Predicting the potential distribution of Campsis grandiflora in China under climate change.

Because the research on the geographical distribution of species significantly influences people's understanding of species protection and utilization, it is important to study the influence of climate change on plants' geographical distribution patterns. Based on 166 distribution records and 11 climate and terrain variables, we used MaxEnt (Maximum Entropy) model and ArcGIS software to predict the potential distribution of Campsis grandiflora under climate change and then determined the dominant climate variables that significantly affected its geographical distribution. In our study, the area under the curve (AUC) value of the training data was 0.939, proving the accuracy of our prediction. Under current climate conditions, the area of potentially suitable habitat is 238.29 × 104 km2, mainly distributed in northern, central, southern, and eastern China. The dominant variables that affect the geographical distribution of C. grandiflora are temperature, precipitation and altitude. In the future climate change scenario, the total area of suitable habitat and highly suitable habitat will increase, whereas the area of moderately suitable habitat and poorly suitable habitat will decrease. In addition, the centroid of the potentially suitable area of C. grandiflora will migrate to higher latitude and higher altitudes areas. The results could give strategic guidance for development, protection, and utilization of C. grandiflora in China.

Direct/indirect band gap tunability in van der Waals heterojunctions based on ternary 2D materials Mo1-x W x Y2.

Artificial van der Waals (vdW) heterojunctions assembled by atomically-thin two-dimensional (2D) materials have demonstrated new physical phenomena and unusual properties, thus triggering new electronic, optoelectronic, valleytronic and photocatalytic application. Herein, the electronic band structures of different vdW heterojunctions based on ternary Mo1-x W x Y2 (Y = S, Se; x = 0-1) monolayer with five stacking orders (AA, AA[Formula: see text], A[Formula: see text]B, AB, AB[Formula: see text]) have been investigated using first principle calculations. The direct/indirect band gap has been obtained in the AA[Formula: see text] stacking type-II heterojunctions, ranging from 0.538 eV to 1.260 eV, that are determined by the interlayer distances and stoichiometries. The estimated power conversion efficiency of the AA[Formula: see text] stacking type-II heterojunction varied from 9.1% to 23.4%. The type-I heterojunctions have also been predicted when semiconducting 2H-MoTe2 monolayer stacks with the specific Mo1-x W x Se2 monolayer, which are MoTe2/Mo0.25W0.75Se2 and MoTe2/Mo0.5W0.5Se2. The reported theoretical results can provide broader 2D materials design possibility for the functional devices.

Electronic and magnetic properties of phosphorene tuned by Cl and metallic atom co-doping.

Using first-principles calculations based on density functional theory, we studied the electronic and magnetic properties of phosphorene co-doped with Cl and a metal atom (including Sc, Ti, V, Cr, Mn, Fe, Co, and Ni). It is found that Cl atom doping makes it much easier for metallic atoms to dope into phosphorene. Phosphorene co-doped with Cl and V, Cr, Mn, or Fe is magnetic, which is determined by the number of valence electrons. Taking V-Cl and Co-Cl co-doped phosphorene as an example, analyses are carried out on the reasonable selection of the doping sites, which distinctly affect the stability, band gap and magnetic moment. The stability is closely relevant to the electronegativity of impurity atoms. With the biaxial strain ranging from -4% to 4%, the magnetic moment of V-Cl co-doped phosphorene and the band gap of Co-Cl co-doped phosphorene are greatly tunable between 1.757-0.951 µB and 0.687-0.496 eV, which come from the electron transfer from V to the surrounding P atoms and the weakened bond between Co and Cl, respectively. These investigations provide a reference for regulating the electronic structure and magnetic properties of diluted magnetic semiconductors and promote the applications of phosphorene in spintronics and nanodevices.

Superconductivity in Li-intercalated bilayer arsenene and hole-doped monolayer arsenene: a first-principles prediction.

Using first-principles calculations, we find Li-intercalated bilayer arsenene with AB stacking is dynamically stable, which is different from pristine bilayer with AA stacking. Electron-phonon coupling of the stable Li-intercalated bilayer arsenene are dominated by the low frequency vibrational modes (E″(1), [Formula: see text](1), E'(1) and acoustic modes) and lead to an superconductivity with T c = 8.68 K with isotropical Eliashberg function. Small biaxial tensile strain (2%) can improve T c to 11.22 K due to the increase of DOS and phonon softening. By considering the fully anisotropic Migdal-Eliashberg theory, T c are found to be enhanced by 50% and exhibits a single anisotropic gap nature. In addition, considering its nearly flat top valence band which is favorable for high temperature superconductivity, we also explore the superconducting properties of hole-doped monolayer arsenene under different strains. the unstrained monolayer arsenene superconducts at T c = 0.22 K with 0.1 hole/cell doping. By applying 3% biaxial strain, T c can be lifted up strikingly to 6.69 K due to a strong Fermi nesting of the nearly flat band. Then T c decreases slowly with strain. Our findings provide another insight to realize 2D superconductivity and suggest that the strain is crucial to further enhance the transition temperature.

Facile synthesis of Bi/BiVO4 composite ellipsoids with high photocatalytic activity.

BiVO4-based composites have been extensively investigated as promising photocatalysts due to their strong visible-light absorption. In this work, novel Bi/BiVO4 composites with excellent photocatalytic performance were firstly fabricated via a simple hydrothermal method, using BiVO4 as a self-sacrificing template and N2H4·H2O as a reductant. In the hydrothermal process, partial BiVO4 was reduced to form metallic Bi nanoparticles, which were deposited on the surface of BiVO4. The Bi content in the Bi/BiVO4 composites could be easily tuned by controlling the concentration of the N2H4·H2O solution. The photocatalytic performance of the Bi/BiVO4 composites was examined by studying the photodecomposition of RhB under visible-light illumination. The experimental results revealed that the Bi/BiVO4 composites exhibit high visible-light photocatalytic activity for the photodegradation of RhB compared with that of pure BiVO4. This enhanced photocatalytic activity likely originates from the strong visible-light absorption and high separation efficiency of photogenerated electron-hole pairs by Bi nanoparticles. This work presents a new approach for the development of Bi/BiVO4 composite photocatalysts with high activity and stability.

Electronic properties and transistors of the NbS2-MoS2-NbS2 NR heterostructure.

Based on density function theory and nonequilibrium Green's functions, we construct a NbS2-MoS2-NbS2 NR inplane heterostructure. The effects of channel length, width, chirality and vacancy of the heterostructure on transport properties are systematically investigated. The electron transport of the armchair-edge heterostructure device shows ballistic transport properties, while the zigzag-edge heterostructure device exhibits resonance tunneling transport properties. Further study indicates NbS2-MoS2-NbS2 field effect transistors (FETs) to be excellent ambipolar transistors. The FETs have high performances with current on/off ratio 4.7 × 105 and subthreshold swing 90 mV/decade with channel length m = 16 and width n = 6.  Increases in the channel length sharply reduce the off-state current and enhance the performance of the devices significantly.

Electronic structures and transport properties of a MoS2-NbS2 nanoribbon lateral heterostructure.

Lateral heterostructures built from an armchair MoS2 nanoribbon (AMoS2NR) and an armchair NbS2 nanoribbon (ANbS2NR) were studied based on first-principles calculations and a non-equilibrium Green's function method. It is found that the work function of the AMoS2NR shows substantial oscillation with increasing nanoribbon width, which is different from the work functions of other kinds of nanoribbons. The AMoS2NR-ANbS2NR lateral heterostructure exhibits an anomalous transport gap that is much larger than the bandgap of the AMoS2NR. As a result, a field effect transistor with AMoS2NR as the channel and ANbS2NRs as electrodes has high on-off ratios of 106-107 and a tiny leakage current of the order of 10-8 µA. These results suggest that lateral metal-semiconductor heterostructures of transition metal dichalcogenides may have potential applications in nanodevices with low energy consumption.