Rare earth based clusters for nanoscale light source (original) (raw)
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Optical studies of sub-3nm Eu2O3 and Gd2O3:Eu3+ nanocrystals
Journal of Alloys and Compounds, 2009
Colloidally stable sub-3 nm Eu 2 O 3 and Gd 2 O 3 :Eu 3+ nanocrystals have been synthesized via a hot solution phase technique. Optical properties of the nanocrystals are studied as a function of size. Both nanocrystal compositions exhibit a new optical signature, an emission peak at 620 nm. Intensity modulation of this peak has been observed for all nanocrystal sizes, suggesting surface-dependent or crystal-field dependent effect. Photoluminescence intensity of smaller Eu 2 O 3 nanocrystals was comparable to that of the Gd 2 O 3 :Eu 3+ nanocrystals.
Rare-earth-based nanoclusters embedded in sol–gel waveguiding thin films
Journal of Luminescence, 2006
We present a new structural method for clusters analysis based on sol-gel planar waveguides and luminescent nanoparticles of Gd 2 O 3 :Eu 3+ . Clusters are deposited onto a TiO 2 sol-gel layer then covered by a second TiO 2 film. The resulting structure exhibits waveguiding properties.
Quantum confinement effect on Gd2O3 clusters
The Journal of Chemical Physics, 2007
The evolution of the gap of a nanoscaled insulator material, namely, Gd 2 O 3 , has been observed by means of vacuum ultraviolet excitation spectra of a dopant ͑Eu 3+ ͒. The nanoparticles have been synthesized by the low energy cluster beam deposition technique and grown afterward by different annealing steps. A gap shift towards the blue is observed, similar to what is observed in semiconductor nanoparticles. Despite the strong ionic character of the material, the evolution exhibits a behavior similar to covalent materials. The evolution of the gap for Gd 2 O 3 follows the same empiric rule that has been derived for semiconductors ͑ZnO, CuBr, Si, and CdS͒. It shows that, in spite of the strong ionic character of the material ͑0.9 on the scale of Phillips͒, the amount of covalency is important enough for creating a significant delocalization of the electron with regard to its hole.
Radiation Measurements, 2004
This paper reports on the synthesis and characterization of Gd2O3:Eu 3+ nanocrystals of di erent sizes. The particles have been synthesized by a sol-lyophilization process. This methods allows the synthesis of 7-100 nm diameter cubic-phase particles. The photoluminescence properties have been studied with di erent excitation from X-ray to VUV and visible wavelengths. Compared to the properties of the bulk materials, some important changes on the luminescence are observed. In particular some bands are strengthened when the size of the particles is diminished. We could therefore ascribe this bands to doping ions on a site close to the surface. Also a very low e ciency of excitation for small particles is observed when exciting with X-ray or high-energy VUV photons (i.e. when exciting the host matrix) compared to the e ciency obtained when exciting in the charge transfer band or in the doping ions related states.
Morphology- and size-dependent spectroscopic properties of Eu3+-doped Gd2O3 colloidal nanocrystals
Journal of Nanoparticle Research, 2014
The synthesis, morphological characterization, and optical properties of colloidal, Eu(III) doped Gd 2 O 3 nanoparticles with different sizes and shapes are presented. Utilizing wet chemical techniques and various synthesis routes, we were able to obtain spherical, nanodisk, nanotripod, and nanotriangle-like morphology of Gd 2 O 3 :Eu 3? nanoparticles. Various concentrations of Eu 3? ions in the crystal matrix of the nanoparticles were tested in order to establish the levels at which the concentration quenching effect is negligible. Based on the luminescence spectra, luminescence lifetimes and optical parameters, which were calculated using the simplified Judd-Ofelt theory, correlations between the Gd 2 O 3 nanoparticles morphology and Eu 3? ions luminescence were established, and allowed to predict the theoretical maximum quantum efficiency to reach from 61 to 98 %. We have also discussed the impact of the crystal structure of Gd 2 O 3 nanoparticles, as well as coordinating environment of luminescent ions located at the surface, on the emission spectra. With the use of a tunable femtosecond laser system and the Z-scan measurement technique, the values of the effective two-photon absorption cross-section in the wavelength range from 550 to 1,200 nm were also calculated. The nonlinear optical measurements revealed maximum multi-photon absorption in the wavelength range from 600 to 750 nm.
IOP Conference …, 2009
Nanostructured Gd 2 O 3 : Eu 3+ thin films were prepared by pulsed laser ablation technique. The dependence of structural, morphological and optical properties of these films on photoluminescence was systematically studied by varying the Eu 3+ incorporation concentration. Micro-Raman and XRD analysis indicate that Eu 3+ incorporation strongly perturbs the cubic Gd 2 O 3 structure and suppresses the grain growth. For 0.10 mol Eu 3+ doped Gd 2 O 3 films deposited under a vacuum of 10-6 mbar when subjected to annealing at 1173 K give transparent films exhibiting intense photoemission at 612 nm due to 5 D 0-7 F 2 transition. The Eu 3+ incorporation concentration above 10 mol %, decreased the luminance intensity may be due to concentration quenching effect.
Tuning of photoluminescence emission properties of Eu3+ doped Gd2O3 by different excitations
Optik, 2017
In this work, we investigated cubical particles of europium doped gadolinium oxide based material for colour tuning by different excitations. Structural properties of the material were studied by transmission electron microscopy and X-ray diffraction analysis. The Photoluminescence (PL) technique was used to study luminescent properties of the material and its optical features were thoroughly investigated by calculating CIE chromaticity. Effect of Eu 3+ concentration on emission spectra for three excitations was also recorded. The emission intensity for 613 nm, 584 nm and 467 nm were recorded as the function of dopant ion concentration. It was observed that the blue emission quenched at 1 mol% Eu 3+ whereas red and green quenched after 2 mol% of Eu 3+ .
Journal of Applied Physics, 2008
Nanoparticles of GdVO 4 doped with Eu 3+ and core/shell of GdVO 4 :Eu 3+ / GdVO 4 are prepared by urea hydrolysis method using ethylene glycol as capping agent as well as reaction medium at 130°C. Unit cell volume increases when GdVO 4 is doped with Eu 3+ indicating the substitution of Gd 3+ lattice sites by Eu 3+. From luminescence study, it is confirmed that there is no particle size effect on emission positions of Eu 3+. Optimum luminescence intensity is found to be in 5-10 at. % Eu 3+. Above these concentrations, luminescence intensity decreases due to concentration quenching effect. There is an enhancement in luminescence intensity of core/shell nanoparticles. This has been attributed to the reduction in surface inhomogenities of Eu 3+ surroundings by bonding to GdVO 4 shell. The lifetime for 5 D 0 level increases with annealing and core/shell formation.
Spherical and rod-like Gd 2 O 3 :Eu 3 + nanophosphors—Structural and luminescent properties
Bulletin of Materials Science, 2012
A comparative study of spherical and rod-like nanocrystalline Gd 2 O 3 :Eu 3+ (Gd 1•92 Eu 0•08 O 3) red phosphors prepared by solution combustion and hydrothermal methods have been reported. Powder X-ray diffraction (PXRD) results confirm the as-formed product in combustion method showing mixed phase of monoclinic and cubic of Gd 2 O 3 :Eu 3+. Upon calcinations at 800 • C for 3 h, dominant cubic phase was achieved. The as-formed precursor hydrothermal product shows hexagonal Gd(OH) 3 :Eu 3+ phase and it converts to pure cubic phase of Gd 2 O 3 :Eu 3+ on calcination at 600 • C for 3 h. TEM micrographs of hydrothermally prepared cubic Gd 2 O 3 :Eu 3+ phase shows nanorods with a diameter of 15 nm and length varying from 50 to 150 nm, whereas combustion product shows the particles to be of irregular shape, with different sizes in the range 50-250 nm. Dominant red emission (612 nm) was observed in cubic Gd 2 O 3 :Eu 3+ which has been assigned to 5 D 0 → 7 F 2 transition. However, in hexagonal Gd(OH) 3 :Eu 3+ , emission peaks at 614 and 621 nm were observed. The strong red emission of cubic Gd 2 O 3 :Eu 3+ nanophosphors by hydrothermal method are promising for high performance display materials. The variation in optical energy bandgap (E g) was noticed in as-formed and heat treated systems in both the techniques. This is due to more ordered structure in heat treated samples and reduction in structural defects.
Journal of Materials Engineering and Performance, 2018
A facile direct precipitation method was used for the synthesis of luminescence nanomaterial. Gd 2 O 3 doped with rare earth element Eu 3+ is synthesized by polyol route. The synthesized nanoparticles show their characteristic red emission. The nanoparticles are characterized by x-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and photoluminescence (PL) study. The synthesized nanoparticles are spherical particles with $ 30 nm size. The photoluminescence studies show the characteristic Eu 3+ red emission. The PL study shows the intensity of the magnetic dipole transition (5 D 0 ! 7 F 1) at 592 nm compared to that of the electronic dipole transition (5 D 0 ! 7 F 2) at 615 nm. The nanomaterials can show significant application in various display devices and biomedical applications for tracking.