Citric Acid-Assisted Hydrothermal Synthesis of Luminescent TbPO₄:Eu Nanocrystals: Controlled Morphology and Tunable Emission

Abstract

This work reports a simple hydrothermal route using citric acid as a "shape modifier" for the controlled synthesis of luminescent TbPO 4 :Eu nanocrystals. The size and morphology of products change remarkably when the proportion of citric acid involved in the reaction increases. The multiple roles that citric acid plays during the controlled synthesis are discussed to try to understand the crystallization and growth dynamics of TbPO 4 crystals. The photoluminescence properties of TbPO 4 :Eu are investigated. The excitation spectra and the variation of the 5 D 4 lifetime values as a function of the Eu 3+ concentration points out the occurrence of Tb 3+ -to-Eu 3+ energy transfer, resulting in a maximum absolute emission quantum yield of 0.14. The possibility to tune the size, the shape, and the optical properties of the nanocrystals reported in this work might be useful for applications in optoelectronics or biolabeling. Moreover, this simple approach might also be applied for the synthesis of other luminescent phosphates.

Citrate mediated synthesis of uniform monazite LnPO4 (Ln = La, Ce) and Ln:LaPO4 (Ln = Eu, Ce, Ce + Tb) spheres and their photoluminescence

“…The procedure is based on a homogeneous precipitation process, which takes place through the controlled release under mild conditions (120°C) of La 3+ cations from lanthanide-citrate complexes in the presence of phosphoric acid using ethylene glycol (EG) as solvent. It should be noted that uniform particles with different morphologies of some LnPO 4 such as YPO 4 [21] and TbPO 4 [22] have been already synthesised in aqueous solutions using citrate ions as an organic additive to control particle size and shape. However, none of the reported procedures gave rise to spheres.…”

Synthesis, morphology and phase transition of the zinc molybdates ZnMoO4·0.8H2O/α-ZnMoO4/ZnMoO4 by hydrothermal method

“…Citric acid is one effective surfactant used to modify the shape of materials, for example sheet-like BaMoO 4 [31], nanocrystals of TbPhO 4 [32], disk-like ZnO [33] and InOOH hollowspheres [34] have been successfully synthesized in the presence of citric acid. In the current work, ZnMoO 4 Á 0.8 H 2 O, rhombus sheet morphology and a pentacle structure have been obtained.…”

Citric acid-assisted growth of lanthanide ions co-doped one-dimensional upconversion microcrystals and their photovoltaic applications

“…It is well known to dynamically modify the crystal growth by either promoting or inhibiting the crystal growth along specific crystallographic facets. Citric acid, a tricarboxylic acid with three carboxylic acid groups and one hydroxyl functional group, which can serve as the chelating agent due to its chelating ligand, was once reported as ''shape modifiers'' to adjust and control the size and morphology of TbPO 4 :Eu Nanocrystals [24]. The advantage of using CA as a shape modifier is that the residual CA on the surface can be more easily removed than other organic molecules due to the good water solubility of CA.…”