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

This work reports a simple hydrothermal route using citric acid as a "shape modifier" for the controlled synthesis of luminescent TbPO4: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 TbPO4 crystals. The photoluminescence properties of TbPO4:Eu are investigated. The excitation spectra and the variation of the D-5(4) lifetime values as a function of the Eu3+ concentration points out the occurrence of Tb3+-to-EU3+ 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.