Eu-doped Y2O3 Research Articles

Using different ratios of glycine to citric acid as fuel mixture in microwave-assisted combustion synthesis of Eu-doped Y2O3–Gd2O3 nanophosphors

Using different ratios of glycine to citric acid as fuel mixture in microwave-assisted combustion synthesis of Eu-doped Y2O3–Gd2O3 nanophosphors

Characterization of multifunctional nanocomposites assembled from Ag-decorated Fe3O4 and Eu-doped Y2O3

Characterization of multifunctional nanocomposites assembled from Ag-decorated Fe3O4 and Eu-doped Y2O3

Effects of substrate temperature on the structure and luminescence of transparent red-emitting Eu-doped Y2O3 thin films

Effects of substrate temperature on the structure and luminescence of transparent red-emitting Eu-doped Y2O3 thin films

Europium-Doped Y2O3-Coated Diatomite Nanomaterials: Hydrothermal Synthesis, Characterization, Optical Study with Enhanced Photocatalytic Performance

Eu-doped Y2O3 coated diatomite nanostructures with variable Eu3+ contents were synthesized by a facile hydrothermal technique. The products were characterized by means of energy dispersive X-ray photoelectron spectroscopy (EDX), scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), Brunauer–Emmett–Teller (BET), UV-vis diffuse reflectance spectroscopy, and photoluminescence spectroscopy techniques. As claimed by PXRD, the particles were crystallized excellently and attributed to the cubic phase of Y2O3. The influence of substitution of Eu3+ ions into Y2O3 lattice caused a redshift in the absorbance and a decrease in the bandgap of as-prepared coated compounds. The pore volume and BET specific surface area of Eu-doped Y2O3-coated diatomite is greater than uncoated biosilica. The sonophotocata-lytic activities of as-synthesized specimens were evaluated for the degradation of Reactive Blue 19. The effect of various specifications such as ultrasonic power, catalyst amount, and primary dye concentration was explored.

Revisiting the Charge Transfer State in Tetravalent Lanthanide Doped Oxides: Up to Date Phenomenological Description

The coloring of oxides doped with Ln4+ has been the subject of much scientific research related to its application as pigments. However, until now, a rational explanation of this phenomenon had not been presented. Here is shown a scheme from a phenomenological perspective, that allows us to rationalize the experimental observations in the optical absorption spectra of Ln-doped (Ln = Ce, Pr and Tb) Y2O3 and Y4Zr3O12. This analysis was based on the explanation of the ligand-to-metal charge transfer (LMCT) O2−/− → Eu3+/2+ state in Eu-doped oxides. In this sense, Eu-doped Y2O3 and Y4Zr3O12 characterization is also presented. Features in the absorption spectra of these materials confirm the presence of Ce4+, Pr4+ and Tb4+, and the photoluminescent spectra their respective trivalent oxidation states. To demonstrate the contribution of multiple LMCT O2−/− → Ln4+/3+ states to the absorption spectra of compounds, Gaussian deconvolutions were performed. Maxima of Gaussian peak profiles were guessed from a vacuum referred binding energy diagram. The initial state for each LMCT O2−/− → Ln4+/3+ is always the top of the valence band, while the final ones correspond to some Ln3+ f state. Additional required peaks to reach adequate fittings were assigned to IVCT Ln3+/4+ and f-d Ln3+ states.

Control of Eu Oxidation State in Y2O3-xSx:Eu Thin-Film Phosphors Prepared by Atomic Layer Deposition: A Structural and Photoluminescence Study.

Structural and photoluminescence studies were carried out on Eu-doped Y2O3−xSx thin films grown by atomic layer deposition at 300 °C. (CH3Cp)3Y, H2O, and H2S were used as yttrium, oxygen, and sulfur precursors, respectively, while Eu(thd)3 was used as the europium precursor. The Eu oxidation state was controlled during the growth process by following the Eu(thd)3 pulse with either a H2S or O3 pulse. The Eu(thd)3/O3 pulse sequence led to photoluminescence emission above 550 nm, whereas the Eu(thd)3/H2S pulse sequence resulted in emission below 500 nm.

Flame synthesis of nanophosphors using sub-micron aerosols

A flame synthesis approach is described for producing metal oxide nanoparticles. It is based on a novel microjet atomisation technique, which generates solution aerosol droplets in the sub-micron range with a mean diameter of 200 nm. Here, luminescent Eu-doped Y2O3 nanophosphors are successfully synthesised from aqueous metal nitrate precursors delivered to non-premixed CH4/N2-O2 flames. The effect of droplet size and synthesis temperature on the particle formation route is experimentally investigated by comparison with micron-size droplets (mean diameter 3.5 µm) produced by ultrasonic atomisation. Depending on the synthesis temperature, the results show that particles are formed via two different mechanisms: gas-to-particle and droplet-to-particle. Using sub-micron droplets at low temperatures (1150 K), the latter mechanism allows production of luminescent Y2O3:Eu3+ nanoparticles in the cubic phase, with straightforward particle size control from 10 to 100 nm by adjusting the precursor concentration in the 0.01–1 mol/L range. At higher flame temperatures (2750 K), results show that nanoparticles are formed via the gas-to-particle mechanism and have a size of 4–5 nm. In comparison with micron-size droplets, specific surface area measurements of the product powders show that sub-micron droplets form an increased fraction of nanoparticles via the gas-to-particle route. The greater developed surface area of sub-micron droplets enhances vaporisation of metal precursor molecules into the gas phase. Timescale analysis shows that the relative rates of solvent evaporation and bulk solute diffusion are also dependent on the droplet size. Electron microscopy confirms that dense particles are formed from sub-micron droplets subjected to a rapid rate of temperature increase in the flame. For the same synthesis conditions, micron-size droplets tend to form hollow particles, indicating that high peak temperatures near the product melting point (>2700 K) are subsequently required to promote dense particle formation.

Eu3+ ions imminence impact on its photoluminescence in Y2O3 host

A systematic photoluminescence study on 2% Eu-doped Y2O3 particles has been carried out. It is observed that 1300°C annealed samples show higher non-radiative contributions, poor lifetime and quantum efficiency in comparison to the samples annealed at lower temperatures (700°C and 900°C), even though the structural symmetry and emission profile remains almost unaffected by the increasing annealing temperature. Based on empirical exploration it has been established that annealing at 1300°C, reduces the average distance between Eu ions to ~6.7Å on. Odd behavior of 1300°C heated Y2O3:Eu sample has been attributed to the decreased interatomic separation i.e. increased proximity and associated increase in interaction between Eu ions. The inferences has been further supported by luminescence investigation of Y2O3 sampled co-doped with Yb–Er.

Optical excitation and external photoluminescence quantum efficiency of Eu³⁺ in GaN.

We investigate photoluminescence of Eu-related emission in a GaN host consisting of thin layers grown by organometallic vapor-phase epitaxy. By comparing it with a reference sample of Eu-doped Y2O3, we find that the fraction of Eu3+ ions that can emit light upon optical excitation is of the order of 1%. We also measure the quantum yield of the Eu-related photoluminescence and find this to reach (~10%) and (~3%) under continuous wave and pulsed excitation, respectively.

A fluorescent probe for detecting thiamine using the luminescence intensity of nanoparticles.

Determination of molecules and biomolecules using nanoparticles is promising in the development of analytical techniques. Modified Eu-doped Y2O3 nanoparticles (Y2O3:Eu NPs) by captopril have been used as a probe for thiamine (vitamin B1) determination. According to the fluorescence enhancement of modified Eu-doped Y2O3 nanoparticles caused by thiamine, a simple and sensitive method were proposed for its detection. The increase in modified Y2O3:Eu NPs fluorescence signal as a function of thiamine concentration was found to be linear in the concentration range of 0-44 μM. The limit of detection (LOD) of thiamine by this method was 0.144 μM. All the measurements were performed in natural pH, at the room temperature under ambient conditions. Possible interaction mechanism was discussed.

Red emitting Y2O3:Eu3+nanophosphors with >80% down conversion efficiency

Obtaining nanophosphors of a controlled size and shape with a high quantum efficiency is the current challenge for display and imaging technologies. Although the surface state induced luminescence quenching in nanophosphors may be compensated to some extent by incorporating activators like rare-earth ions, or by exploiting their quantum size effect, obtaining nanophosphors with quantum efficiencies as high as their bulk counterparts remains elusive. In the present article, we report on the synthesis of uniform Eu-doped Y2O3 nanoparticles, with an average size of 20–53 nm and a down conversion efficiency as high as 85%, using a simple chemical precipitation technique. Along with size control, the effects of Eu3+ content on their emission behaviors have been discussed. We believe the low-cost synthesis process of these nanoparticles will greatly enhance their application potential in optical display and bio-imaging technologies.

Preparation and optical properties of Eu-doped Y2O3–Al2O3–SiO2 glass

Eu-doped Y2O3–Al2O3–SiO2 (YAS) glass with good transparency from ultraviolet to infrared region was prepared by furnace-cooling with a cooling rate (<0.5°C/s) much lower than those (>102°C/s) in conventional quenching approaches. The bulk density of Eu-doped YAS glass increased with increasing concentration of Eu2O3 and showed a linear dependence on the latter. Under ultraviolet excitations, the Eu-doped YAS glasses exhibited characteristic orange emissions of Eu3+ and the maximum emission intensity was obtained with Eu/(Y+Eu)=0.09. Under excitation at 363nm, a broad emission peak in violet-blue region was also observed, which was assigned to 4f–5d transitions of Eu2+.

Nanosized Thermosensors for Use in Explosions

ABSTRACTNanophase Eu-doped Y2(CO3)3 and Eu-doped Zr(OH)4 are seeded into explosive fireballs to record the temperatures inside the fireball. The heat from the explosion decomposes the materials and converts them into Eu-doped Y2O3 and Eu-doped ZrO2, respectively. The optical signatures of these materials are compared with those of samples heated in a pyroprobe. By comparing the full-width half-max (FWHM) of the excitation peak of Eu-doped Y2(CO3)3 or comparing the ratio of two fluorescence peaks and the peak position of Eu-doped Zr(OH)4, we are able to deduce the temperatures inside the explosive fireball.

Structural and luminescent characteristics of pulsed laser deposited Eu3+-doped Y2O3 thin films

Thin films of Eu-doped Y2O3 were deposited using the pulsed laser ablation technique on amorphous fused silica substrates. The effect of oxygen partial pressure (pO2) and substrate temperature on the structural and optical characteristics of the deposited films were investigated. All the deposited films were crystalline, showing preferred orientation along the (111) plane, irrespective of oxygen partial pressure and substrate temperature. The film deposited at 0.005 mbar pO2 exhibited better crystallinity with minimum FWHM at a substrate temperature of 600°C. All the films deposited at various substrate temperatures and different partial pressure (at 600°C) exhibited a red luminescence peak at 615 nm corresponding to the 5D0–7F1 transition in Eu3+. Photoluminescence excitation spectra exhibited two bands, one corresponding to band to band excitation (212 nm) of the host and the other to charge transfer band excitation (245 nm). A microstructure analysis revealed that surface roughness of the as-deposited films increases with increase in oxygen partial pressure.

Transmission Electron Microscopy Study of Eu-Doped Y&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt; Nanosheets and Nanotubes

A hydrothermal method was used to synthesize Eu-doped Y2O3 nanosheets and nanotubes. High Resolution transmission electron microscopy (HRTEM) and synchrotron x-ray diffraction were used to characterize these nanomaterials. The nanosheets were obtained using a slightly lower pH value and they were partly crystalline and partly amorphous. Using a pH value of about 10, fully crystalline nanotubes were obtained. It is anticipated that nanosheets folded themselves to form stable nanotubes.

Synthesis of Nano-Sized Oxide Phosphor Particles Using an Ion-Exchange Polymer/Water/Oil Emulsion Method

We synthesized nano-sized Eu-doped Y2O3 (Y2O3:Eu) phosphor powder by an ion-exchange po-lymer/water/oil (W/O) emulsion method using carboxymethyl cellulose (CMC) as the ion-exchange polymer, in which the CMC-(Y, Eu) gel formed was calcined at 800°C in air to convert into Y2O3:Eu particles. The obtained phosphor powder consists of unagglomerated particles with sizes in the range of 30-80 nm and exhibits strong red emission at 612 nm. This CMC/W/O method for producing nano-sized oxide powder has significant advantages over conventional solid-phase and chemical solution-based methods because this method can provide unagglomerated nanoparticles of oxide phosphor without employing any mechanical pulverizing process for reducing the particles’ size into the nanometer range; mechanical grinding, such as ball milling, of phosphor powders has been well known to cause a significant degradation of their luminescent properties.

High-pressure induced phase transitions of Y2O3 and Y2O3:Eu3+

We investigated high-pressure induced phase transitions in Y2O3 and Eu-doped Y2O3 (Y2O:Eu3+) using angular dispersive synchrotron x-ray diffraction, Raman spectroscopy, and photoluminescence (PL). With increasing pressure, we observed a series of phase transformations in Y2O3:Eu3+, which followed a structure sequence of cubic→monoclinic→hexagonal, while Y2O3 followed a sequence of cubic→hexagonal. During decompression, both hexagonal structured Y2O3 and Y2O3:Eu3+ transformed into monoclinic phases which were quenchable back to ambient pressure. Raman and PL measurements shed additional light on the different phase transition behavior in these two samples.

Synthesis of Nanocrystalline Y2O3:Eu Phosphor by a Metal-Ionic CrossLinker-Containing Polymeric Precursor Method

We synthesized a high-performance red-emitting nano-sized Eu-doped Y2O3 phosphor (Y2O3:Eu) powder by a metal-ionic crosslinker-containing polymeric method using carboxymethyl cellulose (CMC), with post heat treatment at 1000°C in air. This method yields soft but large aggregates of nanocrystalline Y2O3:Eu particles as synthesized, and therefore, to obtain the phosphor powder consisting of nano-sized single grains pulverization of the aggregates by ball milling or other methods is needed; this pulverizing process generally causes a deterioration of the fluorescence of Y2O3:Eu powders. To solve this problem we established a new method to obtain nano-sized Y2O3:Eu powders without mechanical pulverization by using ∅50-μm yttria-stabilized zirconia balls, which were added in a reaction vessel as an aggregation suppressant. By this method high-performance red-emitting Y2O3:Eu powders with grain sizes of 20–30 nm were successfully produced.

Distribution of Eu3+ Dopant Ions in C3i and C2 Sites of the Nanocrystalline Sc2O3:Eu Phosphor

The actual occupancy of the two available cation sites by luminescent Eu3+ ions, in the cubic bixbyite-type structure of nanocrystalline sesquioxides, has been investigated by 151Eu Mössbauer spectroscopy and magnetic susceptibility measurements. It was found that one fourth of the europium ions is in the more symmetric site C 3i and three fourths in the less symmetric site C 2; the distribution is random. In the series of the Eu-doped sesquioxides Sc2O3, Lu2O3, Y2O3 and Eu2O3, the covalency of the Eu-O bond and the Eu site distortion increase with the difference in ionic radii between europium and the cation of the host compound. The magnetic susceptibility has been analyzed as sum of the contributions of the free Eu3+ ion, of the crystal-field effect and of the exchange interaction between europium ions.

Synthesis and magnetic characterizations of manganite-based composite nanoparticles for biomedical applications

We report chemically synthesized highly crystalline lanthanum strontium manganite (LaSrMnO3) and Eu-doped Y2O3 and their composites. The synthesis yields nanoparticles of size 30–40nm. Magnetic measurements performed on nanoparticles and composites show magnetic transition at about 370K with a superparamagnetic behavior at room temperature. The ferromagnetic resonance studies of the nanoparticles show large linewidth due to surface strains. The composite nanoparticles also display luminescent behavior when irradiated with ultraviolet light. The manganites as well their composite with the luminescent nanoparticles may be very useful for biomedical applications.