Latest ArticlesAchieving stable deep blue organic light emitting diodes (OLEDs) with narrow full width at half maximum (FWHM) and color gamut in the range of the commission International de L'Eclairage (CIE) of y ≤ 0.10 is still challenging in display and lighting applications. In this investigation, three donor-acceptor (D-A) deep-blue emitters were designed and synthesized via integrating asymmetric quinazoline (PQ) acceptor with weak donating carbazole (Cz) donor. The effect of the position and number of Cz group in PQ unit are investigated, which is also first examples for systematic research about the effect of different position of asymmetric PQ as acceptor on deep OLEDs. Their bandgaps of 3.12~3.19 eV and the singlet state energy levels of 3.12~3.19 eV were found to be sufficiently large to achieve deep blue light. As expected, these emitters-based OLEDs exhibit deep blue emission with the maximum wavelength ≤ 450 nm and narrow FWHM ≈ 60 nm. Especially, a CIE of y=0.080 was achieved for 4PQ-Cz-based OLED. Significantly, the deep blue electroluminescence (EL) spectra of these three emitters-based OLEDs are very stable and the corresponding CIE coordinates deviation △CIE (x, y)) can be negligible under the applied voltage ranging from 5 V to 9 V.
For organnoboron compounds, the substituents on boron atoms are very important because they not only impact on the molecular stability but also significantly modulate the electronic structures and properties. In this manuscript, we synthesized two new B←N-containing azaacenes with propynyl groups on boron atoms through one-step Grignard reaction. Replacing fluorine atoms by propynyl groups greatly impacts on the electronic energy levels, especially enhancing the HOMO levels, thus leading to the narrowed HOMO-LUMO bandgaps. These B←N-containing azaacenes exhibit the NIR light-absorption (λabs=706 nm for 2a and 762 nm for 2b) and fluorescence properties (λem=740 nm for 2a and 802 nm for 2b), as well as multiple reversible redox behaviors, which are significantly different from the analogs with fluorine atoms. This study thus provides a functional substituent of boron atom, which may lead to new organoboron materials with fascinating properties.
Partially biobased polysilylethers (PSEs) are synthesized via dehydrocoupling polymerization catalyzed by an anionic iridium complex. Different types (AB type or AA and BB type) of monomers are suitable. Levulinic acid (LA) and succinic acid (SA) have been ranked within the top 10 chemicals derived from biomass. BB type monomers (diols) derived from LA and SA have been applied to the synthesis of PSEs. The polymerization reactions employ an air-stable anionic iridium complex bearing a functional bipyridonate ligand as catalyst. Moderate to high yields of polymers with number-average molecular weights (Mn) up to 4.38× 104 were obtained. A possible catalytic cycle via an Ir-H species is presented. Based on the results of kinetic experiments, apparent activation energy of polymerization in the temperature range of 0-10 ℃ is about 38.6 kJ/mol. The PSEs synthesized from AA and BB type monomers possess good thermal stability (T5=418 ℃ to 437 ℃) and low glass-transition temperature (Tg=-49.6 ℃).
The effective valuation of catalyst supports in the catalytic oxidation makes the contribution to understand the support effect of great interest. Here, the role of active substrate in the performance and stability of Cu-Fe-Co ternary oxides was studied towards the complete catalytic oxidation of CO. The Cu-Fe-Co oxide thin films were deposited on copper grid mesh (CUGM)using one-step pulsed-spray evaporation chemical vapor deposition method. Crystalline structure and morphology analyses revealed nano-crystallite sizes and dome-top-like morphology. Synergistic effects between Cu, Fe and Co, which affect the surface Cu2+, Fe3+, Co3+ and chemisorbed oxygen species (O2- and OH-) of thin films over the active support and thus result in better reducibility. The thin film catalysts supported on CUGM exhibited attractive catalytic activity compared to the ternary oxides supported on inert grid mesh at a high gas hourly space velocity. Moreover, the stability in time-on-stream of the ternary oxides on CUGM was evaluated in the CO oxidation for 30 h. The adopted deposition strategy of ternary oxides on CUGM presents an excessive amount of adsorbed active oxygen species that play an important role in the complete CO oxidation. The catalysts supported on CUGM showed better catalytic conversion than that on inert grid mesh and some literature-reported noble metal oxides as well as transition metal oxides counterparts, revealing the beneficial effect of the CUGM support in the improvement of the catalytic performance.
Developing high efficiency and low cost electrocatalysts is critical for the enhancement of oxygen reduction reaction (ORR), which is the fundamental for the development and commercialization of renewable energy conversion technology. Herein, zinc-nitrogen-carbon (Zn-N-C) was prepared by using biomass resource chitosan via a facile carbon bath method. The obtained Zn-N-C delivered a high specific surface area (794.7 cm2 /g) together with pore volume (0.49 cm3 /g). During the electrochemical evaluation of oxygen reduction reaction (ORR), Zn-N-C displayed high activity for ORR with an onset potential E0=0.96 VRHE and a half wave potential E1/2=0.86 VRHE, which were more positive than those of the commercial 20 wt% Pt/C benchmark catalyst (E0=0.96 VRHE and E1/2=0.81 VRHE). In addition, the ZnN-C catalyst also had a better stability and methanol tolerance than those of the Pt/C catalyst.
The widely accepted theory concerning the electrochemical energy storage mechanism of copper hexacyanoferrate (CuHCF) for supercapacitors is that CuHCF stores charge by the reversible redox processes of Fe3+/Fe2+ couple and Cu cations are electrochemically inactive. In this work, CuHCF nanocubes (CuHCF-NC) were synthesized in the presence of potassium citrate and its electrochemical properties were tentatively studied in 1 mol/L Na2SO4 aqueous electrolyte. Good supercapacitive performance was exhibited. The combined analyses of cyclic voltammogram (CV) and X-ray photoelectron spectroscopy (XPS) disclosed that the CuHCF nanocubes underwent the redox reactions of Fe3+/Fe2+ and Cu2+/Cu+ couples to store charges. The Cu2+/Cu+ redox couple was activated due to the strong coordination interaction between the carboxylate groups of citrate ions and surface Cu cations.
Because of their high capacity and low potential, lithium metal anodes are considered to be promising candidates for next generation electrode materials. However, the safety concerns and limited cycling life associated with uncontrollable dendrite growth hamper practical applications. In this work, the acidified cellulose ester, which is a mixed fiber microporous membrane film, was used as a novel electrolyte additive that effectively improves the cycle stability of the lithium metal anode and inhibits dendrite growth. The focus of this paper is on inhibiting the formation and growth of lithium dendrites. The coulombic efficiency of a Li|Cu battery with this acidified cellulose ester additive remains stable at 99% after 500 cycles under a current density of 1 mA/cm2. Symmetric batteries also remain stable after 500 cycles (1000 h) under a current density of 1 mA/cm2. These superior properties can be ascribed to the induced nucleation and the uniform distribution of lithium ion flux. This study uncovers an approach for effectively enabling stable cycling of dendrite-free lithium metal anodes.
MnS as anode material for sodium-ion batteries (SIBs) has recently attracted great attention because of the high theoretical capacity, great natural abundance, and low cost. However, it suffers from inferior electrical conductivity and large volume expansion during the charge/discharge process, leading to tremendous damage of electrodes and subsequently fast capacity fading. To mitigate these issues, herein, a three-dimensional (3D) interlaced carbon nanotubes (CNTs) threaded into or between MnS hollow microspheres (hollow MnS/CNTs composite) has been designed and synthesized as an enhanced anode material. It can effectively improve the electrical conductivity, buffer the volume change, and maintain the integrity of the electrode during the charging and discharging process based on the synergistic interaction and the integrative structure. Therefore, when evaluated as anode for SIBs, the hollow MnS/CNTs electrode displays enhanced reversible capacity (275 mAh/g at 100 mA/g after 100 cycles), which is much better than that of pure MnS electrode (25 mAh/g at 100 mA/g after 100 cycles) prepared without the addition of CNTs. Even increasing the current density to 500 mA/g, the hollow MnS/CNTs electrode still delivers a five times higher reversible capacity than that of the pure MnS electrode. The rate performance of the hollow MnS/CNTs electrode is also superior to that of pure MnS electrode at various current densities from 50 mA/g to 1000 mA/g.
Highly active N, O-doped hierarchical porous carbons (NOCs) are fabricated through the in-situ polymerization and pyrolysis of o-tolidine and p-benzoquinone. As-prepared NOCs have a variety of faradaic-active species (N-6, N-5 and O-I), high ion-accessible platform (1799 m2 /g) and hierarchically micro-meso-macro porous architecture. Consequently, the resultant NOC electrode delivers an advantageous specific capacitance (311 F/g), with a pseudocapacitive contribution of 37% in a threeelectrode configuration, and an enhanced energy output of 18.0 Wh/kg@350 W/kg owing to the enlarged faradaic effect in an aqueous redox-active cell. Besides, a competitive energy density (74.9 Wh/kg) and high-potential durability (87.8%) are achieved in an ionic liquid (EMIMBF4)-assembled device. This study sheds light on a straightforward avenue to optimize the faradaic activity and nanoarchitecture for advanced supercapacitors.
An ultrasensitive detection and effective removal material was successfully developed by using a pillar[n] arene-based supramolecular polymer gel (MTP5⊃HB). The MTP5⊃HB can ultrasensitively recognize Cu2+ and Fe3+, and the limits of detection (LODs) for Cu2+ and Fe3+ are 1.55 and 2.68 nmol/L, respectively. Additionally, the in-situ generated metallogel MTP5⊃HB-Cu can exclusively detect CN-, and the LOD for CN- is 1.13 nmol/L. Noticeably, the xerogel of MTP5⊃HB-Cu can effectively remove CN- from aqueous solution with 94.40% removal rate. Test kit based on MTP5⊃HB-Cu is also prepared for convenient detection of CN-.
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