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Two-dimensional (2D) of transition metal dichalcogenides (TMDCs) are potential candidates for thermoelectric (TE) applications due to their unique structural properties. In this paper, we constructed an 2D monolayer TMDCs semiconductor γ-PbSn2(X=S, Se, Te) and first-principles calculations and Boltzmann transport theory are used to study the thermoelectric performance. We found that γ-PbSnX2 had an ultra-high carrier mobility up to 4.04×103 cm2V−1s−1 leading to a metal-like electrical conductivity. Meanwhile, γ-PbSnX2 both have high Seebeck coefficients, resulting in high power-factors, and also shows intrinsic low lattice thermal conductivity of 6-8 W/mK at room temperature. The lower lattice thermal conductivity and high power-factors resulted in excellent thermoelectric performance. The high ZT values of γ-PbSnS2 and γ-PbSnSe2 were as high as 2.65 and 2.96 at 900 K, respectively. The result suggests that the monolayer γ-PbSnX2 are better candidates for excellent thermoelectric performance.

Germplasm resource is the source of herbal medicine production. Cultivation of superior germplasm resources helps to resolve the serious conflict between long-term population persistence and growing market demand by producing materials with high quality consistently.Cibotium barometzis the original plant of cibotii rhizoma (“Gouji”), a traditional Chinese medicine used in the therapy of pain, weakness, and numbness of lower extremity. Long-history use ofCibotiumhas rendered wild populations of this species declined seriously in China. Without sufficient understanding of species and lineage diversity ofCibotium, it is difficult to propose a targeted conservation scheme at present, let alone selecting high-quality germplasm resources. In order to fill such a knowledge gap, this study sampledC. barometzand relative species throughout their distribution in China, performed genome skimming to obtain plastome data, and conducted phylogenomic analyses. We constructed a well-supported plastome phylogeny of ChineseCibotium, which showed that three species with significant genetic difference distributed in China, namelyC. barometz,C. cumingii, andC. sino-burmaense, a cryptic species endemic to NW Yunnan and adjacent region of NE Myanmar. Moreover, our results revealed two differentiated lineages ofC. barometzdistributed in the east and west side of a classic phylogeographic boundary that probably shaped by monsoons and landforms in China. We also evaluated the resolution of nine traditional barcode loci, and designed five new DNA barcodes based on the plastome data which can discriminate all these species and lineages of ChineseCibotiumaccurately. These novel findings integrated genetic basis will guide conservation planners and medicinal plant breeders to build systematic conservation plans and exploit germplasm resources ofCibotiumin China.

The Curie temperature increases from an intrinsic value of 266 K to 353 K when the biaxial tensile strain of 2.3% is applied to the monolayer MnSe2 magnetic substrate, but the valley splitting of MoTe2 remains as large as 72 meV.

Although the incidence and death rates of gastric cancer (GC) are decreasing, approximately one million new cases and 800,000 GC-related deaths were reported worldwide in 2018. Currently, the oncogenesis of GC remains unclear, and the demand for novel treatment options are unmet. Here, we explored the role of aldo-keto reductase family 1 member B (AKR1B1) in the progression of GC. The proliferation, migration, and invasion of GC cells were evaluated by CCK-8 assay, wound healing assay, and transwell assay, respectively. The interaction between EBF transcription factor 1 (EBF1) and the promoter region of AKR1B1 was determined by luciferase reporter assay and chromatin immunoprecipitation (ChIP). Gene expression levels were measured by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting assay. The expression of AKR1B1 was elevated in GC cells, resulting in increased cell proliferation, migration, and invasion. Meanwhile, EBF1 was a negative regulator of AKR1B1; its overexpression suppressed AKR1B1 expression and GC progression. Furthermore, knockdown of ZNF521 induced EBF1 expression, thus suppressing AKR1B1 expression and resulting in attenuated GC growth and invasiveness. Notably, knockdown of ZNF521 attenuated GC progression and was rescued by overexpression of AKR1B1. Our current study revealed a novel ZNF521/EBF1/AKR1B1 axis in GC and elaborated its important role in promoting GC progression, providing potential therapeutic targets for anti-GC treatments.

Achieving high tunneling magnetoresistance (TMR) in molecular-scale junctions is attractive for their applications in spintronics. By using density-functional theory (DFT) in combination with the nonequilibrium Green's function (NEGF) method, we investigated the spin-resolved charge transport properties of molecular junctions based on Co-Salophene symmetric/asymmetric dimers. We found that nearly 100% spin-injection efficiency (SIE) can be achieved in parallel spin configuration with the spin dependent quantum interference effect. In particular, the high TMR is demonstrated to be closely related to the molecular symmetry, reaching 4600% and 2200% for a symmetric and asymmetric molecular junction (MJ), respectively. Further inelastic transport analyses reveal that the excellent TMR properties of the symmetric MJ can still be preserved in the electron-vibration interaction and temperature effects being considered, which provides an insight for designing future molecular integrated circuit devices.

Two-dimensional materials with intrinsic long-range ordered magnetic moments have drawn a lot of attention. However, for practical applications, whether or not the magnetism is stable in their nanostructures has not been revealed. Here, based on the recently proposed magnetic penta-hexa-graphene, we study the electronic and magnetic properties of its nanoribbons (named PHGNRs). The results show that the PHGNRs have intrinsic robust magnetic moments that are different from zigzag graphene nanoribbons, where the magnetic moments caused by the edge effect are vulnerable. Moreover, the magnetic ground states, namely, ferromagnetic (FM) or antiferromagnetic (AFM), can be transformed by changing the width of PHGNRs. Most interestingly, under the FM ground state, the spin-polarized electronic properties reveal that the zigzag PHGNRs transform from spin-gapless semiconductors (SGSs) to half-metals, as the width of nanoribbons increases, while all the armchair PHGNRs are magnetic semiconductors. Furthermore, by considering different edge effects caused by the residual carbon atoms on the edges, the PHGNRs can further derive different types of SGSs, as well as half-metals. Our work suggests that the PHGNRs possessing intrinsic robust magnetic moments have potential applications in the field of spintronic devices.

Finding sustainable and renewable energy to replace traditional fossil fuel is critical for reducing greenhouse gas emission and avoiding environment pollution. Solar cells that convert energy of sunlight into electricity offer a viable route for solving this issue. At present, halide perovskites are the most potential candidate materials for solar cell with considerable power conversion efficiency, whereas their stability remains a challenge. In this work, we summarize four different key factors that influence the stability of halide perovskites: (a) effect of environmental moisture on the degradation of halide perovskites. The performance of halide perovskite solar cells is reduced due to hydrated crystal hinders the diffusion of photo‐generated carriers, which can be solved by materials encapsulation technique; (b) photo‐induced instability. Through uncovering the underlying physical mechanism, we note that materials engineering or novel device structure can extend the working life of halide perovskites under continuous light exposure; (c) thermal stability. Halide perovskites are rapidly degraded into PbI2 and volatile substances as heating due to lower formation energy, whereas hybrid perovskite is little changed; (d) electric field effect in the degradation of halide perovskites. The electric field impacts significantly on the carrier separation, changes direction of photo‐induced currents and generates switchable photovoltaic effect. For each key factor, we have shown in detail the underlying physical mechanisms and discussed the strategies to overcome this stability difficulty. We expect this review from both theoretical and experimental points of view can be beneficial for development of perovskite solar cell materials and promotes practical applications.

Stacking order and strain are the key component in tuning magnetic property of two-dimensional (2D) van der Waals magnetic materials. In this work, we investigated the crystal structure stability of a 2D ferromagnetic Janus chromium dichalcogenide CrSTe bilayer in AB- and AC-stacking orders and found that AB-stacking CrSTe bilayers, which have a smaller layer spacing and a Curie temperature near room temperature, are more stable than AC-stacking one. The magnetic ground states, exchange coupling constant, and Curie temperature of the AB-stacking CrSTe bilayer can be tuned by strain. It is found that the magnetic ground states of the AB- and AC-stacking CrSTe bilayers are ferromagnetic and interlayer antiferromagnetic within a certain strain range, respectively, indicating that the CrSTe bilayers are expected to be used in the double spin filter. Our results demonstrated that the 2D Janus CrSTe bilayer has the potential in the application of spintronic devices with stable performance and low-power consumption at room temperature.

BACKGROUND: To explore the contribution of type 2 diabetes mellitus (T2DM) to hypothalamic inflammation and depressive disorders in young patients with obesity. METHODS: According to the diagnostic criteria for T2DM, all of patients with obesity were divided into the diabetic and the non-diabetic groups. The severity of depressive disorders was assessed by self-rating depression scale (SDS). The signal intensity (SI) ratio of the T2-weighted phase of the superior hypothalamus/amygdala (H/A) was measured using a quantitative magnetic resonance imaging (MRI) technique to evaluate hypothalamic inflammation. Univariate and multivariate logistic regression analysis was used to find the influencing factors of depressive disorder. The prediction equation’s sensitivity and specificity for the depressive disorder were calculated based on the receiver operating characteristic (ROC) curve. RESULTS: In young patients with obesity and diabetes, the incidence of depression is 79.49%, which was much higher than that in patients without diabetes (P

Phonon hydrodynamics, a collective motion of phonons, has recently attracted renewed attention since its temperature window has been greatly extended in layered materials. The exploration of phonon hydrodynamics bears importance in understanding phonon collective behavior, and its window is crucial for determining the phonon transport regime and engineering the heat transport. Thus, strategies for continuous tuning of the hydrodynamic window are needed, but it remains a challenge. In this work, we demonstrate that the phonon hydrodynamic window in bilayer graphene can be strongly altered by the strain based on theoretical calculations. In particular, the phonon hydrodynamics can be observed at 60 K in unstrained bilayer graphene, while only 0.25% strain can reduce this temperature to 28 K. This strong strain dependence not only provides an efficient way of modulating the phonon collective behavior but also renders a possibility of strain-induced transition of phonon transport regime.

Suppressing phonon thermal conductance is one of the most important ways to improve the thermoelectric efficiency. In the present work, we theoretically analyze the phonon transport properties in the intermediately coupled molecular junction. We show that the twist angle can serve as an independent degree of freedom to manipulate phonon interference and then more precisely regulate the thermal conductance of molecular junctions. Moreover, the phonon mode-resolved calculation indicates that the conduction of in-plane phonon modes is strongly blocked, and only the out-of-plane phonon modes can be transported through the molecular junction. This makes it possible to further suppress the phonon thermal conductance with the twist angle and then significantly improve the thermoelectric figure-of-merit of intermediately coupled molecular junctions. This result suggests a more convenient way to manipulate heat transport, which has potential applications in phononic and thermoelectric molecular devices.

Two-dimensional (2D) porous coordination polymers (PCPs) are a kind of porous crystalline material formed from metal nodes and organic ligands through coordination bonds. PCPs exhibit unique features such as flexible structures, abundant accessible active sites, and high surface areas. The greatest challenge in the commercialization of 2D PCPs and their nano-composites is achieving a controllable and facile synthesis of 2D PCPs with low cost and high quality. Recently, significant progress has been made in the structural and morphological regulation of 2D PCPs. It is still of considerable significance to further explore the synthetic mechanism and unique properties of 2D PCPs and their nano-composites. In this review, recent research progress in the synthesis of 2D PCP materials and their applications is summarized. Firstly, the development process of 2D PCPs is briefly introduced, and then the synthesis strategy of 2D PCPs and their nano-composites is discussed. Subsequently, the potential applications of 2D PCPs and their nano-composites in electro-catalysis and electronic transport are introduced. Finally, the challenges and prospects for the synthesis and applications of 2D PCPs and their nano-composites are addressed for future developments.

The introduction of spin degree of freedom has not only made the electronic transport properties colorful, but also highly attracted people's attention to the spin-related quantum heat transport, with the rapid progress of spin caloritronics in recent year. Against this background, the modeling and tuning of quantum heat transport in magnetic nanostructures has become an emerging and attractive topic. In particular, the spin-phonon interaction has played a crucial role in the novel transport behaviors of heat and spin. In this perspective article, we give an insight into the current theoretical and experimental progresses and discuss the further research perspectives of spin-phonon interaction-related heat transfer.

Pure spin current is expected to be utilized for designing energy-saving devices. Using first-principles calculations in combination with a non-equilibrium Green's function method, the spin-dependent thermoelectric transport properties of metallocene dimer-based molecular junctions are investigated. The results show that spin-polarized currents can be achieved when a temperature difference is applied in molecular structures. It is found that the spin-polarized transport properties are different when transition metals in the dimers are different. It is interesting that a negative differential thermoelectric resistance and a perfect spin filtering effect can be found in chromocene dimer-based and manganocene dimer-based molecular junctions. Moreover, one key finding is that a pure spin current can be obtained in a cobaltocene dimer-based molecular junction, in which the spin-dependent Seebeck coefficient is larger than the charge Seebeck coefficient. These interesting results indicate that metallocene dimer-based molecular junctions have potential applications in future thermal spintronic and spin thermoelectric devices.

We investigated the diffusion properties of metal atoms in van der Waals layered materials using first-principles calculations combined with group theory analysis. We found that there is an abnormal diffusion behavior of Cu in MoS2, which originated from the competition of the electronic and strain energies. Although the atom diffusing in bulk MoS2 constantly changes the symmetry of the system with reduced electronic energy due to p–d coupling between occupied Cu d and unoccupied anion p states, the strain energy is dominant. As a result, the energy barrier of metal atoms is mainly determined by their size, making the diffusion rate of Cu faster than those of other metal atoms. Nevertheless, in the monolayer MoS2, the strain energy is negligible and the electronic coupling is significant, so that the strong d–d coupling between occupied Cu d and unoccupied cation d states leads to the highest diffusion barrier of Cu atoms.

Porous carbons have long been used in the field of Li-ion batteries (LIB); the disorder of the pore alignment, however, limits the performance. Here, we theoretically design more than 120 carbon foams (CFs), in which ordered one-dimensional nanopores are surrounded by interconnected graphene nanoribbons (GNRs). First-principles calculations demonstrate that these CFs exhibit good stabilities and pore-size dependent electronic properties, which are related to the size-dependent band gaps of GNRs. This gives clues for designing metallic CF networks, which provide a high electronic conductivity for anodes. Further using these CFs as anode materials of LIBs, it is found that 6612Z_SIVI combined with the metallicity, a high rate capacity could be expected. Our results reveal the potential applications of CFs in LIBs with high performances, as well as in electronic devices due to the excellent electronic properties.

Dopability in semiconductors plays a crucial role in device performance. Using the first-principles density-functional theory calculations, we investigate systematically the doping properties of layered MX2 (M = Mo, W; X = S, Te) by replacing M or X with the groups III, V and VII elements. It is found that the defect BM is hard to form in MX2 due to the large formation energy originating from the crystal distortion, while AlM is easy to realize compared to the former. In MoS2, WS2 and MoTe2, Al is the most desirable p-type dopant under anion-rich conditions among the group III components. With respect to the doping of the group V elements, it is found that the substitutions on the cation sites have deeper defect levels than those on the anion sites. AsTe and SbTe in MoTe2 and WTe2 are trend to form shallow acceptors under cation-rich conditions, indicating high hole-concentrations for p-type doping, whereas SbS in MoS2 and PTe in WTe2 are shown to be good p-type candidates under cation-rich conditions. In despite of that the substitutions of group VII on X site have low formation energies, the transition energies are too high to achieve n-type MoS2 and WS2. Nevertheless, for MoTe2, the substitutions with the group VII elements on the anion sites are suitable for n-type doping on account of the shallow donor levels and low formation energies under Mo-rich condition. As to WTe2, F is the only potential donor due to the shallow transition energy of FTe. Our findings of filtering out unfavorable and identifying favorable dopants in MX2 are very valuable for experimental implementations.

Penta-hexa-graphene (PHG) is the name given to a novel puckered monolayer of carbon atoms tightly packed into an inerratic mixing pentagonal and hexagonal network. Theoretically, it exhibits excellent electronic properties and can be rolled into penta-hexa-graphene nanotubes (PHGNTs). By using first-principles combined with density functional theory, the PHGNTs with two types of chirality and different diameters were studied. Studies show that not only the nanotubes have intrinsic magnetic properties, but also the magnetic ground state changes with the tube diameter. Interestingly, the nanotubes exhibit semiconducting properties that do not vary with chirality in the antiferromagnetic (AFM) state. And in the ferromagnetic (FM) state, the materials realize the transitions from metal to spin gapless semiconductors (SGS), and to semiconductor with the change of tube diameter. Furthermore, first-principles calculation shows that PHGNTs exhibit diverse electronic properties when the external electrical field is applied, ranging not only from semiconductor to SGS and to metal, but also from semiconductor to half-metal and to metal. Our simulations have an impact on their possible applications in spintronic devices.

Doping, which is the intentional introduction of impurities into a material, can improve the metal-semiconductor interface by reducing Schottky barrier width. Here, we present high-quality two-dimensional SnS2 nanosheets with well-controlled Sb doping concentration via direct vapor growth approach and following micromechanical cleavage process. X-ray photoelectron spectroscopy (XPS) measurement demonstrates that Sb contents of the doped samples are approximately 0.22%, 0.34% and 1.21%, respectively, and doping induces the upward shift of the Fermi level with respect to the pristine SnS2. Transmission electron microscopy (TEM) characterization exhibits that Sb-doped SnS2 nanosheets have a high-quality hexagonal symmetry structure and Sb element is uniformly distributed in the nanosheets. The phototransistors based on the Sb-doped SnS2 monolayers show n-type behavior with high mobility which is one order of magnitude higher than that of pristine SnS2 phototransistors. The photoresponsivity and external quantum efficiency (EQE) of Sb-SnS2 monolayers phototransistors are approximately three orders of magnitude higher than that of pristine SnS2 phototransistor. The results suggest that the method of reducing Shottky barrier width to achieve high mobility and photoresponsivity is effective, and Sb-doped SnS2 monolayer has significant potential in future nanoelectronic and optoelectronic applications.

Generating and manipulating valley polarization in a controlled method is significant. The inherently broken centrosymmetry of the buckled honeycomb structures gives it both ferroelectricity and valley degree of freedom, which provides an opportunity to realize electrically controlled valley polarization. In the first step, we explored the origin of buckling. The hexagonal structure is polar due to buckling of the surface, but the degree of buckling and the energy barrier to switching electric polarization are determined not solely by the chemical composition. We combined the electronegativity difference, bond length and the distribution of charge density to describe quantificationally the polarity of chemical bonds. It shows the characteristics of relatively long bond-length but relatively small electronegativity-difference. For exploring the ferroelectricity of buckling structures and the behavior of ferroelectric (FE) control of the valley degree of freedom, the [Formula: see text]-GaP is used as a model system to elucidate the strain effect on FE behavior and the magnetic proximity effect on the polarization and switching of valley. We found that the spontaneous polarization is positively correlated with the electronegativity difference within a certain range, and the compression strain can effectively manipulate spontaneous polarization and switch barrier. A combination of the magnetic proximity effect and the inversion of electric polarization can generate and switch valley polarization effectively.