Microwave-Assisted Sol−Gel Synthesis and Photoluminescence Characterization of LaPO₄:Eu³⁺,Li⁺ Nanophosphors

Abstract

Here, we describe the fast and mass fabrication of monazite lanthanum orthophosphate (LaPO 4 ) nanoparticles via a simple sol-gel method under the assistance of microwave irradiation. The procedure involves formation of homogeneous, transparent, metal-citrate-EDTA gel precursors using both citric acid (CA) and ethylenediamine tetraacetic acid (EDTA) as the complexing agent followed by microwave irradiation, which promotes prompt thermal decomposition of the metal-citrate-EDTA gel precursors to yield the final nanoparticles. Thermogravimetric/differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) were used to characterize the as-synthesized nanoparticles. About 23 g of single monoclinic phase, approximately 100 nm diameter, LaPO 4 spherical nanoparticles were readily obtained at 800 °C within 0.5 h, and the nanospheres were themselves composed of Ultrafine nanocrystals of a few nanometers in diameter. Furthermore, photoluminescence (PL) characterization of the Li + -and Eu 3+codoped LaPO 4 nanocrystals was carried out. The effects of microwave irradiation temperature and Eu 3+ active center concentration, especially the doping concentration of Li + on the PL properties, were elaborated in detail. Room-temperature photoluminescence (PL) characterization revealed that the optical brightness as well as the intensity ratio of 5 D 0 -7 F 1 to 5 D 0 -7 F 2 is highly dependent on the Li + ions concentration. Introduction of 5 mol % Li + into the crystal structure enhanced the PL emission brightness more than 2-fold, and the Li 0.05 Eu 0.05 La 0.9 PO 4 nanophosphor showed the relatively most promising PL performance with the most intense emission.

Synthesis of rare earth (Pr, Nd, Sm, Eu and Gd) hydroxide and oxide nanorods (nanobundles) by a widely applicable precipitation route

“…This might be attributed to the lower scattering of evolved light and higher packing densities for nanoparticles than those for nanobundles [46]. Furthermore, the rough surfaces observed on nanobundles means the high concentration of inherent defects, which can lead to luminescence quenching [47]. Anyhow, the real reason needs further work.…”

Intense red emitting monoclinic LaPO4:Eu3+ nanoparticles: host–dopant energy transfer dynamics and photoluminescence properties

“…Chen et al 8 have investigated the effect of europium doping on the morphology and optical properties of LaPO 4 20 Another report on the optical properties of europium-doped LaPO 4 nanorods and nanoparticles also exists in the literature. 21 Lei et al 22 have explored the effect of lithium ion co-doping on the PL properties of LaPO 4 :Eu. There are also further reports on the PL properties of Eu 3+ -doped LaPO 4 .…”

Photoluminescence properties of a novel red emitting NaLaTi2O6:Eu3+ phosphor

“…The R/O values calculated for samples are between 2.94 and 2.99, which is strong evidence that Eu 3? ions mainly occupy the lattice site without inversion symmetry [24,25]. As shown in the inset of Fig.…”