Preparation And Optical Properties Of Ag-NaYF₄:Yb³⁺,Er³⁺ Composite Nanofibers

At present, rare earth luminescent materials have been widely used in opticaltemperature sensing, medical diagnosis, infrared anti-counterfeiting and stereodisplay. And the metal surface plasmon can enhance and modulate the luminescenceof rare earth. The method of utilizing metal nanoparticles to control rare earthluminescence can take some new characteristics to rare earth luminescent materials.As we know, core-shell nanoparticles is the most commonly studied compositenanomaterials, but the reaction condition is rigorous and the coating thickness is veryhard to control that limit its wide application. In this paper, we introduced the methodof electrospinning to combine metal nanoparticles and luminescent materials tocontrol the rare earth luminescence. The main works are described in the following:(1) The silver nanorices have been prepared by solvothermal method. Use thescanning electron microscope to analyze surface profile of the silver nanorice,research the effect to the surface profile by the different reaction conditions and getthe best reaction condition of the silver nanorices. Use X-ray diffraction to analyzethe structure of the silver nanorice which is consist of cubic and hexagonal phase.And use ultraviolet-visible spectrophotometer to get absorption spectra of the silvernanorices. It shows two absorption peaks at~400nm and~950nm, which areproduced by the surface plasmon resonance to short and long axis of silver nanoricesrespectively.(2) The NaYF4:Yb3+, Er3+nanoparticles have been prepared by solvothermalmethod. Use X-ray diffraction to analyze the structure of NaYF4:Yb3+, Er3+nanoparticles which has pure hexagonal phase. Through the980nm wavelength laserexcitation, we get the upconversion luminescence of NaYF4:Yb3+, Er3+nanoparticles.From the upconversion luminescence spectrum we know that NaYF4:Yb3+, Er3+nanoparticles have green and red upconversion emissions of523,540and660nm,corresponding to the2H11/2â†'4I15/2,4S3/2â†'4I15/2and4F9/2â†'4I15/2transitions of Er3+.(3) The Ag-NaYF4:Yb3+, Er3+composite nanofibers have been prepared by electrospinning method. Mix0,2,6,10,20ml silver nanorices and0.1g NaYF4:Yb3+,Er3+nanoparticles into PVP ethanol solution to get the different spinning solutionsusing for electrospinning. By changing the spinning voltage to prepare differentAg-NaYF4:Yb3+, Er3+composite nanofibers. Use the scanning electron microscope toanalyze surface profile of the composite nanofibers.(4) Use monochromator to check the upconversion luminescence properties ofthe Ag-NaYF4:Yb3+, Er3+composite nanofibers with980nm wavelength laserexcitation. With the increase of the amount of Ag nanorices doping, the upconversionluminescence intensity of Ag-NaYF4:Yb3+, Er3+composite nanofibers was firstincreased and then decreased, the upconversion luminescence red to green intensityratio (Ired/Igreen) was increased. With the increase of pump voltage, the upconversionluminescence intensity of Ag-NaYF4:Yb3+, Er3+composite nanofibers was increased,Ired/Igreenwas increased, too. With the increase of temperature, the upconversionluminescence intensity of Ag-NaYF4:Yb3+, Er3+composite nanofibers was decreased,Ired/Igreenwas increased. With the increase of spinning voltage, the Ired/IgreenofAg-NaYF4:Yb3+, Er3+composite nanofibers was decreased.