Y2O2S:Yb/Ho-silica/aminosilane core-shell nanoparticles were prepared by a solid-gas method in combination with polyvinylpyr-rolidone assisted one-step ammoniating method. The core was a single Y2O2S:Yb/Ho with 80 nm in diameter and the shell was silica/aminosilane with around 5 nm in thickness. The results of sedimentation experiment indicated that the nanoparticles could be well-dispersed in ethanol and water to form stable colloids. Since the coating weakened lattice vibration energies of the Y2O2S:Yb/Ho particles, the proportion of upconversion processes in the depletion of Ho3+ 5I6 level were increased, resulting in increase of green light and decrease of red light.
Yb3+/Tm3+ co-doped and Yb3+/Ho3+/Tm3+ tri-doped tellurite glasses were synthesized by fusing the mixture of TeO2, PbF2, AlF3, BaF2, Yb2O3, Tm2O3 and Ho2O3 in a corundum crucible at 850 oC for 20 min. The synthesized glasses were characterized by upconversion emission spectra under the excitation of 980 nm laser, and the emission colors were investigated according to the CIE-1931 standards. The results indicated that Yb3+/Tm3+ co-doped tellurite glass exhibited blue upconversion emission with favorable color coordinates of(0.20, 0.07). Yb3+, Ho3+ and Tm3+ tri-doped tellurite glasses presented white upconversion luminescence under a single 980 nm laser excitation. Moreover, a very wide range of emission colors could be tuned by altering Ho3+ concentration. Combining the contribution of adjusting Ho3+ concentration and pump power, near equal energy white light was obtained.
Pure γ-Gd 2 S 3 was synthesized by the thermolysis of a single Gd[S 2 CN(C 4 H 8 )] 3 ·phen complex precursor in a flow of argon carrier gas containing sulfur vapor. The complex precursor was decomposed into amorphous Gd 2 S 3 and carbon at about 350 °C. Crystalline γ-Gd 2 S 3 could be achieved at temperature exceeding 600 °C, and the obtained γ-Gd 2 S 3 presented a very high degree of crystallinity at 800 °C. Carbon prevented the formation of Gd 2 O 2 S impurity in the preparation of γ-Gd 2 S 3 . However, the carbon blackened the product. At temperature ≥1000 °C, the residual carbon impurity could be efficiently removed by introducing sulfur into the system for the volatile CS 2 could be formed in situ via the reaction of sulfur with the deposited carbon. In the meantime, S also promoted the crystallization of γ-Gd 2 S 3 remarkablely.
Monodisperse silica/aminosilane-coated Y 2 O 3:Yb,Ho nanoparticles are prepared via homogenous precipitation combined with a polyvinylpyrrolidone-assisted ammoniation method.The factors that contribute to the success of the coating are examined,and the procedure is optimized.Compared with uncoated nanoparticles,coated nanoparticles exhibit an increased ratio of green to red emission intensity,which can mainly be attributed to the decreased number of surface defects induced by the surface coating.
PANG Tao CAO WangHe XING MingMing LUO XiXian XU ShuJing
