Preparation And Photoluminescence Properties Of Water-soluble Rare Earth Ions Doped PEI-NaYF₄

Up-conversion luminescence nano-materials of doping rare earth ions have extensive application in many fields such as displays, anti-counterfeiting, etc. With the development of science and technology, nano-materials of doping rare earth ions are expected to be used more widely in the fields of biomarker, medical imaging, environmental monitoring, etc. The nano-materials of doping rare earth ions synthesized in traditional synthesis methods are not water-soluble mostly which can not be combined with organics, which leads to extremely limited application in biology, medicine, environment and so on. Therefore, it is of great research value and practical value to synthesize better water-soluble and functional nano-materials of doping rare earth ions which have a good combination with organics. In this paper, we improved the traditional oil heating method to synthesize water-soluble and functional PEI-NaYF₄ nanoparticles with organic functional groups amino on the surface, and carried on studies on the photoluminescenc e properties of Na YF4 nanoparticles modified by PEI doping of some usual rare earth ions(Er³⁺/Yb³⁺、Tm³⁺/Yb³⁺、Ho³⁺/Yb³⁺), and also synthesized a kind of water-soluble PEI-NaYF₄ nanoparticles of doping Tm³⁺/Ho³⁺/Yb³⁺ with a white upconversion luminescence. The main contents are as follows:First of all, we promoted the traditional oil heating method and synthesized a water-soluble β-PEI-NaYF₄:Er³⁺/Yb³⁺ with a average diameter of about 40 nm and amino groups on the surface, after that we had a discusse on the photoluminescence properties and the luminous mechanism under 980 nm laser excitation. Besides, we also studied the influence of doping concentration of Er³⁺ to the photoluminescence properties of PEI-NaYF₄:Er³⁺/Yb³⁺.Moreover, we synthesized PEI-NaYF₄:Tm³⁺/Yb³⁺ and PEI-NaYF₄:Ho³⁺/Yb³⁺, then made studies on the photoluminescence properties and the luminous mechanism of the upconversion luminescence under 980 nm laser excitation, and analysed the effect of different doping concentrations of Tm³⁺, Ho³⁺ and Yb³⁺ to the upconversion luminescence of PEI-NaYF₄.Finally, we synthesized the water-soluble PEI-NaYF₄ nanoparticles of doping Tm³⁺/Ho³⁺/Yb³⁺ with amino groups on the surface, showing a white upconversion luminescence under 980 nm laser excitation of which the intensity is 518 m W, presenting the wavelength of 475 nm, 540 nm, 646 nm and 693 nm,respectively, with chromaticity coordinate（0.3362,0.3080）. Also, we analysed the trend and causes of the change of color coordinate and studied the effect of changes of the concentration of Yb³⁺ to the white upconversion luminescence of PEI-NaYF₄ nanoparticles of doping Tm³⁺/Ho³⁺/Yb³⁺. Subsequently, we did some studies on the water solution of PEI-NaYF₄ nanoparticles of doping Tm³⁺/Ho³⁺/Yb³⁺ by using the non-thermal coupling level thermometry and obtained the FIR based on non-thermal coupling levels as a function of temperature and the sensitivity base d on thermal coupling levels as a function of temperature as well.