Xiu Feng Cheng

Luminescence of Cu2+ and In3+ co-activated ZnS nanoparticles

Abstract Zinc sulfide (ZnS) nanoparticles co-doped with Cu2+ and In3+ ions have been prepared by precipitation from homogeneous solutions of zinc, copper and indium salt compounds, with S2− as precipitating anion formed by decomposition of thioacetamide. The estimated average crystallite size of doped and undoped ZnS nanometer scale samples is about 2–3 nm from X-ray diffraction patterns. Novel luminescence characteristics (green emission, λem∼530–550 nm) have been observed from the co-doped ZnS nanocrystals at room temperature. The emission wavelength and relative photoluminescense intensity of the co-doped samples vary with changing the impurity ratios of Cu2+ and In3+.

Preparation and tunable photoluminescence characteristics of Ni2+:SrAl2O4

Abstract Samples of SrAl 2 O 4 and Ni 2+ :SrAl 2 O 4 were prepared by solid states reactions. Microstructures of the samples were analyzed by X-ray diffraction (XRD). The XRD patterns of the undoped sample calcined at 1100 °C reveal that it exhibits a single SrAl 2 O 4 crystalline phase. No characteristic peaks of dopant have been observed in XRD patterns of the doped sample. The tunable photoluminescence (PL) has been observed from the SrAl 2 O 4 sample doped with Ni 2+ ions. The PL spectra of the doped sample are strongly dependent on the excitation energy. The tunable luminescence of the doped sample originates from d–d optical transitions of Ni 2+ (d 8 ) ions in SrAl 2 O 4 .

Strong visible-light emission of ZnS nanocrystals embedded in sol–gel silica xerogel

Abstract ZnS nanoparticles embedded in novel porous phosphor silica xerogel have been synthesized by sol–gel processing. Their fluorescence properties have been evaluated and compared with those of the Na + -doped and un-doped silica xerogels. Stable and strong visible-light emission of the doped samples has been observed. The relative fluorescence intensities of the samples doped with ZnS nanoparticles (S 2− ions have been obtained by the water solution of NaS) are the highest among all of the doped samples. Its relative fluorescence intensity is about 7.5 times of that of the un-doped silica xerogel and about 300 times of that of pure ZnS nanoparticles. The emission wavelength of the ZnS-doped and Na + -doped samples is the same as that of the un-doped silica xerogel and ZnS nanoparticles ( λ em =440–450 nm). This high efficiency luminescence of the doped silica xerogels has been assigned to the luminescence centers of ZnS nanoparticles and Na + in the porous phosphorescence silica xerogel.

Effect of Yb3+ ion on Raman and absorption spectra of Er:Yb:YCa4O(BO3)3 crystals

Abstract Raman-scattering investigations in two crystals, Er:Yb:YCa4O(BO3)3 (EYYCOB) and Er:YCa4O(BO3)3 (EYCOB), show that the Yb3+ ions doped in the crystal largely change the crystal Raman spectra especially those of the Raman tensor elements αXX, αZZ, αXY, and αYZ, which imply the better nonlinear optical properties possible for this crystal as a nonlinear optical material, and these Yb3+ ions due to their influence on the symmetry of some Rare-earth (RE)-O octahedra also change their ligand field, which imply the better laser properties possible for this crystal as a laser material. These Raman measurements also show that the characteristic spectra of the crystals is mainly contributed by the BO3 triangles and partly by the Ca(1)O6 octahedra, which imply that the structural rigidity of the crystals is mainly ascribed to the Bue5f8O bond stretching and bending and partly by the Ca(1)ue5f8O bonds. On the basis of Judd–Ofelt theory, the effect of the sensitizing Yb3+ ions on the absorbance is analyse by comparing with the absorption spectra of EYYCOB and EYCOB. The spectral parameters around the pumping wavelength of an InGaAs diode laser and the luminescence parameters at about 1500 nm also are calculated for the crystal EYYCOB. These indicate that the crystal EYYCOB as a nonlinear optical and laser material would be excellent especially the radiation laser around 1500 nm to be desirable.

Effect of “Ph–NH–CH2–” group on the luminescence properties of sol–gel silica xerogel

Abstract The effect of Ph–NH–CH2– group (Ph: phenyl) on the luminescence properties of silica xerogel by sol–gel method has been investigated. The absorption spectra, excitation spectra and emission spectra of Ph–NH–CH2– group embedded in the network of silica xerogel have a red shift with increasing the ratios of Ph–NH–CH2– group in the samples. The relative photoluminescence (PL) intensity of the hybrid silica xerogel sample decreases with increasing the ratios of Ph–NH–CH2– group. From the complex luminescent centers, the novel luminescence properties have been observed from the hybrid silica xerogel sample containing Ph–NH–CH2– group.