Phase composition,conductivity,and sensor properties of cerium-doped indium oxide

The hydrothermal synthesis of In_(2)O_(3)and CeO_(2)–In_(2)O_(3)is investigated as well as the properties of sensor layers based on these compounds.During the synthesis of In_(2)O_(3),intermediate products In(OH)_(3)and InOOH are formed,which are the precursors of stable cubic(c-In_(2)O_(3))and metastable rhombohedral(rh-In_(2)O_(3))phases,respectively.A transition from c-In_(2)O_(3)to rh-In_(2)O_(3)is observed with the addition of CeO_(2).The introduction of cerium into rh-In_(2)O_(3)results in a decrease in the sensor response to hydrogen,while it increases in composites based on c-In_(2)O_(3).The data on the sensor activity of the composites correlate with XPS results in which CeO_(2)causes a decrease in the concentrations of chemisorbed oxygen and oxygen vacancies in rh-In_(2)O_(3).The reverse situation is observed in composites based on c-In_(2)O_(3).Compared to In_(2)O_(3)and CeO_(2)–In_(2)O_(3)obtained by other methods,the synthesized composites demonstrate maximum response to H_(2)at low temperatures by 70–100℃,and have short response time(0.2–0.5 s),short recovery time(6–7 s),and long-term stability.A model is proposed for the dependence of sensitivity on the direction of electron transfer between In_(2)O_(3)and CeO_(2).

Three-dimensional numerical simulation of heating and melting behaviors of cerium oxide powders in radio frequency thermal plasma

The present study aims at the numerical simulations of the melting process of cerium oxide particles in RF thermal plasma.The physical model and the calculating method were described firstly;the interaction between cerium oxide particles and plasma was analyzed;specific attention was given to the effects of particle initial size,injection velocity on the particle melting and trajectory in plasma.The influence of the temperature field and velocity field distribution of the plasma around the particle trajectory on the melting effect is analyzed,and the relationship between the heat absorption efficiency of the particles and the particle size reduction process is further determined.It is also found that there exists an optimal particle initial injection velocity which led to a more concentrated final particle size distribution and a more significant reduction of particle size.The results could provide effective guidance for understanding the plasma spheroidization process of uranium dioxide and cerium dioxide powder particles.

Nano transdermal system combining mitochondria-targeting cerium oxide nanoparticles with all-trans retinoic acid for psoriasis

Psoriasis is an inflammatory skin disease that is intricately linked to oxidative stress.Antioxidation and inhibition of abnormal proliferation of keratinocytes are pivotal strategies for psoriasis.Delivering drugs with these effects to the site of skin lesions is a challenge that needs to be solved.Herein,we reported a nanotransdermal delivery system composed of all-trans retinoic acid(TRA),triphenylphosphine(TPP)-modified cerium oxide(CeO2)nanoparticles,flexible nanoliposomes and gels(TCeO_(2)-TRA-FNL-Gel).The results revealed that TCeO_(2)synthesized by the anti-micelle method,with a size of approximately 5 nm,possessed excellent mitochondrial targeting ability and valence conversion capability related to scavenging reactive oxygen species(ROS).TCeO_(2)-TRA-FNL prepared by the film dispersion method,with a size of approximately 70 nm,showed high drug encapsulation efficiency(>96%).TCeO_(2)-TRA-FNL-Gel further showed sustained drug release behaviors,great transdermal permeation ability,and greater skin retention than the free TRA.The results of in vitro EGF-induced and H2O2-induced models suggested that TCeO_(2)-TRA-FNL effectively reduced the level of inflammation and alleviated oxidative stress in HaCat cells.The results of in vivo imiquimod(IMQ)-induced model indicated that TCeO_(2)-TRA-FNL-Gel could greatly alleviate the psoriasis symptoms.In summary,the transdermal drug delivery system designed in this study has shown excellent therapeutic effects on psoriasis and is prospective for the safe and accurate therapy of psoriasis.

Cerium Oxide Nanoparticles Protect against Oxaliplatin Induced Testicular Damage: Biochemical, Histological, Immunohistochemical, and Genotoxic Study

Oxaliplatin is a chemotherapeutic drug used for colorectal cancer treatment. The testicular toxic effect is one of its recorded toxicities which resulted in a few studies. Oxidative stress could be a direct cause of this testicular toxicity. Cerium oxide nanoparticles (CONPs) are optimistic antioxidants for applications in medicine. The aim of the work is to study the protective effect of CONPs on testicular toxicity induced by oxaliplatin in rats. Forty adult male albino rats were divided into 4 groups: Control group, CONPs group (60 mg/kg, 5 times/week), Oxaliplatin group (4 mg/kg, twice/week), and Oxaliplatin & CONPs group, for 4 weeks. Seventy-two hours after the last administration, blood samples were taken for hormonal levels and testes were used for both histopathology and immunohistochemical microscopic examination. Sperm smears were also performed and their results were statistically analyzed to detect any sperm abnormalities. Oxaliplatin increased MDA levels. SOD and GPx activity was decreased. GSH levels were decreased. Also, it decreased the sperm cell count and serum testosterone, and anti-Müllerian hormon. In the testicular sections, significant histopathology changes were seen and immunohistochemical examination confirmed these results. Upon supplementation of CONPs with oxaliplatin decreased MDA levels. SOD and GPx activity was increased, and GSH did not change. In testicular sections, normal morphology was seen. Also, there was an increase in the sperm cell count and serum testosterone anti-Müllerian with significant improvement of testicular architecture, and immunohistochemical examination confirmed these results. The utilization of CONPs produced significant protection against all of the above-mentioned changes.

Neuroprotective Potential of Cerium Oxide Nanoparticles for Focal Cerebral Ischemic Stroke

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

An overview on recent in vivo biological application of cerium oxide nanoparticles

Cerium oxide nanoparticles(CNPs)possess a great potential as therapeutic agents due to their ability to self-regenerate by reversibly switching between two valences+3 and+4.This article reviews recent articles dealing with in vivo studies of CNPs towards Alzheimer’s disease,obesity,liver inflammation,cancer,sepsis,amyotrophic lateral sclerosis,acute kidney injury,radiation-induced tissue damage,hepatic ischemia reperfusion injury,retinal diseases and constipation.In vivo anti-cancer studies revealed the effectiveness of CNPs to reduce tumor growth and angiogenesis in melanoma,ovarian,breast and retinoblastoma cancer cell-induced mice,with their conjugation with folic acid,doxorubicin,CPM,or CXC receptor-4 antagonist ligand eliciting higher efficiency.After conjugation with triphenylphosphonium or magnetite nanoparticles,CNPs were shown to combat Alzheimer’s disease by reducing amyloid-β,glial fibrillary acidic protein,inflammatory and oxidative stress markers in mice.By improving muscle function and longevity,the citrate/EDTA-stabilized CNPs could ameliorate amyotrophic lateral sclerosis.Also,they could effectively reduce obesity in mice by scavenging ROS and reducing adipogenesis,triglyceride synthesis,GAPDH enzyme activity,leptin and insulin levels.In CCl4-induced rats,stress signaling pathways due to inflammatory cytokines,liver enzymes,oxidative and endoplasmic reticulum messengers could be attenuated by CNPs.Commercial CNPs showed protective effects on rats with hepatic ischemia reperfusion and peritonitis-induced hepatic/cardiac injuries by decreasing oxidative stress and hepatic/cardiac inflammation.The same CNPs could improve kidney function by diminishing renal superoxide,hyperglycemia and tubular damage in peritonitis-induced acute kidney injury in rats.Radiation-induced lung and testicular tissue damage could be alleviated in mice,with the former showing improvement in pulmonary distress and bronchoconstriction and the latter exhibiting restoration in spermatogenesis rate and spermatid/spermatocyte number.Through enhancement of gastrointestinal motility,the CNPs could alleviate constipation in both young and old rats.They could also protect rat from light-induced retinal damage by slowing down neurodegenerative process and microglial activation.

Methane Oxidative Coupling over Fluoride-Promoted Cerium Oxide Catalysts

Since the pioneer work of Keller and Bhasin on the oxidative coupling of methane, many catalyst systems, mostly based on the oxides or complex oxides of alkali metals, alkali earth metals and rare earth metals, have been developed. In some studies, halides, especially chlorides and bromides, have been added to these oxides in order to improve the catalvtic activitv and selectivity. howevek of

11B NMR Spectroscopy of Lead Borate Glasses: Additive Effect of Cerium Oxide

Glasses and glass ceramics in the system xCeO2·(50 - x)PbO·50B2O3 (0 ≤ x ≤ 50) have been studied, for the first time, by NMR and FTIR techniques. Effect of CeO2 substitution with PbO on NMR parameters has been discussed in terms of changing both boron and cerium coordination. The quantitative fraction of four coordinated boron (N4) has been simply determined from 11B NMR spectroscopy. On the other hand, the fraction of total tetrahedral structural units B4 (BO4 + PbO4 + CeO4) is obtained from FTIR spectral analysis. It is not possible to get the fraction of cerium oxide directly from the applied spectroscopic tools. Therefore, a simple approach is applied, for the first time, to determine CeO4 fraction by using the different criteria of both 11B NMR and FTIR spectroscopy. The fraction of B4 species is equal to N4, within the experimental error, of the same glasses in the composition region of up to 10 mol% CeO2. On the other hand, there is a clear difference between both N4 and B4 values in glasses of higher CeO2 content (>10 mol%). The related difference showed a linear increasing trend with increasing the content of CeO2 in the glass. This was discussed on the bases of structural role of CeO2 which acts as a glass former in the region >10 mol%, while, at lower concentration, it consumed as a glass modifier.

Conductivity of cerium oxides doped by trivalent cations

For the doping technique with single dopant of Sb2O3,Ga2O3,In2O3,AlCl3,Bi2O3 or Sm2O3,the dopant concentrations of 10%(molar fraction) were selected for the CeO2-based oxygen-ion conductors. A wet chemical method by polymerization of polyvinyl-alcohol was performed for the compound preparation. X-ray diffraction analysis result shows that the calcined powders have nanocrystalline structure with grain size less than 40 nm,and the sintered samples have pure single fluorite-type phase in all doped cerium oxides. Impedance measurement results show that the conductivities and activation energies of CeO2-based oxides depend closely on the dopants. The Sb2O3-doped CeO2 has the largest conductivity and In2O3-doped CeO2 has the lowest one at 200 ℃,the Bi2O3-doped oxide shows the highest activation energy and Al2O3-doped oxide shows the lowest one. Ionic radii and association enthalpies of dopants were taken account for different conductivities and activation energies of the CeO2-based oxygen-ion conductors.

Direct fabrication of cerium oxide hollow nanofibers by electrospinning

Electrospinning technique was used to fabricate PVP/Ce（NO3）3 composite microfibers. Different morphological CeO2 nanofibers were obtained by calcination of the PVP/Ce（NO3）3 composite microfibers and were characterized by scanning electron microscopy （SEM）, Transmission electron microscopy （TEM）, X-ray diffraction （XRD）, thermal gravimetric and differential thermal analysis （TG-DTA）, and （FTIR）. SEM micrographs indicated that the surface of the composite fibers was smooth and became coarse with the increase of calcination temperatures. The diameters of CeO2 hollow nanofibers （300 nm at 600 ℃ and 600 nm at 800 ℃ ） were smaller than those of PVP/Ce（NO3）3 composite fibers （1-2 um ）. CeO2 hollow nanofibers were obtained at 600 ℃ and CeO2 hollow and porous nanofibers formed by nanoparti- cles were obtained at 800 ℃. The length of the CeO2 hollow nanofibers was greater than 50 um. XRD analysis revealed that the composite microfibers were amorphous in structure and CeO2 nanofibers were cubic in structure with space group O^5H - FM3m when calcination tem- peratures were 600-800 ℃. TG-DTA and FTIR revealed that the formation of CeO2 nanofibers was largely influenced by the calcination temperatures. Possible formation mechanism of CeO2 hollow nanofibers was proposed.

Effects of acetic acid on microstructure and electrochemical properties of nano cerium oxide films coated on AA7020-T6 aluminum alloy

Nano cerium oxide films were applied on AA7020-T6 aluminum alloy and the effects of acetic acid concentration on the microstructure and electrochemical properties of the coated samples were investigated by using scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and potentiodynamic polarization methods. It has been found that by increasing the acetic acid/CeCl3·7H2O molar ratio, high uniform and crack-free films with well-developed grains were obtained and grain sizes of the films decreased. Elimination of cracks and decreasing grain size of the nano cerium oxide films caused corrosion resistance to increase.

Determination of Trace Metal Impurities in Cerium Oxide by Fluorination-Assisted ETV-ICP-AES after HPLC Separation

A new method for the separation and detection of trace metal impurities in cerium oxide (CeO_2) using HPLC combined with electrothermal vaporization (ETV)-ICP-AES was developed. This combination links the high separation power of HPLC and high sensitivity of ETV-ICP-AES. The 2-ethylhexyl hydrogen 2-ethylhexylphosphate (P_(507)) resin was used as stationary phase for the separation of metallic impurities in order to eliminate severe spectral interferences of the matrix. The dilute nitric acid was adopted as mobile phase for eluting Cu, Mn, Ni and La. The separation process can be accomplished in about 30 min. After concentrating the eluate by evaporation, the trace impurities were determined by using ETV-ICP-AES with the addition of 6% PTFE slurry as chemical modifier. The proposed method was applied to the analysis of CeO_2 with satisfactory recoveries.

Effects of Cerium Oxide on Ni/Al_2O_3 Catalysts for Decomposition of CH_4 and C_2H_4

Characteristics of carbon deposition of CH 4 and C 2H 4 decomposition over supported Ni and Ni Ce catalysts were studied by using a pulse reaction as well as BET, TPR, XPS and hydrogen chemisorption techniques. It is found that there is a metal semiconductor interaction (MScI) in the Ni Ce catalyst, and the effect of MScI on the carbon deposition of CH 4 decomposition is opposite to that of C 2H 4. A novel model of carbon deposition of CH 4 or C 2H 4 decomposition was proposed.

Biochemical and cellular evidence of the benefit of a combination of cerium oxide nanoparticles and selenium to diabetic rats

AIM: To study the combinative effects of nanocerium and selenium in a murine model of diabetes. METHODS: Cerium oxide (CeO2) nanoparticles (60 mg/kg per day) and sodium selenite (5 μmol/kg per day) aloneor in combination, or the metal form of CeO2 (60 mg/kg) were administered for 2 wk by intraperitoneal injection to streptozotocin-induced diabetic rats. At the end of treatment blood was collected, liver tissue dissected and then oxidative stress markers, extent of energy depletion and lipid prof ile were evaluated.RESULTS: Antioxidant enzymes and high density lipoprotein decreased whereas oxidative stress, adenosine diphosphate/adenosine triphospahte levels, cholesterol, triglyceride and low density lipoprotein increased on induction of diabetes. All were improved by a combination of nanocerium and sodium selenite. There was a relative amelioration by CeO2 nanoparticles or sodium selenite alone, but the metal form of CeO2 showed no signif icant improvement. CONCLUSION: The combination of nanocerium and sodium selenite is more effective than either alone in improving diabetes-induced oxidative stress.

Catalytic performance of cerium iron complex oxides for partial oxidation of methane to synthesis gas

The cerium iron complex oxides oxygen carrier was prepared by the co-precipitation method. The reactions between methane and lattice oxygen from the complex oxides were investigated in a fixed micro-reactor system. The reduced oxygen carder could be re-oxidized by air and its initial state could be restored. The characterizations of the oxygen carders were studied using XRD, O2-TPD, and H2-TPR. The results showed that the bulk lattice oxygen of CeO2-Fe2O3 was found to be suitable for the partial oxidation of methane to synthesis gas. There were two kinds of oxygen species on the oxygen carrier： the stronger oxygen species that was responsible for the complete oxidation of methane, and the weaker oxygen species （bulk lattice oxygen） that was responsible for the selective oxidation of methane to CO and H2 at a higher temperature. Then, the lost bulk lattice oxygen could be selectively supplemented by air re-oxidation at an appropriate reaction condition. CeFeO3 appeared on the oxygen carrier after 10 successive redox cycles, however, it was not bad for the selectivity of CO and H2.

Surface Chemistry and Catalysis of Rare Earth Oxides I．A Study of the Reactivity of Surface Hydroxyls on CeO_2 and Pr_6O_（11） by FT－IR Spectroscopy

The surface chemical properties of CeO2 and Pr6O11 have been investigated with FT-IR spectroscopy. The reactivities of surface hydroxyls were tested through the reaction of CO. Surface formate species are formed on CeO2 and Pr6O11 under CO atmosphere at 200℃ . and the reaction becomcs more prevailing at higher temperatures especially for partially reduced samples. The surface formate species are produced via the reaction of CO with surface hydroxyls which was confirmed by the reaction of CO with D2-treated CeO2 and Pr6O11. The Surface formate can be oxidized to carbonate at temperatures exceeding 300 ℃, and the surface hydroxyls could be recovered as the formate species decompose or are oxidized to carbonate species. The roles played by the surface hydroxyls and surface active sites in the CO oxidation are discussed.

Effect of Surface Modification on Behaviors of Cerium Oxide Nanopowders

Study was made on the effect of surface modification on the behaviors of cerium oxide nanopowders.A surfactant-sodium dodecyl sulfate（C12H25SO4Na）was used to modify the surface of CeO2 powder particles.The unmodified and modified CeO2 powders were characterized by using a powder comprehensive characteristic tester,laser particle size analyzer,specific surface area tester,X-ray diffraction tester,and a scanning electron microscope.The testing and analysis results showed that C12H25SO4Na surface modification might increase the flowability and dispersity,and decrease the specific surface area and agglomeration of CeO2 powders.The mechanism of the surface modification of CeO2 powder particles was also discussed.

Preparation and Methanol Decomposition Activity of RutheniumSupported Ce-Doped Mesoporous TiO_2 Oxide

Mesoporous TiO2-CeO2 mixed oxide(m-TiO2-CeO2) were synthesized using n-cetylpyridinium chloride (C16PyCl) as a structure-directing agent under the neutral conditions and room temperature. The synthesized mesoporous samples were characterized by FT-IR, XRD, and N2 adsorption BET methods. The incorporation of Ce3+ ions into the channel wall improves the stability of the mesoporous structure obviously. After ruthenium being loaded by the impregnating method, the Ru particle strongly interacts with the mesoporous mixed supports. Although a part of the particles are possible to block the support pores, the catalytic activity of ruthenium supported on the m-TiO2-CeO2 for methanol decomposition to carbon monoxide and hydrogen is significantly higher than that of ruthenium supported on m-TiO2. A synergistic effect between CeO2 and TiO2 was observed for promoting the catalytic properties of Ru.

Cerium Oxide Film Prepared from Molten Salts

Cerium oxide film formed on the nickel electrode at 453 K in LiNO3-KNO3 molten salts. The molten salt background and the cathode process of Leeds on the nickel electrode were studied by using cyclic voltammetry. The cathodic reaction mechanism of the molten salt background was: O-2(-)+e <----> O-2(-2); O-2+2NO(3)(-) --> 2NO(2)(-)+2O(2). According to the results of SEM and XPS, cerium oxide film, which is composed of CeO2, can form on the nickel electrode at - 1.850 V vs. Ag/AgNO3 (0.1 mol/L) reference electrode.

Effect of Temperature on Pitting Corrosion Resistance of 316 Stainless Steel Coated by Cerium Oxide Film in 3.5% NaCl Solution

One of the main problems of stainless steel is its poor pitting corrosion resistance in the aggressive environment containing Cl-, such as seawater. In this paper we investigated the corrosion behavior of the 316 stainless steel coated by cerium oxide nanocoating prepared by sol-gel process. Potentiodynamic polarization and electrochemical impedance spectroscopy （EIS） were used to study the corrosion behavior of cerium oxide nanocoatings in 3.5% NaCl solution. The microstructure of the cerium oxide was examined by scanning electron microscopy （SEM） and the formed phases was identified by X-ray diffraction （XRD）. The pitting corrosion resistance of the cerium oxide nanocoating was found to be improved after heat treatment of the cerium oxide nanocoating at 300℃ for 30 min.