Publicação: Luminescence and non-radiative processes in lanthanide squarate hydrates
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The luminescence properties of solid hydrated lanthanide squarates (Ln2(C4O4)3(H2O) x; x = 8 or 13;Ln3+ = Gd, La, Eu, Tb, Pr) are reported for temperatures down to 4.2K. The luminescence of the squarate group is observed for the Gd3+ and La3+ compounds at low temperatures (below 150K). The Pr3+ compound does not show any emission at all, not even at 4.2K. This is ascribed to the quenching of the Pr3+ emission by multiphonon relaxation and/or concentration quenching. The quantum efficiencies of the 5D0 emission of Eu3+ and of the 5D4 emission of Tb3+ in these squarate complexes are strikingly different. Whereas the Tb3+ emission shows a temperature independent quantum efficiency of 50% upon ligand excitation, the Eu3+ emission is strongly quenched, showing a temperature dependent quantum efficiency of 0.8% at 4.2K upon ligand excitation. This quenching is ascribed to the low energy position of the charge-transfer state of Eu3+ in these compounds.
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A. inorganic compounds, D. luminescence, D. optical properties, Charge transfer, Hydrates, Ions, Luminescence, Optical properties, Quantum efficiency, Quenching, Concentration quenching, Lanthanide squarate hydrates, Ligand excitation, Multiphonon relaxation, Nonradiative processes, Rare earth compounds
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Inglês
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Journal of Physics and Chemistry of Solids, v. 57, n. 11, p. 1727-1734, 1996.
