Photoluminescence Properties of SrMoO4:Eu3+, Sm3+ Nanophosphors Prepared by Sol-Gel Method.

Novel red light-emitting nanophosphors of SrMoO4:Eu3+, Sm3+ were synthesized by a facile sol-gel method. Particles have sizes in the range of 50-80 nm. The structures, morphologies and optical properties of as-prepared products were characterized by means of X-ray diffraction (XRD), transmission electron microscope (TEM) and photo luminescent (PL). The results indicate that the red emission intensity was enhanced significantly with the increase of Sm3+ doping concentrations. When the mole fraction of Sm3+ is 2%, the emission intensity of red light is the strongest. It has been found that the incorporation of R+(Li+, Na+) into SrMoO4:Eu3+, Sm3+ phosphor could lead to a remarkable increase of photoluminescence. Thus, it is considered to be efficient red-emitting phosphors.

Photoluminescence of CaxSr(1-x) (NbO3)2:Pr3+ (0 < or = x < or = 1) nanophosphors.

Nanoparticles of CaxSr(1-x) (NbO3)2 doped with Pr3+ have been synthesized by sol-gel method. Particles have sizes in the range of 50-70 nm. The CaxSr(1-x) (NbO3)2:Pr3+ phosphors showed a white emission under the near-ultraviolet excitation (254 nm). There is a large photoluminescence enhancement of the CaxSr(1-x) (NbO3)2:Pr3+ phosphor samples when added with 0.5% KCl. X-ray diffraction (XRD), transmission electron microscope (TEM), photo luminescent (PL) analysis were utilized to characterize the CaxSr(1-x) (NbO3)2:Pr+ particles. The concentration quenching of the samples was discussed as well. The optical concentration and the calcination temperature were 0.8 mol% of Ca2+ and 900 degrees C for these phosphors, respectively, the possible mechanism was discussed. CaxSr(1-x) (NbO3)2:Pr3+ is a promising white phosphor under near-ultraviolet excitation for various applications.

In-dopants effect on the photoluminescence properties of YVO4 nanophosphors.

The powders of Yttrium vanadate (YVO4) with In-dopants were synthesized by solid-state reactions, and X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) absorption spectra, photoluminescence (PL) spectra, and the luminescence intensity change were used to characterize the samples. The results of XRD indicated that the YVO4:In3+ samples remained in pure cubic phase. TEM illustrated that the powders mainly consisted of grains with an average size of 100 nm. Under the excitation of 320 nm, the YVO4:In3+ single-crystalline samples exhibited emission ranging from 350 to 700 nm. The emission intensity of YVO4:In3+ increased with increasing indium concentration in the lower indium concentration region until the saturated PL intensity was reached, and the strongest white fluorescence was observed when the In3+ doping concentration was 2% at 900 degrees C. The luminescent intensity of YVO4:In3+ (2%) was 9.6 times as strong as that of non-doped YVO4. The nanophosphors emit white luminescence owing to broad charge transfer in crystal lattice is due to the addition of In3+ to capture the UV radiation.

Structural phase transition of tungsten-doped vanadium dioxide nanopowders prepared by thermolysis.

Tungsten-doped vanadium dioxide (VO2) nanopowders were prepared by thermolysis of (NH4)5[(VO)6(CO3)4(OH)9] x 10H2O at low temperature, with active white powdery tungstic acid used as a substitutional dopant. The composition and microstructure of the powders were examined by X-ray diffraction, transmission electron microscope, and differential scanning calorimetry. The change in electrical resistance due to the S-M transition was measured from 0 to 150 degrees C by the four-probe method. Hysteresis loops and differential scanning calorimetry analysis of the samples indicated that the phase-transition temperature of VO2 nanopowders was 67.15 degrees C. For tungsten-doped VO2 nanopowders, the temperature was reduced to 26.46 degrees C. After sintering the nanopowders, Tc rose from 26.46 degrees C to 34.85 degrees C with the sizes increasing to the bulk. A significant direct correlation between particle size and Tc was confirmed. The results indicated that white powdery tungstic acid is exceptionally effective as a dopant for reducing transition temperature.

Synthesis and luminescent properties of a novel bluish-white afterglow phosphor, b-Zn3(PO4)2:Hf4+.

A new bluish-white long-lasting phosphorescent material, Hf4+-doped b-Zn3(PO4)2, was prepared by the conventional high-temperature solid-state method. The photoluminescence (PL) spectrum reveals that it exhibits a strong blue emission band centred at 470 nm, with asymmetry on the long wavelength side; this material emits bluish-white light and shows strong afterglow phosphorescence after it is excited with a 254 nm UV lamp. The phosphorescence lasts nearly 40 min in the light perception of the dark-adapted human eye (0.32 mcd/m(2)). The possible phosphorescence mechanism is also analysed.