Efficient synthesis of biazoles by aerobic oxidative homocoupling of azoles catalyzed by a copper(I)/2-pyridonate catalytic system.

A highly efficient and convenient CuCl/2-pyridonate catalytic system for oxidative homocoupling of azoles affording a biazole product has been developed. With this system, a variety of biazoles have been effectively synthesized in good to excellent yields in the presence of a very small amount of copper catalyst (1.0 mol%). It was feasible to employ air as a green oxidant

Phagraphene: A Low-energy Graphene Allotrope composed of 5-6-7 Carbon Rings with Distorted Dirac Cones

Using systematic evolutionary structure searching we propose a new carbon allotrope, phagraphene, standing for penta-hexa-hepta-graphene, because the structure is composed of 5-6-7 carbon rings. This two-dimensional (2D) carbon structure is lower in energy than most of the predicted 2D carbon allotropes due to its sp2-hybridization and density of atomic packing comparable to graphene. More interestingly, the electronic structure of phagraphene has distorted Dirac cones. The direction-dependent cones are further proved to be robust against external strain with tunable Fermi velocities.Comment: 5 pages, 3 figure

Propagation and Pitfalls: Reasoning-based Assessment of Knowledge Editing through Counterfactual Tasks

Current approaches of knowledge editing struggle to effectively propagate updates to interconnected facts. In this work, we delve into the barriers that hinder the appropriate propagation of updated knowledge within these models for accurate reasoning. To support our analysis, we introduce a novel reasoning-based benchmark -- ReCoE (Reasoning-based Counterfactual Editing dataset) -- which covers six common reasoning schemes in real world. We conduct a thorough analysis of existing knowledge editing techniques, including input augmentation, finetuning, and locate-and-edit. We found that all model editing methods show notably low performance on this dataset, especially in certain reasoning schemes. Our analysis over the chain-of-thought generation of edited models further uncover key reasons behind the inadequacy of existing knowledge editing methods from a reasoning standpoint, involving aspects on fact-wise editing, fact recall ability, and coherence in generation. We will make our benchmark publicly available.Comment: 22 pages, 14 figures, 5 table

Fluorination-induced magnetism in boron nitride nanotubes from ab initio calculations

Ab initio calculations were conducted to investigate the electronic structures and magnetic properties of fluorinated boron nitride nanotube (F-BNNT). It was found that the chemisorption of F atoms on the B atoms of BNNT can induce spontaneous magnetization, whereas no magnetism can be produced when the B and N atoms are equally fluorinated. This provides a different approach to tune the magnetic properties of BNNTs as well as a synthetic route toward metal-free magnetic materials.<br /

Enhancement of hydrogen physisorption on single-walled carbon nanotubes resulting from defects created by carbon bombardment

The defect effect on hydrogen adsorption on single-walled carbon nanotubes (SWNTs) has been studied by using extensive molecular dynamics simulations and density functional theory (DFT) calculations. It indicates that the defects created on the exterior wall of the SWNTs by bombarding the tube wall with carbon atoms and C-2 dimers at a collision energy of 20 eV can enhance the hydrogen adsorption potential of the SWNTs substantially. The average adsorption energy for a H-2 molecule adsorbed on the exterior wall of a defected (10,10) SWNT is similar to 150 meV, while that for a H-2 molecule adsorbed on the exterior wall of a perfect (10,10) SWNT is similar to 104 meV. The H-2 sticking coefficient is very sensitive to temperature, and has a maximum value around 70 to 90 K. The electron density contours, the local density of states, and the electron transfers obtained from the DFT calculations clearly indicate that the H-2 molecules are all physisorbed on the SWNTs. At temperatures above 200 K, most of the H-2 molecules adsorbed on the perfect SWNT are soon desorbed, but the H-2 molecules can still remain on the defected SWNTs at 300 K. The detailed processes of H-2 molecules adsorbing on and desorbing from the (10,10) SWNTs are demonstrated

Bioactive Electrospun Scaffolds Delivering Growth Factors and Genes for Tissue Engineering Applications

A biomaterial scaffold is one of the key factors for successful tissue engineering. In recent years, an increasing tendency has been observed toward the combination of scaffolds and biomolecules, e.g. growth factors and therapeutic genes, to achieve bioactive scaffolds, which not only provide physical support but also express biological signals to modulate tissue regeneration. Huge efforts have been made on the exploration of strategies to prepare bioactive scaffolds. Within the past five years, electrospun scaffolds have gained an exponentially increasing popularity in this area because of their ultrathin fiber diameter and large surface-volume ratio, which is favored for biomolecule delivery. This paper reviews current techniques that can be used to prepare bioactive electrospun scaffolds, including physical adsorption, blend electrospinning, coaxial electrospinning, and covalent immobilization. In addition, this paper also analyzes the existing challenges (i.e., protein instability, low gene transfection efficiency, and difficulties in accurate kinetics prediction) to achieve biomolecule release from electrospun scaffolds, which necessitate further research to fully exploit the biomedical applications of these bioactive scaffolds

High activity and durability of novel perovskite electrocatalysts for water oxidation

Development of highly active and cost-effective electrocatalysts is central to the large-scale electrolysis of water for renewable energy generation. Perovskite oxides are a group of promising candidates to lower the oxygen evolution reaction (OER) barriers in water splitting and further improvement of their activity and durability is an important objective. Here we report scandium and niobium cation (Sc3+ and Nb5+) doped strontium cobaltite perovskites (SrScxNbyCo1-x-yO3-δ) as a family of highly active and durable electrocatalysts for the OER in alkaline solution. These perovskites not only manifest up to a factor of 50 increase of the intrinsic activity compared to the gold-standard OER electrocatalysts (such as IrO2 and RuO2) and a factor of 5.8 enhancement to the perovskite-Ba0.5Sr0.5Co0.8Fe0.2O3-δ at an overpotential of 0.35 V, but also, more importantly, show excellent durability in alkaline solutions under operation

A comparative study of SrCo0.8Nb0.2O3-δ and SrCo0.8Ta0.2O3-δ as low-temperature solid oxide fuel cell cathodes: effect of non-geometry factors on the oxygen reduction reaction

The oxygen reduction reaction (ORR) activity of cathodes has to be improved to realize the low-temperature operation of solid-oxide fuel cells (SOFCs). Whilst geometric factors are conventionally accepted to influence the ORR activity of perovskite cathodes, other factors may also contribute and therefore need to be explored. Here, we substituted 20% niobium and tantalum which have similar ionic radii into strontium cobaltites to obtain the two perovskite oxides SrCo0.8Nb0.2O3-delta (SCN20) and SrCo0.8Ta0.2O3-delta (SCT20), respectively. Our study of the isostructural SCN20 and SCT20 allows geometric effects to be separated from other factors, and we observe better cathode performance of SCT20 cathode, which may be related to the lower electronegativity of Ta5+, thus resulting in higher oxygen surface exchange kinetics and diffusivity as compared with Nb5+