Synthesis And Properties Of Monodisperse Upconversion Rare Earth Fluoride

In this thesis,a series of monodisperse upconverted nanoparticles were prepared by the thermal decomposition method,and their luminescence properties were studied.The up-conversion nanoparticles were compounded with the semiconductor by a simple method,the photocatalytic performance of the composite photocatalyst was tested,and the possible reaction mechanism was analyzed.The details are as follows:?1?Na REF4: Yb³⁺,Er³⁺?RE = Y,Lu,Gd?and NaYF₄: Yb³⁺,Ho³⁺/Tm³⁺/(Er³⁺,Tm³⁺)were synthesized by the thermal decomposition.From SEM,XRD,and PL characterization,we know that they are all monodisperse,strongly emitting upconverted nanoparticles.Among them,NaYF₄: 16% Yb³⁺,8% Er³⁺,5% Tm³⁺?CIE: 0.363,0.378?and NaYF₄: 16% Yb³⁺,8% Er³⁺,6% Tm³⁺?CIE: 0.366,0.370?are close to white light.?2?The prepared NaYF₄:Yb³⁺,Tm³⁺@NaYF₄@Cd S/g-C₃N₄ ternary photocatalysts were characterized by XRD,SEM,TEM,PL,UV-Vis,etc.,and their phase,morphology and luminescence characteristics were characterized analysis.It was confirmed that the three were successfully compounded.Through a series of experiments,NaYF₄:Yb³⁺,Tm³⁺@NaYF₄ and Cd S,g-C₃N₄ mass ratio of 2:1:1,and heat treatment temperature of 400 ? NaYF₄:Yb³⁺,Tm³⁺@NaYF₄@Cd S/g-C₃N₄ composite catalyst is the best catalyst.Under near-infrared light,the degradation rate of the best catalyst for rhodamine B was 37.1% in 300 min.?3?NaYF₄: 20%Yb³⁺,2%Tm³⁺@NaYF₄: 20%Yb³⁺@NaYF₄/g-C₃N₄ composite photocatalysts were prepared,and their degradation rates were arranged in the following order under different light sources: sunlight> ultraviolet light> visible light.When the near infrared light was irradiated for 300 minutes,the degradation rate of NaYF₄:20%Yb³⁺,2%Tm³⁺@NaYF₄: 20%Yb³⁺@NaYF₄/g-C₃N₄ was about 56.3%.The hydrogen evolution rate of the composite catalyst under simulated sunlight is 1920 ?mol·h-1·g-1.?4?The synthesis of NaYF₄: 20%Yb³⁺,2%Tm³⁺@NaYF₄: 20%Yb³⁺@NaYF₄@ Cd S/g-C₃N₄ ternary composite photocatalyst,NaYF₄:20%Yb³⁺,2%Tm³⁺@NaYF₄: 20%Yb³⁺@NaYF₄@Cd S/g-C₃N₄,Cd S,g-C₃N₄ was subjected to rhodamine B degradation experiments,and the results showed that NaYF₄: 20%Yb³⁺,2%Tm³⁺@NaYF₄: 20%Yb³⁺@NaYF₄@Cd S/g-C₃N₄ has good photocatalytic activity.The degradation rate of UCNPs@Cd S/g-C₃N₄ was about 53.8% when exposed to near-infrared light for 300 min.Under simulated sunlight,the hydrogen evolution rate of UCNPs@Cd S/g-C₃N₄ is 957 ?mol·h-1·g-1,which is 4.8 times and 1.9 times that of Cd S and g-C₃N₄,respectively.