The effect of EU3+ ion doping concentration in Gd2O3 fine spherical particles

This work reports on the preparation of Gd2O3, cubic system, with spherical particles, narrow size distribution, whether or not doped with 1-5 at.% of Eu3+ and the influence of Eu3+ concentration on optical and morphological properties. Average diameter and size distribution particle analyses were performed for all samples from SEM results. Doped samples were also investigated by luminescence spectroscopy and emission kinetic measurements. All oxide samples present a particle average diameter distribution range from 110 to 150 nm and a decrease of particle average diameter with the presence of Eu3+. The particle size decrease is almost the same for all samples with different doping ion concentration. Therefore, the presence of doping ion may be inhibiting particle growth after the nucleation process. From spectroscopic studies, the doping ion distribution in the surface of oxide samples can be considered homogeneous because concentration quenching is not observed, as well as a significant difference among the calculated lifetime for each sample. (C) 2002 Elsevier B.V. B.V. All rights reserved.

The crystal field strength parameter and the maximum splitting of the 7F1 manifold of the Eu3+ ion in oxides

We examine, from both the experimental and theoretical point of view, the behavior of the maximum splitting ��E, of the 7F1 manifold of the Eu3+ ion as a function of the so-called crystal field strength parameter, Nv, in a series of oxides. In connection with the original theory that describes the relation between ��E and Nv, a more consistent procedure to describe this relation is presented for the cases of small total angular momentum J. Good agreement is found between theory and experiment. �� 1995.

Estudo do comportamento t��rmico e da luminesc��ncia de filmes de quitosana com os ��ons Eu3+ e Tb3+

Films of chitosan with trivalent lanthanides ions Eu3+ and Tb3+ were respectively prepared in the ratio of 3:1 m/m (chitosan: lanthanide) and 6:1 m/m (chitosan: lanthanide). There were no formations of films in a ratio of 1:1 m/m (chitosan: lanthanides). The films of chitosan with the Tb3+ ion have the same transparent appearance than the pure chitosan films. The film of chitosan with Eu3+ ion has a muddy appearance. These films present good resistance to tear. The appearance of the compounds prepared in ratio 1:1m/m is a white powder. The films and compounds of chitosan were characterized by Elementary Analysis (CHN), Thermal Analysis (TG/DTG) and Spectroscopy of Luminescence. The CHN analysis was made only for compounds prepared in ratio 1:1m/m, suggesting that these compounds possess the formula QUILn.6H2O, where QUI = Chitosan and Ln = Lanthanide. The results of the curves TG/DTG indicated that there are strong interactions between Eu3+ or Tb3+ and chitosan, causing a lesser lost of mass in the films. The luminescence analysis showed that the films of chitosan with the ions Eu3+ and Tb3+ present emissions in the region of the visible one, with bands of the chitosan and of the Eu3+ ion. The luminescence analysis of the compounds of chitosan with the Eu3+ and Tb3+ ions suggest that the chitosan does not transfer into energy to the ions lanthanides, however the chemical neighborhood around of the ion lanthanides breaks the selection rules and, conseq��ently the 4f-4f transitions of the lanthanide ions are observed

The role of the Eu3+ ions in structure and photoluminescence properties of SrBi2Nb2O9 powders

Conselho Nacional de Desenvolvimento Cient��fico e Tecnol��gico (CNPq)

Enhanced Eu3+ Emission in Aqueous Phosphotungstate Colloidal Systems: Stabilization of Polyoxometalate Nanostructures

Luminescent Eu3+-containing polyphosphate tungstate aqueous colloidal systems were prgared and studied as a function of the relative polyphosphate tungstate content. In polyphosphate-rich solutions, Eu-H- ions occupy cagelike sites composed of phosphate groups from the metaphosphate chains. In these sites, an average number of 0.5 water molecule coordinates to an Eu3+ ion and the 500 emission quantum efficiency is 0.22. Tungstatc addition leads to important modifications in neighboring Eu3+ leading to coordination sites in the aqueous medium where metal ions are completely hidden from interactions with solvent molecules. Transmission electron microscopy results clearly show \V-rich nanoparticles with sizes between 5 and 10 nm for all tungstate relative concentrations. For high tungstatc relative contents (above 30 mol %), spectroscopic results suggest the presence of Eu34- in polyoxometalate (P0M)-like sites by comparison with the well-known decatungstoeuropate [EuW10O36](9-) structure. These new aqueous colloids display surprisingly high 5llo emission quantum efficiencies of ca 80% because of the strong ligand field provided by tungstate POM ligands and the complete absence of water molecules from the Eu3+ first coordination shell.

Structural and optical properties of Eu3+ and Mg2+ doped LiTaO3 obtained via the polymeric precursor method

This work reports on the pure lithium tantalate (LiTaO3), europium (III)-doped LiTaO3 and magnesium (II)-europium (III)-doped LiTaO3 preparared by the polymeric precursor method, using four different powered samples of Eu3+ ion concentrations 0.1 to 1at %. Structural and optical properties of powders have been studied. The different possible sites occupied by the rare earth were examined. The phase contents and lattice parameters were studied by the Rietveld method and the structural disorder in the LiTaO3 host caused by Eu3+ ions was analyzed. Results indicated LiTaO3 free of secondary phases at 650��C and the photoluminescence (PL) emission spectra showed the characteristic sharp emission bands given by Eu3+ ions when they are excited at a wavelength of 399 nm. An increase of dopants contents caused a non-homogeneous broadening and showed a slightly larger one when Mg was added. A displacement of the transition 5D0-7F0 to shorter wavelengths as function of Eu3+ concentration was also noticed.

Spherical-shaped Y2O3:Eu3+ nanoparticles with intense photoluminescence emission

Conselho Nacional de Desenvolvimento Cient��fico e Tecnol��gico (CNPq)

Tb3+-> Eu3+ Energy Transfer in Mixed-Lanthanide-Organic Frameworks

In this work, we report a theoretical and experimental investigation of the energy transfer mechanism in two isotypical 2D coordination polymers, (infinity)[(Tb1-xEux)(DPA)(HDPA)], where H(2)DPA is pyridine 2,6-dicarboxylic acid and x = 0.05 or 0.50. Emission spectra of (infinity)[(Tb0.95Eu0.05)(DPA)(HDPA)] and (infinity)[(Tb0.5Eu0.5)(DPA)(HDPA)], (I) and (2), show that the high quenching effect on Tb3+ emission caused by Eu3+ ion indicates an efficient Tb3+-> Eu3+ energy transfer (ET). The k(ET) of Tb3+-> Eu3+ ET and rise rates (k(r)) of Eu3+ as a function of temperature for (1) are on the same order of magnitude, indicating that the sensitization of the Eu3+5D0 level is highly fed by ET from the D-5(4) level of Tb3+ ion. The eta(ET) and R-0 values vary in the 67-79% and 7.15 to 7.93 angstrom ranges. Hence, Tb3+ is enabled to transfer efficiently to Eu3+ that can occupy the possible sites at 6.32 and 6.75 angstrom. For (2), the ET processes occur on average with eta(ET) and R-0 of 97% and 31 angstrom, respectively. Consequently, Tb3+ ion is enabled to transfer energy to Eu3+ localized at different layers. The theoretical model developed by Malta was implemented aiming to insert more insights about the dominant mechanisms involved in the ET between lanthanides ions. Calculated single Tb3+-> Eu3+ ETs are three orders of magnitude inferior to those experimentally; however, it can be explained by the theoretical model that does not consider the role of phonon assistance in the Ln(3+)-> Ln(3+) ET processes. In addition, the Tb3+-> Eu3+ ET processes are predominantly governed by dipole-dipole (d-d) and dipole-quadrupole (d-q) mechanisms.

S��ntese, aplica����o e avalia����o da toxicidade aguda de complexo org��nico �� base de eur��pio proposto como marcador fotoluminescente para a Identifica����o de res��duos de tiro

Um complexo de alta fotoluminesc��ncia �� proposto como marcador ��ptico para a identifica����o de res��duos de tiro (GSR). O marcador �� o complexo [Eu(PIC)3(NMK)3], de f��rmula molecular Eu(C6H2N3O7)3.(C7H13NO)3, que apresenta o ��on Eu3+ e os ligantes ��cido p��crico (PIC) e n-metil-��-caprolactama (NMK). Foi realizada a caracteriza����o quimicamente atrav��s de espectroscopia de emiss��o, espectroscopia de infravermelho com transformada de Fourier (FTIR), termogravimetria e an��lise t��rmica diferencial (TG/DTA), e espectrometria de massas com ioniza����o por eletrospray e resson��ncia ciclotr��nica de ��ons por transformada de Fourier (ESI-FT-ICR MS), e, em seguida, foram adicionadas diferentes massas do complexo a muni����es convencionais (de 2 a 50 mg por cartucho). Ap��s os tiros, o GSR marcado foi visualmente e quimicamente detectado por irradia����o UV (�� = 395 nm) e ESI-FT-ICR MS, respectivamente. Os resultados mostraram uma fotoluminesc��ncia eficiente e duradoura, sendo facilmente vis��vel sobre a superf��cie do alvo, no ambiente, no cartucho deflagrado, na arma de fogo, e sobre as m��os e bra��os do atirador quando utilizada massa a partir de 25 mg do marcador em cartuchos .38 e 50 mg em cartuchos .40. Sua toxicidade aguda tamb��m foi avaliada empregando-se o Protocolo 423 da Organiza����o para a Coopera����o e Desenvolvimento Econ��mico (OECD) e apresentou DL50 de 1000 mg.kg-1, sendo classificado como de categoria 4 na escala do Sistema Globalmente Harmonizado de Classifica����o e Rotulagem de Produtos Qu��micos (GHS), considerado, portanto, de m��dia toxicidade. O composto mostrou ser menos t��xico do que os componentes inorg��nicos de muni����es convencionais (em especial o Pb), justificando o seu emprego como marcador de GSR.

Pechini's solution as precursor for Eu(III)-containing ZnO films

The flat-panel-display's (FPD) market and demand for highly efficient and colored luminescent films have been growing quickly. In this work, thin films were obtained from Pechini's solution by dip-coating. The green films were thermally treated at 873 K in order to get ZnO:Eu 1 at% thin film. A Schott(R) glass plate hydrothermally treated was used as substrate. The films have a mosaic shaped feature that was observed by optical microscopy. That feature is a result of substrate thermal treatment. The film deposition decreases the substrate transmittance in the visible range. When the F-7(0) -->L-5(6) (392nm) Eu3+ transition is excited, it is possible to detect emission from D-5(0) --> F-7(J) (J = 1, 2, 3 and 4) transitions. The D-5(0) --> F-7(2) transition is also observed by using ZnO excitation wavelengths indicating energy transfer from ZnO to Eu3+ ion. (C) 2003 Elsevier B.V. (USA). All rights reserved.

Europium(III)-containing zinc oxide from Pechini method

ZnO:Eu3+ (0.1 and 3 at%) with average particle size of 500 nm were prepared by the Pechini method. Photoluminescence spectroscopy evidences that there is no energy transfer between ZnO and Eu3+ ion. The emission spectrum at 77 K shows that Eu3+ ions occupy at least three different sites in ZnO:Eu 3 at% sample. The experimental intensity parameter Omega(2) indicates that Eu3+ ions in the sample doped with 3 at% occupy sites where 4-configurational levels can better mix with opposite-parity states than those in the sample doped with 0.1 at%. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Study of the annealing temperature effect on the structural and luminescent properties of SrWO4:Eu phosphors prepared by a non-hydrolytic sol-gel process

Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)

Synthesis of a functionalized europium complex and deposition of luminescent Langmuir-Blodgett (LB) films

Coordena����o de Aperfei��oamento de Pessoal de N��vel Superior (CAPES)

Synthesis, characterization and spectroscopy of the europium doped lanthanum trimetaphosphate

Orthorhombic modification of europium doped lanthanum trimetaphosphate has been prepared. The compound was obtained by precipitation of rare earth chloride solution with trimetaphosphoric acid. The characterizations were made using X-ray diffractometry, chemical analysis and infrared spectroscopy. Excitation and emission spectra were recorded at liquid nitrogen and room temperatures. Assignments of the 5D0���7FJ (J=0, 1, 2, 3, 4, 5) transitions were made and an unusual high 5D0���7F4 transition intensity with six split lines has been observed. Structural distortion of the crystal lattice may be caused by the Eu3+ ion inclusion. The simple overlap model was applied for the calculation of the total splitting of the 5D0���7F1 transition, the 5D0���7F0/5D 0���7F2 transition intensity ratio and the ���� (��=2.4) intensity parameters. Theoretical predictions showed to be in good accordance with the experimental data. �� 1988 Elsevier Science S.A.

Preparation, characterization and spectroscopy of the europium diphenylphosphinate complex

The purpose of this work is to study the preparation and spectroscopic behavior of the europium diphenylphosphinate complex -Eu(DPP)3. Elemental and thermogravimetric analysis, powder X-ray diffractometry, and infrared spectroscopy were applied to characterize the formula of the final product and the sixfold coordination of the Eu3+ ion. Excitation and emission spectra have been recorded at liquid nitrogen and room temperatures. The 5D0���7F2 transition intensity decreases when T decreases in comparison to the 5D0���7F1 transition intensity. Molecular mechanic calculations were developed in order to obtain the spatial coordinates of the Eu3+ and ligand ions. The simple overlap model was used to calculate the total splitting of the 5D0���7F1 transition, 5D0���7F0/5D 0���7F2 ntensity ratio and the intensity parameters, ���� (��=2 and 4). Good agreements between theoretical predictions and experimental results have been obtained with g=2/3 as the effective charge and ��=0.8��10-24 cm3 as the isotropic polarizability of the oxygen. �� 1998 Elsevier Science S.A.