[en] I–VI chalcogenide low-toxicity semiconductors and their near-infrared optical property are of great importance for solar cell and biological probe applications. Here, we report the synthesis of Ag₂S _x Se_{1− x} ( x  = 0–1) ternary nanocrystals (NCs) and their photoelectrochemical properties, using a refined simple hot-injection reaction recipe. The ICP-MS results show the change of non-metallic composition in products and precursors, which can be well fitted with Vegard’s equation. Ternary alloying broadens the absorption spectrum region of Ag₂S NCs. It can also balance the transfer of photo-excited electrons through the interfaces of TiO₂/Ag₂S _x Se_{1− x} and Ag₂S _x Se_{1− x} /electrolyte by minimizing electron–hole recombination. By tuning the compositions, an increase in power conversion efficiency (PCE) was observed with the increase of S composition and the size of the NCs. The photoelectrochemical results reveal that Ag₂S _x Se_{1− x} ternary NCs exhibit higher conversion efficiency than pure binary NCs. The drop in PCE of the binary NCs is mainly attributed to the decreases of the charge separation following exciton transition. (paper)

[en] By controlling the hydrolysis of alkoxysilanes, highly luminescent, transparent and flexible perovskite quantum dot (QD) gels were synthesized. The gels could maintain the structure without shrinking and exhibited excellent stability comparing to the QDs in solution. This in situ fabrication can be easily scaled up for large-area/volume gels. The gels integrated the merits of the polymer matrices to avoid the non-uniformity of light output, making it convenient for practical LED applications. Monochrome and white LEDs were fabricated using these QD gels; the LEDs exhibited broader color gamut, demonstrating better property in the backlight display application. (paper)

[en] LuBO₃:Ln³⁺ (Ln = Eu, Tb) nanofibers were synthesized via electrospinning combined with heat treatment. The structure analyses show that the as-prepared LuBO₃:Ln³⁺ (Ln = Eu, Tb) nanofibers have porous morphology and average diameters of 200-300 nm, which consist of closely lined nanoparticles with the size of about 30 nm. The fluorescence spectra show that the R/O values are 1.02 and 1.12 for LuBO₃:3 mol% Eu³⁺ nanofibers sintered at 800 and 900 C, respectively. For LuBO₃:xTb³⁺ (x = 1, 3, and 5 mol%) nanofibers, the emission intensities and the fluorescence lifetime increase slightly with increasing Tb³⁺ concentration. The fluorescence characteristic of LuBO₃:Ln³⁺ (Ln = Eu, Tb) nanofibers is discussed. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

[en] Highlights: •The phase transition of CaNb₂O₆ was investigated for the first time under high pressure. •In situ Raman spectroscopy and Synchrotron X-ray diffraction were measured. •A pressure-induced reversible phase transition was observed below 23 GPa. •The orthorhombic columbite Pbcn transforms to monoclinic structure P2₁/c. •The lattice parameters of the new phase were obtained by the Pawley refinements. -- Abstract: The in situ high pressure studies of CaNb₂O₆ have been performed using Raman spectroscopy and Synchrotron X-ray diffraction in a DAC up to 23 GPa. Raman experiments show that most Raman peaks decrease in intensity and shift toward high wave numbers with increasing pressure. Two turn points in the slope of frequency–pressure curve of the slopes of Raman modes turn up at the pressure around 8 and 15 GPa. ADXRD results display that the old peaks disappear and some new peaks appear above 9.4 GPa, and the patterns remain unchanged above 15 GPa. Both Raman and X-ray diffraction data provide evidence of a reversible phase transition beginning from about 8 GPa and completing at 15 GPa

[en] Highlights: ► GdBO₃:Ln³⁺ nanofibers were synthesized successfully by electrospinning. ► The samples have the average diameter of 150 nm and the flexible morphology. ► The GdBO₃: Eu³⁺ nanofibers have the stronger orange emission. ► The luminescence properties are different from the reported bulk material. ► We describe the energy transform process of GdBO₃:Ln³⁺ system. - Abstract: GdBO₃:Ln³⁺ (Ln = Eu, Tb) nanofibers were synthesized using electrospinning combined with heat treatment. The synthesized nanofibers were characterized by X-ray diffraction, Raman spectroscopy, field emission-scanning electron microscopy, thermogravimetric and differential thermal analyses, and photoluminescence. The experimental results show that the flexible synthesized nanofibers have an average diameter of approximately 150 nm. The nanofibers consist of crystalline grains with diameters of about 40 nm and have a vaterite-type structure of GdBO₃. The GdBO₃:Eu³⁺ nanofibers exhibit strong orange and weak red emissions with a low ratio of red to orange emission intensities, which is different from those of the reported bulk materials and nanoparticles. The luminescence properties of the synthesized GdBO₃:Tb³⁺ nanofibers are essentially consistent with those of the synthesized GdBO₃:Tb³⁺powders by solid-state reaction.