Synthesis,Properties,Mechanism And Application Of Lanthanide Ions Doped BaF₂ And BaCeF₅ Fluorescent Materials

In recent decades,fluorescent materials have been extensively studied,such as white light-emitting diodes,biomarkers,solar concentrators,etc.Although the application of fluorescent materials is very extensive,with the development of various related applications,there are also higher requirements for various properties of the fluorescent powder,such as:luminous intensity,color adjustment and so on.In this paper,a series of lanthanide ion-doped BaF₂and BaCeF₅fluorescent samples were synthesized by coprecipitation-hydrothermal method,and their luminescence mechanism,energy transfer mechanism and potential applications were also studied:（1）A series of Ce³⁺and Tb³⁺single-and co-doped BaF₂fluorescent materials were synthesized by co-precipitation-hydrothermal method.The structure,morphology,elemental composition and photoluminescence properties of the synthesized materials were studied by XRD,TEM,EDX,PL and PLE.XRD and TEM measurements showed that the synthesized phosphors had a cubic structure,and the grain size calculated by the Scherrer formula was in agreement with the crystal size observed by TEM.The fluorescence excitation and fluorescence emission spectra of Ce³⁺and Tb³⁺single-doped BaF₂substrates were analyzed using PL and PLE,respectively.In BaF₂,the Ce³⁺emission spectrum and the Tb³⁺excitation spectrum have a large overlap,indicating the possibility of energy transfer.According to the energy level relationship between Ce³⁺and Tb³⁺,the energy transfer mechanism from Ce³⁺to Tb³⁺in BaF₂was analyzed.The energy transfer efficiency can reach 88.22%by calculation.Through CIE coordinate analysis,it was found that the Ce³⁺single-doped BaF₂sample showed blue light,and the Ce³⁺and Tb³⁺co-doped samples showed green light.The Cu²⁺ion detection reagent was prepared by uniformly dispersing the phosphor powder in absolute ethanol.Through the comparative study of a series of metal ions,it is found that the detection reagent has a special sensitivity to the aqueous solution containing Cu²⁺.The reasons for the fluorescence quenching of detection reagents caused by Cu²⁺ions were analyzed from the aspects of aggregation-induced fluorescence quenching and energy transfer.The detection reagents and detection samples were analyzed by DLS and UV-vis,respectively.And it was finally determined that the energy transfer was the cause of fluorescence quenching caused by Cu²⁺ions.At the same time,the detection effect of detection reagents on Cu²⁺ions in the presence of common ions in wastewater was also studied.The detection principle of Cu²⁺ion detection reagent for Cu²⁺-containing aqueous solution and the possibility of actual detection are analyzed from both quantitative and qualitative aspects.This paper believes that the phosphor has great application potential in the actual detection of Cu²⁺in wastewater.（2）BaCeF₅ fluorescent nanomaterials doped with different concentrations of Tb³⁺and Eu³⁺were synthesized by coprecipitation-hydrothermal method.The structure,morphology,photoluminescence properties,valence composition,UV absorption and other properties of the doped samples were studied by XRD,TEM,PL and PLE,XPS,UV-vis,etc.The fluorescence emission spectrum shows that the emission center of BaCeF₅sample itself is at358 nm,which is blue light emission.The fluorescence emission spectrum of the Tb³⁺-doped BaCeF₅luminescent material is composed of the fluorescence emission spectrum of Ce³⁺and the fluorescence emission spectrum of Tb³⁺.The emission of Tb³⁺-doped BaCeF₅samples was changed from blue to green by changing the content of doped Tb³⁺.It is found by calculation that the energy transfer efficiency from Ce³⁺to Tb³⁺in Tb³⁺-doped BaCeF₅material can reach up to 87.69%.By doping Eu³⁺in BaCeF₅:10mol%Tb³⁺,the energy transfer process from Tb³⁺to Eu³⁺was studied,and the phosphor samples continued to transition from green to orange.It is found by calculation that the energy transfer efficiency from Tb³⁺to Eu³⁺in Tb³⁺/Eu³⁺doped BaCeF₅material can reach up to 71.72%.The energy transfer mechanism of Ce³⁺→Tb³⁺→Eu³⁺in a series of BaCeF₅co-doped with Tb³⁺/Ce³⁺was analyzed.At the same time,by changing the concentration of Tb³⁺and Eu³⁺in the BaCeF₅matrix,the transition from blue to green to orange can be achieved.The results show that this material is expected to be applied to multi-color emission-modulating luminescent materials and incandescent lamps.