Ivan G.N. Silva

Low Temperature Synthesis of Luminescent RE2O3:Eu3+ Nanomaterials Using Trimellitic Acid Precursors

[RE(TLA)·(H2O)n:Eu3+] (RE3+: Y, Gd and Lu; TLA: trimellitic acid) precursor complexes were synthesized by an one step aqueous co-precipitation method. After annealing for 1 h, RE2O3:Eu3+ nanophosphors were formed through the benzenetricarboxylate low temperature thermolysis method (500-1000 oC). The compounds were characterized by using different techniques [elemental analysis (CHN), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG/DTG), X-ray powder diffraction (XPD) and scanning electron microscope (SEM)]. The XPD data indicated that the Y2O3:Eu3+ materials have crystallite size range from 11 to 62 nm. The SEM and transmission electron microscopy (TEM) images show that the annealed materials keep morphological similarities with the precursor complexes. The photoluminescence properties were studied based on the excitation and emission spectra, and luminescence decay lifetimes of the 5D0 emitting level of the Eu3+ ion. The experimental intensity parameters (Ωλ), lifetimes (τ), as well as radiative (Arad) and non-radiative (Anrad) decay rates were calculated and discussed. The RE2O3:Eu3+ phosphors (RE: Y3+ and Lu3+) annealed at 500 to 1000 oC have emission quantum efficiency (intrinsic quantum yield) values from 60 to 82%, indicating that this material can be potentially used for optical markers applications.

Red (Eu3+), Green (Tb3+) and Ultraviolet (Gd3+) Emitting Nitrilotriacetate Complexes Prepared by One-step Synthesis

The [RE(NTA)(H2O)2]⋅(H2O) rare-earth complexes (RE3+: 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 photoluminescence behavior was studied based on the excitation and emission spectra, and luminescence decay curves. The compounds exhibit red (Eu3+), green (Tb3+) and UV (Gd3+) monochromatic emissions under UV excitation. The NTA ligand acts as luminescence sensitizer in the ligand-to- RE3+ intramolecular energy transfer process, owing to the fact that the first excited triplet state (T1: 29 000 cm−1) is located above of the 5D0 (Eu3+) and 5D4 (Tb3+) emitting levels. The experimental intensity parameters Ωλ (λ: 2 and 4) for the Eu3+ NTA complex were calculated, and the results are discussed. The Gd3+-NTA complex exhibits a high-intensity emission band in the UV region (32 000 cm−1) assigned to the 6P7/2→8S7/2 intraconfigurational transition. Graphical Abstract Red (Eu3+), Green (Tb3+) and Ultraviolet (Gd3+) Emitting Nitrilotriacetate Complexes Prepared by One-step Synthesis