Instability in mixed‐halide perovskites (MHPs) is a key issue limiting perovskite solar cells and light‐emitting diodes (LEDs). One form of instability arises during the processing of MHP quantum ...dots using an antisolvent to precipitate and purify the dots forming surface traps that lead to decreased luminescence, compromised colloidal stability, and emission broadening. Here, the introduction of inorganic ligands in the antisolvents used in dot purification is reported in order to overcome this problem. MHPs that are colloidally stable for over 1 year at 25 °C and 40% humidity are demonstrated and films that are stable under 100 W cm−2 photoirradiation, 4× longer than the best previously reported MHPs, are reported. In LEDs, the materials enable an EQE of 24.4% (average 22.5 ± 1.3%) and narrow emission (full‐width at half maximum of 30 nm). Sixfold‐enhanced operating stability relative to the most stable prior red perovskite LEDs having external quantum efficiency >20% is reported.
Bandgap‐stable and efficient CsPbBrxI3−x perovskite light‐emitting diodes (PLEDs) are demonstrated by adopting an in situ inorganic ligand exchange. This strategy enables bandgap‐stable mixed‐halide perovskites with nanocrystal colloidal stability exceeding 1 year at ambient conditions. The PLEDs exhibit an external quantum efficiency (EQE) of 24.4% and sixfold‐enhanced operating stability relative to the most stable prior red perovskite LEDs having EQEs >20%.
Liquid metal (LM) droplets show the superiority in coalescing into integral liquid conductors applicable in flexible and deformable electronics. However, the large surface tension, oxide shells and ...poor compatibility with most other materials may prevent spontaneous coalescence of LM droplets and/or hybridisation into composites, unless external interventions (e.g., shear and laser) are applied. Here, we show that biological nanofibrils (NFs; including cellulose, silk fibroin and amyloid) enable evaporation-induced sintering of LM droplets under ambient conditions into conductive coating on diverse substrates and free-standing films. The resultants possess an insulating NFs-rich layer and a conductive LM-rich layer, offering flexibility, high reflectivity, stretchable conductivity, electromagnetic shielding, degradability and rapid actuating behaviours. Thus this sintering approach not only extends fundamental knowledge about sintering LM droplets, but also starts a new scenario of producing flexible coating and free-standing composites with flexibility, conductivity, sustainability and degradability, and applicable in microcircuits, wearable electronics and soft robotics.
Abstract
In this paper, we report 591 high-velocity star candidates (HiVelSCs) selected from over 10 million spectra of Data Release 7 (DR7) of the Large Sky Area Multi-object Fiber Spectroscopic ...Telescope and the second Gaia data release, with three-dimensional velocities in the Galactic rest frame larger than 445 km s
−1
. We show that at least 43 HiVelSCs are unbound to the Galaxy with escape probabilities larger than 50%, and this number decreases to eight if the possible parallax zero-point error is corrected. Most of these HiVelSCs are metal-poor and slightly
α
-enhanced inner halo stars. Only 14% of them have Fe/H > −1, which may be the metal-rich “in situ” stars in the halo formed in the initial collapse of the Milky Way or metal-rich stars formed in the disk or bulge but kinematically heated. The low ratio of 14% implies that the bulk of the stellar halo was formed from the accretion and tidal disruption of satellite galaxies. In addition, HiVelSCs on retrograde orbits have slightly lower metallicities on average compared with those on prograde orbits; meanwhile, metal-poor HiVelSCs with Fe/H < −1 have an even faster mean retrograde velocity compared with metal-rich HiVelSCs. To investigate the origins of HiVelSCs, we perform orbit integrations and divide them into four types, i.e., hypervelocity stars, hyper-runaway stars, runaway stars and fast halo stars. A catalog for these 591 HiVelSCs, including radial velocities, atmospheric parameters, Gaia astrometric parameters, spatial positions, and velocities, etc., is available in the China-VO PaperData Repository at doi:
10.12149/101038
.
This work describes a strategy to produce circularly polarized thermally activated delayed fluorescence (CP-TADF). A set of two structurally similar organic emitters SFST and SFOT are constructed, ...whose spiro architectures containing asymmetric donors result in chirality. Upon grafting within the spiro frameworks, the donor and acceptor are fixed proximally in a face-to-face manner. This orientation allows intramolecular through-space charge transfer (TSCT) to occur in both emitters, leading to TADF properties. The donor units in SFST and SFOT have a sulfur and oxygen atom, respectively; such a subtle difference has great impacts on their photophysical, chiroptical, and electroluminescence (EL) properties. SFOT exhibits greatly enhanced EL performance in doped organic light-emitting diodes, with external quantum efficiency (EQE) up to 23.1%, owing to the concurrent manipulation of highly photoluminescent quantum efficiency (PLQY, ∼90%) and high exciton utilization. As a comparison, the relatively larger sulfur atom in SFST introduces heavy atom effects and leads to distortion of the molecular backbone that lengthens the donor–acceptor distance. SFST thus has lower PLQY and faster nonradiative decay rate. The collective consequence is that the EQE value of SFST, i.e., 12.5%, is much lower than that of SFOT. The chirality of these two spiro emitters results in circularly polarized luminescence. Because SFST has a more distorted molecular architecture than SFOT, the luminescence dissymmetry factor (|g lum|) of circularly polarized luminescence of one enantiomer of the former, namely, either (S)-SFST or (R)-SFST, is almost twice that of (S)-SFOT/(R)-SFOT. Moreover, the CP organic light-emitting diodes (CP-OLEDs) show obvious circularly polarized electroluminescence (CPEL) signals with g EL of 1.30 × 10–3 and 1.0 × 10–3 for (S)-SFST and (S)-SFOT, respectively.
Abstract
Melatonin has been characterized as a growth regulator in plants. Melatonin shares tryptophan as the precursor with the auxin indole-3-acetic acid (IAA), but the interplay between melatonin ...and IAA remains controversial. In this study, we aimed to dissect the relationship between melatonin and IAA in regulating Arabidopsis primary root growth. We observed that melatonin concentrations ranging from 10–9 to 10–6 M functioned as IAA mimics to promote primary root growth in Arabidopsis wild type, as well as in pin-formed (pin) single and double mutants. Transcriptome analysis showed that changes in gene expression after melatonin and IAA treatment were moderately correlated. Most of the IAA-regulated genes were co-regulated by melatonin, indicating that melatonin and IAA regulated a similar subset of genes. Melatonin partially rescued primary root growth defects in pin single and double mutant plants. However, melatonin treatment had little effect on primary root growth in the presence of high concentrations of auxin biosynthesis inhibitors, or polar transport inhibitor, and could not rescue the root length defect of the IAA biosynthesis quintuple mutant yucQ. Therefore, we propose that melatonin promotes primary root growth in an IAA-dependent manner.
Modulation of the Arabidopsis transcriptome by melatonin at low concentrations moderately correlates with that of IAA, reflecting their action on primary root growth.
Functional passivators are conventionally utilized in modifying the crystallization properties of perovskites to minimize the non‐radiative recombination losses in perovskite light‐emitting diodes ...(PeLEDs). However, the weak anchor ability of some commonly adopted molecules has limited passivation ability to perovskites and even may desorb from the passivated defects in a short period of time, which bring about plenty of challenges for further development of high‐performance PeLEDs. Here, a multidentate molecule, formamidine sulfinic acid (FSA), is introduced as a novel passivator to perovskites. FSA has multifunctional groups (S≐O, C≐N and NH2) where the S≐O and C≐N groups enable coordination with the lead ions and the NH2 interacts with the bromide ions, thus providing the most effective chemical passivation for defects and in turn the formation of highly stable perovskite emitters. Moreover, the interaction between the FSA and octahedral PbBr64− can inhibit the formation of unfavorable low‐n domains to further minimize the inefficient energy transfer inside the perovskite emitters. Therefore, the FSA passivated green‐emitting PeLED exhibits a high external quantum efficiency (EQE) of 26.5% with fourfold enhancement in operating lifetime as compared to the control device, consolidating that the multidentate molecule is a promising strategy to effectively and sustainably passivate the perovskites.
A multidentate molecule (Formamidine Sulfinic Acid, FSA) to passivate the perovskite for efficient light‐emitting devices. Owing to its multiple roles of guaranteeing sufficient passivation durability and minimizing the energy loss, green PeLEDs based on the FSA‐perovskite films shows a superior EQE of 26.5%.
2D nanomaterials have various size/morphology‐dependent properties applicable in electronics, optics, sensing, and actuating. However, intensively studied inorganic 2D nanomaterials are frequently ...hindered to apply in some particular and industrial fields, owing to harsh synthesis, high‐cost, cytotoxicity, and nondegradability. Endeavor has been made to search for biobased 2D nanomaterials with biocompatibility, sustainability, and biodegradability. A method of hydrophobization‐induced interfacial‐assembly is reported to produce an unprecedented type of nanosheets from marine chitin. During this process, two layers of chitin aggregations assemble into nanosheets with high aspect ratio. With super stability and amphiphilicity, these nanosheets have super ability in creating highly stable Pickering emulsions with internal phase up to 83.4% and droplet size up to 140 μm, in analogue to graphene oxide. Combining emulsifying and carbonization can further convert these 2D precursors to carbon nanosheets with thickness as low as ≈3.8 nm. Having biologic origin, conductivity, and dispersibility in various solvents, resultant carbon nanosheets start a new scenario of exploiting marine resources for fully biobased electric devices with sustainability and biodegradability, e.g., supercapacitor, flexible circuits, and electronic sensors. Hybrid films of chitin and carbon nanosheets also offer low‐cost and environment‐friendly alternative of conductive components desirable in green electronics, wearable electronics, biodegradable circuits, and biologic devices.
A hydrophobization‐induced interfacial assembly method is developed to produce chitin‐based 2D nanomaterials. Having biologic origin, conductivity, and dispersibility in various solvents, these 2D nanomaterials of chitin and carbon start a new scenario of exploiting marine resources for Pickering emulsion and fully biobased electric devices with sustainability and biodegradability, being applicable in green electronics, wearable electronics, biodegradable circuits, and biologic devices.
Extremely soft and thin electrodes with high skin conformability have potential applications in wearable devices for personal healthcare. Here, a submicrometer thick, highly robust, and conformable ...nanonetwork epidermal electrode (NEE) is reported. Electrospinning of polyamide nanofibers and electrospraying of silver nanowires are simultaneously performed to form a homogeneously convoluted network in a nonwoven way. For a 125 nm thick NEE, a low sheet resistance of ≈4 Ω sq−1 with an optical transmittance of ≈82% is achieved. Due to the nanofiber‐based scaffold that undertakes most of the stress during deformation, the electric resistance of the NEE shows very little variation; less than 1.2% after 50 000 bending cycles. The NEE can form a fully conformal contact to human skin without additional adhesives, and the NEE shows a contact impedance that is over 50% lower than what is found in commercial gel electrodes. Due to conformal contact even under deformation, the NEE proves to be a stable, robust, and comfortable approach for measuring electrocardiogram signals, especially when a subject is in motion. These features make the NEE promising for use in the ambulatory measurement of physiological signals for healthcare applications.
A nanonetwork epidermal electrode (NEE) consisting of polyamide‐6 nanofibers and silver nanowires is successfully fabricated by simultaneous conduction of electrospinning and electrospraying. The superb mechanical stability of the NEE is achieved due to its nanofiber‐based scaffold. With the van der Waals interactions, the NEE can form fully conformal contact to human skin to sense electrophysiological signals.
Asp-based lactam cyclic peptides are considered promising drug candidates. However, using Fmoc solid-phase peptide synthesis (Fmoc-SPPS) for these peptides also causes aspartimide formation, ...resulting in low yields or even failure to obtain the target peptides. Here, we developed a diaminodiacid containing an amide bond as a β-carboxyl-protecting group for Asp to avoid aspartimide formation. The practicality of this diaminodiacid has been illustrated by the synthesis of lactam cyclic peptide cycloLys9,Asp13 KIIIA7-14 and 1Y.
In this study, a novel electrochemical non-enzyme sensing platform for glucose detection was fabricated on the basis of shape-controlled Cu2O six corner star-like microcrystal (SCSM) composite doped ...with poly(3,4-ethylenedioxythiophene) (PEDOT)-functionalized multi-walled carbon nanotubes (MWCNTs). The scanning electron microscopy and transmission electron microscopy analysis indicate that the Cu2O SCSMs in the composite show a perfect single crystal structure with six arms and they are bounded with {430} and adjacent high-index facets. Thanks to the Cu2O SCSMs with a high density of active sites and enhanced electron transfer ability of PEDOT-MWCNTs, the prepared Cu2O SCSM/PEDOT-MWCNTs exhibit higher electrocatalytic activity toward glucose oxidation compared to the other counterpart electrodes. On the basis of the Cu2O SCSM/PEDOT-MWCNTs composite, the non-enzymatic amperometric sensing of glucose has been successfully realized in 0.1 M NaOH at 0.5 V with a short response time (<4 s), a low detection limit (0.04 μM, S/N = 3) and a wide linear response concentration range of 4.95 × 10−4–0.374 mM and 0.374–3.446 mM. Moreover, the proposed amperometric sensor presents high sensitivity as well as excellent reproducibility, long term stability and selectivity, suggesting the potential applicability of the sensor for glucose detection.
•A novel Cu2O six corner star-like microcrystal (SCSM) on PEDOT-MWCNTs is synthesized.•A non-enzyme glucose sensor based on Cu2O SCSM/PEDOT-MWCNTs is fabricated.•The Cu2O SCSMs with a yield above 90% are distributed uniformly in the PEDOT-MWCNTs.•The Cu2O SCSMs are bounded with {430} and adjacent high-index facets.•The fabricated sensor exhibits excellent performance for glucose monitoring.
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