Improvement And Application Of Annealing To NaYF₄:Yb³⁺,Er³⁺/xCa²⁺ Upconversion Photoluminescence

Luminescent materials doped with rare earth ions are favored because of their excellent luminescent efficiency and stability,and take on a wide range of application in the fields of optoelectronic devices,LED phosphor,optical temperature sensing and biological detection.In this thesis,based on Yb-Er co-doped Na YF4 phosphors,the upconversion photoluminescence efficiency is improved by doping Ca2+ ions.In particular,the photoluminescence intensity of NaYF₄:Yb³⁺,Er³⁺/xCa²⁺ phosphor is further enhanced though high temperature annealing and the samples are applied in optical temperature sensing and bioluminescence detection.The specific works are as follows:?1?NaYF₄:Yb³⁺,Er³⁺/xCa²⁺?x=0,0.1,0.2,0.3,0.4,0.5,0.6 and 0.7?nanophosphors are prepared by solvothermal method,their crystal structures and surface profiles are analyzed by using of XRD and SEM,respectively,and the effect of Ca2+ doping on the lattice is discussed.Under the excitation of 980 nm near-infrared laser,strong photoluminescence spectra located in the red and green bands are obtained,and the optimal Ca2+ ion concentration is 0.4 mmol.?2?NaYF₄:Yb³⁺,Er³⁺/xCa²⁺ phosphors are annealed under different temperatures,and it is found that the photoluminescence intensity of the sample presents a significant enhancement.XRD results show that crystallization phase NaYF₄:Yb³⁺,Er³⁺/xCa²⁺ changes gradually from cubic to mixed phase of cubic and hexagonal phases with the increase of annealing temperature.SEM images show that the morphology is also condensed into sheets from spherical particles.Based on this,a theoretical model is established to study the internal mechanism of the improved upconversion photoluminescence efficiency by analyzing the crystal structure and morphology of phosphor.?3?NaYF₄:Yb³⁺,Er³⁺/0.4Ca²⁺ phosphor is selected as high temperature sensing material,and the change of fluorescence intensity ratio of two green emissions from erbium ions with the increase of temperature is analyzed.The results show that the sensitivity of the temperature sensing material has been improved obviously and the range of temperature detection has been greatly expanded.?4?Finally,NaYF₄:Yb³⁺,Er³⁺/0.4Ca²⁺ phosphors are dissolved in phosphate buffer solutions,and the mixed fluorescent solution is injected into mice in order to investigate the flow of animal blood and the disease of clinical circulatory system.The feasibility of our bioluminescence detecting materials is discussed preliminarily.