Hermi Felinto Brito

Persistent luminescence materials Lu2O3:R(3+),M (Pr,Hf(IV); Eu; or Tb,Ca(2+)) were successfully and rapidly (22 min) prepared by microwave-assisted solid-state synthesis (MASS) using a carbon microwave susceptor and H3BO3 as flux. Reaction times are reduced by up to 93% over previous synthetic methods, without special gases application and using a domestic microwave oven. All materials prepared with H3BO3 flux exhibit LuBO3 impurities that were quantified by Rietveld refinement from ...

New complexes with the general formula [RE(TPC)3·(H2O)2], where RE=Eu3+, Sm3+, Gd3+, Tb3+ and TPC=2-thiophenecarboxylate, have been prepared and investigated by photoluminescence spectroscopy. These compounds were characterized by complexometric titration, elemental analyses and infrared spectroscopy. The X-ray crystal structure has been determined for the [Eu(TPC)3·(H2O)2] compound, indicating that this complex is in dimeric form bridged by two carboxylate ions with monoclinic crystal ...

Al2O3:Eu3+(1%) samples were prepared by combustion, ceramic, and Pechini methods annealed from 400 to 1400°C. XRD patterns indicate that samples heated up to 1000°C present disordered character of activated alumina (γ-Al2O3). However, α-Al2O3 phase showed high crystallinity and thermostability at 1200–1400°C. The sample characterizations were also carried out by means of infrared spectroscopy (IR), scanning electron microscopy (SEM) and specific surface areas analysis (BET method). ...

This work presents the preparation of the europium tungstate compound, Eu2(WO4)3, through the use of a polymeric precursor according to the Pechini method. In the preparation of this precursor ammonium tungstate, europium nitrate, edta, citric acid and ethylene glycol were mixed and heated at 700°C for 4h, leading to a luminescent compound. X-ray diffraction, infrared spectroscopy, thermogravimetric analysis and diffuse reflectance spectroscopy were used to characterize the luminescent ...

In the present work the lamellar phases of composition K4Nb6O17, KNb3O8 and KCa2Nb3O10 were used as precursors to prepare new compounds through the potassium exchange reaction with Eu3+ ion via a soft chemistry route. The precursors show absorption bands in the UV range and KNb3O8 exhibits blue emission at room and liquid nitrogen temperature, while K4Nb6O17 presents emission spectra only at low temperature. The aim of this work is to investigate the photoluminescence properties of ...

In this work is reported the sensitization effect by polymer matrices on the photoluminescence properties of diaquatris(thenoyltrifluoroacetonate)europium(III), [Eu(tta)3(H2O)2], doped into poly-β-hydroxybutyrate (PHB) with doping percentage at 1, 3, 5, 7 and 10% (mass) in film form. TGA results indicated that the Eu3+ complex precursor was immobilized in the polymer matrix by the interaction between the Eu3+ complex and the oxygen atoms of the PHB polymer when the rare earth complex was ...

The preparation, characterization and photoluminescent study of Eu3+ ions doped into the RE2(WO4)3 matrix (RE=La and Gd), which was produced by the Pechini method at 750°C are reported. This method is based on polyesterification between citric acid and ethylene glycol, producing a material at low temperature. The X-ray diffraction patterns of the powder materials show the characteristic lines of the rare-earth tungstates. The infrared data are compatible with a Td point group symmetry ...

We report the synthesis, characterization and spectroscopic properties of the compound Eu(thenoyltrifluoroacetonate), 2(dibenzyl sulfoxide) which is highly luminescent under UV excitation. Experimental and theoretical results on ligand field parameters, 4f-4f intensities and intramolecular energy transfer processes are described. The characteristic emission spectrum of the Eu3+ ion shows a very high intensity for the hypersensitive 5D0 → 7F2 transition, pointing to a highly polarizable ...

The persistent luminescence of CdSiO3:Tb3+ was investigated with photoluminescence, thermoluminescence (TL), synchrotron radiation X-ray absorption (XANES and EXAFS) and UV-VUV spectroscopies. Only the typical intraconfigurational 4f8–4f8 transitions of the Tb3+ ion were observed with no traces of band emission in either the conventional UV excited or persistent luminescence spectra. The trap structure from TL with three traps from 0.65 to 0.85 eV is ideal for room-temperature persistent ...

In the present work the layered perovskite phase KCa2Nb3O10 was doped with rare earth ions through a solid-state reaction, producing compounds of general formula K1−xLnxCa2−xNb3O10 (where Ln=La3+ or Eu3+ and x=0.02). The photoluminescence properties of the layered oxide doped with rare earth ions in the perovskite-type layers were investigated based on the luminescence data. The KCa2Nb3O10 phase does not exhibit emission bands when excited in the UV region. On the other hand the matrices ...

In this work, the growth and the characterization of new orange emitting triple-layer electroluminescent organic devices using vacuum deposited trivalent samarium complex [Sm(TTA)3(TPPO)2] as emission layer is described. The electroluminescence (EL) spectra of the devices show narrow bands arising from the 5G5/2→6HJ transitions (J=5/2, 7/2 and 9/2) of the Sm3+ ion with the hypersensitive 5G5/2→6HJ transitions as the prominent group. The hole transporting layer (HTL) was obtained using a ...

Luminescence from trivalent rare earth (R3+: La3+–Lu3+, excluding Pm3+) ions was studied in the CdSiO3 host. The positions of the R2+/3+ energy levels in the band structure of CdSiO3 suggest that the doping of CdSiO3 with R2+ ions is difficult if not impossible. Red, pink, blue, green and close to white persistent luminescence colours were obtained by doping with Pr3+, Sm3+, Gd3+, Tb3+ and Dy3+, respectively. The efficiency of the defect to R3+ energy transfer determines if persistent ...

The R2O3:Eu3+ (R3+: Y, Gd and Lu) nanophosphors were synthesized with a low temperature thermolysis method using rare earth 1,3,5-benzenetricarboxylate (TMA) complexes as precursors. The R(TMA):Eu3+ (1mole %) complexes were synthesized using the co-precipitation method which complexes were then annealed at temperatures from 500 to 1000°C for 1h, yielding the cubic C-type R2O3:Eu3+ materials. The XPD patterns revealed no impurities in C-R2O3 obtained at any temperature. The Scherrer’s ...

It is reported in this work the preparation, characterisation and photoluminescence study of poly(methylmethacrylate) (PMMA) thin films co-doped with [Eu(tta)3(H2O)2] and [Tb(acac)3(H2O)3] complexes. Both the composition and excitation wavelength may be tailored to fine-tune the emission properties of these Ln3+–β-diketonate doped polymer films, exhibiting green and red primary colours, as well as intermediate colours. In addition to the ligand–Ln3+ intramolecular energy transfer, it is ...

Red, blue and green emitting rare earth compounds (RE3+=Eu3+, Gd3+ and Tb3+) containing the benzenetricarboxylate ligands (BTC) [hemimellitic (EMA), trimellitic (TLA) and trimesic (TMA)] were synthesized and characterized by elemental analysis, complexometric titration, X-ray diffraction patterns, thermogravimetric analysis and infrared spectroscopy. The complexes presented the following formula: [RE(EMA)(H2O)2], [RE(TLA)(H2O)4] and [RE(TMA)(H2O)6], except for Tb-TMA compound, which was ...