Stability of Quantum-Dot Light Emitting Diodes with Alkali Metal Carbonates Blending in Mg Doped ZnO Electron Transport Layer

We report here the fabrication of highly efficient and long-lasting quantum-dot light emitting diodes (QLEDs) by blending various alkali metal carbonate in magnesium (Mg) doped zinc oxide (ZnO) (MZO) electron transport layer (ETL). Alkali metal carbonates blending in MZO, X2CO3:MZO, control the band-gap, electrical properties, and thermal stability. This can therefore enhance the operational lifetime of QLEDs. It is found that the conductivity of X2CO3:MZO film can be controlled and the thermal stability of ETLs could be improved by X2CO3 blending in MZO. The inverted red QLEDs (R-QLEDs) with Cs2CO3:MZO, Rb2CO3:MZO, and K2CO3:MZO ETLs exhibited the operational lifetime of 407 h for the R-QLEDs with Cs2CO3:MZO, 620 h with Rb2CO3:MZO and 94 h with K2CO3:MZO ETLs at T95 with the initial luminance of 1000 cd/m2. Note that all red QLEDs showed the high brightness over 150,000 cd/m2. But the R-QLEDs with Na2CO3:MZO and Li2CO3:MZO ETLs exhibited shorter operational lifetime and poor brightness than the R-QLED with pristine MZO ETL.

RbKLi2[Li3SiO4]4:Eu2+ an ultra narrow-band phosphor

The new phosphor RbKLi2[Li3SiO4]4:Eu2+ was synthesized by different high-temperature solid-state reactions. It is accessible from the alkali metal carbonates, SiO2, and Eu2+ as a luminous active cation either in closed tantalum ampoules or by conventional solid-state reaction in nickel crucibles, under a constant flow of forming gas. The structure of the thereby received rod-shaped crystals was solved and refined on the basis of single crystal X-ray diffraction data. The compound crystallizes isostructurally to CsKNa2[Li3SiO4]4 and forms a highly condensed network of LiO4 and SiO4 tetrahedra [I4/m (no. 87), Z = 2, a = 10.9508(6) and c = 6.3334(3) Å]. It is a new member of the recently discovered family of alkali lithosilicate phosphors. Under excitation with UV to blue light, the compound exhibits interesting luminescence properties. Depending on the mode of synthesis, either green or blue luminescence of the samples is observed. Both emission profiles can be described as ultra-narrow-banded, since the full width at half maximum (fwhm) is below 0.2 eV. The green phosphor shows an emission maximum at 532 nm with a fwhm of 43.5 nm (0.193 eV) and the blue one at 474 nm with a fwhm of 24.8 nm (0.137 eV). Furthermore, the material presented here allows a more detailed localization of the luminescence center inside the structure, which may allow a better understanding of the luminescence properties of many other alkali lithosilicate phosphors.

SYNTHESIS OF STABLE ATЕ-COMPLEXES OF HETEROAROMATIC BORONIC ACIDS AND 4,6,10-TRIHYDROXY-1,4,6,10-TETRAAZAADAMANTANE

In this article synthesis of stable ate complexes of heteroaromatic boronic acids and 4,6,10-trihydroxy-1,4,6,10-tetraazaadamantane is described. Ate complexes that have betaine structure were prepared by reaction of tris(β-oximinomethyl)amine with 3-pyridinylboronic and 2-thienylboronic acids. Modification of this method consists in usage of alkali metal carbonates as an additional base. This improvement makes it possible to synthesize ate complexes of 3-thienylboronic and 2-furanylboronic acids which are resistant to air-moisture and have improved thermal stability. All substances were synthesized with nearly quantitative yields and characterized by 1H, 13С (DEPT 135) and 11B NMR spectroscopy; elemental analysis and HRMS. According to spectral data, all ate complexes have cage structure and do not have any traces of free heterocyclic boronic acids in NMR spectra. In this article we also demonstrate that such stable ate complexes can be used for covalent immobilization of heterocyclic boronic acids on polymeric matrix. On the first stage polystyrene that contains 4-(benzyloxy)benzyl bromide residues was modified by 4,6,10- tetraazaadamntane fragments. Then, derived material was treated with 3-thienylboronic acid. Novel polymer contains boronic acid in the form of covalently bound ate complex. This polymer has 40% loading according to elemental analysis. We confirmed presence of covalently bound residues of 3-thienylboronic acid and diamantane fragments by comparison of experimental and calculated FTIR spectra. Such polymers can be used for separation of boronic acids from reaction mixtures and in solid phase synthesis.

A mechanism of alkali metal carbonates catalysing the synthesis of β-hydroxyethyl sulfide with mercaptan and ethylene carbonate

The activation mechanism of the synthesis of β-hydroxyethyl sulfide with ethylene carbonate and thiol catalysed by M2CO3 has been studied.

Versatile porous graphene flakes derived from alkali metal carbonates using an ultrafast and sulfuric acid-free solid-state oxidation reaction

We report a H2SO4-free, alkali metal carbonate (M2CO3) based solid-state reaction, which offers an ultra-fast, effective method for the synthesis of single-layered graphene oxide (GO).