Eu2O3 Nanocrystals Research Articles

Catalytic oxidation of lignin and model compounds over nano europium oxide

The heterogeneous catalyst for depolymerization of lignin has a good application prospect because the catalyst is easy to recover. Although heterogeneous noble metal catalysts exhibit excellent activity under mild conditions, high prices restrict their wide use. In recent reports, nano rare earth oxide catalysts have shown good performance in the catalytic oxidation of lignin, and their prices are relatively low, which has good research value. Our study found that rare earth oxide nanocatalysts have obvious structure-activity relationship in the catalytic oxidation of lignin. To investigate theses structure-dependent behaviour and the reaction mechanism, a series of shape-specific Eu2O3 nanocrystal catalysts (spheres, spindles, sheets and rods) with well-defined crystal facets were synthesized and investigated. The four catalysts show increasing conversions from 54.6% to 91.2% in the sequence of nanospindles, nanospheres, nanosheets and nanorods, under condition of 1 MPa O2, 493 K and 8 h. These results demonstrate that the Eu2O3 nanocrystal is structure-sensitive. It is found that the surface crystal facets of Eu2O3 nanocrystals play crucial roles in the catalytic properties. Among the nanocrystals, Eu2O3 nanorods with well-defined (220) crystal facets displayed superior catalytic activity. It is deduced that the high reactivity of Eu2O3 nanorods is related to the abundant lattice oxygen which is benefit to active oxygen species. A plausible reaction pathway that involves the Mars-van Krevelen mechanism was proposed.

Ultrasensitive Point-of-Care Test for Tumor Marker in Human Saliva Based on Luminescence-Amplification Strategy of Lanthanide Nanoprobes.

The point‐of‐care detection of tumor markers in saliva with high sensitivity and specificity remains a daunting challenge in biomedical research and clinical applications. Herein, a facile and ultrasensitive detection of tumor marker in saliva based on luminescence‐amplification strategy of lanthanide nanoprobes is proposed. Eu2O3 nanocrystals are employed as bioprobes, which can be easily dissolved in acidic enhancer solution and transform into a large number of highly luminescent Eu3+ micelles. Meanwhile, disposable syringe filter equipped with nitrocellulose membrane is used as bioassay platform, which facilitates the accomplishment of detection process within 10 min. The rational integration of dissolution enhanced luminescent bioassay strategy and miniaturized detection device enables the unique lab‐in‐syringe assay of tumor marker like carcinoembryonic antigen (CEA, an important tumor marker in clinic diagnosis and prognosis of cancer) with a detection limit down to 1.47 pg mL−1 (7.35 × 10−15 m). Upon illumination with a portable UV flashlight, the photoluminescence intensity change above 0.1 ng mL−1 (0.5 × 10−12 m) of CEA can be visually detected by naked eyes, which allows one to qualitatively evaluate the CEA level. Moreover, we confirm the reliability of using the amplified luminescence of Eu2O3 nanoprobes for direct quantitation of CEA in patient saliva samples, thus validates the practicality of the proposed strategy for both clinical diagnosis and home self‐monitoring of tumor marker in human saliva.

Shape control over microwave hydrothermally grown Y2O3:Eu by europium concentration adjustment

Two-step synthesis of Y2O3:Eu nanostructures was performed. It includes microwave driven hydrothermal and calcination stages. Performed route results in crystallization of Y4O(OH)9(NO3):Eu crystals initially, then Y2O3:Eu crystals after calcination. Arranged Eu contents in relation to overall cation quantity were set to 2 mol%, 10 mol% and 20 mol%. Varying europium concentrations influence habit of obtained Y4O(OH)9(NO3):Eu crystals from needle-like to plate-like and as a result, also shapes of final Y2O3:Eu nanostructures. Additionally, certain amount of Eu2+ ions was detected in as-grown material using laser spectroscopy and decay kinetics measurements. Obtained material was calcined at 1200 °C in the air, which results in oxidation of Eu2+ ions and crystallization of small number of cubic Eu2O3 nanocrystals. Characterization of obtained materials was performed using XRD, SEM, TEM, EDX, CL, Raman and photoluminescence spectroscopy.

Structural and optical properties of nanoparticulate Y2O3:Eu2O3

Nanoparticulate Y2 O3 :Eu2 O3 with a small, uniform particle size and a well-defined composition was synthesized using a low temperature microwave plasma process. The structural evolution and the luminescence properties were studied in different states of annealing and Eu2 O3 addition using X-ray diffraction, transmission electron microscopy, and UV-photoluminescence spectroscopy. As synthesized, the samples were amorphous and showed only weak luminescence. Subsequent annealing steps from 500°C to 800°C lead to the formation and growth of cubic Y2 O3 :Eu2 O3 nanocrystals (5–20 nm) and a concomitant strong increase of the luminescence yield already at small grain sizes in the range of 10 nm. No self-quenching effects were observed up to 11 mol% Eu2 O3 .

Structural and optical properties of nanoparticulate Y2O3:Eu2O3 made by microwave plasma synthesis

Nanoparticulate Y2O3:Eu2O3 with a small, uniform particle size and a well-defined composition was synthesized using a low temperature microwave plasma process. The structural evolution and the luminescence properties were studied in different states of annealing and Eu2O3 addition using X-ray diffraction, transmission electron microscopy, and UV-photoluminescence spectroscopy. As synthesized, the samples were amorphous and showed only weak luminescence. Subsequent annealing steps from 500°C to 800°C lead to the formation and growth of cubic Y2O3:Eu2O3 nanocrystals (5–20 nm) and a concomitant strong increase of the luminescence yield already at small grain sizes in the range of 10 nm. No self-quenching effects were observed up to 11 mol% Eu2O 3.

Understanding the growth of Eu2O3 nanocrystal films made via electrophoretic deposition

Eu2O3 nanocrystals, surface-functionalized with oleic acid, were assembled into transparent thinfilms via electrophoretic deposition (EPD). Suspended in a non-polar solvent (hexane), thenanocrystals were cast into stable films on both the cathode and the anode. We characterizedthe nanocrystal films using optical microscopy, energy dispersive spectroscopy andphotoluminescence spectroscopy. Scanning electron microscopy and atomic force microscopyprovided information regarding the morphology, topology and surface coverage of the films.These homogeneous, densely packed films were composed predominantly of agglomerates (∼15 nm) ofthe Eu2O3 nanocrystals rather than of individual nanocrystals. Nonetheless,the films possessed low root mean square (RMS) roughness (∼1.4 nm). High transparency of the film in the visible region was facilitated by the densepacking and the small diameter of the agglomerates, which reduced transmission losses dueto scattering. The effect of EPD process parameters (applied voltage and nanocrystalconcentration) on the growth uniformity and the thickness of the films was examined viasurface contact profilometry. We discovered a correlation among the said EPDprocess parameters, the overall quality and thickness of these transparent films,which provided insight into the mechanisms of the nanocrystal deposition process.

Synthesis of Mesoporous Eu2O3 Microspindles

Mesoporous Eu2O3 microspindles have been prepared by a facile solution process followed by subsequent heat treatment. By adding urea stepwise and varying the reaction time, the dimension of the Eu2O3 microspindles can be easily tuned from 250 × 100 nm to 900 × 400 nm. The products were characterized by X-ray diffraction, small-angle X-ray scattering, (high-resolution) transmission electron microscopy, scanning electron microscopy, N2 adsorption, and photoluminescence spectroscopy. The Eu2O3 samples exhibit a relatively broad pore-size distribution, and the wall of the pore is constructed by well-crystalline Eu2O3 nanocrystals with diameters of about 15 nm. A possible formation mechanism of the mesoporous microspindles was also discussed.

Photoluminescence of Ga2S3:Eu nanocrystals

The photoluminescence (PL) of Ga2S3-5 mol % Eu2O3 nanocrystals prepared by mechanical comminution of the initial compound has been studied in the temperature range from 77 to 300 K. It is established that the PL spectrum of nanocrystals, in comparison to that of a massive sample, extends over a broader wavelength interval (430–620 nm) and has two maxima (at 507 and 556 nm) instead of one. The intensity of emission from nanocrystals is significantly higher than that from the massive crystal. The halfwidth in both cases varies with the temperature in proportion to T1/2. The intensity of emission at 556 nm for nanocrystals depends on the temperature as lgI ∼ 1/T, this dependence having three linear portions corresponding to an activation energy of 0.04, 0.16, and 0.43 eV. The PL bands with maxima at 507 and 556 nm are assigned to the intracenter 4f65d4f7 transitions in Eu2+ ions.

Self assembly of Eu2O3 nanocrystals and nanoneedles

AbstractThe self‐assembly of europium oxide (Eu2O3) nanocrystals into anisotropic one dimensional europium hydroxychloride (Eu(OH)2Cl) nanostructures is reported. Eu2O3 nanocrystals, synthesized via colloidal chemistry, form one dimensional structures via a stepwise assembly and growth procedure. Transmission electron microscopy (HR‐TEM) reveals the shape and crystal lattice spacing of the nanostructures, whereas X‐ray diffraction (XRD) measurements characterize the nanocrystals' crystallinity. Photoluminescence measurements indicate changes in the site location and environment of the Eu3+ ions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Synthesis of Eu2O3 nanocrystals in a new polymorph in corundum structure by reactive doping in a mesoporous Al2O3 powder

Synthesis of Eu2O3 nanocrystals in a new polymorph in corundum structure by reactive doping in a mesoporous Al2O3 powder

Synthesis and Properties of Sub-50-nm Europium Oxide Nanoparticles

Eu2O3 nanocrystals are synthesized by a colloidal precipitation route in the size range 2–40 nm. The nanocrystals are passivated with a surface layer of trioctyl phosphine oxide (TOPO) in order to eliminate surface recombination effects. When pumped at 254 nm (4f → 5d transition) the nanocrystals exhibit red luminescence characteristic of 5D0 → 7Fn Eu3+ transitions within the cubic form of Eu2O3. The efficiency of the luminescence is increased by a factor of five as the particle size drops below 10 nm; it is suggested that confinement of the long lifetime Eu3+ excitation within the nanocrystal is responsible for this effect.

Lanthanide Luminescence as a Probe of Nanocrystalline Materials

The sharp lines in the optical spectra of lanthanide ions in solids are sensitive to the local environment surrounding the ion and, therefore, provide a local probe to study new materials. This paper reports the laser spectroscopic characterization of a series of Eu2O3 nanocrystals, which serve as a model compound for understanding the spectroscopy of lanthanides in nanocrystalline materials. The optical spectra of Eu2O3 particles with diameters of approximately 18 to 4 nm show an increase in inhomogeneous broadening and a transition to a very disordered phase as the particle size decreases. The 5D0 fluorescence transients of the nanocrystals are shorter than in bulk material show no clear trend as a function of particle size but do become single exponential for 6- and 4-nm particles.