6 research outputs found

    Evolution of Useless Iron Rust into Uniform α‑Fe<sub>2</sub>O<sub>3</sub> Nanospheres: A Smart Way to Make Sustainable Anodes for Hybrid Ni–Fe Cell Devices

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    The large amount of iron rust yielded in steel industries is undoubtedly a useless and undesired product since its substantial formation and recycle/smelting would give rise to enormous financial costs and environmental pollution issues. To best reuse such rusty wastes, we herein propose a smart and applicable method to convert them into uniform α-Fe<sub>2</sub>O<sub>3</sub> nanospheres. Only after a simple and conventional hydrothermal treatment in HNO<sub>3</sub> solution, nearly all of the iron rust can evolve into sphere-like α-Fe<sub>2</sub>O<sub>3</sub> products with a typical size of ∼30 nm. When serving as actives for electrochemical energy storage, the <i>in situ</i> generated α-Fe<sub>2</sub>O<sub>3</sub> nanospheres exhibit prominent anodic performance, with a maximum specific capacity of ∼269 mAh/g at ∼0.3 A/g, good rate capabilities (∼67.3 mAh/g still retains even at a high rate up to 12.3 A/g), and negligible capacity degradation among 500 cycles. Furthermore, by paring with activated carbons/Ni cathodes, a unique full hybrid Ni–Fe cell is constructed. The assembled full devices can be operated reversibly at a voltage as high as ∼1.8 V in aqueous electrolytes, capable of delivering both high specific energy and power densities with maximum values of ∼131.25 Wh/kg and ∼14 kW/kg, respectively. Our study offers a scalable and effective route to transform rusty wastes into useful α-Fe<sub>2</sub>O<sub>3</sub> nanospheres, providing an economic way to make sustainable anodes for energy-storage applications and also a platform to develop advanced Fe-based nanomaterials for other wide potential applications

    Intersystem Crossing and Triplet Fusion in Singlet-Fission-Dominated Rubrene-Based OLEDs Under High Bias Current

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    Singlet fission is usually the only reaction channel for excited states in rubrene-based organic light-emitting diodes (OLEDs) at ambient temperature. Intriguingly, we discover that triplet fusion (TF) and intersystem crossing (ISC) within rubrene-based devices begin at moderate and high current densities (<i>j</i>), respectively. Both processes enhance with decreasing temperature. This behavior is discovered by analyzing the magneto-electroluminescence curves of the devices. The <i>j</i>-dependent magneto-conductance, measured at ambient temperature indicates that spin mixing within polaron pairs that are generated by triplet-charge annihilation (TQA) causes the occurrence of ISC, while the high concentrations of triplets are responsible for generating TF. Additionally, the reduction in exciton formation and the elevated TQA with decreasing temperature may contribute to the enhanced ISC at low temperatures. This work provides considerable insight into the different mechanisms that occur when a high density of excited states exist in rubrene and reasonable reasons for the absence of EL efficiency roll-off in rubrene-based OLEDs

    Direct Observation of Molecular Orbitals in an Individual Single-Molecule Magnet Mn<sub>12</sub> on Bi(111)

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    Single-molecule nanomagnets have unique quantum properties, and their potential applications require characterization and accessibility of individual single-molecule magnets on various substrates. We develop a gentle tip-deposition method to bring individual prototype single-molecule magnets, manganese-12-acetate (Mn<sub>12</sub>) molecules, onto the semimetallic Bi(111) surface without linker molecules, using low-temperature scanning tunneling microscopy. We are able to identify both the almost flat-lying and side-lying orientations of Mn<sub>12</sub> molecules at 4.5 K. Energy-resolved spectroscopic mapping enables the first observation of several molecular orbitals of individual Mn<sub>12</sub> molecules in real space, which is consistent with density functional theory calculations. Both experimental and theoretical results suggest that an energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the almost flat-lying Mn<sub>12</sub> is only 40% of such a gap for an isolated (free) Mn<sub>12</sub> molecule, which is caused by charge transfer from the metallic surface states of Bi to the Mn<sub>12</sub>. Despite the reduction of this gap, STM images show that the local lattices of Bi(111) covered with Mn<sub>12</sub> remain essentially intact, indicating that Mn<sub>12</sub>–Bi interactions are not strong. Our findings open an avenue to address directly the local structural and electronic properties of individual single-molecule magnets on solid substrates

    High-Efficiency Phosphorescent Hybrid Organic–Inorganic Light-Emitting Diodes Using a Solution-Processed Small-Molecule Emissive Layer

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    The morphology and optical and electrical properties of solution-processed and vacuum-deposited 4,4′,4″-tris­(carbazol-9-yl)­triphenylamine (TCTA):2,2′-(1,3-phenylene)­bis­[5-(4-<i>tert</i>-butylphenyl)-1,3,4-oxadiazole] (OXD-7) composite films are investigated. All of the films exhibit smooth and pinhole-free morphology, while the evaporated films possess enhanced carrier-transport properties compared to solution-processed ones. The close correlation between the carrier-transport feature and the packing density of the film is established. High-efficiency monochromatic and white phosphorescent hybrid organic–inorganic light-emitting diodes with solution-processed small-molecule emissive layers are reported: the maximum external quantum efficiencies of blue, yellow, and red devices are 18.9, 14.6, and 10.2%, respectively; white devices show a maximum luminance efficiency of 40 cd A<sup>–1</sup> and a power efficiency of 20.8 lm W<sup>–1</sup> at 1000 cd m<sup>–2</sup>. The efficiencies of blue, red, and white devices represent significant improvement over previously reported values

    Universal Flexible Lamination Encapsulation Strategy toward Underwater-Operation Electroluminescence Devices

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    A reliable encapsulation technology with scalability and flexibility is urgently needed for electroluminescence devices. Here, we developed a simple, robust, low-cost, and scalable flexible lamination encapsulation strategy with quantum-dot light-emitting diodes (QLEDs) as the model devices. Multilayered Parafilm combining with calcium oxide buffer was used for the lamination encapsulation. We successfully demonstrated that such a Parafilm Lami encapsulation (PLE) not only allowed excellent protection for QLEDs in air but endowed QLED outstanding waterproof performance. As a result, highly efficient and stable flexible waterproof QLEDs were realized based on this PLE, exhibiting maximum external quantum efficiency of ∼8% and long half-luminescence lifetime of over 1.5 h in water. We believe that there are not any obstacles to extending this encapsulation technology to other flexible flat-panel devices, such as organic/perovskite light-emitting diodes

    Universal Flexible Lamination Encapsulation Strategy toward Underwater-Operation Electroluminescence Devices

    No full text
    A reliable encapsulation technology with scalability and flexibility is urgently needed for electroluminescence devices. Here, we developed a simple, robust, low-cost, and scalable flexible lamination encapsulation strategy with quantum-dot light-emitting diodes (QLEDs) as the model devices. Multilayered Parafilm combining with calcium oxide buffer was used for the lamination encapsulation. We successfully demonstrated that such a Parafilm Lami encapsulation (PLE) not only allowed excellent protection for QLEDs in air but endowed QLED outstanding waterproof performance. As a result, highly efficient and stable flexible waterproof QLEDs were realized based on this PLE, exhibiting maximum external quantum efficiency of ∼8% and long half-luminescence lifetime of over 1.5 h in water. We believe that there are not any obstacles to extending this encapsulation technology to other flexible flat-panel devices, such as organic/perovskite light-emitting diodes
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