Two-dimensional ferroelastic and ferromagnetic NiOX (X = Cl and Br) with half-metallicity and a high Curie temperature.

Two-dimensional (2D) multiferroic materials with distinctive properties, such as half-metallicity, high Curie temperature (TC), and magnetoelastic coupling, hold potential applications in novel nanoscale spintronic devices, but they are rare. Using density functional theory (DFT) calculations and evolutionary algorithms, we identify new types of 2D NiOX (X = F, Cl and Br) monolayers that are stable in energy, dynamics, thermodynamics, and mechanics. Among them, NiOF is an indirect-gap antiferromagnetic (AFM) semiconductor, while NiOCl and NiOBr are half-metallic materials with ferromagnetic (FM) ordering with a TC of 671 and 692 K and in-plane magnetic anisotropy energies (MAEs) of 541 and 609 µeV per Ni along the x-axis and y-axis, respectively. Notably, ferroelasticity is another important feature of NiOCl and NiOBr monolayers with energy barriers of 234.0 and 151.5 meV per atom, respectively. Moreover, the in-plane magnetic easy axis is strongly coupled to the lattice direction. The coexistence of high ferromagnetism, ferroelasticity, half-metallicity, and magnetoelastic coupling renders NiOCl and NiOBr monolayers great potential for future nanodevices.

Stability and the electronic and optical properties of two-dimensional iridium trihalides with promising applications in photocatalytic water splitting.

Based on density functional theory (DFT) calculations, we systematically investigate the structural stabilities, mechanical, electronic, and optical properties of an unexplored kind of two-dimensional (2D) material IrX3 (X = Cl, Br, I) monolayers. Calculations reveal that IrX3 monolayers have low cleavage energies, making them feasible to be extracted from their 3D layered bulk counterparts, and possess excellent energetic, dynamical, mechanical, and thermodynamic stabilities. The calculated band gaps fall in the range from 1.796 to 2.410 eV, with the conduction band (CB) edge and valence band (VB) edge straddling between the redox potentials of water. Analysis of optical properties shows that the monolayers exhibit large exciton binding energies and good optical absorption in the visible-light and ultraviolet regions. The van der Waals (vdW) heterostructures IrCl3:IrBr3 and IrBr3:IrI3 have type-II band alignment with enhanced charge separation, narrower band gap, and better visible light absorption, suggesting that the heterostructures hold promising applications in photocatalytic water splitting.

Large exciton binding energy, superior mechanical flexibility, and ultra-low lattice thermal conductivity in BiI3monolayer.

The exciton binding energy, mechanical properties, and lattice thermal conductivity of monolayer BiI3are investigated on the basis of first principle calculation. The excitation energy of monolayer BiI3is predicted to be 1.02 eV, which is larger than that of bulk BiI3(0.224 eV). This condition is due to the reduced dielectric screening in systems. The monolayer can withstand biaxial tensile strain up to 30% with ideal tensile strength of 2.60 GPa. Compared with graphene and MoS2, BiI3possesses superior flexibility and ductility due to its large Poisson's ratio and smaller Young's modulus by two orders of magnitude. The predicted lattice thermal conductivitykLof monolayer BiI3is 0.247 W m-1 K-1at room temperature, which is lower than most reported values for other 2D materials. Such ultralowkLresults from the scattering between acoustic and optical phonon modes, heavy atomic mass, and relatively weak chemical bond.

Two-dimensional hexagonal chromium chalco-halides with large vertical piezoelectricity, high-temperature ferromagnetism, and high magnetic anisotropy.

On the basis of density functional theory, we predicted that Janus CrTeI and CrSeBr monolayers possess highly energetic, dynamical, and mechanical stability. Due to noncentral symmetry, the two monolayers exhibit vertical piezoelectricity with large piezoelectric coefficients d31 (1.745 and 1.716 pm V-1 for CrBSe and CrTeI, respectively), which are larger than those of most materials in existence. Both systems are also ferromagnetic (FM) semiconductors, with Curie temperature (TC) higher than 550 K and large in-plane magnetic anisotropy energy. Superexchange interactions are responsible for high-temperature FM order. A semiconductor to half metal transition can be regulated by carrier doping, which can be carried out by gate voltages. Doped systems still retain the same FM order as pristine ones; in particular, hole doping enhances exchange coupling, thereby increasing TC. The combination of piezoelectricity, high TC, and controllable electronic structures and magnetic properties makes magnetic 2D Janus CrSeBr and CrTeI attractive materials for potential applications in nanoelectronics, electromechanics, and spintronics.

Theoretical discovery of novel two-dimensional VA-N binary compounds with auxiticity.

Auxetic materials, which possess a negative Poisson's ratio (NPR), have been a hot topic in materials science research. Through atomistic simulations, we theoretically rediscover a few novel two-dimensional (2D) VA-nitride (VA-N) binary compounds with δ-phosphorene-like structures. The structures in the δ-phase (except for δ-PN) exhibit better stability in terms of energy, thermodynamics, and mechanics with respect to their counterparts in the α- and ß-phases. The structures in the δ-phase show semiconducting behaviors with direct band gaps falling in the visible light region. Interestingly, most structures in the α- and δ-phases (except for δ-BiN) exhibit large in-plane NPRs and excellent mechanical properties. The maximum NPR occurs along the zigzag (x) direction for the δ-phases and along the diagonal direction for the α-phases. Particularly, for α- and δ-SbN, the NPRs are -0.628 and -0.296, respectively. δ-SbN can sustain tensile strains of up to 22% and 35% with maximum stresses of 12.1 and 9.8 GPa in the zigzag and armchair directions, respectively. In addition, the transverse response can reach up to 6.6% at a strain of ∼18% along the armchair (y) direction for δ-SbN, which is considerably higher than those of other 2D auxetic materials. Our results reveal that 2D VA-N binary compounds have potential applications in designing 2D electromechanical and optoelectronic devices.

A first-principles study of the SnO2 monolayer with hexagonal structure.

We report the structural, electronic, magnetic, and elastic properties of a two-dimensional (2D) honeycomb stannic oxide (SnO2) monolayer based on comprehensive first-principles calculations. The free-standing and well-ordered 2D centered honeycomb SnO2 (T-SnO2) monolayer with D3d point-group symmetry has good dynamical stability, as well as thermal stability at 500 K. The T-SnO2 monolayer is a nonmagnetic wide-bandgap semiconductor with an indirect bandgap of 2.55/4.13 eV obtained by the generalized gradient approximation with the Perdew-Burke-Ernzerhof/Heyd-Scuseria-Ernzerhof hybrid functional, but it acquires a net magnetic moment upon creation of a Sn vacancy defect. The elastic constants obtained from the relaxed ion model show that the T-SnO2 monolayer is much softer than MoS2. The bandgap monotonically decreases with increasing strain from -8% to 15%. An indirect-to-direct bandgap transition occurs upon applying biaxial strain below -8%. Synthesis of the T-SnO2 monolayer is proposed. We identify the Zr(0001) surface as being suitable to grow and stabilize the T-SnO2 monolayer. The unique structure and electronic properties mean that the T-SnO2 monolayer has promising applications in nanoelectronics. We hope that the present study on the stable free-standing SnO2 monolayer will inspire researchers to further explore its importance both experimentally and theoretically.

Half-metallic and magnetic properties in nonmagnetic element embedded graphitic carbon nitride sheets.

We have investigated the structures, electronic structures and magnetic properties of the triazine-based g-C3N4 (gt-C3N4) monolayer doped with B, Al, and Cu atoms based on density functional theory using ab initio calculations. The B atom prefers to be situated at the center of the triazine ring, whereas the Al and Cu atoms tend to be located above the center of the triazine ring. The doping at the interstitial sites results in nonplanar structures which are thermodynamically stable. Each dopant atom induces a total magnetic moment of 1.0 µB which mainly arises from the pz orbitals because the n-type doping injects unpaired electrons into anti-π orbitals. The results obtained from the GGA-PBE and HSE06 schemes show that all the doped systems exhibit half-metallic behaviors. B- and Al-doped systems are at a ferromagnetic ground state, while the Cu-doped case is at an anti-ferromagnetic ground state. The long-range half-metallic ferromagnetic order is attributed to the p-p interactions. In particular, the estimated Curie temperature implies that the systems doped with B are potential candidates for spintronics applications in future.

Effect and mechanism of Danhong injection on isolated mesenteric arterial rings in rats / 中国中药杂志

<p><b>OBJECTIVE</b>To study the effect and mechanism of Danhong injection on isolated mesenteric arterial rings in rats.</p><p><b>METHOD</b>An isolated vascular ring experiment was conducted to determine the changes in tension of vascular rings with a biological signal collection and analytical system.</p><p><b>RESULT</b>Danhong injection had no impact on the tension of vascular rings. Danhong injection showed a significant vasodilatation effect on treated arteria rings of norepinephrine, and no remarkable impact was made on the effect without endothium. It showed notable effect on blood vessels treated with Ca(2+) and no significant impact on those treated with caffeine. It could inhibit NE-induced intracellular calcium from releasing and external calcium from inflowing. No effects of potassium channel blockers on aorta ring tensile force were found.</p><p><b>CONCLUSION</b>Danhong injection shows significant vasodilation effect, which mainly works through vascular smooth muscle. Its vasodilation effect may be related to inhibitory receptor, voltage-dependent Ca(2+)-release and IP3 receptor-mediated Ca(2 +)-influx.</p>

Effect of hyperbaric oxygen on demineralized bone matrix and biphasic calcium phosphate bone substitutes.

OBJECTIVES: The aim of this study was to assess the possible effect of hyperbaric oxygen (HBO) on the healing of critical-sized defects that were grafted with demineralized bone matrix (DBM) combined with Pluronic F127 (F127) to form a gel or putty, or a commercially available biphasic calcium phosphate (BCP), mixed either with blood or F127 to form a putty. STUDY DESIGN: Twenty New Zealand White rabbits were randomly divided into 2 groups of 10 animals each. Bilateral 15-mm calvarial defects were created in the parietal bones of each animal, resulting in 40 critical-sized defects. Group I defects were grafted with either DBM putty or DBM gel. Group II defects were grafted with either BCP or BCP putty. Five animals from each group received HBO treatment (100% oxygen, at 2.4 ATA) for 90 minutes per day 5 days a week for 4 weeks. The other 5 animals in each group served as a normobaric (NBO) controls, breathing only room air. All animals were humanely killed at 6 weeks. The calvariae were removed and analyzed by micro computed tomography (mCT) and histomorphometry. RESULTS: mCT analysis indicated a higher bone mineral content (BMC, P < .05), bone volume fraction (BVF; P < .001), and bone mineral density (BMD; P < .001) of the defects grafted with BCP rather than DBM. Furthermore, the voxels that were counted as bone had a higher tissue mineral density (TMD) in the BCP- than in the DBM-filled defects (P < .001). Histologically complete bony union over the defects was observed in all specimens. Histomorphometric analysis showed that DBM-filled defects had more new bone (P < .007) and marrow (P < .001), and reduced fibrous tissue compared with the BCP defects (P < .001) under NBO conditions. HBO treatment reduced the amount of fibrous tissue in BCP filled defects (P < .05), approaching levels similar to that in matching DBM-filled defects. HBO also resulted in a small but significant increase in new bone in DBM-grafted defects (P < .05). CONCLUSION: Use of DBM or BCP promoted healing in these critical-sized defects. Hyperbaric oxygen therapy resulted in a slight increase in new bone in DBM-grafted defects and much larger reduction in fibrous tissue and matching increases in marrow in BCP-grafted defects, possibly through increased promotion of angiogenesis.