Tip Growth of Quasi-Metallic Bilayer Graphene Nanoribbons with Armchair Chirality.

Graphene nanoribbons (GNRs), quasi one-dimensional (1D) narrow strips of graphene, have shown promise for high-performance nanoelectronics due to their exceptionally high carrier mobility and structurally tunable bandgaps. However, producing chirality-uniform GNRs on insulating substrates remains a big challenge. Here, we report the successful growth of bilayer GNRs with predominantly armchair chirality and ultranarrow widths (<5 nm) on insulating hexagonal boron nitride (h-BN) substrates using chemical vapor deposition (CVD). The growth of GNRs is catalyzed by transition metal nanoparticles, including Fe, Co, and Ni, through a unique tip-growth mechanism. Notably, GNRs catalyzed by Ni exhibit a high purity (97.3%) of armchair chirality. Electron transport measurements indicate that the ultrathin bilayer armchair GNRs exhibit quasi-metallic behavior. This quasi-metallicity is further supported by density functional theory (DFT) calculations, which reveal a significantly reduced bandgap in bilayer armchair GNRs. The chirality-specific GNRs reported here offer promising advancements for the application of graphene in nanoelectronics.

Anisotropic Interlayer Force Field for Group-VI Transition Metal Dichalcogenides.

An anisotropic interlayer force field that describes the interlayer interactions in homogeneous and heterogeneous interfaces of group-VI transition metal dichalcogenides (MX2, where M = Mo, W, and X = S, Se) is presented. The force field is benchmarked against density functional theory calculations for bilayer systems within the Heyd-Scuseria-Ernzerhof hybrid density functional approximation, augmented by a nonlocal many-body dispersion treatment of long-range correlation. The parametrization yields good agreement with the reference calculations of binding energy curves and sliding potential energy surfaces. It is found to be transferable to transition metal dichalcogenide (TMD) junctions outside of the training set that contain the same atom types. Calculated bulk moduli agree with most previous dispersion-corrected density functional theory predictions, which underestimate the available experimental values. Calculated phonon spectra of the various junctions under consideration demonstrate the importance of appropriately treating the anisotropic nature of the layered interfaces. Considering our previous parametrization for MoS2, the anisotropic interlayer potential enables accurate and efficient large-scale simulations of the dynamical, tribological, and thermal transport properties of a large set of homogeneous and heterogeneous TMD interfaces.

Sepiolite and ZIF-67 co-modified PAN/PVdF-HFP nanofiber separators for advanced Li-ion batteries.

Electrospun PAN/PVdF-HFP membranes have the potential to be used as separators for Li-ion batteries owing to their good mechanical properties and high chemical stability. However, the application of PAN/PVdF-HFP separators has been hampered by their poor electrochemical performances. In this study, semi-aligned PAN/PVdF-HFP nanofiber separators have been fabricated by an electrospinning technology. Sepiolite and ZIF-67 co-modification was employed to enhance the physical properties of the PAN/PVdF-HFP separators. The test cells with the as-prepared composite separator showed better electrochemical performance than the commercial and raw PAN/PVdF-HFP separators.

Co9S8 nanoparticles embedded into amorphous carbon as anode materials for lithium-ion batteries.

In this paper, Co9S8 nanoparticles embedded into amorphous carbon have been synthesized by a simple electrospinning method followed by a high-temperature annealing process. The unique structure endows the Co9S8/C composites with excellent electrochemical properties. Co9S8 particles embedded into the carbon matrix show a high Li storage capacity around 1100 and 358 mAhg-1 at a current density of 0.1 and 5.0 Ag-1, respectively. After 200 cycles, an impressive discharge capacity of around 1063.4 mAhg-1 can be obtained at a current density of 0.3 Ag-1.

Anisotropic semi-aligned PAN@PVdF-HFP separator for Li-ion batteries.

Compared with the common electrospun nanofibers, the alignment of the nanofibers exhibits interesting anisotropic mechanical properties and structural stability. In this paper, semi-aligned PAN@PVdF-HFP nanofiber separators were prepared by a modified electrospinning method. The composite separators exhibit anisotropic mechanical properties and enhanced electrochemical performance compared with electrospun PAN films. The PAN@PVdF-HFP nanofiber separator can deliver an ionic conductivity of 1.2 mSccm-1 with electrochemical stability up to 5.0 V. The LiFePO4/Li cell with semi-aligned PAN@PVdF-HFP separator shows excellent cycling performance, good rate capability, as well as high discharge capacity.

Endoscopic Surgery versus Minimal Puncture Drainage Surgery for Treatment of Supratentorial Intracerebral Hemorrhage.

AIM: To compare neuroendoscopy versus minimal puncture drainage for surgical treatment of supratentorial hypertensive intracerebral hemorrhage. MATERIAL AND METHODS: A total of 108 cases involving supratentorial intracerebral hemorrhage were retrospectively analyzed. In 30 cases, endoscopic surgery was performed, while 78 cases involved puncture surgery. We compared hematoma clearance rate, postoperative rebleeding rate, incidence of postoperative complications, operation duration, and Glasgow coma score seven days after surgery. Clinical data such as early postoperative rehabilitation time, Glasgow outcome score three months after surgery, and intensive care unit (ICU) stay were also compared between the two groups. RESULTS: The results showed that endoscopic surgery was associated with a superior clinical therapeutic effect in hematoma clearance rates, GCS scores on postoperative day 7, the average ICU stay, early postoperative rehabilitation time and intracranial infection outcomes than minimal puncture drainage surgery for the treatment of supratentorial intracerebral hemorrhage (p < 0.05). Three months after surgery, the favorable prognosis rate in the endoscopic treatment group was significantly higher than that in the craniotomy group [83.3% (28/34) vs. 61.5% (31/51), respectively; ? < sup > 2 < /sup > =4.698, p=0.030]. In contrast, no significant differences in rebleeding, pulmonary infection, tracheotomy, secondary epilepsy, gastrointestinal hemorrhage, death in late postoperative period, or in baseline parameters were observed between the two groups (p > 0.05). CONCLUSION: Endoscopic surgery potentially represents a beneficial surgical procedure for treatment of supratentorial spontaneous intracerebral hemorrhage.

Sodium hydrosulfide attenuates cerebral ischemia/reperfusion injury by suppressing overactivated autophagy in rats.

Ischemic stroke is a leading cause of death and disability worldwide, and autophagy may be involved in the pathological process of cerebral ischemia/reperfusion injury. Hydrogen sulfide (H2S) is an endogenous gasotransmitter with protective effects against multiple diseases. Here, we tested the effect of H2S on cerebral ischemia/reperfusion injury in rats. Sodium hydrosulfide (NaHS), an H2S donor, improved neurological function and reduced the size of the infarcts induced by transient middle cerebral artery occlusion (MCAO) followed by reperfusion in rats. NaHS treatment reduced the lactate dehydrogenase (LDH) activity in the serum (a marker of cellular membrane integrity) and the expression of cleaved caspase-3 (a marker for apoptosis) in the brains of MCAO rats. We also found that autophagy was overactivated in the brains of MCAO rats, as indicated by an increased ratio of LC3 II to I, decreased expression of p62, and transmission electron microscope detection. NaHS treatment significantly inhibited the autophagic activity in the brains of MCAO rats. Furthermore, PC12 cells were subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) to mimic MCAO in vitro. We found that NaHS treatment reduced cellular injury and suppressed overactivated autophagy induced by OGD/R in PC12 cells. An autophagy stimulator (rapamycin) eliminated the protective effect of NaHS against LDH release and caspase-3 activity induced by OGD/R in PC12 cells. An autophagy inhibitor (3-methyladenine, 3-MA) also reduced the cellular injury induced by OGD/R in PC12 cells. In conclusion, the results indicate that overactivated autophagy accelerates cellular injury after MCAO in rats and that exogenous H2S attenuates cerebral ischemia/reperfusion injury via suppressing overactivated autophagy in rats.