothermal as well as microwave-mediated solvothermal synthesis. X-ray diffraction (XRD) data shows that the synthesized particles are single phase. SEM and TEM analysis suggest that particle synthesized by microwave-mediated solvothermal method are less agglomerated. In vitro toxicology study of the synthesized nanoceria particles has shown good free radical scavenging activity for NO and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical assayed except superoxide radical within a concentration range of 25 to 75 ng ml(-1). Nanoceria particle also showed inhibition of Fe-ascorbate-induced lipid peroxidation (LPx) in chick liver mitochondrial fractions. Solvothermally synthesized nanoceria showed better protection against Fe-ascorbate-induced LPx than the hydrothermal one while the hydrothermally synthesized nanoceria showed better DPPH and NO scavenging activity. The ceria nanoparticles also prevented Fe-ascorbate-H2O2-induced carbonylation of bovine serum albumin in a dose-dependent manner. At higher concentration, i.e., 100 ng ml(-1), the synthesized nanoparticles showed a reverse trend in all the parameters measured indicating its toxicity at higher doses.

  5. 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.

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

    PubMed Central

    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. PMID:27486320

  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. 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.

  9. Electroanalytical evaluation of antioxidant activity of cerium oxide nanoparticles by nanoparticle collisions at microelectrodes.

    PubMed

    Sardesai, Naimish P; Andreescu, Daniel; Andreescu, Silvana

    2013-11-13

    We describe a simple, cost-effective and rapid electrochemical screening approach to evaluate antioxidant activity of cerium oxide nanoparticles (CeO2 NPs) by single nanoparticle collision at microelectrodes. The method is based on direct monitoring of the interaction between a Pt microelectrode and surface bound superoxo and peroxo anions of CeO2 NPs (Ce-O2(-)/O2(2-)) formed upon exposure to H2O2, selected here as a model reactive oxygen species. We observe an increase in spike current frequency for CeO2 NPs exposed to H2O2, which we attribute to the reduction of surface bound oxygen species when the particles collide with the microelectrode. The results were confirmed with spectroscopic techniques that demonstrate changes in surface reactivity and composition. The spike frequency was found to correlate well with the superoxide dismutase activity of these particles. This approach could enable routine screening of antioxidant NPs using a rapid and inexpensive assay.

  10. Intratracheal instillation of cerium oxide nanoparticles induces hepatic toxicity in male Sprague-Dawley rats

    PubMed Central

    Nalabotu, Siva K; Kolli, Madhukar B; Triest, William E; Ma, Jane Y; Manne, Nandini DPK; Katta, Anjaiah; Addagarla, Hari S; Rice, Kevin M; Blough, Eric R

    2011-01-01

    Background Cerium oxide (CeO2) nanoparticles have been posited to have both beneficial and toxic effects on biological systems. Herein, we examine if a single intratracheal instillation of CeO2 nanoparticles is associated with systemic toxicity in male Sprague-Dawley rats. Methods and results Compared with control animals, CeO2 nanoparticle exposure was associated with increased liver ceria levels, elevations in serum alanine transaminase levels, reduced albumin levels, a diminished sodium-potassium ratio, and decreased serum triglyceride levels (P < 0.05). Consistent with these data, rats exposed to CeO2 nanoparticles also exhibited reductions in liver weight (P < 0.05) and dose-dependent hydropic degeneration, hepatocyte enlargement, sinusoidal dilatation, and accumulation of granular material. No histopathological alterations were observed in the kidney, spleen, and heart. Analysis of serum biomarkers suggested an elevation of acute phase reactants and markers of hepatocyte injury in the rats exposed to CeO2 nanoparticles. Conclusion Taken together, these data suggest that intratracheal instillation of CeO2 nanoparticles can result in liver damage. PMID:22072870

  11. Electroanalytical evaluation of antioxidant activity of cerium oxide nanoparticles by nanoparticle collisions at microelectrodes.

    PubMed

    Sardesai, Naimish P; Andreescu, Daniel; Andreescu, Silvana

    2013-11-13

    We describe a simple, cost-effective and rapid electrochemical screening approach to evaluate antioxidant activity of cerium oxide nanoparticles (CeO2 NPs) by single nanoparticle collision at microelectrodes. The method is based on direct monitoring of the interaction between a Pt microelectrode and surface bound superoxo and peroxo anions of CeO2 NPs (Ce-O2(-)/O2(2-)) formed upon exposure to H2O2, selected here as a model reactive oxygen species. We observe an increase in spike current frequency for CeO2 NPs exposed to H2O2, which we attribute to the reduction of surface bound oxygen species when the particles collide with the microelectrode. The results were confirmed with spectroscopic techniques that demonstrate changes in surface reactivity and composition. The spike frequency was found to correlate well with the superoxide dismutase activity of these particles. This approach could enable routine screening of antioxidant NPs using a rapid and inexpensive assay. PMID:24079646

  12. Cerium oxide nanoparticle aggregates affect stress response and function in Caenorhabditis elegans

    PubMed Central

    Rogers, Steven; Rice, Kevin M; Manne, Nandini DPK; Shokuhfar, Tolou; He, Kun; Selvaraj, Vellaisamy

    2015-01-01

    Objective: The continual increase in production and disposal of nanomaterials raises concerns regarding the safety of nanoparticles on the environmental and human health. Recent studies suggest that cerium oxide (CeO2) nanoparticles may possess both harmful and beneficial effects on biological processes. The primary objective of this study is to evaluate how exposure to different concentrations (0.17–17.21 µg/mL) of aggregated CeO2 nanoparticles affects indices of whole animal stress and survivability in Caenorhabditis elegans. Methods: Caenorhabditis elegans were exposed to different concentrations of CeO2 nanoparticles and evaluated. Results: Our findings demonstrate that chronic exposure of CeO2 nanoparticle aggregates is associated with increased levels of reactive oxygen species and heat shock stress response (HSP-4) in Caenorhabditis elegans, but not mortality. Conversely, CeO2 aggregates promoted strain-dependent decreases in animal fertility, a decline in stress resistance as measured by thermotolerance, and shortened worm length. Conclusion: The data obtained from this study reveal the sublethal toxic effects of CeO2 nanoparticle aggregates in Caenorhabditis elegans and contribute to our understanding of how exposure to CeO2 may affect the environment. PMID:26770770

  13. 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

  14. 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

  15. 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

  16. 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.

  17. Effects of cerium oxide nanoparticles on the growth of keratinocytes, fibroblasts and vascular endothelial cells in cutaneous wound healing.

    PubMed

    Chigurupati, Srinivasulu; Mughal, Mohamed R; Okun, Eitan; Das, Soumen; Kumar, Amit; McCaffery, Michael; Seal, Sudipta; Mattson, Mark P

    2013-03-01

    Rapid and effective wound healing requires a coordinated cellular response involving fibroblasts, keratinocytes and vascular endothelial cells (VECs). Impaired wound healing can result in multiple adverse health outcomes and, although antibiotics can forestall infection, treatments that accelerate wound healing are lacking. We now report that topical application of water soluble cerium oxide nanoparticles (Nanoceria) accelerates the healing of full-thickness dermal wounds in mice by a mechanism that involves enhancement of the proliferation and migration of fibroblasts, keratinocytes and VECs. The Nanoceria penetrated into the wound tissue and reduced oxidative damage to cellular membranes and proteins, suggesting a therapeutic potential for topical treatment of wounds with antioxidant nanoparticles.

  18. Hazard and risk assessment of a nanoparticulate cerium oxide-based diesel fuel additive - a case study.

    PubMed

    Park, Barry; Donaldson, Kenneth; Duffin, Rodger; Tran, Lang; Kelly, Frank; Mudway, Ian; Morin, Jean-Paul; Guest, Robert; Jenkinson, Peter; Samaras, Zissis; Giannouli, Myrsini; Kouridis, Haris; Martin, Patricia

    2008-04-01

    Envirox is a scientifically and commercially proven diesel fuel combustion catalyst based on nanoparticulate cerium oxide and has been demonstrated to reduce fuel consumption, greenhouse gas emissions (CO(2)), and particulate emissions when added to diesel at levels of 5 mg/L. Studies have confirmed the adverse effects of particulates on respiratory and cardiac health, and while the use of Envirox contributes to a reduction in the particulate content in the air, it is necessary to demonstrate that the addition of Envirox does not alter the intrinsic toxicity of particles emitted in the exhaust. The purpose of this study was to evaluate the safety in use of Envirox by addressing the classical risk paradigm. Hazard assessment has been addressed by examining a range of in vitro cell and cell-free endpoints to assess the toxicity of cerium oxide nanoparticles as well as particulates emitted from engines using Envirox. Exposure assessment has taken data from modeling studies and from airborne monitoring sites in London and Newcastle adjacent to routes where vehicles using Envirox passed. Data have demonstrated that for the exposure levels measured, the estimated internal dose for a referential human in a chronic exposure situation is much lower than the no-observed-effect level (NOEL) in the in vitro toxicity studies. Exposure to nano-size cerium oxide as a result of the addition of Envirox to diesel fuel at the current levels of exposure in ambient air is therefore unlikely to lead to pulmonary oxidative stress and inflammation, which are the precursors for respiratory and cardiac health problems. PMID:18444008

  19. The Effect of Cerium Oxide Nanoparticle Valence State on Reactive Oxygen Species and Toxicity.

    PubMed

    Dunnick, Katherine M; Pillai, Rajalekshmi; Pisane, Kelly L; Stefaniak, Aleksandr B; Sabolsky, Edward M; Leonard, Stephen S

    2015-07-01

    Cerium oxide (CeO2) nanoparticles, which are used in a variety of products including solar cells, gas sensors, and catalysts, are expected to increase in industrial use. This will subsequently lead to additional occupational exposures, making toxicology screenings crucial. Previous toxicology studies have presented conflicting results as to the extent of CeO2 toxicity, which is hypothesized to be due to the ability of Ce to exist in both a +3 and +4 valence state. Thus, to study whether valence state and oxygen vacancy concentration are important in CeO2 toxicity, CeO2 nanoparticles were doped with gadolinium to adjust the cation (Ce, Gd) and anion (O) defect states. The hypothesis that doping would increase toxicity and decrease antioxidant abilities as a result of increased oxygen vacancies and inhibition of +3 to +4 transition was tested. Differences in toxicity and reactivity based on valence state were determined in RLE-6TN rat alveolar epithelial and NR8383 rat alveolar macrophage cells using enhanced dark field microscopy, electron paramagnetic resonance (EPR), and annexin V/propidium iodide cell viability stain. Results from EPR indicated that as doping increased, antioxidant potential decreased. Alternatively, doping had no effect on toxicity at 24 h. The present results imply that as doping increases, thus subsequently increasing the Ce(3+)/Ce(4+) ratio, antioxidant potential decreases, suggesting that differences in reactivity of CeO2 are due to the ability of Ce to transition between the two valence states and the presence of increased oxygen vacancies, rather than dependent on a specific valence state.

  20. Integration of bulk-quality thin film magneto-optical cerium-doped yttrium iron garnet on silicon nitride photonic substrates.

    PubMed

    Onbasli, Mehmet C; Goto, Taichi; Sun, Xueyin; Huynh, Nathalie; Ross, C A

    2014-10-20

    Cerium substituted yttrium iron garnet (Ce:YIG) films were grown on yttrium iron garnet (YIG) seed layers on silicon nitride films using pulsed laser deposition. Optimal process conditions for forming garnet films on silicon nitride are presented. Bulk or near-bulk magnetic and magneto-optical properties were observed for 160 nm thick Ce:YIG films grown at 640 °C on rapid thermal annealed 40 nm thick YIG grown at 640 °C and 2 Hz pulse rate. The effect of growth temperature and deposition rate on structural, magnetic and magneto-optical properties has been investigated.

  1. Cytotoxicity and antibacterial activity of gold-supported cerium oxide nanoparticles

    PubMed Central

    Suresh Babu, K; Anandkumar, M; Tsai, TY; Kao, TH; Stephen Inbaraj, B; Chen, BH

    2014-01-01

    Background Cerium oxide nanoparticles (CeO2) have been shown to be a novel therapeutic in many biomedical applications. Gold (Au) nanoparticles have also attracted widespread interest due to their chemical stability and unique optical properties. Thus, decorating Au on CeO2 nanoparticles would have potential for exploitation in the biomedical field. Methods In the present work, CeO2 nanoparticles synthesized by a chemical combustion method were supported with 3.5% Au (Au/CeO2) by a deposition-precipitation method. The as-synthesized Au, CeO2, and Au/CeO2 nanoparticles were evaluated for antibacterial activity and cytotoxicity in RAW 264.7 normal cells and A549 lung cancer cells. Results The as-synthesized nanoparticles were characterized by X-ray diffraction, scanning and transmission electron microscopy, and ultraviolet-visible measurements. The X-ray diffraction study confirmed the formation of cubic fluorite-structured CeO2 nanoparticles with a size of 10 nm. All synthesized nanoparticles were nontoxic towards RAW 264.7 cells at doses of 0–1,000 μM except for Au at >100 μM. For A549 cancer cells, Au/CeO2 had the highest inhibitory effect, followed by both Au and CeO2 which showed a similar effect at 500 and 1,000 μM. Initial binding of nanoparticles occurred through localized positively charged sites in A549 cells as shown by a shift in zeta potential from positive to negative after 24 hours of incubation. A dose-dependent elevation in reactive oxygen species indicated that the pro-oxidant activity of the nanoparticles was responsible for their cytotoxicity towards A549 cells. In addition, cellular uptake seen on transmission electron microscopic images indicated predominant localization of nanoparticles in the cytoplasmic matrix and mitochondrial damage due to oxidative stress. With regard to antibacterial activity, both types of nanoparticles had the strongest inhibitory effect on Bacillus subtilis in monoculture systems, followed by Salmonella

  2. Cerium oxides and cerium-platinum surface alloys on Pt(111) single-crystal surfaces studied by scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Berner, Ulrich; Schierbaum, Klaus-Dieter

    2002-06-01

    Three-dimensional clusters of metallic Ce are deposited on Pt(111) surfaces by thermal evaporation in ultrahigh vacuum. Different reactions occur upon heating of the sample in ultrahigh vacuum and during the exposure of oxygen that lead to distinct well-ordered surface phases. Their geometric structures are determined by scanning tunneling microscopy (STM). A two-dimensional ordered surface alloy of Pt5Ce is obtained by annealing at 1000 K. It forms two different incommensurate overlayers on Pt(111) with long-distance spacings in the moiré patterns (13.7 and 14.8 Å). Hexagonally shaped two-dimensional islands are formed upon heating the Pt(111) single crystal with a submonolayer coverage of Ce at 900 K. They are localized at step edges. STM reveals a local 2×2 structure with respect to Pt(111). It is assigned to a precursor state of alloy formation. Ordered CeO2 phases result from annealing the alloy at 1000 K in oxygen. The surface structure is consistent with oxygen-terminated fluorite-type CeO2(111). During decomposition of CeO2 at 900 K, an oxide structure is identified which is attributed to an ultrathin ordered phase of surface-Ce2O3.

  3. 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

  4. 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...

  5. Cerium (IV) oxide nanotubes prepared by low temperature deposition at normal pressure.

    PubMed

    Boehme, M; Fu, G; Ionescu, E; Ensinger, W

    2011-02-11

    This paper reports the synthesis of cerium dioxide nanotubes (CeNTs) by electroless deposition using ion-track-etched polycarbonate templates. To achieve nanotubes with thin walls and small surface roughness the tubes were generated by a several-step-containing procedure under aqueous conditions. The approach reported below will process open end nanotubes with well-defined outer diameter and wall thickness.

  6. Cerium oxide coated anodes for aluminum electrowinning: Topical report, October 1, 1986-June 30, 1987

    SciTech Connect

    Walker, J. K.

    1987-12-01

    Because of the cost of building and maintaining a carbon anode plant and the energy penalties associated with the use of carbon anodes in the production of aluminum, the use of inert anodes has long been proposed. Various cermet anodes have been investigated. In this paper, tests on a material, cerium oxyfluoride (CEROX), deposited in situ as an anode, are reported. (JDH)

  7. 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.

  8. Sulfonated macro-RAFT agents for the surfactant-free synthesis of cerium oxide-based hybrid latexes.

    PubMed

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

    2013-10-01

    Three types of amphiphatic macro-RAFT agents were employed as compatibilizers to promote the polymerization reaction at the surface of nanoceria for the synthesis of CeO2-based hybrid latexes. Macro-RAFT copolymers and terpolymers were first synthesized employing various combinations of butyl acrylate as a hydrophobic monomer and acrylic acid (AA) and/or 2-acrylamido-2-methylpropane sulfonic acid (AMPS) as hydrophilic monomers. After characterizing the adsorption of these macro-RAFT agents at the cerium oxide surface by UV-visible spectrometry, emulsion copolymerization reactions of styrene and methyl acrylate were then carried out in the presence of the surface-modified nanoceria. Dynamic Light Scattering and cryo-Transmission Electron Microscopy were employed to confirm the hybrid structure of the final CeO2/polymer latexes, and proved that the presence of acrylic acid units in amphiphatic macro-RAFT agents enabled an efficient formation of hybrid structures, while the presence of AMPS units, when combined with AA units, resulted in a better distribution of cerium oxide nanoclusters between latex particles.

  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. Cerium oxide nanoparticle uptake kinetics from the gas-phase into lung cells in vitro is transport limited.

    PubMed

    Raemy, David O; Limbach, Ludwig K; Rothen-Rutishauser, Barbara; Grass, Robert N; Gehr, Peter; Birbaum, Karin; Brandenberger, Christina; Günther, Detlef; Stark, Wendelin J

    2011-04-01

    Nowadays, aerosol processes are widely used for the manufacture of nanoparticles (NPs), creating an increased occupational exposure risk of workers, laboratory personnel and scientists to airborne particles. There is evidence that possible adverse effects are linked with the accumulation of NPs in target cells, pointing out the importance of understanding the kinetics of particle internalization. In this context, the uptake kinetics of representative airborne NPs over 30 min and their internalization after 24 h post-exposure were investigated by the use of a recently established exposure system. This system combines the production of aerosolized cerium oxide (CeO(2)) NPs by flame spray synthesis with its simultaneous particle deposition from the gas-phase onto A549 lung cells, cultivated at the air-liquid interface. Particle uptake was quantified by mass spectrometry after several exposure times (0, 5, 10, 20 and 30 min). Over 35% of the deposited mass was found internalized after 10 min exposure, a value that increased to 60% after 30 min exposure. Following an additional 24 h post-incubation, a time span, after which adverse biological effects were observed in previous experiments, over 80% of total CeO(2) could be detected intracellularly. On the ultrastructural level, focal cerium aggregates were present on the apical surface of A549 cells and could also be localized intracellularly in vesicular structures. The uptake behaviour of aerosolized CeO(2) is in line with observations on cerium suspensions, where particle mass transport was identified as the rate-limiting factor for NP internalization. PMID:21118721

  11. Gadolinium doped cerium oxide for soot oxidation: Influence of interfacial metal-support interactions

    NASA Astrophysics Data System (ADS)

    Durgasri, D. Naga; Vinodkumar, T.; Lin, Fangjian; Alxneit, Ivo; Reddy, Benjaram M.

    2014-09-01

    The aim of the present investigation was to ascertain the role of Al2O3, SiO2, and TiO2 supports in modulating the catalytic performance of ceria-based solid solutions. In this study, we prepared nanosized Ce-Gd/Al2O3, Ce-Gd/SiO2, and Ce-Gd/TiO2 catalysts by a deposition coprecipitation method and evaluated for soot oxidation. The synthesized catalysts were calcined at two different temperatures to assess their thermal stability and extensively characterized by various techniques, namely, XRD, Raman, BET surface area, TEM, H2-TPR, and UV-vis DRS. XRD and TEM results indicate that Ce-Gd-oxide nanoparticles are in highly dispersed form on the surface of the supports. Raman results show a prominent sharp peak and a broad peak corresponding to the F2g mode of ceria and the presence of oxygen vacancies, respectively. The presence of a significant number of oxygen vacancies in all samples is also confirmed from UV-vis DRS measurements. The H2-TPR results suggest that Gd-doping facilitates the reduction of the materials and decreases the onset temperature of reduction. Among the prepared samples, Ce-Gd/TiO2 catalyst exhibited the highest activity, suggesting the existence of strong interfacial metal support interaction between the active metal oxide and the support.

  12. Process for fabrication of metal oxide films

    SciTech Connect

    Tracy, C.E.; Benson, D.; Svensson, S.

    1990-07-17

    This invention is comprised of a method of fabricating metal oxide films from a plurality of reactants by inducing a reaction by plasma deposition among the reactants. The plasma reaction is effective for consolidating the reactants and producing thin films of metal oxides, e.g. electro-optically active transition metal oxides, at a high deposition rate. The presence of hydrogen during the plasma reaction enhances the deposition rate of the metal oxide. Various types of metal oxide films can be produced.

  13. 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.

  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

    2016-06-01

    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. 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

    2016-06-01

    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. PMID:27184540

  16. 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.

  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. Uptake and release of cerium during Fe-oxide formation and transformation in Fe(II) solutions.

    PubMed

    Nedel, S; Dideriksen, K; Christiansen, B C; Bovet, N; Stipp, S L S

    2010-06-15

    Fe-oxides are ubiquitous in soils and sediments and form during Fe(0) corrosion. Depending on redox conditions and solution composition, Fe-oxides such as ferrihydrite, goethite, magnetite, and green rust (GR) may form. These phases typically have high surface area and large affinity for adsorption of trace components. Further, Fe(II)-Fe(III) (hydr)oxides are redox active. Cerium, a member of the lanthanide family, can be used as an analogue for the tri- and tetra-valent actinides found in radioactive waste, expected to be stored in subsurface repositories. In experiments with ferrihydrite, Ce(III) was effectively scavenged from Fe(II)-bearing solutions within 5 min at pH 7. During transformation of ferrihydrite to green rust, however, all Ce(III) was released to solution. By varying initial solution Fe(II):Fe(III) ratio, magnetite and goethite formed together with GR(Na,SO(4)), resulting in decreased Ce(III) release. X-ray photoelectron spectroscopy revealed Ce(III) adsorbed on magnetite. When Fe-oxides were synthesized by air oxidation of Fe(II) solutions at pH 7, GR(Na,SO(4)) played a catalytic role in the oxidation of Ce(III) to Ce(IV) by O(2), removing more than 90% of the dissolved Ce. Transmission electron microscopy revealed that it formed discrete nanocrystals of CeO(2(s)). These results demonstrate that Fe-oxide interaction with radionuclides is likely to depend strongly on the local redox conditions. By analogy with Ce, the trivalent actinides are not expected to be sequestered by preformed GR in anoxic environments. Our results also suggest that trivalent actinides and lanthanides are released when dissimilatory iron reduction of Fe(III)-oxides leads to GR formation However, under oxidizing conditions, GR may influence radionuclide mobility by catalyzing their transformation to a higher oxidation state. PMID:20496931

  19. 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.

  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. Catalysts with Cerium in a Membrane Reactor for the Removal of Formaldehyde Pollutant from Water Effluents.

    PubMed

    Gutiérrez-Arzaluz, Mirella; Noreña-Franco, Luis; Ángel-Cuevas, Saúl; Mugica-Álvarez, Violeta; Torres-Rodríguez, Miguel

    2016-01-01

    We report the synthesis of cerium oxide, cobalt oxide, mixed cerium, and cobalt oxides and a Ce-Co/Al₂O₃ membrane, which are employed as catalysts for the catalytic wet oxidation (CWO) reaction process and the removal of formaldehyde from industrial effluents. Formaldehyde is present in numerous waste streams from the chemical industry in a concentration low enough to make its recovery not economically justified but high enough to create an environmental hazard. Common biological degradation methods do not work for formaldehyde, a highly toxic but refractory, low biodegradability substance. The CWO reaction is a recent, promising alternative that also permits much lower temperature and pressure conditions than other oxidation processes, resulting in economic benefits. The CWO reaction employing Ce- and Co-containing catalysts was carried out inside a slurry batch reactor and a membrane reactor. Experimental results are reported. Next, a mixed Ce-Co oxide film was supported on an γ-alumina membrane used in a catalytic membrane reactor to compare formaldehyde removal between both types of systems. Catalytic materials with cerium and with a relatively large amount of cerium favored the transformation of formaldehyde. Cerium was present as cerianite in the catalytic materials, as indicated by X-ray diffraction patterns. PMID:27231888

  2. Sorption of trivalent cerium by a mixture of microbial cells and manganese oxides: Effect of microbial cells on the oxidation of trivalent cerium

    NASA Astrophysics Data System (ADS)

    Ohnuki, Toshihiko; Jiang, Mingyu; Sakamoto, Fuminori; Kozai, Naofumi; Yamasaki, Shinya; Yu, Qianqian; Tanaka, Kazuya; Utsunomiya, Satoshi; Xia, Xiaobin; Yang, Ke; He, Jianhua

    2015-08-01

    Sorption of Ce by mixtures of synthetic Mn oxides and microbial cells of Pseudomonas fluorescens was investigated to elucidate the role of microorganisms on Ce(III) oxidative migration in the environment. The mixtures, upon which Ce was sorbed following exposure to solutions containing 1.0 × 10-4 or 1.0 × 10-5 mol L-1 Ce(III), were analyzed by scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS) and micro-X-ray fluorescence (micro-XRF) at synchrotron facilities. A Ce LIII-edge micro XANES spectra analysis was also performed to determine the oxidation states of Ce adsorbed to the Mn oxides and microbial cells in the mixtures. The distribution ratios (Kd) of Ce between the individual solids and solution increased with increasing pH of the solution, and was nearly the same in mixtures containing varying amounts of microbial cells. SEM-EDS and micro-XRF analyses showed that Ce was sorbed by both MnO2 and microbial cells (1.7 × 10-1 or 3.3 × 10-1 g L-1). In addition, nano-particles containing Ce and P developed on the surface of the microbial cells. XANES analysis showed that lower fractions of Ce(III) were oxidized to Ce(IV) in the mixtures containing greater amounts of microbial cells. Micro-XANES analysis revealed that Ce was present as Ce(III) on the microbial cells and as Ce(IV) on Mn oxides. These results strongly suggest that the association of Ce(III) with the microbial cell surface and the formation of Ce phosphate nano-particles are responsible for suppressing the oxidation of Ce(III) to Ce(IV) in the mixtures.

  3. 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.

  4. Oxidation of epitaxial Ce films

    NASA Astrophysics Data System (ADS)

    Vescovo, E.; Carbone, C.

    1996-02-01

    Single-crystal Ce films of more than 300 Å thickness have been epitaxially grown on W(110). Their interaction with molecular oxygen at room temperature has been studied by angle-resolved photoemission, low-energy electron diffraction, and Auger spectroscopy. As a function of the oxygen exposure, the reaction is found to proceed through a sequence of three distinct stages: (i) ordered dissociative surface adsorption; (ii) formation of an ordered Ce2O3-like surface oxide; and (iii) gradual conversion of the sesquioxide into a disordered surface dioxide CeO2-x. A structurally different Ce2O3 oxide is obtained after high oxygen exposures followed by heating at 450 K. The formation of the epitaxial surface sesquioxides is favored by the good lattice match with the Ce substrate. The same type of structural relation might lead to the formation of ordered sesquioxides on other rare-earth surfaces exposing hexagonal planes.

  5. 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

  6. Thin film hydrous metal oxide catalysts

    DOEpatents

    Dosch, Robert G.; Stephens, Howard P.

    1995-01-01

    Thin film (<100 nm) hydrous metal oxide catalysts are prepared by 1) synthesis of a hydrous metal oxide, 2) deposition of the hydrous metal oxide upon an inert support surface, 3) ion exchange with catalytically active metals, and 4) activating the hydrous metal oxide catalysts.

  7. 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.

  8. Cerium Oxide Nanoparticles Induced Toxicity in Human Lung Cells: Role of ROS Mediated DNA Damage and Apoptosis

    PubMed Central

    Pandey, Alok K.

    2014-01-01

    Cerium oxide nanoparticles (CeO2 NPs) have promising industrial and biomedical applications. In spite of their applications, the toxicity of these NPs in biological/physiological environment is a major concern. Present study aimed to understand the molecular mechanism underlying the toxicity of CeO2 NPs on lung adenocarcinoma (A549) cells. After internalization, CeO2 NPs caused significant cytotoxicity and morphological changes in A549 cells. Further, the cell death was found to be apoptotic as shown by loss in mitochondrial membrane potential and increase in annexin-V positive cells and confirmed by immunoblot analysis of BAX, BCl-2, Cyt C, AIF, caspase-3, and caspase-9. A significant increase in oxidative DNA damage was found which was confirmed by phosphorylation of p53 gene and presence of cleaved poly ADP ribose polymerase (PARP). This damage could be attributed to increased production of reactive oxygen species (ROS) with concomitant decrease in antioxidant “glutathione (GSH)” level. DNA damage and cell death were attenuated by the application of ROS and apoptosis inhibitors N-acetyl-L- cysteine (NAC) and Z-DEVD-fmk, respectively. Our study concludes that ROS mediated DNA damage and cell cycle arrest play a major role in CeO2 NPs induced apoptotic cell death in A549 cells. Apart from beneficial applications, these NPs also impart potential harmful effects which should be properly evaluated prior to their use. PMID:24987704

  9. 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.

  10. 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

  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. 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.

  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. PMID:27208478

  14. 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. PMID:25448805

  15. Cellular uptake and reactive oxygen species modulation of cerium oxide nanoparticles in human monocyte cell line U937.

    PubMed

    Lord, Megan S; Jung, MoonSun; Teoh, Wey Yang; Gunawan, Cindy; Vassie, James A; Amal, Rose; Whitelock, John M

    2012-11-01

    Cerium oxide nanoparticles (nanoceria) are promising materials for intracellular oxygen free radical scavenging providing a potential therapy for reactive oxygen species (ROS)-mediated inflammatory processes. In this study rhombohedral-shaped nanoceria were synthesized by flame spray pyrolysis with tuneable particle diameters between 3 and 94 nm by changing the liquid precursor flow rate. Monocytes and macrophages are major players in inflammatory processes as their production of ROS species has important downstream effects on cell signalling. Therefore, this study examined the ability of the nanoceria to be internalised by the human monocytic cell line, U937, and scavenge intracellular ROS. U937 cells activated in the presence of phorbol 12-myristate 13-acetate (PMA) were found to be more responsive to the nanoceria than U937 cells, which may not be surprising given the role of monocyte/macrophages in phagocytosing foreign material. The smaller particles were found to contain more crystal lattice defects with which to scavenge ROS, however a greater proportion of both the U937 and activated U937 cell populations responded to the larger particles. Hence all nanoceria particle sizes examined in this study were equally effective in scavenging intracellular ROS. PMID:22841920

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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. PMID:26986089

  1. 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%.

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

    DOEpatents

    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).

  3. Electrochromism in copper oxide thin films

    SciTech Connect

    Richardson, T.J.; Slack, J.L.; Rubin, M.D.

    2000-08-15

    Transparent thin films of copper(I) oxide prepared on conductive SnO2:F glass substrates by anodic oxidation of sputtered copper films or by direct electrodeposition of Cu2O transformed reversibly to opaque metallic copper films when reduced in alkaline electrolyte. In addition, the same Cu2O films transform reversibly to black copper(II) oxide when cycled at more anodic potentials. Copper oxide-to-copper switching covered a large dynamic range, from 85% and 10% photopic transmittance, with a coloration efficiency of about 32 cm2/C. Gradual deterioration of the switching range occurred over 20 to 100 cycles. This is tentatively ascribed to coarsening of the film and contact degradation caused by the 65% volume change on conversion of Cu to Cu2O. Switching between the two copper oxides (which have similar volumes) was more stable and more efficient (CE = 60 cm2/C), but covered a smaller transmittance range (60% to 44% T). Due to their large electrochemical storage capacity and tolerance for alkaline electrolytes, these cathodically coloring films may be useful as counter electrodes for anodically coloring electrode films such as nickel oxide or metal hydrides.

  4. CVD diamond film oxidation resistance research

    NASA Astrophysics Data System (ADS)

    Jing, Longwei; Wang, Xiaoping; Wang, Lijun; Pan, Xiufang; Sun, Yiqing; Wang, Jinye; Sun, Hongtao

    2013-12-01

    Diamond films were deposited on a silicon substrate by microwave plasma chemical vapor deposition system, and its oxidation experiments were carried out in atmospheric environmental condition by using a muffle furnace. Inatmospheric environment (the temperature is from 400°C to 900°C) the oxidation resistance of diamond thin films was investigated. The results indicate that under the atmospheric environment diamond thin film surface morphology did not change after 6 hours at 400°C. Diamond thin film surface morphology began to change after 2 hours at 600°C, and when time was extended to 4 hours, the diamond thin film surface morphology changed significantly. The surface morphology of diamond films began to change after 15 minutes at a 700°C condition and when time was extended to 6 hours diamond films were all destroyed. All the diamond films on the silicon substrate disappeared completely in 20 minutes at 900°C. The intact crystal face is the reason that natural diamond has stable chemical property. The crystal face of synthetic diamond film has a lot of defects, especially on the side. Oxidation of the diamond films begin with the grain boundary and defects.

  5. 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

  6. High quality oxide films on substrates

    DOEpatents

    Ruckman, M.W.; Strongin, M.; Gao, Y.L.

    1994-02-01

    A method is described for providing an oxide film of a material on the surface of a substrate using a reactive deposition of the material onto the substrate surface in the presence of a solid or liquid layer of an oxidizing gas. The oxidizing gas is provided on the substrate surface in an amount sufficient to dissipate the latent heat of condensation occurring during deposition as well as creating a favorable oxidizing environment for the material. 4 figures.

  7. High quality oxide films on substrates

    DOEpatents

    Ruckman, Mark W.; Strongin, Myron; Gao, Yong L.

    1994-01-01

    A method for providing an oxide film of a material on the surface of a substrate using a reactive deposition of the material onto the substrate surface in the presence of a solid or liquid layer of an oxidizing gas. The oxidizing gas is provided on the substrate surface in an amount sufficient to dissipate the latent heat of condensation occurring during deposition as well as creating a favorable oxidizing environment for the material.

  8. 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.

  9. Optical and magneto-optical behavior of Cerium Yttrium Iron Garnet thin films at wavelengths of 200–1770 nm

    PubMed Central

    Onbasli, Mehmet C.; Beran, Lukáš; Zahradník, Martin; Kučera, Miroslav; Antoš, Roman; Mistrík, Jan; Dionne, Gerald F.; Veis, Martin; Ross, Caroline A.

    2016-01-01

    Magneto-optical cerium-substituted yttrium iron garnet (Ce:YIG) thin films display Faraday and Kerr rotation (rotation of light polarisation upon transmission and reflection, respectively) as well as a nonreciprocal phase shift due to their non-zero off-diagonal permittivity tensor elements, and also possess low optical absorption in the near-infrared. These properties make Ce:YIG useful in providing nonreciprocal light propagation in integrated photonic circuits, which is essential for accomplishing energy-efficient photonic computation and data transport architectures. In this study, 80 nm-thick Ce:YIG films were grown on Gadolinium Gallium Garnet substrates with (100), (110) and (111) orientations using pulsed laser deposition. The films had bulk-like structural and magnetic quality. Faraday and Kerr spectroscopies along with spectroscopic ellipsometry were used to deduce the complete permittivity tensor of the films in the ultraviolet, visible and near-infrared spectral region, and the magneto-optical figure of merit as a function of wavelength was determined. The samples showed the highest IR Faraday rotation reported for thin films of Ce:YIG, which indicates the importance of this material in development of nonreciprocal photonic devices. PMID:27025269

  10. Effect of cerium substitution on microstructure and Faraday rotation of Ce x Y3- x Fe5O12 thin films

    NASA Astrophysics Data System (ADS)

    Shahrokhvand, S. M.; Mozaffari, M.; Rozatian, A. S. H.; Hamidi, S. M.; Tehranchi, M. M.

    2016-01-01

    In this work, cerium-substituted yttrium iron garnet (Ce x Y3- x Fe5O12, x = 0.25-1) targets were fabricated by conventional ceramic method at different temperatures, and their crystal structures were investigated by X-ray diffraction method. The results showed that the minimum calcining temperature required to get single-phase targets depends on x value and decreased by increasing x value. Then, thin films of the targets were deposited on GGG (444) single-crystal substrates by pulsed laser deposition technique. Based on the previous studies, preferred (444) oriented Ce x Y3- x Fe5O12 thin films were fabricated under optimum conditions. Faraday rotation of the thin films was measured at 635 nm wavelength, and the results showed that Faraday rotation and sensitivity constant increased by increasing x value. Scanning electron microscope images showed that by increasing x value, cracks on the thin films' surface increased. Atomic force microscopy images showed that the films have smooth surfaces and the surface roughness decreased by increasing the x value.

  11. Solution Grown Antimony Doped Zinc Oxide Films

    NASA Astrophysics Data System (ADS)

    Riley, Conor T.

    Zinc oxide is an extensively studied semiconducting material due to its versatile properties applicable to many technologies such as electronics, optoelectronics, sensing and renewable energy. Although zinc oxide films have been created for device fabrication, the methods used to synthesize them are expensive and unrealistic for affordable commercial devices. In addition, zinc oxide is intrinsically n-type making the realization of stable p-type materials a great challenge for light emitting diodes, solar cells and UV lasing. In this thesis zinc oxide films are created using low cost solution methods. To accomplish this, a previously unreported surfactant, tert-butanol, is used. Several controlled experiments vary the concentration of tert-butanol, zinc and oxygen sources to demonstrate the ability of tert-butanol to create low cost films. Further, small amounts of antimony glycolate are added to the reaction solution, to create antimony doped zinc oxide films on sapphire and silicon substrates. Although hall measurements indicate that the films are n-type, a discussion of antimony activation provides a feasible path for the realization of low cost, p-type zinc oxide films.

  12. Preparation and characterization of RF sputtered Ce-V mixed oxide thin films

    SciTech Connect

    Malini, D. Rachel; Sanjeeviraja, C.

    2012-06-05

    Cerium-Vanadium mixed oxide thin films were deposited at room temperature by varying RF power in RF magnetron sputtering. The morphology and structural features were studied by taking FESEM and XRD and optical properties were analyzed by taking transmittance and absorption spectra. The crystalline film shows orthorhombic CeVO{sub 3} phase and the observed grain size varies from 89.4nm to 208.7nm. The transmission increases and the absorption edge at 330nm is blue shifted with increase in RF power. The optical band gap is found to increase from 1.59 to 1.94eV. The PL spectra shows blue shift in the emission peak centered at a wavelength of 495nm with increase in RF power.

  13. 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.

  14. Zinc oxide thin film acoustic sensor

    SciTech Connect

    Mohammed, Ali Jasim; Salih, Wafaa Mahdi; Hassan, Marwa Abdul Muhsien; Nusseif, Asmaa Deiaa; Kadhum, Haider Abdullah; Mansour, Hazim Louis

    2013-12-16

    This paper reports the implementation of (750 nm) thickness of Zinc Oxide (ZnO) thin film for the piezoelectric pressure sensors. The film was prepared and deposited employing the spray pyrolysis technique. XRD results show that the growth preferred orientation is the (002) plane. A polycrystalline thin film (close to mono crystallite like) was obtained. Depending on the Scanning Electron Microscopy photogram, the film homogeneity and thickness were shown. The resonance frequency measured (about 19 kHz) and the damping coefficient was calculated and its value was found to be about (2.5538), the thin film be haves as homogeneous for under and over damped. The thin film pressure sensing was approximately exponentially related with frequency, the thin film was observed to has a good response for mechanical stresses also it is a good material for the piezoelectric properties.

  15. Mesoscopically structured nanocrystalline metal oxide thin films

    NASA Astrophysics Data System (ADS)

    Carretero-Genevrier, Adrian; Drisko, Glenna L.; Grosso, David; Boissiere, Cédric; Sanchez, Clement

    2014-11-01

    This review describes the main successful strategies that are used to grow mesostructured nanocrystalline metal oxide and SiO2 films via deposition of sol-gel derived solutions. In addition to the typical physicochemical forces to be considered during crystallization, mesoporous thin films are also affected by the substrate-film relationship and the mesostructure. The substrate can influence the crystallization temperature and the obtained crystallographic orientation due to the interfacial energies and the lattice mismatch. The mesostructure can influence the crystallite orientation, and affects nucleation and growth behavior due to the wall thickness and pore curvature. Three main methods are presented and discussed: templated mesoporosity followed by thermally induced crystallization, mesostructuration of already crystallized metal oxide nanobuilding units and substrate-directed crystallization with an emphasis on very recent results concerning epitaxially grown piezoelectric structured α-quartz films via crystallization of amorphous structured SiO2 thin films.

  16. A comparative study of the oxides of lanthanum, cerium, praseodymium, and samarium as catalysts for the oxidative dehydrogenation of methane in the presence and absence of carbon tetrachloride

    SciTech Connect

    Sugiyama, Shigeru; Matsumura, Yasuyuki; Moffat, J.B. )

    1993-02-01

    The catalytic oxidative coupling of methane to ethane and ethene has been investigated on the rare earth oxides, i.e., La[sub 2]O[sub 3], CeO[sub 2], Pr[sub 6]O[sub 11], and Sm[sub 2]O[sub 3]. Addition of a small amount of tetrachloromethane (TCM) to the reactant stream improves the catalytic activity of these oxides. In particular, the praseodymium catalyst yields high selectivity to the C[sub 2] compounds comparable to La[sub 2]O[sub 3] or Sm[sub 2]O[sub 3] when TCM is present in the feedstream. The X-ray diffraction patterns for these catalysts after the reaction with TCM show the presence of the oxychlorides in the catalysts except for the cerium catalyst, for which the selectivity to C[sub 2] compounds is very low even in the presence of TCM. The oxychlorides can be generated on La[sub 2]O[sub 3], Sm[sub 2]O[sub 3], or Pr[sub 6]O[sub 11] by preheating under a stream including TCM. The product distribution of the reaction with these catalysts in the absence of TCM is similar to that with the oxides in the presence of TCM, while Pr[sub 6]O[sub 11] pretreated with TCM is unstable with no TCM in the feedstream. It appears that the improvement of the activity of the rare earth catalysts with TCM in the feedstream is primarily due to the formation of the oxychlorides during the reaction. 49 refs., 6 figs., 5 tabs.

  17. Cerium ion conducting solid electrolyte

    NASA Astrophysics Data System (ADS)

    Hasegawa, Yasunori; Imanaka, Nobuhito; Adachi, Gin-ya

    2003-02-01

    A cerium ion conducting solid electrolyte, (Ce xZr 1- x) 4/4- xNb(PO 4) 3, was successfully realized with the NASICON-type structure which possesses a three-dimensional network, especially suitable for bulky ion migration. The cerium ion conductivity exceeds approximately one order of magnitude in comparison to that of the rare-earth ion conducting R2(WO 4) 3 and R1/3Zr 2(PO 4) 3 ( R=Sc, Y, Eu-Lu) series and the value is in the range between typical oxide anion conductors of yttria stabilized zirconia (YSZ) and calcia stabilized zirconia (CSZ). Since cerium ion has been demonstrated to be another migrating ion species in solid electrolyte field, a promising application for various functional materials is greatly expected.

  18. Electro-deposition of superconductor oxide films

    SciTech Connect

    Bhattacharya, Raghu N.

    2001-01-01

    Methods for preparing high quality superconducting oxide precursors which are well suited for further oxidation and annealing to form superconducting oxide films. The method comprises forming a multilayered superconducting precursor on a substrate by providing an electrodeposition bath comprising an electrolyte medium and a substrate electrode, and providing to the bath a plurality of precursor metal salts which are capable of exhibiting superconducting properties upon subsequent treatment. The superconducting precursor is then formed by electrodepositing a first electrodeposited (ED) layer onto the substrate electrode, followed by depositing a layer of silver onto the first electrodeposited (ED) layer, and then electrodepositing a second electrodeposited (ED) layer onto the Ag layer. The multilayered superconducting precursor is suitable for oxidation at a sufficient annealing temperature in air or an oxygen-containing atmosphere to form a crystalline superconducting oxide film.

  19. Mesoporous semiconducting oxide thin films with nanocrystalline walls: Synthesis, characterization, and applications

    NASA Astrophysics Data System (ADS)

    Frindell, Karen Lynne

    Mesoporous titania thin films were synthesized using a novel modified sol-gel method, which involves the inhibition of rapid condensative polymerization of hydrolyzed titanium alkoxide using concentrated acid solutions. Lamellar, 2D-hexagonal, and cubic mesostructures were created by varying the volume fraction of the structure-directing block copolymer in the precursor solution. A mesostructured cubic semiconducting framework made up of three-dimensionally arranged anatase nanocrystallites embedded in an amorphous titania matrix was obtained by heat treating the films. Interesting absorbance and photoluminescence properties were observed including a blue shifted band gap and well-defined photoluminescence peaks owing to the high surface area and unusual surface environment of the nanocrystallites present in the framework. Selected rare earth ions were included into the walls of the mesoporous titania thin films and excitation of the mesoporous titania in its band gap resulted in sensitized photoluminescence in the visible and near infrared regions of the spectrum. The energy transfer mechanism was determined in part by evaluating which rare earth ions exhibited photoluminescence via energy transfer. Mesoporous titania thin films were incorporated into several devices including a dye sensitized solar cell. The photocurrent, photovoltage and power conversion efficiency of several iterations of solar cell devices were tested. Electrochromic devices were also fabricated and tested using pure mesoporous titania films and those doped with cerium ions. Contrary to the behavior of non-porous Ce-TiO2 thin films, the addition of cerium to mesoporous titania films caused an increased electrochromic effect. The calcination temperature was varied to correlate the evolution of the structure of the titania thin films with optical and electrochemical properties. Electron microscopy, optical absorbance, photoluminescence, lithium insertion, chronoamperometry, and

  20. 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

  1. 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.

  2. A rapid solvothermal synthesis of cerium oxide hollow spheres and characterization

    SciTech Connect

    Kempaiah Devaraju, Murukanahally; Liu, Xiangwen; Yin, Shu; Sato, Tsugio

    2012-10-15

    An easy and size controlled solvothermal synthesis of CeO{sub 2} hollow spheres is still a challenge in the area of materials synthesis. Here, CeO{sub 2} hollow spheres have been synthesized using PVA500 as a surfactant via solvothermal reaction followed by calcinations. The size of CeO{sub 2} hollow spheres could be controlled from 500 to 150 nm by changing the amounts of Ce(NO{sub 3}){sub 3}{center_dot}6H{sub 2}O and PVA500. The possible growth mechanism of CeO{sub 2} hollow sphere was explained. The CO oxidation catalytic activity of the CeO{sub 2} hollow spheres were superior to that of the commercial CeO{sub 2} powder due to the high specific surface area and small crystallite size. - Graphical abstract: A rapid and easy way to prepare CeO{sub 2} hollow sphere with 150-500 nm in diameter was successfully achieved by solvothermal reaction. The prepared particles showed hollowness due to Ostwald ripening process. An improved catalytic activity was observed and discussed. Highlights: A rapid synthesis of CeO{sub 2} hollow spheres with diameter size from 15 to 500 nm. Black-Right-Pointing-Pointer Cheap surfactant was used to prepare hollow spheres. Black-Right-Pointing-Pointer Effect of temperature and surfactant ratio were investigated. Black-Right-Pointing-Pointer Systematic characterization by XRD, FESEM, TEM, TG, FTIR and UV. Black-Right-Pointing-Pointer CO oxidation analysis results showed better catalytic activity.

  3. Electrodeposition of silver(II) oxide films

    SciTech Connect

    Breyfogle, B.E.; Hung, C.J.; Shumsky, M.G.; Switzer, J.A.

    1996-09-01

    AgO has been studied extensively for its use as the cathode material in zinc-silver oxide batteries. Continuous films of silver(II) oxide (AgO) have been electrodeposited directly from aqueous solutions of 50 mM silver acetate/25 mM sodium acetate onto 430 stainless steel, polycrystalline platinum, and indium-tin oxide-coated glass. Current efficiencies for the electrodeposition process ranged from 62 to 95% and were a function of the applied current density. X-ray diffraction of the electrodeposited films reveals a [010] texture when the thickness is greater than 1 {micro}m. Freshly ground films or powders exhibit only reflections consistent with the monoclinic AgO structure. Rietveld analysis confirms the ground films are single-phase AgO with a P 2{sub 1}/c space group. The films were imaged and film thickness was measured by atomic force microscopy. Thermogravimetric analysis shows that the films begin to decompose in air above 130 C, with an abrupt weight loss between 180 and 200 C. The total weight loss of 6.4 to 6.5% corresponds to thermal decomposition of AgO to Ag{sub 2}O with loss of oxygen. A direct optical bandgap of 1.1 eV was measured. The black AgO films absorb strongly in the near infrared and throughout the visible region. The four-point resistivity of the AgO films was 12 {+-} 1 {Omega} cm.

  4. Graphene oxide film as solid lubricant.

    PubMed

    Liang, Hongyu; Bu, Yongfeng; Zhang, Junyan; Cao, Zhongyue; Liang, Aimin

    2013-07-10

    As a layered material, graphene oxide (GO) film is a good candidate for improving friction and antiwear performance of silicon-based MEMS devices. Via a green electrophoretic deposition (EPD) approach, GO films with tunable thickness in nanoscale are fabricated onto silicon wafer in a water solution. The morphology, microstructure, and mechanical properties as well as the friction coefficient and wear resistance of the films were investigated. The results indicated that the friction coefficient of silicon wafer was reduced to 1/6 its value, and the wear volume was reduced to 1/24 when using GO film as solid lubricant. These distinguished tribology performances suggest that GO films are expected to be good solid lubricants for silicon-based MEMS/NEMS devices. PMID:23786494

  5. Cerium oxidation state in silicate melts: Combined fO2, temperature and compositional effects

    NASA Astrophysics Data System (ADS)

    Smythe, Duane J.; Brenan, James M.

    2015-12-01

    To quantify the relative proportions of Ce3+ and Ce4+ in natural magmas, we have synthesized a series of Ce doped glasses ranging in composition from basalt to rhyolite (±H2O) at 0.001 and 1 GPa, under fO2 conditions varying from FMQ -4.0 to FMQ +8.4, and temperatures from 1200 to 1500 °C. The Ce4+/Ce3+ ratio in the experimental run products was determined both potentiometrically and in situ, using Ce M4,5-edge X-ray absorption near-edge structure (XANES) spectroscopy. For a given melt composition, the change in Ce4+/Ce3+ ratio with fO2 follows the trend predicted from the reaction stoichiometry assuming simple oxides as melt species. In addition to fO2, melt composition and water content have been found to be secondary controls on Ce4+/Ce3+, with more depolymerized melts and hydrous compositions favoring the stabilization of Ce3+. The Ce4+/Ce3+ ratio can be expressed through the equation,

  6. High quality transparent conducting oxide thin films

    DOEpatents

    Gessert, Timothy A.; Duenow, Joel N.; Barnes, Teresa; Coutts, Timothy J.

    2012-08-28

    A transparent conducting oxide (TCO) film comprising: a TCO layer, and dopants selected from the elements consisting of Vanadium, Molybdenum, Tantalum, Niobium, Antimony, Titanium, Zirconium, and Hafnium, wherein the elements are n-type dopants; and wherein the transparent conducting oxide is characterized by an improved electron mobility of about 42 cm.sup.2/V-sec while simultaneously maintaining a high carrier density of .about.4.4e.times.10.sup.20 cm.sup.-3.

  7. 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.

  8. 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.

  9. Patterning of Indium Tin Oxide Films

    NASA Technical Reports Server (NTRS)

    Immer, Christopher

    2008-01-01

    A relatively rapid, economical process has been devised for patterning a thin film of indium tin oxide (ITO) that has been deposited on a polyester film. ITO is a transparent, electrically conductive substance made from a mixture of indium oxide and tin oxide that is commonly used in touch panels, liquid-crystal and plasma display devices, gas sensors, and solar photovoltaic panels. In a typical application, the ITO film must be patterned to form electrodes, current collectors, and the like. Heretofore it has been common practice to pattern an ITO film by means of either a laser ablation process or a photolithography/etching process. The laser ablation process includes the use of expensive equipment to precisely position and focus a laser. The photolithography/etching process is time-consuming. The present process is a variant of the direct toner process an inexpensive but often highly effective process for patterning conductors for printed circuits. Relative to a conventional photolithography/ etching process, this process is simpler, takes less time, and is less expensive. This process involves equipment that costs less than $500 (at 2005 prices) and enables patterning of an ITO film in a process time of less than about a half hour.

  10. 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. PMID:26744830

  11. 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.

  12. Aluminum oxide film thickness and emittance

    SciTech Connect

    Thomas, J.K.; Ondrejcin, R.S.

    1991-11-01

    Aluminum reactor components which are not actively cooled could be subjected to high temperatures due to gamma heating after the core coolant level dropped during the ECS phase of a hypothetical LOCA event. Radiative heat transfer is the dominant heat transfer process in this scenario and therefore the emittance of these components is of interest. Of particular interest are the safety rod thimbles and Mark 60B blanket assemblies; for the K Reactor, these components have been exposed to low temperature (< 55{degrees}C) moderator for about a year. The average moderator temperature was assumed to be 30{degrees}C. The Al oxide film thickness at this temperature, after one year of exposure, is predicted to be 6.4 {mu}m {plus minus} 10%; insensitive to exposure time. Dehydration of the film during the gamma heating accident would result in a film thickness of 6.0 {mu}m {plus minus} 11%. Total hemispherical emittance is predicted to be 0.69 at 96{degrees}C, decreasing to 0.45 at 600{degrees}C. Some phenomena which would tend to yield thicker oxide films in the reactor environment relative to those obtained under experimental conditions were neglected and the predicted film thickness values are therefore conservative. The emittance values predicted for a given film thickness are also conservative. The conservativisms inherent in the predicted emittance are particularly relevant for uncertainty analysis of temperatures generated using these values.

  13. Aluminum oxide film thickness and emittance

    SciTech Connect

    Thomas, J.K.; Ondrejcin, R.S.

    1991-11-01

    Aluminum reactor components which are not actively cooled could be subjected to high temperatures due to gamma heating after the core coolant level dropped during the ECS phase of a hypothetical LOCA event. Radiative heat transfer is the dominant heat transfer process in this scenario and therefore the emittance of these components is of interest. Of particular interest are the safety rod thimbles and Mark 60B blanket assemblies; for the K Reactor, these components have been exposed to low temperature (< 55{degrees}C) moderator for about a year. The average moderator temperature was assumed to be 30{degrees}C. The Al oxide film thickness at this temperature, after one year of exposure, is predicted to be 6.4 {mu}m {plus_minus} 10%; insensitive to exposure time. Dehydration of the film during the gamma heating accident would result in a film thickness of 6.0 {mu}m {plus_minus} 11%. Total hemispherical emittance is predicted to be 0.69 at 96{degrees}C, decreasing to 0.45 at 600{degrees}C. Some phenomena which would tend to yield thicker oxide films in the reactor environment relative to those obtained under experimental conditions were neglected and the predicted film thickness values are therefore conservative. The emittance values predicted for a given film thickness are also conservative. The conservativisms inherent in the predicted emittance are particularly relevant for uncertainty analysis of temperatures generated using these values.

  14. Thin-Film Solid Oxide Fuel Cells

    NASA Technical Reports Server (NTRS)

    Chen, Xin; Wu, Nai-Juan; Ignatiev, Alex

    2009-01-01

    The development of thin-film solid oxide fuel cells (TFSOFCs) and a method of fabricating them have progressed to the prototype stage. This can result in the reduction of mass, volume, and the cost of materials for a given power level.

  15. Metal current collect protected by oxide film

    DOEpatents

    Jacobson, Craig P.; Visco, Steven J.; DeJonghe, Lutgard C.

    2004-05-25

    Provided are low-cost, mechanically strong, highly electronically conductive current collects and associated structures for solid-state electrochemical devices, techniques for forming these structures, and devices incorporating the structures. The invention provides solid state electrochemical devices having as current interconnects a ferritic steel felt or screen coated with a protective oxide film.

  16. Exposure to Cerium Oxide Nanoparticles Is Associated With Activation of Mitogen-activated Protein Kinases Signaling and Apoptosis in Rat Lungs

    PubMed Central

    Rice, Kevin M.; Nalabotu, Siva K.; Manne, Nandini D.P.K.; Kolli, Madhukar B.; Nandyala, Geeta; Arvapalli, Ravikumar; Ma, Jane Y.; Blough, Eric R.

    2015-01-01

    Objectives: With recent advances in nanoparticle manufacturing and applications, potential exposure to nanoparticles in various settings is becoming increasing likely. No investigation has yet been performed to assess whether respiratory tract exposure to cerium oxide (CeO2) nanoparticles is associated with alterations in protein signaling, inflammation, and apoptosis in rat lungs. Methods: Specific-pathogen-free male Sprague-Dawley rats were instilled with either vehicle (saline) or CeO2 nanoparticles at a dosage of 7.0 mg/kg and euthanized 1, 3, 14, 28, 56, or 90 days after exposure. Lung tissues were collected and evaluated for the expression of proteins associated with inflammation and cellular apoptosis. Results: No change in lung weight was detected over the course of the study; however, cerium accumulation in the lungs, gross histological changes, an increased Bax to Bcl-2 ratio, elevated cleaved caspase-3 protein levels, increased phosphorylation of p38 MAPK, and diminished phosphorylation of ERK-1/2-MAPK were detected after CeO2 instillation (p<0.05). Conclusions: Taken together, these data suggest that high-dose respiratory exposure to CeO2 nanoparticles is associated with lung inflammation, the activation of signaling protein kinases, and cellular apoptosis, which may be indicative of a long-term localized inflammatory response. PMID:26081650

  17. Microheterogeneity of ruthenium oxide film anodes

    SciTech Connect

    Roginskaya, Yu.E.; Belova, I.D.; Galyamov, B.S.; Popkov, Yu.M.; Zakhar'in, D.S.

    1988-03-01

    Following an analysis of x-ray diffraction, differential thermal analysis, and infrared and x-ray photoelectron spectroscopy data for ruthenium hydroxide and ruthenium oxide films heat-treated at temperatures between 300 and 600 degrees C, the composition and structure of the ruthenium hydroxide was determined and it was shown that the ruthenium oxide film electrodes (up to 600 degrees C) are inhomogeneous in their composition and structure; they contain regions measuring 15-20 nm with long-rage order which in their composition and structure correspond to the anhydrous rutile phase of ruthenium dioxide, and amorphous regions identical with ruthenium hydroxide. The relation between the electrochemical behavior of the ruthenium oxide electrodes and the results obtained is discussed.

  18. Role of tetrachloromethane as a gas-phase additive in the oxidative dehydrogenation of propane over cerium oxide

    SciTech Connect

    Sugiyama, Shigeru; Iizuka, Y.; Nitta, E.; Hayashi, H.; Moffat, J.B.

    2000-01-01

    In the absence of tetrachloromethane (TCM) carbon dioxide is the principal product formed in the oxidation of propane on ceria. The introduction of small partial pressures of TCM increases the conversion of propane with selectivities to propene up to 80%. Except under special circumstances no evidence of chlorinated species from TCM is found in the bulk structure while the surface region is shown to contain chlorine, although its form is not known. The enhancement of conversion and selectivity to propene is shown to be dependent upon the presence of chlorine, in whatever form, in the surface region of the catalyst.

  19. Structural and Mechanical Characteristics of Anodic Oxide Films on Titanium

    SciTech Connect

    Pang, Mengzhi; Eakins, Daniel E; Norton, Murray G; Bahr, David F

    2001-01-01

    Oxide films were grown electrochemically on polycrystalline titanium in 0.1 M sulfuric acid (H2SO4) from open-circuit potential to a final potential of 9.4 V (vs silver-silver chloride [Ag-AgCl]) using three anodization rates: a step polarization, growth at 200 mV/s, and growth at 1 mV/s. Anodic polarization curves showed various degrees of oxygen evolution above 5.4 VAg-AgCl, indicating that the extent of oxide film breakdown depends on film growth rate, with slower growth rates undergoing more severe film breakdown. In-situ characterization of mechanical behavior of oxide films by nanoindentation revealed that the oxide film can sustain a tensile stress up to 2.5 GPa prior to film fracture. Among these three anodization rates, the oxide film formed by step polarization exhibited the highest film-strengthening effect. At applied potentials prior to oxide film breakdown, all films exhibited a strength of ≈1 GPa. The films ranged from amorphous titanium dioxide (TiO2) to anatase, with the extent of crystallization increasing with decreasing film growth rate. Correlations between electrochemical polarization, structural characteristics, and the mechanical behavior of these anodic films are discussed in relationship to electrostrictive stresses, which may lead to the breakdown of passive films. KEY WORDS: anodic polarization, films, nanoindentation, titanium, transmission electron microscopy.

  20. 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

  1. Interfacial Assembly of Graphene Oxide Films

    NASA Astrophysics Data System (ADS)

    Valtierrez, Cain; Ismail, Issam; Macosko, Christopher; Stottrup, Benjamin

    Controlled assembly of monolayer graphene-oxide (GO) films at the air/water interface is of interest for the development of transparent conductive thin films of chemically-derived graphene. We present experimental results from investigations of the assembly of polydisperse GO sheets at the air-water interface. GO nanosheets with lateral dimensions of greater than 10 microns were created using a modified Tour synthesis (Dimiev and Tour, 2014). GO films were generated with conventional Langmuir trough techniques to control lateral packing density. Film morphology was characterized in situ with Brewster angle microscopy. Films were transferred unto a substrate via the Langmuir-Blodgett deposition technique and imaged with fluorescence quenching microscopy. Through pH modulation of the aqueous subphase, it was found that GO's intrinsic surface activity to the interface increased with increasing subphase acidity. Finally, we found a dominant elastic contribution during uniaxial film deformation as measured by anisotropic pressure measurements. A. M. Dimiev, and J. M. Tour, ``Mechanism of GO Formation,'' ACS Nano, 8, (2014)

  2. High-permitivity cerium oxide prepared by molecular beam deposition as gate dielectric and passivation layer and applied to AlGaN/GaN power high electron mobility transistor devices

    NASA Astrophysics Data System (ADS)

    Chiu, Yu Sheng; Liao, Jen Ting; Lin, Yueh Chin; Chien Liu, Shin; Lin, Tai Ming; Iwai, Hiroshi; Kakushima, Kuniyuki; Chang, Edward Yi

    2016-05-01

    High-κ cerium oxide (CeO2) was applied to AlGaN/GaN high-electron-mobility transistors (HEMTs) as a gate insulator and a passivation layer by molecular beam deposition (MBD) for high-power applications. From capacitance-voltage (C-V) measurement results, the dielectric constant of the CeO2 film was 25.2. The C-V curves showed clear accumulation and depletion behaviors with a small hysteresis (20 mV). Moreover, the interface trap density (D it) was calculated to be 5.5 × 1011 eV-1 cm-2 at 150 °C. A CeO2 MOS-HEMT was fabricated and demonstrated a low subthreshold swing (SS) of 87 mV/decade, a high ON/OFF drain current ratio (I ON/I OFF) of 1.14 × 109, and a low gate leakage current density (J leakage) of 2.85 × 10-9 A cm-2 with an improved dynamic ON-resistance (R ON), which is about one order of magnitude lower than that of a conventional HEMT.

  3. Stability of Commercial Small-Sized Cerium Oxide in the Presence of Biological Material: Dilucidating Relationships between Reactivity and Toxicity of Nanomaterials

    NASA Astrophysics Data System (ADS)

    Cervini-Silva, J.; Gilbert, B.; Fernandez-Lomelin, P.; Guzman-Mendoza, J.; Chavira, E.

    2007-05-01

    Cerium is the most abundant lanthanide and generally the only one to undergo redox reactions at the Earth's surface. Although rarely studied in natural environments, the redox chemistry of cerium may regulate metal toxicity. Unlike Ce(III) or other lanthanide ions, Ce(IV) has shown a remarkably efficacy to hydrolyze DNA. While Ce(IV) has been recognized as an important candidate to occupy peptidases catalytic centers, Ce(III) is virtually inactive for peptide hydrolysis. The selectivity of Ce as Ce(IV) relates to the specific coordination of water molecules and their orientation. Ce(IV) may bind selectivity to biomolecules to instigate conformation changes or cleavage of complexes, which affect metabolic pathways pivotal to growth and survival. For instance, Ce(IV) promotes the selective cleavage of RNA-type substrates, cyclic monophosphates, peptides, or monocleotides such as AMP, leading to mixtures of nucleosides and nucleobases. Association constants for Ce(IV)-DNA complexes are reported to be higher in magnitude for single stranded than double stranded DNA, while cleavage rates for either complexes are comparable. Complexation of Ce(IV) with mitoxantrone results in the intercalation of such complex into DNA, enabling mitoxantrone to bind effectively with DNA, along with concomitant conformational changes in the DNA double helix and inhibition of DNA synthesis. To the authors' knowledge, however, little information is available on the reactivity as it relates to toxicity of Ce-bearing nanoparticles widely used in nanotechnological applications. Here, we study molecular interactions between small-sized CeO2 and biomolecules(e.g., DNA, RNA, proteins) using carbon and cerium spectroscopy. Suspension stability as determined by aggregation kinetics was studied by Dynamic Light Scattering (DSL) and UV. In addition, acidophiles and fungi cultures were analyzed by nephelometry to estimate population density and growth rate values. Results show a progressive increase in

  4. Influence of doping with third group oxides on properties of zinc oxide thin films

    SciTech Connect

    Palimar, Sowmya Bangera, Kasturi V.; Shivakumar, G. K.

    2013-03-15

    The study of modifications in structural, optical and electrical properties of vacuum evaporated zinc oxide thin films on doping with III group oxides namely aluminum oxide, gallium oxide and indium oxide are reported. It was observed that all the films have transmittance ranging from 85 to 95%. The variation in optical properties with dopants is discussed. On doping the film with III group oxides, the conductivity of the films showed an excellent improvement of the order of 10{sup 3} {Omega}{sup -1} cm{sup -1}. The measurements of activation energy showed that all three oxide doped films have 2 donor levels below the conduction band.

  5. Novel sol-gel synthesis of cerium-doped ZnO thin films for photocatalytic activity

    SciTech Connect

    Senthilvelan, S.; Chandraboss, V. L.; Karthikeyan, B.; Murugavelu, M.; Loganathan, B.; Natanapatham, L.

    2012-07-23

    The Ce-doped ZnO films on silica glass plates were prepared by sol-gel dip coating technique. The surface morphology of thin films was characterized by means of scanning electron microscopy (SEM). Optical properties of films have been investigated using UV-visible spectroscopy. The photocatalytic activity was established by testing the degradation of Alizarin Red (AR) from aqueous solution. The test of photocatalytic activity of the heat-treated Ce-doped ZnO films were also carried out under visible light irradiation.

  6. Metallic oxide switches using thick film technology

    NASA Technical Reports Server (NTRS)

    Patel, D. N.; Williams, L., Jr.

    1974-01-01

    Metallic oxide thick film switches were processed on alumina substrates using thick film technology. Vanadium pentoxide in powder form was mixed with other oxides e.g., barium, strontium copper and glass frit, ground to a fine powder. Pastes and screen printable inks were made using commercial conductive vehicles and appropriate thinners. Some switching devices were processed by conventional screen printing and firing of the inks and commercial cermet conductor terminals on 96% alumina substrates while others were made by applying small beads or dots of the pastes between platinum wires. Static, and dynamic volt-ampere, and pulse tests indicate that the switching and self-oscillatory characteristics of these devices could make them useful in memory element, oscillator, and automatic control applications.

  7. Galvanostatic Ion Detrapping Rejuvenates Oxide Thin Films.

    PubMed

    Arvizu, Miguel A; Wen, Rui-Tao; Primetzhofer, Daniel; Klemberg-Sapieha, Jolanta E; Martinu, Ludvik; Niklasson, Gunnar A; Granqvist, Claes G

    2015-12-01

    Ion trapping under charge insertion-extraction is well-known to degrade the electrochemical performance of oxides. Galvanostatic treatment was recently shown capable to rejuvenate the oxide, but the detailed mechanism remained uncertain. Here we report on amorphous electrochromic (EC) WO3 thin films prepared by sputtering and electrochemically cycled in a lithium-containing electrolyte under conditions leading to severe loss of charge exchange capacity and optical modulation span. Time-of-flight elastic recoil detection analysis (ToF-ERDA) documented pronounced Li(+) trapping associated with the degradation of the EC properties and, importantly, that Li(+) detrapping, caused by a weak constant current drawn through the film for some time, could recover the original EC performance. Thus, ToF-ERDA provided direct and unambiguous evidence for Li(+) detrapping. PMID:26599729

  8. Water clustering on nanostructured iron oxide films

    NASA Astrophysics Data System (ADS)

    Merte, Lindsay R.; Bechstein, Ralf; Peng, Guowen; Rieboldt, Felix; Farberow, Carrie A.; Zeuthen, Helene; Knudsen, Jan; Lægsgaard, Erik; Wendt, Stefan; Mavrikakis, Manos; Besenbacher, Flemming

    2014-06-01

    The adhesion of water to solid surfaces is characterized by the tendency to balance competing molecule-molecule and molecule-surface interactions. Hydroxyl groups form strong hydrogen bonds to water molecules and are known to substantially influence the wetting behaviour of oxide surfaces, but it is not well-understood how these hydroxyl groups and their distribution on a surface affect the molecular-scale structure at the interface. Here we report a study of water clustering on a moiré-structured iron oxide thin film with a controlled density of hydroxyl groups. While large amorphous monolayer islands form on the bare film, the hydroxylated iron oxide film acts as a hydrophilic nanotemplate, causing the formation of a regular array of ice-like hexameric nanoclusters. The formation of this ordered phase is localized at the nanometre scale; with increasing water coverage, ordered and amorphous water are found to coexist at adjacent hydroxylated and hydroxyl-free domains of the moiré structure.

  9. Water Clustering on Nanostructured Iron Oxide Films

    SciTech Connect

    Merte, L. R.; Bechstein, Ralf; Peng, Guowen; Rieboldt, Felix; Farberow, Carrie A.; Zeuthen, Helene; Knudsen, Jan; Laegsgaard, E.; Wendt, Stefen; Mavrikakis, Manos; Besenbacher, Fleming

    2014-06-30

    The adhesion of water to solid surfaces is characterized by the tendency to balance competing molecule–molecule and molecule–surface interactions. Hydroxyl groups form strong hydrogen bonds to water molecules and are known to substantially influence the wetting behaviour of oxide surfaces, but it is not well-understood how these hydroxyl groups and their distribution on a surface affect the molecular-scale structure at the interface. Here we report a study of water clustering on a moire´-structured iron oxide thin film with a controlled density of hydroxyl groups. While large amorphous monolayer islands form on the are film, the hydroxylated iron oxide film acts as a hydrophilic nanotemplate, causing the formation of a regular array of ice-like hexameric nanoclusters. The formation of this ordered phase is localized at the nanometre scale; with increasing water coverage, ordered and amorphous water are found to coexist at adjacent hydroxylated and hydroxyl-free domains of the moire´ structure.

  10. 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.

  11. 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.

  12. 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. PMID:26239283

  13. Comparative study of structural, optical and impedance measurements on V{sub 2}O{sub 5} and V-Ce mixed oxide thin films

    SciTech Connect

    Malini, D. Rachel; Sanjeeviraja, C.

    2015-06-24

    Vanadium pentoxide (V{sub 2}O{sub 5}) and Vanadium-Cerium mixed oxide thin films at different molar ratios of V{sub 2}O{sub 5} and CeO{sub 2} have been deposited at 200 W rf power by rf planar magnetron sputtering in pure argon atmosphere. The structural and optical properties were studied by taking X-ray diffraction and transmittance and absorption spectra respectively. The amorphous thin films show an increase in transmittance and optical bandgap with increase in CeO{sub 2} content in as-prepared thin films. The impedance measurements for as-deposited thin films show an increase in electrical conductivity with increase in CeO{sub 2} material.

  14. Thin zinc oxide and cuprous oxide films for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Jeong, Seongho

    Metal oxide semiconductors and heterojunctions made from thin films of metal oxide semiconductors have broad range of functional properties and high potential in optical, electrical and magnetic devices such as light emitting diodes, spintronic devices and solar cells. Among the oxide semiconductors, zinc oxide (ZnO) and cuprous oxide (Cu2O) are attractive because they are inexpensive, abundant and nontoxic. As synthesized ZnO is usually an intrinsic n - type semiconductor with wide band gap (3.4 eV) and can be used as the transparent conducting window layer in solar cells. As synthesized Cu2O is usually a p - type semiconductor with a band gap of 2.17 eV and has been considered as a potential material for the light absorbing layer in solar cells. I used various techniques including metal organic chemical vapor deposition, magnetron sputtering and atomic layer deposition to grow thin films of ZnO and Cu2O and fabricated Cu2O/ZnO heterojunctions. I specifically investigated the optical and electrical properties of Cu 2O thin films deposited on ZnO by MOCVD and showed that Cu2O thin films grow as single phase with [110] axis aligned perpendicular to the ZnO surface which is (0001) plane and with in-plane rotational alignment due to (220) Cu2O || (0002)ZnO; [001]Cu2O || [12¯10]ZnO epitaxy. Moreover, I fabricated solar cells based on these Cu2O/ZnO heterojunctions and characterized them. Electrical characterization of these solar cells as a function of temperature between 100 K and 300 K under illumination revealed that interface recombination and tunneling at the interface are the factors that limit the solar cell performance. To date solar cells based on Cu2O/ZnO heterojunctions had low open circuit voltages (~ 0.3V) even though the expected value is around 1V. I achieved open circuit voltages approaching 1V at low temperature (~ 100 K) and showed that if interfacial recombination is reduced these cells can achieve their predicted potential.

  15. 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.

  16. 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

  17. Mechanism for Limiting Thickness of Thin Oxide Films on Aluminum

    NASA Astrophysics Data System (ADS)

    Baran, Jakub D.; Grönbeck, Henrik; Hellman, Anders

    2014-04-01

    A first-principles account of the observed limiting thickness of oxide films formed on aluminum during oxidizing conditions is presented. The results uncover enhanced bonding of oxygen to thin alumina films in contact with metallic aluminum that stems from charge transfer between a reconstructed oxide-metal interface and the adsorbed molecules. The first-principles results are compared with the traditional Cabrera-Mott (CM) model, which is a classical continuum model. Within the CM model, charged surface oxygen species and metal ions generate a (Mott) potential that drives oxidation. An apparent limiting thickness is observed as the oxidation rate decreases rapidly with film growth. The present results support experimental estimates of the Mott potential and film thicknesses. In contrast to the CM model, however, the calculations reveal a real limiting thickness that originates from a diminishing oxygen adsorption energy beyond a certain oxide film thickness.

  18. Dysprosium oxide and dysprosium-oxide-doped titanium oxide thin films grown by atomic layer deposition

    SciTech Connect

    Tamm, Aile Kozlova, Jekaterina; Aarik, Lauri; Aarik, Jaan; Kukli, Kaupo; Link, Joosep; Stern, Raivo

    2015-01-15

    Dysprosium oxide and dysprosium-oxide-doped titanium oxide thin films were grown by atomic layer deposition on silicon substrates. For depositing dysprosium and titanium oxides Dy(thd){sub 3}-O{sub 3} and TiCl{sub 4}-O{sub 3} were used as precursors combinations. Appropriate parameters for Dy(thd){sub 3}-O{sub 3} growth process were obtained by using a quartz crystal microbalance system. The Dy{sub 2}O{sub 3} films were deposited on planar substrates and on three-dimensional substrates with aspect ratio 1:20. The Dy/Ti ratio of Dy{sub 2}O{sub 3}-doped TiO{sub 2} films deposited on a planar silicon substrate ranged from 0.04 to 0.06. Magnetometry studies revealed that saturation of magnetization could not be observed in planar Dy{sub 2}O{sub 3} films, but it was observable in Dy{sub 2}O{sub 3} films on 3D substrates and in doped TiO{sub 2} films with a Dy/Ti atomic ratio of 0.06. The latter films exhibited saturation magnetization 10{sup −6} A cm{sup 2} and coercivity 11 kA/m at room temperature.

  19. Fabrication of nanostructured metal oxide films with supercritical carbon dioxide: Processing and applications

    NASA Astrophysics Data System (ADS)

    You, Eunyoung

    was performed thereafter. Subsequent calcination of the samples at high temperature of 400 °C revealed TiO2 nanochannels. H2-assisted-codeposition of Pt and cerium oxide using SFD was performed on porous carbon substrates for their use as anodes for direct methanol fuel cells. X-ray photoelectron analysis revealed that Pt was deposited as a pure metal and Ce was deposited as an oxide. Electrochemical analysis of a full cell revealed that an anode prepared with SFD exhibited better performance than that prepared with conventional brush-painting method. The second process that was developed is a direct spray-on technique to rapidly deposit crystalline nanoscale dendritic TiO2 onto a solid surface. This technique employs atomization of precursor solutions in supercritical fluids combined with the plasma thermal spraying. A solution of metal oxide precursor in scCO2 was expanded across a nozzle into the plasma jet where it is converted to metal oxide. We have investigated TiO2 as our model system using titanium tetra isopropoxide (Ttip) as a precursor. The film structure depends on key process variables including precursor concentration, precursor solution flow rate and plasma gun to substrate distance. The high surface area of the deposited films is attractive for applications in photovoltaics and we have fabricated dye-sensitized solar cells using these films.

  20. Study of the formation process of titanium oxides containing micro arc oxidation film on Mg alloys

    NASA Astrophysics Data System (ADS)

    Song, Yingwei; Dong, Kaihui; Shan, Dayong; Han, En-Hou

    2014-09-01

    A novel micro arc oxidation (MAO) film is developed to protect Mg alloys from corrosion. This film contains plenty of titanium oxides, which exhibits higher chemical stability than traditional MAO films. Especially, the micropores on the surface of the film are in situ sealed during the film formation process instead of the sealing pores post treatment. The film formation process is investigated by the observation of surface and cross-section morphologies and analysis of chemical composition. It is found that the sizes of micropores increase but the quantities decrease with increasing oxidation voltages. The micropores are open in the initial stage of oxidation and then they are sealed gradually. The growth direction of the film takes place change at different oxidation voltages. The elements of F and Ti play a significant role in the film growth process.

  1. 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. PMID:25439500

  2. Methane Activation Mediated by a Series of Cerium-Vanadium Bimetallic Oxide Cluster Cations: Tuning Reactivity by Doping.

    PubMed

    Ma, Jia-Bi; Meng, Jing-Heng; He, Sheng-Gui

    2016-04-18

    The reactions of cerium-vanadium cluster cations Cex Vy Oz (+) with CH4 are investigated by time-of-flight mass spectrometry and density functional theory calculations. (CeO2 )m (V2 O5 )n (+) clusters (m=1,2, n=1-5; m=3, n=1-4) with dimensions up to nanosize can abstract one hydrogen atom from CH4 . The theoretical study indicates that there are two types of active species in (CeO2 )m (V2 O5 )n (+) , V[(Ot )2 ](.) and [(Ob )2 CeOt ](.) (Ot and Ob represent terminal and bridging oxygen atoms, respectively); the former is less reactive than the latter. The experimentally observed size-dependent reactivities can be rationalized by considering the different active species and mechanisms. Interestingly, the reactivity of the (CeO2 )m (V2 O5 )n (+) clusters falls between those of (CeO2 )2-4 (+) and (V2 O5 )1-5 (+) in terms of C-H bond activation, thus the nature of the active species and the cluster reactivity can be effectively tuned by doping.

  3. 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.

  4. Methane Activation Mediated by a Series of Cerium-Vanadium Bimetallic Oxide Cluster Cations: Tuning Reactivity by Doping.

    PubMed

    Ma, Jia-Bi; Meng, Jing-Heng; He, Sheng-Gui

    2016-04-18

    The reactions of cerium-vanadium cluster cations Cex Vy Oz (+) with CH4 are investigated by time-of-flight mass spectrometry and density functional theory calculations. (CeO2 )m (V2 O5 )n (+) clusters (m=1,2, n=1-5; m=3, n=1-4) with dimensions up to nanosize can abstract one hydrogen atom from CH4 . The theoretical study indicates that there are two types of active species in (CeO2 )m (V2 O5 )n (+) , V[(Ot )2 ](.) and [(Ob )2 CeOt ](.) (Ot and Ob represent terminal and bridging oxygen atoms, respectively); the former is less reactive than the latter. The experimentally observed size-dependent reactivities can be rationalized by considering the different active species and mechanisms. Interestingly, the reactivity of the (CeO2 )m (V2 O5 )n (+) clusters falls between those of (CeO2 )2-4 (+) and (V2 O5 )1-5 (+) in terms of C-H bond activation, thus the nature of the active species and the cluster reactivity can be effectively tuned by doping. PMID:26714587

  5. High carrier concentration p-type transparent conducting oxide films

    DOEpatents

    Yan, Yanfa; Zhang, Shengbai

    2005-06-21

    A p-type transparent conducting oxide film is provided which is consisting essentially of, the transparent conducting oxide and a molecular doping source, the oxide and doping source grown under conditions sufficient to deliver the doping source intact onto the oxide.

  6. Doping in zinc oxide thin films

    NASA Astrophysics Data System (ADS)

    Yang, Zheng

    Doping in zinc oxide (ZnO) thin films is discussed in this dissertation. The optimizations of undoped ZnO thin film growth using molecular-beam epitaxy (MBE) are discussed. The effect of the oxygen ECR plasma power on the growth rate, structural, electrical, and optical properties of the ZnO thin films were studied. It was found that larger ECR power leads to higher growth rate, better crystallinity, lower electron carrier concentration, larger resistivity, and smaller density of non-radiative luminescence centers in the ZnO thin films. Low-temperature photoluminescence (PL) measurements were carried out in undoped and Ga-doped ZnO thin films grown by molecular-beam epitaxy. As the carrier concentration increases from 1.8 x 1018 to 1.8 x 1020 cm-3, the dominant PL line at 9 K changes from I1 (3.368--3.371 eV), to IDA (3.317--3.321 eV), and finally to I8 (3.359 eV). The dominance of I1, due to ionized-donor bound excitons, is unexpected in n-type samples, but is shown to be consistent with the temperature-dependent Hall fitting results. We also show that IDA has characteristics of a donor-acceptor-pair transition, and use a detailed, quantitative analysis to argue that it arises from GaZn donors paired with Zn-vacancy (VZn) acceptors. In this analysis, the GaZn0/+ energy is well-known from two-electron satellite transitions, and the VZn0/- energy is taken from a recent theoretical calculation. Typical behaviors of Sb-doped p-type ZnO are presented. The Sb doping mechanisms and preference in ZnO are discussed. Diluted magnetic semiconducting ZnO:Co thin films with above room-temperature TC were prepared. Transmission electron microscopy and x-ray diffraction studies indicate the ZnO:Co thin films are free of secondary phases. The magnetization of the ZnO:Co thin films shows a free electron carrier concentration dependence, which increases dramatically when the free electron carrier concentration exceeds ˜1019 cm -3, indicating a carrier-mediated mechanism for

  7. CW laser compaction of aqueous solution deposited metal oxide films

    SciTech Connect

    Exarhos, G.J.; Dennis, T.

    1997-12-01

    Zirconium dioxide films were spin cast onto silica or silicon substrates from an aqueous solution comprised of the precursor metal nitrate and an organic complexant such as glycine. The hydrated films so derived consist of an amorphous organic phase in which the metal cations and nitrate anions are homogeneously dispersed. Heating to temperatures above 200 {degrees}C leads to film dehydration followed by an auto-catalyzed oxidation reaction whereby the bound nitrate oxidizes the organic matrix leaving behind an intact stoichiometric and crystalline metal oxide film. Films are characterized using AFM, XRD, and optical methods. Transformation processes in these films have been studied in detail by means of spectroscopic ellipsometry and laser induced fluorescence from films doped with a suitable rare earth probe ion such as SM{sup +3}. In the latter case, the measured fluorescence emission spectra are used to identify the hydrated, dehydrated, amorphous and crystalline metal oxide phases which evolve during processing. These transformations also have been induced upon visible CW laser irradiation at fluences in excess of 1 MW/cm{sup 2}. Under these conditions, the film dehydrates and compacts within the footprint of the incident laser beam rendering this region of the film water insoluble. Post irradiation washing of the film with water removes all vestiges of the film outside of the beam footprint suggesting a possible use of this technique for lithography applications. Films subjected to laser irradiation and post irradiation heating have been characterized with respect to thickness, phase composition, crystallite size and optical constants.

  8. p-type conduction in sputtered indium oxide films

    SciTech Connect

    Stankiewicz, Jolanta; Alcala, Rafael; Villuendas, Francisco

    2010-05-10

    We report p-type conductivity in intrinsic indium oxide (IO) films deposited by magnetron sputtering on fused quartz substrates under oxygen-rich ambient. Highly oriented (111) films were studied by x-ray diffraction, optical absorption, and Hall effect measurements. We fabricated p-n homojunctions on these films.

  9. Polymer-assisted aqueous deposition of metal oxide films

    DOEpatents

    Li, DeQuan; Jia, Quanxi

    2003-07-08

    An organic solvent-free process for deposition of metal oxide thin films is presented. The process includes aqueous solutions of necessary metal precursors and an aqueous solution of a water-soluble polymer. After a coating operation, the resultant coating is fired at high temperatures to yield optical quality metal oxide thin films.

  10. Effects of oxidative treatments on human hair keratin films.

    PubMed

    Fujii, T; Ito, Y; Watanabe, T; Kawasoe, T

    2012-01-01

    The effects of hydrogen peroxide and commercial bleach on hair and human hair keratin films were examined by protein solubility, scanning electron microscopy (SEM), immunofluorescence microscopy, immunoblotting, and Fourier-transform infrared spectroscopy. Protein solubility in solutions containing urea decreased when the keratin films were treated with hydrogen peroxide or bleach. Oxidative treatments promoted the urea-dependent morphological change by turning films from opaque to transparent in appearance. Immunofluorescence microscopy and immunoblotting showed that the oxidation of amino acids and proteins occurred due to the oxidative treatments, and such occurrence was more evident in the bleach-treated films than in the hydrogen peroxide-treated films. Compared with hair samples, the formation of cysteic acid was more clearly observed in the keratin films after the oxidative treatments.

  11. Effects of oxidative treatments on human hair keratin films.

    PubMed

    Fujii, T; Ito, Y; Watanabe, T; Kawasoe, T

    2012-01-01

    The effects of hydrogen peroxide and commercial bleach on hair and human hair keratin films were examined by protein solubility, scanning electron microscopy (SEM), immunofluorescence microscopy, immunoblotting, and Fourier-transform infrared spectroscopy. Protein solubility in solutions containing urea decreased when the keratin films were treated with hydrogen peroxide or bleach. Oxidative treatments promoted the urea-dependent morphological change by turning films from opaque to transparent in appearance. Immunofluorescence microscopy and immunoblotting showed that the oxidation of amino acids and proteins occurred due to the oxidative treatments, and such occurrence was more evident in the bleach-treated films than in the hydrogen peroxide-treated films. Compared with hair samples, the formation of cysteic acid was more clearly observed in the keratin films after the oxidative treatments. PMID:22487448

  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. Flexible electrostatic nanogenerator using graphene oxide film

    NASA Astrophysics Data System (ADS)

    Tian, He; Ma, Shuo; Zhao, Hai-Ming; Wu, Can; Ge, Jie; Xie, Dan; Yang, Yi; Ren, Tian-Ling

    2013-09-01

    Recently, graphene oxide (GO) super capacitors with ultra-high energy densities have received significant attention. In addition to their use in energy storage, GO capacitors might also have broad applications in renewable energy engineering, such as energy harvesting. Here, a flexible nanogenerator based on GO film is designed. A multilayer structure Al/PI/GO/PI/ITO is made on a flexible PET substrate. The GO nanogenerator could generate a peak voltage of 2 V with a current of 30 nA upon the repetitive application of a 15 N force with a frequency of 1 Hz. Moreover, the output voltage was increased to 34.4 V upon increasing the frequency of force application to 10 Hz. Compared with control samples, embedding GO film with a release structure into the device could significantly enhance the output voltage from 0.1 V to 2.0 V. The mechanism of our nanogenerator can be explained by an electrostatic effect, which is fundamentally different from that of previously reported piezoelectric and triboelectric generators. In this manuscript, we demonstrate flexible nanogenerators with large-area graphene based materials, which may open up new avenues of research with regard to applications in energy harvesting.Recently, graphene oxide (GO) super capacitors with ultra-high energy densities have received significant attention. In addition to their use in energy storage, GO capacitors might also have broad applications in renewable energy engineering, such as energy harvesting. Here, a flexible nanogenerator based on GO film is designed. A multilayer structure Al/PI/GO/PI/ITO is made on a flexible PET substrate. The GO nanogenerator could generate a peak voltage of 2 V with a current of 30 nA upon the repetitive application of a 15 N force with a frequency of 1 Hz. Moreover, the output voltage was increased to 34.4 V upon increasing the frequency of force application to 10 Hz. Compared with control samples, embedding GO film with a release structure into the device could

  14. Pulsed organometallic beam epitaxy of complex oxide films

    NASA Astrophysics Data System (ADS)

    Duray, S. J.; Buchholz, D. B.; Song, S. N.; Richeson, D. S.; Ketterson, J. B.; Marks, T. J.; Chang, R. P. H.

    1991-09-01

    The results are reported of a pulsed organometallic beam epitaxy (POMBE) process for growing complex oxide films at low background gas pressure and low substrate temperature using organometallic precursors in an oxygen plasma environment. The results show that POMBE can extend the capability of organometallic chemical vapor deposition to growing complex oxide films with high precision both in composition and structure without the need for post-deposition oxidation and heat treatments. The growth of phase-pure, highly oriented Y-Ba-Cu-O superconducting oxide films is given as an example. Similar to the pulsed laser deposition process, the POMBE method has the potential for in situ processing of multilayer structures.

  15. [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.

  16. Effects of pH and fulvic acids concentration on the stability of fulvic acids--cerium (IV) oxide nanoparticle complexes.

    PubMed

    Oriekhova, Olena; Stoll, Serge

    2016-02-01

    The behavior of cerium (IV) oxide nanoparticles has been first investigated at different pH conditions. The point of zero charge was determined as well as the stability domains using dynamic light scattering, nanoparticle tracking analysis and scanning electron microscopy. A baseline hydrodynamic diameter of 180 nm was obtained indicating that individual CeO2 nanoparticles are forming small aggregates. Then we analyzed the particle behavior at variable concentrations of fulvic acids for three different pH-electrostatic scenarios corresponding to positive, neutral and negative CeO2 surface charges. The presence of fulvic acids was found to play a key role on the CeO2 stability via the formation of electrostatic complexes. It was shown that a small amount of fulvic acids (2 mg L(-1)), representative of environmental fresh water concentrations, is sufficient to stabilize CeO2 nanoparticles (50 mg L(-1)). When electrostatic complexes are formed between negatively charged FAs and positively charged CeO2 NPs the stability of such complexes is obtained with time (up to 7 weeks) as well as in pH changing conditions. Based on zeta potential variations we also found that the fulvic acids are changing the CeO2 acid-base surface properties. Obtained results presented here constitute an important outcome in the domain of risk assessment, transformation and removal of engineered nanomaterials released into the environment. PMID:26347935

  17. Amorphous tin-cadmium oxide films and the production thereof

    SciTech Connect

    Li, Xiaonan; Gessert, Timothy A

    2013-10-29

    A tin-cadmium oxide film having an amorphous structure and a ratio of tin atoms to cadmium atoms of between 1:1 and 3:1. The tin-cadmium oxide film may have an optical band gap of between 2.7 eV and 3.35 eV. The film may also have a charge carrier concentration of between 1.times.10.sup.20 cm.sup.-3 and 2.times.10.sup.20 cm.sup.-3. The tin cadmium oxide film may also exhibit a Hall mobility of between 40 cm.sup.2V.sup.-1 s.sup.-1 and 60 cm.sup.2V.sup.-1 s.sup.-1. Also disclosed is a method of producing an amorphous tin-cadmium oxide film as described and devices using same.

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

    PubMed

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

    2016-07-28

    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.

  19. 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.

  20. The effects of ultra-thin cerium fluoride film as the anode buffer layer on the electrical characteristics of organic light emitting diodes

    NASA Astrophysics Data System (ADS)

    Lu, Hsin-Wei; Tsai, Cheng-Che; Hong, Cheng-Shong; Kao, Po-Ching; Juang, Yung-Der; Chu, Sheng-Yuan

    2016-11-01

    In this study, the efficiency of organic light-emitting diodes (OLEDs) was enhanced by depositing a CeF3film as an ultra-thin buffer layer between the indium tin oxide (ITO) electrode and α-naphthylphenylbiphenyldiamine (NPB) hole transport layer, with the structure configuration ITO/CeF3 (0.5, 1, and 1.5 nm)/α-naphthylphenylbiphenyl diamine (NPB) (40 nm)/tris(8-hydroxyquinoline) aluminum (Alq3) (60 nm)/lithium fluoride (LiF) (1 nm)/Al (150 nm). The enhancement mechanism was systematically investigated via several approaches. The X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy results revealed the formation of the UV-ozone treated CeF3 film. The work function increased from 4.8 eV (standard ITO electrode) to 5.22 eV (0.5-nm-thick UV-ozone treated CeF3 film deposited on the ITO electrode). The surface roughness of the UV-ozone treated CeF3 film was smoother than that of the standard ITO electrode. Further, the UV-ozone treated CeF3 film increased both the surface energy and polarity, as determined from contact angle measurements. In addition, admittance spectroscopy measurements showed an increased capacitance and conductance of the OLEDs. Accordingly, the turn-on voltage decreased from 4.2 V to 3.6 V at 1 mA/cm2, the luminance increased from 7588 cd/m2 to 24760 cd/m2, and the current efficiency increased from 3.2 cd/A to 3.8 cd/A when the 0.5-nm-thick UV-ozone treated CeF3 film was inserted into the OLEDs.

  1. Films based on oxidized starch and cellulose from barley.

    PubMed

    El Halal, Shanise Lisie Mello; Colussi, Rosana; Deon, Vinícius Gonçalves; Pinto, Vânia Zanella; Villanova, Franciene Almeida; Carreño, Neftali Lenin Villarreal; Dias, Alvaro Renato Guerra; Zavareze, Elessandra da Rosa

    2015-11-20

    Starch and cellulose fibers were isolated from grains and the husk from barley, respectively. Biodegradable films of native starch or oxidized starches and glycerol with different concentrations of cellulose fibers (0%, 10% and 20%) were prepared. The films were characterized by morphological, mechanical, barrier, and thermal properties. Cellulose fibers isolated from the barley husk were obtained with 75% purity and high crystallinity. The morphology of the films of the oxidized starches, regardless of the fiber addition, was more homogeneous as compared to the film of the native starch. The addition of cellulose fibers in the films increased the tensile strength and decreased elongation. The water vapor permeability of the film of oxidized starch with 20% of cellulose fibers was lower than the without fibers. However the films with cellulose fibers had the highest decomposition with the initial temperature and thermal stability. The oxidized starch and cellulose fibers from barley have a good potential for use in packaging. The addition of cellulose fibers in starch films can contribute to the development of films more resistant that can be applied in food systems to maintain its integrity.

  2. Virus removal by biogenic cerium.

    PubMed

    De Gusseme, Bart; Du Laing, Gijs; Hennebel, Tom; Renard, Piet; Chidambaram, Dev; Fitts, Jeffrey P; Bruneel, Els; Van Driessche, Isabel; Verbeken, Kim; Boon, Nico; Verstraete, Willy

    2010-08-15

    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(-1) bio-Ce. Given the fact that virus removal with 50 mg L(-1) Ce(III) as CeNO(3) was lower, the presence of the bacterial carrier matrix in bio-Ce significantly enhanced virus removal. PMID:20704235

  3. 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.

  4. Antimony promoted bismuth cerium molybdate catalysts

    SciTech Connect

    Brazdil, J.F.; Glaeser, L.C.; Grasselli, R.K.

    1990-05-01

    This patent describes an improvement in antimony-promoted bismuth cerium molybdate whereby the tendency of the catalyst to lose efectiveness over time is significantly reduced. This patent describes new catalysts which are also useful in other oxidation-type reactions such as the oxidation of acrolein and methacrolein to produce the corresponding unsaturated aldehydes and acids and the oxydehydrogenation of various olefins such as isoamylenes to produce the corresponding diolefins such as isoprene.

  5. Aerosol chemical vapor deposition of metal oxide films

    DOEpatents

    Ott, Kevin C.; Kodas, Toivo T.

    1994-01-01

    A process of preparing a film of a multicomponent metal oxide including: forming an aerosol from a solution comprised of a suitable solvent and at least two precursor compounds capable of volatilizing at temperatures lower than the decomposition temperature of said precursor compounds; passing said aerosol in combination with a suitable oxygen-containing carrier gas into a heated zone, said heated zone having a temperature sufficient to evaporate the solvent and volatilize said precursor compounds; and passing said volatilized precursor compounds against the surface of a substrate, said substrate having a sufficient temperature to decompose said volatilized precursor compounds whereby metal atoms contained within said volatilized precursor compounds are deposited as a metal oxide film upon the substrate is disclosed. In addition, a coated article comprising a multicomponent metal oxide film conforming to the surface of a substrate selected from the group consisting of silicon, magnesium oxide, yttrium-stabilized zirconium oxide, sapphire, or lanthanum gallate, said multicomponent metal oxide film characterized as having a substantially uniform thickness upon said FIELD OF THE INVENTION The present invention relates to the field of film coating deposition techniques, and more particularly to the deposition of multicomponent metal oxide films by aerosol chemical vapor deposition. This invention is the result of a contract with the Department of Energy (Contract No. W-7405-ENG-36).

  6. Low reflectance sputtered vanadium oxide thin films on silicon

    NASA Astrophysics Data System (ADS)

    Esther, A. Carmel Mary; Dey, Arjun; Rangappa, Dinesh; Sharma, Anand Kumar

    2016-07-01

    Vanadium oxide thin films on silicon (Si) substrate are grown by pulsed radio frequency (RF) magnetron sputtering technique at RF power in the range of 100-700 W at room temperature. Deposited thin films are characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques to investigate microstructural, phase, electronic structure and oxide state characteristics. The reflectance and transmittance spectra of the films and the Si substrate are recorded at the solar region (200-2300 nm) of the spectral window. Substantial reduction in reflectance and increase in transmittance is observed for the films grown beyond 200 W. Further, optical constants viz. absorption coefficient, refractive index and extinction coefficient of the deposited vanadium oxide films are evaluated.

  7. Formation of alumina-ceria mixed oxide in model systems

    NASA Astrophysics Data System (ADS)

    Skála, Tomáš; Tsud, Nataliya; Prince, Kevin C.; Matolín, Vladimír

    2011-02-01

    Interaction of aluminium with cerium oxide was studied by photoelectron spectroscopy of Al/CeO2(1 1 1) and CeO2/Al(1 1 1) model systems. It was found in both cases that metallic aluminium was immediately oxidized, CeO2 was partially reduced and a mixed oxide with cerium present as Ce3+ was formed. The compound is probably cerium aluminate CeAlO3 mixed with Al2O3 or Ce2O3. In both cases the intermixing was limited by the diffusion of aluminium into ceria. The excess of deposited material above this limit formed AlOx and CeO2 overlayers on the top of the mixed oxide + aluminate/CeO2 and mixed oxide + aluminate/Al films, respectively.

  8. 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.

  9. Method for producing high quality oxide films on substrates

    DOEpatents

    Ruckman, M.W.; Strongin, M.; Gao, Y.L.

    1993-11-23

    A method is described for providing an oxide film of a material on the surface of a substrate using a reactive deposition of the material onto the substrate surface in the presence of a solid or liquid layer of an oxidizing gas. The oxidizing gas is provided on the substrate surface in an amount sufficient to dissipate the latent heat of condensation occurring during deposition as well as creating a favorable oxidizing environment for the material. 4 figures.

  10. Method for producing high quality oxide films on substrates

    DOEpatents

    Ruckman, Mark W.; Strongin, Myron; Gao, Yong L.

    1993-01-01

    A method for providing an oxide film of a material on the surface of a substrate using a reactive deposition of the material onto the substrate surface in the presence of a solid or liquid layer of an oxidizing gas. The oxidizing gas is provided on the substrate surface in an amount sufficient to dissipate the latent heat of condensation occurring during deposition as well as creating a favorable oxidizing environment for the material.

  11. Partial oxidation of 4-tert-butyltoluene catalyzed by homogeneous cobalt and cerium acetate catalysts in the Br-/H2O2/acetic acid system: insights into selectivity and mechanism.

    PubMed

    van de Water, Leon G A; Kaza, Arati; Beattie, James K; Masters, Anthony F; Maschmeyer, Thomas

    2007-01-01

    The partial oxidation of 4-tert-butyltoluene to 4-tert-butylbenzaldehyde by hydrogen peroxide in glacial acetic acid, catalyzed by bromide ions in combination with cobalt(II) acetate or cerium(III) acetate, has been studied in detail. Based on the observed differences in reaction rates and product distributions for the different catalysts, a reaction mechanism involving two independent pathways is proposed. After the initial formation of a benzylic radical species, either oxidation of this intermediate by the metal catalyst or reaction with bromine generated in situ occurs, depending on which catalyst is used. The first pathway leads to the exclusive formation of 4-tert-butylbenzaldehyde, whereas reaction of the radical intermediate with bromine leads to formation of the observed side products 4-tert-butylbenzyl bromide and its hydrolysis and solvolysis products 4-tert-butylbenzyl alcohol and 4-tert-butylbenzyl acetate, respectively. The cobalt(II) catalysts Co(OAc)(2) and Co(acac)(2) are able to quickly oxidize the radical intermediate, thereby largely preventing the bromination reaction (i.e., side-product formation) from occurring, and yield the aldehyde product with 75-80 % selectivity. In contrast, the cerium catalyst studied here exhibits an aldehyde selectivity of around 50 % due to the competing bromination reaction. Addition of extra hydrogen peroxide leads to an increased product yield of 72 % (cerium(III) acetate) or 58 % (cobalt(II) acetate). Product inhibition and the presence of increasing amounts of water in the reaction mixture do not play a role in the observed low incremental yields.

  12. Novel cerium-tungsten mixed oxide catalyst for the selective catalytic reduction of NO(x) with NH3.

    PubMed

    Shan, Wenpo; Liu, Fudong; He, Hong; Shi, Xiaoyan; Zhang, Changbin

    2011-07-28

    A novel Ce-W mixed oxide catalyst prepared by homogeneous precipitation method presented nearly 100% NO(x) conversion in a wide temperature range from 250 to 425 °C for the selective catalytic reduction of NO(x) with NH(3) under an extremely high GHSV of 500,000 h(-1).

  13. 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.

  14. 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.

  15. Unidirectional oxide hetero-interface thin-film diode

    SciTech Connect

    Park, Youngmin; Lee, Eungkyu; Lee, Jinwon; Lim, Keon-Hee; Kim, Youn Sang

    2015-10-05

    The unidirectional thin-film diode based on oxide hetero-interface, which is well compatible with conventional thin-film fabrication process, is presented. With the metal anode/electron-transporting oxide (ETO)/electron-injecting oxide (EIO)/metal cathode structure, it exhibits that electrical currents ohmically flow at the ETO/EIO hetero-interfaces for only positive voltages showing current density (J)-rectifying ratio of ∼10{sup 5} at 5 V. The electrical properties (ex, current levels, and working device yields) of the thin-film diode (TFD) are systematically controlled by changing oxide layer thickness. Moreover, we show that the oxide hetero-interface TFD clearly rectifies an AC input within frequency (f) range of 10{sup 2} Hz < f < 10{sup 6} Hz, providing a high feasibility for practical applications.

  16. 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

  17. Two kinds of composite films: Graphene oxide/carbon nanotube film and graphene oxide/activated carbon film via a self-assemble preparation process

    NASA Astrophysics Data System (ADS)

    Zou, Li-feng; Ma, Nan; Sun, Mei; Ji, Tian-hao

    2014-11-01

    Two kinds of free-standing composite films, including graphene oxide and activated carbon film as well as graphene oxide and carbon nanotube film, were fabricated through a simple suspension mixing and then natural deposition process. The films were characterized by various measurement techniques in detail. The results show that the composite films without any treatment almost still remain the original properties of the corresponding precursors, and exhibit loose structure, which can be easily broken in water; whereas after treated at 200 °C in air, the films become relatively more dense, and even if immersed into concentrated strong alkali or acid for five days, they still keep the film-morphologies, but regretfully, they show obvious brittleness and slight hydrophilicity. As soon as the treated films are performed in high concentrated strong alkali for about one day, their brittleness and wettability can be improved and became good flexibility and complete hydrophilicity.

  18. Study of cerium diffusion in undoped lithium-6 enriched glass with Rutherford backscattering spectrometry

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaodong; Moore, Michael E.; Lee, Kyung-Min; Lukosi, Eric D.; Hayward, Jason P.

    2016-07-01

    Undoped lithium-6 enriched glasses coated with pure cerium (99.9%) with a gold protection layer on top were heated at three different temperatures (500, 550, and 600 °C) for varied durations (1, 2, and 4 h). Diffusion profiles of cerium in such glasses were obtained with the conventional Rutherford backscattering technique. Through fitting the diffusion profiles with the thin-film solution of Fick's second law, diffusion coefficients of cerium with different annealing temperatures and durations were solved. Then, the activation energy of cerium for the diffusion process in the studied glasses was found to be 114 kJ/mol with the Arrhenius equation.

  19. 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

    2016-05-01

    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.

  20. Influence of film thickness on laser ablation threshold of transparent conducting oxide thin-films

    NASA Astrophysics Data System (ADS)

    Rung, S.; Christiansen, A.; Hellmann, R.

    2014-06-01

    We report on a comprehensive study of the laser ablation threshold of transparent conductive oxide thin films. The ablation threshold is determined for both indium tin oxide and gallium zinc oxide as a function of film thickness and for different laser wavelengths. By using a pulsed diode pumped solid state laser at 1064 nm, 532 nm, 355 nm and 266 nm, respectively, the relationship between optical absorption length and film thickness is studied. We find that the ablation threshold decreases with increasing film thickness in a regime where the absorption length is larger than the film thickness. In turn, the ablation threshold increases in case the absorption length is smaller than the film thickness. In particular, we observe a minimum of the ablation threshold in a region where the film thickness is comparable to the absorption length. To the best of our knowledge, this behaviour previously predicted for thin metal films, has been unreported for all three regimes in case of transparent conductive oxides, yet. For industrial laser scribing processes, these results imply that the efficiency can be optimized by using a laser where the optical absorption length is close to the film thickness.

  1. 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.

  2. 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. PMID:26566067

  3. Study of indium tin oxide films exposed to atomic axygen

    NASA Technical Reports Server (NTRS)

    Snyder, Paul G.; De, Bhola N.; Woollam, John A.; Coutts, T. J.; Li, X.

    1989-01-01

    A qualitative simulation of the effects of atomic oxygen has been conducted on indium tin oxide (ITO) films prepared by dc sputtering onto room-temperature substrates, by exposing them to an RF-excited oxygen plasma and characterizing the resulting changes in optical, electrical, and structural properties as functions of exposure time with ellipsometry, spectrophotometry, resistivity, and X-ray measurements. While the films thus exposed exhibit reduced resistivity and optical transmission; both of these effects, as well as partial crystallization of the films, may be due to sample heating by the plasma. Film resistivity is found to stabilize after a period of exposure.

  4. Structural characterization of impurified zinc oxide thin films

    SciTech Connect

    Trinca, L. M.; Galca, A. C. Stancu, V. Chirila, C. Pintilie, L.

    2014-11-05

    Europium doped zinc oxide (Eu:ZnO) thin films have been obtained by pulsed laser deposition (PLD). 002 textured thin films were achieved on glass and silicon substrates, while hetero-epilayers and homo-epilayers have been attained on single crystal SrTiO{sub 3} and ZnO, respectively. X-ray Diffraction (XRD) was employed to characterize the Eu:ZnO thin films. Extended XRD studies confirmed the different thin film structural properties as function of chosen substrates.

  5. A novel Graphene Oxide film: Synthesis and Dielectric properties

    NASA Astrophysics Data System (ADS)

    Canimkurbey, Betul; San, Sait Eren; Yasin, Muhammad; Köse, Muhammet Erkan

    In this work, we used Hummers method to synthesize Graphene Oxide (GO) and its parallel plate impedance spectroscopic technique to investigate dielectric properties. Graphene Oxide films were coated using drop casting method on ITO substrate. To analyze film morphology, atomic force microscopy was used. Dielectrics measurements of the samples were performed using impedance analyzer (HP-4194) in frequency range (100 Hz to 10MHz) at different temperatures. It was observed that the films' AC conductivity σac varied with angular frequency, ω as ωS, with S<1. The electrical properties of GO showed changes depending on both frequency and temperature. We observed GO film contains direct current (DC) and Correlated Barrier Hopping (CBH) conductivity mechanisms at low and high frequency ranges, respectively. Using solution processed Graphene Oxide will provide potential for organic electronic applications through its photon absorption and transmittance capability in the visible range and excellent electrical parameters.

  6. Ordered fragmentation of oxide thin films at submicron scale

    PubMed Central

    Guo, L.; Ren, Y.; Kong, L. Y.; Chim, W. K.; Chiam, S. Y.

    2016-01-01

    Crack formation is typically undesirable as it represents mechanical failure that compromises strength and integrity. Recently, there have also been numerous attempts to control crack formation in materials with the aim to prevent or isolate crack propagation. In this work, we utilize fragmentation, at submicron and nanometre scales, to create ordered metal oxide film coatings. We introduce a simple method to create modified films using electroplating on a prepatterned substrate. The modified films undergo preferential fragmentation at locations defined by the initial structures on the substrate, yielding ordered structures. In thicker films, some randomness in the characteristic sizes of the fragments is introduced due to competition between crack propagation and crack creation. The method presented allows patterning of metal oxide films over relatively large areas by controlling the fragmentation process. We demonstrate use of the method to fabricate high-performance electrochromic structures, yielding good coloration contrast and high coloration efficiency. PMID:27748456

  7. Ordered fragmentation of oxide thin films at submicron scale

    NASA Astrophysics Data System (ADS)

    Guo, L.; Ren, Y.; Kong, L. Y.; Chim, W. K.; Chiam, S. Y.

    2016-10-01

    Crack formation is typically undesirable as it represents mechanical failure that compromises strength and integrity. Recently, there have also been numerous attempts to control crack formation in materials with the aim to prevent or isolate crack propagation. In this work, we utilize fragmentation, at submicron and nanometre scales, to create ordered metal oxide film coatings. We introduce a simple method to create modified films using electroplating on a prepatterned substrate. The modified films undergo preferential fragmentation at locations defined by the initial structures on the substrate, yielding ordered structures. In thicker films, some randomness in the characteristic sizes of the fragments is introduced due to competition between crack propagation and crack creation. The method presented allows patterning of metal oxide films over relatively large areas by controlling the fragmentation process. We demonstrate use of the method to fabricate high-performance electrochromic structures, yielding good coloration contrast and high coloration efficiency.

  8. 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.

  9. Electrochromic lithium nickel oxide thin film by pulsed laser deposition

    SciTech Connect

    Wen, S.J.; Rottkay, K. von; Rubin, M.

    1996-10-01

    * Thin films of lithium nickel oxide were deposited by pulsed laser deposition (PLD) from targets of pressed LiNiO{sub 2} powder with layered structure. The composition, structure and surface air sensitivity of these films were analyzed using a variety of techniques, such as nuclear reaction analysis, Rutherford backscattering spectrometry (RBS), x-ray diffraction, infrared spectroscopy, and atomic force microscopy. Optical properties were measured using a combination of variable angle spectroscopic ellipsometry and IP spectroradiometry. Crystalline structure, surface morphology and chemical composition of Li{sub x}Ni{sub 1-x}O thin films depend strongly on deposition oxygen pressure, temperature as well as substrate target distance. The films produced at temperatures lower than 600 degrees C spontaneously absorb CO{sub 2} and H{sub 2}O at their surface once they are exposed to the air. The films deposited at 600 degrees C proved to be stable in air over a long period. Even when deposited at room temperature the PLD films are denser and more stable than sputtered films. RBS determined that the best electrochromic films had the stoichiometric composition L{sub 0.5}Ni{sub 0.5}O when deposited at 60 mTorr O{sub 2} pressure. Electrochemical tests show that the films exhibit excellent reversibility in the range 1.0 V to 3.4 V versus lithium and long cyclic life stability in a liquid electrolyte half cell. Electrochemical formatting which is used to develop electrochromism in other films and nickel oxide films is not needed for these stoichiometric films. The optical transmission range is almost 70% at 550 nm for 120 nm thick films.

  10. Determination of oxygen diffusion kinetics during thin film ruthenium oxidation

    SciTech Connect

    Coloma Ribera, R. Kruijs, R. W. E. van de; Yakshin, A. E.; Bijkerk, F.

    2015-08-07

    In situ X-ray reflectivity was used to reveal oxygen diffusion kinetics for thermal oxidation of polycrystalline ruthenium thin films and accurate determination of activation energies for this process. Diffusion rates in nanometer thin RuO{sub 2} films were found to show Arrhenius behaviour. However, a gradual decrease in diffusion rates was observed with oxide growth, with the activation energy increasing from about 2.1 to 2.4 eV. Further exploration of the Arrhenius pre-exponential factor for diffusion process revealed that oxidation of polycrystalline ruthenium joins the class of materials that obey the Meyer-Neldel rule.

  11. Determination of oxygen diffusion kinetics during thin film ruthenium oxidation

    NASA Astrophysics Data System (ADS)

    Coloma Ribera, R.; van de Kruijs, R. W. E.; Yakshin, A. E.; Bijkerk, F.

    2015-08-01

    In situ X-ray reflectivity was used to reveal oxygen diffusion kinetics for thermal oxidation of polycrystalline ruthenium thin films and accurate determination of activation energies for this process. Diffusion rates in nanometer thin RuO2 films were found to show Arrhenius behaviour. However, a gradual decrease in diffusion rates was observed with oxide growth, with the activation energy increasing from about 2.1 to 2.4 eV. Further exploration of the Arrhenius pre-exponential factor for diffusion process revealed that oxidation of polycrystalline ruthenium joins the class of materials that obey the Meyer-Neldel rule.

  12. Photo-oxidation Behaviour of EVA Antimicrobial Films

    NASA Astrophysics Data System (ADS)

    Botta, L.; Scaffaro, R.; La Mantia, F. P.

    2010-06-01

    In this work the photo-oxidation of neat EVA and antimicrobial EVA/Nisin films was studied. Two EVA samples—containing two different vinyl acetate levels—were added with different amounts of nisin. The influence of the matrix type and of the nisin content on the photo-oxidation behaviour was evaluated. The photo-oxidation has been followed by monitoring the change of the mechanical and spectroscopic properties upon artificial exposure to UV-B light. The results revealed that the films incorporating nisin show a better photo resistance with respect to the neat polymer. This improvement becomes weaker with decreasing the amount of nisin incorporated. Moreover the EVA 28 based films showed a much slower photo-oxidation rate in comparison with the EVA 14 based ones.

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

    DOE PAGESBeta

    Lipp, M. J.; Jeffries, J. R.; Cynn, H.; Park Klepeis, J. -H.; Evans, W. J.; Mortensen, D. R.; Seidler, G. T.; Xiao, Y.; Chow, P.

    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

  14. High stability mechanisms of quinary indium gallium zinc aluminum oxide multicomponent oxide films and thin film transistors

    SciTech Connect

    Lee, Ching-Ting Lin, Yung-Hao; Lin, Jhong-Ham

    2015-01-28

    Quinary indium gallium zinc aluminum oxide (IGZAO) multicomponent oxide films were deposited using indium gallium zinc oxide (IGZO) target and Al target by radio frequency magnetron cosputtering system. An extra carrier transport pathway could be provided by the 3 s orbitals of Al cations to improve the electrical properties of the IGZO films, and the oxygen instability could be stabilized by the strong Al-O bonds in the IGZAO films. The electron concentration change and the electron mobility change of the IGZAO films for aging time of 10 days under an air environment at 40 °C and 75% humidity were 20.1% and 2.4%, respectively. The experimental results verified the performance stability of the IGZAO films. Compared with the thin film transistors (TFTs) using conventional IGZO channel layer, in conducting the stability of TFTs with IGZAO channel layer, the transconductance g{sub m} change, threshold voltage V{sub T} change, and the subthreshold swing S value change under the same aging condition were improved to 7.9%, 10.5%, and 14.8%, respectively. Furthermore, the stable performances of the IGZAO TFTs were also verified by the positive gate bias stress. In this research, the quinary IGZAO multicomponent oxide films and that applied in TFTs were the first studied in the literature.

  15. High stability mechanisms of quinary indium gallium zinc aluminum oxide multicomponent oxide films and thin film transistors

    NASA Astrophysics Data System (ADS)

    Lee, Ching-Ting; Lin, Yung-Hao; Lin, Jhong-Ham

    2015-01-01

    Quinary indium gallium zinc aluminum oxide (IGZAO) multicomponent oxide films were deposited using indium gallium zinc oxide (IGZO) target and Al target by radio frequency magnetron cosputtering system. An extra carrier transport pathway could be provided by the 3 s orbitals of Al cations to improve the electrical properties of the IGZO films, and the oxygen instability could be stabilized by the strong Al-O bonds in the IGZAO films. The electron concentration change and the electron mobility change of the IGZAO films for aging time of 10 days under an air environment at 40 °C and 75% humidity were 20.1% and 2.4%, respectively. The experimental results verified the performance stability of the IGZAO films. Compared with the thin film transistors (TFTs) using conventional IGZO channel layer, in conducting the stability of TFTs with IGZAO channel layer, the transconductance gm change, threshold voltage VT change, and the subthreshold swing S value change under the same aging condition were improved to 7.9%, 10.5%, and 14.8%, respectively. Furthermore, the stable performances of the IGZAO TFTs were also verified by the positive gate bias stress. In this research, the quinary IGZAO multicomponent oxide films and that applied in TFTs were the first studied in the literature.

  16. Nitrogen doped zinc oxide thin film

    SciTech Connect

    Li, Sonny X.

    2003-12-15

    To summarize, polycrystalline ZnO thin films were grown by reactive sputtering. Nitrogen was introduced into the films by reactive sputtering in an NO{sub 2} plasma or by N{sup +} implantation. All ZnO films grown show n-type conductivity. In unintentionally doped ZnO films, the n-type conductivities are attributed to Zn{sub i}, a native shallow donor. In NO{sub 2}-grown ZnO films, the n-type conductivity is attributed to (N{sub 2}){sub O}, a shallow double donor. In NO{sub 2}-grown ZnO films, 0.3 atomic % nitrogen was found to exist in the form of N{sub 2}O and N{sub 2}. Upon annealing, N{sub 2}O decomposes into N{sub 2} and O{sub 2}. In furnace-annealed samples N{sub 2} redistributes diffusively and forms gaseous N{sub 2} bubbles in the films. Unintentionally doped ZnO films were grown at different oxygen partial pressures. Zni was found to form even at oxygen-rich condition and led to n-type conductivity. N{sup +} implantation into unintentionally doped ZnO film deteriorates the crystallinity and optical properties and leads to higher electron concentration. The free electrons in the implanted films are attributed to the defects introduced by implantation and formation of (N{sub 2}){sub O} and Zni. Although today there is still no reliable means to produce good quality, stable p-type ZnO material, ZnO remains an attractive material with potential for high performance short wavelength optoelectronic devices. One may argue that gallium nitride was in a similar situation a decade ago. Although we did not obtain any p-type conductivity, we hope our research will provide a valuable reference to the literature.

  17. Oxide film on metal substrate reduced to form metal-oxide-metal layer structure

    NASA Technical Reports Server (NTRS)

    Youngdahl, C. A.

    1967-01-01

    Electrically conductive layer of zirconium on a zirconium-oxide film residing on a zirconium substrate is formed by reducing the oxide in a sodium-calcium solution. The reduced metal remains on the oxide surface as an adherent layer and seems to form a barrier that inhibits further reaction.

  18. Growth of Epitaxial Oxide Thin Films on Graphene

    NASA Astrophysics Data System (ADS)

    Zou, Bin; Walker, Clementine; Wang, Kai; Tileli, Vasiliki; Shaforost, Olena; Harrison, Nicholas M.; Klein, Norbert; Alford, Neil M.; Petrov, Peter K.

    2016-08-01

    The transfer process of graphene onto the surface of oxide substrates is well known. However, for many devices, we require high quality oxide thin films on the surface of graphene. This step is not understood. It is not clear why the oxide should adopt the epitaxy of the underlying oxide layer when it is deposited on graphene where there is no lattice match. To date there has been no explanation or suggestion of mechanisms which clarify this step. Here we show a mechanism, supported by first principles simulation and structural characterisation results, for the growth of oxide thin films on graphene. We describe the growth of epitaxial SrTiO3 (STO) thin films on a graphene and show that local defects in the graphene layer (e.g. grain boundaries) act as bridge-pillar spots that enable the epitaxial growth of STO thin films on the surface of the graphene layer. This study, and in particular the suggestion of a mechanism for epitaxial growth of oxides on graphene, offers new directions to exploit the development of oxide/graphene multilayer structures and devices.

  19. Growth of Epitaxial Oxide Thin Films on Graphene

    PubMed Central

    Zou, Bin; Walker, Clementine; Wang, Kai; Tileli, Vasiliki; Shaforost, Olena; Harrison, Nicholas M.; Klein, Norbert; Alford, Neil M.; Petrov, Peter K.

    2016-01-01

    The transfer process of graphene onto the surface of oxide substrates is well known. However, for many devices, we require high quality oxide thin films on the surface of graphene. This step is not understood. It is not clear why the oxide should adopt the epitaxy of the underlying oxide layer when it is deposited on graphene where there is no lattice match. To date there has been no explanation or suggestion of mechanisms which clarify this step. Here we show a mechanism, supported by first principles simulation and structural characterisation results, for the growth of oxide thin films on graphene. We describe the growth of epitaxial SrTiO3 (STO) thin films on a graphene and show that local defects in the graphene layer (e.g. grain boundaries) act as bridge-pillar spots that enable the epitaxial growth of STO thin films on the surface of the graphene layer. This study, and in particular the suggestion of a mechanism for epitaxial growth of oxides on graphene, offers new directions to exploit the development of oxide/graphene multilayer structures and devices. PMID:27515496

  20. Growth of Epitaxial Oxide Thin Films on Graphene.

    PubMed

    Zou, Bin; Walker, Clementine; Wang, Kai; Tileli, Vasiliki; Shaforost, Olena; Harrison, Nicholas M; Klein, Norbert; Alford, Neil M; Petrov, Peter K

    2016-01-01

    The transfer process of graphene onto the surface of oxide substrates is well known. However, for many devices, we require high quality oxide thin films on the surface of graphene. This step is not understood. It is not clear why the oxide should adopt the epitaxy of the underlying oxide layer when it is deposited on graphene where there is no lattice match. To date there has been no explanation or suggestion of mechanisms which clarify this step. Here we show a mechanism, supported by first principles simulation and structural characterisation results, for the growth of oxide thin films on graphene. We describe the growth of epitaxial SrTiO3 (STO) thin films on a graphene and show that local defects in the graphene layer (e.g. grain boundaries) act as bridge-pillar spots that enable the epitaxial growth of STO thin films on the surface of the graphene layer. This study, and in particular the suggestion of a mechanism for epitaxial growth of oxides on graphene, offers new directions to exploit the development of oxide/graphene multilayer structures and devices. PMID:27515496

  1. Synthesis and Oxidation Resistance of h-BN Thin Films

    NASA Astrophysics Data System (ADS)

    Stewart, David; Meulenberg, Robert; Lad, Robert

    Hexagonal boron nitride (h-BN) is an exciting 2D material for use in sensors and other electronic devices that operate in harsh, high temperature environments. Not only is h-BN a wide band gap material with excellent wear resistance and high temperature stability, but recent reports indicate that h-BN can prevent metallic substrates from oxidizing above 600°C in low O2 pressures. However, the PVD of highly crystalline h-BN films required for this oxidation protection has proven challenging. In this work, we have explored the growth of h-BN thin films by reactive RF magnetron sputtering from an elemental B target in an Ar/N2 atmosphere. The film growth rate is extremely slow and the resulting films are atomically smooth and homogeneous. Using DC biasing during deposition and high temperature annealing treatments, the degree of film crystallinity can be controlled. The oxidation resistance of h-BN films deposited on inert sapphire and reactive metal substrates such as Zr and ZrB2 has been examined by techniques such as XPS, XRD, and SEM after oxidation between 600 and 1200°C under varying oxygen pressures. The success of h-BN as a passivation layer for metallic substrates in harsh environments is shown to depend greatly on its crystalline quality and defects. Supported by the NSF SusChEM program.

  2. 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.

  3. 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

  4. 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

  5. Assigning the Cerium Oxidation State for CH2CeF2 and OCeF2 Based on Multireference Wave Function Analysis.

    PubMed

    Mooßen, Oliver; Dolg, Michael

    2016-06-01

    The geometric and electronic structure of the recently experimentally studied molecules ZCeF2 (Z = CH2, O) was investigated by density functional theory (DFT) and wave function-based ab initio methods. Special attention was paid to the Ce-Z metal-ligand bonding, especially to the nature of the interaction between the Ce 4f and the Z 2p orbitals and the possible multiconfigurational character arising from it, as well as to the assignment of an oxidation state of Ce reflecting the electronic structure. Complete active space self-consistent field (CASSCF) calculations were performed, followed by orbital rotations in the active orbital space. The methylene compound CH2CeF2 has an open-shell singlet ground state, which is characterized by a two-configurational wave function in the basis of the strongly mixed natural CASSCF orbitals. The system can also be described in a very compact way by the dominant Ce 4f(1) C 2p(1) configuration, if nearly pure Ce 4f and C 2p orbitals are used. In the basis of these localized orbitals, the molecule is almost monoconfigurational and should be best described as a Ce(III) system. The singlet ground state of the oxygen OCeF2 complex is of closed-shell character when a monoconfigurational wave function with very strongly mixed Ce 4f and O 2p CASSCF natural orbitals is used for the description. The transformation to orbitals localized on the cerium and oxygen atoms leads to a multiconfigurational wave function and reveals characteristics of a mixed valent Ce(IV)/Ce(III) compound. Additionally, the interactions of the localized active orbitals were analyzed by evaluating the expectation values of the charge fluctuation operator and the local spin operator. The Ce 4f and C 2p orbital interaction of the CH2CeF2 compound is weakly covalent and resembles the interaction of the H 1s orbitals in a stretched hydrogen dimer. In contrast, the interaction of the localized active orbitals for OCeF2 shows ionic character. Calculated vibrational Ce

  6. Continuous-flow IRMS technique for determining the 17O excess of CO2 using complete oxygen isotope exchange with cerium oxide

    NASA Astrophysics Data System (ADS)

    Mrozek, D. J.; van der Veen, C.; Kliphuis, M.; Kaiser, J.; Wiegel, A. A.; Röckmann, T.

    2015-02-01

    This paper presents an analytical system for analysis of all single substituted isotopologues (12C16O17O, 12C16O18O, 13C16O16O) in nanomolar quantities of CO2 extracted from stratospheric air samples. CO2 is separated from bulk air by gas chromatography and CO2 isotope ratio measurements (ion masses 45 / 44 and 46 / 44) are performed using isotope ratio mass spectrometry (IRMS). The 17O excess (Δ17O) is derived from isotope measurements on two different CO2 aliquots: unmodified CO2 and CO2 after complete oxygen isotope exchange with cerium oxide (CeO2) at 700 °C. Thus, a single measurement of Δ17O requires two injections of 1 mL of air with a CO2 mole fraction of 390 μmol mol-1 at 293 K and 1 bar pressure (corresponding to 16 nmol CO2 each). The required sample size (including flushing) is 2.7 mL of air. A single analysis (one pair of injections) takes 15 minutes. The analytical system is fully automated for unattended measurements over several days. The standard deviation of the 17O excess analysis is 1.7‰. Multiple measurements on an air sample reduce the measurement uncertainty, as expected for the statistical standard error. Thus, the uncertainty for a group of 10 measurements is 0.58‰ for Δ 17O in 2.5 h of analysis. 100 repeat analyses of one air sample decrease the standard error to 0.20‰. The instrument performance was demonstrated by measuring CO2 on stratospheric air samples obtained during the EU project RECONCILE with the high-altitude aircraft Geophysica. The precision for RECONCILE data is 0.03‰ (1σ) for δ13C, 0.07‰ (1σ) for δ18O and 0.55‰ (1σ) for δ17O for a sample of 10 measurements. This is sufficient to examine stratospheric enrichments, which at altitude 33 km go up to 12‰ for δ17O and up to 8‰ for δ18O with respect to tropospheric CO2 : δ17O ~ 21‰ Vienna Standard Mean Ocean Water (VSMOW), δ18O ~ 41‰ VSMOW (Lämmerzahl et al., 2002). The samples measured with our analytical technique agree with available data for

  7. Oxidation and growth of Mg thin films on Ru(001)

    NASA Astrophysics Data System (ADS)

    Huang, H. H.; Jiang, X.; Siew, H. L.; Chin, W. S.; Sim, W. S.; Xu, G. Q.

    1999-08-01

    The oxidation and growth of ultra-thin Mg films on a Ru(001) substrate have been studied using X-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS) in the temperature range of 300-1500 K. Our results suggest that the growth of Mg thin films follows a layer-by-layer mode. Upon oxygen adsorption at 300 K, two O 1s peaks were detected on the Mg film. The peak at 532.2-532.6 eV could be attributed to either dioxygen or partially reduced species (O δ-, δ<2), whereas that at 530.1-530.6 eV is due to lattice oxygen in MgO. Annealing of the oxidized film to 800 K causes the conversion of the dioxygen or partially reduced species to the oxide state. Thermal desorption peaks of MgO were directly detected at 1000-1127 and 1350-1380 K, respectively. However, initial evaporation of Mg atoms onto an oxygen pre-adsorbed surface yields a fully oxidized MgO. Further Mg deposition results in the formation of a partially oxidized film with the observation of an O 1s peak at 532.2 eV.

  8. Stress and phase transformation phenomena in oxide films

    SciTech Connect

    Exarhos, G.J.; Hess, N.J.

    1992-04-01

    In situ optical methods are reviewed for characterization of phase transformation processes and evaluation of residual stress in solution- deposited metastable oxide films. Such low density films most often are deposited as disordered phases making them prone to crystallization and attendant densification when subjected to increased temperature and/or applied pressure. Inherent stress imparted during film deposition and its evolution during the transformation are evaluated from phonon frequency shifts seen in Raman spectra (TiO{sub 2}) or from changes in the laser-induced fluorescence emission spectra for films containing rare earth (Sm{sup +3}:Y{sub 3}Al{sub 5}O{sub 12}) or transition metal (Cr{sup +3}:Al{sub 2}O{sub 3}) dopants. The data in combination with measured increases in line intensities intrinsic to the evolving phase are used to follow crystallization processes in thin films. In general, film deposition parameters are found to influence the crystallite ingrowth kinetics and the magnitude of stress and stress relaxation in the film during the transformation. The utility of these methods to probe crystallization phenomena in oxide films will be addressed.

  9. Growth control of the oxidation state in vanadium oxide thin films

    SciTech Connect

    Lee, Shinbuhm; Meyer, Tricia L.; Park, Sungkyun; Lee, Ho Nyung

    2014-12-05

    Precise control of the chemical valence or oxidation state of vanadium in vanadium oxide thin films is highly desirable for not only fundamental research, but also technological applications that utilize the subtle change in the physical properties originating from the metalinsulator transition (MIT) near room temperature. However, due to the multivalent nature of vanadium and the lack of a good understanding on growth control of the oxidation state, stabilization of phase pure vanadium oxides with a single oxidation state is extremely challenging. Here, we systematically varied the growth conditions to clearly map out the growth window for preparing phase pure epitaxial vanadium oxides by pulsed laser deposition for providing a guideline to grow high quality thin films with well-defined oxidation states of V₂⁺²O₃, V⁺⁴O₂, and V₂⁺⁵O₅. A well pronounced MIT was only observed in VO₂ films grown in a very narrow range of oxygen partial pressure P(O₂). The films grown either in lower (< 10 mTorr) or higher P(O₂) (> 25 mTorr) result in V₂O₃ and V₂O₅ phases, respectively, thereby suppressing the MIT for both cases. We have also found that the resistivity ratio before and after the MIT of VO₂ thin films can be further enhanced by one order of magnitude when the films are further oxidized by post-annealing at a well-controlled oxidizing ambient. This result indicates that stabilizing vanadium into a single valence state has to compromise with insufficient oxidation of an as grown thin film and, thereby, a subsequent oxidation is required for an 3 improved MIT behavior.

  10. Growth control of the oxidation state in vanadium oxide thin films

    DOE PAGESBeta

    Lee, Shinbuhm; Meyer, Tricia L.; Park, Sungkyun; Lee, Ho Nyung

    2014-12-05

    Precise control of the chemical valence or oxidation state of vanadium in vanadium oxide thin films is highly desirable for not only fundamental research, but also technological applications that utilize the subtle change in the physical properties originating from the metalinsulator transition (MIT) near room temperature. However, due to the multivalent nature of vanadium and the lack of a good understanding on growth control of the oxidation state, stabilization of phase pure vanadium oxides with a single oxidation state is extremely challenging. Here, we systematically varied the growth conditions to clearly map out the growth window for preparing phase puremore » epitaxial vanadium oxides by pulsed laser deposition for providing a guideline to grow high quality thin films with well-defined oxidation states of V₂⁺²O₃, V⁺⁴O₂, and V₂⁺⁵O₅. A well pronounced MIT was only observed in VO₂ films grown in a very narrow range of oxygen partial pressure P(O₂). The films grown either in lower (< 10 mTorr) or higher P(O₂) (> 25 mTorr) result in V₂O₃ and V₂O₅ phases, respectively, thereby suppressing the MIT for both cases. We have also found that the resistivity ratio before and after the MIT of VO₂ thin films can be further enhanced by one order of magnitude when the films are further oxidized by post-annealing at a well-controlled oxidizing ambient. This result indicates that stabilizing vanadium into a single valence state has to compromise with insufficient oxidation of an as grown thin film and, thereby, a subsequent oxidation is required for an 3 improved MIT behavior.« less

  11. Growth control of the oxidation state in vanadium oxide thin films

    SciTech Connect

    Lee, Shinbuhm; Meyer, Tricia L.; Lee, Ho Nyung; Park, Sungkyun; Egami, Takeshi

    2014-12-01

    Precise control of the chemical valence or oxidation state of vanadium in vanadium oxide thin films is highly desirable for not only fundamental research but also technological applications that utilize the subtle change in the physical properties originating from the metal-insulator transition (MIT) near room temperature. However, due to the multivalent nature of vanadium and the lack of a good understanding on growth control of the oxidation state, stabilization of phase pure vanadium oxides with a single oxidation state is extremely challenging. Here, we systematically varied the growth conditions to clearly map out the growth window for preparing phase pure epitaxial vanadium oxides by pulsed laser deposition for providing a guideline to grow high quality thin films with well-defined oxidation states of V{sub 2}{sup +3}O{sub 3}, V{sup +4}O{sub 2}, and V{sub 2}{sup +5}O{sub 5}. A well pronounced MIT was only observed in VO{sub 2} films grown in a very narrow range of oxygen partial pressure P(O{sub 2}). The films grown either in lower (<10 mTorr) or higher P(O{sub 2}) (>25 mTorr) result in V{sub 2}O{sub 3} and V{sub 2}O{sub 5} phases, respectively, thereby suppressing the MIT for both cases. We have also found that the resistivity ratio before and after the MIT of VO{sub 2} thin films can be further enhanced by one order of magnitude when the films are further oxidized by post-annealing at a well-controlled oxidizing ambient. This result indicates that stabilizing vanadium into a single valence state has to compromise with insufficient oxidation of an as grown thin film and, thereby, a subsequent oxidation is required for an improved MIT behavior.

  12. Multifunctional oxide thin films for magnetoelectric and electromechanical applications

    NASA Astrophysics Data System (ADS)

    Baek, Seung Hyub

    Epitaxial multifunctional oxide thin films have been extensively researched to understand and exploit a variety of their physical properties. In order to integrate such versatile properties into real devices, there are several critical issues: (1) high-quality thin film growth, (2) fundamental understanding on reliable performance, and (3) device fabrication process preserving functionality of oxides. We have investigated all these issues, employing two different materials: multiferroic BiFeO3 and piezoelectric Pb(Mg1/3 Nb2/3)O3-PbTiO3 (PMN-PT) epitaxial thin films. For the high-quality thin film growth, we have chosen both BiFeO 3 and PMN-PT thin films as a model system. Bi2O3and PbO are the volatile species in these oxides, which makes it hard to grow phase-pure stoichiometric thin films. Because the properties of oxides are sensitive to stoichiometry and defects, it is highly required to fix such volatile elements during thin film growth. We have grown high-quality epitaxial thin films using a fast-rate off-axis sputtering method and vicinal substrates. In addition, we were able to control domain structures of BiFeO3 thin films using vicinal substrates. For the study on the reliability issues in oxides, we have used BiFeO 3 thin films within the framework of magnetoelectric device applications. For reliable magnetoelectric performance of BiFeO3, polarization switching path has to be (1) deterministic, and to be retained along with (2) time---retention, and (3) cycles--- fatigue. We have used monodomain BiFeO3 thin films as a model system. Based on theoretical predictions, we have studied polarization switching paths, and achieved both selective polarization switching and retention problems using island BiFeO3 structure. We have also investigated polarization fatigue, dependent on switching path. For the demonstration of working devices preserving the original functionality of oxides, we have fabricated micro-cantilevers using PMN-PT heterostructure on Si. The

  13. SPH based modelling of oxide and oxide film formation in gravity die castings

    NASA Astrophysics Data System (ADS)

    Ellingsen, K.; Coudert, T.; M'Hamdi, M.

    2015-06-01

    Gravity die casting is an important casting process which has the capability of making complicated, high-integrity components for e.g. the automotive industry. Oxides and oxide films formed during filling affect the cast product quality. The Smoothed particle hydrodynamics (SPH) method is particularly suited to follow complex flows. The SPH method has been used to study filling of a gravity die including the formation and transport of oxides and oxide films for two different filling velocities. A low inlet velocity leads to a higher amount of oxides and oxide films in the casting. The study demonstrates the usefulness of the SPH method for an increased understanding of the effect of different filling procedures on the cast quality.

  14. Aerosol chemical vapor deposition of metal oxide films

    DOEpatents

    Ott, K.C.; Kodas, T.T.

    1994-01-11

    A process of preparing a film of a multicomponent metal oxide including: forming an aerosol from a solution comprised of a suitable solvent and at least two precursor compounds capable of volatilizing at temperatures lower than the decomposition temperature of said precursor compounds; passing said aerosol in combination with a suitable oxygen-containing carrier gas into a heated zone, said heated zone having a temperature sufficient to evaporate the solvent and volatilize said precursor compounds; and passing said volatilized precursor compounds against the surface of a substrate, said substrate having a sufficient temperature to decompose said volatilized precursor compounds whereby metal atoms contained within said volatilized precursor compounds are deposited as a metal oxide film upon the substrate is disclosed. In addition, a coated article comprising a multicomponent metal oxide film conforming to the surface of a substrate selected from the group consisting of silicon, magnesium oxide, yttrium-stabilized zirconium oxide, sapphire, or lanthanum gallate, said multicomponent metal oxide film characterized as having a substantially uniform thickness upon said substrate.

  15. Electrochemical formation of a composite polymer-aluminum oxide film

    NASA Astrophysics Data System (ADS)

    Runge-Marchese, Jude Mary

    1997-10-01

    The formation of polymer films through electrochemical techniques utilizing electrolytes which include conductive polymer is of great interest to the coatings and electronics industries as a means for creating electrically conductive and corrosion resistant finishes. One of these polymers, polyamino-benzene (polyaniline), has been studied for this purpose for over ten years. This material undergoes an insulator-to-metal transition upon doping with protonic acids in an acid/base type reaction. Review of prior studies dealing with polyaniline and working knowledge of aluminum anodization has led to the development of a unique process whereby composite polymer-aluminum oxide films are formed. The basis for the process is a modification of the anodizing electrolyte which results in the codeposition of polyaniline during aluminum anodization. A second process, which incorporates electrochemical sealing of the anodic layer with polyaniline was also developed. The formation of these composite films is documented through experimental processing, and characterized by way of scientific analysis and engineering tests. Analysis results revealed the formation of unique dual phase anodic films with fine microstructures which exhibited full intrusion of the columnar aluminum oxide structure with polyaniline, indicating the polymer was deposited as the metal oxidation proceeded. An aromatic amine derivative of polyaniline with aluminum sulfate was determined to be the reaction product within the aluminum oxide phase of the codeposited films. Scientific characterization determined the codeposition process yields completely chemically and metallurgically bound composite films. Engineering studies determined the films, obtained through a single step, exhibited superior wear and corrosion resistance to conventionally anodized and sealed films processed through two steps, demonstrating the increased manufacturing process efficiency that can be realized with the modification of the

  16. Graphene Oxide Transparent Hybrid Film and Its Ultraviolet Shielding Property.

    PubMed

    Xie, Siyuan; Zhao, Jianfeng; Zhang, Bowu; Wang, Ziqiang; Ma, Hongjuan; Yu, Chuhong; Yu, Ming; Li, Linfan; Li, Jingye

    2015-08-19

    Herein, we first reported a facile strategy to prepare functional Poly(vinyl alcohol) (PVA) hybrid film with well ultraviolet (UV) shielding property and visible light transmittance using graphene oxide nanosheets as UV-absorber. The absorbance of ultraviolet light at 300 nm can be up to 97.5%, while the transmittance of visible light at 500 nm keeps 40% plus. This hybrid film can protect protein from UVA light induced photosensitive damage, remarkably. PMID:26226281

  17. In situ Oxidation of Ultrathin Silver Films on Ni(111)

    SciTech Connect

    A Meyer; I Flege; S Senanayake; B Kaemena; R Rettew; F Alamgir; J Falta

    2011-12-31

    Oxidation of silver films of one- and two-monolayer thicknesses on the Ni(111) surface was investigated by low-energy electron microscopy at temperatures of 500 and 600 K. Additionally, intensity-voltage curves were measured in situ during oxidation to reveal the local film structure on a nanometer scale. At both temperatures, we find that exposure to molecular oxygen leads to the destabilization of the Ag film with subsequent relocation of the silver atoms to small few-layer-thick silver patches and concurrent evolution of NiO(111) regions. Subsequent exposure of the oxidized surface to ethylene initiates the transformation of bilayer islands back into monolayer islands, demonstrating at least partial reversibility of the silver relocation process at 600 K.

  18. The physical and chemical properties of ultrathin oxide films.

    PubMed

    Street, S C; Xu, C; Goodman, D W

    1997-01-01

    Thin oxide films (from one to tens of monolayers) of SiO2, MgO, NiO, Al2O3, FexOy, and TiO2 supported on refractory metal substrates have been prepared by depositing the oxide metal precursor in a background of oxygen (ca 1 x 10(-5) Torr). The thinness of these oxide samples facilitates investigation by an array of surface techniques, many of which are precluded when applied to the corresponding bulk oxide. Layered and mixed binary oxides have been prepared by sequential synthesis of dissimilar oxide layers or co-deposition of two different oxides. Recent work has shown that the underlying oxide substrate can markedly influence the electronic and chemical properties of the overlayer oxide. The structural, electronic, and chemical properties of these ultrathin oxide films have been probed using Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), electron energy loss spectroscopy (ELS), ion-scattering spectroscopy (ISS), high-resolution electron energy loss spectroscopy (HREELS), infrared reflectance absorption spectroscopy (IRAS), temperature-programmed desorption (TPD), scanning tunneling microscopy (STM), and scanning tunneling spectroscopy (STS).

  19. Investigation of solution-processed bismuth-niobium-oxide films

    SciTech Connect

    Inoue, Satoshi; Ariga, Tomoki; Matsumoto, Shin; Onoue, Masatoshi; Miyasako, Takaaki; Tokumitsu, Eisuke; Shimoda, Tatsuya; Chinone, Norimichi; Cho, Yasuo

    2014-10-21

    The characteristics of bismuth-niobium-oxide (BNO) films prepared using a solution process were investigated. The BNO film annealed at 550°C involving three phases: an amorphous phase, Bi₃NbO₇ fluorite microcrystals, and Nb-rich cubic pyrochlore microcrystals. The cubic pyrochlore structure, which was the main phase in this film, has not previously been reported in BNO films. The relative dielectric constant of the BNO film was approximately 140, which is much higher than that of a corresponding film prepared using a conventional vacuum sputtering process. Notably, the cubic pyrochlore microcrystals disappeared with increasing annealing temperature and were replaced with triclinic β-BiNbO₄ crystals at 590°C. The relative dielectric constant also decreased with increasing annealing temperature. Therefore, the high relative dielectric constant of the BNO film annealed at 550°C is thought to result from the BNO cubic pyrochlore structure. In addition, the BNO films annealed at 500°C contained approximately 6.5 atm.% carbon, which was lost at approximately 550°C. This result suggests that the carbon in the BNO film played an important role in the formation of the cubic pyrochlore structure.

  20. Chemical fabrication of superconducting Y-Ba-Cu oxide films

    NASA Astrophysics Data System (ADS)

    Hussain, A. A.; Sayer, M.

    1992-02-01

    High-Tc superconducting films of Y-Ba-Cu oxide were prepared on 100-plane MgO substrates by a sol-gel method. A procedure is described for preparing a superconducting film using acetate compounds dissolved in salicylic or lactic acids in the presence of ethylene glycol. This solution has superior qualities in terms of homogeneity, viscosity, and stability against atmospheric hydration. The results indicate that the nature of the solvent influences the microstructure and superconducting properties of Y-Ba-Cu-O films. X-ray diffraction analysis reveals that the annealed films are textured and had orthorhombic orientation. A correlation between the crystal structure and the superconducting properties of the Y-Ba-Cu-O films is presented.

  1. Large and pristine films of reduced graphene oxide

    PubMed Central

    Ahn, Sung Il; Kim, Kukjoo; Jung, Jura; Choi, Kyung Cheol

    2015-01-01

    A new self-assembly concept is introduced to form large and pristine films (15 cm in diameter) of reduced graphene oxide (RGO). The resulting film has different degrees of polarity on its two different sides due to the characteristic nature of the self-assembly process. The RGO film can be easily transferred from a glass substrate onto water and a polymer substrate after injection of water molecules between the RGO film and glass substrate using an electric steamer. The RGO film can also be easily patterned into various shapes with a resolution of around ±10 μm by a simple taping method, which is suitable for mass production of printed electronics at low cost. PMID:26689267

  2. 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.

  3. Mechanisms of polarization switching in graphene oxides and poly(vinylidene fluoride)-graphene oxide films

    NASA Astrophysics Data System (ADS)

    Jiang, Zhiyuan; Zheng, Guangping; Zhan, Ke; Han, Zhuo; Wang, Hao

    2016-04-01

    Polarization switching in graphene oxides (GOs) and poly(vinylidene fluoride) (PVDF)-GO nanocomposite is investigated by piezoelectric force microscopy (PFM). The dynamical switching results reveal that GO films exhibit ferroelectric and piezoelectric properties with two-dimensional characteristics. Abnormal polarization switching is observed in PVDF-GO films, which is promising for electronic applications.

  4. Comparison of topotactic fluorination methods for complex oxide films

    SciTech Connect

    Moon, E. J. Choquette, A. K.; Huon, A.; Kulesa, S. Z.; May, S. J.; Barbash, D.

    2015-06-01

    We have investigated the synthesis of SrFeO{sub 3−α}F{sub γ} (α and γ ≤ 1) perovskite films using topotactic fluorination reactions utilizing poly(vinylidene fluoride) as a fluorine source. Two different fluorination methods, a spin-coating and a vapor transport approach, were performed on as-grown SrFeO{sub 2.5} films. We highlight differences in the structural, compositional, and optical properties of the oxyfluoride films obtained via the two methods, providing insight into how fluorination reactions can be used to modify electronic and optical behavior in complex oxide heterostructures.

  5. Peculiarities of jumping electroconductivity in bismuth oxide films

    NASA Astrophysics Data System (ADS)

    Vidadi, Yu. A.; Guseinov, Ya. Yu.; Bagiev, V. E.; Rafiev, T. Yu.

    1991-11-01

    The electrical properties of bismuth oxide films with direct and alternating current have been studied. A charge carrier transfer is shown to be dominant in these films both at low temperatures and at high frequencies due to the carrier jumps between the localized states with the energy near the Fermi level N( EF). The value of N( EF) at the localization radius α -1 = 8Å, the angular coefficient in Mott's law for jumping conductivity B = 93 K {1}/{4} and the average length of jumping at 230 K, R = 70 Å, have been calculated by two independent methods for τ-Bi 2O 3 films.

  6. Surface and sub-surface thermal oxidation of thin ruthenium films

    SciTech Connect

    Coloma Ribera, R.; Kruijs, R. W. E. van de; Yakshin, A. E.; Bijkerk, F.; Kokke, S.; Zoethout, E.

    2014-09-29

    A mixed 2D (film) and 3D (nano-column) growth of ruthenium oxide has been experimentally observed for thermally oxidized polycrystalline ruthenium thin films. Furthermore, in situ x-ray reflectivity upon annealing allowed the detection of 2D film growth as two separate layers consisting of low density and high density oxides. Nano-columns grow at the surface of the low density oxide layer, with the growth rate being limited by diffusion of ruthenium through the formed oxide film. Simultaneously, with the growth of the columns, sub-surface high density oxide continues to grow limited by diffusion of oxygen or ruthenium through the oxide film.

  7. Passivation of thin film oxide superconductors

    SciTech Connect

    Josefowicz, J.Y.; Rensch, D.B.; Nieh, K.W.

    1992-05-19

    This patent describes a passivation coating for oxide superconductors. It comprises a first layer of a Group II oxide encapsulating the oxide superconductor, the Group II having a substantially amorphous structure and having a thickness ranging from about 500 {Angstrom} to 2 {mu}m; and a second layer of a polymer covering the Group II oxide, the polymer comprising a composition selected from the group consisting of polyimide, polybenzyl methacrylate, polybutyl methacrylate, polybutyl styrene, polybutadiene, styrenes, polyamide resins, polyacrylics, polyacrylamides, polystyrenes, polyethylene, polyisoprene, polymethyl pentenes, polymethyl methacrylates, and polyvinyls.

  8. Combinatorial measurements of Hall effect and resistivity in oxide films.

    PubMed

    Clayhold, J A; Kerns, B M; Schroer, M D; Rench, D W; Logvenov, G; Bollinger, A T; Bozovic, I

    2008-03-01

    A system for the simultaneous measurement of the Hall effect in 31 different locations as well as the measurement of the resistivity in 30 different locations on a single oxide thin film grown with a composition gradient is described. Considerations for designing and operating a high-throughput system for characterizing highly conductive oxides with Hall coefficients as small as 10(-10) m3/C are discussed. Results from measurements on films grown using combinatorial molecular beam epitaxy show the usefulness of characterizing combinatorial libraries via both the resistivity and the Hall effect. PMID:18377026

  9. Plasmon polaritons in conducting-metal-oxide films

    NASA Astrophysics Data System (ADS)

    Efremenko, A.; Rhodes, C.; Cerutti, M.; Losego, M.; Aspnes, D. E.; Maria, J.-P.; Franzen, S.

    2008-10-01

    We report the evolution with thickness of p-polarized reflectance spectra of indium tin oxide (ITO) films deposited on BK-7 glass. ITO is one of the most common examples of the class of conducting metal oxides. Due to the low charge carrier density, ˜10-21/cm^3, the spectral features of the plasmon are observed in the near infrared. The spectra are dominated by two plasmon polariton structures, which we show are associated with the screened bulk plasmon (SBP) for very thin films and the surface plasmon for thick films. The conductor skin depth is the cut-off between the thin and thick film behavior. Remarkably, all features of these complex spectra are accurately described using only the three-phase model and the Drude free-electron representation of the dielectric function of the films. This first observation of the SBP is made possible by the unique features of these films, which include continuity for even the thinnest films and an absence of complications from bulk absorption in the spectral region of interest. The observation of the SBP is possible due to the fact that ITO behaves as a free electron conductor. Specifically, ITO has no band-to-band transitions that would obscure the intrinsic screed bulk plasmons.

  10. Characterization of reliability of printed indium tin oxide thin films.

    PubMed

    Hong, Sung-Jei; Kim, Jong-Woong; Jung, Seung-Boo

    2013-11-01

    Recently, decreasing the amount of indium (In) element in the indium tin oxide (ITO) used for transparent conductive oxide (TCO) thin film has become necessary for cost reduction. One possible approach to this problem is using printed ITO thin film instead of sputtered. Previous studies showed potential for printed ITO thin films as the TCO layer. However, nothing has been reported on the reliability of printed ITO thin films. Therefore, in this study, the reliability of printed ITO thin films was characterized. ITO nanoparticle ink was fabricated and printed onto a glass substrate followed by heating at 400 degrees C. After measurement of the initial values of sheet resistance and optical transmittance of the printed ITO thin films, their reliabilities were characterized with an isothermal-isohumidity test for 500 hours at 85 degrees C and 85% RH, a thermal shock test for 1,000 cycles between 125 degrees C and -40 degrees C, and a high temperature storage test for 500 hours at 125 degrees C. The same properties were investigated after the tests. Printed ITO thin films showed stable properties despite extremely thermal and humid conditions. Sheet resistances of the printed ITO thin films changed slightly from 435 omega/square to 735 omega/square 507 omega/square and 442 omega/square after the tests, respectively. Optical transmittances of the printed ITO thin films were slightly changed from 84.74% to 81.86%, 88.03% and 88.26% after the tests, respectively. These test results suggest the stability of printed ITO thin film despite extreme environments. PMID:24245331

  11. Tungsten oxide proton conducting films for low-voltage transparent oxide-based thin-film transistors

    SciTech Connect

    Zhang, Hongliang; Wan, Qing; Wan, Changjin; Wu, Guodong; Zhu, Liqiang

    2013-02-04

    Tungsten oxide (WO{sub x}) electrolyte films deposited by reactive magnetron sputtering showed a high room temperature proton conductivity of 1.38 Multiplication-Sign 10{sup -4} S/cm with a relative humidity of 60%. Low-voltage transparent W-doped indium-zinc-oxide thin-film transistors gated by WO{sub x}-based electrolytes were self-assembled on glass substrates by one mask diffraction method. Enhancement mode operation with a large current on/off ratio of 4.7 Multiplication-Sign 10{sup 6}, a low subthreshold swing of 108 mV/decade, and a high field-effect mobility 42.6 cm{sup 2}/V s was realized. Our results demonstrated that WO{sub x}-based proton conducting films were promising gate dielectric candidates for portable low-voltage oxide-based devices.

  12. Tungsten oxide proton conducting films for low-voltage transparent oxide-based thin-film transistors

    NASA Astrophysics Data System (ADS)

    Zhang, Hongliang; Wan, Qing; Wan, Changjin; Wu, Guodong; Zhu, Liqiang

    2013-02-01

    Tungsten oxide (WOx) electrolyte films deposited by reactive magnetron sputtering showed a high room temperature proton conductivity of 1.38 × 10-4 S/cm with a relative humidity of 60%. Low-voltage transparent W-doped indium-zinc-oxide thin-film transistors gated by WOx-based electrolytes were self-assembled on glass substrates by one mask diffraction method. Enhancement mode operation with a large current on/off ratio of 4.7 × 106, a low subthreshold swing of 108 mV/decade, and a high field-effect mobility 42.6 cm2/V s was realized. Our results demonstrated that WOx-based proton conducting films were promising gate dielectric candidates for portable low-voltage oxide-based devices.

  13. Plasma enhanced chemical vapor deposition (PECVD) method of forming vanadium oxide films and vanadium oxide thin-films prepared thereby

    DOEpatents

    Zhang, Ji-Guang; Tracy, C. Edwin; Benson, David K.; Turner, John A.; Liu, Ping

    2000-01-01

    A method is disclosed of forming a vanadium oxide film on a substrate utilizing plasma enhanced chemical vapor deposition. The method includes positioning a substrate within a plasma reaction chamber and then forming a precursor gas comprised of a vanadium-containing chloride gas in an inert carrier gas. This precursor gas is then mixed with selected amounts of hydrogen and oxygen and directed into the reaction chamber. The amounts of precursor gas, oxygen and hydrogen are selected to optimize the final properties of the vanadium oxide film An rf plasma is generated within the reaction chamber to chemically react the precursor gas with the hydrogen and the oxygen to cause deposition of a vanadium oxide film on the substrate while the chamber deposition pressure is maintained at about one torr or less. Finally, the byproduct gases are removed from the plasma reaction chamber.

  14. Oxidized film structure and method of making epitaxial metal oxide structure

    DOEpatents

    Gan, Shupan [Richland, WA; Liang, Yong [Richland, WA

    2003-02-25

    A stable oxidized structure and an improved method of making such a structure, including an improved method of making an interfacial template for growing a crystalline metal oxide structure, are disclosed. The improved method comprises the steps of providing a substrate with a clean surface and depositing a metal on the surface at a high temperature under a vacuum to form a metal-substrate compound layer on the surface with a thickness of less than one monolayer. The compound layer is then oxidized by exposing the compound layer to essentially oxygen at a low partial pressure and low temperature. The method may further comprise the step of annealing the surface while under a vacuum to further stabilize the oxidized film structure. A crystalline metal oxide structure may be subsequently epitaxially grown by using the oxidized film structure as an interfacial template and depositing on the interfacial template at least one layer of a crystalline metal oxide.

  15. Ambient-Temperature Sputtering Of Composite Oxide Films

    NASA Technical Reports Server (NTRS)

    Thakoor, Sarita

    1992-01-01

    Technique for deposition of homogeneous films of multicomponent oxides on substrates at ambient temperature based on sequential sputter deposition of individual metal components, as alternating ultra-thin layers, from multiple targets. Substrates rotated over sputtering targets of lead, zirconium, and titanium. Dc-magnetron sputtering of constituent metals in reactive ambient of argon and oxygen leads to formation of the respective metal oxides intermixed on extremely fine scale in desired composition. Compatible with low-temperature microelectronic processing.

  16. Manganese oxide nanowires, films, and membranes and methods of making

    DOEpatents

    Suib, Steven Lawrence; Yuan, Jikang

    2011-02-15

    Nanowires, films, and membranes comprising ordered porous manganese oxide-based octahedral molecular sieves and methods of making the same are disclosed. A method for forming nanowires includes hydrothermally treating a chemical precursor composition in a hydrothermal treating solvent to form the nanowires, wherein the chemical precursor composition comprises a source of manganese cations and a source of counter cations, and wherein the nanowires comprise ordered porous manganese oxide-based octahedral molecular sieves.

  17. Ion beam-based characterization of multicomponent oxide thin films and thin film layered structures

    SciTech Connect

    Krauss, A.R.; Rangaswamy, M.; Lin, Yuping; Gruen, D.M. ); Schultz, J.A. ); Schmidt, H.K. ); Chang, R.P.H. . Dept. of Materials Science)

    1992-01-01

    Fabrication of thin film layered structures of multi-component materials such as high temperature superconductors, ferroelectric and electro-optic materials, and alloy semiconductors, and the development of hybrid materials requires understanding of film growth and interface properties. For High Temperature Superconductors, the superconducting coherence length is extremely short (5--15 [Angstrom]), and fabrication of reliable devices will require control of film properties at extremely sharp interfaces; it will be necessary to verify the integrity of thin layers and layered structure devices over thicknesses comparable to the atomic layer spacing. Analytical techniques which probe the first 1--2 atomic layers are therefore necessary for in-situ characterization of relevant thin film growth processes. However, most surface-analytical techniques are sensitive to a region within 10--40 [Angstrom] of the surface and are physically incompatible with thin film deposition and are typically restricted to ultra high vacuum conditions. A review of ion beam-based analytical methods for the characterization of thin film and multi-layered thin film structures incorporating layers of multicomponent oxides is presented. Particular attention will be paid to the use of time-of-flight techniques based on the use of 1- 15 key ion beams which show potential for use as nondestructive, real-time, in-situ surface diagnostics for the growth of multicomponent metal and metal oxide thin films.

  18. Ion beam-based characterization of multicomponent oxide thin films and thin film layered structures

    SciTech Connect

    Krauss, A.R.; Rangaswamy, M.; Lin, Yuping; Gruen, D.M.; Schultz, J.A.; Schmidt, H.K.; Chang, R.P.H.

    1992-11-01

    Fabrication of thin film layered structures of multi-component materials such as high temperature superconductors, ferroelectric and electro-optic materials, and alloy semiconductors, and the development of hybrid materials requires understanding of film growth and interface properties. For High Temperature Superconductors, the superconducting coherence length is extremely short (5--15 {Angstrom}), and fabrication of reliable devices will require control of film properties at extremely sharp interfaces; it will be necessary to verify the integrity of thin layers and layered structure devices over thicknesses comparable to the atomic layer spacing. Analytical techniques which probe the first 1--2 atomic layers are therefore necessary for in-situ characterization of relevant thin film growth processes. However, most surface-analytical techniques are sensitive to a region within 10--40 {Angstrom} of the surface and are physically incompatible with thin film deposition and are typically restricted to ultra high vacuum conditions. A review of ion beam-based analytical methods for the characterization of thin film and multi-layered thin film structures incorporating layers of multicomponent oxides is presented. Particular attention will be paid to the use of time-of-flight techniques based on the use of 1- 15 key ion beams which show potential for use as nondestructive, real-time, in-situ surface diagnostics for the growth of multicomponent metal and metal oxide thin films.

  19. Growth of ultrathin vanadium oxide films on Ag(100)

    NASA Astrophysics Data System (ADS)

    Nakamura, Takuya; Sugizaki, Yuichi; Ishida, Shuhei; Edamoto, Kazuyuki; Ozawa, Kenichi

    2016-07-01

    Vanadium oxide films were grown on Ag(100) by vanadium deposition in O2 and subsequent annealing at 450 °C. It was found that at least three types of ordered V oxide films, which showed (1 × 1), hexagonal, and (4 × 1) LEED patterns, were formed on Ag(100) depending on the O2 pressure during deposition and conditions during postannealing. The films with the hexagonal and (1 × 1) periodicities were characterized by photoelectron spectroscopy (PES) and near-edge X-ray absorption fine structure (NEXAFS) analysis. The film with the (1 × 1) periodicity was ascribed to a VO(100) film. On the other hand, the film with the hexagonal periodicity was found to be composed of V2O3, and the analysis of the LEED pattern revealed that the lattice parameter of the hexagonal lattice is 0.50 nm, which is very close to that of corundum V2O3(0001) (0.495 nm).

  20. Electrosynthesis and characterization of lead oxide thin films

    SciTech Connect

    Mahalingam, T. . E-mail: maha51@rediffmail.com; Velumani, S.; Raja, M.; Thanikaikarasan, S.; Chu, J.P.; Wang, S.F.; Kim, Y.D.

    2007-08-15

    Lead dioxide (PbO{sub 2}) is an important oxide material used extensively as anode material in batteries and fuel cells and its study has now taken new strides beyond the wide field of battery research. In the present study, lead dioxide films were electrodeposited onto precleaned copper substrate from nitrate baths. The film composition, morphology and structure were investigated using Energy Dispersive X-ray Analysis (EDX), scanning electron microscopy and X-ray diffraction techniques. The oxidation and reduction potential regions and the mechanism of lead dioxide film formation are discussed using cyclic voltammetry studies. X-ray diffraction results revealed tetragonal [{alpha}-PbO{sub 2} + {beta}-PbO{sub 2}] structures of the films which are influenced by bath temperature and solution pH value. EDAX studies show that the films deposited at higher bath temperatures and low solution pH values are rich in lead content and low in oxygen content. The effects of bath temperature and solution pH on the morphological features of lead dioxide films are also described.

  1. Magnetic Transparent Conducting Oxide Film And Method Of Making

    DOEpatents

    Windisch, Jr., Charles F.; Exarhos, Gregory J.; Sharma, Shiv K.

    2006-03-14

    Cobalt-nickel oxide films of nominal 100 nm thickness, and resistivity as low as 0.06 O·cm have been deposited by spin-casting from both aqueous and organic precursor solutions followed by annealing at 450° C. in air. An increase in film resistivity was found upon substitution of other cations (e.g., Zn2+, Al3+) for Ni in the spinel structure. However, some improvement in the mechanical properties of the films resulted. On the other hand, addition of small amounts of Li decreased the resistivity. A combination of XRD, XPS, UV/Vis and Raman spectroscopy indicated that NiCo2O4 is the primary conducting component and that the conductivity reaches a maximum at this stoichiometry. When x<0.67, NiO forms leading to an increase in resistivity; when x>0.67, the oxide was all spinel but the increased Co content lowered the conductivity.

  2. Multiferroic oxide thin films and heterostructures

    NASA Astrophysics Data System (ADS)

    Lu, Chengliang; Hu, Weijin; Tian, Yufeng; Wu, Tom

    2015-06-01

    Multiferroic materials promise a tantalizing perspective of novel applications in next-generation electronic, memory, and energy harvesting technologies, and at the same time they also represent a grand scientific challenge on understanding complex solid state systems with strong correlations between multiple degrees of freedom. In this review, we highlight the opportunities and obstacles in growing multiferroic thin films with chemical and structural integrity and integrating them in functional devices. Besides the magnetoelectric effect, multiferroics exhibit excellent resistant switching and photovoltaic properties, and there are plenty opportunities for them to integrate with other ferromagnetic and superconducting materials. The challenges include, but not limited, defect-related leakage in thin films, weak magnetism, and poor control on interface coupling. Although our focuses are Bi-based perovskites and rare earth manganites, the insights are also applicable to other multiferroic materials. We will also review some examples of multiferroic applications in spintronics, memory, and photovoltaic devices.

  3. Multiferroic oxide thin films and heterostructures

    SciTech Connect

    Lu, Chengliang E-mail: Tao.Wu@kaust.edu.sa; Hu, Weijin; Wu, Tom E-mail: Tao.Wu@kaust.edu.sa; Tian, Yufeng

    2015-06-15

    Multiferroic materials promise a tantalizing perspective of novel applications in next-generation electronic, memory, and energy harvesting technologies, and at the same time they also represent a grand scientific challenge on understanding complex solid state systems with strong correlations between multiple degrees of freedom. In this review, we highlight the opportunities and obstacles in growing multiferroic thin films with chemical and structural integrity and integrating them in functional devices. Besides the magnetoelectric effect, multiferroics exhibit excellent resistant switching and photovoltaic properties, and there are plenty opportunities for them to integrate with other ferromagnetic and superconducting materials. The challenges include, but not limited, defect-related leakage in thin films, weak magnetism, and poor control on interface coupling. Although our focuses are Bi-based perovskites and rare earth manganites, the insights are also applicable to other multiferroic materials. We will also review some examples of multiferroic applications in spintronics, memory, and photovoltaic devices.

  4. Impact of Rh-CeOx interaction on CO oxidation mechanisms

    NASA Astrophysics Data System (ADS)

    Ševčíková, Klára; Kolářová, Tatiana; Skála, Tomáš; Tsud, Nataliya; Václavů, Michal; Lykhach, Yaroslava; Matolín, Vladimír; Nehasil, Václav

    2015-03-01

    We have investigated the impact of electronic metal-support interaction on catalytic properties of Rh/CeOx system, i.e. its capacity for the reverse and direct oxygen spillover, in the context of CO oxidation. The studies were carried out on two types of samples consisting of Rh particles supported on polycrystalline nearly stoichiometric and partially reduced cerium oxide films using temperature programmed reaction, temperature programmed desorption, and conventional X-ray and resonant photoelectron spectroscopies. We have found that the electronic Rh-CeOx interaction leads to a buildup of a net positive charge on Rh particles supported on stoichiometric cerium oxide, and a net negative charge on Rh particles on reduced cerium oxide. The effect of the Rh-CeOx interaction is manifested in suppression of the reverse and direct oxygen spillover on Rh particles supported on partially reduced ceria.

  5. Perovskite Oxide Thin Film Growth, Characterization, and Stability

    NASA Astrophysics Data System (ADS)

    Izumi, Andrew

    Studies into a class of materials known as complex oxides have evoked a great deal of interest due to their unique magnetic, ferroelectric, and superconducting properties. In particular, materials with the ABO3 perovskite structure have highly tunable properties because of the high stability of the structure, which allows for large scale doping and strain. This also allows for a large selection of A and B cations and valences, which can further modify the material's electronic structure. Additionally, deposition of these materials as thin films and superlattices through techniques such as pulsed laser deposition (PLD) results in novel properties due to the reduced dimensionality of the material. The novel properties of perovskite oxide heterostructures can be traced to a several sources, including chemical intermixing, strain and defect formation, and electronic reconstruction. The correlations between microstructure and physical properties must be investigated by examining the physical and electronic structure of perovskites in order to understand this class of materials. Some perovskites can undergo phase changes due to temperature, electrical fields, and magnetic fields. In this work we investigated Nd0.5Sr 0.5MnO3 (NSMO), which undergoes a first order magnetic and electronic transition at T=158K in bulk form. Above this temperature NSMO is a ferromagnetic metal, but transitions into an antiferromagnetic insulator as the temperature is decreased. This rapid transition has interesting potential in memory devices. However, when NSMO is deposited on (001)-oriented SrTiO 3 (STO) or (001)-oriented (LaAlO3)0.3-(Sr 2AlTaO6)0.7 (LSAT) substrates, this transition is lost. It has been reported in the literature that depositing NSMO on (110)-oriented STO allows for the transition to reemerge due to the partial epitaxial growth, where the NSMO film is strained along the [001] surface axis and partially relaxed along the [11¯0] surface axis. This allows the NSMO film enough

  6. Indium oxide inverse opal films synthesized by structure replication method

    NASA Astrophysics Data System (ADS)

    Amrehn, Sabrina; Berghoff, Daniel; Nikitin, Andreas; Reichelt, Matthias; Wu, Xia; Meier, Torsten; Wagner, Thorsten

    2016-04-01

    We present the synthesis of indium oxide (In2O3) inverse opal films with photonic stop bands in the visible range by a structure replication method. Artificial opal films made of poly(methyl methacrylate) (PMMA) spheres are utilized as template. The opal films are deposited via sedimentation facilitated by ultrasonication, and then impregnated by indium nitrate solution, which is thermally converted to In2O3 after drying. The quality of the resulting inverse opal film depends on many parameters; in this study the water content of the indium nitrate/PMMA composite after drying is investigated. Comparison of the reflectance spectra recorded by vis-spectroscopy with simulated data shows a good agreement between the peak position and calculated stop band positions for the inverse opals. This synthesis is less complex and highly efficient compared to most other techniques and is suitable for use in many applications.

  7. Structural transformation of nickel hydroxide films during anodic oxidation

    SciTech Connect

    Crocker, R.W.; Muller, R.H.

    1992-05-01

    The transformation of anodically formed nickel hydroxide/oxy-hydroxide electrodes has been investigated. A mechanism is proposed for the anodic oxidation reaction, in which the reaction interface between the reduced and oxidized phases of the electrode evolves in a nodular topography that leads to inefficient utilization of the active electrode material. In the proposed nodular transformation model for the anodic oxidation reaction, nickel hydroxide is oxidized to nickel oxy-hydroxide in the region near the metal substrate. Since the nickel oxy-hydroxide is considerably more conductive than the surrounding nickel hydroxide, as further oxidation occurs, nodular features grow rapidly to the film/electrolyte interface. Upon emerging at the electrolyte interface, the reaction boundary between the nickel hydroxide and oxy-hydroxide phases spreads laterally across the film/electrolyte interface, creating an overlayer of nickel oxy-hydroxide and trapping uncharged regions of nickel hydroxide within the film. The nickel oxy-hydroxide overlayer surface facilitates the oxygen evolution side reaction. Scanning tunneling microscopy of the electrode in its charged state revealed evidence of 80 {endash} 100 Angstrom nickel oxy-hydroxide nodules in the nickel hydroxide film. In situ spectroscopic ellipsometer measurements of films held at various constant potentials agree quantitatively with optical models appropriate to the nodular growth and subsequent overgrowth of the nickel oxy-hydroxide phase. A two-dimensional, numerical finite difference model was developed to simulate the current distribution along the phase boundary between the charged and uncharged material. The model was used to explore the effects of the physical parameters that govern the electrode behavior. The ratio of the conductivities of the nickel hydroxide and oxy-hydroxide phases was found to be the dominant parameter in the system.

  8. Electrical properties of films of zinc oxide nanoparticles and its hybrid with reduced graphene oxide

    NASA Astrophysics Data System (ADS)

    Madhuri, K. Priya; Bramhaiah, K.; John, Neena S.

    2016-05-01

    Free-standing films of ZnO nanoparticles (NPs) and reduced graphene oxide (rGO)-ZnO NPs hybrid are prepared at a liquid/liquid interface. The films are characterized by UV-visible spectroscopy, X-ray diffraction, scanning electron microscopy and atomic force microscopy. ZnO film consists of spherical aggregated NPs while the hybrid film contains folded sheets of rGO with embedded ZnO NPs. Electrical properties of the films and its photoresponse in presence of UV radiation are investigated using current sensing atomic force microscopy (CSAFM) at nanoscale and bulk measurements using two probe methods. Enhancement in photocurrent is observed in both cases and the current imaging reveals an inhomogeneous contribution by different ZnO grains in the film.

  9. Study of the doping of thermally evaporated zinc oxide thin films with indium and indium oxide

    NASA Astrophysics Data System (ADS)

    Palimar, Sowmya; Bangera, Kasturi V.; Shivakumar, G. K.

    2013-12-01

    The present paper reports observations made on investigations carried out to study structural, optical and electrical properties of thermally evaporated ZnO thin films and their modulations on doping with metallic indium and indium oxide separately. ZnO thin film in the undoped state is found to have a very good conductivity of 90 Ω-1 cm-1 with an excellent transmittance of up to 90 % in the visible region. After doping with metallic indium, the conductivity of the film is found to be 580 Ω-1 cm-1, whereas the conductivity of indium oxide-doped films is increased up to 3.5 × 103 Ω-1 cm-1. Further, the optical band gap of the ZnO thin film is widened from 3.26 to 3.3 eV when doped with indium oxide and with metallic indium it decreases to 3.2 eV. There is no considerable change in the transmittance of the films after doping. All undoped and doped films were amorphous in nature with smooth and flat surface without significant modifications due to doping.

  10. Development of metal oxide impregnated stilbite thick film ethanol sensor

    NASA Astrophysics Data System (ADS)

    Mahabole, M. P.; Lakhane, M. A.; Choudhari, A. L.; Khairnar, R. S.

    2016-05-01

    This paper presents the study of the sensing efficiency of Titanium oxide/ Stilbite and Copper oxide /Stilbite composites towards detection of hazardous pollutants like ethanol. Stilbite based composites are prepared by physically mixing zeolite with metal oxides namely TiO2 and CuO with weight ratios of 25:75, 50:50 and 75:25. The resulting sensor materials are characterized by X-ray diffraction and Fourier Transform Infrared Spectroscopy techniques. Composite sensors are fabricated in the form of thick film by using screen printing technique. The effect of metal oxide concentration on various ethanol sensing parameters such as operating temperature, maximum uptake capacity and response/recovery time are investigated. The results indicate that metal oxide impregnated stilbite composites have great potential as low temperature ethanol sensor.

  11. Study of preparation method and oxidization/reduction effect on the performance of nickel-cerium oxide catalysts for aqueous-phase reforming of ethanol

    NASA Astrophysics Data System (ADS)

    Roy, B.; Leclerc, C. A.

    2015-12-01

    The effect of preparation method and oxidation state of the active metal on the catalytic activity of Ni-Ce-O catalysts was studied for aqueous phase reforming of ethanol. A sol-gel (SG) route and a solution combustion synthesis (SCS) method were used for the preparation of 10 wt% Ni loaded catalysts. The catalytic activity of three groups of catalysts; reduced at 425 °C (HR, metallic Ni), reduced at 1000 °C (FR, metallic Ni), and not reduced (NR, as NiO) were tested at different operating conditions. The difference in the metal particle sizes, governed by the preparation method, affects the catalytic efficiency most, not the reduced or oxidized state of Ni. The SG samples were superior for ethanol conversion and selectivity for H2 and CO2 compared to the SCS samples. The X-ray photoelectron spectroscopy (XPS) analysis of the samples demonstrated that the relative ratio of Ce2O3 to CeO2 increased inside the reactor. While Ni doping increases oxygen mobility in the Ce-O lattice, Ce3+ converts Ni2+ to metallic Ni inside the reactor. This can explain why the reduction stage for Ni-Ce-O system in APR is irrelevant. Higher oxygen mobility through the support helps oxidation of CO to CO2 leading to improved catalytic performance.

  12. Structure and chemical properties of molybdenum oxide thin films

    SciTech Connect

    Ramana, C. V.; Atuchin, V. V.; Pokrovsky, L. D.; Becker, U.; Julien, C. M.

    2007-07-15

    Molybdenum oxide (MoO{sub 3}) exhibits interesting structural, chemical, electrical, and optical properties, which are dependent on the growth conditions and the fabrication technique. In the present work, MoO{sub 3} films were produced by pulsed-laser deposition and dc magnetron sputtering under varying conditions of growth temperature (T{sub s}) and oxygen pressure (pO{sub 2}). The effect of growth conditions on the structure and chemical properties of MoO{sub 3} films was examined using x-ray diffraction, reflection high-energy electron diffraction, x-ray photoelectron spectroscopy, and infrared spectroscopic measurements. The analyses indicate that the microstructure of Mo oxide films is sensitive to T{sub s} and pO{sub 2}. The growth conditions were optimized to produce stoichiometric and highly textured polycrystalline MoO{sub 3} films. A comparison of the microstructure of MoO{sub 3} films grown using pulsed-laser deposition and sputtering methods is also presented.

  13. Fabrication of highly textured lithium cobalt oxide films by rapid thermal annealing

    DOEpatents

    Bates, John B.

    2003-04-29

    Systems and methods are described for fabrication of highly textured lithium cobalt oxide films by rapid thermal annealing. A method of forming a lithium cobalt oxide film includes depositing a film of lithium cobalt oxide on a substrate; rapidly heating the film of lithium cobalt oxide to a target temperature; and maintaining the film of lithium cobalt oxide at the target temperature for a target annealing time of at most, approximately 60 minutes. The systems and methods provide advantages because they require less time to implement and are, therefore less costly than previous techniques.

  14. Fabrication of highly textured lithium cobalt oxide films by rapid thermal annealing

    DOEpatents

    Bates, John B.

    2002-01-01

    Systems and methods are described for fabrication of highly textured lithium cobalt oxide films by rapid thermal annealing. A method of forming a lithium cobalt oxide film includes depositing a film of lithium cobalt oxide on a substrate; rapidly heating the film of lithium cobalt oxide to a target temperature; and maintaining the film of lithium cobalt oxide at the target temperature for a target annealing time of at most, approximately 60 minutes. The systems and methods provide advantages because they require less time to implement and are, therefore less costly than previous techniques.

  15. Fabrication of highly textured lithium cobalt oxide films by rapid thermal annealing

    DOEpatents

    Bates, John B.

    2003-05-13

    Systems and methods are described for fabrication of highly textured lithium cobalt oxide films by rapid thermal annealing. A method of forming a lithium cobalt oxide film includes depositing a film of lithium cobalt oxide on a substrate; rapidly heating the film of lithium cobalt oxide to a target temperature; and maintaining the film of lithium cobalt oxide at the target temperature for a target annealing time of at most, approximately 60 minutes. The systems and methods provide advantages because they require less time to implement and are, therefore less costly than previous techniques.

  16. Photoassisted oxidation of oil films on water

    SciTech Connect

    Heller, A.; Brock, J.R.

    1991-08-01

    The objective of the project is to develop TiO{sub 2}-based photocatalysts for the solar assisted oxidative dissolution of oil slicks. In a TiO{sub 2} crystal, absorption of a photon generates an electron-hole pair. The electron reacts with surface-adsorbed oxygen, reducing it to hydrogen peroxide; the hole directly oxidizes adsorbed organic compounds, usually via an intermediate OH radical. Since the density of TiO{sub 2} (3.8g/cc for anatase, 4.3 g/cc for rutile) is greater than that of either oil or seawater, TiO{sub 2} crystals are attached to inexpensive, engineered hollow glass microspheres to ensure flotation on the oil slick surface. Portions of the microsphere surface not covered by TiO{sub 2} are made oleophilic so that the microbeads will be preferentially attracted to the oil-air interface.

  17. Investigation and characterization of oxidized cellulose and cellulose nanofiber films

    NASA Astrophysics Data System (ADS)

    Yang, Han

    Over the last two decades, a large amount of research has focused on natural cellulose fibers, since they are "green" and renewable raw materials. Recently, nanomaterials science has attracted wide attention due to the large surface area and unique properties of nanoparticles. Cellulose certainly is becoming an important material in nanomaterials science, with the increasing demand of environmentally friendly materials. In this work, a novel method of preparing cellulose nanofibers (CNF) is being presented. This method contains up to three oxidation steps: periodate, chlorite and TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxyl) oxidation. The first two oxidation steps are investigated in the first part of this work. Cellulose pulp was oxidized to various extents by a two step-oxidation with sodium periodate, followed by sodium chlorite. The oxidized products can be separated into three different fractions. The mass ratio and charge content of each fraction were determined. The morphology, size distribution and crystallinity index of each fraction were measured by AFM, DLS and XRD, respectively. In the second part of this work, CNF were prepared and modified under various conditions, including (1) the introduction of various amounts of aldehyde groups onto CNF by periodate oxidation; (2) the carboxyl groups in sodium form on CNF were converted to acid form by treated with an acid type ion-exchange resin; (3) CNF were cross-linked in two different ways by employing adipic dihydrazide (ADH) as cross-linker and water-soluble 1-ethyl-3-[3-(dimethylaminopropyl)] carbodiimide (EDC) as carboxyl-activating agent. Films were fabricated with these modified CNF suspensions by vacuum filtration. The optical, mechanical and thermo-stability properties of these films were investigated by UV-visible spectrometry, tensile test and thermogravimetric analysis (TGA). Water vapor transmission rates (WVTR) and water contact angle (WCA) of these films were also studied.

  18. Zinc oxide doped graphene oxide films for gas sensing applications

    NASA Astrophysics Data System (ADS)

    Chetna, Kumar, Shani; Garg, A.; Chowdhuri, A.; Dhingra, V.; Chaudhary, S.; Kapoor, A.

    2016-05-01

    Graphene Oxide (GO) is analogous to graphene, but presence of many functional groups makes its physical and chemical properties essentially different from those of graphene. GO is found to be a promising material for low cost fabrication of highly versatile and environment friendly gas sensors. Selectivity, reversibility and sensitivity of GO based gas sensor have been improved by hybridization with Zinc Oxide nanoparticles. The device is fabricated by spin coating of deionized water dispersed GO flakes (synthesized using traditional hummer's method) doped with Zinc Oxide on standard glass substrate. Since GO is an insulator and functional groups on GO nanosheets play vital role in adsorbing gas molecules, it is being used as an adsorber. Additionally, on being exposed to certain gases the electric and optical characteristics of GO material exhibit an alteration in behavior. For the conductivity, we use Zinc Oxide, as it displays a high sensitivity towards conduction. The effects of the compositions, structural defects and morphologies of graphene based sensing layers and the configurations of sensing devices on the performances of gas sensors were investigated by Raman Spectroscopy, X-ray diffraction(XRD) and Keithley Sourcemeter.

  19. Electrosynthesis of highly transparent cobalt oxide water oxidation catalyst films from cobalt aminopolycarboxylate complexes.

    PubMed

    Bonke, Shannon A; Wiechen, Mathias; Hocking, Rosalie K; Fang, Xi-Ya; Lupton, David W; MacFarlane, Douglas R; Spiccia, Leone

    2015-04-24

    Efficient catalysis of water oxidation represents one of the major challenges en route to efficient sunlight-driven water splitting. Cobalt oxides (CoOx ) have been widely investigated as water oxidation catalysts, although the incorporation of these materials into photoelectrochemical devices has been hindered by a lack of transparency. Herein, the electrosynthesis of transparent CoOx catalyst films is described by utilizing cobalt(II) aminopolycarboxylate complexes as precursors to the oxide. These complexes allow control over the deposition rate and morphology to enable the production of thin, catalytic CoOx films on a conductive substrate, which can be exploited in integrated photoelectrochemical devices. Notably, under a bias of 1.0 V (vs. Ag/AgCl), the film deposited from [Co(NTA)(OH2 )2 ](-) (NTA=nitrilotriacetate) decreased the transmission by only 10 % at λ=500 nm, but still generated >80 % of the water oxidation current produced by a [Co(OH2 )6 ](2+) -derived oxide film whose transmission was only 40 % at λ=500 nm.

  20. Electrosynthesis of highly transparent cobalt oxide water oxidation catalyst films from cobalt aminopolycarboxylate complexes.

    PubMed

    Bonke, Shannon A; Wiechen, Mathias; Hocking, Rosalie K; Fang, Xi-Ya; Lupton, David W; MacFarlane, Douglas R; Spiccia, Leone

    2015-04-24

    Efficient catalysis of water oxidation represents one of the major challenges en route to efficient sunlight-driven water splitting. Cobalt oxides (CoOx ) have been widely investigated as water oxidation catalysts, although the incorporation of these materials into photoelectrochemical devices has been hindered by a lack of transparency. Herein, the electrosynthesis of transparent CoOx catalyst films is described by utilizing cobalt(II) aminopolycarboxylate complexes as precursors to the oxide. These complexes allow control over the deposition rate and morphology to enable the production of thin, catalytic CoOx films on a conductive substrate, which can be exploited in integrated photoelectrochemical devices. Notably, under a bias of 1.0 V (vs. Ag/AgCl), the film deposited from [Co(NTA)(OH2 )2 ](-) (NTA=nitrilotriacetate) decreased the transmission by only 10 % at λ=500 nm, but still generated >80 % of the water oxidation current produced by a [Co(OH2 )6 ](2+) -derived oxide film whose transmission was only 40 % at λ=500 nm. PMID:25826458

  1. Formation of zinc oxide films using submicron zinc particle dispersions

    SciTech Connect

    Rajachidambaram, Meena Suhanya; Varga, Tamas; Kovarik, Libor; Sanghavi, Rahul P.; Shutthanandan, V.; Thevuthasan, Suntharampillai; Han, Seungyeol; Chang, Chih-hung; Herman, Gregory S.

    2012-07-27

    The thermal oxidation of submicron metallic Zn particles was studied as a method to form nanostructured ZnO films. The particles used for this work were characterized by electron microscopy, x-ray diffraction and thermal analysis to evaluate the Zn-ZnO core shell structure, surface morphology, and oxidation characteristics. Significant nanostructural changes were observed for films annealed to 400 °C or higher, where nanoflakes, nanoribbons, nanoneedles and nanorods were formed as a result of stress induced fractures arising in the ZnO outer shell due to differential thermal expansion between the metallic Zn core and the ZnO shell. Mass transport occurs through these defects due to the high vapor pressure for metallic Zn at temperatures above 230 °C, whereupon the Zn vapor rapidly oxidizes in air to form the ZnO nanostructures. The Zn particles were also incorporated into zinc indium oxide precursor solutions to form thin film transistor test structures to evaluate the potential of forming nanostructured field effect sensors using simple solution processing.

  2. Pulsed organometallic beam epitaxy of complex oxide films

    SciTech Connect

    Duray, S.J.; Buchholz, D.B.; Song, S.N.; Richeson, D.S.; Ketterson, J.B.; Marks, T.J.; Chang, R.P.H. )

    1991-09-16

    We report the results of a pulsed organometallic beam epitaxy (POMBE) process for growing complex oxide films at low background gas pressure (10{sup {minus}4}--10{sup {minus}2} Torr) and low substrate temperature (600--680 {degree}C) using organometallic precursors in an oxygen plasma environment. Our results show that POMBE can extend the capability of organometallic chemical vapor deposition to growing complex oxide films with high precision both in composition and structure without the need for post-deposition oxidation and heat treatments. The growth of phase-pure, highly oriented Y-Ba-Cu-O superconducting oxide films {l brace}({ital T}{sub {ital c}} ({ital R}=0)=90.5 K) and {ital J}{sub {ital c}} (77 K, 50 K gauss)=1.1{times}10{sup 5} A/cm{sup 2}{r brace} is given as an example. Similar to the pulsed laser deposition process, the POMBE method has the potential for {ital in} {ital situ} processing of multilayer structures (e.g., junctions).

  3. Transition of oxide film configuration and the critical stress inferred by scanning probe microscopy at nanoscale

    NASA Astrophysics Data System (ADS)

    Fang, Xufei; Li, Yan; Zhang, Changxing; Dong, Xuelin; Feng, Xue

    2016-09-01

    Scanning probe microscopy (SPM) equipped in high temperature nanoindentation instrument is adopted to in situ characterize the oxide film growth on Ni-base single crystal at nanoscale. SPM images reveal a transition of oxide film configuration that the originally flat surface roughens during oxidation. Based on the stress-diffusion coupling effect during oxidation, the stress evolution in the oxide film and the evolution of surface configuration are analyzed. A new method to infer the critical stress in the oxide film at the transition point is proposed by measuring the undulated surface wavelength based on the surface morphology obtained by SPM.

  4. Properties of nano-structured cuprous oxide thin films fabricated by thermal oxidation of copper layer

    NASA Astrophysics Data System (ADS)

    Gevorgyan, Vladimir; Reymers, Anna; Nersesyan, Manuk; Nitsche, Serge; Giorgio, Suzanne; Karapetyan, Artak; Marine, Wladimir

    2011-07-01

    Among the potential photovoltaic devices based on semiconductor oxides as active layer is cuprous oxide (Cu2O). Although the theoretical limit of Cu2O solar cell efficiency is 20%, the best efficiency obtained up to now is only 2%. This is due to a very limited amount of work devoted to this semiconductor and only during last few years this material has been investigated for solar cells applications. In this work we report our results of optical, structural and surface morphology investigations of Cu2O films prepared by thermal oxidation of copper layer. The effects of oxidation temperature and oxygen partial pressure on surface morphology and crystalline structure of Cu2O films were studied. Scanning electron microscope results have shown that Cu2O films have microcrystalline structure with grain size of about 5-15 μm. Analysis of fine structure shows typical lattice spacing of cubic Cu2O structure. X-ray investigations have shown that the films consist of single Cu2O phase without any interstitial phase and have a nano-grain structure. The grains have an average dimensions about (33-41) nm. Optical investigations have shown that the absorption edge of prepared films is due to a direct allowed transition. The value of the optical band gap is 2.08 eV.

  5. Photoassisted oxidation of oil films on water

    SciTech Connect

    Heller, A.; Brock, J.R.

    1990-10-01

    The objective of the project is to develop a method for the solar assisted oxidation of oil slicks. A semiconducting photocatalyst, titanium dioxide, is used. Upon absorbing a photon, an electron-hole pair is generated in the TiO{sub 2} microcrystal. The electron reacts with surface-adsorbed oxygen, reducing it to hydrogen peroxide; the hole directly oxidizes adsorbed organic compounds. Titanium dioxide is denser than either oil or seawater; the density of its anatase phase is 3.8 and that of its rutile phase is 4.3. In order to keep the titanium dioxide at the air/oil interface, it is attached to a low density, floating material. The particles of the latter are sufficiently small to make the system economical. Specifically, the photocatalyst particles are attached to inexpensive hollow glass microbeads of about 100{mu}m diameter. Those areas of the microbeads that are not covered by photocatalyst are made oleophilic, so that the microbeads will follow the oil slick and not migrate to either the air/water or the water/oil interface.

  6. Growth and characterization of antimony doped tin oxide thin films

    NASA Astrophysics Data System (ADS)

    Shanthi, S.; Subramanian, C.; Ramasamy, P.

    1999-03-01

    Pure and antimony doped tin oxide thin films were deposited on glass and quartz plates by spray pyrolysis method. Structural, electrical and optical properties of these films were studied by varying the substrate temperature and antimony concentration. The best electro-optic properties obtained were, resistivity as low as 9×10 -4 Ω cm and average transmission of 80% in the visible region, at the substrate temperature of 400°C with the antimony concentration of 9 at%. While doping, change in preferred orientation was observed from [1 1 0] to [2 0 0]. The optical investigation showed that, depending upon the doping concentration, the antimony doped films had direct allowed transitions in the range 4.13-4.22 eV and indirect allowed transitions in the range 2.54-2.65 eV.

  7. Investigation of tungsten doped tin oxide thin film transistors

    NASA Astrophysics Data System (ADS)

    Yang, Jianwen; Meng, Ting; Yang, Zhao; Cui, Can; Zhang, Qun

    2015-11-01

    Tungsten doped tin oxide thin film transistors (TWO-TFTs) were fabricated by radio frequency magnetron sputtering. With TWO thin films as the channel layers, the TFTs show lower off-current and positive shift turn-on voltage than the intrinsic tin oxide TFTs, which can be explained by the reason that W doping is conducive to suppress the carrier concentration of the TWO channel layer. It is important to elect an appropriate channel thickness for improving the TFT performance. The optimum TFT performance in enhancement mode is achieved at W doping content of 2.7 at% and channel thickness of 12 nm, with the saturation mobility, turn-on voltage, subthreshold swing value and on-off current ratio of 5 cm2 V-1 s-1, 0.4 V, 0.4 V/decade and 2.4  ×  106, respectively.

  8. Manganese oxide nanowires, films, and membranes and methods of making

    DOEpatents

    Suib, Steven Lawrence; Yuan, Jikang

    2008-10-21

    Nanowires, films, and membranes comprising ordered porous manganese oxide-based octahedral molecular sieves, and methods of making, are disclosed. A single crystal ultra-long nanowire includes an ordered porous manganese oxide-based octahedral molecular sieve, and has an average length greater than about 10 micrometers and an average diameter of about 5 nanometers to about 100 nanometers. A film comprises a microporous network comprising a plurality of single crystal nanowires in the form of a layer, wherein a plurality of layers is stacked on a surface of a substrate, wherein the nanowires of each layer are substantially axially aligned. A free standing membrane comprises a microporous network comprising a plurality of single crystal nanowires in the form of a layer, wherein a plurality of layers is aggregately stacked, and wherein the nanowires of each layer are substantially axially aligned.

  9. Photocatalytic oxide films in the built environment

    NASA Astrophysics Data System (ADS)

    Österlund, Lars; Topalian, Zareh

    2014-11-01

    The possibility to increase human comfort in buildings is a powerful driving force for the introduction of new technology. Among other things our sense of comfort depends on air quality, temperature, lighting level, and the possibility of having visual contact between indoors and outdoors. Indeed there is an intimate connection between energy, comfort, and health issues in the built environment, leading to a need for intelligent building materials and green architecture. Photocatalytic materials can be applied as coatings, filters, and be embedded in building materials to provide self-cleaning, antibacterial, air cleaning, deodorizing, and water cleaning functions utilizing either solar light or artificial illumination sources - either already present in buildings, or by purposefully designed luminaries. Huge improvements in indoor comfort can thus be made, and also alleviate negative health effects associated with buildings, such as the sick-house syndrome. At the same time huge cost savings can be made by reducing maintenance costs. Photocatalytic oxides can be chemically modified by changing their acid-base surface properties, which can be used to overcome deactivation problems commonly encountered for TiO2 in air cleaning applications. In addition, the wetting properties of oxides can be tailored by surface chemical modifications and thus be made e.g. oleophobic and water repellent. Here we show results of surface acid modified TiO2 coatings on various substrates by means of photo-fixation of surface sulfate species by a method invented in our group. In particular, we show that such surface treatments of photocatalytic concrete made by mixing TiO2 nanoparticles in reactive concrete powders result in concrete surfaces with beneficial self-cleaning properties. We propose that such approaches are feasible for a number of applications in the built environment, including glass, tiles, sheet metals, plastics, etc.

  10. Genesis of a Cerium Oxide-Supported Gold Catalyst for CO Oxidation: Transformation of Mononuclear Gold Complexes into Clusters as Characterized by X-Ray Absorption Spectroscopy

    SciTech Connect

    Aguilar-Guerrero, V.; Lobo-Lapidus, R; Gates, B

    2009-01-01

    CeO{sub 2}-supported mononuclear gold species synthesized from Au(CH{sub 3}){sub 2}(acac) catalyzed CO oxidation at 353 K, with a turnover frequency of 6.5 x 10{sup -3} molecules of CO (Au atom s){sup -1} at CO and O{sub 2} partial pressures of 1.0 and 0.5 kPa, respectively. As the catalyst functioned in a flow reactor, the activity increased markedly so that within about 10 h the conversion of CO had increased from about 1% to almost 100%. Activated catalyst samples were characterized by X-ray absorption spectroscopy and found to incorporate clusters of gold, which increased in size, undergoing reduction, with increasing time of operation. The X-ray absorption near-edge structure spectrum of the catalyst used for the longest period was indistinguishable from that characterizing gold foil. Extended X-ray absorption fine structure data characterizing the catalyst after the longest period of operation indicated the presence of clusters of approximately 30 Au atoms each, on average. The evidence that the catalytic activity increased as the clusters grew is contrasted with earlier reports pointing to increasing activity of supported gold clusters as they were made smallerin a cluster size range largely exceeding ours.

  11. Oxidation Effects in Rare Earth Doped Topological Insulator Thin Films.

    PubMed

    Figueroa, A I; van der Laan, G; Harrison, S E; Cibin, G; Hesjedal, T

    2016-01-01

    The breaking of time-reversal symmetry (TRS) in topological insulators is a prerequisite for unlocking their exotic properties and for observing the quantum anomalous Hall effect (QAHE). The incorporation of dopants which exhibit magnetic long-range order is the most promising approach for TRS-breaking. REBiTe3, wherein 50% of the Bi is substitutionally replaced by a RE atom (RE = Gd, Dy, and Ho), is a predicted QAHE system. Despite the low solubility of REs in bulk crystals of a few %, highly doped thin films have been demonstrated, which are free of secondary phases and of high crystalline quality. Here we study the effects of exposure to atmosphere of rare earth-doped Bi2(Se, Te)3 thin films using x-ray absorption spectroscopy. We demonstrate that these RE dopants are all trivalent and effectively substitute for Bi(3+) in the Bi2(Se, Te)3 matrix. We find an unexpected high degree of sample oxidation for the most highly doped samples, which is not restricted to the surface of the films. In the low-doping limit, the RE-doped films mostly show surface oxidation, which can be prevented by surface passivation, encapsulation, or in-situ cleaving to recover the topological surface state. PMID:26956771

  12. Spatial atomic layer deposition of zinc oxide thin films.

    PubMed

    Illiberi, A; Roozeboom, F; Poodt, P

    2012-01-01

    Zinc oxide thin films have been deposited at high growth rates (up to ~1 nm/s) by spatial atomic layer deposition technique at atmospheric pressure. Water has been used as oxidant for diethylzinc (DEZ) at deposition temperatures between 75 and 250 °C. The electrical, structural (crystallinity and morphology), and optical properties of the films have been analyzed by using Hall, four-point probe, X-ray diffraction, scanning electron microscopy, spectrophotometry, and photoluminescence, respectively. All the films have c-axis (100) preferential orientation, good crystalline quality and high transparency (∼ 85%) in the visible range. By varying the DEZ partial pressure, the electrical properties of ZnO can be controlled, ranging from heavily n-type conductive (with 4 mOhm.cm resistivity for 250 nm thickness) to insulating. Combining the high deposition rates with a precise control of functional properties (i.e., conductivity and transparency) of the films, the industrially scalable spatial ALD technique can become a disruptive manufacturing method for the ZnO-based industry.

  13. Oxidation Effects in Rare Earth Doped Topological Insulator Thin Films

    PubMed Central

    Figueroa, A. I.; van der Laan, G.; Harrison, S. E.; Cibin, G.; Hesjedal, T.

    2016-01-01

    The breaking of time-reversal symmetry (TRS) in topological insulators is a prerequisite for unlocking their exotic properties and for observing the quantum anomalous Hall effect (QAHE). The incorporation of dopants which exhibit magnetic long-range order is the most promising approach for TRS-breaking. REBiTe3, wherein 50% of the Bi is substitutionally replaced by a RE atom (RE = Gd, Dy, and Ho), is a predicted QAHE system. Despite the low solubility of REs in bulk crystals of a few %, highly doped thin films have been demonstrated, which are free of secondary phases and of high crystalline quality. Here we study the effects of exposure to atmosphere of rare earth-doped Bi2(Se, Te)3 thin films using x-ray absorption spectroscopy. We demonstrate that these RE dopants are all trivalent and effectively substitute for Bi3+ in the Bi2(Se, Te)3 matrix. We find an unexpected high degree of sample oxidation for the most highly doped samples, which is not restricted to the surface of the films. In the low-doping limit, the RE-doped films mostly show surface oxidation, which can be prevented by surface passivation, encapsulation, or in-situ cleaving to recover the topological surface state. PMID:26956771

  14. Oxidative stability of LARC (tm)-TPI films

    NASA Technical Reports Server (NTRS)

    Hinkley, Jeffrey A.

    1992-01-01

    The oxidative aging of 50-micron-thick films of LARC-TPI was studied using conventional thermogravimetric techniques and measurements of plane-stress fracture toughness. It was shown that at high temperature, most of the toughness loss occurred very early relative to the weight loss. The difficulties of interpreting TGA results in this regime and the problems of extrapolations to long times are discussed.

  15. Hafnium carbide formation in oxygen deficient hafnium oxide thin films

    NASA Astrophysics Data System (ADS)

    Rodenbücher, C.; Hildebrandt, E.; Szot, K.; Sharath, S. U.; Kurian, J.; Komissinskiy, P.; Breuer, U.; Waser, R.; Alff, L.

    2016-06-01

    On highly oxygen deficient thin films of hafnium oxide (hafnia, HfO2-x) contaminated with adsorbates of carbon oxides, the formation of hafnium carbide (HfCx) at the surface during vacuum annealing at temperatures as low as 600 °C is reported. Using X-ray photoelectron spectroscopy the evolution of the HfCx surface layer related to a transformation from insulating into metallic state is monitored in situ. In contrast, for fully stoichiometric HfO2 thin films prepared and measured under identical conditions, the formation of HfCx was not detectable suggesting that the enhanced adsorption of carbon oxides on oxygen deficient films provides a carbon source for the carbide formation. This shows that a high concentration of oxygen vacancies in carbon contaminated hafnia lowers considerably the formation energy of hafnium carbide. Thus, the presence of a sufficient amount of residual carbon in resistive random access memory devices might lead to a similar carbide formation within the conducting filaments due to Joule heating.

  16. Oxidation of electrodeposited black chrome selective solar absorber films

    SciTech Connect

    Holloway, P.H.; Shanker, K.; Pettit, R.B.; Sowell, R.R.

    1980-01-01

    X-ray photoelectron and Auger electron spectroscopies have been used to study the composition and oxidation of electrodeposited black chrome films. The outer layer of the film is Cr/sub 2/O/sub 3/ with the inner layer being a continuously changing mixture of Cr + Cr/sub 2/O/sub 3/. Initially, approximately 40% by volume of the film is combined as Cr/sub 2/O/sub 3/, and the volume percentage of Cr/sub 2/O/sub 3/ increases to greater than 60% after only 136 hours at 250/sup 0/C. After approximately 3600 hours at 400/sup 0/C, the volume percentage of Cr/sub 2/O/sub 3/ increased to as high as 80%. The thermal emittance decreased approximately linearly with increasing oxide content, while the solar absorptance remained constant until the percentage of Cr/sub 2/O/sub 3/ exceeded approximately 70%. Oxidation was slower when the Cr/sup +3/ concentration in the plating bath was reduced from 16 g/l to 8 g/l, and when black chrome was deposited on stainless steel rather than sulfamate nickel.

  17. 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.

  18. 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

  19. Optical Characterization of Titanium-Vanadium Oxide Films

    NASA Astrophysics Data System (ADS)

    Kakiuchida, Hiroshi; Jin, Ping; Okada, Masahisa; Tazawa, Masato

    2007-02-01

    Composite thin films of titanium and vanadium oxides (TVO) with various compositions were deposited by rf magnetron sputtering. The TVO films, of which their crystalline structure, composition, and film morphology were characterized, were examined to determine the optical constants and thermochromic performance as a function of the compositional ratio. The optical constants were determined by ellipsometric analysis using a consistent model of the film structure, and it was found that optical constants at visible and near-infrared wavelengths monotonically decrease from the values of VO2 towards those of TiO2 with an increase in Ti content in the TVO. The gradual depression of thermochromic performance with an increase in Ti content was measured. The change in X-ray diffraction pattern with the compositional ratio suggests that VO2 and TiO2 in the TVO film form a solid solution, or in other words the TVO can be expressed by TixV1-xO2.

  20. Electrical properties of vanadium tungsten oxide thin films

    SciTech Connect

    Nam, Sung-Pill; Noh, Hyun-Ji; Lee, Sung-Gap; Lee, Young-Hie

    2010-03-15

    The vanadium tungsten oxide thin films deposited on Pt/Ti/SiO{sub 2}/Si substrates by RF sputtering exhibited good TCR and dielectric properties. The dependence of crystallization and electrical properties are related to the grain size of V{sub 1.85}W{sub 0.15}O{sub 5} thin films with different annealing temperatures. It was found that the dielectric properties and TCR properties of V{sub 1.85}W{sub 0.15}O{sub 5} thin films were strongly dependent upon the annealing temperature. The dielectric constants of the V{sub 1.85}W{sub 0.15}O{sub 5} thin films annealed at 400 {sup o}C were 44, with a dielectric loss of 0.83%. The TCR values of the V{sub 1.85}W{sub 0.15}O{sub 5} thin films annealed at 400 {sup o}C were about -3.45%/K.

  1. Highly Conducting Transparent Indium-Doped Zinc Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Singh, Budhi; Ghosh, Subhasis

    2014-09-01

    Highly conducting transparent indium-doped zinc oxide (IZO) thin films have been achieved by controlling different growth parameters using radio frequency magnetron sputtering. The structural, electrical, and optical properties of the IZO thin films have been investigated for varied indium content and growth temperature ( T G) in order to find out the optimum level of doping to achieve the highest conducting transparent IZO thin films. The highest mobility and carrier concentration of 11.5 cm2/V-s and 3.26 × 1020 cm-3, respectively, have been achieved in IZO doped with 2% indium. It has been shown that as T G of the 2% IZO thin films increase, more and more indium atoms are substituted into Zn sites leading to shift in (002) peaks towards higher angles which correspond to releasing the stress within the IZO thin film. The minimum resistivity of 5.3 × 10-4 Ω-cm has been achieved in 2% indium-doped IZO grown at 700°C.

  2. 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. PMID:26706928

  3. 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.

  4. Electrochemical deposition of conducting ruthenium oxide films from solution

    SciTech Connect

    Anderson, D.P.; Warren, L.F.

    1984-02-01

    In the last decade, ruthenium oxide, RuO /sub x/ (x less than or equal to 2), has been used extensively as the active anode electrocatalyst constituent for Cl/sub 2/ and O/sub 2/ evolution reactions, in chlorate production, and in metal electrowinning from mixed chloride-sulfate solutions. More recently, this material has been incorporated in several light-induced water electrolysis schemes and apparently possesses the ability to inhibit CdS photocorrosion by acting as a hole scavenger. The numerous applications for this catalyst material certainly warrant further studies of its electrochemical properties on a variety of substrates, e.g., semiconductors. The lack of a simple technique for controlled deposition of ruthenium oxide onto conducting substrates prompted us to investigate an electrochemical approach to this problem. We describe here a new way to electrochemically deposit conducting films of hydrated ruthenium oxide from an aqueous solution of the benzeneruthenium (II)aqua complex. The films slowly dissolve in aqueous electrolytes upon potential cycling, yet appear to be catalytic with regards to water oxidation.

  5. Cerium compounds as scintillators

    SciTech Connect

    Wojtowicz, A.J.; Berman, E.; Koepke, C.; Lempicki, A.

    1991-01-01

    Stoichiometric Ce-materials with negligible Ce-Ce interactions should have superior scintillator properties. We present two materials: CeF{sub 3} and Ce{sub x}La{sub 1-x}P{sub 5}O{sub 14}. While cerium trifluoride is a known scintillator, pentaphosphate is of a limited usefulness, except as a remarkable model material. We show that quenching in fluoride is responsible for loss of 50% of the light output and is the cause of the, so-called, ultra fast component (2 ns). Light output of fluoride (about 50% of BGO) could be significantly improved. Deeper understanding of Ce-systems is needed to fully exploit their potentials. 10 figs., 6 refs.

  6. Cerium compounds as scintillators

    SciTech Connect

    Wojtowicz, A.J.; Berman, E.; Koepke, C.; Lempicki, A.

    1991-12-31

    Stoichiometric Ce-materials with negligible Ce-Ce interactions should have superior scintillator properties. We present two materials: CeF{sub 3} and Ce{sub x}La{sub 1-x}P{sub 5}O{sub 14}. While cerium trifluoride is a known scintillator, pentaphosphate is of a limited usefulness, except as a remarkable model material. We show that quenching in fluoride is responsible for loss of 50% of the light output and is the cause of the, so-called, ultra fast component (2 ns). Light output of fluoride (about 50% of BGO) could be significantly improved. Deeper understanding of Ce-systems is needed to fully exploit their potentials. 10 figs., 6 refs.

  7. Isothermal thermogravimetric analysis of soybean oil oxidation correlated to thin film micro-oxidation test methods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A method of correlation between the Thin Film Micro-Oxidation (TFMO) test with isothermal thermogravimetric analysis is reported utilizing a soybean oil system. Utilizing a kinetic model, pseudo-rate constants and “activation energy” can be calculated from weight loss data. This model accounts for o...

  8. Self-formed copper oxide contact interlayer for high-performance oxide thin film transistors

    SciTech Connect

    Gao, Xu E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Aikawa, Shinya; Mitoma, Nobuhiko; Lin, Meng-Fang; Kizu, Takio; Tsukagoshi, Kazuhito E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Nabatame, Toshihide

    2014-07-14

    Oxide thin film transistor employing copper source/drain electrodes shows a small turn on voltage and reduced hysteresis. Cross-sectional high-resolution transmission electron microscopy image confirmed the formation of ∼4 nm CuO{sub x} related interlayer. The lower bond-dissociation energy of Cu-O compared to Si-O and In-O suggests that the interlayer was formed by adsorbing oxygen molecules from surrounding environment instead of getting oxygen atoms from the semiconductor film. The formation of CuO{sub x} interlayer acting as an acceptor could suppress the carrier concentration in the transistor channel, which would be utilized to control the turn on voltage shifts in oxide thin film transistors.

  9. Magnetic transparent conducting oxide film and method of making

    DOEpatents

    Windisch, Jr., Charles F.; Exarhos, Gregory J.; Sharma, Shiv K.

    2004-07-13

    Cobalt-nickel oxide films of nominal 100 nm thickness, and resistivity as low as 0.06 .OMEGA..multidot.cm have been deposited by spin-casting from both aqueous and organic precursor solutions followed by annealing at 450.degree. C. in air. Films deposited on sapphire substrates exhibit a refractive index of about 1.7 and are relatively transparent in the wavelength region from 0.6 to 10.0 .mu.m. They are also magnetic. The electrical and spectroscopic properties of the oxides have been studied as a function of x=Co/(Co+Ni) ratio. An increase in film resistivity was found upon substitution of other cations (e.g., Zn.sup.2+, Al.sup.3+) for Ni in the spinel structure. However, some improvement in the mechanical properties of the films resulted. On the other hand, addition of small amounts of Li decreased the resistivity. A combination of XRD, XPS, UV/Vis and Raman spectroscopy indicated that NiCo.sub.2 O.sub.4 is the primary conducting component and that the conductivity reaches a maximum at this stoichiometry. When x<0.67, NiO forms leading to an increase in resistivity; when x>0.67, the oxide was all spinel but the increased Co content lowered the conductivity. The influence of cation charge state and site occupancy in the spinel structure markedly affects calculated electron band structures and contributes to a reduction of p-type conductivity, the formation of polarons, and the reduction in population of mobile charge carriers that tend to limit transmission in the infrared.

  10. Thin copper oxide films prepared by ion beam sputtering with subsequent thermal oxidation: Application in chemiresistors

    NASA Astrophysics Data System (ADS)

    Horak, P.; Bejsovec, V.; Vacik, J.; Lavrentiev, V.; Vrnata, M.; Kormunda, M.; Danis, S.

    2016-12-01

    Copper oxide films were prepared by thermal oxidation of thin Cu films deposited on substrates by ion beam sputtering. The subsequent oxidation was achieved in the temperature range of 200 °C-600 °C with time of treatment from 1 to 7 h (with a 1-h step) in a furnace open to air. At temperatures 250 °C-600 °C, the dominant phase formed was CuO, while at 200 °C mainly the Cu2O phase was identified. However, the oxidation at 200 °C led to a more complicated composition - in the depth Cu2O phase was observed, though in the near-surface layer the CuO dominant phase was found with a significant presence of Cu(OH)2. A limited amount of Cu2O was also found in samples annealed at 600 °C. The sheet resistance RS of the as-deposited Cu sample was 2.22 Ω/□, after gradual annealing RS was measured in the range 2.64 MΩ/□-2.45 GΩ/□. The highest RS values were obtained after annealing at 300 °C and 350 °C, respectively. Oxygen depth distribution was studied using the 16O(α,α) nuclear reaction with the resonance at energy 3032 keV. It was confirmed that the higher oxidation degree of copper is located in the near-surface region. Preliminary tests of the copper oxide films as an active layer of a chemiresistor were also performed. Hydrogen and methanol vapours, with a concentration of 1000 ppm, were detected by the sensor at an operating temperature of 300 °C and 350 °C, respectively. The response of the sensors, pointed at the p-type conductivity, was improved by the addition of thin Pd or Au catalytic films to the oxidic film surface. Pd-covered films showed an increased response to hydrogen at 300 °C, while Au-covered films were more sensitive to methanol vapours at 350 °C.

  11. Chemical solution growth of ferroelectric oxide thin films and nanostructures.

    PubMed

    Bassiri-Gharb, Nazanin; Bastani, Yaser; Bernal, Ashley

    2014-04-01

    Chemical solution deposition (CSD) provides a low-cost, versatile approach for processing of thin and ultrathin ferroelectric films, as well as short and high aspect ratio ferroelectric nanostructures. This review discusses the state of the art in the processing of ferroelectric oxide thin films and nanostructures by CSD, with special emphasis on nucleation and growth phenomena. The effects of choice of precursor solution, substrate and bottom electrode stack, and thermal treatment conditions on the nucleation and growth are examined. Furthermore, methods to control ferroelectric thin film's microstructure, including phase content, texture, grain size and chemical homogeneity, are reviewed. Lastly, current CSD-based methods for processing of ferroelectric oxide nanostructures are presented with special consideration of the structural development, as well as advantages and shortcomings associated with each method. Lead zirconate-titanate, Pb(ZrxTi1-x)O3 (PZT), and barium titanate, BaTiO3 (BT), are used throughout the discussion, as specific examples for CSD processing of perovskite ferroelectrics.

  12. CSA doped polypyrrole-zinc oxide thin film sensor

    NASA Astrophysics Data System (ADS)

    Chougule, M. A.; Jundale, D. M.; Raut, B. T.; Sen, Shashwati; Patil, V. B.

    2013-02-01

    The polypyrrole-zinc oxide (PPy-ZnO) hybrid sensor doped with different weight ratios of camphor sulphonic acid (CSA) were prepared by spin coating technique. These CSA doped PPy-ZnO hybrids were characterized by field emission scanning electron microscope (FESEM) and fourier transform infrared (FTIR) which proved the formation of polypyrrole, PPy-ZnO and the interaction between polypyrrole - ZnO (PPy-ZnO) hybrid with CSA doping. The gas sensing properties of the PPy-ZnO hybrid films doped with CSA have been studied for oxidizing (NO2) as well as reducing (H2S, NH3, CH4OH and CH3OH) gases at room temperature. We demonstrate that CSA doped PPy-ZnO hybrid films are highly selective to NO2 along with high-sensitivity at low concentration (80% to 100 ppm) and better stability, which suggested that the CSA doped PPy-ZnO hybrid films are potential candidate for NO2 detection at room temperature.

  13. Chemical solution growth of ferroelectric oxide thin films and nanostructures.

    PubMed

    Bassiri-Gharb, Nazanin; Bastani, Yaser; Bernal, Ashley

    2014-04-01

    Chemical solution deposition (CSD) provides a low-cost, versatile approach for processing of thin and ultrathin ferroelectric films, as well as short and high aspect ratio ferroelectric nanostructures. This review discusses the state of the art in the processing of ferroelectric oxide thin films and nanostructures by CSD, with special emphasis on nucleation and growth phenomena. The effects of choice of precursor solution, substrate and bottom electrode stack, and thermal treatment conditions on the nucleation and growth are examined. Furthermore, methods to control ferroelectric thin film's microstructure, including phase content, texture, grain size and chemical homogeneity, are reviewed. Lastly, current CSD-based methods for processing of ferroelectric oxide nanostructures are presented with special consideration of the structural development, as well as advantages and shortcomings associated with each method. Lead zirconate-titanate, Pb(ZrxTi1-x)O3 (PZT), and barium titanate, BaTiO3 (BT), are used throughout the discussion, as specific examples for CSD processing of perovskite ferroelectrics. PMID:24121276

  14. Effect of Multiply Charged Ions on the Refractive Index of Titanium Oxide Films and an Application to Decorative Films

    NASA Astrophysics Data System (ADS)

    Suzuki, Akira

    2000-03-01

    In previous reports, higher charged ions are induced by higher voltage discharge, and harder films such as TiN, (Ti,Al)N and TiC are obtained by the higher voltage discharge method. The effect of multiply charged ions was confirmed in previous experiments. Multiply charged ions will affect physical properties other than hardness. In this study, the refractive index of titanium oxide films is investigated as a function of the discharge voltage. A high-refractive-index film is obtained by the high-voltage discharge method under various deposition conditions. The high-refractive-index film is applied to a reflection-increasing film, e.g., reflector for optical pumping of a laser beam. A reddish film can be obtained by depositing TiCN film; the film is applied to decorative goods to achieve a copper-like color. However, the reddish color of TiCN is inferior to that of films which are obtained by anodic oxidation or painting. If the reddishness of TiCN film is increased, the frequency of application to decorative goods is expected to increase. In this study, TiO2 film is applied to increase the reddishness of TiCN film for use in decorative goods. By depositing TiO2 film on TiCN, the reddishness is successfully increased from 8.4 to 34.9 with respect to the a* value which expresses red in the L* a* b* color space.

  15. Solution-Processed Indium Oxide Based Thin-Film Transistors

    NASA Astrophysics Data System (ADS)

    Xu, Wangying

    Oxide thin-film transistors (TFTs) have attracted considerable attention over the past decade due to their high carrier mobility and excellent uniformity. However, most of these oxide TFTs are usually fabricated using costly vacuum-based techniques. Recently, the solution processes have been developed due to the possibility of low-cost and large-area fabrication. In this thesis, we have carried out a detailed and systematic study of solution-processed oxide thin films and TFTs. At first, we demonstrated a passivation method to overcome the water susceptibility of solution-processed InZnO TFTs by utilizing octadecylphosphonic acid (ODPA) self-assembled monolayers (SAMs). The unpassivated InZnO TFTs exhibited large hysteresis in their electrical characteristics due to the adsorbed water at the semiconductor surface. Formation of a SAM of ODPA on the top of InZnO removed water molecules weakly absorbed at the back channel and prevented water diffusion from the surroundings. Therefore the passivated devices exhibited significantly reduced hysteretic characteristics. Secondly, we developed a simple spin-coating approach for high- k dielectrics (Al2O3, ZrO2, Y 2O3 and TiO2). These materials were used as gate dielectrics for solution-processed In2O3 or InZnO TFTs. Among the high-k dielectrics, the Al2O3-based devices showed the best performance, which is attributed to the smooth dielectric/semiconductor interface and the low interface trap density besides its good insulating property. Thirdly, the formation and properties of Al2O3 thin films under various annealing temperatures were intensively studied, revealing that the sol-gel-derived Al2O3 thin film undergoes the decomposition of organic residuals and nitrate groups, as well as conversion of aluminum hydroxides to form aluminum oxide. Besides, the Al2O 3 film was used as gate dielectric for solution-processed oxide TFTs, resulting in high mobility and low operating voltage. Finally, we proposed a green route for

  16. Carbon nanotube film synthesized from ethanol and its oxidation behavior in air

    NASA Astrophysics Data System (ADS)

    Ren, Yan; Ma, Wen-Jun; Zeng, Qing-Sheng; Li, Jin-Zhu; Dong, Hai-Bo; Zhou, Wei-Ya

    2012-09-01

    In this paper, we propose an efficient way to synthesize carbon nanotube films using ferrocene and ethanol. The as-grown film is free-standing, semi-transparent, and of macro scale size. The tubes in the film are mostly single- or double-walled. The oxidation behavior of the film is studied via Raman spectroscopy, and the result indicates that the inner wall of the double-walled tube is effectively protected from oxidation by the outer wall.

  17. Structure formation upon reactive direct current magnetron sputtering of transition metal oxide films

    SciTech Connect

    Ngaruiya, J.M.; Kappertz, O.; Mohamed, S.H.; Wuttig, M.

    2004-08-02

    A comparative study of reactive direct current magnetron sputtering for different transition metal oxides reveals crystalline films at room temperature for group 4 and amorphous films for groups 5 and 6. This observation cannot be explained by the known growth laws and is attributed to the impact of energetic particles, originating from the oxidized target, on the growing film. This scenario is supported by measured target characteristics, the evolution of deposition stress of the films, and the observed backsputtering.

  18. Highly conductive grain boundaries in copper oxide thin films

    NASA Astrophysics Data System (ADS)

    Deuermeier, Jonas; Wardenga, Hans F.; Morasch, Jan; Siol, Sebastian; Nandy, Suman; Calmeiro, Tomás; Martins, Rodrigo; Klein, Andreas; Fortunato, Elvira

    2016-06-01

    High conductivity in the off-state and low field-effect mobility compared to bulk properties is widely observed in the p-type thin-film transistors of Cu2O, especially when processed at moderate temperature. This work presents results from in situ conductance measurements at thicknesses from sub-nm to around 250 nm with parallel X-ray photoelectron spectroscopy. An enhanced conductivity at low thickness is explained by the occurrence of Cu(II), which is segregated in the grain boundary and locally causes a conductivity similar to CuO, although the surface of the thick film has Cu2O stoichiometry. Since grains grow with an increasing film thickness, the effect of an apparent oxygen excess is most pronounced in vicinity to the substrate interface. Electrical properties of Cu2O grains are at least partially short-circuited by this effect. The study focuses on properties inherent to copper oxide, although interface effects cannot be ruled out. This non-destructive, bottom-up analysis reveals phenomena which are commonly not observable after device fabrication, but clearly dominate electrical properties of polycrystalline thin films.

  19. Oxidation of rubrene thin films: an electronic structure study.

    PubMed

    Sinha, Sumona; Wang, C-H; Mukherjee, M; Mukherjee, T; Yang, Y-W

    2014-12-30

    The performances of organic semiconductor devices are crucially linked with their stability at the ambient atmosphere. The evolution of electronic structures of 20 nm thick rubrene films exposed to ambient environment with time has been studied by UV and X-ray photoemission spectroscopy (UPS and XPS), near edge X-ray absorption fine structure (NEXAFS) spectroscopy, and density functional theory (DFT). XPS, NEXAFS data, and DFT calculated values suggest the formation of rubrene-epoxide and rubrene-endoperoxide through reaction of tetracene backbone with oxygen of ambient environment. Angle dependent XPS measurement indicates that the entire probed depth of the films reacts with oxygen by spending only about 120 min in ambient environment. The HOMO peak of pristine rubrene films almost disappears by exposure of 120 min to ambient environment. The evolution of the valence band (occupied states) and NEXAFS (unoccupied states) spectra indicates that the films become more insulating with exposure as the HOMO-LUMO gap increases on oxidation. Oxygen induced chemical reaction completely destroys the delocalized nature of the electron distribution in the tetracene backbone of rubrene. The results are relevant to the performance and reliability of rubrene based devices in the environment. PMID:25383646

  20. Surfactant-assisted ultrasonic spray pyrolysis of nickel oxide and lithium-doped nickel oxide thin films, toward electrochromic applications

    NASA Astrophysics Data System (ADS)

    Denayer, Jessica; Bister, Geoffroy; Simonis, Priscilla; Colson, Pierre; Maho, Anthony; Aubry, Philippe; Vertruyen, Bénédicte; Henrist, Catherine; Lardot, Véronique; Cambier, Francis; Cloots, Rudi

    2014-12-01

    Lithium-doped nickel oxide and undoped nickel oxide thin films have been deposited on FTO/glass substrates by a surfactant-assisted ultrasonic spray pyrolysis. The addition of polyethylene glycol in the sprayed solution has led to improved uniformity and reduced light scattering compared to films made without surfactant. Furthermore, the presence of lithium ions in NiO films has resulted in improved electrochromic performances (coloration contrast and efficiency), but with a slight decrease of the electrochromic switching kinetics.

  1. IR Ellipsometry on RF sputtered Permalloy Oxide thin films

    NASA Astrophysics Data System (ADS)

    Cui, Yubo; Geerts, Wilhelmus; Twagirayezu, Fidele; Zollner, Stefan

    2015-03-01

    Recently several electronic devices have achieved significant enhancements that have been attributed to an oxidized NiFe layer. A study on lateral spin valves, was found to have an increased magnetoresistance after leaving it exposed to air. The enhancements were attributed to the partly oxidation of a NiFe layer. Even more recently the turn on voltages of Hematite based water splitting devices was lowered to record low of .61 V with the addition of an amorphous NiFeOx layer. We investigated the optical properties of Ni80Fe20-oxide thin films that were deposited by reactive RF sputtering on quartz and Si/SiO2 substrates. Deposition was performed in an AJA Magnetron System using an Ar gas flow of 8 sccm and an oxygen gas flow of 2 sccm for different substrate temperatures (24-600 degrees Celsius). The optical properties in the visible spectrum and the film thickness were measured using a Woollam M2000 variable angle spectroscopic ellipsometer. Additional measurements were performed with a Woollam IR-VASE from 1.7 to 30 micrometer. The measurement results show the existence of a phonon peak around 382 cm-1 slightly red-shifted from the 390 cm-1 phonon peak of single crystalline NiO. XRD spectra did only reveal X-ray peaks of the rocksalt structure. This work was partly funded by National Science Foundation (DMR-1104934). Use of the facilities of the CINT at Sandia National Lab is acknowledged.

  2. Oxide Film Aging on Alloy 22 in Halide Containing Solutions

    SciTech Connect

    Rodriguez, Martin A.; Carranza, Ricardo M.; Rebak, Raul B.

    2007-07-01

    Passive and corrosion behaviors of Alloy 22 in chloride and fluoride containing solutions, changing the heat treatment of the alloy, the halide concentration and the pH of the solutions at 90 deg. C, was investigated. The study was implemented using electrochemical techniques, which included open circuit potential monitoring over time, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements carried out at open circuit and at passivity potentials. Corrosion rates obtained by EIS measurements after 24 h immersion in naturally aerated solutions were below 0.5 {mu}m/year. The corrosion rates were practically independent of solution pH, alloy heat treatment and halide ion nature and concentration. EIS low frequency resistance values increased with applied potential in the passive domain and with polarization time in pH 6 - 1 M NaCl at 90 deg. C. This effect was attributed to an increase in the oxide film thickness and oxide film aging. High frequency capacitance measurements indicated that passive oxide on Alloy 22 presented a double n-type/p-type semiconductor behavior in the passive potential range. (authors)

  3. Studies on nickel-tungsten oxide thin films

    SciTech Connect

    Usha, K. S.; Sivakumar, R.; Sanjeeviraja, C.

    2014-10-15

    Nickel-Tungsten oxide (95:5) thin films were prepared by rf sputtering at 200W rf power with various substrate temperatures. X-ray diffraction study reveals the amorphous nature of films. The substrate temperature induced decrease in energy band gap with a maximum transmittance of 71%1 was observed. The Micro-Raman study shows broad peaks at 560 cm{sup −1} and 1100 cm{sup −1} correspond to Ni-O vibration and the peak at 860 cm{sup −1} can be assigned to the vibration of W-O-W bond. Photoluminescence spectra show two peaks centered on 420 nm and 485 nm corresponding to the band edge emission and vacancies created due to the addition of tungsten, respectively.

  4. High angular sensitivity thin film tin oxide sensor

    NASA Astrophysics Data System (ADS)

    Kaur, Davinder; Madaan, Divya; Sharma, V. K.; Kapoor, A.

    2016-05-01

    We present theoretical anlaysis of a thin film SnO2 (Tin Oxide) sensor for the measurement of variation in the refractive index of the bulk media. It is based on lossy mode resonance between the absorbing thin film lossy modes and the evanescent wave. Also the addition of low index dielectric matching layer between the prism and the lossy waveguiding layer future increase the angular sensitivity and produce an efficient refractive index sensor. The angular interrogation is done and obtained sensitivity is 110 degree/RIU. Theoretical analysis of the proposed sensor based on Fresnel reflection coefficients is presented. This enhanced sensitivity will further improve the monitoring of biomolecular interactions and the higher sensitivity of the proposed configurations makes it to be a much better option to be employed for biosensing applications.

  5. Hybrid films with graphene oxide and metal nanoparticles could now replace indium tin oxide.

    PubMed

    Varela-Rizo, Helena; Martín-Gullón, Ignacio; Terrones, Mauricio

    2012-06-26

    Graphene oxide (G-O), a highly oxidized sheet of sp(2)-hybridized carbon with insulating electrical properties, can be transformed into graphene if it is adequately reduced. In the past, researchers believed that reduced G-O (rG-O) could be highly conducting, but it has been shown that the presence of extended vacancies and defects within rG-O negatively affect its electrical transport. Although these observations indicated that rG-O could not be used in the fabrication of any electronic device, in this issue of ACS Nano, Ruoff's group demonstrates that rG-O can indeed be used for producing efficient transparent conducting films (TCFs) if the rG-O material is coupled with Au nanoparticles (Au-NPs) and Ag nanowires (Ag-NWs). The work further demonstrates that these hybrid films containing zero-dimensional (Au-NPs), one-dimensional (Ag-NWs), and two-dimensional (rG-O) elements exhibit high optical transmittance (e.g., 90%) and low sheet resistance (20-30 Ω/□), with values comparable to those of indium tin oxide (ITO) films. In addition, Ruoff's group notes that the presence of Ag-NWs and rG-O in the films showed antibacterial properties, thus demonstrating that it is now possible to produce flexible TCFs with bactericidal functions. The data show that smart hybrid films containing rG-O and different types of NPs and NWs could be synthesized easily and could result in smart films with unprecedented functions and applications.

  6. Vibrational spectra of CO adsorbed on oxide thin films: A tool to probe the surface defects and phase changes of oxide thin films

    SciTech Connect

    Savara, Aditya

    2014-03-15

    Thin films of iron oxide were grown on Pt(111) single crystals using cycles of physical vapor deposition of iron followed by oxidative annealing in an ultrahigh vacuum apparatus. Two procedures were utilized for film growth of ∼15–30 ML thick films, where both procedures involved sequential deposition+oxidation cycles. In procedure 1, the iron oxide film was fully grown via sequential deposition+oxidation cycles, and then the fully grown film was exposed to a CO flux equivalent to 8 × 10{sup −7} millibars, and a vibrational spectrum of adsorbed CO was obtained using infrared reflection-absorption spectroscopy. The vibrational spectra of adsorbed CO from multiple preparations using procedure 1 show changes in the film termination structure and/or chemical nature of the surface defects—some of which are correlated with another phase that forms (“phase B”), even before enough of phase B has formed to be easily detected using low energy electron diffraction (LEED). During procedure 2, CO vibrational spectra were obtained between deposition+oxidation cycles, and these spectra show that the film termination structure and/or chemical nature of the surface defects changed as a function of sequential deposition+oxidation cycles. The authors conclude that measurement of vibrational spectra of adsorbed CO on oxide thin films provides a sensitive tool to probe chemical changes of defects on the surface and can thus complement LEED techniques by probing changes not visible by LEED. Increased use of vibrational spectra of adsorbed CO on thin films would enable better comparisons between films grown with different procedures and by different groups.

  7. Stress generation in thermally grown oxide films. [oxide scale spalling from superalloy substrates

    NASA Technical Reports Server (NTRS)

    Kumnick, A. J.; Ebert, L. J.

    1981-01-01

    A three dimensional finite element analysis was conducted, using the ANSYS computer program, of the stress state in a thin oxide film thermally formed on a rectangular piece of NiCrAl alloy. The analytical results indicate a very high compressive stress in the lateral directions of the film (approximately 6200 MPa), and tensile stresses in the metal substrate that ranged from essentially zero to about 55 MPa. It was found further that the intensity of the analytically determined average stresses could be approximated reasonably well by the modification of an equation developed previously by Oxx for stresses induced into bodies by thermal gradients.

  8. 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.

  9. Anodic Oxidation in Aluminum Electrode by Using Hydrated Amorphous Aluminum Oxide Film as Solid Electrolyte under High Electric Field.

    PubMed

    Yao, Manwen; Chen, Jianwen; Su, Zhen; Peng, Yong; Zou, Pei; Yao, Xi

    2016-05-01

    Dense and nonporous amorphous aluminum oxide (AmAO) film was deposited onto platinized silicon substrate by sol-gel and spin coating technology. The evaporated aluminum film was deposited onto the AmAO film as top electrode. The hydrated AmAO film was utilized as a solid electrolyte for anodic oxidation of the aluminum electrode (Al) film under high electric field. The hydrated AmAO film was a high efficiency electrolyte, where a 45 nm thick Al film was anodized completely on a 210 nm thick hydrated AmAO film. The current-voltage (I-V) characteristics and breakdown phenomena of a dry and hydrated 210 nm thick AmAO film with a 150 nm thick Al electrode pad were studied in this work. Breakdown voltage of the dry and hydrated 210 nm thick AmAO film were 85 ± 3 V (405 ± 14 MV m(-1)) and 160 ± 5 V (762 ± 24 MV m(-1)), respectively. The breakdown voltage of the hydrated AmAO film increased about twice, owing to the self-healing behavior (anodic oxidation reaction). As an intuitive phenomenon of the self-healing behavior, priority anodic oxidation phenomena was observed in a 210 nm thick hydrated AmAO film with a 65 nm thick Al electrode pad. The results suggested that self-healing behavior (anodic oxidation reaction) was occurring nearby the defect regions of the films during I-V test. It was an effective electrical self-healing method, which would be able to extend to many other simple and complex oxide dielectrics and various composite structures.

  10. High temperature nitrogen oxides sensing enabled by indium oxide thin films

    NASA Astrophysics Data System (ADS)

    Kannan, Srinivasan

    Generation of power using fossil fuel combustion invariably results in formation of undesirable gas species (NOx, SOx, CO, CO2, etc.) at high-temperatures which are harmful to the environment. Thus, there is a continual need to develop sensitive, responsive, stable, selective, robust and low-cost sensor systems and sensor materials for combustion monitoring. This work investigates the viability of microfabricated NO x sensors based on sputtered indium oxide (In2O3) utilizing microhotplate structures. The material becomes resistive when exposed to oxidizing gases like NOx, with its conductivity dependent upon the temperature, partial pressure of the test gas and morphological structure. We believe this device would help increase efficiency and decrease emissions through improved combustion process control, leading to a comparably economic and responsive sensor. In this work, more than 600 sensors were fabricated and tested, including RF and pulsed-DC sputtered films. About 50 unique sensor conditions were characterized and related to the gas sensor response. The sensor conditions included deposition parameters (power, pressure, time, etc.) and postdeposition processes (anneals, promoter layers, etc.). In2O3 thin films were RF sputter deposited on microhotplate structures with different thickness (40 to 300 nm) in pure Ar. Additionally, a combination of reactive and RF sputtering of In2O3 material was-deposited in Ar and O2 (10% and 25%) mixture. In2O3 films without promoter layers and with gold or TiOx promoter layers (~ 3 nm) were investigated for NOx sensing. Selectivity, stability and repeatability of indium oxide (In2O3) thin film sensor to detect NOx (25 ppm) in presence of other exhaust gas pollutants including H2, NH3 and CO2 at high operating temperatures (greater than 350 °C) was investigated in N2 carrier gas. In2O 3 films (150nm thick) deposited in Ar and O2 (25% O 2) presented the highest response (S ~ 50) to 25 ppm NOx at 500 °C when compared to films

  11. Preparation of cerium halide solvate complexes

    DOEpatents

    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.

  12. Effect of Oxidation Condition on Growth of N: ZnO Prepared by Oxidizing Sputtering Zn-N Film

    NASA Astrophysics Data System (ADS)

    Qin, Xuesi; Li, Guojian; Xiao, Lin; Chen, Guozhen; Wang, Kai; Wang, Qiang

    2016-06-01

    Nitrogen-doped zinc oxide (N: ZnO) films have been prepared by oxidizing reactive RF magnetron-sputtering zinc nitride (Zn-N) films. The effect of oxidation temperature and oxidation time on the growth, transmittance, and electrical properties of the film has been explored. The results show that both long oxidation time and high oxidation temperature can obtain the film with a good transmittance (over 80 % for visible and infrared light) and a high carrier concentration. The N: ZnO film exhibits a special growth model with the oxidation time and is first to form a N: ZnO particle on the surface, then to become a N: ZnO layer, and followed by the inside Zn-N segregating to the surface to oxidize N: ZnO. The surface particle oxidized more adequately than the inside. However, the X-ray photoemission spectroscopy results show that the lower N concentration results in the lower N substitution in the O lattice (No). This leads to the formation of n-type N: ZnO and the decrease of carrier concentration. Thus, this method can be used to tune the microstructure, optical transmittance, and electrical properties of the N: ZnO film.

  13. Effect of Oxidation Condition on Growth of N: ZnO Prepared by Oxidizing Sputtering Zn-N Film.

    PubMed

    Qin, Xuesi; Li, Guojian; Xiao, Lin; Chen, Guozhen; Wang, Kai; Wang, Qiang

    2016-12-01

    Nitrogen-doped zinc oxide (N: ZnO) films have been prepared by oxidizing reactive RF magnetron-sputtering zinc nitride (Zn-N) films. The effect of oxidation temperature and oxidation time on the growth, transmittance, and electrical properties of the film has been explored. The results show that both long oxidation time and high oxidation temperature can obtain the film with a good transmittance (over 80 % for visible and infrared light) and a high carrier concentration. The N: ZnO film exhibits a special growth model with the oxidation time and is first to form a N: ZnO particle on the surface, then to become a N: ZnO layer, and followed by the inside Zn-N segregating to the surface to oxidize N: ZnO. The surface particle oxidized more adequately than the inside. However, the X-ray photoemission spectroscopy results show that the lower N concentration results in the lower N substitution in the O lattice (No). This leads to the formation of n-type N: ZnO and the decrease of carrier concentration. Thus, this method can be used to tune the microstructure, optical transmittance, and electrical properties of the N: ZnO film.

  14. Thermally evaporated mechanically hard tin oxide thin films for opto-electronic apllications

    NASA Astrophysics Data System (ADS)

    Tripathy, Sumanta K.; Rajeswari, V. P.

    2014-01-01

    Tungsten doped tin oxide (WTO) and Molybdenum doped tin oxide (MoTO) thin film were deposited on corn glass by thermal evaporation method. The films were annealed at 350°C for one hour. Structural analysis using Xray diffraction data shows both the films are polycrystalline in nature with monoclinic structure of tin oxide, Sn3O4, corresponding to JCPDS card number 01-078-6064. SEM photograph showed that both the films have spherical grains with size in the range of 20-30 nm. Compositional analysis was carried out using EDS which reveals the presence of Sn, O and the dopant Mo/W only thereby indicating the absence of any secondary phase in the films. The films are found to contain nearly 6 wt% of Mo, 8 wt% of W as dopants respectively. The transmission pattern for both the films in the spectral range 200 - 2000 nm shows that W doping gives a transparency of nearly 80% from 380 nm onwards while Mo doping has less transparency of 39% at 380nm. Film hardness measurement using Triboscope shows a film hardness of about 9-10 GPa for both the films. It indicates that W or M doping in tin oxide provides the films the added advantage of withstanding the mechanical wear and tear due to environmental fluctuations By optimizing the optical and electrical properties, W/Mo doped tin oxide films may be explored as window layers in opto-electronic applications such as solar cells.

  15. Deposition, stabilization and characterization of zirconium oxide and hafnium oxide thin films for high k gate dielectrics

    NASA Astrophysics Data System (ADS)

    Gao, Yong

    As the MOS devices continue to scale down in feature size, the gate oxide thickness is approaching the nanometer node. High leakage current densities caused by tunneling is becoming a serious problem. Replacing silicon oxide with a high kappa material as the gate dielectrics is becoming very critical. In recent years, research has been focused on a few promising candidates, such as ZrO2, HfO2, Al2O3, Ta 2O5, and some silicates. However, unary metal oxides tend to crystallize at relatively low temperatures (less than 700°C). Crystallized films usually have a very small grain size and high leakage current due to the grain boundaries. The alternatives are high kappa oxides which are single crystal or amorphous. Silicates remain amorphous at high temperatures, but have some problems such as phase separation, interface reaction, and lower kappa value. In this work, we addressed the crystallization problems of zirconium oxide and hafnium oxide thin films. Both of these two thin films were deposited by DC reactive magnetron sputtering so that very dense films were deposited with little damage. A specially designed system was set up in order to have good control of the deposition process. The crystallization behavior of as-deposited amorphous ZrO2 and HfO2 films was studied. It was found that the films tended to have higher crystallization temperature when the films were thinner than a critical thickness of approximately 5 nm. However, it was still well below 900°C. The crystallization temperature was significantly increased by sandwiching the high kappa oxide layer between two silica layers. Ultra thin HfO2 films of 5nm thickness remained amorphous up to 900°C. This is the highest crystallization temperature which has been reported. The mechanisms for this effect are proposed. Electrical properties of these high kappa dielectric films were also studied. It was found that ultra thin amorphous HfO2 and ZrO 2 films had superior electrical properties to crystalline films

  16. 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.

  17. Formation of Flexible and Transparent Indium Gallium Zinc Oxide/Ag/Indium Gallium Zinc Oxide Multilayer Film

    NASA Astrophysics Data System (ADS)

    Kim, Jun Ho; Kim, Da-Som; Kim, Sun-Kyung; Yoo, Young-Zo; Lee, Jeong Hwan; Kim, Sang-Woo; Seong, Tae-Yeon

    2016-08-01

    In this study, the electrical, optical, and bending characteristics of amorphous indium gallium zinc oxide (IGZO)/Ag/IGZO (39 nm/19 nm/39 nm) multilayer films deposited on polyethylene terephthalate (PET) substrate at room temperature were investigated and compared with those of Sn-doped indium oxide (ITO) (100 nm thick) films. At 500 nm the ITO film transmitted 91.3% and the IGZO/Ag/IGZO multilayer film transmitted 88.8%. The calculated transmittance spectrum of the multilayer film was similar to the experimental result. The ITO film and IGZO/Ag/IGZO multilayer film, respectively, showed carrier concentrations of 1.79 × 1020 and 7.68 × 1021 cm-3 and mobilities of 27.18 cm2/V s and 18.17 cm2/V s. The ITO film had a sheet resistance of 134.9 Ω/sq and the IGZO/Ag/IGZO multilayer film one of 5.09 Ω/sq. Haacke's figure of merit (FOM) was calculated to be 1.94 × 10-3 for the ITO film and 45.02 × 10-3 Ω-1 for the IGZO/Ag/IGZO multilayer film. The resistance change of 100 nm-thick ITO film was unstable even after five cycles, while that of the IGZO/Ag/IGZO film was constant up to 1000 cycles.

  18. Amorphous semiconducting and conducting transparent metal oxide thin films and production thereof

    DOEpatents

    Perkins, John; Van Hest, Marinus Franciscus Antonius Maria; Ginley, David; Taylor, Matthew; Neuman, George A.; Luten, Henry A.; Forgette, Jeffrey A.; Anderson, John S.

    2010-07-13

    Metal oxide thin films and production thereof are disclosed. An exemplary method of producing a metal oxide thin film may comprise introducing at least two metallic elements and oxygen into a process chamber to form a metal oxide. The method may also comprise depositing the metal oxide on a substrate in the process chamber. The method may also comprise simultaneously controlling a ratio of the at least two metallic elements and a stoichiometry of the oxygen during deposition. Exemplary amorphous metal oxide thin films produced according to the methods herein may exhibit highly transparent properties, highly conductive properties, and/or other opto-electronic properties.

  19. Growth of Ordered Ultrathin Tungsten Oxide Films on Pt(111)

    SciTech Connect

    Li, Zhenjun; Zhang, Zhenrong; Kim, Yu Kwon; Smith, R. Scott; Netzer, Falko; Kay, Bruce D.; Rousseau, Roger J.; Dohnalek, Zdenek

    2011-04-07

    Ordered tungsten oxide ultra-thin films were prepared on a Pt(111) substrate at 700 K via direct sublimation of monodispersed cyclic (WO3)3 trimers. The surface composition, structure and morphology were determined using a combination of atomically resolved imaging, ensemble-averaged surface-sensitive spectroscopies, and density functional theory (DFT). We find that half of the (WO3)3 tungsten atoms get partially reduced to the (5+) oxidation state in the first layer at the Pt(111) interface. The opening of the (WO3)3 ring leads to the formation of a tungsten oxide layer with a zig-zag chain structure with a c(4×2) periodicity. In the second layer, the (WO3)3 clusters remain intact and form an ordered (3×3) array of molecularly-bound (WO3)3. DFT calculations provide a detailed understanding of the structure, oxidation states, and the vibrational frequencies for both the c(4×2) and (3×3) overlayers.

  20. Oxidation Effect in Octahedral Hafnium Disulfide Thin Film.

    PubMed

    Chae, Sang Hoon; Jin, Youngjo; Kim, Tae Soo; Chung, Dong Seob; Na, Hyunyeong; Nam, Honggi; Kim, Hyun; Perello, David J; Jeong, Hye Yun; Ly, Thuc Hue; Lee, Young Hee

    2016-01-26

    Atomically smooth van der Waals materials are structurally stable in a monolayer and a few layers but are susceptible to oxygen-rich environments. In particular, recently emerging materials such as black phosphorus and perovskite have revealed stronger environmental sensitivity than other two-dimensional layered materials, often obscuring the interesting intrinsic electronic and optical properties. Unleashing the true potential of these materials requires oxidation-free sample preparation that protects thin flakes from air exposure. Here, we fabricated few-layer hafnium disulfide (HfS2) field effect transistors (FETs) using an integrated vacuum cluster system and study their electronic properties and stability under ambient conditions. By performing all the device fabrication and characterization procedure under an oxygen- and moisture-free environment, we found that few-layer AA-stacking HfS2-FETs display excellent field effect responses (Ion/Ioff ≈ 10(7)) with reduced hysteresis compared to the FETs prepared under ambient conditions. Oxidation of HfS2 occurs uniformly over the entire area, increasing the film thickness by 250% at a prolonged oxidation time of >120 h, while defects on the surface are the preferential initial oxidation sites. We further demonstrated that the stability of the device in air is significantly improved by passivating FETs with BN in a vacuum cluster.

  1. Temperature and pressure dependent Mott potentials and their influence on self-limiting oxide film growth

    NASA Astrophysics Data System (ADS)

    Cai, Na; Zhou, Guangwen; Müller, Kathrin; Starr, David E.

    2012-10-01

    Classic Cabrera-Mott theory stipulates that the limited oxide-film growth results from electron tunneling from the metal through the oxide film to adsorbed oxygen. This leads to an electric field across the oxide film that assists ion migration for low-temperature oxide-film growth. Here, we show that the field-driven oxide-film growth can be manipulated via the temperature and pressure of oxidation. The magnitude of the self-generated electric field depends on the oxygen surface coverage that exhibits a Langmuir isotherm behavior with changes in temperature and oxygen pressure. These observations demonstrate the ability to tune an interfacial reaction via self-adaptation to its environment.

  2. Degradation of electrochromic film of amorphous tungsten oxide after coloration

    NASA Astrophysics Data System (ADS)

    Luo, Zhongkuan

    1992-11-01

    The degradation of the electrochromic film of a-WO3 was investigated from the equilibrium state of different driving voltage and the time dependent emf was also obtained in an open or short circuit of zero volts. Based on the mechanism of activation and the principal of chemical reaction kinetics, the correct definition of electrochromic memory was made and a relation of memory was obtained. It was also found that at the initial time of natural bleaching, the change rate of proton concentration in the film was also obtained. According to the mechanism of electrochromic memory, it was indicated that in the open circuit case, the theoretical reaction of the change rate of electric potential was in good agrement with the experimental results, and furthermore, the reaction constant was determined with the experimental data. In the short circuit case, there exist two effects on degradation, the short circuit current caused by the backward emf, and the oxidation of the colored film. The experimental data shows that, in the short circuit case, the degradation strongly depends on the short circuit current and the effect of chemical reaction can be neglected.

  3. Pulsed laser deposition of nanostructured indium-tin-oxide film

    NASA Astrophysics Data System (ADS)

    Yong, Thian Kok; Nee, Chen Hon; Yap, Seong Shan; Siew, Wee Ong; Sáfran, György; Yap, Yoke Kin; Tou, Teck Yong

    2010-08-01

    Effects of O2, N2, Ar and He on the formation of micro- and nanostructured indium tin oxide (ITO) thin films were investigated in pulsed Nd:YAG laser deposition on glass substrate. For O2 and Ar, ITO resistivity of <= 4 × 10-4 Ωcm and optical transmittance of > 90% were obtained with substrate temperature of 250 °C. For N2 and He, low ITO resisitivity could be obtained but with poor optical transmittance. SEM images show nano-structured ITO thin films for all gases, where dense, larger and highly oriented, microcrystalline structures were obtained for deposition in O2 and He, as revealed from the XRD lines. EDX results indicated the inclusion of Ar and N2 at the expense of reduced tin (Sn) content. When the ITO films were applied for fabrication of organic light emitting devices (OLED), only those deposited in Ar and O2 produced comparable performance to single-layer OLED fabricated on the commercial ITO.

  4. Indium doped zinc oxide nanowire thin films for antireflection and solar absorber coating applications

    SciTech Connect

    Shaik, Ummar Pasha; Krishna, M. Ghanashyam

    2014-04-24

    Indium doped ZnO nanowire thin films were prepared by thermal oxidation of Zn-In metal bilayer films at 500°C. The ZnO:In nanowires are 20-100 nm in diameter and several tens of microns long. X-ray diffraction patterns confirm the formation of oxide and indicate that the films are polycrystalline, both in the as deposited and annealed states. The transmission which is <2% for the as deposited Zn-In films increases to >90% for the ZnO:In nanowire films. Significantly, the reflectance for the as deposited films is < 10% in the region between 200 to 1500 nm and < 2% for the nanowire films. Thus, the as deposited films can be used solar absorber coatings while the nanowire films are useful for antireflection applications. The growth of nanowires by this technique is attractive since it does not involve very high temperatures and the use of catalysts.

  5. Interfacial Shear Strength of Multilayer Graphene Oxide Films.

    PubMed

    Daly, Matthew; Cao, Changhong; Sun, Hao; Sun, Yu; Filleter, Tobin; Singh, Chandra Veer

    2016-02-23

    Graphene oxide (GO) is considered as one of the most promising layered materials with tunable physical properties and applicability in many important engineering applications. In this work, the interfacial behavior of multilayer GO films was directly investigated via GO-to-GO friction force microscopy, and the interfacial shear strength (ISS) was measured to be 5.3 ± 3.2 MPa. Based on high resolution atomic force microscopy images and the available chemical data, targeted molecular dynamics simulations were performed to evaluate the influence of functional structure, topological defects, and interlayer registry on the shear response of the GO films. Theoretical values for shear strength ranging from 17 to 132 MPa were predicted for the different structures studied, providing upper bounds for the ISS. Computational results also revealed the atomic origins of the stochastic nature of friction measurements. Specifically, the wide scatter in experimental measurements was attributed to variations in functional structure and topological defects within the sliding volume. The findings of this study provide important insight for understanding the significant differences in strength between monolayer and bulk graphene oxide materials and can be useful for engineering topological structures with tunable mechanical properties.

  6. 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.

  7. Amperometric detection and electrochemical oxidation of aliphatic amines and ammonia on silver-lead oxide thin-film electrodes

    SciTech Connect

    Ge, Jisheng

    1996-01-08

    This thesis comprises three parts: Electrocatalysis of anodic oxygen-transfer reactions: aliphatic amines at mixed Ag-Pb oxide thin-film electrodes; oxidation of ammonia at anodized Ag-Pb eutectic alloy electrodes; and temperature effects on oxidation of ethylamine, alanine, and aquated ammonia.

  8. 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.

  9. 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.

  10. Superconducting Yttrium Barium Copper Oxide Thin Films and Thin Film Devices

    NASA Astrophysics Data System (ADS)

    Stamper, Anthony Kendall

    Superconducting thin films of YBa_2 Cu_3O_{7 -delta} (YBCO) have been deposited using rf diode sputtering from a single composite target. These films were deposited on silicon substrates at substrate temperatures up to 600^circC using either 100% argon or a 90% argon and 10% oxygen sputtering gas mixture. Yttria-stabilized ZrO_2 (YSZ) buffer layers were employed both for electrical isolation and to minimize the reaction between the silicon and the superconductor. The YSZ crystal structure was highly dependent on the deposition parameters and films with (111) and (100) cubic texturing were grown on oxidized silicon substrates. The composition and electrical properties of the YBCO films, which were deposited on-axis from 5 cm targets, were approximately constant over most of the 5 cm substrates when oxygen was in the sputtering gas and were reproducible. The effect of the sputtering gas pressure, the presence of 10% oxygen in the sputtering gas, the target composition, and the substrate temperature on the film composition have been studied. We demonstrated that neutral oxygen bombardment was responsible for composition differences between the target and the thin film. YBCO films deposited on in-situ heated substrates had zero-transition temperatures up to 87K with 10% to 90% transition widths of less than 5K and were c-axis oriented. Films deposited on unheated substrates required processing at higher temperatures, had zero-transition temperatures up to 85K, and were randomly oriented. Lithographic processes and contact technologies were developed for device fabrication. Using these processes, we fabricated simple YBCO microstrip structures, YBCO/Au/n-Si Schottky diodes, Pb/Ag/YBCO Josephson junctions, and Au/YSZ/YBCO multi-layer structures. After optimization of the process, we were able to fabricate high quality diodes and ohmic contacts without degrading the electrical properties of the YBCO. Finally, we fabricated flux transformer structures, with winding widths

  11. cw laser compaction of aqueous-solution-deposited metal oxide films

    NASA Astrophysics Data System (ADS)

    Exarhos, Gregory J.; Dennis, Tasshi

    1997-05-01

    Zirconium dioxide films were spin cast onto silica or silicon substrates from an aqueous solution comprised of the precursor metal nitrate and an organic complexant such as glycine. The hydrated films so derived consist of an amorphous organic phase in which the metal cations and nitrate anions are homogeneously dispersed. Heating to temperatures above 200 degrees C leads to film dehydration followed by an auto-catalyzed oxidation reaction whereby the bound nitrate oxidizes the organic matrix leaving behind an intact stoichiometric and crystalline metal oxide film. Films are characterized using AFM, XRD, and optical methods. Transformation processes in these films have been studied in detail by means of spectroscopic ellipsometry and laser induced fluorescence from films doped with a suitable rare earth probe ion such as Sm+3. In the latter case, the measured fluorescence emission spectra are used to identify the hydrated, dehydrated, amorphous and crystalline metal oxide phases which evolve during processing. These transformations also have been induced upon visible CW laser irradiation at fluences in excess of 1 MW/cm2. Under these conditions, the film dehydrates and compacts within the footprint of the incident laser beam rendering this region of the film water insoluble. Post irradiation washing of the film with water removes all vestiges of the film outside of the beam footprint suggesting a possible use of this technique for lithography applications. Films subjected to laser irradiation and post irradiation heating have been characterized with respect to thickness, phase composition, crystallite size and optical constants.

  12. Epitaxial growth of intermetallic MnPt films on oxides and large exchange bias

    DOE PAGESBeta

    Liu, Zhiqi; Biegalski, Michael D.; Hsu, Shang-Lin; Shang, Shunli; Marker, Cassie; Liu, Jian; Li, Li; Fan, Lisha S.; Meyer, Tricia L.; Wong, Anthony T.; et al

    2015-11-05

    High-quality epitaxial growth of intermetallic MnPt films on oxides is achieved, with potential for multiferroic heterostructure applications. Antisite-stabilized spin-flipping induces ferromagnetism in MnPt films, although it is robustly antiferromagnetic in bulk. Thus, highly ordered antiferromagnetic MnPt films exhibit superiorly large exchange coupling with a ferromagnetic layer.

  13. Structural and physical properties of tin oxide thin films for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Lin, Su-Shia; Tsai, Yung-Shiang; Bai, Kai-Ren

    2016-09-01

    Tin oxide films were deposited on glass substrates by RF magnetron sputtering. At a lower sputtering pressure, the tin oxide film comprised nanocrystalline orthorhombic SnO with a (110) orientation, greater p-type conductivity and better hydrophobicity. Increasing substrate temperature resulted in the coexistence of nanocrystalline orthorhombic SnO and tetragonal SnO2 in the deposited film, favoring hydrophilicity, changing the p-type conductivity to n-type conductivity, and reducing resistivity. As the sputtering pressure or substrate temperature increased, the tin oxide film exhibited a lower surface roughness, a larger optical energy gap, and higher optical transmission.

  14. Flexible Electronics Powered by Mixed Metal Oxide Thin Film Transistors

    NASA Astrophysics Data System (ADS)

    Marrs, Michael

    A low temperature amorphous oxide thin film transistor (TFT) and amorphous silicon PIN diode backplane technology for large area flexible digital x-ray detectors has been developed to create 7.9-in. diagonal backplanes. The critical steps in the evolution of the backplane process include the qualification and optimization of the low temperature (200 °C) metal oxide TFT and a-Si PIN photodiode process, the stability of the devices under forward and reverse bias stress, the transfer of the process to flexible plastic substrates, and the fabrication and assembly of the flexible detectors. Mixed oxide semiconductor TFTs on flexible plastic substrates suffer from performance and stability issues related to the maximum processing temperature limitation of the polymer. A novel device architecture based upon a dual active layer improves both the performance and stability. Devices are directly fabricated below 200 ºC on a polyethylene naphthalate (PEN) substrate using mixed metal oxides of either zinc indium oxide (ZIO) or indium gallium zinc oxide (IGZO) as the active semiconductor. The dual active layer architecture allows for adjustment to the saturation mobility and threshold voltage stability without the requirement of high temperature annealing, which is not compatible with flexible plastic substrates like PEN. The device performance and stability is strongly dependent upon the composition of the mixed metal oxide; this dependency provides a simple route to improving the threshold voltage stability and drive performance. By switching from a single to a dual active layer, the saturation mobility increases from 1.2 cm2/V-s to 18.0 cm2/V-s, while the rate of the threshold voltage shift decreases by an order of magnitude. This approach could assist in enabling the production of devices on flexible substrates using amorphous oxide semiconductors. Low temperature (200°C) processed amorphous silicon photodiodes were developed successfully by balancing the tradeoffs

  15. Consequences of N2 gas flow variation on properties of zirconium oxide-nitride films

    NASA Astrophysics Data System (ADS)

    Jariwala, Nayan N.; Chauhan, Kamlesh V.; Pandya, Parth P.; Patel, Nicky P.; Rawal, Sushant K.

    2016-09-01

    Zirconium oxide-nitride films was prepared by RF reactive magnetron sputtering in presence of helium, oxygen and nitrogen gases. The N2 gas flow rate was varied for each consecutive run of sputtering at values of 66, 72, 78, 84, and 90 sccm respectively. Zirconium oxide-nitride films showed structural variation in evolution of various textures as detected by X-ray diffraction. It showed good transmission values above 50% for all samples. Wettability studies of zirconium oxide-nitride films was done by contact angle goniometer. All samples depict hydrophobic behaviour as all films have contact angle values above 90° and as nitrogen gas flow rate increases, the films roughness as well as contact angle increases. Tribological test is done on zirconium oxide-nitride films coated on aluminium, brass and mild steel pins, which give excellent wear resistance compared to uncoated pins.

  16. Transparent conductive oxides for thin-film silicon solar cells

    NASA Astrophysics Data System (ADS)

    Löffler, J.

    2005-04-01

    This thesis describes research on thin-film silicon solar cells with focus on the transparent conductive oxide (TCO) for such devices. In addition to the formation of a transparent and electrically conductive front electrode for the solar cell allowing photocurrent collection with low ohmic losses, the front TCO plays an important role for the light enhancement of thin-film silicon pin type solar cells. If the TCO is rough, light scattering at rough interfaces in the solar cell in combination with a highly reflective back contact leads to an increase in optical path length of the light. Multiple (total) internal reflectance leads to virtual 'trapping' of the light in the solar cell structure, allowing a further decrease in absorber thickness and thus thin-film silicon solar cell devices with higher and more stable efficiency. Here, the optical mechanisms involved in the light trapping in thin-film silicon solar cells have been studied, and two types of front TCO materials have been investigated with respect to their suitability as front TCO in thin-film silicon pin type solar cells. Undoped and aluminum doped zinc oxide layers have been fabricated for the first time by the expanding thermal plasma chemical vapour deposition (ETP CVD) technique at substrate temperatures between 150 º C and 350 º C, and successfully implemented as a front electrode material for amorphous silicon pin superstrate type solar cells. Solar cells with efficiencies comparable to cells on Asahi U-type reference TCO have been reproducibly obtained. A higher haze is needed for the ZnO samples studied here than for Asahi U-type TCO in order to achieve comparable long wavelength response of the solar cells. This is attributed to the different angular distribution of the scattered light, showing higher scattering intensities at large angles for the Asahi U-type TCO. A barrier at the TCO/p interface and minor collection problems may explain the slightly lower fill factors obtained for the cells

  17. Growth and Dissolution of Iron and Manganese Oxide Films

    SciTech Connect

    Scot T. Martin

    2008-12-22

    Growth and dissolution of Fe and Mn oxide films are key regulators of the fate and transport of heavy metals in the environment, especially during changing seasonal conditions of pH and dissolved oxygen. The Fe and Mn are present at much higher concentrations than the heavy metals, and, when Fe and Mn precipitate as oxide films, heavy metals surface adsorb or co-precipitate and are thus essentially immobilized. Conversely, when the Fe and Mn oxide films dissolve, the heavy metals are released to aqueous solution and are thus mobilized for transport. Therefore, understanding the dynamics and properties of Fe and Mn oxide films and thus on the uptake and release of heavy metals is critically important to any attempt to develop mechanistic, quantitative models of the fate, transport, and bioavailablity of heavy metals. A primary capability developed in our earlier work was the ability to grow manganese oxide (MnO{sub x}) films on rhodochrosite (MnCO{sub 3}) substrate in presence of dissolved oxygen under mild alkaline conditions. The morphology of the films was characterized using contact-mode atomic force microscopy. The initial growth began by heteroepitaxial nucleation. The resulting films had maximum heights of 1.5 to 2 nm as a result of thermodynamic constraints. Over the three past years, we have investigated the effects of MnO{sub x} growth on the interactions of MnCO{sub 3} with charged ions and microorganisms, as regulated by the surface electrical properties of the mineral. In 2006, we demonstrated that MnO{sub x} growth could induce interfacial repulsion and surface adhesion on the otherwise neutral MnCO{sub 3} substrate under environmental conditions. Using force-volume microscopy (FVM), we measured the interfacial and adhesive forces on a MnO{sub x}/MnCO{sub 3} surface with a negatively charged silicon nitride tip in a 10-mM NaNO3 solution at pH 7.4. The interfacial force and surface adhesion of MnOx were approximately 40 pN and 600 pN, respectively

  18. Photocatalytic degradation of triethylamine on titanium oxide thin films

    SciTech Connect

    Huang, A.; Cao, L.; Chen, J.; Spiess, F.J.; Suib, S.L.; Obee, T.N.; Hay, S.O.; Freihaut, J.D.

    1999-11-15

    Photooxidation of triethylamine (TEA) in the presence of O{sub 2}, N{sub 2}, and H{sub 2}O over titanium oxide (TiO{sub 2}) was investigated using a flat plate reactor. TEA was photocatalytically oxidized to CO{sub 2} and some by-products on TiO{sub 2} thin film catalysts. The intrinsic oxidation rate of the reaction was determined and was dependent on TEA concentration, humidity level, and light intensity. Photocatalytic deactivation was observed in these reactions. Fourier transform infrared (FTIR) and temperature-programmed desorption with a mass spectrometer as a detector (TPD-MS) were used to characterize the surface of the catalyst and study the deactivation mechanism. FTIR and TPD-MS results suggest that accumulation of carboxylic acid species, -N-N=O, and some other accumulation of carboxylic acid species, -N-N=O, and some other carbonaceous species occurred during the reaction. These by-product species or intermediates were chemisorbed on the catalyst surface. They were stable under reaction conditions and might be responsible for deactivation of TiO{sub 2} by either poisoning the active sites directly or blocking the adsorption of TEA on the catalyst surface.

  19. Carboxylate Precursor Effects on MOD Derived Metal Oxide (Nickel/Nickel Oxide ) Thin Films

    NASA Astrophysics Data System (ADS)

    Gao, Xiang

    Thin films in the (Ni/NiO) system have been widely studied because of their significant potential for use in batteries, fuel cells, solar cells, supercapacitors, magnetic devices and various sensor applications. Such films typically are deposited onto suitable substrates by electrochemical or vapor deposition methods, followed by heat treatment to develop the oxide structure. In this study, by contrast, the Ni/NiO thin films were prepared by metallo-organic decomposition (MOD) technique in order to facilitate the development of nano structure feature as well as molecular scale mixing and excellent composition control. Critical parameters that must be controlled during this deposition process to achieve high quality films include: carboxylate precursor chemistry, solution chemistry, film structure chemistry, film deposition characteristics, film structure development and pyrolysis characteristics. These crucial control parameters are, for the most areas, poorly understood for this system especially for the carboxylate precursor chemistry effects on properties of Ni/NiO thin films. The goal of this work, therefore, is to understand and design those parameters in term of precursor species, viscosity, solute concentration and solvent composition as well as film deposition and heat treatment conditions that can lead to the controlled fabrication of nano-sized, high surface area, low resistive Ni/NiO thin films on Si and metallic substrates such as stainless steels and silver. The solvent system used consisted of a unique mixture of propionic acid and amylamine, in molar ratio of 0.5--2.0, with Ni acetate as the solute precursor in the concentration range of 0.2--2 mol/l. The films were prepared by spin deposition at 3000 rpm from carboxylate solution precursors with viscosity range of 10--640 cP. Good quality nano-sized Ni/NiO thin films, in the range of 0.2--2 microm thickness, on Si or stainless steel substrates were obtained by a mixed AA/PPA solvent system in the

  20. Fabrication of Fe-Al nanoparticles by selective oxidation of Fe-Al thin films

    NASA Astrophysics Data System (ADS)

    Jang, Pyungwoo; Shin, Seungchan; Jung, Chip-Sup; Kim, Kwang-Ho; Seomoon, Kyu

    2013-04-01

    The possibility of a new technique for fabricating nanoparticles from thin films using selective oxidation in an atmosphere mixture of water vapor and hydrogen was investigated. Fe-5wt.%Al films were RF-sputtered and annealed in the atmosphere mixture at 900°C for up to 200 min, in order to oxidize aluminum selectively. Thermodynamics simulation showed that temperatures exceeding 800°C are necessary to prevent iron from being oxidized, as confirmed by the depth profile of XPS. As the annealing time increased, the morphology of the 200-nm Fe-Al films changed from the continuous to the discontinuous type; thus, particulate Fe-Al films formed after 100 min. The particulate 10- to 100-nm Fe-Al films showed super-paramagnetic behavior after the oxidation. Thus, a new technique for fabricating nanoparticles was successfully introduced using selective oxidation.

  1. Electrochromic properties of niobium oxide thin films prepared by radio-frequency magnetron sputtering method

    NASA Astrophysics Data System (ADS)

    Maruyama, Toshiro; Arai, Susumu

    1993-08-01

    Electrochromic niobium oxide thin films were prepared by a radio-frequency magnetron sputtering method. Amorphous Nb2O5 thin films deposited at radio-frequency power 100 W showed the electrochromic behavior: Reduction and oxidation of the films in 0.1 M Na2CO3+0.1 M NaHCO3 buffer solution resulted in coloration and bleaching, respectively. Coulometry indicated that the coloration efficiency was 10 cm2/C.

  2. Measurements of the optical properties of thin films of silver and silver oxide

    NASA Technical Reports Server (NTRS)

    Peters, Palmer N.; Sisk, Robert C.; Brown, Yolanda; Gregory, John C.; Nag, Pallob K.; Christl, Ligia

    1995-01-01

    The optical properties of silver films and their oxides are measured to better characterize such films for use as sensors for atomic oxygen. Good agreement between properties of measured pure silver films and reported optical constants is observed. Similar comparisons for silver oxide have not been possible because of a lack of reported constants, but self-consistencies and discrepancies in our measured results are described.

  3. On the Design of Oxide Films, Nanomaterials, and Heterostructures for Solar Water Oxidation Photoanodes

    NASA Astrophysics Data System (ADS)

    Kronawitter, Coleman Xaver

    Photoelectrochemistry and its associated technologies show unique potential to facilitate the large-scale production of solar fuels—those energy-rich chemicals obtained through conversion processes driven by solar energy, mimicking the photosynthetic process of green plants. The critical component of photoelectrochemical devices designed for this purpose is the semiconductor photoelectrode, which must be optically absorptive, chemically stable, and possess the required electronic band alignment with respect to the redox couple of the electrolyte to drive the relevant electrochemical reactions. After many decades of investigation, the primary technological obstacle remains the development of photoelectrode structures capable of efficient and stable conversion of light with visible frequencies, which is abundant in the solar spectrum. Metal oxides represent one of the few material classes that can be made photoactive and remain stable to perform the required functions. The unique range of functional properties of oxides, and especially the oxides of transition metals, relates to their associated diversity of cation oxidation states, cation electronic configurations, and crystal structures. In this dissertation, the use of metal oxide films, nanomaterials, and heterostructures in photoelectrodes enabling the solar-driven oxidation of water and generation of hydrogen fuel is examined. A range of transition- and post-transition-metal oxide material systems and nanoscale architectures is presented. The first chapters present results related to electrodes based on alpha-phase iron(III) oxide, a promising visible-light-active material widely investigated for this application. Studies of porous films fabricated by physical vapor deposition reveal the importance of structural quality, as determined by the deposition substrate temperature, on photoelectrochemical performance. Heterostructures with nanoscale feature dimensionality are explored and reviewed in a later chapter

  4. ZnO Films with Very High Haze Value for Use as Front Transparent Conductive Oxide Films in Thin-Film Silicon Solar Cells

    NASA Astrophysics Data System (ADS)

    Hongsingthong, Aswin; Krajangsang, Taweewat; Afdi Yunaz, Ihsanul; Miyajima, Shinsuke; Konagai, Makoto

    2010-05-01

    We successfully increased the haze value of zinc oxide (ZnO) films fabricated using metal-organic chemical vapor deposition (MOCVD) by conducting glass-substrate etching before film deposition. It was found that with increasing the glass treatment time, the surface morphology of ZnO films changed from conventional pyramid-like single texture to greater cauliflower-like multi texture. Further, the rms roughness and the haze value of the films increased remarkably. Using ZnO films with a high haze value as front transparent conductive oxide (TCO) films in hydrogenated microcrystalline silicon (µc-Si:H) solar cells, we improved the quantum efficiency of these cells particularly in the long-wavelength region.

  5. Aqueous phase deposition of dense tin oxide films with nano-structured surfaces

    SciTech Connect

    Masuda, Yoshitake Ohji, Tatsuki; Kato, Kazumi

    2014-06-01

    Dense tin oxide films were successfully fabricated in an aqueous solution. The pH of the solutions was controlled to pH 1.3 by addition of HCl. Precise control of solution condition and crystal growth allowed us to obtain dense tin oxide films. Concave–convex surface of fluorine-doped tin oxide (FTO) substrates was entirely-covered with the continuous films. The films were about 65 nm in thickness and had nano-structured surfaces. Morphology of the films was strikingly different from our previous reported nano-sheet assembled structures. The films were not removed from the substrates by strong water flow or air blow to show strong adhesion strength. The aqueous solution process can be applied to surface coating of various materials such as nano/micro-structured surfaces, particles, fibers, polymers, metals or biomaterials. - Graphical abstract: Dense tin oxide films of 65 nm were successfully fabricated in an aqueous solution. They had nano-structured surfaces. Concave-convex substrates were entirely-covered with the continuous films. - Highlights: • Dense tin oxide films of 65 nm were successfully fabricated in an aqueous solution. • They had nano-structured surfaces. • Concave–convex substrates were entirely-covered with the continuous films.

  6. Metal oxide semiconductor thin-film transistors for flexible electronics

    NASA Astrophysics Data System (ADS)

    Petti, Luisa; Münzenrieder, Niko; Vogt, Christian; Faber, Hendrik; Büthe, Lars; Cantarella, Giuseppe; Bottacchi, Francesca; Anthopoulos, Thomas D.; Tröster, Gerhard

    2016-06-01

    The field of flexible electronics has rapidly expanded over the last decades, pioneering novel applications, such as wearable and textile integrated devices, seamless and embedded patch-like systems, soft electronic skins, as well as imperceptible and transient implants. The possibility to revolutionize our daily life with such disruptive appliances has fueled the quest for electronic devices which yield good electrical and mechanical performance and are at the same time light-weight, transparent, conformable, stretchable, and even biodegradable. Flexible metal oxide semiconductor thin-film transistors (TFTs) can fulfill all these requirements and are therefore considered the most promising technology for tomorrow's electronics. This review reflects the establishment of flexible metal oxide semiconductor TFTs, from the development of single devices, large-area circuits, up to entirely integrated systems. First, an introduction on metal oxide semiconductor TFTs is given, where the history of the field is revisited, the TFT configurations and operating principles are presented, and the main issues and technological challenges faced in the area are analyzed. Then, the recent advances achieved for flexible n-type metal oxide semiconductor TFTs manufactured by physical vapor deposition methods and solution-processing techniques are summarized. In particular, the ability of flexible metal oxide semiconductor TFTs to combine low temperature fabrication, high carrier mobility, large frequency operation, extreme mechanical bendability, together with transparency, conformability, stretchability, and water dissolubility is shown. Afterward, a detailed analysis of the most promising metal oxide semiconducting materials developed to realize the state-of-the-art flexible p-type TFTs is given. Next, the recent progresses obtained for flexible metal oxide semiconductor-based electronic circuits, realized with both unipolar and complementary technology, are reported. In particular

  7. 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.

  8. Graphene-based thin film supercapacitor with graphene oxide as dielectric spacer

    NASA Astrophysics Data System (ADS)

    Liu, Jinzhang; Galpaya, Dilini; Notarianni, Marco; Yan, Cheng; Motta, Nunzio

    2013-08-01

    Thin film supercapacitors are produced by using electrochemically exfoliated graphene (G) and wet-chemically produced graphene oxide (GO). Either G/GO/G stacked film or sole GO film are sandwiched by two Au films to make devices, where GO is the dielectric spacer. The addition of graphene film can increase the capacitance about two times, compared to the simple Au electrode. It is found that the GO film has very high dielectric constant, accounting for the high capacitance. AC measurement reveals that the relative permittivity of GO is in the order of 104 within the frequency range of 0.1-70 Hz.

  9. Fabrication and characterization of oxide-based thin film transistors, and process development for oxide heterostructures

    NASA Astrophysics Data System (ADS)

    Lim, Wantae

    2009-12-01

    This dissertation is focused on the development of thin film transistors (TFTs) using oxide materials composed of post-transitional cations with (n-1)d 10ns0 (n≥4). The goal is to achieve high performance oxide-based TFTs fabricated at low processing temperature on either glass or flexible substrates for next generation display applications. In addition, etching mechanism and Ohmic contact formation for oxide heterostructure (ZnO/CuCrO 2) system is demonstrated. The deposition and characterization of oxide semiconductors (In 2O3-ZnO, and InGaZnO4) using a RF-magnetron sputtering system are studied. The main influence on the resistivity of the films is found to be the oxygen partial pressure in the sputtering ambient. The films remained amorphous and transparent (> 70%) at all process conditions. These films showed good transmittance at suitable conductivity for transistor fabrication. The electrical characteristics of both top- and bottom-gate type Indium Zinc Oxide (InZnO) and Indium Gallium Zinc Oxide (InGaZnO4)-based TFTs are reported. The InZnO films were favorable for depletion-mode TFTs due to their tendency to form oxygen vacancies, while enhancement-mode devices were realized with InGaZnO4 films. The InGaZnO4-based TFTs fabricated on either glass or plastic substrates at low temperature (<100°C) exhibit good electrical properties: the saturation mobility of 5--12 cm2.V-1.s-1 and threshold voltage of 0.5--2.5V. The devices are also examined as a function of aging time in order to verify long-term stability in air. The effect of gate dielectric materials on electrical properties of InGaZnO 4-based TFTs was investigated. The use of SiNx film as a gate dielectric reduces the trap density and the roughness at the channel/gate dielectric interface compared to SiO2 gate dielectric, resulting in an improvement of device parameters by reducing scattering of trapped charges at the interface. The quality of interface is shown to have large effect on TFT performance

  10. Origin and Tunability of Unusually Large Surface Capacitance in Doped Cerium Oxide Studied by Ambient-Pressure X-Ray Photoelectron Spectroscopy.

    PubMed

    Gopal, Chirranjeevi Balaji; Gabaly, Farid El; McDaniel, Anthony H; Chueh, William C

    2016-06-01

    The volumetric redox (chemical) capacitance of the surface of CeO2-δ films is quantified in situ to be 100-fold larger than the bulk values under catalytically relevant conditions. Sm addition slightly lowers the surface oxygen nonstoichiometry, but effects a 10-fold enhancement in surface chemical capacitance by mitigating defect interactions, highlighting the importance of differential nonstoichiometry for catalysis. PMID:27031580

  11. Deformation behavior of the oxide film on the surface of cold sprayed powder particle

    NASA Astrophysics Data System (ADS)

    Yin, Shuo; Wang, Xiaofang; Li, Wenya; Liao, Hanlin; Jie, Hongen

    2012-10-01

    In cold spraying, oxide-free interface is an important factor for metal-to-metal contact between powder particles and substrate, which determines the bonding strength and final coating quality. In this study, a systematic finite element analysis (FEA) is performed to examine the deformation behavior of the oxide film on an Al 6061-T6 particle surface after deposition. The simulation results show that the oxide film can be disrupted during the high velocity impact. Part of the cracked oxides remains at the interface and mainly accumulates at the central region after particle deposition. Substrate hardness, particle velocity and spray angle are found to influence the deformation behavior and final state of the oxide film. Besides, interparticle interaction is also investigated in the present work to clarify the deformation behavior of the oxide film inside the coating.

  12. Continuously Controlled Optical Band Gap in Oxide Semiconductor Thin Films.

    PubMed

    Herklotz, Andreas; Rus, Stefania Florina; Ward, Thomas Zac

    2016-03-01

    The optical band gap of the prototypical semiconducting oxide SnO2 is shown to be continuously controlled through single axis lattice expansion of nanometric films induced by low-energy helium implantation. While traditional epitaxy-induced strain results in Poisson driven multidirectional lattice changes shown to only allow discrete increases in bandgap, we find that a downward shift in the band gap can be linearly dictated as a function of out-of-plane lattice expansion. Our experimental observations closely match density functional theory that demonstrates that uniaxial strain provides a fundamentally different effect on the band structure than traditional epitaxy-induced multiaxes strain effects. Charge density calculations further support these findings and provide evidence that uniaxial strain can be used to drive orbital hybridization inaccessible with traditional strain engineering techniques. PMID:26836282

  13. Continuously controlled optical band gap in oxide semiconductor thin films

    DOE PAGESBeta

    Herklotz, Andreas; Rus, Stefania Florina; Ward, Thomas Zac

    2016-02-02

    The optical band gap of the prototypical semiconducting oxide SnO2 is shown to be continuously controlled through single axis lattice expansion of nanometric films induced by low-energy helium implantation. While traditional epitaxy-induced strain results in Poisson driven multidirectional lattice changes shown to only allow discrete increases in bandgap, we find that a downward shift in the band gap can be linearly dictated as a function of out-of-plane lattice expansion. Our experimental observations closely match density functional theory that demonstrates that uniaxial strain provides a fundamentally different effect on the band structure than traditional epitaxy-induced multiaxes strain effects. In conclusion, chargemore » density calculations further support these findings and provide evidence that uniaxial strain can be used to drive orbital hybridization inaccessible with traditional strain engineering techniques.« less

  14. 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}

  15. Electrophoretic deposition of PTFE particles on porous anodic aluminum oxide film and its tribological properties

    NASA Astrophysics Data System (ADS)

    Zhang, Dongya; Dong, Guangneng; Chen, Yinjuan; Zeng, Qunfeng

    2014-01-01

    Polytetrafluoroethylene (PTFE) composite film was successfully fabricated by depositing PTFE particles into porous anodic aluminum oxide film using electrophoretic deposition (EPD) process. Firstly, porous anodic aluminum oxide film was synthesized by anodic oxidation process in sulphuric acid electrolyte. Then, PTFE particles in suspension were directionally deposited into the porous substrate. Finally, a heat treatment at 300 °C for 1 h was utilized to enhance PTFE particles adhesion to the substrate. The influence of anodic oxidation parameters on the morphology and micro-hardness of the porous anodic aluminum oxide film was studied and the PTFE particles deposited into the pores were authenticated using energy-dispersive spectrometer (EDS) and scanning electron microscopy (SEM). Tribological properties of the PTFE composite film were investigated under dry sliding. The experimental results showed that the composite film exhibit remarkable low friction. The composite film had friction coefficient of 0.20 which deposited in 15% PTFE emulsion at temperature of 15 °C and current density of 3 A/dm2 for 35 min. In addition, a control specimen of porous anodic aluminum oxide film and the PTFE composite film were carried out under the same test condition, friction coefficient of the PTFE composite film was reduced by 60% comparing with the control specimen at 380 MPa and 100 mm/s. The lubricating mechanism was that PTFE particles embedded in porous anodic aluminum oxide film smeared a transfer film on the sliding path and the micro-pores could support the supplement of solid lubricant during the sliding, which prolonged the lubrication life of the aluminum alloys.

  16. Electrically Controlled Drug Delivery from Graphene Oxide Nanocomposite Films

    PubMed Central

    2015-01-01

    On-demand, local delivery of drug molecules to target tissues provides a means for effective drug dosing while reducing the adverse effects of systemic drug delivery. This work explores an electrically controlled drug delivery nanocomposite composed of graphene oxide (GO) deposited inside a conducting polymer scaffold. The nanocomposite is loaded with an anti-inflammatory molecule, dexamethasone, and exhibits favorable electrical properties. In response to voltage stimulation, the nanocomposite releases drug with a linear release profile and a dosage that can be adjusted by altering the magnitude of stimulation. No drug passively diffuses from the composite in the absence of stimulation. In vitro cell culture experiments demonstrate that the released drug retains its bioactivity and that no toxic byproducts leach from the film during electrical stimulation. Decreasing the size and thickness of the GO nanosheets, by means of ultrasonication treatment prior to deposition into the nanocomposite, alters the film morphology, drug load, and release profile, creating an opportunity to fine-tune the properties of the drug delivery system to meet a variety of therapeutic needs. The high level of temporal control and dosage flexibility provided by the electrically controlled GO nanocomposite drug delivery platform make it an exciting candidate for on-demand drug delivery. PMID:24428340

  17. Combustion synthesized indium-tin-oxide (ITO) thin film for source/drain electrodes in all solution-processed oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Tue, Phan Trong; Inoue, Satoshi; Takamura, Yuzuru; Shimoda, Tatsuya

    2016-06-01

    We report combustion solution synthesized (SCS) indium-tin-oxide (ITO) thin film, which is a well-known transparent conductive oxide, for source/drain (S/D) electrodes in solution-processed amorphous zirconium-indium-zinc-oxide TFT. A redox-based combustion synthetic approach is applied to ITO thin film using acetylacetone as a fuel and metal nitrate as oxidizer. The structural and electrical properties of SCS-ITO precursor solution and thin films were systematically investigated with changes in tin concentration, indium metal precursors, and annealing conditions such as temperature, time, and ambient. It was found that at optimal conditions the SCS-ITO thin film exhibited high crystalline quality, atomically smooth surface (RMS ~ 4.1 Å), and low electrical resistivity (4.2 × 10-4 Ω cm). The TFT using SCS-ITO film as the S/D electrodes showed excellent electrical properties with negligible hysteresis. The obtained "on/off" current ratio, subthreshold swing factor, subthreshold voltage, and field-effect mobility were 5 × 107, 0.43 V/decade, 0.7 V, and 2.1 cm2/V s, respectively. The performance and stability of the SCS-ITO TFT are comparable to those of the sputtered-ITO TFT, emphasizing that the SCS-ITO film is a promising candidate for totally solution-processed oxide TFTs.

  18. High dielectric constant nickel-doped titanium oxide films prepared by liquid-phase deposition

    NASA Astrophysics Data System (ADS)

    Lee, Ming-Kwei; Yen, Chih-Feng; Fan, Cho-Han

    2014-09-01

    The electrical characteristics of nickel-doped titanium oxide films prepared by liquid-phase deposition on p-type (100) silicon substrate were investigated. The aqueous solutions of ammonium hexafluorotitanate and boric acid were used as precursors for the growth of titanium oxide films and the dielectric constant is 29. The dielectric constant can be improved to 94 by nickel doping at the thermal annealing at 700 °C in nitrous oxide.

  19. Nickel oxide and molybdenum oxide thin films for infrared imaging prepared by biased target ion-beam deposition

    NASA Astrophysics Data System (ADS)

    Jin, Yao; Saint John, David; Jackson, Tom N.; Horn, Mark W.

    2014-06-01

    Vanadium oxide (VOx) thin films have been intensively used as sensing materials for microbolometers. VOx thin films have good bolometric properties such as low resistivity, high negative temperature coefficient of resistivity (TCR) and low 1/f noise. However, the processing controllability of VOx fabrication is difficult due to the multiple valence states of vanadium. In this study, metal oxides such as nickel oxide (NiOx) and molybdenum oxide (MoOx) thin films have been investigated as possible new microbolometer sensing materials with improved process controllability. Nickel oxide and molybdenum oxide thin films were prepared by reactive sputtering of nickel and molybdenum metal targets in a biased target ion beam deposition tool. In this deposition system, the Ar+ ion energy (typically lower than 25 eV) and the target bias voltage can be independently controlled since ions are remotely generated. A residual gas analyzer (RGA) is used to precisely control the oxygen partial pressure. A real-time spectroscopic ellipsometry is used to monitor the evolution of microstructure and properties of deposited oxides during growth and post-deposition. The properties of deposited oxide thin films depend on processing parameters. The resistivity of the NiOx thin films is in the range of 0.5 to approximately 100 ohm-cm with a TCR from -2%/K to -3.3%/K, where the resistivity of MoOx is between 3 and 2000 ohm-cm with TCR from -2.1%/K to -3.2%/K. We also report on the thermal stability of these deposited oxide thin films.

  20. Cerium as a surrogate in the plutonium immobilization waste form

    NASA Astrophysics Data System (ADS)

    Marra, James Christopher

    In the aftermath of the Cold War, approximately 50 tonnes (MT) of weapons useable plutonium (Pu) has been identified as excess. The U.S. Department of Energy (DOE) has decided that at least a portion of this material will be immobilized in a titanate-based ceramic for final disposal in a geologic repository. The baseline formulation was designed to produce a ceramic consisting primarily of a highly substituted pyrochlore with minor amounts of brannerite and hafnia-substituted rutile. Since development studies with actual actinide materials is difficult, surrogates have been used to facilitate testing. Cerium has routinely been used as an actinide surrogate in actinide chemistry and processing studies. Although cerium appeared as an adequate physical surrogate for powder handling and general processing studies, cerium was found to act significantly different from a chemical perspective in the Pu ceramic form. The reduction of cerium at elevated temperatures caused different reaction paths toward densification of the respective forms resulting in different phase assemblages and microstructural features. Single-phase fabrication studies and cerium oxidation state analyses were performed to further quantify these behavioral differences. These studies indicated that the major phases in the final phase assemblages contained point defects likely leading to their stability. Additionally, thermochemical arguments predicted that the predominant pyrochlore phase in the ceramic was metastable. The apparent metastabilty associated with primary phase in the Pu ceramic form indicated that additional studies must be performed to evaluate the thermodynamic properties of these compounds. Moreover, the metastability of this predominant phase must be considered in assessment of long-term behavior (e.g. radiation stability) of this ceramic.