Crystal Structures, Thermal and Luminescent Properties of Gadolinium(III) trans-1,4-Cyclohexanedicarboxylate Metal-Organic Frameworks

Four new gadolinium(III) metal-organic frameworks containing 2,2’-bipyridyl (bpy) or 1,10-phenanthroline (phen) chelate ligands and trans-1,4-cyclohexanedicarboxylate (chdc2–) were synthesized. Their crystal structures were determined by single-crystal X-ray diffraction analysis. All four coordination frameworks are based on the binuclear carboxylate building units. In the compounds [Gd2(bpy)2(chdc)3]·H2O (1) and [Gd2(phen)2(chdc)3]·0.5DMF (2), the six-connected {Ln2(L)2(OOCR)6} blocks form a 3D network with the primitive cubic (pcu) topology. In the compounds [Gd2(NO3)2(phen)2(chdc)2]·2DMF (3) and [Gd2Cl2(phen)2(chdc)2]∙0.3DMF∙2.2dioxane (4), the four-connected {Ln2(L)2(X)2OOCR)4} units (where X = NO3– for 3 or Cl– for 4) form a 2D square-grid (sql) network. The solid-state luminescent properties were investigated for the synthesized frameworks. Bpy-containing compound 1 shows no luminescence, possibly due to the paramagnetic quenching by Gd3+ cation. In contrast, the phenathroline-containing MOFs 2–4 possess yellow emission under visible excitation (λex = 460 nm) with the tuning of the characteristic wavelength by the coordination environment of the metal center.

A Cocktail Approach Toward Tunable Organic Afterglow Systems

In this work, a cocktail approach toward tunable organic long-lived luminescence materials in solid, solution, and gel states is proposed. The tunable long-lived luminescence (τ > 0.7 s) is realized by controlling the energy transfer via manipulating the photo-induced isomerization of the energy acceptor (5). The afterglow can be regulated between blue and yellow emission upon irradiation of UV or visible light. And the “apparent lifetime” for the long-lived fluorescence is the same as the lifetime of the energy donor. The function is relying on the simple radiative energy transfer (reabsorption) between a long-lived phosphorescence and a highly efficient fluorescent isomer (5b), rather than the complicated communication between the excited state of the molecules such as Förster resonance energy transfer or Dexter energy transfer. The simple working principle endows this strategy with huge universality, flexibility, and operability. This work offers an extremely simple, feasible, and universal way to construct tunable afterglow materials in solid, solution, and gel states.

Yellow Emissive Tris(8-hydroxyquinoline) Aluminum by the Incorporation of ZnO Quantum Dots for OLED Applications

Tris(8-hydroxyquinoline) aluminum complexes are of significant interest because of their remarkable optical and electrical properties, both as an emissive layer and electron injection layer. They emit light in the blue and green ranges of the visible spectrum, so for white organic light emitting diodes (OLEDs), yellow emission is required as well. In this study, we propose the use of zinc oxide quantum dots to tune the emission color of the complex while maintaining its luminous efficiency. Hence, tris(8-hydroxyquinoline) aluminum-zinc oxide nanohybrids with different zinc oxide quantum dots concentrations (10, 20, or 30 wt.%) were synthesized. The structural properties were characterized using powder X-ray diffraction analysis, while the composition and optical characteristics were characterized by Fourier transform infrared spectroscopy, UV-visible absorption spectroscopy, and photoluminescence emission spectroscopy. The results show that increased levels of zinc oxide quantum dots lead to a decrease in crystallinity, double hump emission and a slight red shift in emission peaks. Also, at 20 and 30 wt.% of zinc oxide quantum dots concentrations, yellow emission was observed.

The Optical Properties of Dy3+ Doped LaPO4 Phosphors Prepared by Solid State Reaction Method

Luminescent nanomaterials are used in everyday life due to their employment in distinct fields of science and technology, like cathode ray tubes (CRTs), flat panel display devices, temperature sensors, lasers, solar-cells, biological imaging, and solid-state lighting but also as carriers for miscellaneous therapeutic drugs. We have prepared dysprosium Dy3+ (0.5 mol %) doped lanthanum phosphate (LaPO4) phosphor by solid state reaction method. The excitation spectra of synthesized phosphor at 595 nm monitoring were composed of broadband and a series of sharp peaks, the strongest excitation peak at 254, 271, and 350 nm. The main emission spectra of samples under 254, 271, and 350 nm excitation are Dy3+ (0.5 mol %) doped LaPO4 phosphor observed at 477 and 573 nm corresponding to blue and yellow color. The broadband emission is the characteristic of the allowed f-h transition of Dy3+ ions. The corresponding emission band is observed due to the (blue emission) 4f9/2→6h15/2, (yellow emission) 4f9/2→6h13/2 transition of Dy3+ ions. All the samples have been characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and photoluminescence (PL) techniques.

Indium-antimony-halide single crystals for high-efficiency white-light emission and anti-counterfeiting

Although single-source white emissive perovskite has emerged as a class of encouraging light-emitting material, the synthesis of lead-free halide perovskite materials with high luminous efficiency is still challenging. Here, we report a series of zero-dimensional indium-antimony (In/Sb) alloyed halide single crystals, BAPPIn2–2xSb2xCl10 (BAPP = C10H28N4, x = 0 to 1), with tunable emission. In BAPPIn1.996Sb0.004Cl10, bright yellow emission with near 100% photoluminescence quantum yield (PLQY) is yielded when it was excited at 320 nm, which turns into bright white-light emission with a PLQY of 44.0% when excited at 365 nm. Combined spectroscopy and theoretical studies reveal that the BAPP4+-associated blue emission and inorganic polyhedron–afforded orange emission function as a perfect pair of complementary colors affording white light in BAPPIn1.996Sb0.004Cl10. Moreover, the interesting afterglow behavior, together with excitation-dependent emission property, makes BAPPIn2–2xSb2xCl10 as high-performance anti-counterfeiting/information storage materials.