Enhanced luminescence of Tb(3+) due to efficient energy transfer from Ce(3+) in a nanocrystalline Lu(2)Si(2)O(7) host lattice.

Nanocrystalline lutetium pyrosilicate Lu(2)Si(2)O(7) (LPS) doped with Tb(3+) (LPS:Tb) or Ce(3+)/Tb(3+) (LPS:Ce, Tb) was obtained at 1250 °C by the reaction of nanostructured Lu(2)O(3) and colloidal SiO(2). X-ray diffraction analysis confirmed the crystallization of a single phase of LPS at the indicated temperature. Different concentrations of active ions allowed us to study the influence of Ce(3+) co-doping on Tb(3+) emission. Tb(3+)-doped LPS yields both the blue emission [Formula: see text] (J = 3, 4, 5, 6) and the green emission [Formula: see text] (J = 3, 4, 5, 6) of Tb(3+). The green emission of Tb(3+) is enhanced remarkably in both the cathodoluminescence and photoluminescence spectra because of energy transfer from Ce(3+) to Tb(3+) ions, both of which are present in the host lattice. Based on the optical luminescence and luminescence excitation spectra, the optimal Tb(3+) doping level for maximum light output was established to be 9 mol% and the highest enhancement of Tb(3+) luminescence by Ce(3+) co-doping was detected using a 1:3 ratio of Ce(3+)/Tb(3+) concentration. Two different crystallographic sites of Tb(3+) in the LPS lattice were detected in the luminescence and excitation spectra of samples with higher Tb(3+) concentrations (6-9 mol%). The single-exponential decay profile of (5)D(4) emission for the less concentrated samples and the double-exponential decay for the higher doping level are in agreement with this observation. Calculation of colour coordinates shows that LPS:Ce(0.25%)Tb(3%) emits white light.

Characterization of the electronic excited-state energetics and solution structure of lanthanide(III) complexes with the polypyridine ligand 6,6'-bis[bis(2-pyridylmethyl)aminomethyl]-2,2'-bipyridine.

Absorption, emission, and excitation spectra for solid-state and solution of Tb(III), Dy(III), and Gd(III) complexes with the polypyridine ligand 6,6'-bis[bis(2-pyridylmethyl)-aminomethyl]-2,2'-bipyridine (C36H34N8) are presented. Measurements of excited-state lifetimes and quantum yields in various solvents at room temperature and 77 K are also reported and used to characterize the excited-state energetics of this system. Special attention is given to the characterization of metal-to-ligand energy transfer efficiency and mechanisms. The measurement of circularly polarized luminescence (CPL) from the solution of the Dy(III) complex following circularly polarized excitation confirms the chiral structure of the complexes under study. No CPL is present in the luminescence from the Eu(III) or Tb(III) complex because of efficient racemization. The variation of the magnitude of the CPL as a function of temperature from an aqueous solution of DyL is used for the first time to characterize the solution equilibria between different chiral species.

Effect of ligand radicals on vibrational IR, Raman and vibronic spectra of europium beta-diketonates.

Vibrational IR, Raman spectra and vibronic sidebands of Eu(3+) electronic transitions of europium tris-beta-diketonates Eu(beta)(3).Ph (beta-dipyvaloylmethane (DPM), acetylacetone (AA), benzoylacetone (BA), thenoyltrifluoroacetone (TTFA) and other beta-diketones; Ph-methyl-, phenyl-, and nitro-derivatives of 1,10-phenanthroline (Phen)) as well as Eu(beta)(3).Bpy and Eu(beta)(3).D-Bpy (Bpy- and D-Bpy-H- and D-2,2'-bipyridine) were studied. Effect of ligand radical properties on spectra and manifestation of the reciprocal influence of non-equivalent ligands in spectra are discussed. Dependence of the spectra on electronic density distribution in both ligands as well as on the strength of M-O and M-N bonds at the variation of radicals of one of the ligands, beta or Ph, was examined. Shape of vibronic sidebands was analysed. Behaviour of bands in the middle and far regions of IR spectra of the series Eu(beta)(3).Phen and Eu(TTFA)(3).Ph was investigated. Increase of the polarising influence of Eu(3+) ions on Phen and Bpy molecules and strengthening the Eu-N bonds in TTFA compounds in comparison with DPM compounds were disclosed from the Raman spectra of Eu(beta)(3).Phen and Eu(beta)(3).Bpy, that is in accordance with properties of beta-diketone radicals. Conclusion about weaker Eu-N bonds in europium beta-diketonates with heterocyclic diimines in comparison with corresponding nitrates was derived from the spectra. Spectral data concerning the relative strength of Eu-ligand bonds are in agreement with available X-ray data.