Transparent near-infrared perovskite light-emitting diodes.

Mobile and wearable devices are increasingly reliant on near-infrared (NIR) covert illumination for facial recognition, eye-tracking or motion and depth sensing functions. However, these small devices offer limited spatial real estate that is typically already occupied by their full-area electronic color displays. Here, we report a transparent perovskite light-emitting diode (LED) that could be overlaid across a color display to provide an efficient and high-intensity NIR illumination. Our transparent devices are constructed with an ITO/AZO/PEIE/FAPbI3/poly-TPD/MoO3/Al/ITO/Ag/ITO architecture, and offer a high average transmittance of more than 55% across the visible spectral region. In particular, our Al/ITO/Ag/ITO top transparent electrode was designed to offer a combination low sheet resistance and low plasma damage upon electrode deposition. The devices emit at 799 nm with a high total external quantum efficiency of 5.7% at a current density of 5.3 mA cm-2 and a high radiance of 1.5 W sr-1 m-2, and possess a large functional device area of 120 mm2. The efficient performance is ideal for battery-powered wearable devices, and could enable advanced security and sensing features on future smart-watches, phones, gaming consoles and augmented or virtual reality headsets.

Thermal Instability Induced Oriented 2D Pores for Enhanced Sodium Storage.

Hierarchical porous structures are highly desired for various applications. However, it is still challenging to obtain such materials with tunable architectures. Here, this paper reports hierarchical nanomaterials with oriented 2D pores by taking advantages of thermally instable bonds in vanadium-based metal-organic frameworks (MOFs). High-temperature calcination of these MOFs accompanied by the loss of coordinated water molecules and other components enables the formation of orderly slit-like 2D pores in vanadium oxide/porous carbon nanorods (VOx /PCs). This unique combination leads to an increase of the reactive surface area. In addition, optimized VOx /PCs demonstrate high-rate capability and ultralong cycling life for sodium storage. The assembled full cells also show high capacity and cycling stability. This report provides an effective strategy for producing MOFs-derived composites with hierarchical porous architectures for energy storage.

Yolk-Shell MnO@ZnMn2 O4 /N-C Nanorods Derived from α-MnO2 /ZIF-8 as Anode Materials for Lithium Ion Batteries.

Manganese oxides (MnOx ) are promising anode materials for lithium ion batteries, but they generally exhibit mediocre performances due to intrinsic low ionic conductivity, high polarization, and poor stability. Herein, yolk-shell nanorods comprising of nitrogen-doped carbon (N-C) coating on manganese monoxide (MnO) coupled with zinc manganate (ZnMn2 O4 ) nanoparticles are manufactured via one-step carbonization of α-MnO2 /ZIF-8 precursors. When evaluated as anodes for lithium ion batteries, MnO@ZnMn2 O4 /N-C exhibits an reversible capacity of 803 mAh g-1 at 50 mA g-1 after 100 cycles, excellent cyclability with a capacity of 595 mAh g-1 at 1000 mAg-1 after 200 cycles, as well as better rate capability compared with those non-N-C shelled manganese oxides (MnOx ). The outstanding electrochemical performance is attributed to the unique yolk-shell nanorod structure, the coating effect of N-C and nanoscale size.

Tricarboxylate-based Gd(III) coordination polymers exhibiting large magnetocaloric effects.

Two Gd(III) coordination polymers with the formula [Gd(cit)(H2O)]∞ () and [Gd(nta)(H2O)2]∞ () (H4cit = citric acid, H3nta = nitrilotriacetic acid) have been successfully prepared under hydrothermal conditions. Complex exhibits a three-dimensional (3D) structure based on carboxylate-bridged layers, while complex is a double-layer structure containing eight-coordinated Gd(III). Magnetic investigations reveal that weak antiferromagnetic couplings between adjacent Gd(III) ions in both and with different Weiss values result in large cryogenic magnetocaloric effects. It is notable that the maximum entropy changes (-ΔS) of and reach 31.3 J kg(-1) K(-1) and 32.2 J kg(-1) K(-1) at 2 K for a moderate field change (ΔH = 3 T), and a remarkable -ΔS (41.5 J kg(-1) K(-1) for and 42.0 J kg(-1) K(-1) for ) could be obtained for ΔH = 7 T.

Cobalt oxide 2D nano-assemblies from infinite coordination polymer precursors mediated by a multidentate pyridyl ligand.

In this work, the construction of Co3O4 two dimensional (2D) nano-assemblies utilizing infinite coordination polymers (ICPs) as precursors was investigated, aiming at the morphology targeted fabrication and utilization of 2D materials. Based on the successful modulation of morphology, a rose-like Co based ICP precursor was obtained, which was further transformed into porous Co3O4 nanoflake assemblies with a well-preserved 2D morphology and a large surface area. The mechanism of the morphology modulation was illustrated by systematic investigation, which demonstrated the crucial role of a modulating agent in the formation of 2D nano-assemblies. In addition, the cobalt oxide 2D nano-assemblies are fabricated into a lithium anode combined with graphene, and the remarkable capacity and stability (900 mA h g(-1) after 50 cycles) of the resulting Co3O4/G nanocomposite indicates its potential in lithium battery applications.

Low-dimensional carboxylate-bridged Gd(III) complexes for magnetic refrigeration.

Four carboxylate-bridged Gd(III) complexes (1-4) with 1D/2D structures have been synthesized by using the hydrothermal reaction of Gd2O3 with various carboxylate ligands. Compounds 1 and 2 contained the same [2n] Gd(III)-OH ladders, but with different crystallographically independent Gd(III) ions, whilst the structures of compounds 3 and 4 were composed of [Gd4(µ3-OH)2(piv)8(H2O)2](2+) units and 1D ladder Gd(III) chains, respectively. Antiferromagnetic interactions occurred in compounds 1-3, owing to their small Gd-O-Gd angles, whereas ferromagnetic coupling occurred in compound 4, in which the Gd-O-Gd angles were larger. These complexes exhibited a distinct magnetocaloric effect (MCE), which was affected by their different magnetic densities and exchange interactions. Among these compounds, complex 4 presented the largest MCE (-ΔS(m)(max)=43.6 J kg(-1) K(-1)), the lowest M(w)/N(Gd) ratio (the highest magnetic density), and weak ferromagnetic coupling. Therefore, a lower M(w)/N(Gd) ratio and weaker exchange interactions (a smaller absolute value of θ) between Gd(III) ions resulted in a larger MCE for the Gd(III) complexes.