Rare Earth Ion Doped Nayf4 Nanomaterials Hydrothermal Synthesis And Spectral Characterization

This thesis is focused on the rare earth ions doped NaYF₄ nanomaterials,including three parts:core/shell nanoparticles,nanorods and water-soluble nanopaticles. A simple and efficient method has been developed for the synthesis ofα-NaYF₄:Nd/α-NaYF₄ core/shell nanoparticles under hydrothermal conditions.The as-prepared products were characterized by powder X-ray diffraction(XRD), transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS), photoluminescence(PL) spectra and lifetimes.TEM images show that the as-prepared samples have sphere-like shape.The lifetime values of the ⁴F_3/2 energy level of theα-NaYF₄:Nd/α-NaYF₄ core/shell nanoparticles increase significantly in comparison with those ofα-NaYF₄:Nd core nanoparticles,with a quantum efficiency of as high as 52%.The Eu³⁺,Tb³⁺,Nd³⁺ and Yb³⁺/Er³⁺ doped hexagonal phase NaYF₄(β-NaYF₄) nanorods were synthesized under hydrothermal conditions and characterized by XRD, scanning electron microscope(SEM),steady photoluminescence spectrum and transient luminescence lifetime measurement.XRD data indicated that the products were of pure hexagonal phase.The nanorods were shown uniform morphology and size with about 400 nm in diameter and about 5μm in length.Visible and NIR photoluminescence emissions were observed from Eu³⁺(or Tb³⁺)-doped and Nd³⁺(or Er³⁺)-doped nanorods.The luminescent decay rate of the Nd³⁺ doped nanorods increased with the Nd³⁺ concentration,and an evident concentration quenching effect was observed.The quantum efficiency ofβ-NaYF₄:1.2%Nd andβ-NaYF₄:10%Yb, 2%nanorods were measured to be 37%and 33%,respectively.Importantly,β-NaYF₄: Yb,Er nanorods displayed both up-conversion and down-conversion luminescence emission under excited under power-tunable 980 nm laser diode.The luminescence mechanism for theβ-NaYF₄:Yb,Er nanorods was analyzed and a normal two-photon upconversion process excited by a 980nm NIR laser was observed.Investagete the possibility to use laurel acid and 11-BUA to take the place of oleic acid to synthesize UCNPs and try to obtain water-soluable naoparticles.