Red (Eu~(3+)), Green (Tb~(3+)) and Ultraviolet (Gd~(3+)) Emitting Nitrilotriacetate Complexes Prepared by One-step Synthesis

摘要

The [RE(NTA)(H_2O)_2?(H_2O) rare-earth complexes (RE~(3+): Eu, Gd, Tb and NTA: nitrilotriacetate) were synthesized and characterized by elemental analysis, thermogravimetry, X-ray diffraction, and infrared spectroscopy. The complexes show high crystallinity and thermostability. The photolumi-nescence behavior was studied based on the excitation and emission spectra, and luminescence decay curves. The compounds exhibit red (Eu~(3+)), green (Tb~(3+)) and UV (Gd~(3+)) monochromatic emissions under UV excitation. The NTA ligand acts as luminescence sensitizer in the ligand-to-RE~(3+) intramolecular energy transfer process, owing to the fact that the first excited triplet state (T_1: 29 000 cm~(-1)) is located above of the ~5D_0 (Eu~(3+)) and ~5D_4 (Tb~(3+)) emitting levels. The experimental intensity parameters Ω_λ (λ: 2 and 4) for the Eu~(3+) NTA complex were calculated, and the results are discussed. The Gd~(3+)-NTA complex exhibits a high-intensity emission band in the UV region (32 000 cm~(-1)) assigned to the ~6P_(7/2) → ~8S_(7/2) intraconfigurational transition.