Self-Assembly And Properties Of NaYF₄ Upconversion Luminescent Materials

Rare-earth doped nanomaterials which have become one of the hotspots in the field of materials science due to their unique optical,electrical and magnetic properties have been widely used in biomarker,display,optical storage,anti-counterfeiting and so on.This thesis focuses on the preparation of rare earth ion-doped fluoride and its luminescence properties,the specific research contents are as follows:1.The a-NaYF₄:Yb³⁺,Tm³⁺ powder were prepared by citric acid-assisted hydrothermal method.The effects of different citric acid addition and temperature on the luminescence intensity of the products were investigated.The results show that when CA=4mmol,temperatures are 160? and 180?,and CA=8mmol,temperatures are 120? and 160?,all spherical particles with uniform morphology and uniform particle size are obtained.The crystallinity of samples prepared at 180? are better,and the upconversion luminescence is obviously enhanced.2.The NaYF₄:Yb³⁺,Ho³⁺ and NaYF₄:Yb³⁺,Ho³⁺ @Au composites were prepared by microemulsion method.The reaction conditions were relatively mild without secondary surface modification.The results show that NaYF₄:Yb³⁺,Ho³⁺@Au composites were directly formed in the microemulsion system.It can be seen from the SEM that the encapsulation has little effect on the morphology of HAuCl4,when HAuCl4 was added to 80,100 and 200?L of HAuCl4 respectively.The biggest luminescence intensity appeared when the volume of HAuCl4 is 200?L.After added 100?L 2%HAuCl4,compared with the upconversion spectrum before calcination,the peak intensity of upconversion spectrum was significantly enhanced.3.The synthesis of NaYF₄:Yb³⁺,Er³⁺ particles by hydrothermal method with SDS/EDTA was studied.The effects of EDTA on the crystal phase,morphology and luminescence properties of the samples were investigated at different temperatures and time.The results show that,the morphology of the particles is spherical after 2h at 100?,and is rodlike spheres after 2h at 160?.The luminescence intensity is stronger at 160?.Through adjusting the reacted time,the samples are smooth and uniform with a strong luminescence after 6h at 180?.