ABSTRACT
Near-infrared (NIR) radiation has generated considerable industrial and research interest. However, NIR phosphors for this are limited by low quantum efficiency and broad spectra. Rare-earth-containing compounds doped with activators as host systems for NIR phosphors may resolve these limitations. Yb3+-doped NaY9Si6O26 phosphors were synthesized using a conventional solid-state reaction method. The main phase of the synthesized phosphor samples exhibited a hexagonal structure NaY9Si6O26 phase, and had an angular-shape with an average grain size of 1-3 µm. The NaY9Si6O26:Yb3+ phosphors showed a near-infrared emission from 950 to 1100 nm, which was attributed to the 2F5/2 â 2F7/2 transition of Yb3+ ions under 270 and 920 nm excitation. The excitation spectra, recorded by monitoring the emission at 985 nm, showed two bands in the ultraviolet and infrared regions, which correspond to the charge transfer transition and the 2F7/2 â 2F5/2 transition of Yb3+ ions. At 300 °C, the emission intensity of the NaY9Si6O26:Yb3+ phosphor remained constant at 82%. Furthermore, the thermal degradation was negligible after cooling, suggesting the possibility of application in advanced anti-counterfeiting applications.
ABSTRACT
We demonstrate the crystal phase-selective synthesis for lead-free cesium manganese bromine perovskite nanocrystals synthesized by the modified hot-injection method due to changing the concentration of solvent (trioctylphosphine; TOP). The compositions synthesized were determined by the amount of TOP solvent, and the structure phase of the nanocrystals was selected from hexagonal CsMnBr3 to tetragonal Cs3MnBr5 as the amount of TOP solvent increased. The emission peaks of CsMnBr3 and Cs3MnBr5 nanocrystals were observed at 650â nm (red) and 520â nm (green), respectively. After a durability test at 85°C and 85% humidity for 24â h, the lead-free perovskite CsMnBr3 nanocrystal powder maintained its initial emission intensity, and the metal halide Cs3MnBr5 nanocrystal powder exhibited an increase in red emission due to the post-synthesis of CsMnBr3 nanocrystals.
ABSTRACT
Bi2MoO6:Eu3+ phosphors were synthesized by a solid state reaction, and H2S gas sensing performance was investigated. The Bi2MoO6:Eu3+ phosphors showed an excellent red emission due to f-f transition of Eu3+. Owing to the exposure to H2S gas, the emission intensity of the phosphors dramatically decreased to 40% of the initial value. The body color of the phosphor changed from yellow-white to dark brown. The response of the Bi2MoO6:Eu3+ phosphors for H2S gas was started from 10 ppm, and the emission intensity exponentially decreased with increasing the concentration until 500 ppm.
ABSTRACT
The Ce3+/Tb3+ doped Ba3La2(BO3)4 phosphors were synthesized by a conventional solid state reaction method. The synthesized phosphor samples are a single phase of Ba3La2(BO3)4 and showed angular-shaped fine grains with average particle size from 5 µm to 10 µm. The Ba3La2(BO3)4:Ce3+ phosphors showed an asymmetric broad blue emission under excitation at 365 nm and the Ba3La2(BO3)4:Tb3+ phosphors exhibited typical green emission assigned to the 4f-4f transition of Tb3+ under excitation at 254 nm. Under near-UV (365 nm) excitation, Ba3La2(BO3)4:Ce3+,Tb3+ phosphors showed both a blue emission band and green emission peaks due to Ce3+ and Tb3+, respectively. By optimizing the composition, cyan-blue emission with high color purity (CIE chromaticity coordinate values x = 0.2557 and y = 0.3839) was obtained for the Ba3La2(BO3)4:0.05Ce3+,0.03Tb3+ phosphor, and the internal quantum efficiency of the phosphor at the excitation wavelength of 365 nm is estimated to be 50%. The dental glazing paste prepared by mixing organic binder, Ba3La2(BO3)4:Ce3+,Tb3+ phosphors, and low T g glass was successfully vitrified when it was heated at 600 and 700 °C, and showed high chemical stability of the luminescence properties in acidic aqueous solution (pH = 4).
ABSTRACT
Green-emitting CsPbBr3 perovskite nanocrystals were synthesized by the modified hot-injection method using three different solvents. The produced nanocrystals showed a narrow green emission band centered at 515-520 nm with full width at half-maximum (FWHM) values of approximately 18-20 nm. The highest photoluminescence quantum yield (PLQY) was obtained for the nanocrystal sample synthesized using a paraffin liquid solvent, with a value of 70.1% under excitation at 450 nm. The CsPbBr3 nanocrystals film light-emitting diodes (LED) chip module showed a luminous efficacy of 40.7lm/Wrad. The white LED (WLED) with green CsPbBr3 and red CsPbI3 nanocrystal films emitted bluish-white light with a high color rendering index of 89, and the luminous efficacy of the WLED reached 16.3lm/Wrad.
