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Effective Transfer of UV Energy to Red Luminescence in the Nanocomposites Polymer/Eu Coordination Compounds
Abstract
Nanocomposites (NCs) thin films based on oligomer poly-N-epoxypropylcarbazole (PEPC) and organic coordinated compounds (OCC) have been obtained by chemical methods. Absorption threshold for samples with different concentrations was determined as 3.34 - 3.4 eV. Photoluminescence spectra reveal a number of emission bands centered at 580, 590, 612-615, 651, and 700 nm, which can be associated to internal 4f - 4f transitions of Eu3+ ion 5D0 → 7Fi (i = 0,1,2,3 and 4). By comparing the photoluminescence spectra of the organic compound and of the PEPC/Eu(o- MBA)3Phen nanocomposite one can observe the amplification of the photoluminescence intensity in NC.
... In this study, the 5 D 0 → 7 F 5 transition (740-770 nm) and the 5 D 0 → 7 F 6 transition (810-840 nm) were not observed because the intensities of these transitions are very low. 60 The ratios of intensities corresponding to 5 D 0 → 7 F 2 and 5 D 0 → 7 F 1 transitions are different for the complexes studied: for DPPOEu(NO 3 ) 3 and PnPPOEu(NO 3 ) 3 they are 6 and 5, respectively, showing deviation from an inversion centre in the complexes. 39 In complexes DPPOEu(TFA) 3 and PnPPOEu(TFA) 3 this ratio is ∼4, indicating that the deviation is not so strong. ...
New phosphinoyl-containing tetradentate heterocycles preorganised for metal ion binding were designed and prepared in high yields. The X-ray structures of two allied phosphinoyl-bearing 2,2'-bipyridyl and phenanthroline ligands, as well as closely related structures of 2,6-bis(diphenylphosphinoyl)pyridine and 9-(diphenylphosphinoyl)-1,10-phenanthroline-2-one, are reported. Complexes of nitrates of several lanthanides and trifluoroacetate of Eu(iii) with two phosphinoyl-bearing 2,2'-bipyridyl and phenanthroline ligands were isolated and characterised. The first structures of lanthanide complexes with phosphinoyl-bearing 2,2'-bipyridyl and phenanthroline ligands are reported. The nature of the counter-ion is crucial for the coordination environment of the metal ion. The photophysical properties of the complexes differring in both the nature of the ligand and counter-ion were investigated. The photophysical properties of the complexes are strongly ligand- and counter-ion-dependent. Absorbance and luminescence excitation spectra of complexes showed main peaks in the UV range which correspond to the absorption of light by the ligand and these are ligand-dependent. Luminescence spectra of complexes show typical europium emission in the red region with a high quantum yield, which corresponds to the transitions (5)D0 → (7)FJ (J = 0-6). The value of deviation of the components of (5)D0 → (7)F2 and (5)D0 → (7)F1 transitions from the inversion centre shows a larger dependence on the counter-ion than on the nature of the ligand. The value of the luminescence quantum yield is larger for europium complexes with 2,2'-bipyridyl-based ligands and NO3 counter-ions than for complexes with phenanthroline-based ligands and NO3 counter-ions. A low dependence of the luminescence lifetime of Eu complexes on the nature of the ligand has been demonstrated: values in the solid state were in the range 1.1-2.0 ms.
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