Synthesis And Luminescence Property Of Rare Earth Fluoride Luminescent Materials Based On Energy Transfer

Compared with other rare earth luminescent materials,rare earth fluoride phosphors are widely used in biomedical,solar cell,photocatalysis due to their good biocompatibility,low phonon energy,high refractive index and so on.In this dissertation,taking NaGdF₄,Ba2YF7 and?-NaYF4 as matrices,fluoride multicolor phosphors doped with various rare earth ions(Dy³⁺,Sm³⁺,Tb³⁺,Eu³⁺,Yb³⁺,Tm³⁺)were synthesized by hydrothermal method.The crystal structure,morphology,fluorescence properties,energy transfer and magnetic properties were systematically analyzed.The main experimental contents are as follows:1.A series of NaGdF₄:Dy³⁺/Sm³⁺phosphors were prepared by hydrothermal strategy using ethylenediaminetetraacetic acid disodium salt?EDTA-2Na?as assistant.Under the excitation of 274 nm,the NaGd F₄ samples single-doped with Dy³⁺or Sm³⁺ions show strong blue light and orange red light emission,respectively,NaGdF₄:Dy³⁺,Sm³⁺phosphors achieve blue,white and red-orange emissions.Under 366 nm excitation,energy transfer process from Dy³⁺to Sm³⁺exists in NaGdF₄:Dy³⁺,Sm³⁺phosphors,and the transfer mechanism is dipole-dipole interaction.By changing the excitation wavelengths and the doped concentration of Dy³⁺and Sm³⁺,tunable luminescence and white emission are realized.The samples also show paramagnetic properties.2.A series of Ba₂YF₇:Dy³⁺/Tb³⁺/Eu³⁺spherical nanoparticles were synthesized by hydrothermal method.Spectra tests show that the phosphors single-doped with Dy³⁺,Tb³⁺or Eu³⁺ions can emit blue,green and red light,respectively.By changing the excitation wavelengths and the doped ratio of rare earth ions,Ba₂YF₇:Dy³⁺,Tb³⁺,Ba₂YF₇:Dy³⁺,Eu³⁺,Ba₂YF₇:Tb³⁺,Eu³⁺phosphors achieve blue-green light,red-orange and white light and yellow-green light emissions,respectively.Meanwhile,the energy transfer processes from Dy³⁺to Tb³⁺,Dy³⁺to Eu³⁺and Tb³⁺to Eu³⁺are observed,and the transfer mechanisms are all dipole-dipole interaction.In addition,green light,yellow light and white light emissions can be realized in Ba₂YF₇:Dy³⁺,Tb³⁺,Eu³⁺phosphors by changing the excitation wavelengths.3.A series of?-NaYF₄:Yb³⁺/Tm³⁺/Eu³⁺phosphors were prepared by hydrothermal method.In the up-conversion luminescence process,the?-NaYF₄:Yb³⁺,Tm³⁺/Eu³⁺samples achieve energy transfer from Yb³⁺to Tm³⁺and Eu³⁺,and generate blue and red orange emissions,respectively.By changing the concentration of Eu³⁺,blue light,white light and red orange light emissions are obtained in NaYF₄:Yb³⁺,Tm³⁺,Eu³⁺samples and the energy transfer from Tm³⁺to Eu³⁺occurs.In the down-conversion process,the characteristic emission of Eu³⁺appears in the photoluminescence spectra of?-NaYF₄:Yb³⁺,Tm³⁺,Eu³⁺monitored at characteristic excitation peak of Tm³⁺,indicating that Tm³⁺transfers the energy to Eu³⁺,and the samples can achieve purple light and pink light emissions.