Study On Preparation And Properties Of Rare-earth Doped Lanthanum Sodium Sulfates

In this thesis rear-earth doped lanthanum sodium sulfate nanomaterials,including NaGd?SO₄?₂:Ln and NaTb?SO₄?₂:Ln,were successfully prepared by solvothermal method.A series of characterization such as scanning electron microscope?SEM?,transmission electron microscope?TEM?,X-ray diffraction?XRD?,energy-dispersive spectrometer?EDS?were carried out to investigate the microstructural morphology,phase and composition as well as magnetic and fluorescent properties of the obtained products.Cytotoxicity and applications in fluorescent bio-imaging and intracellular detection of Fe3+ ions of the prepared nanomaterials were evaluated with human cervical cancer?HeLa?cell line as a cell model.Detailed research contents and results are listed as follows:? Preparation and characterization of rare earth elements doped NaGd?SO₄?₂:LnNaGd?SO₄?₂:Tb and NaGd?SO₄?₂:Er,Yb were prepared by a solvothermal method.The characterization results demonstrated that these nanomaterials were hexagonal NaGd?SO₄?₂ exhibiting 1D rod-like morphology with a diameter of 300 nm and length of 1 ?m.The presence of Gd element endowed desirable magnetic resonance properties to the products.Results of in vivo magnetic resonance imaging?MRI?carried out in mice indicated that the products could be used to as a T1 contrast agent for the liver and kidney organs.Taken together low cytotoxicity of the products indicated by a high cell viability of 95% obtained with NaGd?SO₄?₂:Tb concentration of 250 ?g mL-1,our products might find use in applications as a positive MRI agent.Down-converting NaGd?SO₄?₂:Tb and up-converting NaGd?SO₄?₂:Er,Yb 1D nanomaterials were obtained by Tb doping and Er-Yb co-doping,respectively.Upon excitation of UV light??EX = 369 nm?,the prepared NaGd?SO₄?₂:Tb emitted green down-conversion luminescence centered at 491 nm and 545 nm,according to the energy transfer of 5D4?7F6 and 5D4?7F5 of Tb³⁺.The luminescent emission intensity of NaGd?SO₄?₂:Tb solution sharply quenched after adding into metallic ions such as Fe3+,Cu2+.Based on this,NaGd?SO₄?₂:Tb was anticipated to be a novel fluorescent detecting agent for metallic ions.Sintered products of NaGd?SO₄?₂:Er,Yb calcinated at 900 °C emitted bright upconversion luminescence centered at 545 nm corresponding to 5D4?7F6 in Tb³⁺,and 672 nm corresponding to 5D4?7F5 in Er³⁺ when excited by 980 nm laser.The major emission peaks at 545 nm and 672 nm,according to the energy transfer of 5D4?7F6 in Tb³⁺ energy level and 5D4 ?7F5 in Er³⁺ energy level.Further investigation on fluorescent mechanism showed that this upconversion process was a two-photon absorption process.? Preparation and characterization of rare earth doped NaTb?SO₄?₂:LnNaTb?SO₄?₂:Ln?Ln= Gd,Ce,Li,Eu,Er,Yb?nanomaterials were prepared by a simple solvothermal method.Characterization results revealed that the products were hexagonal Na Tb?SO₄?₂,exhibiting sphere-like morphology with a diameter of 300⁵00 nm.The products transformed into Tb₂O₂SO₄ after calcination at 900 °C.We further investigated the photoluminescent properties of the products and their applications in fluorescent detection of metallic ions.Experimental results showed that the products exhibited down-conversion luminescent properties.Upon excitation of UV light??EX = 369 nm?,the prepared NaTb?SO₄?₂:Ln?Ln = Gd,Er,Yb?emitted green down-conversion luminescence centered at 491 nm and 545 nm,according to the energy transfer of 5D4?7F6 and 5D4?7F5 of Tb³⁺.NaTb?SO₄?₂:Ln-water dispersion aslo have the ability to detect mental ions.Tb₂O₂SO₄:Er,Yb obtained from calcination of NaGd?SO₄?₂:Er,Yb exhibited unique fluorescent properties as well as the uniform well-dispersed sphere-like morphology of NaGd?SO₄?₂:Er,Yb.On one hand,the intensity of fluorescent emission was remarkably enhanced.On the other hand,the color of the fluorescence excited by UV light??EX = 369 nm?changed from red to blue as the concentration of Tb₂O₂SO₄:Er,Yb in water decreased from > 1.0 × 10-2 M to 1.0 × 10-3 M.Low cytotoxicity was suggested by a high cell viability of 95% when the incubation concentration of Tb₂O₂SO₄:Er,Yb was 100 ?g mL-1.Tb₂O₂SO₄:Er,Yb spheres were found to be endocytosed by HeLa cells after an incubation time of 10 h.The internalized Tb₂O₂SO₄:Er,Yb remained to be fluorescent and successfully accomplished fluorescent bio-imaging by lightening the cells bright blue.Whereas the blue fluorescence observed in cells sharply quenched with the addition of Fe3+,indicating potential applications of our Tb₂O₂SO₄:Er,Yb as a novel fluorescent detector of in vivo Fe3+ ions for living cells.