Room-temperature spin injection across a chiral perovskite/III-V interface.

Spin accumulation in semiconductor structures at room temperature and without magnetic fields is key to enable a broader range of optoelectronic functionality1. Current efforts are limited owing to inherent inefficiencies associated with spin injection across semiconductor interfaces2. Here we demonstrate spin injection across chiral halide perovskite/III-V interfaces achieving spin accumulation in a standard semiconductor III-V (AlxGa1-x)0.5In0.5P multiple quantum well light-emitting diode. The spin accumulation in the multiple quantum well is detected through emission of circularly polarized light with a degree of polarization of up to 15 ± 4%. The chiral perovskite/III-V interface was characterized with X-ray photoelectron spectroscopy, cross-sectional scanning Kelvin probe force microscopy and cross-sectional transmission electron microscopy imaging, showing a clean semiconductor/semiconductor interface at which the Fermi level can equilibrate. These findings demonstrate that chiral perovskite semiconductors can transform well-developed semiconductor platforms into ones that can also control spin.

Selective Excitation of Exciton-Polariton Condensate Modes in an Annular Perovskite Microcavity.

Exciton-polariton systems composed of a light-matter quasi-particle with a light effective mass easily realize Bose-Einstein condensation. In this work, we constructed an annular trap in a halide perovskite semiconductor microcavity and observed the spontaneous formation of symmetrical petal-shaped exciton-polariton condensation in the annular trap at room temperature. In our study, we found that the number of petals of the petal-shaped exciton-polariton condensates, which is decided by the orbital angular momentum, is dependent on the light intensity distribution. Therefore, the selective excitation of perovskite microcavity exciton-polariton condensates under all-optical control can be realized by adjusting the light intensity distribution. This could pave the way to room-temperature topological devices, optical cryptographical devices, and new quantum gyroscopes in the exciton-polariton system.

Quantifying Chemical Reactions and Interfacial Properties at Buried Polymer/Polymer Interfaces.

Maleic anhydride (MAH)-modified polymers are used as tie layers for binding dissimilar polymers in multilayer polymer films. The MAH chemistry which promotes adhesion is well characterized in the bulk; however, only recently has the interfacial chemistry been studied. Sum frequency generation vibrational spectroscopy (SFG) is an interfacial spectroscopy technique which provides detailed information on interfacial chemical reactions, species, and molecular orientations and has been essential for characterizing the MAH chemistry in both nylon and ethyl vinyl alcohol copolymer (EVOH) model systems and coextruded multilayer films. Here, we further characterize the interfacial chemistry between MAH-modified polyethylene tie layers and both EVOH and nylon by investigating the model systems over a range of MAH concentrations. We can detect the interfacial chemical reaction products between MAH and the barrier layer at MAH concentrations of ≥0.022 wt % for nylon and ≥0.077 wt % for EVOH. Additionally, from the concentration-dependent reaction reactant/product SFG peak positions and the product imide or ester/acid C═O group tilt angles extracted from the polarization-dependent SFG spectra, we quantitatively observe concentration-dependent changes to both the interfacial chemistry and interfacial structure. The interfacial chemistry and molecular orientation as a function of MAH concentration are well correlated with the adhesion strength, providing important quantitative information for the future design of MAH-modified tie layers for a variety of important applications.

A Universal Room-Temperature 3D Printing Approach Towards porous MOF Based Dendrites Inhibition Hybrid Solid-State Electrolytes.

Hybrid solid-state electrolytes (HSSEs) provide new opportunities and inspiration for the realization of safer, higher energy-density metal batteries. The innovative application of 3-dimensional printing in the electrochemical field, especially in solid-state electrolytes, endows energy storage devices with fascinating characteristics. In this paper, effective dendrite-inhibited PEO/MOFs HSSEs is innovatively developed through universal room-temperature 3-dimensional printing (RT-3DP) strategy. The prepared HSSEs display enhanced dendrite inhibition due to the porous MOF filler promoting homogeneity of lithium deposition and the formation of C-OCO3 Li, ROLi, LiF mesophases, which further improve the migration of Li+ in PEO chain and comprehensive performances. This universal strategy realizes the fabrication of different slurry components (PEO with ZIF-67, MOF-74, UIO-66, ZIF-8 fillers) HSSEs at RT environment, providing new inspirations for the exploration of next-generation advanced solid-state batteries.

Investigating the Resistance Mechanism of Wheat Varieties to Fusarium Head Blight Using Comparative Metabolomics.

Fusarium head blight (FHB) is primarily caused by Fusarium graminearum and severely reduces wheat yield, causing mycotoxin contamination in grains and derived products. F. graminearum-secreted chemical toxins stably accumulate in plant cells, disturbing host metabolic homeostasis. We determined the potential mechanisms underlying FHB resistance and susceptibility in wheat. Three representative wheat varieties (Sumai 3, Yangmai 158, and Annong 8455) were inoculated with F. graminearum and their metabolite changes were assessed and compared. In total, 365 differentiated metabolites were successfully identified. Amino acids and derivatives, carbohydrates, flavonoids, hydroxycinnamate derivatives, lipids, and nucleotides constituted the major changes in response to fungal infection. Changes in defense-associated metabolites, such as flavonoids and hydroxycinnamate derivatives, were dynamic and differed among the varieties. Nucleotide and amino acid metabolism and the tricarboxylic acid cycle were more active in the highly and moderately resistant varieties than in the highly susceptible variety. We demonstrated that two plant-derived metabolites, phenylalanine and malate, significantly suppressed F. graminearum growth. The genes encoding the biosynthetic enzymes for these two metabolites were upregulated in wheat spike during F. graminearum infection. Thus, our findings uncovered the metabolic basis of resistance and susceptibility of wheat to F. graminearum and provided insights into engineering metabolic pathways to enhance FHB resistance in wheat.

Ultrasonography and contrast-enhanced ultrasound for activity assessment in 115 patients with carotid involvement of Takayasu arteritis.

OBJECTIVES: To evaluate the efficacy of ultrasound and contrast-enhanced ultrasound (CEUS) in disease activity assessment of Takayasu arteritis (TA) with carotid involvement. METHODS: This is a cohort study of 115 patients of TA with carotid involvement. We investigated correlations between clinical data, sonographic features, and CEUS enhancement at the site most prominent lesion of each patient. Disease activity was assessed by the National Institute of Health Kerr criteria. Sonographic findings were compared with follow-up examinations. CEUS was repeated after a 3-7 months interval in 35 patients to evaluate change of CEUS enhancement after treatment. RESULTS: Extensiveness of CEUS enhancement at most prominent carotid lesions had significant correlations with disease activity by the Kerr criteria (P < .001). The specificity of extensive enhancement for indicating active disease was 95%, while sensitivity was 67%. Patients with active disease showed greater arterial wall thickness and more prominent reduction of arterial wall thickness after treatment. Most of the patients (68%) with subsided active disease after treatment featured decrease of CEUS enhancement. CONCLUSIONS: Extensiveness of enhancement by CEUS and arterial wall thickness by ultrasonography may be useful markers for initial and follow-up assessment of disease activity of TA with common carotid artery involvement.

Correlating Charge-Transfer State Lifetimes with Material Energetics in Polymer:Non-Fullerene Acceptor Organic Solar Cells.

Minimizing the energy offset between the lowest exciton and charge-transfer (CT) states is a widely employed strategy to suppress the energy loss (Eg/q - VOC) in polymer:non-fullerene acceptor (NFA) organic solar cells (OSCs). In this work, transient absorption spectroscopy is employed to determine CT state lifetimes in a series of low energy loss polymer:NFA blends. The CT state lifetime is observed to show an inverse energy gap law dependence and decreases as the energy loss is reduced. This behavior is assigned to increased mixing/hybridization between these CT states and shorter-lived singlet excitons of the lower gap component as the energy offset ΔECT-S1 is reduced. This study highlights how achieving longer exciton and CT state lifetimes has the potential for further enhancement of OSC efficiencies.

Electrochemiluminescent Detection of Proteins Based on Fullerenols Modified Gold Nanoparticles and Triple Amplification Approaches.

In this work, fullerenols were found to be able to enhance the ECL signals of the luminol and H2O2 system and were employed for the first time as a reducing, catalyzing, and stabilizing agent in the one-step fast synthesis of fullerenols@AuNPs in only 5 min. First, the prepared fullerenols@AuNPs were applied to fabricate a label-free immunosensor for the detection of human cardiopathy biomarker (cardiac troponin I, cTnI). Second, using the fullerenols@AuNPs as biolabels to establish a sandwich-type immunosensor and catalyzing in situ copper-stained reaction to generate Cu particles capped on the fullerenols@AuNPs, and then a novel electrochemical stripping chemiluminescent (ESCL) method was developed for detection of cTnI and IgG with about 20 times more sensitive than the former one. At the process of ESCL detection, Cu2+was stripped from Cu@fullerenols@AuNPs with significant increase of the ECL signals. This can be attributed to the fact that the fullerenols@AuNPs nanoparticles and the Cu2+ have excellent conductivity and could facilitate the decomposition of H2O2 to generate various reactive oxygen species (ROSs), thereby accelerating the ECL process. Both immunosensors show high sensitivity and selectivity to cTnI and IgG detection with a wide linear range from fg/mL to ng/mL and the low limits of detection down to fg/mL for cTnI and IgG, respectively.

Electrochemiluminescence detection of cardiac troponin I based on Au-Ag alloy nanourchins.

In this work, an Au-Ag alloy nanourchin (Au-Ag alloy NU) based electrochemiluminescent (ECL) sensor for the measurement of cardiac troponin I (cTnI) was developed. The as-prepared Au-Ag alloy NUs exhibited higher specific surface area and better conductivity owing to their unique urchin-like morphology, which resulted in excellent electrocatalytic activity towards H2O2 in the luminol-H2O2 ECL system. We have found that the Au-Ag alloy NUs could enhance the ECL signal in the luminol-H2O2 solution. Based on these facts, a facile and label-free ECL immunosensor has been constructed for the analysis of cTnI, a cardiac biomarker, with a wide linear range of 3.5 pg mL-1-350 µg mL-1. This novel ECL immunosensor has good stability and reproducibility, showing potential application in clinical diagnostics. In addition, a non-enzymatic electrochemical sensor for H2O2 was also fabricated, with a wide linear detection range of 100 nM-200 µM, a low limit of detection of 45 nM and a fast response time (less than 2 s).

Electron Accumulation Induces Efficiency Bottleneck for Hydrogen Production in Carbon Nitride Photocatalysts.

This study addresses the light intensity dependence of charge accumulation in a photocatalyst suspension, and its impact on both charge recombination kinetics and steady-state H2 evolution efficiency. Cyanamide surface functionalized melon-type carbon nitride (NCNCNx) has been selected as an example of emerging carbon nitrides photocatalysts because of its excellent charge storage ability. Transient spectroscopic studies (from ps to s) show that the bimolecular recombination of photogenerated electrons and holes in NCNCNx can be well described by a random walk model. Remarkably, the addition of hole scavengers such as 4-methylbenzyl alcohol can lead to ∼400-fold faster recombination kinetics (lifetime shortening to ∼10 ps). We show that this acceleration is not the direct result of ultrafast hole extraction by the scavenger, but is rather caused by long-lived electron accumulation in NCNCNx after hole extraction. The dispersive pseudo-first order recombination kinetics become controlled by the density of accumulated electrons. H2 production and steady-state spectroscopic measurements indicate that the accelerated recombination caused by electron accumulation limits the H2 generation efficiency. The addition of a reversible electron acceptor and mediator, methyl viologen (MV2+), accelerates the extraction of electrons from the NCNCNx and increases the H2 production efficiency under one sun irradiation by more than 30%. These results demonstrate quantitatively that while long-lived electrons are essential to drive photoinduced H2 generation in many photocatalysts, excessive electron accumulation may result in accelerated recombination losses and lower performance, and thus highlight the importance of efficient electron and hole extraction in enabling efficient water splitting photocatalysts.

Mechanistic Study of Oxygen Reduction at Liquid/Liquid Interfaces by Hybrid Ultramicroelectrodes and Mass Spectrometry.

Proton-coupled electron transfer (PCET) reactions at various interfaces (liquid/membrane, solid/electrolyte, liquid/liquid) lie at the heart of many processes in biology and chemistry. Mechanistic study can provide profound understanding of PCET and rational design of new systems. However, most mechanisms of PCET reactions at a liquid/liquid interface have been proposed based on electrochemical and spectroscopic data, which lack direct evidence for possible intermediates. Moreover, a liquid/liquid interface as one type of soft interface is dynamic, making the investigation of interfacial reactions very challenging. Herein a novel electrochemistry method coupled to mass spectrometry (EC-MS) was introduced for in situ study of the oxygen reduction reaction (ORR) by ferrocene (Fc) under catalysis from cobalt tetraphenylporphine (CoTPP) at liquid/liquid interfaces. The key units are two types of gel hybrid ultramicroelectrodes (agar-gel/organic hybrid ultramicroelectrodes and water/PVC-gel hybrid ultramicroelectrodes), which were made based on dual micro- or nanopipettes. A solidified liquid/liquid interface can be formed at the tip of these pipettes, and it serves as both an electrochemical cell and a nanospray emitter for mass spectrometry. We demonstrated that the solidified L/L interfaces were very similar to typical L/L interfaces. Key CoTPP intermediates of the ORR at the liquid/liquid interfaces were identified for the first time, and the four-electron oxygen reduction pathway predominated, which provides valuable insights into the mechanism of the ORR. Theoretical simulation has further supported the possibility of formation of intermediates. This type of platform is promising for in situ tracking and identifying intermediates to study complicated reactions at liquid/liquid interfaces or other soft interfaces.

The binding energy and dynamics of charge-transfer states in organic photovoltaics with low driving force for charge separation.

Recent progress in organic photovoltaics (OPVs) has been enabled by optimization of the energetic driving force for charge separation, and thus maximization of open-circuit voltage, using non-fullerene acceptor (NFA) materials. In spite of this, the carrier dynamics and relative energies of the key states controlling the photophysics of these systems are still under debate. Herein, we report an in-depth ultrafast spectroscopic study of a representative OPV system based on a polymer donor PffBT4T-2OD and a small-molecule NFA EH-IDTBR. Global analysis of the transient absorption data reveals efficient energy transfer between donor and acceptor molecules. The extracted kinetics suggest that slow (∼15 ps) generation of charge carriers is followed by significant geminate recombination. This contrasts with the "reference" PffBT4T-2OD:PC71BM system where bimolecular recombination dominates. Using temperature-dependent pump-push-photocurrent spectroscopy, we estimate the activation energy for the dissociation of bound charge-transfer states in PffBT4T-2OD:EH-IDTBR to be 100 ± 6 meV. We also observe an additional activation energy of 14 ± 7 meV, which we assign to the de-trapping of mobile carriers. This work provides a comprehensive picture of photophysics in a system representing new generation of OPV blends with a small driving force for charge separation.

Azimuth Phase Center Adaptive Adjustment upon Reception for High-Resolution Wide-Swath Imaging.

A spaceborne azimuth multichannel synthetic aperture radar (SAR) system can effectively realize high resolution wide swath (HRWS) imaging. However, the performance of this system is restricted by its two inherent defects. Firstly, non-uniform sampling is generated if the pulse repetition frequency (PRF) deviates from the optimum value. Secondly, multichannel systems are very sensitive to channel errors, which are difficult to completely eliminate. In this paper, we propose a novel receive antenna architecture with an azimuth phase center adaptive adjustment which adjusts the phase center position of each sub-aperture to improve multichannel SAR system performance. On one hand, the optimum value of the PRF can be adaptively adjusted within a certain range by adjusting receiving phase centers to obtain uniform azimuth sampling. On the other hand, false targets introduced by residual channel errors after azimuth multichannel error compensation can be further suppressed. The effectiveness of the proposed method to compensate for non-uniform sampling and suppress false targets is verified by simulation experiments.

Fabrication of Tris(bipyridine)ruthenium(II)-Functionalized Metal-Organic Framework Thin Films by Electrochemically Assisted Self-Assembly Technique for Electrochemiluminescent Immunoassay.

A simple strategy for one-step fabrication of tris(bipyridine)ruthenium(II) (Ru(bpy)32+)-functionalized metal-organic framework (Ru-MOF) thin films using a self-assembly approach assisted by an electrochemical way was introduced. In this protocol, the electrochemically driven cooperative reaction of Ru(bpy)32+ as an electrochemiluminescent (ECL) probe and a structure-directing agent, trimesic acid (H3btc) as a ligand, and Zn(NO3)2 as the Zn2+ source leads to an one-step and simultaneous synthesis and deposition of the MOF onto the electrode surface. Characterization of the Ru-MOF thin films was performed with scanning electron microscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy. Scanning ion conductance microscopy was specially applied in situ to image the topography and thickness of the Ru-MOF thin films. The Ru-MOF thin films as a sensing platform show excellent ECL behavior because of plenty of Ru(bpy)32+ molecules encapsulated in the frameworks. On the basis of the Ru-MOF modified electrodes, an ultrasensitive label-free ECL immunosensing method for the human heart-type fatty-acid-binding protein has been developed with a wide linear response range (150 fg mL-1-150 ng mL-1) and a very low limit of detection (2.6 fg mL-1). The prepared immunosensor also displayed excellent stability and good specificity in the test of practical samples.

Triethanolamine-Modified Gold Nanoparticles Synthesized by a One-Pot Method and Their Application in Electrochemiluminescent Immunoassy.

In many electrochemiluminescent (ECL) systems, coreactants play crucial roles in the redox-induced light emission process at the electrode surface. In this work, a novel and environment-friendly nanoplatform for ECL immunosensing enabled by triethanolamine (TEOA)-modified gold nanoparticles (TEOA@AuNPs) is reported. The monodisperse TEOA@AuNPs are fabricated by one-pot synthesis using TEOA as both reducing and stabilizing agent. Then the TEOA@AuNPs-modified electrode not only acted as coreactant for Ru(bpy)32+ ECL system but also provided a carrier for antibody 1 to form label-free immunosensor through an interaction between antigen and antibody. The unique structure of the TEOA@AuNPs loaded a large amount of coreactant of Ru(bpy)32+, which shortened the electron-transfer distance from the AuNPs surface to the appended TEOA molecules, thereby greatly enhancing the ECL efficiency and amplifying the ECL signal. In addition, Ru(bpy)32+-doped silica (RuSiO2) nanoparticles and antibody 2 were combined to form a composite for labels and a sandwich-type ECL immunosensor has been constructed. The possible mechanism of those ECL systems have also been proposed and confirmed by the EC-MS hyphenated technique. The human cardiopathy biomarker, cardiac troponin I (cTnI), was detected in a wide linear concentration range and the limit of detection (LOD) was 34 or 5.5 fg mL-1 by using the proposed label-free or labeling ECL immunoassay method.

Crystallization Inhibition Properties of Cellulose Esters and Ethers for a Group of Chemically Diverse Drugs: Experimental and Computational Insight.

Amorphous solid dispersions are widely used to enhance the oral bioavailability of poorly water-soluble drugs. Polymeric additives are commonly used to delay crystallization of the drug from the supersaturated solutions formed upon ASD dissolution by influencing the nucleation and growth of crystals. However, there is limited evidence regarding the mechanisms by which polymers stabilize supersaturated drug solutions. The current study used experiments and computational modeling to explore polymer-drug interactions in aqueous solutions. Nucleation induction times for supersaturated solutions of nine drugs in the presence of five newly synthesized cellulose-based polymers were evaluated. The polymers had carboxylic acids substituents with additional variations in the side-chain structure: (1) one with a single side chain and a carboxylic acid termination, (2) three with a branched side chain terminated with a carboxylic and an alcohol group (varying the cellulose linkage and the length of the hydrocarbon side chain), and (3) one with a branched side chain with two carboxylic acid end groups. The polymers with a short side chain and one carboxylic acid were effective, whereas the polymers with the two carboxylic acids or a long hydrocarbon chain were less effective. Atomic force microscopy experiments, evaluating polymer adsorption onto amorphous drug films, indicated that the effective polymers were uniformly spread across the surface. These results were supported by molecular dynamics simulations of a polymer chain in the presence of a drug aggregate in an aqueous environment, whereby the effective materials had a higher probability of establishing close contacts and more negative estimated free energies of interaction. The insights provided by this study provide approaches to design highly effective polymers to improve oral drug delivery.

Air-Stable Porous Fe2N Encapsulated in Carbon Microboxes with High Volumetric Lithium Storage Capacity and a Long Cycle Life.

The development of inexpensive electrode materials with a high volumetric capacity and long cycle-life is a central issue for large-scale lithium-ion batteries. Here, we report a nanostructured porous Fe2N anode fully encapsulated in carbon microboxes (Fe2N@C) prepared through a facile confined anion conversion from polymer coated Fe2O3 microcubes. The resulting carbon microboxes could not only protect the air-sensitive Fe2N from oxidation but also retain thin and stable SEI layer. The appropriate internal voids in the Fe2N cubes help to release the volume expansion during lithiation/delithiation processes, and Fe2N is kept inside the carbon microboxes without breaking the shell, resulting in a very low electrode volume expansion (the electrode thickness variation upon lithiation is ∼9%). Therefore, the Fe2N@C electrodes maintain high volumetric capacity (1030 mA h cm-3 based on the lithiation-state electrode volume) comparable to silicon anodes, stable cycling performance (a capacity retention of over 91% for 2500 cycles), and excellent rate performance. Kinetic analysis reveals that the Fe2N@C shows an enhanced contribution of capacitive charge mechanism and displays typical pseudocapacitive behavior. This work provides a new direction on designing and constructing nanostructured electrodes and protective layer for air unstable conversion materials for potential applications as a lithium-ion battery/capacitor electrode.

Phosphorus Enhanced Intermolecular Interactions of SnO2 and Graphene as an Ultrastable Lithium Battery Anode.

SnO2 suffers from fast capacity fading in lithium-ion batteries due to large volume expansion as well as unstable solid electrolyte interphase. Herein, the design and synthesis of phosphorus bridging SnO2 and graphene through covalent bonding are demonstrated to achieve a robust structure. In this unique structure, the phosphorus is able to covalently "bridge" graphene and tin oxide nanocrystal through PC and SnOP bonding, respectively, and act as a buffer layer to keep the structure stable during charging-discharging. As a result, when applied as a lithium battery anode, SnO2 @P@GO shows very stable performance and retains 95% of 2nd capacity onward after 700 cycles. Such unique structural design opens up new avenues for the rational design of other high-capacity materials for lithium battery, and as a proof-of-concept, creates new opportunities in the synthesis of advanced functional materials for high-performance energy storage devices.

Olefin Cross-Metathesis in Polymer and Polysaccharide Chemistry: A Review.

Olefin cross-metathesis, a ruthenium-catalyzed carbon-carbon double bond transformation that features high selectivity, reactivity, and tolerance of various functional groups, has been extensively applied in organic synthesis and polymer chemistry. Herein, we review strategies for performing selective cross-metathesis and its applications in polymer and polysaccharide chemistry, including constructing complex polymer architectures, attaching pendant groups to polymer backbones and surfaces, and modifying polysaccharide derivatives.