Formation and Luminescence of Sodium Rare Earth Fluoride Nanocrystals in the Presence of Chelators

Abstract

The single crystal structure of sodium yttrium fluoride (NaYF4) nanoparticles formed mainly by aggregation in aqueous phase was first confirmed by high resolution transmission electron microscope (HRTEM). Then, effects of reactant concentrations and pH on the formation of NaYF4 nanocrystals were investigated and described in the presence of sodium citrate (Na-citrate). The results showed that the non-aggregation formation of NaYF4 was dominant under a low concentration range of reactants, and the aggregation formation was dominant under a high concentration range of reactants. For comparison, NaYF4 nanocrystals were also synthesized by co-precipitation in the presence of various other chelators, not only amino-carboxyl (H2N-C) types involving (Na-EDTA) and sodium nitrilotriacetate (Na-NTA) but also hydroxyl-carboxyl (HO-C) types including sodium citrate (Na-citrate), sodium malate (Na-malate), and potassium sodium tartrate (K, Na-tartate). All the chelators showed a similar influence on the particle formation. However, the size of the final product was different corresponding to the different chelators. An upconversion fluorescent material, cubic NaYF4 nanocrystal co-doped with ytterbium and erbium with diameter about 10 nm was successfully achieved at room temperature. Under 980 nm laser excitation, the red emissions at 652 and 679 nm were much stronger than green emissions at 520 and 541 nm. Additionally, effects of concentrations of the different chelators on the fluorescent properties of the formed NaYF4:Yb, Er nanocrystals were also investigated. Different chelators affected the fluorescent properties differently, according to their respective physical and chemical properties.

Self-assembled growth of LuVO4 nanoleaves: hydrothermal synthesis, morphology evolution, and luminescence properties

“…Na 2 tar is an efficient chelating reagent, which has been reported to regulate the morphology and size of the products in the hydrothermal system. [22][23][24][25][26][27][28] In the present system, Na 2 tar also plays an important role in the growth process of tetragonal LuVO 4 crystals with different morphologies and dimensions. Therefore, LuVO 4 samples have been prepared with different contents of Na 2 tar (0 g, 0.1 g, 0.3 g, 0.4 g) at 180 uC for 24 h and the pH value was maintained at 10.…”

“…In particular, the addition of special chelating agent, which has a significant effect on the kinetics of the crystal growth, has been demonstrated to be an effective strategy to achieve control over the morphology of final products. [19][20][21] Because of the high thermal stability and ability to form complexes with other metal ions, the sodium tartrate (Na 2 C 4 H 4 O 6 ?2H 2 O) has a dynamic effect as the capping reagent and shape modifier by adjusting the growth rate of different facets under hydrothermal conditions, resulting in the formation of various geometries of the final products, such as Co spheres 22 and hyperbranches, 23 Ni nanobelts, 24 hydroxyapatite hollow spheres, 25 NaYF 4 nanoparticles, 26 CuO prickly microspheres, 27 boehmite, 28 and so on.…”

Synthesis of Highly Luminescent Silica-Coated Upconversion Nanoparticles from Lanthanide Oxides or Nitrates Using Co-Precipitation and Sol–Gel Methods

“…Complexes formed are adsorbed on the surface of NPs, limiting the growth in size of the resulting UCNPs. In fact, smaller NPs size is generally achieved by increasing the concentration of different chelators [54]. Moreover, EDTA is used to prevent precipitation before proceeding with the synthesis procedure [55].…”