Study Of Photoluminescence Properties And Thermal Effect Of Rare Earth Co-doped NaGdF₄Nanocrystals

Because of excellent magnetic and optical properties, compounds containingGd³⁺have great potential in various fields. In addition, NaGdF₄also become hotspot topic in biomedical applications. In recent years, people have done a lot ofworks in the compound multi-functional materials of up-conversion fluorescenceand Magnatic Resonance Imaging （MRI）, there was a lot of reports andconsequently realized the fluorescence detection and MRI analysis in organism.This thesis reports associated related further research in the up-conversionfluorescence of the rare earth co-doped NaGdF₄,and an interesting finding on theproperty of NaGdF₄.First, we investigated the influence of annealing temperature to thefluorescence intensity of hexagonal phase NaGdF₄:Yb³⁺/Er³⁺, and then optimizedthe annealing temperature. We prepared the NaGdF₄:Yb³⁺/Er³⁺precursor withprecipitation，and annealed them at400℃-800℃. From the fluorescence spectrummeasurements of the samples, we got the strongest intensity in the samples sinteredat600℃.And then we performed through the X Ray diffraction（XRD）、X RayFluorescence（XRF）, experiments, we analysed the influence of oxygen ion doped byhyperthermia sintering on the crystal structure and the up-conversion fluorescenceintensity of sample.Second, we measured the fluorescence intensity ratio of two green light inalong with the change of the temperature, obtained the expression of FIR variationwith temperature; And research the similar "saturation" phenomenon of NaGdF₄:Yb³⁺/Er³⁺samples sintered in600℃. It was found the intension that graduallybecome flat in along with growing of laser power. And we gave an explanation tothe thermal effect of samples induced by infrared laser that weaken or madequenches the fluorescent. And design two groups of experiments verify theexplanation, the first group dispersed in the water, and powder and tablettingsamples in the air, the second group is different concentrations of Yb³⁺dopedNaGdF₄: Yb³⁺/Er³⁺samples. And we can use it to application of thermal effect.Through the FIR, we got the temperature of the heating effect of induced by infraredlaser of different state and different Yb³⁺concentrations. Further, combined with therate equation and boltzmann distribution, we fitted the relationship betweenfluorescence intensity and laser power.Finally, because the high efficiency up-conversion fluorescence of NaGdF₄:Yb³⁺/Er³⁺, coped Eu³⁺in NaGdF₄: Yb³⁺/Er³⁺, through the energy transfer of Er³⁺toEu³⁺,we realized the up-conversion of Eu³⁺. And we analysed the energy transfer path of Er³⁺to Eu³⁺. Design and preparation the nuclear shell structure of sample toimprove the fluorescence intensity ratio of Eu³⁺to Er³⁺.