Absorbers with lightweight, low filler loading and broad absorption band are highly desirable for electromagnetic wave absorption field. Here, hollow Co1–xS microspheres constructed by nanosheets are ...fabricated via a facile synthetic method based on hydrothermal route. As an efficient wave absorber, the Co1–xS hollow spheres demonstrate excellent microwave absorption performance. With a weight content of only 3 wt%, the maximum reflection loss (RL) can reach as strong as −46.1 dB at 13.92 GHz and its qualified frequency bandwidth (with RL value over −10 dB) remarkably achieves 5.6 GHz, covering 35% of the entire measured bandwidth. In addition, compared with other cobalt sulfides (such as CoS2 and Co9S8), the Co1–xS microspheres with hollow structure exhibit more superior absorption intensity and broader qualified bandwidth. Therefore, this work provides a promising approach for the design and synthesis of hollow Co1–xS microspheres with lightweight and high‐performance microwave absorption.
The hollow Co1–xS microspheres with understanding microwave absorption performance are successfully fabricated through a facile hydrothermal route. The RLmax can reach to −46.1 dB at 13.92 GHz with an ultralow filler loading (3 wt%) and the effective frequency bandwidth is up to 5.6 GHz. Moreover, the possible wave absorption mechanism is also depicted comprehensively in this article.
Actualizing full singlet exciton yield via a reverse intersystem crossing from the high‐lying triplet state to singlet state, namely, “hot exciton” mechanism, holds great potential for ...high‐performance fluorescent organic light‐emitting diodes (OLEDs). However, incorporating comprehensive insights into the mechanism and effective molecular design strategies still remains challenging. Herein, three blue emitters (CNNPI, 2TriPE‐CNNPI, and 2CzPh‐CNNPI) with a distinct local excited (LE) state and charge‐transfer (CT) state distributions in excited states are designed and synthesized. They show prominent hybridized local and charge‐transfer (HLCT) states and aggregation‐induced emission enhancement properties. The “hot exciton” mechanism based on these emitters reveals that a balanced LE/CT distribution can simultaneously boost photoluminescence efficiency and exciton utilization. In particular, a nearly 100% exciton utilization is achieved in the electroluminescence (EL) process of 2CzPh‐CNNPI. Moreover, employing 2CzPh‐CNNPI as the emitter, emissive dopant, and sensitizing host, respectively, the EL performances of the corresponding nondoped pure‐blue, doped deep‐blue, and HLCT‐sensitized fluorescent OLEDs are among the most efficient OLEDs with a “hot exciton” mechanism to date. These results could shed light on the design principles for “hot exciton” materials and inspire the development of next‐generation high‐performance OLEDs.
Full exciton utilization is achieved in the electroluminescence process of 2CzPh‐CNNPI, owing to the balanced distribution of locally excited and charge‐transfer states. Further, this molecule is the first “hot exciton” material that can be employed as the emitter, emissive dopant, and sensitizing host, respectively, and simultaneously achieve high performance in the corresponding blue and host‐sensitized fluorescent organic light‐emitting diodes.
Currently used bioproduction systems for chemicals and fuels are primarily based on sugar-containing substrates. They have inherent limitations regarding substrate sustainability and affordability, ...product spectrum and yield, and costs for up- and downstream processing. To overcome some of these major burdens new bioproduction strategies and systems are being developed, including biorefinery, electro-biotechnology (use of electricity for biosynthesis) and C1 bioeconomy using synthetic biological systems based on C1 carbon feedstocks such as CO, CO2, methane, methanol and formic acid. In this article, the promises, development trends and challenges of these new bioproduction systems and concepts are briefly summarized and discussed.
Non-volatile resistive switching, also known as memristor1 effect, where an electric field switches the resistance states of a two-terminal device, has emerged as an important concept in the ...development of high-density information storage, computing and reconfigurable systems2–9. The past decade has witnessed substantial advances in non-volatile resistive switching materials such as metal oxides and solid electrolytes. It was long believed that leakage currents would prevent the observation of this phenomenon for nanometre-thin insulating layers. However, the recent discovery of non-volatile resistive switching in two-dimensional monolayers of transition metal dichalcogenide10,11 and hexagonal boron nitride12 sandwich structures (also known as atomristors) has refuted this belief and added a new materials dimension owing to the benefits of size scaling10,13. Here we elucidate the origin of the switching mechanism in atomic sheets using monolayer MoS2 as a model system. Atomistic imaging and spectroscopy reveal that metal substitution into a sulfur vacancy results in a non-volatile change in the resistance, which is corroborated by computational studies of defect structures and electronic states. These findings provide an atomistic understanding of non-volatile switching and open a new direction in precision defect engineering, down to a single defect, towards achieving the smallest memristor for applications in ultra-dense memory, neuromorphic computing and radio-frequency communication systems2,3,11.A combination of atomistic imaging and spectroscopy reveals that metal substitution into a sulfur vacancy is the underlying mechanism for resistive switching in transition metal dichalcogenide monolayers.
By adapting the concept of epitaxy to two-dimensional space, we show the growth of a single-atomic-layer, in-plane heterostructure of a prototypical material system—graphene and hexagonal boron ...nitride (h-BN). Monolayer crystalline h-BN grew from fresh edges of monolayer graphene with atomic lattice coherence, forming an abrupt one-dimensional interface, or boundary. More important, the h-BN lattice orientation is solely determined by the graphene, forgoing configurations favored by the supporting copper substrate.
Organic emitters with persistent phosphorescence have shown potential application in optoelectronic devices. However, rational design and phosphorescence tuning are still challenging. Here, a series ...of metal-free luminophores without heavy atoms and carbonyl groups from commercial/lab-synthesized carbazole and benzene were synthesized to realize tunable molecular emission from fluorescence to phosphorescence by simply substituent variation. All the molecules emit blue fluorescence in both solution and solid state. Upon removal of excitation source, the fluorinated luminophores show obvious phosphorescence. The lab-synthesized carbazole based molecules exhibit a huge lifetime difference to the commercially purchased ones due to the existence of isomer in the latter samples. The small energy gap between singlet and triplet state and low reorganization energy help enhance intersystem crossing to contribute to a more competitive radiative process from triplet to ground state. Blue and white organic light-emitting devices are fabricated by using fluorinated luminophore as emitting layer.
Bioconversion of natural microorganisms generally results in a mixture of various compounds. Downstream processing (DSP) which only targets a single product often lacks economic competitiveness due ...to incomplete use of raw material and high cost of waste treatment for by‐products. Here, we show with the efficient microbial conversion of crude glycerol by an artificially evolved strain and how a catalytic conversion strategy can improve the total products yield and process economy of the DSP. Specifically, Clostridium pasteurianum was first adapted to increased concentration of crude glycerol in a novel automatic laboratory evolution system. At m3 scale bioreactor the strain achieved a simultaneous production of 1,3‐propanediol (PDO), acetic and butyric acids at 81.21, 18.72, and 11.09 g/L within only 19 h, respectively, representing the most efficient fermentation of crude glycerol to targeted products. A heterogeneous catalytic step was developed and integrated into the DSP process to obtain high‐value methyl esters from acetic and butyric acids at high yields. The coproduction of the esters also greatly simplified the recovery of PDO. For example, a cosmetic grade PDO (96% PDO) was easily obtained by a simple single‐stage distillation process (with an overall yield more than 77%). This integrated approach provides an industrially attractive route for the simultaneous production of three appealing products from the crude glycerol fermentation broth, which greatly improve the process economy and ecology.
The crude glycerol tolerance and 1,3‐propanediol production of Clostridium pasteurianum were significantly enhanced by subjecting the strain to a novel automatic adaptive laboratory evolution system. A heterogeneous catalytic step was developed and integrated into the downstream process for coproducing high‐value ester of acetic and butyric acids with 1,3‐propanediol. This integrated approach provides an industrially attractive route for simultaneous production of three appealing products from crude glycerol, which greatly improves the process economy and ecology.
Scanning tunneling microscope (STM) has presented a revolutionary methodology to nanoscience and nanotechnology. It enables imaging of the topography of surfaces, mapping the distribution of ...electronic density of states, and manipulating individual atoms and molecules, all at atomic resolutions. In particular, atom manipulation capability has evolved from fabricating individual nanostructures toward the scalable production of the atomic‐sized devices bottom‐up. The combination of precision synthesis and in situ characterization has enabled direct visualization of many quantum phenomena and fast proof‐of‐principle testing of quantum device functions with immediate feedback to guide improved synthesis. Several representative examples are reviewed to demonstrate the recent development of atomic‐scale manipulation, focusing on progress that addresses quantum properties by design in several technologically relevant materials systems. Integration of several atomically precisely controlled probes in a multiprobe STM system vastly extends the capability of in situ characterization to a new dimension where the charge and spin transport behaviors can be examined from mesoscopic to atomic length scale. The automation of atomic‐scale manipulation and the integration with well‐established lithographic processes further push this bottom‐up approach to a new level that combines reproducible fabrication, extraordinary programmability, and the ability to produce large‐scale arrays of quantum structures.
The recent developments in atomic‐scale manipulation with scanning tunneling microscopy (STM) are reviewed. In particular, the review focuses on the progress that addresses quantum properties by design through the precise control of atomic structures in several technologically relevant materials systems. In situ characterization with single‐ and multiprobe STM is discussed, which is utilized for thorough determination of electronic structures.
Social skills are important but difficult to measure. So far, few empirical studies have examined the effect of social skills on the performance of professionals. Using the number of LinkedIn ...connections as a proxy for social skills, we investigate the effect of financial analysts' social skills on their performance. We use multiple ways to validate the measure of social skills and show that analysts with better social skills produce more accurate earnings forecasts and that their stock recommendations elicit stronger market reactions. Furthermore, these socially skilled analysts are more likely to be voted as All‐Star Analysts. This study provides the first large‐sample evidence highlighting the importance of social skills on financial analysts' performance.
Résumé
L'effet des compétences sociales sur la performance des analystes
Les compétences sociales sont importantes, mais difficiles à mesurer. Jusqu’à présent, peu d’études empiriques ont examiné l'effet des compétences sociales sur la performance des professionnels. En utilisant le nombre de relations sur LinkedIn comme indicateur des compétences sociales, les auteurs étudient l'effet des compétences sociales des analystes financiers sur leur performance. Ils utilisent plusieurs moyens pour valider la mesure des compétences sociales et montrent que les analystes ayant de meilleures compétences sociales produisent des prévisions de résultats plus précises et que leurs recommandations en matière d'actions suscitent des réactions plus fortes du marché. De plus, ces analystes socialement compétents sont plus susceptibles d’être élus analystes All‐Star. Les auteurs exposent les conclusions d'une première étude portant sur un vaste échantillon soulignant l'importance des compétences sociales sur la performance des analystes financiers.
Direct synthesis of graphene with well‐defined nanoscale pores over large areas can transform the fabrication of nanoporous atomically thin membranes (NATMs) and greatly enhance their potential for ...practical applications. However, scalable bottom‐up synthesis of continuous sheets of nanoporous graphene that maintain integrity over large areas has not been demonstrated. Here, it is shown that a simple reduction in temperature during chemical vapor deposition (CVD) on Cu induces in‐situ formation of nanoscale defects (≤2–3 nm) in the graphene lattice, enabling direct and scalable synthesis of nanoporous monolayer graphene. By solution‐casting of hierarchically porous polyether sulfone supports on the as‐grown nanoporous CVD graphene, large‐area (>5 cm2) NATMs for dialysis applications are demonstrated. The synthesized NATMs show size‐selective diffusive transport and effective separation of small molecules and salts from a model protein, with ≈2–100× increase in permeance along with selectivity better than or comparable to state‐of‐the‐art commercially available polymeric dialysis membranes. The membranes constitute the largest fully functional NATMs fabricated via bottom‐up nanopore formation, and can be easily scaled up to larger sizes permitted by CVD synthesis. The results highlight synergistic benefits in blending traditional membrane casting with bottom‐up pore creation during graphene CVD for advancing NATMs toward practical applications.
Facile fabrication of large‐area atomically thin membranes by bottom‐up synthesis of nanoporous monolayer graphene is reported. A simple reduction in graphene growth temperature enables facile synthesis of nanoporous graphene. By solution‐casting a hierarchically porous support on the as‐grown nanoporous graphene, large‐area (>5 cm2) nanoporous atomically thin membranes for dialysis applications are demonstrated.
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