Synthesis, Characterization And Luminescence Properties Of Environmental Functional Material β-NaYF₄ Doped With Rare Earth

Upconversion luminescence materials is a kind of functional materials with wide application. They have shown great potential and especial advantages in labeled biological molecules, solid-state lasers, solar cells, environmental purification etc. In this thesis, we carried on the research of rare earth doped upconversion luminescence materials for its unique application in environmental science,,and synthesizedβ-NaYF4 of high conversion efficiency, which can effectively save resources and energy. This materials may apply in environmental monitoring, analysis and pollution control fields as fluorescence labeled material or composited with TiO2.The main contents are as follows:(1)The samples were prepared by high temperature solid-state synthesis at different temperatures, and were characterized and analyzed.lt was found that the sample calcined for 3h at 630℃had the most pure phase, and of which the main product was P-NaYF4 and it had the highest luminescence intensity, while samples at other temperatures contained impure phase and luminescence intensity was not high.(2) The impact of different surfactants on morphology of samples was carried on by hydrothermal synthesis, and different luminescence properties were compared. The results indicated the morphology of sample added EDTA under the same condition was the best and the luminescence intensity of sample added citric acid was the highest.(3)The NaYF4:Yb,Er and NaYF4:Yb,Tm were prepared by solvothermal synthesis in water/ethanol/oleic acid system. The properties of prepared samples were comprehensively compared.It is found that pure phaseβ-NaYF4 can be synthesized by controlling appropriate reaction conditions. The order of luminescence intensity of samples synthesized by three methods from high to low was solid-state synthesis, hydrothermal synthesis and solvothermal synthesis.(4) Upconversion mechanism in green area, red area in P-NaYF4 of Yb-Er co-activate system and it in blue area, red area inβ-NaYF4 of Yb-Tm co-activate system was discussed, respectively. From the analysis of relationship between pumped power and luminescence intensity, we can deduced that green emission and red emission belong two-photon process in Yb-Er co-activate system, while the visible area emission of Yb-Tm co-activate system contains two-photon, three-photon and four-photon process.