The Luminescent Properties Of Novel Sc-based Material Sc₂O₃, K₂NaScF₆ And The Upconversion Enhancement Of NaYF₄

(1) Using urea or NH₄HCO₃ as precipitating agent, the Sc（OH）₃ precursors with different morphologieshave been prepared by homogeneous precipitation method. Subsequently, these precursors annealed at 850 °C for 2h to get the Sc₂O₃ microcrystals. Under 980 nm laser excited, we can observe the bright red and green upconversion（UC） emissions from the Sc₂O₃ microcrystals codoping with Yb³⁺/Er³⁺ or Yb³⁺/Ho³⁺ ions pairs. In addition, when Eu³⁺, Tb³⁺ ion doped Sc₂O₃ microcrystals excited by 250 nm or 310 nm ultraviolet light respectively, we can observe intense downconversion（DC） red light and green light. This means earth ions can doped into Sc₂O₃ microcrystals lattice and Sc₂O₃ is an excellent luminescence host material.（2） We used water soluble polyvinylpyrrolidone（PVP） as chelating agents, NH₄F as fluorine source and classic hydrothermal method prepared water soluble cubic K₂NaScF₆. In subsequent experiments, by adjusting the ratio of NH₄F/RE and the amount of PVP, the crystalline phase transform from KSc2F7 to K₂NaScF₆ have been observed. In addition, Yb³⁺/Er³⁺, Yb³⁺/Ho³⁺ and Tb³⁺/Ce³⁺ion pairs have been doped into K₂NaScF₆ NCs successfully.When the K₂NaScF₆ NCs doped with Yb³⁺/Er³⁺ or Yb³⁺/Ho³⁺ ion pairs were excited by 980 nm laser, we can observe bright red or green UC emission light and the K₂NaScF₆ NCs which doped with Tb³⁺/Ce³⁺ ion pairs excited by 260 nm, we can observe green DC emission light clearly.（3） A kind of water dispersed and small particle size（35 nm） hexagonal NaYF₄ NCs are prepared by a new strategy. In this strategy, we use cubic CaF₂ to induce heterogeneous growth of hexagonal phase shells NaYF₄ and using an amphiphilic surfactant, polyvinylpyrrolidone（PVP） as the chelating agent to make our core-shell NCs material have good water solubility and small particle size. In addition, we tune the doping concentration of Tm³⁺ ions to modulate the UC color output from green to yellow, then to red by the naked eye. The intensity ratio of red/green UC emission increases dramatically from 0.1 to 6.2.（4） A series NaYF₄:10 mol%Yb/1 mol%Er/x mol%（x = 0, 2, 4, 6, 8） Hexagonal micro sheet have been prepared by hydrothermal method and Sodium citrate as chelating agents. When these samples excited by 980 nm laser, a bright green light can be observed. When the doping concentration of Ca²⁺ ions increased from 0 to 8 mol%, the UC emissions intensity at different wavelength allshows an intense increase. Moreover, as shown in TEM pictures of these samples, as the increase of Ca²⁺ ions doping concentration, the crystallinity of these samples have different degree increase.（5） Regular spherical Gd₂O（CO₃）₂ precursor have been prepared by homogeneous precipitation method and using urea as precipitating agent, its size is about 120 nm, and then these precursor annealed at 850 °C for 2h to get the Gd₂O₃ microcrystals. In subsequent experiments, we doped the Zn²⁺ ions into Yb³⁺/Er³⁺ or Yb³⁺/Ho³⁺ co-doped Gd₂O₃ nanocrystals and observed a strong enhancement in their UC emission. Among them, the UC emission enhancement of Gd₂O₃:Yb/Er excited by 1560 nm laser is observed for the first time. Moreover, Zn²⁺ ion doping also effect the papamagnetic of Gd₂O₃:Yb/Er and slight increase have been observed.