| Due to the unique electronic shell structure,rare earth element has been widely used in the matrix or activator of luminescent material.The rare earth doped luminescent material possesses many advantages,such as high color purity,the strong ability of absorbing the excitation energy,high conversion efficiency,and thus have potentional applications in the field of light,electric,magnetic,bioimaging and so on;especially in the biology application field,the rare earth doped nanomaterials can be acted as drug carriers which can realize early diagnosis of some diseases.Fluoride and phosphate materials are important host materials.Among the fluoride material,due to the low phonon energy(360 cm-1),NaYF4 has been regarded as one of the excellent matrix;and how to simultaneously efficiently control the size of particle and enhance luminescent intensity of the material is an interesting research topic.For GdPO4 material,the relationship of structure,morphology and luminescent properties has not been completely understood.For Ca3Bi(PO4)3 host material,it is the only Ca eulytite that can be synthesized at a relatively low temperature.In this thesis,Yb3+/Er3+-doped NaYF4,Sm3+-doped GdPO4 and Ca3Bi(PO4)3 materials have been synthsised via hydrothermal and solid state method,the crystal structure,micro-morphology and luminescent properties of the materials have been investigated.The main research contents and conclusions are listed as following:(1)NaYF4:Yb3+,Er3+ powders have been successfully prepared by a hydrothermal method and the influence of the ratio of ethanol to water and the type of alcohols on the crystal structure,micro-morphology and luminescent property of the material have been investigated.The ratio of ethanol to water has an important influence on the crystal structure,micro-morphology and luminescent properties of the material.With the increase of Vethonat/Vwater,the structure of the material changes from hexagonal to coexsitence of cubic and hexagonal phase and then to cubic phase,and the particle size of the materials decreases.When Vethonal/Vwater is 2:1,the sample reaches the optimal luminescent intensity.The type of alcohols(Vaclohols/Vwater=2:1)obviously affects the crystal structure of the material.When the solvent is methanol,the material exhibits coexsitence of cubic and hexagonal phase,while the samples are hexagonal phase when the solvent is other alcohols.When the solvent is n-propyl alcohol,the sample gets the optimal luminescent intensity.(2)Sm3+ doped GdPO4 nanomaterials were synthesised by a hydrothermal method.The influence of Sm3+ doping and annealing temperature on the crystal structure,micro-morohology and luminescent properties of the material were investigated systematically.The results suggest that doping of Sm3+ exhibites no obvious influence on the crystal structure for the non-annealed samples,which possesses a hexagonal structure and a nanorod shape.Under 401 nm excitation,GdPO4·H2O:xSm3+ displays several typical emission bands located at 560,596 and 640 nm,respectively.The annealing temperature has an important influence on the crystal structure and morphology of the material.With the increase of the annealing temperature,the compound is transformed from GdPO4·H2O hexagonal structure to anhydrous GdPO4 monoclinic structure and the morphologies is varied from nanorods to ellipse-like shapes;meanwhile,the luminescent intensity has been greatly enhanced.Moreover,GdPO4·H2O:1.75%Sm3+ sample exhibits paramagnetic property.The property of cell imaging and magnetic resonance imaging of GdPO4·H2O:1.75%Sm3+ sample has been investigated,suggesting the potentional application of the GdPO4·H2O nanomaterial in the bioimaging field.(3)GdPO4·H2O:xSm3+,yTb3+ nanomaterial has been prepared via a hydrothermal method and the influence of Sm3+/Tb3+ doping and the volume of NH3 ·H2O on the crystal structure,micro-morohology and luminescent properties of the material has been investigated.Tb3+ can effieciently transfer energy to Sm3+.By adjusting the concentration of Tb3+ and Sm3+,the color of the material can be tuned.The increase of the volume of NH3·H2O causes the preferred orientation growth of the sample;however,the grain size of the material decreases and the luminescent intensity decreases with the addition of NH3·H2O.(4)Sm3+ doped Ca3Bi(PO4)3 powders were prepared by a high temperature solid state reaction.All the samples exhibit pure cubic phase.The SEM image displays that the material is well-crystalline and uniform.With the increase of the Sm3+ concentration,the luminescent intentiy firstly increases and then decreases.When the doping concentration of Sm3+ is 0.03,the luminescent property becomes optimum.The main mechanism of concentration quenching for the Sm3+ doped Ca3Bi(PO4)3 material is dipole-dipole interaction.The chromaticity coordinates of Ca3Bi0.97(PO4)3:0.03Sm3+ sample is(0.5406,0.4566),which is located at the orange light region,indicating that the phosphor may be used as an orange phosphor for NUV-based white LEDs. |
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