Preparation And Luminescence Properties Of Nano Green Phosphor Under VUV Excitation

For advancing display device technology, fine particle phosphors which have smaller particle size and more uniform particle shape than those present commercial phosphors are required. In this paper, we synthesized manganese doped silicate and rare earth doped fluoride nano-phosphor via hydrothermal route. The main work focused on the improvement of photoluminescence (PL) properties of traditional Zn2SiO4:Mn2+ phosphor in nano scale. In addition, the unique PL properties of nano phosphor under vacuum ultraviolet (VUV) excitation were also discussed. On the other hand, the VUV PL properties of rare earth doped fluoride nanophosphors were selected and studied.1.Nanoscaled hexagonal Zn2SiO4:Mn2+ green phosphor with regular and uniform morphology was synthesized by hydrothermal method at a low temperature of 140℃, which was the lowest synthesize temperature that ever reported. The as-synthesized nanophosphor exhibited intensive broad emission around 523nm, which was attributed to the 4T1-6A1 transition of Mn2+. When the cetyltrimethyl ammonium bromide (CTAB) as the surfactant molecules was adopted into the hydrothermal procedure, the morphology and the particle size of the phosphor could be controlled. The uniform spherical nanoparticles exhibited the strongest broad emission. Series of Zn2-xSiO4:xMn2+ nanophosphors with different particle size were producted when the condition of the hydrothermal changed. It was found that the highest concentration quenching occurred in the series of Zn2-xSiO4:xMn2+ nanophosphor with the smallest particle size, and the decay time of Mn2+ prolongered with the decrease of particle size due to size effect in nano-materials.2. Heat-treatment and codoping other ions could improve the PL properties of the hydrothermal production. After the heat-treatment, PL intensity of the Zn2SiO4:Mn2+ nanophosphor increased along with the elongered decay time, while still keeping the monodispersed spherical morplogy. The decay time of Mg2+ codoped Zn2SiO4:Mn2+ is 4.981 ms, is much shorter than the commercial bulk phosphor. The PL intensity of Zn2SiO4:Mn2+,Ca2+ nanophosphor was 107% of that of commercial bulk phosphor.3.Hexagonal NaYF4:Tb3+ nanophosphor with well dispersed morphology was synthesized by the hydrothermal route. With the increasing reduction temperature, the hexagonal NaYF4 (β-NaYF4) was gradually replaced by cubic NaYF4(a-NaYF4). Tb3+ doped cubic NaYF4 exhibited intensive green PL under VUV or ultraviolet (UV) excitation. The green emission of Tb3+ in cubic NaYF4 was obviously improved with Ce3+ codoped due to the energy transfer procedure under UV excitation. Nano Hexagonal NaYF4:Ln3+(Ln=Sm, Dy) exhibit excellent PL properties under VUV or UV excitation.