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A two-dimensional (2D) lamellar Zn metal–organic framework (Zn-MOF, 1) with a fluorescent 1,6-di(pyridin-3-yl)pyrene (3-DPPy) and 1,4-benzenedicarboxylate (BDC2−) bridging linkers was prepared and structurally characterized. The chemical formula of 1 is [Zn(μ-3-DPPy)(μ-BDC)]n. The mononuclear Zn(II) ion, acting as a node, is tetrahedrally coordinated with two 3-DPPy and two BDC linkers. The coordination environment of Zn(II) is a distorted tetrahedral geometry. The Zn-MOF is the sql network structure based on topology analysis. The undulated 2D sheets of 1 tightly pack together to form a lamellar structure. The pyrene moieties are parallelly oriented to each other. The Zn-MOF is not porous, possibly because the mononuclear Zn(II) node did not form cluster-based secondary building units due to the less symmetric 3-DPPy. The steady-state fluorescence measurements indicate that the fluorescence signal of the 1 is slightly blue-shifted compared to the free 3-DPPy in the solid state. The excimer emission band at 463 nm for crystalline 3-DPPy is shifted to 447 nm for 1. The value of 447 nm is also a blue-shift value compared to nonsubstituted pyrene crystals (470 nm). Despite its nonporosity, the surface Lewis acidic sites of 1 could catalyze the transesterification of esters. Surface defect sites are responsible for this catalytic activity. [ABSTRACT FROM AUTHOR]

Perovskite quantum dots (PQDs), as the promising materials for the blue light-emitting diodes (LEDs), own huge advantages as ultra-high color purity, flexibility and whole-spectrum tunability. Through dimensional and compositional engineering, PQD-LEDs have shown superiority in deep-blue light emission. However, compared with the fast development of red and green PeLEDs, the electroluminescent performance of PQD-LEDs has faced more obstacles. In this review, we aim to explore and state the uniqueness and the possible solutions for the bottleneck problems of the PQD-LEDs. [ABSTRACT FROM AUTHOR]

Electrochemiluminescence (ECL) is a phenomenon in which light is emitted from excited species generated by electrochemical reactions at electrodes. Alternating-current-driven ECL (AC-ECL) devices show good brightness and fast ECL response in comparison to direct-current-driven ECL devices. In this report, we focus on the ECL intensity and long-term stability of blue-light-emitting AC-ECL systems. We used a mixed solvent of propylene carbonate and toluene (volume ratio=1 : 1) to achieve stable blue ECL from 9,10-diphenylanthracene (DPA) molecules. We analyzed the electrochemical, optical, and AC-ECL properties of DPA in this mixed solvent to investigate the effect of the stabilities of redox species on AC-ECL properties. We found that the composition of the electrolyte solution affects the stability of these species. We conclude that stability of generated active species is required to achieve good performance in blue AC-ECL devices. [ABSTRACT FROM AUTHOR]

This study was concerned with the synthesis and properties of new soluble copolyimides containing naphthalene, oxadiazole and tetramethyldisiloxane units. These copolyimides were prepared by two-step polycondensation reaction in solution of aromatic diamines containing preformed oxadiazole ring with a mixture 1 : 1 of naphthalene tetracarboxylic dianhydride and tetramethyldisiloxane- [1,3-bis(4′-phthalic anhydride)]. The structure of these polymers was confirmed by Fourier transform infrared and 1H-NMR spectroscopy. The solubility, thermal stability and glass transition temperature of these copolyimides were measured and compared with those of related polyimides which do not contain siloxane groups. All these polymers emitted an intense blue color light upon irradiation with UV light. These copoly(oxadiazole-naphthylimide)s could be considered promising candidates for organo-soluble high-performance polymers for use in novel technological applications. [ABSTRACT FROM AUTHOR]

As majority of polyheteroarylenes based on bis(naphthalic anhydrides), are difficult to process due to their infusiblity and insolubility in common organic solvents and solubility only in strong acids, this study is concerned with the synthesis and properties of new, easily processable polyimides and copolyimides containing naphthalene and oxadiazole rings. These polymers have been synthesized and their properties have been compared with regard to the influence of oxadiazole and naphthalene units on their physical properties. The polyimides were prepared by polycondensation reaction in solution of the aromatic diamines containing preformed oxadiazole ring with two dianhydrides having naphthalene units, at high temperature. Also, copolyimides were prepared by using a mixture of each naphthalene-containing dianhydride, with hexafluoroisopropylidene-dianhydride in the polycondensation reaction with the same diamino-oxadiazoles. Most of the resulting polyimides and copolyimides were soluble in polar amidic solvents and in less polar solvents, and their solutions gave flexible films when spread onto glass plates. The thermal stability and glass transition temperature of these polyimides and copolyimides were measured and compared. The quality and the roughness of the spin-coated films of these polymers were investigated by atomic force microscopy. The photoluminescence properties of the polymers in solution were studied to determine the color of emission. The UV absorption was also studied to determine the Stokes shift, and hence the possible reabsorption effects. The properties of the present polyimides make them attractive for applications in advanced optoelectronics and other related fields. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Lead‐based perovskite nanocrystals (NCs) are promising candidates for use in lighting and display applications; however, the toxicity of lead is one critical issue that needs to be solved for its commercialization. Consequently, less toxic tin and bismuth‐based perovskite NCs have been developed, but these materials exhibit low photoluminescence quantum yields (PLQYs) and large full width at half maximum (FWHM) values. Due to their similarity in size for Eu2+ and Pb2+, the more environmental‐friendly europium shows the potential to replace lead. Herein, the synthesis of Eu2+ doped CsBr NCs with an average size of 51.5 nm via a facile hot‐injection method is reported. The prepared CsBr:Eu2+ NCs exhibit an emission peak at 440 nm with an FWHM of 31 nm and PLQY up to 32.8%, which is persistent for at least 60 d. Moreover, the size and FWHM of CsBr:Eu2+ NCs can be tuned to 18.9 and 29 nm, respectively, by co‐doping of Ca2+ ions into the NCs. It is also demonstrated that the prepared CsBr:Eu2+ NCs can be employed as efficient color conversion materials for fabricating white light‐emitting diodes. [ABSTRACT FROM AUTHOR]