Preparation And Photoluminescence Properties Of α-NaYF₄:Eu³⁺ Based Inorganic-Organic Hybrid Nanomaterials

Rare earth doped Na YF4 nanocrystals, which have two polymorphic forms: cubic(a-) Na YF4 and hexagonal(b-) Na YF4, have received intensive attention in recent years because of their unique luminescence properties as a result of their very low phonon energy. However, their luminescence is largely limited by the low optical absorption of rare earth ions, and because of this, an extensive amount of attention has been focused on the improvement of their photoluminescence properties. In order to improve the photoluminescence properties of a-Na YF4:Eu3+ nanocrystals, they were used to prepare the inorganic-organic hybrid nanoparticles with the organic ligands, which have strong optical absorption. These ligands can efficiently transfer their absorbed energy to the Eu3+ ions for strong photoluminescence emission.In this thesis, undoped a-Na YF4 nanocrystals were synthesized using the solvothermal method under the optimal experimental conditions: the reaction temperature at 180 oC, the molar ratio of Y3+/F-= 1:4, the reaction time of 16 h. Their average particle size was about 30 nm. The Eu3+ doped a-Na YF4 or the a-Na YF4: Eu3+ nanocrystals were prepared using the ion-exchange method. a-Na YF4: Eu3+ nanocrystals with different Eu3+ doping concentrations were prepared using this method. The photoluminescence properties of the ion-exchanged a-Na YF4: Eu3+ nanocrystals have been systematically studied. In addition, the photoluminescence quenching concentration has also been identified.The ion-exchanged a-Na YF4: Eu3+ nanocrystals were then used as matrix to fabricate the inorganic-organic hybrid nanoparticles with the organic ligands with organic ligands, pyromellitic acid(PMA) and 2-thenoyltrifluoroacetone(TTA). After the a-Na YF4:Eu3+-PMA and a-Na YF4:Eu3+-TTA inorganic-organic hybrid nanoparticles were obtained, their photoluminescence properties were investigated in detail. Strong energy transfer from the organic ligands to the Eu3+ ions and excellent photoluminescence properties had been observed.