Preparation And Properties Of Rare Earth Doped Bismuth Salt Inorganic Nano-fluorescent Material

Rare earth luminescent materials are made up via matrix that can not emit light by itself and rare earth ions with rich energy level.They are one of the most important rare earth functional materials,and mainly used in the fields of life lighting,biological detection,optical imaging and so on.Furthermore,rare earth luminescent materials play an increasingly important role in the human life and resource utilization.Therefore,the inorganic fluorescent nano-materials of bismuth salt doped with different rare earth ions were prepared via a simple and rapid synthesis method,and the structure performance and fluorescence mechanism of the target products were studied systematically.The main research work was as follows:?1?A novel blue-emitting nano-material of Tm³⁺-doped NaBiF₄ has been successfully synthesized via a facile and rapid reaction at room temperature.XRD,TEM,EDX were utilized to characterize structural perfor mance of the target products,and the fluorescence properties were measured via fluorescence spectrometer.XRD analysis exhibited the target products were hexagonal phase of NaBiF₄ with a high crystallization degree,the position of diffraction peaks matc hed well with the main peaks?100???101???201???211?of NaBiF₄?JCPDS No.41-0796?,which indicated that the crystal structure of the target products did not change after doping.TEM analysis displayed the target products showed a well-distributed spherical-like morphology,and the average particle size was calculated via the Debye-Scherrer equation based on the half height width(?FWHM=0.244 degree?of the?100?plane to be 36 nm.Moreover,the elements of sodium?Na??bismuth?Bi??fluorine?F?and thulium?Tm?were verified to be present in the target products via EDX spectra,so the target products are confirmed to be NaBiF₄:Tm³⁺.The fluorescence spectrum showed the target products could emit bright blue light that the characteristic emission peak situated at⁴51 nm corresponded to the transitions of Tm³⁺ions from ¹D₂?³F₄ under the light excitation of 357 nm.Moreover,the optimal doping concentration of Tm³⁺ions was obtained to be 50 mol%and the mechanism of concentration quenching was proved as electric dipole-dipole interactions.The color coordinate of the target product was determined to be?0.1354,0.0602?,and the color purity was about 92.4%.Besides,the crystal field environment around the luminescence center Tm³⁺ions was further explored via the Judd-Ofelt theory,the result was that the change of the crystal field environment would induce a significant influence on the energy level transition of the luminescence center Tm³⁺ions.The target products were promising candidates for blue-emitting phosphors in the fields of white light-emitting diodes,ceramics as well as display devices and so on.?2?A green-emitting nano-material of Yb³⁺and Er³⁺ions co-doped NaBiF₄ has been successfully synthesized via a facile and rapid reaction at room temperature.The effects of the amount of ammonium fluoride?NH₄F?,the amount of bismuth nitrate?Bi?NO₃?₃?,the amount of ytterbium nitrate?Yb?NO₃?₃?as sensitizer,the amount of erbium nitrate?Er?NO₃?₃?as luminescent center,and reaction temperature as well as reaction time on the structure and fluorescence properties of the target products were investigated via single factor optimization experiments.The single factor optimization results obtained were as follows:the amount of ammonium fluoride NH₄F n _NH4F=22 mmol,the amount of bismuth nitrate Bi?NO₃?₃ n _Bi3+/n _Na+=0.5,the amount of ytterbium nitrate as sensitizer Yb?NO₃?₃ n _Yb3+/n _Bi3+=0.25,the amount of erbium nitrate as luminescence center Er?NO₃?₃ n _Er3+/n _Bi3+=0.025,and the reaction temperature T=35 ^oC as well as the reaction time t=1.5 min.On the basis of single factor optimization experiments,four significant influence factors?ammonium fluoride NH₄F,ytterbium nitrate Yb?NO₃?₃,erbium nitrate Er?NO₃?₃ and reaction temperature T?were selected to conduct further optimization via orthogonal experiments.The orthogonal optimization results obtained were as follows:the amount of ammonium fluoride NH₄F n _NH4F=22 mmol,the amount of ytterbium nitrate as sensitizer Yb?NO₃?₃ n _Yb3+/n _Bi3+=0.3,the amount of erbium nitrate as luminescence center Er?NO₃?₃ n _Er3+/n _Bi3+=0.03,and the reaction temperature T=35 ^oC.Under this optimum condition,the target products C₁,C₂ and C₃ were synthesized and the structural performance were characterized via XRD,TEM,EDX,and the fluorescence properties were measured via fluorescence spectrometer.XRD analysis showed that the crystal phase of the target product s were similar,the position of diffraction peaks matched well with the main peaks?100???101???201???211?of NaBiF₄?JCPDS No.41-0796?,which indicated that the crystal structure of the target products did not change after doping.The sharp and narrow peak showed a good crystallinity of the target products.TEM analysis showed that the morphology of the target products almost are the same,and all of them are well-distributed spherical-like nanoparticles.With the help of Debye-Scherrer equation,the average particle size of the target products was calculated based on the half height width(?FWHM=0.304degree?of the?100?plane to be about 29 nm.EDX spectra showed that the element composition of the target products contained sodium?Na?,bismuth?Bi?,fluorine?F?,ytterbium?Yb?and erbium?Er?,so the target products were confirmed to be NaBiF₄:Yb,Er.The fluorescence spectra of the target products were similar to the samples with the best fluorescence properties in orthogonal experiment,and they both showed the characteristic emission peaks of Er³⁺ions.The emission peak with relatively low intensity situated at⁵20 nm corresponded to the transitions of Er³⁺ions from ²H_11/2?⁴I_15/2,while the sharp emission peak with higher intensity situated at⁵40nm corresponded to the transitions of Er³⁺ions from ⁴S_3/2?⁴I_15/2,there was also a weak emission peak situated at⁶55nm corresponded to the transitions of Er³⁺ions from ⁴F_9/2?⁴I_15/2,which indicated that the fluorescent nano-material could be effectively excited by the light of 980 nm.This work provided a better reference for the synthesis of different rare earth ions doped sodium tetrafluorobismuth fluorescent nano-materials,and also established a solid foundation for its exploration in depth.