Ultra-stable perovskite quantum dot composites encapsulated with mesoporous SiO2 and PbBr(OH) for white light-emitting diodes.

Lead halide perovskite quantum dots (QDs) with high fluorescence efficiency and high color purity have a broad application prospect in the field of backlight display, but poor stability has been a key factor limiting their commercialization. Herein, we successfully synthesized CsPbBr3 QDs-KIT-6 (CsPbBr3 -K6) composite by using KIT-6 molecular sieve as the limited template with a simple high temperature solid-phase method. Further, the semi-protected CsPbBr3 QDs in KIT-6 frame will spontaneously hydrolyze when encountering water, and finally the double-encapsulated CsPbBr3 QDs-KIT-6@PbBr(OH) (CsPbBr3 -K6@PbBr(OH)) composite are obtained. CsPbBr3 -K6@PbBr(OH) composite shows excellent green emission properties, including a photoluminescence quantum yield (PLQY) (~73%) and a narrow emission linewidth of 25 nm. It is interesting that, the composite has excellent stability, including water stability without attenuation of fluorescence intensity after soaking in water for 60 days, thermal stability of 120°C heating-cooling cycle, and excellent optical stability without attenuation under continuous ultraviolet irradiation.

One-Step Hydrothermal Synthesis of MoO2/MoS2 Nanocomposites as High-Performance Electrode Material for Supercapacitors.

By only changing the ratio of Mo to S source, a distinctive single phase MoO2 or MoS2 and MoO2/MoS2 nanocomposites (NCs) are obtained through a simple one-step hydrothermal method based on CH4N2S as a sulfur source and (NH4)6Mo7O24·4H2O as a source of Mo in oxalic acid. The effect of ratio of Mo to S source on the composition, structure, and electrochemical performance are systematically researched. Due to its unique design, abundant macropores active sites in MoO2/MoS2 NCs induce superior rate property (55.30% capacitance retention to 20 from 1 A g-1) and larger specific capacitance (1667.3 F g-1 at 1 A g-1) and longer cycle life (94.75% after 5000 cycles) as used directly as an electrode. Furthermore, at a power density of 225 W kg-1, a maximal energy density of 21.85 Wh kg-1 is provided by the asymmetric supercapacitor (MoO2/MoS2//AC). The capacitance of asymmetric supercapacitor (ASC) is remarkably enhanced by 129.02% under 5000 cycles at a current density of 1.5 A g-1, demonstrating outstanding cycle property. These results imply the prepared MoO2/MoS2 NCs have promising applications in advanced energy storages. It is important and should be noted that NCs of oxide and sulfide are prepared with only a simple one-step process.

In-air self-reduction synthesis and luminescence properties from Mg21 Ca4 Na4 (PO4 )18 :Eu2+ -Eu3+ excited using ultraviolet light.

A series of Mg21 Ca4 Na4 (PO4 )18 :Eu2+ -Eu3+ phosphors was successfully synthesized using a high-temperature solid-state method in an air atmosphere. The phase structures and luminescence properties of the samples were studied in detail. The phosphors exhibited strong visible light emission under different wavelengths of ultraviolet light excitation. By harmonizing the doping concentration of Eu3+ to adjust the relative luminescence intensity of Eu2+ and Eu3+ , a colourful emission of phosphors could be achieved. In addition, the colour coordinates of the International Commission on lighting indicated that Mg21 Ca4 Na4 (PO)18 :Eu2+ -Eu3+ could be considered as a potential blue, orange and red phosphor for white light-emitting diode applications.