Preparation And Luminescence Properties Of NaYF₄:Ce³⁺,Tm³⁺,Yb³⁺ Nanocrystals And Opal Structures

In the era of rapid development of science and technology,rare earth as a key material become an indispensable strategic resource with the rise and development of various new energy sources.With our country paying more and more attention to rare earth resources,how to improve the utilization rate of rare earth resources and the intensity of rare earth luminescence has become an important research topic.In this paper,Na YF₄doped nanocrystals with hexagonal phase,which have low photon energy,were prepared by solvothermal method.Three kinds of rare earth ions ytterbium(Yb³⁺),thulium(Tm³⁺),cerium(Ce³⁺)are selected to doping Na YF₄nanocrystals,because ytterbium(Yb³⁺)and cerium(Ce³⁺)can realize dual-wavelength absorption,and both of them have good energy level matching with thulium(Tm³⁺),which is conductive to energy transfer between rare earth ions.In order to study the luminescence mechanism of Na YF₄:Yb³⁺,Tm³⁺,Ce³⁺nanocrystals,using fluorescence spectrophotometer to measure the luminescence of nanocrystals,which can obtain the fluorescence spectra of nanocrystals irradiated by two wavelengths of light sources.Analying the effects of fixing the doping concentration of 5%Yb³⁺and 10%Ce³⁺and changing doping concentration of Tm³⁺on the luminescent intensity of nanocrystals,and it was found that the luminescent intensity of Na YF₄nanocrystals with the doping concentration of 5%Tm³⁺was the strongest.Monodisperse polymethylmethacrylate(PMMA)colloidal solutions with particle sizes of 200 nm,209 nm,222 nm,299 nm and 435 nm were prepared by soap-free emulsion polymerization.Assembling PMMA colloidal solution on glass substrate by vertical deposition self-assembly,three-dimensional PMMA opal photonic crystals with stop bands of 450 nm,468 nm,500 nm,674 nm and 980 nm were obtained.Nanocrystals of Na YF₄:5%Yb³⁺,0.5%Tm³⁺,10%Ce³⁺,which have the strongest luminous intensity,were assembled in liquid state on the glass substrate and three-dimensional polymethylmethacrylate opal photonic crystals that have different band gaps respectively,then the nanocrystals/three-dimensional photonic crystal composite films were prepared.By measuring the fluorescence spectra of nanocrystalline films and composite nanocrystalline films with different band gaps,analying the regulation of composite films on the luminescence of nanocrystals,regular influence of the band gap structure of photonic crystals and the coupling of excitation field and emission field of Na YF₄nanocrystals on luminescence was obtained.