Ce Nanoparticles Research Articles

Preparation of Monolayered Ce-Fe Oxides Dispersed on Graphene and Their Superior Adsorptive Behavior

We present a facile synthesis of highly dispersed Ce and Fe metal oxide nanoparticles (NPs) with the size distribution of about 1–2 nm on reduced graphene oxide (RGO). The obtained Ce-Fe/RGO hybrid material is structurally characterized by TEM, XRD, XPS, Raman, BET, and H2-TPR. The results show that the addition of Fe promotes the formation of high surface area Ce-Fe/RGO hybrid material due to the inhibition of different species on crystal growth. The enhanced adsorption properties mainly come from the monolayer dispersion and the reduced particle size of NPs on the graphene. The driving force for the adsorption is the electrostatic action between adsorbent materials with positive electricity and CR with negative electricity, and the NPs and RGO together interact with the Congo red (CR) in the adsorption process. The Ce-Fe/RGO hybrid material exhibits a high adsorption capacity of 179.5 mg g−1 for the CR in water, suggesting their potential use in water treatment.

Preparation and luminescence properties of SiO2/Lu2Si2O7:Ce composite starting from mesopore template

A chemical processing method has been developed for preparing the nanosized phosphors of Lu2Si2O7:Ce3+ (LPS:Ce) by choosing mesoporous template SBA-15 as Si source. Accordingly, the luminescent ceramic composite of SiO2/LPS:Ce has also been densified by hot pressing at elevated temperatures using composited powders with the prepared LPS:Ce phosphor particles embedded in SiO2 matrix. XRD analysis and TEM observation have been carried out for both the prepared LPS:Ce phosphors and the final SiO2/LPS:Ce ceramics, indicating complete crystallization and a well distribution of LPS:Ce nanoparticles in SiO2 component. The ultra-violet fluorescence spectra, X-ray excited luminescence spectra, and decay time of the resultant SiO2/LPS:Ce ceramic composite have also been measured, showing a blue emission from Ce3+ and a fast decay time of about 37 ns. Experimental results show that an attractive strategy has been successfully developed for producing translucent or even transparent ceramics with phosphor nanoparticles embedded in matrix. The specific route can provide an effective control of reaction channels and a uniform distribution of phosphor particles in matrix by the template guiding role from ordered mesoporous SiO2. The fabrication method thus developed could be employed in other kinds of composited ceramics.

Transformation of pristine and citrate-functionalized CeO2 nanoparticles in a laboratory-scale activated sludge reactor.

Engineered nanomaterials (ENMs) are used to enhance the properties of many manufactured products and technologies. Increased use of ENMs will inevitably lead to their release into the environment. An important route of exposure is through the waste stream, where ENMs will enter wastewater treatment plants (WWTPs), undergo transformations, and be discharged with treated effluent or biosolids. To better understand the fate of a common ENM in WWTPs, experiments with laboratory-scale activated sludge reactors and pristine and citrate-functionalized CeO2 nanoparticles (NPs) were conducted. Greater than 90% of the CeO2 introduced was observed to associate with biosolids. This association was accompanied by reduction of the Ce(IV) NPs to Ce(III). After 5 weeks in the reactor, 44 ± 4% reduction was observed for the pristine NPs and 31 ± 3% for the citrate-functionalized NPs, illustrating surface functionality dependence. Thermodynamic arguments suggest that the likely Ce(III) phase generated would be Ce2S3. This study indicates that the majority of CeO2 NPs (>90% by mass) entering WWTPs will be associated with the solid phase, and a significant portion will be present as Ce(III). At maximum, 10% of the CeO2 will remain in the effluent and be discharged as a Ce(IV) phase, governed by cerianite (CeO2).

Luminescence properties of LaF3:Ce nanoparticles encapsulated by oleic acid

Cerium ions doped lanthanum fluoride (LaF3:Ce) nanopowder as well as LaF3:Ce nanopowder whose surfaces was modified by oleic acid (OA) were synthesized by using an in-situ hydrothermal process under the various doping concentrations. Based on the XRD spectra and TEM images, it was confirmed that the crystalline structured hexagonal LaF3:Ce nanopowder was synthesized. Oleic acid was efficient for conversion of the water dispersible LaF3:Ce nanoparticles to hydrophobic ones. Surface modification was verified by FTIR absorption spectrum as well as TEM images, showing no agglomeration between 5 and 10nm scaled particles. Photoluminescence based on 5d⟶4f electronic transition of cerium ions excited at λex ∼256nm for both neat and OA encapsulated LaF3:Ce nanoparticles decreases as the cerium concentration increases, while the quantum yields of OA encapsulated nanoparticles were much lower than the neat particles due to low photon transmittance of OA at the range longer than ∼350nm.

Agglomerated nanoparticles of hydrous Ce(IV)+Zr(IV) mixed oxide: Preparation, characterization and physicochemical aspects on fluoride adsorption

Abstract Hydrous Ce(IV)–Zr(IV) oxide (Ce/Zr ∼ 1:1, mol/mol) (HCZMO) prepared by simple chemical precipitation was nanoparticles (60–70 nm) agglomerate with irregular surface morphology. The BET surface area, pore volume and pH zpc were estimated to be 185.04 m 2 g −1 , 0.1219 cm 3 g −1 and 5.8 (±0.2), respectively. Investigation of fluoride adsorption over HCZMO from its aqueous phase at an optimized pH ∼ 6.0 showed that the adsorption kinetics and equilibrium data described, respectively, the pseudo-second order equation ( R 2 = 0.98–0.99) and the Langmuir isotherm ( R 2 > 0.99) very well. Values of the computed Arrhenius activation energy, E a (1.16 kJ mol −1 ), Langmuir monolayer capacity, θ (19.5 mg g −1 ), D–R adsorption energy, E D–R (15.05 kJ mol −1 ) and isosteric heat of reaction, Δ H r (0.518 kJ mol −1 ) suggested that the fluoride has high affinity for homogeneous HCZMO surface for adsorption. Evidences appeared from the equal distribution co-efficient values and too well Langmuir isotherm fit. The fluoride adsorption reactions at 298–313 K with HCZMO were spontaneous (Δ G 0 = negative) despite endothermic nature (Δ H 0 , kJ mol −1 = +3.53, +4.04), owing to the increase of entropy (Δ S 0 , J mol −1 K −1 = +12.4, 13.8). More than 95% fluoride was released from F − HCZMO (24.8 mg F − g −1 ) by 1.0 M NaOH, confirming the ion-exchange adsorption mechanism inclining to chemisorption. 1 g HCZMO per liter of a groundwater (F − : 4.40 mg L −1 ) can reduce fluoride level below 1.5 mg L −1 in batch treatment.

Effects of Ce(III) and CeO₂ nanoparticles on soil-denitrification kinetics.

Cerium (Ce)-based compounds, such as CeO₂ nanoparticles (NPs), have received much attention in the last several years due to their popular applications in industrial and commercial uses. Understanding the impact of CeO₂ NPs on nutrient cycles, a subchronic toxicity study of CeO₂ NPs on soil-denitrification process was performed as a function of particle size (33 and 78 nm), total Ce concentration (50-500 mg L(-1)), and speciation [Ce(IV) vs. Ce(III)]. The antimicrobial effect on the soil-denitrification process was evaluated in both steady-state and zero-order kinetic models to assess particle- and chemical-species specific toxicity. It was found that soluble Ce(III) was far more toxic than Ce(IV)O₂ NPs when an equal total concentration of Ce was evaluated. Particle size-dependent toxicity, species-dependent toxicity, and concentration-dependent toxicity were all observed in this study for both the steady-state and the kinetic evaluations. Changes in physicochemical properties of Ce(IV)O₂ NPs might be important in assessing the environmental fate and toxicity of NPs in aquatic and terrestrial environments.

Gamma irradiation effect on photoluminescence from functionalized LaF3:Ce nanoparticles

Oleic acid coated and uncoated LaF3:Ce nano-phosphor particles were synthesized by a co-precipitation method. Nanoparticles were characterized for their structure, organic coating and optical behavior using an X-ray diffraction, a Transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), UV–vis absorption and Photoluminescence spectroscopy. Sizes of nanoparticles were measured from TEM images and were also estimated using the Scherer formula. UV–vis absorption, Photoluminescent and FTIR measurements were done with nanoparticles before and after gamma irradiation up to a dose of 6.19kGy. The uncoated nanoparticles exhibit emission only at 305nm when exited with 250nm. The oleic acid coated nanoparticles exhibit emissions at 308 and 361nm when exited with 252nm. Dependence of photo luminescent intensity on gamma dose was studied and the changes were attributed to radiation induced defect traps and also to the breach or damage in the capping material.

Synthesis and Characterization of Ce‐Doped Y3Al5O12 (YAG:Ce) Nanopowders Used for Solid‐State Lighting

Nano‐Ce‐doped Y3Al5O12 (YAG:Ce) powders were synthesized by using a sol‐gel low temperature combustion method, followed by thermal annealing. The annealing temperature for enriching nanoparticles was optimized and found to be 1000°C. The process for enriching uniform nanoparticles of YAG:Ce powder was carried out by using the nanosteam technique (NST). The nanoparticles obtained from this NST treatment had a size in the range of 9–20 nm. Measurements of the photoluminescence spectra of the dispersed YAG:Ce nanoparticles solutions showed a blue shift in the photoemission with a value of ca. 10 nm in the green region. WLEDs made from the blue LED chip coated with the nano‐YAG:Ce + MEH‐PPV composite epoxy exhibit white light with a broad band luminescent spectrum and a high color rending index (CRI). The photoluminescence spectra of the YAG:Ce nanoparticles showed a potential application of the prepared nanostructured YAG:Ce phosphor not only in energy‐efficient solid‐state lighting, but also in optoelectronic devices, including organic composite solar cells. In addition, it is suggested that NST can be applied for the enrichment of uniform inorganic nanoparticles.

Hydrothermal synthesis of core-shell structured TbPO4:Ce(3+)@TbPO4:Gd(3+) nanocomposites for magnetic resonance and optical imaging.

Multi-modal imaging based on multifunctional nanoparticles provides deep, non-invasive and highly sensitive imaging and is a promising alternative approach that can improve the sensitivity of early cancer diagnosis. In this study, two nanoparticles, TbPO4:Ce(3+) and TbPO4:Ce(3+)@TbPO4:Gd(3+), were synthesized via the citric-acid-mediated hydrothermal route, and then systematically characterized by means of microstructure, photoluminescence, magnetic resonance imaging (MRI), biocompatibility, and bioimaging. The results of energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS) line scans indicated that TbPO4:Gd(3+) nanoshells about 5 nm in thickness were successfully coated on the TbPO4:Ce(3+) nanocores. X-ray diffraction (XRD) and Fourier transforms of high-resolution transmission electron microscopy (TEM) images indicated that the core-shell nanocomposites had a single crystal structure. The photoluminescence of the TbPO4:Ce(3+)@TbPO4:Gd(3+) and TbPO4:Ce(3+) nanoparticles was greatly intensified by 200 times and 100 times, respectively, compared with pure TbPO4 nanoparticles. In vitro cytotoxicity tests based on the methyl thiazolyl tetrazolium (MTT) assay demonstrated that the monodispersed nanoparticles of TbPO4:Ce(3+)@TbPO4:Gd(3+) had low toxicity. The intracellular luminescence of the nanoparticles after being internalized by HeLa cells was also observed using confocal fluorescence microscopes. MRI showed that the nanoshells of Gd-doped TbPO4 possessed a longitudinal relaxivity of 4.067 s(-1) mM(-1), which is comparable to that of the commercial MRI contrast Gd-TDPA. As a result, the core-shell structured TbPO4:Ce(3+)@TbPO4:Gd(3+) nanoparticles can potentially serve as multifunctional nanoprobes for both optical biolabels and MRI contrast agents.

Ce-Doped YAG Nanophosphor and Red Emitting CuInS2/ZnS Core/Shell Quantum Dots for Warm White Light-Emitting Diode with High Color Rendering Index

In this work, we report the solvothermal synthesis of Ce-doped YAG (YAG:Ce) nanoparticles (NPs) and their association with a free-Cd CuInS2/ZnS (CIS/ZnS) core/shell QDs for application into white light emitting diode (WLED). 1500 °C-annealed YAG:Ce NPs and CIS/ZnS core/shell QDs exhibited intense yellow and red emissions band with maxima at 545 and 667 nm, respectively. Both YAG:Ce nanophosphor and CIS/ZnS QDs showed high photoluminescence quantum yield (PL QY) of about 50% upon 460 nm excitation. YAG:Ce nanophosphor layer and bilayered YAG:Ce nanophosphor-CIS/ZnS QDs were applied on blue InGaN chip as converter wavelength to achieve WLED. While YAG:Ce nanophosphor converter layer showed low color rendering index (CRI) and cold white light, bilayered YAG:Ce nanophosphor-CIS/ZnS QDs displayed higher CRI of about 84 and warm white light with a correlated color temperature (CCT) of 2784 K. WLED characteristics were measured as a function of forward current from 20 to 1200 mA. The white light stability of bilayered nanophosphor-QDs-based WLED operated at 200 mA was also studied as a function of operating time up to 40 h. Interestingly, CRI and CCT of such device tend to remain constant after 7 h of operating time suggesting that layer-by-layer structure of YAG:Ce phosphor and red-emitting CIS/ZnS QDs could be a good solution to achieve stable warm WLED, especially when high current density is applied.

The pressure-induced phase transition studies of In2S3 and In2S3:Ce nanoparticles

A novel method, gas–liquid phase chemical deposition is developed to prepare In2S3 and In2S3:Ce nanoparticles. The structural, morphology and composition feature of these two nanoparticles is studied by XRD, HRTEM, and XPS. In situ high-pressure synchrotron X-ray diffraction studies were carried out by using a diamond-anvil cell. The doping does not influence the tetragonal-to-cubic phase transition path while results in a lower phase transition pressure of In2S3:Ce nanoparticles (4.3GPa) than that of In2S3 nanoparticles (7.1GPa). The bulk moduli of tetragonal phases are B0=87.1±4.3GPa and B0=55.6±4.1GPa, respectively. The distinct high-pressure behaviors can be explained in term of the doped ions, causing lattice distortion and reducing structural stability of the In2S3 nanoparticles and further accelerating the phase transition.

Elaboration and optimization of Ce-doped Y3Al5O12 nanopowder dispersions

This work aims at achieving homogeneous luminescent films from Ce-doped yttrium aluminium garnet (YAG:Ce) phosphors dispersed in aqueous suspensions. Colloidal luminescent suspensions of YAG:Ce nanoparticles have been successfully prepared by a solvothermal process. Powder resulting from the dried as-synthesized suspension was submitted to different thermal treatments and a thorough study of nanoparticles aqueous suspensions has been carried out, for each thermal treatment. The influence of these treatments on the structural, morphological and optical properties of YAG:Ce nanopowders were studied by means of X-ray diffraction, infrared spectroscopy and transmission electron microscopy. Besides, particles size distribution and zeta potential of YAG:Ce aqueous suspensions in different pH conditions were investigated by dynamic light and electrophoretic light scatterings, respectively, in order to characterize suspensions stability. This study enabled us to optimize heat treatment and redispersion parameters in order to achieve very homogeneous luminescent films which can be used for display or mood lighting.

Luminescent LaF3:Ce-doped organically modified nanoporous silica xerogels

Organically modified silica compounds (ORMOSILs) were synthesized by a sol-gel method from amine-functionalized 3-aminopropyl triethoxylsilane and tetramethylorthosilicate and were doped in situ with LaF3:Ce nanoparticles, which in turn were prepared either in water or in ethanol. Doped ORMOSILs display strong photoluminescence either by UV or X-ray excitation and maintain good transparency up to a loading level of 15.66% w/w. The TEM observations demonstrate that ORMOSILs remain nanoporous with pore diameters in the 5–10 nm range. LaF3:Ce nanoparticles doped into the ORMOSILs are rod-like, 5 nm in diameter and 10–15 nm in length. Compression testing indicates that the nanocomposites have very good strength, without significant lateral dilatation and buckling under quasi-static compression. LaF3:Ce nanoparticle-doped ORMOSILs have potential for applications in radiation detection and solid state lighting.

Preparation and characterization of BiFeO3@Ce-doped TiO2 core-shell structured nanocomposites

BiFeO3@TiO2–Ce composite nanoparticles with a BiFeO3 core and a Ce-doped TiO2 shell structure were fabricated via a sol–gel method. The nanoparticles were characterized by scanning electron microscopy with energy dispersive spectroscopy, X-ray diffraction, transmission electron microscopy and UV–vis diffuse reflectance spectroscopy. The results reveal that core-shell structured BiFeO3@TiO2–Ce nanoparticles show a significant redshift in the UV–vis absorption spectra in comparison with both Ce-TiO2 and BiFeO3@TiO2 nanoparticles. The photocatalytic activities of the samples were tested in the degradation of methyl orange in aqueous solutions under visible light and UV light irradiations. The core-shell structured BiFeO3@TiO2–Ce sample exhibits higher photocatalytic activity, which is attributed to the synergistic effects of BiFeO3 and cerium.

Characterisation and catalytic properties of Ni, Co, Ce and Ru nanoparticles in mesoporous carbon spheres

Ni, Co, Ce and Ru nanoparticles were inserted into templated carbon using a nanocasting technique and evaluated for the dehydration of glycerol. NiO and CeO2 preferentially yielded 5 nm uniformly sized particles that filled the mesoporous carbon via a geometric confinement effect. Ru generated Ruo and RuO2 nanoparticles that selectively migrated towards the carbon surface and did not undergo sintering, whereas Co nanoparticles containing CoO and Co3O4 showed the opposite behaviour. The stabilising effects of the Ce and Ru nanoparticles on the carbon matrix effectively prevented the aggregation of small particles, resulting in superior catalytic performance in glycerol dehydration.

X-ray luminescence of CdTe quantum dots in LaF3:Ce/CdTe nanocomposites

CdTe quantum dots have intense photoluminescence but exhibit almost no x-ray luminescence. However, intense x-ray luminescence from CdTe quantum dots is observed in LaF3:Ce/CdTe nanocomposites. This enhancement in the x-ray luminescence of CdTe quantum dots is attributed to the energy transfer from LaF3:Ce to CdTe quantum dots in the nanocomposites. The combination of LaF3:Ce nanoparticles and CdTe quantum dots makes LaF3:Ce/CdTe nanocomposites promising scintillators for radiation detection.

Non-photobleaching YAG:Ce nanoparticles for optical imaging with blue excitation

Hydrophilic Y3Al5O12 (YAG) and (YxGd1−x)3Al5O12 nanoparticles (NPs) doped with Ce3+ ions were synthesized by a solvothermal method and used for cell-imaging. The crystallite sizes and photoluminescence spectra were tuned by lanthanide ions (Gd3+, Ce3+) doping. Without any surface modification, the YAG:Ce NPs show good water solubility, colloid stability and low toxicity. The intracellular uptake of the YAG:Ce NPs was visualized using a confocal fluorescence microscope under the excitation of a 457 nm laser due to the strong absorption of fluorescent NPs in the blue region. The non-bleaching property was confirmed by comparing with organic dye Alexa488. Overall, we demonstrated that the YAG:Ce NPs can serve as an efficient fluorescence imaging agent with visible light excitation and without photo-bleaching, which shows great foreground in bio-imaging, especially with confocal imaging system for in vitro studies.

Room temperature synthesis of hydrophilic Ln3+-doped KGdF4 (Ln = Ce, Eu, Tb, Dy) nanoparticles with controllable size: energy transfer, size-dependent and color-tunable luminescence properties

In this paper, we demonstrate a simple, template-free, reproducible and one-step synthesis of hydrophilic KGdF(4): Ln(3+) (Ln = Ce, Eu, Tb and Dy) nanoparticles (NPs) via a solution-based route at room temperature. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) and cathodoluminescence (CL) spectra are used to characterize the samples. The results indicate that the use of water-diethyleneglycol (DEG) solvent mixture as the reaction medium not only allows facile particle size control but also endows the as-prepared samples with good water-solubility. In particular, the mean size of NPs is monotonously reduced with the increase of DEG content, from 215 to 40 nm. The luminescence intensity and absolute quantum yields for KGdF(4): Ce(3+), Tb(3+) NPs increase remarkably with particle sizes ranging from 40 to 215 nm. Additionally, we systematically investigate the magnetic and luminescence properties of KGdF(4): Ln(3+) (Ln = Ce, Eu, Tb and Dy) NPs. They display paramagnetic and superparamagnetic properties with mass magnetic susceptibility values of 1.03 × 10(-4) emu g(-1)·Oe and 3.09 × 10(-3) emu g(-1)·Oe at 300 K and 2 K, respectively, and multicolor emissions due to the energy transfer (ET) process Ce(3+)→ Gd(3+)→ (Gd(3+))(n)→ Ln(3+), in which Gd(3+) ions play an intermediate role in this process. Representatively, it is shown that the energy transfer from Ce(3+) to Tb(3+) occurs mainly via the dipole-quadrupole interaction by comparison of the theoretical calculation and experimental results. This kind of magnetic/luminescent dual-function materials may have promising applications in multiple biolabels and MR imaging.

Photoluminescence Properties of LaF<sub>3</sub>:Ce Nanoparticles Embedded in Polyacrylamide

Oleic acid coated LaF3:Ce nanoparticles were synthesized and embedded in polyacrylamide through a two-step procedure. In the first step nanoparticles were synthesized by adopting co-precipitation technique and in the second step, nanoparticles were embedded in polyacrylamide (PAM) hydro-gel through the solution route. Nanoparticels were characterized for their crystal structure, particle size, organic coating and photoluminescence behavior using X-ray diffracttion, SEM, TEM, FTIR and photoluminescence spectroscopy. Size of nanoparticles was estimated using the Scherer formula. Polymer nano composite (PNC) material was synthesized with two different weight percent of the nano powder viz 1.634% (termed as NG1) and 0.1664% (termed as NG2). The nanoparticle-polymer composite exhibits emissions at 308 and 370 nm. A comparison of the emission spectrum of LaF3:Ce nano-powder pellet with that of the composite suggests a suppression of emission from the PAM host in the composite.

Filter paper as template for synthesis of cerium-doped Yttrium aluminum garnet phosphors

Cerium-doped yttrium aluminum garnet phosphors with laminar structure were synthesized by a very simple method using filter paper as the structure template at 1100 °C. Three thin plate samples with different morphology were prepared via the different preparation procedures. The crystalline phase, composition, surface morphology and luminescence property of the synthesized samples are investigated by X-ray diffraction, energy dispersive X-ray analysis, scanning electron microscopy, and photoluminescence spectrum. Results indicate that the metal cations are combined with the filter paper templates and are self-assembled on the surface of filter paper. The self-assembly induced the growth of YAG: Ce crystal and the formation of the plate-like YAG: Ce samples. These plate-like bulky grains are composed of YAG: Ce nanoparticles (about 30 nm), and they show yellow–green fluorescent emissions. The YAG: Ce with laminar structure facilitates the increase of PL intensity.