Abstract
As a quantum material, Weyl semimetal has a series of electronic-band-structure features, including Weyl points with left and right chirality and corresponding Berry curvature, which have ...been observed in experiments. These band-structure features also lead to some unique nonlinear properties, especially high-order harmonic generation (HHG) due to the dynamic process of electrons under strong laser excitation, which has remained unexplored previously. Herein, we obtain effective HHG in type-II Weyl semimetal β-WP
2
crystals, where both odd and even orders are observed, with spectra extending into the vacuum ultraviolet region (190 nm, 10th order), even under fairly low femtosecond laser intensity. In-depth studies have interpreted that odd-order harmonics come from the Bloch electron oscillation, while even orders are attributed to Bloch oscillations under the “spike-like” Berry curvature at Weyl points. With crystallographic orientation-dependent HHG spectra, we further quantitatively retrieved the electronic band structure and Berry curvature of β-WP
2
. These findings may open the door for exploiting metallic/semimetallic states as solid platforms for deep ultraviolet radiation and offer an all-optical and pragmatic solution to characterize the complicated multiband electronic structure and Berry curvature of quantum topological materials.
Herein, we describe the development of a copper‐catalyzed C(sp3)‐amination of proaromatic dihydroquinazolinones derived from ketones. The reaction is enabled by the intermediacy of open‐shell species ...arising from homolytic C−C bond‐cleavage driven by aromatization. The protocol is characterized by its operational simplicity and generality, including chemical diversification of advanced intermediates.
Herein, we describe the development of a copper‐catalyzed C(sp3)‐amination of proaromatic dihydroquinazolinones derived from ketone building blocks. The reaction is enabled by the intermediacy of open‐shell species arising from homolytic C−C bond‐cleavage driven by aromatization. The protocol is characterized by its operational simplicity and generality, including chemical diversification of advanced intermediates.
C-C bond forming cross-couplings are convenient technologies for the construction of functional molecules. Consequently, there is continual interest in approaches that can render traditionally inert ...functionality as cross-coupling partners, included in this are ketones which are widely-available commodity chemicals and easy to install synthetic handles. Herein, we describe a dual catalytic strategy that utilizes dihydroquinazolinones derived from ketone congeners as adaptative one-electron handles for forging C(sp
) architectures via α C-C cleavage with aryl and alkyl bromides. Our approach is achieved by combining the flexibility and modularity of nickel catalysis with the propensity of photoredox events for generating open-shell reaction intermediates. This method is distinguished by its wide scope and broad application profile--including chemical diversification of advanced intermediates--, providing a catalytic technique complementary to existing C(sp
) cross-coupling reactions that operates within the C-C bond-functionalization arena.
Atomically thin 2D crystals have gained tremendous attention owing to their potential impact on future electronics technologies, as well as the exotic phenomena emerging in these materials. ...Monolayers of α‐phase Sb (α‐antimonene), which shares the same puckered structure as black phosphorous, are predicted to be stable with precious properties. However, the experimental realization still remains challenging. Here, high‐quality monolayerα‐antimonene is successfully grown, with the thickness finely controlled. The α‐antimonene exhibits great stability upon exposure to air. Combining scanning tunneling microscopy, density functional theory calculations, and transport measurements, it is found that the electron band crossing the Fermi level exhibits a linear dispersion with a fairly small effective mass, and thus a good electrical conductivity. All of these properties make the α‐antimonene promising for future electronic applications.
Monolayer α‐phase antimonene, a structural analog to black phosphorous, is fabricated on a WTe2 substrate. The α‐antimonene exhibits great stability upon exposure to air. Its electron band crossing the Fermi level exhibits a linear dispersion with a fairly small effective mass, and thus a good electrical conductivity. All of these properties make α‐antimonene promising in future electronic applications.
Superconducting quantum interferometer device (SQUID) plays a key role in understanding electromagnetic properties and emergent phenomena in quantum materials. The technological appeal of SQUID is ...that its detection accuracy for the electromagnetic signal can precisely reach the quantum level of a single magnetic flux. However, conventional SQUID techniques normally can only be applied to a bulky sample and do not have the capability to probe the magnetic properties of micro‐scale samples with small magnetic signals. Herein, it is demonstrated that, based on a specially designed superconducting nano‐hole array, the contactless detection of magnetic properties and quantized vortices in micro‐sized superconducting nanoflakes is realized. An anomalous hysteresis loop and a suppression of Little–Parks oscillation are observed in the detected magnetoresistance signal, which originates from the disordered distribution of the pinned vortices in Bi2Sr2CaCu2O8+δ. Therefore, the density of pinning centers of the quantized vortices on such micro‐sized superconducting samples can be quantitatively evaluated, which is technically inaccessible for conventional SQUID detection. The superconducting micro‐magnetometer provides a new approach to exploring mesoscopic electromagnetic phenomena of quantum materials.
Superconducting quantum interferometer devices are important in investigating magnetic properties in quantum materials, but cannot probe micro‐scale samples with small magnetic signals. Based on the superconducting micro‐magnetometer, the density of vortex pinning centers in Bi2Sr2CaCu2O8 nanoflake can be determined as 1.1 × 1012 m−2. This superconducting micro‐magnetometer sheds light on the detection of small magnetic signals of nanoflakes.
RATIONALE:Microvascular inflammation and endothelial dysfunction secondary to unchecked activation of endothelium play a critical role in the pathophysiology of sepsis and organ failure. The ...intrinsic signaling mechanisms responsible for dampening excessive activation of endothelial cells are not completely understood.
OBJECTIVE:To determine the central role of YAP (Yes-associated protein), the major transcriptional coactivator of the Hippo pathway, in modulating the strength and magnitude of endothelial activation and vascular inflammation.
METHODS AND RESULTS:Endothelial-specific YAP knockout mice showed increased basal expression of E-selectin and ICAM (intercellular adhesion molecule)-1 in endothelial cells, a greater number of adherent neutrophils in postcapillary venules and increased neutrophil counts in bronchoalveolar lavage fluid. Lipopolysaccharide challenge of these mice augmented NF-κB (nuclear factor-κB) activation, expression of endothelial adhesion proteins, neutrophil and monocyte adhesion to cremaster muscle venules, transendothelial neutrophil migration, and lung inflammatory injury. Deletion of YAP in endothelial cells also markedly augmented the inflammatory response and cardiovascular dysfunction in a polymicrobial sepsis model induced by cecal ligation and puncture. YAP functioned by interacting with the E3 ubiquitin-protein ligase TLR (Toll-like receptor) signaling adaptor TRAF6 (tumor necrosis factor receptor-associated factor 6) to ubiquitinate TRAF6, and thus promoted TRAF6 degradation and modification resulting in inhibition of NF-κB activation. TRAF6 depletion in endothelial cells rescued the augmented inflammatory phenotype in mice with endothelial cell–specific deletion of YAP.
CONCLUSIONS:YAP modulates the activation of endothelial cells and suppresses vascular inflammation through preventing TRAF6-mediated NF-κB activation and is hence essential for limiting the severity of sepsis-induced inflammation and organ failure.
The design, catalytic process, and property study of nanozymes are of importance for both fundamental research and application demand. Here, the peroxidase‐mimicking properties of a series of carbon ...dots (C‐dots) was systematically investigated and they were found to be probably closer to their natural counterparts, as compared to the known corresponding nanozymes. Firstly, four kinds of metal‐free and surface‐modulated C‐dots were bottom‐up fabricated using glucose, α‐cyclodextrin (CD), β‐CD, and γ‐CD as precursors, respectively, and their formation processes, structures, as well as surface chemistry were investigated. Secondly, in the peroxidase‐mimicking catalytic system, no hydroxyl radicals were produced, which indicates a different and special catalytic mode. By employing a joint experimental–theoretical study, a probable catalytic mechanism is proposed. Thirdly, the present C‐dots maintained well their catalytic activity even in complicated serum matrices because their catalytic performances are completely irrelevant of any cation‐related binding sites. Finally, the catalytic performances of the as‐prepared C‐dots were modulated by either pre‐engineering NP surface structures or subsequently introducing photo‐regulated host–guest reactions.
A specific nanozyme: As assessed by the combination of experimental and theoretical studies, the proposed carbon dots show a different and special peroxidase‐mimicking activity. Owing to the stronger anti‐interference capacity and versatilely modulated catalytic properties, they are closer to their natural counterparts as compared to the known corresponding nanozymes.
Selective hydrogenation of C=O against the conjugated C=C in cinnamaldehyde (CAL) is indispensable to produce cinnamyl alcohol (COL). Nonetheless, it is challenged by the low selectivity and the need ...to use organic solvents. Herein, for the first time, we report the use of Fe‐Co alloy nanoparticles (NPs) on N‐doped carbon support as a selective hydrogenation catalyst to efficiently convert CAL to COL. The resultant catalyst with the optimized Fe/Co ratio of 0.5 can achieve an exceptional COL selectivity of 91.7 % at a CAL conversion of 95.1 % in pure water medium under mild reaction conditions, ranking it the best performed catalyst reported to date. The experimental results confirm that the COL selectivity and CAL conversion efficiency are, respectively promoted by the presence of Fe and Co, while the synergism of the alloyed Fe‐Co is the key to concurrently achieve high COL selectivity and CAL conversion efficiency.
A bimetallic Fe‐Co alloying strategy is innovatively utilized to concurrently enhance the selectivity and conversion efficiency for selective hydrogenation of cinnamaldehyde to cinnamyl alcohol in water. A Fe‐Co alloy catalyst with a Fe/Co molar ratio of 0.5 achieves an exceptional selectivity of 91.7 % at 95.1 % conversion.
Thermal energy storage technologies based on phase‐change materials (PCMs) have received tremendous attention in recent years. These materials are capable of reversibly storing large amounts of ...thermal energy during the isothermal phase transition and offer enormous potential in the development of state‐of‐the‐art renewable energy infrastructure. Thermal conductivity plays a vital role in regulating the thermal charging and discharging rate of PCMs and improving the heat‐utilization efficiency. The strategies for tuning the thermal conductivity of PCMs and their potential energy applications, such as thermal energy harvesting and storage, thermal management of batteries, thermal diodes, and other forms of energy utilization, are summarized systematically. Furthermore, a research perspective is given to highlight emerging research directions of engineering advanced functional PCMs for energy applications.
A comprehensive review regarding the tuning of the thermal conductivity of phase change composites for thermal energy conversion, storage, and utilization is provided, which gives an insightful understanding of the thermal energy storage and conversion processes. The aim is to stimulate potential emerging applications of phase change materials.
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