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
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
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)
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
The
morphology and optical and electrical properties of solution-processed
and vacuum-deposited 4,4′,4″-trisÂ(carbazol-9-yl)Âtriphenylamine
(TCTA):2,2′-(1,3-phenylene)ÂbisÂ[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
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
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