Synthesis and luminescence properties of oxyapatite NaY9Si6O26 doped with Eu3+, Tb3+, Dy3+ and Pb2+

Oxyapatite NaY9Si6O26 was prepared by sol-gel method. By choosing the precursors, a single phase compound was obtained. This soft chemical method lowered the reaction temperature by 100degreesC compared with the solid state method. Its morphology was studied by transmission electron microscopy (TEM). Several rare earth ions (Eu3+, Tb3+, Dy3+) and Pb2+ ion were doped in this compound. The high resolution emission spectrum of Eu3+ showed that rare earth ions occupied two yttrium sites. In spite of the charge imbalance of Pb2+ with the cations in this compound, it was found that Pb2+ could emit in UV range and transfer its excitation energy to Dy3+ ion.

VUV excited luminescence of europium activated calcium borophosphate prepared in air

XAFS (EXAFS and XANES) at Eu-L-3 edge were used to determine the local structure and the valences of europium in CaBPO5:Eu prepared in air. The results of EXAFS showed that the doped europium atoms were nine-coordinated by oxygen atoms and the distances of bond Eu-O were 2.39 Angstrom in the host lattice. XANES at Eu-L-3 edge exhibited that Eu2+ and Eu3+ coexisted in the matrix. The luminescent spectrum of the material excited by VUV at 147 nm presented a similar spectrum with that excited by f-f transition of Eu2+ at 396 nm and f-d transition of Eu2+ at 312 nm. The broad emission band due to both 4f(6)5d - 4f(7) transition of EU2+ and f - f transition of Eu3+ could be observed in emission spectra, which indicated that the trivalent europium ions were reduced in air in the matrix at high temperature by the defects [V-Cn]" formed by aliovalent substitution between Ca2+ and Eu3+ ions. The UV excitation spectrum showed the typical f-f transition of Eu3+ and f-d transition of Eu2+. The bands with the maxima at about 113 and 158 nm in VUV excitation spectrum were assigned to originate from the absorption of the host lattice.

Preparation, patterning and luminescence properties of rare earth-doped YVO4 nanocrystalline phosphor films via sol-gel soft lithography

In this presentation, nanocrystalline YVO4:A (A=Eu3+, Dy3+, SM3+, Er3+) phosphor films and their patterning were fabricated by a Pechini sol-gel process combined with a soft lithography (micro-molding in capillaries). XRD, FT-IR, AFM and optical microscope, absorption spectra, photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 400 degrees C and the crystallinity increased with the increase of annealing temperatures. Transparent nonpattemed phosphor films were uniform and crack free, which mainly consisted of grains with an average size of 90nm. Patterned crystalline phosphor film bands with different widths (5-30 mu m) were obtained. The doped rare earth ions (A) showed their characteristic emission in crystalline YVO4 phosphor films due to an efficient energy transfer from vanadate groups to them. The Sm3+ and Er3+ ions also showed upconversion luminescence in YVO4 film host. The optimum concentration for Eu3+ was determined to be 7 mol% and those for Dy3+, Sm3+, Er3+ were 2 Mol% of Y3+ in YVO4 films, respectively.

Sol-gel preparation and luminescence properties of nano-structured hybrid materials incorporated with europium complexes

Microporous silica gel has been prepared by the sol-gel method utilizing the hydrolysis and polycondensation of tetraethylorthosilicate (TEOS). The gel has been doped with the luminescent ternary europium complex Eu(TTA)(3)(.)phen: where HTTA=1-(2-thenoyl)-3,3,3-trifluoracetone and phen=1,10-phenanthroline. By contrast to the weak f-f electron absorption bands of Eu3+, the complex organic ligand exhibits intense near ultraviolet absorption. Energy transfer from the ligand to Eu3+ enables the production of efficient, sharp visible luminescence from this material. Utilizing the polymerization of methyl methacrylate, the inorganic/polymer hybrid material containing Eu(TTA)(3)(.)phen has also been obtained. SEM micrographs show uniformly dispersed particles in the nanometre range. The characteristic luminescence spectral features of europium ions are present in the emission spectra of the hybrid material doped with Eu(TTA)(3)(.)phen.

Preparation and luminescence properties of ormosil material doped with Eu(TTA)(3)phen complex

The europium complex, Eu(TTA)(3)phen (TTA = thenoyltrifluoroacetone, phen = 1,10-phenanthroline) was successfully doped into organically modified silicate (ormosil) matrix-SiO2/(VTMOS+PMMA) (VTMOS = vinyltrimethoxysilane, PMMA = polymethylmethacrylate) via sol-gel process, and the luminescence properties of the resultant ormosil composite phosphors [ormosil: Eu(TTA)(3)phen were investigated compared with those of the pure Eu(TTA)(3)phen complex powder. The ormosil composite materials incorporated with Eu(TTA)(3)phen show the characteristic red emission of Eu3+ ion. The Eu3+ possesses fewer emission lines and longer lifetime in the hybrid phosphor than in the pure Eu(TTA)(3)phen complex. This has been explained from the viewpoint of the surrounding environment where the Eu3+ ion lies. (C) 2000 Elsevier Science B.V. All rights reserved.

Luminescence properties of Eu(phen)(2)Cl-3 doped in sol-gel-derived SiO2-PEG matrix

Rare earth complex Eu(phen)(2)Cl-3 was introduced into a SiO2-PEG-400 hybrid material by a sol-ger method. The result indicated that Poly(ethylene glycol) (PEG) could associate with Eu3+ and change the surroundings of Eu3+ in the hybrid material, greatly improving the decay time. Transparent SiO2-PEG400 hybrid doped with a very small amount of Eu(phen)(2)Cl-3 has better mechanical properties and can retain excellent luminescence properties of the rare earth complex. (C) 2000 Elsevier Science B.V. All rights reserved.

Preparation and luminescence properties of sol-gel hybrid materials incorporated with europium complexes

Microporous silica gel has been prepared by the sol-gel method utilizing the hydrolysis and polycondensation of tetraethylorthosilicate (TEOS). The gel has been doped with the luminescent ternary europium complex Eu(TTA)(3). phen: where HTTA = 1-(2-thenoyl)-3,3,3-trifluoracetone and phen = 1,10-phenanthroline. By contrast to the weak f-f electron absorption bands of Eu3+, the complex organic ligand exhibits intense near ultraviolet absorption. Energy transfer from the ligand to Eu3+ enables the production of efficient, sharp visible luminescence from this material. Utilizing the polymerization of methyl methacrylate or ethyl methacrylate, the inorganic/polymer hybrid materials containing Eu(TTA)(3). phen have also been obtained. SEM micrographs show uniformly dispersed particles in the nanometre range. The characteristic luminescence spectral features of europium ions are present in the emission spectra of the hybrid material doped with Eu(TTA)3 phen. (C) 2000 Kluwer Academic Publishers.

Displacement and luminescence of Eu3+ in CaYBO4

CaY1-xBO4: xEu was synthesied by solid state reaction method, and the displacement and luminescence of the Eu3+ in CaYBO4 host were studied. Two luminescent centers could be observed at certain Eu3+-concentration, indicating that the Eu3+ occupies two different crystallographic sites. This result shows that the Eu3+ occupies two different Y3+ sites in CaYBO4. The investigation on Eu-O charge transfer bands indicates that the larger distortion or the lower symmetry of Eu3+ site is,the shorter wavelength of the Eu-O charge transfer band is. When the Eu3+-concentration is high (x > 0.10), Eu3+ occupies the sites of Ca2+ and is reduced to Eu2+.

Luminescence centers and valence change of Eu2+ in KCaF3

The nature of the emission centers and the valence change of Eu2+ in KCaF3:Eu2+ depends strongly on preparation conditions. Experimental results show that there are two different d-->f emission bands, located at 425 and 510 nm, respectively. Their origin, relationship, and the effect of doping concentration on them are discussed. A Eu2+-Eu3+ valence change process is proposed. (C) 2000 Elsevier Science Ltd. All rights reserved.