Cerium Concentration Research Articles

Generation of cold white light by using energy transfer process in single phase Ce3+/Tb3+ co-doped CaSrAl2SiO7 phosphor

Single phased CaSrAl2SiO7 phosphor singly doped with different concentrations of trivalent cerium and terbium; and co-doped with varying Tb3+ concentration were prepared by standard solid state reaction (SSR) method. The crystallinity and particle morphology of the product samples were analysed by using XRD and TEM characterizations. Photoluminescence characterizations of singly doped and co-doped samples were studied in detail. CaSrAl2SiO7:Ce3+,Tb3+ phosphor exhibit a broad blue emission band at 410 nm and some sharp emission bands in blue green and yellow regions, which originate from Ce3+ and Tb3+ ions, respectively. By increasing the concentration of Tb3+ ions while fixing Ce3+ concentration in the host lattice energy transfer takes place from Ce3+ to Tb3+ ions which create luminescence emission in white region. CaSrAl2SiO7:Ce3+,Tb3+ phosphors are proved to be promising candidates for white lighting for outdoor illumination.

The effects of exogenous cerium on photosystem II as probed by in vivo chlorophyll fluorescence and lipid production of Scenedesmus obliquus XJ002.

Cerium is the most abundant rare earth metal in the earth's crust, and it has deleterious effects on aquatic ecosystems from fertilizer runoff. Scenedesmus obliquus is an oil-rich microalga that grows rapidly and is sensitive to many kinds of toxins. Given that microalgae are useful indicators of eutrophication and toxic stress, it was found that lower concentrations of cerium (0.50-5.00 mg·L-1 ) stimulated algal growth and increased chlorophyll a content, whereas higher concentrations (above 50.00 mg·L-1 ) had an inhibitory effect on algal growth and chlorophyll a content. The algal growth rate and chlorophyll a content peaked at a cerium concentration of 5.00 mg·L-1 . Both the donor and acceptor sides of photosystem II (PSII) reaction centers were sensitive to cerium-induced stress. Specifically, high concentrations of cerium damaged the oxygen evolving complex and PSII reaction center and suppressed electron transport at the donor and receptor side of the reaction center, influencing the absorption, transfer, and application of light energy in S. obliquus XJ002. In addition, we established a simple method to quantify the intracellular lipid content of S. obliquus XJ002, and the optimum staining conditions for Nile red were as follows: volume percentage of dimethyl sulfoxide was 2%, the concentration of Nile red was 2.0µg·mL-1 , and the staining time of Nile red was 5 min. The addition of cerium resulted in a significant increase in the total lipid content of XJ002. When the concentration of cerium was 50 mg·L-1 , the total lipid content was 16.26% higher than the control group. This information will enhance our ability to utilize microelement fertilizer in biomass accumulation programs and will help to further reveal the key regulatory factors in the lipid metabolism, and would lay the foundation for promoting the research of microalgae bioenergy.

SAXS Study of the Structure of Fibrous Ceric Hydrogen Phosphate Gels

Gel-like ceric hydrogen phosphates with unusual 1D fibrous structure are known since the end of 19th century. Nevertheless, the structure of these materials is still poorly understood. Here we first have applied small angle X-ray scattering (SAXS) technique to get a deeper insight into the structure of wet ceric hydrogen phosphate gels synthesized from ceric phosphate solutions with various cerium concentration. To interpret SAXS data, we used a structural model considering interparticle interaction. The quantity of independent model parameters was determined by the number of independent singular vectors and by the number of Shannon channels. Finally, key parameters characterizing the scattering from gels have been determined.

Temperature Dependence of the Electrical Resistivity of Electron-Doped Cuprates

Experimental data on the temperature dependence of electrical resistivity are analyzed for electron-doped Nd2 – xCexCuO4 – δ cuprates in a wide range of cerium concentrations 0.12 ≤ x ≤ 0.20. It is shown that, in a wide temperature range above the superconducting transition temperature, the electrical resistivity mainly exhibits quadratic temperature dependence and decreases sharply at concentrations of x ≥ 0.17. Theoretical analysis based on the microscopic t – J model for strongly correlated electrons shows that the quadratic temperature dependence of electrical resistivity is attributed to electron scattering by spin excitations. To describe these excitations, a model of antiferromagnetic (AFM) spin fluctuations in the paramagnetic phase is proposed; the intensity of these fluctuations depends on the AFM correlation length. The quadratic temperature dependence of electrical resistivity agrees well with experimental data.

Modeling proton-exchange-membrane fuel cell performance/degradation tradeoffs with chemical scavengers

One of the primary limiting factors for proton-exchange-membrane (PEM) fuel-cell lifetime is membrane degradation driven by operational stressors such as generation of highly reactive radical species, which result in cell failure and voltage decay. To extend the lifetime of the membrane, cerium ions are added to the membrane to mitigate the effects of chemical degradation by scavenging radicals produced by crossover of reactant gases across the PEM. Although cerium has shown to be very effective at reducing chemical degradation during PEM fuel cell operation, the cerium ions also lead to a decrease in performance due to changes in the membrane transport properties and possible site blockage in the catalyst layers. In this paper, a full-cell, transient performance and durability model is presented in which a micro-kinetic framework accounts for gas crossover induced degradation and concentrated-solution theory describes transport in the PEM. The transport model takes into account the coupled nature of the electrochemical driving forces that cause transport of cerium ions, protons, and water. The cell model predicts the migration of cerium out of the membrane and into the catalyst layers and its impact on performance. A comparison between dilute-solution-theory and concentrated-solution-theory models shows how water management in the cell also effects cerium distribution, where higher relative humidity leads to better retention of cerium in the membrane. A voltage loss breakdown shows that cerium leads to performance losses in the cell both by decreasing proton activity and by modifying transport properties of water and protons through the membrane. Transient simulations show that the optimal tradeoff between performance and durability metrics is reached at low cerium concentrations in the membrane (less than 1% of membrane sulfonic acid sites occupied by cerium for our analysis). Finally, analysis of membrane thickness and catalyst layer thickness as design parameters shows that thicker membranes and thinner catalyst layers best optimize both performance and durability.

Photoluminescence and decay characteristics of cerium, gallium and vanadium - containing borate-based bioactive glass powders for bioimaging applications

Biomaterials having photoluminescent properties play a crucial role in real-time bioimaging after in vivo implantation. In this study, photoluminescence properties and decay characteristics of the borate-based 13–93B3 glasses containing different concentrations of cerium, gallium, and vanadium oxides were investigated for biomedical applications. The borate-based bioactive glass powders were prepared using melt-quench technique and size reduction was performed through planetary ball milling. Bioactivity of the prepared powders was investigated in simulated body fluid at 37 °C under static conditions. The photoluminescent properties and decay kinetics of the as-prepared and the SBF-treated bioactive glass powders were analyzed by steady-state and time-resolved photoluminescence measurements. Results revealed that the cerium activated glasses exhibited an intense luminescence centered at 538 nm. Broad-band emission of the gallium and vanadium doped samples was centered at 440 and 572 nm, respectively. All of the SBF-treated glasses exhibited enhanced lifetimes and bi-exponential decays both in nanosecond and microsecond regime measurements. It was concluded that depending on the dopant concentration, bioactive glass particles prepared in the study showed remarkable photoluminescence and have potential to be used in bioimaging applications.

Evaluation of structural, optical, dielectric, electrical, and magnetic properties of Ce3+ doped Cu0.5Cd0.25Co0.25Fe2-xO4 spinel nano-ferrites

Rare earth cerium (Ce3+) doped Cu0.5Cd0.25Co0.25CexFe2-x O4 (x = 0, 0.0125, 0.025, 0.0375, 0.05) spinel ferrites nanoparticles were synthesized via co-precipitation technique. XRD, FT-IR, UV-VIS, VSM, LCR and current-voltage measurement techniques were utilized to investigate the structural parameters, metal stretching vibrations, indirect energy band gap, magnetic parameters and electrical behavior of synthesized ferrite powders respectively. The XRD patterns confirmed the remarkable reduction in crystallites size, cell volume and lattice constant while both densities (ρx,ρbulk) tends to increase with rise in Ce3+contents(x). The indirect energy band gaps (Eg) and the DC electrical resistivities were found in decreasing order from 3.48 to 2.50 eV and 9.902×107 to 0.142×107(ohm-cm) respectively at room temperature (303 K) with Ce3+ doping concentration. LCR meter inveterate that the dielectric constant had declining, and ac conductivity had growing trend at fix value of cerium concentration with rise of frequency from 8 Hz to 8 MHz. The soft magnetic properties can be significantly improved by the small amount of Ce3+ ion doping (x = 0.0375) with an increase of the saturation magnetization (Ms), and retentivity (Mr).

New sonochemiluminescence involving solvated electron in Ce(III)/Ce(IV) solutions

The moving single-bubble sonoluminescence of Ce3+ in water and ethylene glycol solutions of CeCl3 and (NH4)2Ce(NO3)6 was studied. As found, a significant part of intensity of the luminescence (100% with cerium concentration less than 10–4 M) is due to the sonochemiluminescence. A key reaction of sonochemiluminescence is the Ce4+ reduction by a solvated (or hydrated in water) electron: Ce4+ + es (eaq) → *Ce3+. Solvated electrons are formed in a solution via electrons ejection from a low-temperature plasma periodically generated in deformable moving bubble at acoustic vibrations. Reactions of heterolytic dissociation of solvents make up the source of electrons in the plasma. In aqueous CeCl3 solutions, the Ce4+ ion is formed at the oxidation of Ce3+ by OH radical. The latter species originates from homolytic dissociation of water in the plasma of the bubble, also penetrating from the moving bubble into the solution. The sonochemiluminescence in cerium trichloride solutions are quenched by the Br− (acceptor of OH) and H+ ions (acceptor of eaq). In water and ethylene glycol solutions of (NH4)2Ce(NO3)6, the sonochemiluminescence also quenched by the H+ ion. The sonochemiluminescence in CeCl3 solutions is registered at [Ce3+] ≥ 10–5 M. Then the sonochemiluminescence intensity increases with the cerium ion concentration and reaches the saturation plateau at 10–2 M. It was shown that sonophotoluminescence (re-emission of light of bubble plasma emitters by cerium ions) also contributes to the luminescence of Ce3+ in solutions with [Ce3+] ≥ 10–4 M. If the cerium concentration is more than 10–2 M, a third source contributes to luminescence, viz., the collisional excitation of Ce3+ ions penetrating into the moving bubble.

In Vitro Studies of Ce-Doped Hydroxyapatite Synthesized by Sol–Gel Method for Biomedical Applications

The present study was focused on the synthesis and characterization of cerium with hydroxyapatite for biomedical applications. Hydroxyapatite (HAp) substituted with variable concentration (0.075, 0.150, 0.225%) of cerium (Ce) was synthesized by sol–gel method. The structural and morphological properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDAX). The average crystallite size of the synthesized samples was determined as 20 nm. The functional group has been identified by FTIR. Antibacterial and anti-inflammatory focused the antibacterial activity and albumin denaturation of cerium. Blood compatibility was performed by hemolytic assay. The structural property was characterized by X-ray diffraction and crystallite size was determined as 20 nm. The FTIR spectra confirmed the presence of hydroxyl and phosphate functional groups. Antibacterial studies revealed that all cerium-doped hydroxyapatite samples exhibit good antibacterial activity against the pathogens Streptococcus oralis and Streptococcus pyogenes. Hemolysis ratios of the cerium-doped hydroxyapatite sample indicate good blood compatibility. Anti-inflammatory results exhibit high inhibition percentage of albumin denaturation for cerium-doped hydroxyapatite samples. This study suggests that the cerium proves that it is a good material for biomedical applications.

Fabrication and scintillation characterizations of high concentration Ce[formula omitted] doped BaF2 transparent ceramic

In this study, high concentration (5 mol%) of cerium doped barium fluoride transparent ceramic was fabricated by hot pressing method t a temperature of 1200 °C under 30 MPa. XRD (X-ray Diffraction), SEM (Scanning Electron Microscope), PLE (Photoluminescence Emission) measurements was used to investigate the phase composition, microstructure as well as photoluminescence properties of Ce3+: BaF2. XEL (X-ray Excited Luminescence) and pulse height spectrum were used to investigate the scintillation properties of this ceramic. The phase composition and microstructure analyses showed that the Ce3+: BaF2precursor nanoparticles prepared by the co-precipitation method were uniform and have a average size of 25 nm. The highest transmittance of the ceramic was 77% at the wavelength of 2300 nm. The PL (photoluminescence) spectrum showed that the 5d–4f transition of Ce3+: BaF2 transparent ceramic is located at 340 nm. X-ray excited luminescence exhibited only one violet peak at 392 nm. Scintillation decay time measurements showed only a slow component of 437 ns under 662 keV gamma excitation.

Oxidation of a lignin-derived-model compound: Iso-eugenol to vanillin over cerium containing MCM-22

A series of Ce-containing MCM-22 zeolites with varying cerium concentrations were synthesized and thoroughly studied by various spectroscopic and analytical methods. The powder XRD, FT-IR and surface area analysis confirm the presence of well-ordered MCM-22 framework. The DRUV-Vis spectral and XPS analyses confirmed the presence of cerium ion in both +3 and + 4 oxidation states with tetrahedral coordination. Interestingly MCM-22 containing a small amount of cerium ion (Si/Ce ratio of 200) facilitates a good conversion of isoeugenol (63%), with the selective formation of vanillin (75%) and the catalyst retains its activity for several cycles.

Effect of Ce3+ concentration on persistent luminescence of YAGG:Ce3+,Cr3+,Nd3+ nanophosphors obtained by the co-precipitation method

Synthesis of Y3Al2Ga3O12 garnet (YAGG) nanophosphors co-doped with Ce3+, Cr3+, and Nd3+ ions by co-precipitation is reported. The effect of Ce3+ concentration on the structure of garnet and on optical properties including persistent luminescence was investigated. The X-ray diffraction measurements showed that single garnet phase was obtained. The contraction of the crystallites size was observed with increasing the cerium concentration. The combined emission of three used co-dopants together allows to extend persistent luminescence spectral range. The photoluminescence, excitation and persistent luminescence spectra were collected and the optimal Ce3+ concentration for the highest efficiency conversion of UV and blue light into the red and the near infrared emission was determined. Based on thermoluminescence data, the effect of Ce3+ concentration on the traps redistribution was also investigated.

Influence of Al-3Ti-0.15C and Ce on Microstructure and Tensile Properties of Al-Si-Cu 319 alloy

In the present research, an attempt has been made to evaluate the effects of addition of Al-3Ti-0.15C (0.05wt%) master alloy with different concentration (0.1, 0.3, 0.5, 0.8, 1wt%) of cerium (Ce), a rare earth element on microstructure and tensile properties of Al-Si-Cu 319 alloy. Optical microscopy (OM) and field emission scanning electron microscopy (FE-SEM) with EDS analysis was employed to study the microstructural modification and existence of intermetallic compounds. Experimental results show that addition of Ce with up to 0.3wt% increases the tensile properties up to 49.13% as compared to base alloy due to refinement of α-Al and modification of eutectic silicon. In contrast, tensile properties decline above 0.3wt% addition of Ce due to formation of needle like intermetallic compounds. These Ce rich needles like intermetallic compounds suppress the effect of modification, decreasing tensile properties of modified alloy.

Hot Corrosion Behaviour of Electroless Deposited Nano-structured Cerium Oxide Coatings on Superalloy

Cerium oxide film was developed on Superni-75, via electroless method using cerium acetate and triethanolamine. Hot corrosion studies were conducted on bare substrate and the cerium oxide-coated superalloy after exposure to a molten salt environment of Na2SO4–60%V2O5 at 900 °C under cyclic conditions. The weight change measurements were taken to calculate the cyclic hot corrosion kinetics of the coatings at 900 °C. The structural features of the samples were characterized by SEM/EDS and XRD. It was observed that the corrosion rate of cerium oxide-coated superalloy is lower than that of the uncoated superalloy due to the formation of dense and protective oxide scale over the surface of the coatings. In spite of the combined effect of thermal cycling and an aggressive environment, the weight variation per unit area was found to decrease as the cerium concentration increased. Cerium oxide film was able to impede the movement of ions, thereby reducing the short-circuit diffusion of ions. Also, there was an improvement in resistance to spallation in the coated specimens with increase in cerium concentration.

Influence of metals from e-waste dismantling on telomere length and mitochondrial DNA copy number in people living near recycling sites

Metals are the primary toxicants released by electronic waste (e-waste) recycling, but their adverse effects on people working in e-waste recycling or living near e-waste sites have not been studied well. Taizhou is one of the three largest e-waste recycling locations in China. Atpresent, to prevent the environmental problems stem from e-waste dismantling, the local government has shut down all the industries in 2015. In this study, we collected blood samples of residents living near e-waste dismantling factories, and in matched reference areas in Taizhou, in December 2017, after the factories have been shut down for two years. Seventeen metals were quantified in all blood samples. Among them, the concentrations of arsenic (As), nickel (Ni), silver (Ag), lanthanum (La), and Cerium (Ce) were statistically significant higher in individuals in e-waste recycling locations than those in reference location. Length of telomere (LOT) and mitochondrialDNA copy number (MCN) were measured in blood as a marker of human health. In the e-waste dismantling location, the level LOT and MCN were elevated in resident living near e-waste sites (RE) and former working in e-waste recycling (OE) than residents living in the reference area (RF). Furthermore, Pearson correlation and multiple linear regression analysis between the changed metals and LOT, MCN in blood were performed. In RE and OE, the concentration of Ni significantly positively correlated with MCN; in OE, the Ni level significantly positively correlated with MCN and LOT. Considering that the high level of Ni, TL and mtDNA were correlated with the risk of cancer, we speculated that e-waste exposure elevate the risk of cancer, and Ni that has long been present in the body was the potential hazardous element causing cancer.

RADIO-OPTICAL response of cerium-doped lithium gadolinium bismuth borate glasses

Bismuth borate glasses containing lithium and gadolinium were doped with (0.1–2.5 mol%) of Ce and their optical and radiation response were investigated. These modified glasses exhibited photoluminescent properties in response to the radiations, which were evidenced by their broad-band spectral features around 378 nm due to 5d→4f transitions of the Ce3+ ions. The intensity response of these glasses increased with increasing concentration of cerium up to 2.0 mol% which decreased upon further increase in the concentration of cerium due to the quenching effect and cross-relaxation between the nearest ions. Gamma irradiation of samples with 1 and 2 Gy doses demonstrated an increase in the intensity of photoluminescence peaks with increase in the irradiation dose. The observed increase caused the formation of relatively more electron and hole trap centers that eventually led to more recombinations in the glass matrix. This enhancement in the intensity after irradiation was also proportional to the dose as expected and the photoluminescence peaks observed for the irradiation samples were broader than those of un-irradiated samples. The observed decrease in intensity after irradiation of samples with high cerium concentration (i.e. 2.5 mol%) may be linked to the energy transfer and dissipation occurring during cross-relaxation among the nearest cerium ions.

Fabrication and characterization of 1, 5, 10 at.% Ce:Y2O3 nanopowders

Nanopowders (particle size of about 7-14 nm) of yttrium oxide doped with cerium ions with concentrations of 1, 5, 10 at.% have been synthesized by laser ablation of the target. For the first time in the world the cerium concentration of 10 at.% in the yttrium oxide lattice has been obtained. Their morphology, structure, and scintillation properties have been investigated. No significant cathodoluminescence of the activator in the Ce3+ state has been detected in the powders, and X-ray luminescence was completely absent. Presumably, the cerium ion is in the nonradiative state of Ce4+.

Rapid visible light-driven photocatalytic degradation using Ce-doped ZnO nanocatalysts

In this work, we have reported the synthesis of Ce-doped ZnO nanostructures with different doping concentrations using simple co-precipitation method. The prepared samples were thoroughly characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), Brunauer Emmett Teller (BET), UV–Visible and photoluminescence (PL) spectroscopy. This study was conducted to investigate the effect of the doping concentration of cerium on the structural, morphological, optical, and photocatalytic properties of ZnO. The XRD pattern of synthesized materials displayed wurtzite ZnO structure. FESEM images show the formation of nanobars and nanohexanes along with agglomeration on the change in the doping concentration of Ce3+. The mesoporous nature of nanostructures is confirmed by BET. The incorporation of Ce3+ in ZnO significantly led to the redshift in the band gap in absorption spectra from 3.17 eV to 2.72 eV. The deconvoluted PL spectra revealed that the Ce doping enhances the emission in the blue region due to the transitions between 2D3/2→2Fi/2 energy levels. The Zn0.94Ce0.06O sample exhibited 9.1 times faster photocatalytic activity than the undoped ZnO, under visible light irradiation in 60 min for Methylene blue (MB) dye. The improvement in photocatalytic activity originates from the enhancement in the PL intensity. This is also in good agreement with the increase in the BET surface area for Ce-doped ZnO as compared to undoped ZnO. Thus, Ce-doping enhances the degradation rate, which makes ZnO a potential photocatalyst for the removal of organic pollutants present in water.

Corrosion Inhibition at Scribed Locations in Coated AA2024-T3 by Cerium- and DMTD-Loaded Natural Silica Microparticles under Continuous Immersion and Wet/Dry Cyclic Exposure.

Earlier studies on cerium-loaded naturally occurring silica microparticles (i.e., diatomaceous earth) demonstrated the potential to efficiently protect small scratches in epoxy-coated AA2024-T3 panels during relatively short immersion times. The current work investigates the potential of such inhibitor-loaded microparticles to protect wide and deep scribes (up to 1 mm wide) in long-time immersion testing and during cyclic (wet/dry) conditions. For this, cerium nitrate and 2,5-dimercaptothiadiazole (DMTD) were used as inorganic and organic corrosion inhibitors. The corrosion protection was evaluated using a hyphenated real-time optics/electrochemistry method and two individual local techniques measuring oxygen concentration and electrochemical impedance (LEIM) inside the scribe. SEM/EDS was used to analyze the samples after exposure. The results show significant levels of corrosion protection at damaged locations at low cerium concentrations (3.7 wt % Ce3+ relative to the total coating mass) during 30 days of immersion in salt solution. However, for a given scribe geometry, the protection was found to be dependent on the electrolyte volume with larger electrolyte/exposed metal ratios leading to short protection time. A partial replacement of the Ce3+ by DMTD in the microcarriers resulted in a higher degree of passivation than when DMTD was used alone. Wet/dry cyclic exposure tests showed that cyclic conditions can increase the buildup of stable inhibitor-containing layers in the case of cerium-loaded silica microparticles. This underlines the need for more research using wet/dry exposure conditions.

Effect of the Ce3+ concentration on laser-sintered YAG ceramics for white LEDs applications

This paper describes the laser sintering and luminescence properties of Y3Al5O12 (YAG) phosphors doped with different concentrations of Ce3+ and synthesized using the polymeric precursor method. The ceramics were sintered by a new laser sintering technique in which a CO2 laser is employed as the heating source. The resultant ceramics exhibited a homogeneous microstructure with narrow grain size distribution and high relative density. The introduction of Ce3+ ions led to luminescence quenching at a concentration above 0.5 mol% and a redshift of the emission spectrum band with increasing cerium concentration. The excitation spectrum showed two characteristic bands centered at 340 nm and 460 nm and a relative change in their intensity by change the Ce3+ concentration. The presence of a single valence (Ce3+) of cerium was determined by X-ray absorption near edge structure measurements.