Single-crystalline van der Waals layered dielectric with high dielectric constant.

The scaling of silicon-based transistors at sub-ten-nanometre technology nodes faces challenges such as interface imperfection and gate current leakage for an ultrathin silicon channel1,2. For next-generation nanoelectronics, high-mobility two-dimensional (2D) layered semiconductors with an atomic thickness and dangling-bond-free surfaces are expected as channel materials to achieve smaller channel sizes, less interfacial scattering and more efficient gate-field penetration1,2. However, further progress towards 2D electronics is hindered by factors such as the lack of a high dielectric constant (κ) dielectric with an atomically flat and dangling-bond-free surface3,4. Here, we report a facile synthesis of a single-crystalline high-κ (κ of roughly 16.5) van der Waals layered dielectric Bi2SeO5. The centimetre-scale single crystal of Bi2SeO5 can be efficiently exfoliated to an atomically flat nanosheet as large as 250 × 200 µm2 and as thin as monolayer. With these Bi2SeO5 nanosheets as dielectric and encapsulation layers, 2D materials such as Bi2O2Se, MoS2 and graphene show improved electronic performances. For example, in 2D Bi2O2Se, the quantum Hall effect is observed and the carrier mobility reaches 470,000 cm2 V-1 s-1 at 1.8 K. Our finding expands the realm of dielectric and opens up a new possibility for lowering the gate voltage and power consumption in 2D electronics and integrated circuits.

Orbital Magneto-Nonlinear Anomalous Hall Effect in Kagome Magnet Fe_{3}Sn_{2}.

It has been theoretically predicted that perturbation of the Berry curvature by electromagnetic fields gives rise to intrinsic nonlinear anomalous Hall effects that are independent of scattering. Two types of nonlinear anomalous Hall effects are expected. The electric nonlinear Hall effect has recently begun to receive attention, while very few studies are concerned with the magneto-nonlinear Hall effect. Here, we combine experiment and first-principles calculations to show that the kagome ferromagnet Fe_{3}Sn_{2} displays such a magneto-nonlinear Hall effect. By systematic field angular and temperature-dependent transport measurements, we unambiguously identify a large anomalous Hall current that is linear in both applied in-plane electric and magnetic fields, utilizing a unique in-plane configuration. We clarify its dominant orbital origin and connect it to the magneto-nonlinear Hall effect. The effect is governed by the intrinsic quantum geometric properties of Bloch electrons. Our results demonstrate the significance of the quantum geometry of electron wave functions from the orbital degree of freedom and open up a new direction in Hall transport effects.

Base-Catalyzed One-Pot Synthesis of 2,3,6-Substituted Pyridines.

A three-component reaction catalyzed by base was established, which mainly consisted of ynals, isocyanates, amines and alcohols. This strategy provides a wide range of substrates and represents a simple process for the preparation of different pyridine derivatives in good yields with high regioselectivities.

CPA-catalyzed asymmetric domino thia-Michael/aldol reactions for simultaneous chiral center and axial chirality formation.

A highly enantio- and diastereoselective domino thia-Michael/aldol reaction applying 5H-dibenzo[a,c][7]annulen-5-one as a Michael acceptor, catalyzed by a chiral phosphoric acid (CPA), has been developed. The bridged biaryl adduct contains multiple stereogenic centers in the bridging linkage as well as a thermodynamically controlled stereogenic axis. The energy difference between the two atropodiastereomers is about 9.1 kcal mol-1, which accounts for the observed excellent diastereoselectivity (>20 : 1).

Identification and Analysis of Immune Microenvironment-Related Genes for Keloid Risk Prediction and Their Effects on Keloid Proliferation and Migration.

Keloid is a kind of proliferative scar with continuous growth, no restriction and easy recurrence, which cannot be cured and bring serious physical injury and psychological burden to patients. The main reason is that the pathological mechanism is not clear. Therefore, this project is expected to reveal the immune microenvironment-related genes and their functions in keloid progression, and provide effective targets for the treatment of keloid. Firstly, 8 kinds of immune infiltrating cells and 19 potential characteristic genes were identified by immune infiltration analysis, ssGSEA, LASSO regression (glmnet algorithm and lars algorithm) and WGCNA, indicating that keloid was closely related to the changes of immune microenvironment. Then, 4 pathological biomarkers of keloid (MAPK1, PTPRC, STAT3 and IL1R1) were identified by differentially analysis, univariate analysis, LASSO regression (lars algorithm), support vector machine recursive feature elimination (SVM-REF) algorithm, multivariate logical regression analysis and six machine learning algorithms. Based on the 4 feature genes, the risk prediction model and nomogram were constructed. Calibration curve and ROC analysis (AUC = 0.930) showed that the model had reliable clinical value. Subsequently, consistent cluster analysis was used to find that there were 2 immune microenvironment subsets in keloid patients, of which subgroup II was immune subgroup. Multiple independent datasets and RT-qPCR showed that the expression trend of the 4 genes was consistent with the analysis. Cell gain-loss experiment confirmed that 4 genes regulated the proliferation and migration of keloid cells. The above data shows that MAPK1, PTPRC, STAT3 and IL1R1 may be personalized therapeutic targets for keloid patients.

Antisymmetric Seebeck Effect in a Tilted Weyl Semimetal.

Tilting the Weyl cone breaks the Lorentz invariance and enriches the Weyl physics. Here, we report the observation of a magnetic-field-antisymmetric Seebeck effect in a tilted Weyl semimetal, Co_{3}Sn_{2}S_{2}. Moreover, it is found that the Seebeck effect and the Nernst effect are antisymmetric in both the in-plane magnetic field and the magnetization. We attribute these exotic effects to the one-dimensional chiral anomaly and phase space correction due to the Berry curvature. The observation is further reproduced by a theoretical calculation, taking into account the orbital magnetization.

Photocatalytic C-H Disulfuration for the Preparation of Indolizine-3-disulfides.

A photocatalytic C-H disulfuration of indolizines was developed, giving an approach to a wide variety of indolizine-3-disulfides with good yields. Trisulfide dioxides were explored as a high-efficient disulfuration reagent. This disulfuration reaction could be scaled up to grams. Mechanistic studies support a photoinduced pathway involving the generation of indolizine cationic radicals. A bulky alkyl substituent on terminal sulfur of trisulfide dioxide A was necessary for selective formation of disulfide over monosulfide.

Chirality-Dependent Hall Effect and Antisymmetric Magnetoresistance in a Magnetic Weyl Semimetal.

Weyl semimetals host a variety of exotic effects that have no counterpart in conventional materials, such as the chiral anomaly and magnetic monopole in momentum space. These effects give rise to unusual transport properties, including a negative magnetoresistance and a planar Hall effect, etc. Here, we report a new type of Hall and magnetoresistance effect in a magnetic Weyl semimetal. Unlike antisymmetric (with respect to either magnetic field or magnetization) Hall and symmetric magnetoresistance in conventional materials, the discovered magnetoresistance and Hall effect are antisymmetric in both magnetic field and magnetization. We show that the Berry curvature, the tilt of the Weyl node, and the chiral anomaly synergically produce these phenomena. Our results reveal a unique property of Weyl semimetals with broken time reversal symmetry.

Recent advances in the synthesis of indolizine and its derivatives by radical cyclization/cross-coupling.

Indolizine is a nitrogen-containing heterocycle that has a variety of potential biological activities, and some indolizine derivatives with excellent fluorescence properties can even be used as organic fluorescent molecules for biological and material applications. Thus, many approaches for their synthesis have been developed. Among them, radical-induced synthetic approaches are receiving increasing attention owing to their unique advantages, such as efficient heterocycle construction, efficient C-C or C-X bond construction, and high atom- and step-economy. This review systematically examines the current and latest synthetic strategies using radical species or radical intermediates for synthesizing indolizines and their derivatives. This review is classified into two parts based on the type of building blocks used for indolizine ring construction and the type of radical trigger for indolizine derivative construction. We anticipate that this review will provide a deep understanding of this topic, and ultimately help researchers to develop novel approaches for the synthesis of indolizine and its derivatives.

Pronounced Dependence of All-Polymer Solar Cells Photovoltaic Performance on the Alkyl Substituent Patterns in Large Bandgap Polymer Donors.

For all-polymer solar cells which are composed of polymer donors and polymer acceptors, the effect of alkyl side chains on photovoltaic performance is a matter of some debate, and this effect remains difficult to forecast. In this concise contribution, we demonstrate that three alkyls namely branched alkyl 2-butyloctyl (2BO), long linear alkyl n-dodecyl (C12), and double-short linear alkyl n-hexyls (DC6) incorporated into the side chains of large bandgap polymer donor PBDT-TTz can induce considerable, of significance, and different electronic, optical, and morphological parameters. Systematic studies shed light on the critical role of the double-short linear alkyl n-hexyls (DC6) in (i) producing large ionization potential value, (ii) increasing propensity of the polymer to order along the π-stacking direction, (iii) generating polymer crystallites with more preferential "face-on" orientation, consequently, (iv) improvement of carriers transportation, (v) suppression of charge recombination, (vi) reduction of energy loss in all-polymer devices. In parallel, we unearth that the PBDT-TTz with double-short linear alkyl n-hexyls (DC6) represents the highest efficiency of 8.3 %, whereas, the other two PBDT-TTz analogues (2BO, C12) yield efficiencies of less than 3 % in optimized all-polymer solar cells. Though branched or long linear alkyl side chains (2BO, C12) have been applied to provide the solution processability of conjugated polymers, motifs bearing multiple short linear alkyl substituents (DC6) are proved critical to the development of high performing polymers.

Palladium-catalyzed C(sp²)-H arylation using formamide as a transformable directing group.

A new process for the ortho arylation of formanilides through palladium-catalyzed C-H activation is described. Formamide is reported as a transformable directing group in the transition-metal-catalyzed C-H functionalization reaction. The resulting biarylformanilide products can be readily transformed to the corresponding biarylisocyanides or N-heterocycles.

(+)-Catechin Alleviates CCI-Induced Neuropathic Pain in Rats by Modulating the IL34/CSFIR Axis and Attenuating the Schwann Cell-Macrophage Cascade Response in the DRG.

The aim of this study was to investigate the potential therapeutic applications of (+)-catechin in the treatment of neuropathic pain. In vivo study, 32 SD rats were randomly divided into four groups: sham group, chronic constriction injury (CCI) group, CCI + ibuprofen group and CCI+ (+)-catechin group. They were subjected to behavioural tests, ELISA, immunohistochemistry and Western blotting. The mechanisms involved were investigated using specific inhibitors in cell experiments. Results of in vivo experiments showed that (+)-catechin could reduce the cold sensitivity pain in a rat model of CCI; ELISA and immunohistochemistry results showed that (+)-catechin could decrease the levels of IL-8, IL-6, TNF-α, CCL2 and CCL5 in serum and the expression levels of nNOS, COX2, IL6, TNF-α, IBA-1 and CSF1R in DRG of CCI rats. Finally, western blot confirmed that (+)-catechin could diminish the levels of IL-34/CSF1R/JAK2/STAT3 signalling pathway in DRG of CCI rats. In vitro studies showed that (+)-catechin reduced IL-34 secretion in LPS-induced RSC96 cells. Meanwhile, (+)-catechin administration in LPS-induced Schwann cell-conditioned medium (L-CM) significantly inhibited the proliferation and migration of RAW264.7 cells; in addition, L-CM+(+)-catechin reduced the activation of the CSF1R/JAK2/STAT3 signalling pathway. (+)-Catechin attenuated the Schwann cell-macrophage cascade response in the DRG by modulating the IL34/CSFIR axis and inhibiting activation of the JAK2/STAT3 pathway, thereby attenuating CCI-induced neuropathic pain in rats.

ß-Sitosterol Alleviates Neuropathic Pain by Affect Microglia Polarization through Inhibiting TLR4/NF-κB Signaling Pathway.

The etiology of neuropathic pain is mostly caused by mechanical deformation and neuroinflammation, of which neuroinflammation is the main cause of chronic neuropathic pain. Activation of the TLR4/NF-κB signaling pathway mediates elevated levels of inflammatory cytokines, and we clearly demonstrated by in vivo and in vitro Western blot experiments that ß-sitosterol significantly inhibited the elevated Toll-like receptor 4 (TLR4) expression levels and nuclear factor-kappa B (NF-κB) activation associated with inflammatory responses. In cellular experiments, we clearly saw that both ß-sitosterol and TLR4/NF-κB signaling pathway inhibitors could inhibit M1 proinflammatory phenotype expression and promote M2 anti-inflammatory phenotype expression in GMI-R1 microglia by flow cytometry and immunofluorescence assays. Therefore, we suggest that ß-sitosterol can affect microglial polarization by inhibiting the TLR4/NF-κB signaling pathway thereby reducing neuroinflammation and thus alleviating neuropathic pain.

Synthesis of 7-Arylthiomethyl Dibenzo[b,d]azepines through Imidoylative Heck Cyclization and CPA-Catalyzed Thio-Michael Addition/Enantioselective Protonation.

A chiral phosphoric acid-catalyzed thio-Michael addition/enantioselective protonation has been developed for the first time. The reaction applies 7-methylene-6-aryl-7H-dibenzo[b,d]azepines, products of Pd-catalyzed imidoylative Heck cyclization, as Michael acceptors in reactions with a wide range of aryl thiols. Diversified 7-[(arylthio)methyl]-7H-dibenzo[b,d]azepines bearing a benzylic stereocenter and a thermodynamically regulated biaryl axis were produced with good to excellent enantioselectivity and 14-25:1 diastereoisomeric ratios.

Synthesis of 2-alkoxy(aroxy)-3-substituted quinolines by DABCO-promoted cyclization of o-alkynylaryl isocyanides.

Diversified 2-alkoxy- and 2-aroxy-3-substituted quinolines were synthesized from o-alkynylaryl isocyanides and alcohols and phenols promoted by DABCO, respectively. The reaction was initiated by nucleophilic addition of DABCO to isocyanide and subsequent cycliztion, leading to a DABCO-quinoline-based adduct as the reactive intermediate, followed by substitution of the DABCO moiety with oxygenated nucleophiles.

Synergistic Effects of Polymer Donor Backbone Fluorination and Nitrogenation Translate into Efficient Non-Fullerene Bulk-Heterojunction Polymer Solar Cells.

State-of-the-art non-fullerene bulk-heterojunction (BHJ) polymer solar cells outperform the more extensively studied polymer-fullerene BHJ solar cells in terms of efficiency, thermal-, and photostability. Considering the strong light absorption in the near-infrared region (600-1000 nm) for most of the efficient acceptors, the exploration of high-performing large band gap (LBG) polymer donors with complementary optical absorption ranging from 400 to 700 nm remains critical. In this work, the strategy of concurrently incorporating fluorine (-F) and unsaturated nitrogen (-N) substituents along the polymer backbones is used to develop the LBG polymer donor PB[N][F]. Results show that the F- and N-substituted polymer donor PB[N][F] realizes up to 14.4% efficiency in BHJ photovoltaic devices when paired with a benchmark molecule acceptor Y6, which largely outperforms the analogues PB with an efficiency of only 3.6% and PB[N] with an efficiency of 11.8%. Systematic examinations show that synergistic effects of polymer backbone fluorination and nitrogenation can significantly increase ionization potential values, improve charge transport, and reduce bimolecular recombination and trap-assisted recombination in the PB[N][F]:Y6 BHJ system. Importantly, our study shows that the F- and N-substituted conjugated polymers are promising electron-donor materials for solution-processed non-fullerene BHJ solar cells.

Impact of Donor-Acceptor Interaction and Solvent Additive on the Vertical Composition Distribution of Bulk Heterojunction Polymer Solar Cells.

The vertical composition distribution of a bulk heterojunction (BHJ) photoactive layer is known to have dramatic effects on photovoltaic performance in polymer solar cells. However, the vertical composition distribution evolution rules of BHJ films are still elusive. In this contribution, three BHJ film systems, composed of polymer donor PBDB-T, and three different classes of acceptor (fullerene acceptor PCBM, small-molecule acceptor ITIC, and polymer acceptor N2200) are systematically investigated using neutron reflectometry to examine how donor-acceptor interaction and solvent additive impact the vertical composition distribution. Our results show that those three BHJ films possess homogeneous vertical composition distributions across the bulk of the film, while very different composition accumulations near the top and bottom surface were observed, which could be attributed to different repulsion, miscibility, and phase separation between the donor and acceptor components as approved by the measurement of the donor-acceptor Flory-Huggins interaction parameter χ. Moreover, the solvent additive 1,8-diiodooctane (DIO) can induce more distinct vertical composition distribution especially in nonfullerene acceptor-based BHJ films. Thus, higher power conversion efficiencies were achieved in inverted solar cells because of facilitated charge transport in the active layer, improved carrier collection at electrodes, and suppressed charge recombination in BHJ solar cells.

Skeletal rearrangement of cyano-substituted iminoisobenzofurans into alkyl 2-cyanobenzoates catalyzed by B(C6F5)3.

An efficient method for the direct conversion of cyano-substituted iminoisobenzofurans into their corresponding alkyl 2-cyanobenzoates has been developed. This transformation proceeds via cleavage of C-C, C-O, and C-N bonds in starting iminoisobenzofurans. DFT study revealed that intermediate α-iminonitriles are produced in situ via C-C bond formation between 2-iminium benzoates and a cyanide ion. Generation of isocyanide as the byproduct in a more thermodynamic manner in DFT calculations also supports the experimental results.

Arylative cyclization of 2-isocyanobiphenyls with anilines: one-pot synthesis of 6-arylphenanthridines via competitive reaction pathways.

A transition-metal-free method for the synthesis of C6 phenanthridine derivatives by arylative cyclization of 2-isocyanobiphenyls with arylamines in one pot was developed. Mechanistic studies suggest that electrophilic aromatic substitution (SEAr) of a nitrilium intermediate and homolytic aromatic substitution (HAS) of an imidoyl radical intermediate are two competitive reaction pathways involved in the annulation step.