Defect engineering is considered as one of the most efficient strategies to regulate the electronic structure of materials and involves the manipulation of the types, concentrations, and spatial ...distributions of defects, resulting in unprecedented properties. It is shown that a single‐layered MnO2 nanosheet with vacancies is a robust half‐metal, which was confirmed by theoretical calculations, whereas vacancy‐free single‐layered MnO2 is a typical semiconductor. The half‐metallicity of the single‐layered MnO2 nanosheet can be observed for a wide range of vacancy concentrations and even in the co‐presence of Mn and O vacancies. This work enables the development of half‐metals by defect engineering of well‐established low‐dimensional materials, which may be used for the design of next‐generation paper‐like spintronics.
A manganese dioxide monolayer was rendered half‐metallic by a defect engineering strategy, which was confirmed by calculations. These theoretical studies showed that the half‐metallicity of a single‐layered MnO2 nanosheet can be observed for a wide range of vacancy concentrations and even in the presence of both Mn and O vacancies.
As the properties of ultrathin two‐dimensional (2D) crystals are strongly related to their electronic structures, more and more attempts were carried out to tune their electronic structures to meet ...the high standards for the construction of next‐generation smart electronics. Herein, for the first time, we show that the conductive nature of layered ternary chalcogenide with formula of Cu2WS4 can be switched from semiconducting to metallic by hydrogen incorporation, accompanied by a high increase in electrical conductivity. In detail, the room‐temperature electrical conductivity of hydrogenated‐Cu2WS4 nanosheet film was almost 1010 times higher than that of pristine bulk sample with a value of about 2.9×104 S m−1, which is among the best values for conductive 2D nanosheets. In addition, the metallicity in the hydrogenated‐Cu2WS4 is robust and can be retained under high‐temperature treatment. The fabricated all‐solid‐state flexible supercapacitor based on the hydrogenated‐Cu2WS4 nanosheet film shows promising electrochemical performances with capacitance of 583.3 F cm−3 at a current density of 0.31 A cm−3. This work not only offers a prototype material for the study of electronic structure regulation in 2D crystals, but also paves the way in searching for highly conductive electrodes.
Metallic nanosheets: The conductivity of the layered ternary chalcogenide Cu2WS4 is switched from semiconducting to metallic by hydrogen incorporation, accompanied by a strong increase in conductivity. The metallic hydrogenated‐Cu2WS4 nanosheets were applied as electrode material in an all‐solid‐state flexible supercapacitor.
Unsaturated fatty acids (UFAs) are essential for functional membrane phospholipids in most bacteria. The bifunctional dehydrogenase/isomerase FabX is an essential UFA biosynthesis enzyme in the ...widespread human pathogen Helicobacter pylori, a bacterium etiologically related to 95% of gastric cancers. Here, we present the crystal structures of FabX alone and in complexes with an octanoyl-acyl carrier protein (ACP) substrate or with holo-ACP. FabX belongs to the nitronate monooxygenase (NMO) flavoprotein family but contains an atypical 4Fe-4S cluster absent in all other family members characterized to date. FabX binds ACP via its positively charged α7 helix that interacts with the negatively charged α2 and α3 helices of ACP. We demonstrate that the 4Fe-4S cluster potentiates FMN oxidation during dehydrogenase catalysis, generating superoxide from an oxygen molecule that is locked in an oxyanion hole between the FMN and the active site residue His182. Both the 4Fe-4S and FMN cofactors are essential for UFA synthesis, and the superoxide is subsequently excreted by H. pylori as a major resource of peroxide which may contribute to its pathogenic function in the corrosion of gastric mucosa.
Infectious microbes that spread easily in healthcare facilities remain as the severe threat for the public health, especially among immunocompromised populations. Given the intricate problem of ...dramatic increase in resistance to common biocides, the development of safe and efficient biocide formulated agents to alleviate drug resistance is highly demanding. In this study, Schiff-base ligands were successfully formed on natural biopolymer of epsilon-poly-L-lysine (ε-PL) decorated aldehyde functionalized mesoporous silica SBA-15 (CHO-SBA-15) for the selective coordination of silver ions, which was affirmed by various physicochemical methods. Besides the identified broad-spectrum antibacterial activities, the as-prepared Schiff-base silver nanocomplex (CHO-SBA-15/ε-PL/Ag, CLA-1) exhibited an improved inhibitory effect on infectious pathogen growth typified by
Escherichia coli
and
Staphylococcus aureus
in comparison with two control silver complexes without Schiff-base conjugates, SBA-15/ε-PL/Ag and CHO-SBA-15/Ag, respectively. In addition, CLA-1 remarkably inhibited the growth of
Mycobacterium tuberculosis
due to the excellent antimicrobial activity of silver species. Significantly, CLA-1 kills
Candida albicans
cells, inhibits biofilm formation, and eliminates preformed biofilms, with no development of resistance during continuous serial passaging. The antifungal activity is connected to disruption of bacterial cell membranes and increased levels of intracellular reactive oxygen species. In mouse models of multidrug-resistant
C. albicans
infection, CLA-1 exhibited efficient
in vivo
fungicidal efficacy superior to two antifungal drugs, amphotericin B and fluconazole. Moreover, CLA-1 treatment induces negligible toxicity against normal tissues with safety. Therefore, this study reveals the pivotal role of the molecular design of Schiff-base silver nanocomplex formation on biopolymer surface-functionalized silica mesopores as a green and efficient nanoplatform to tackle infectious microbes.
Summary
Antibiotic resistance in Helicobacter pylori has been growing worldwide with current treatment regimens. Development of new compounds for treatment of H. pylori infections is urgently ...required to achieve a successful eradication therapy in the future. Armeniaspirols, a novel class of natural products isolated from Streptomyces armeniacus, have been previously identified as antibacterial agents against Gram‐positive pathogens. In this study, we found that armeniaspirol A (ARM1) exhibited potent antibacterial activity against H. pylori, including multidrug‐resistant strains, with MIC range values of 4–16 μg ml‐1. The underlying mechanism of action of ARM1 against H. pylori involved the disruption of bacterial cell membranes. Also, ARM1 inhibited biofilm formation, eliminated preformed biofilms and killed biofilm‐encased H. pylori in a dose‐dependent manner. In a mouse model of multidrug‐resistant H. pylori infection, dual therapy with ARM1 and omeprazole showed efficient in vivo killing efficacy comparable to the standard triple therapy, and induced negligible toxicity against normal tissues. Moreover, at acidic pH 2.5, ARM1 exhibited a much more potent anti‐H. pylori activity than metronidazole. Thus, these findings demonstrated that ARM1 is a novel potent anti‐H. pylori agent, which can be developed as a promising drug lead for treatment of H. pylori infections.
ARM1, a natural product isolated from S. armeniacus, showed potent antimicrobial activity against H. pylori both in vivo and in vitro. It is a possible drug candidate not only inhibiting planktonic growth and biofilm formation but also disrupting the mature biofilm by permeabilizing bacterial membranes.ARM1 might provide a promising drug lead for the development of anti‐H. pylori therapy.
•New Monte Carlo sampling-based algorithm for coercivity calculation proposed.•Design of AFM-FM exchange-coupled composite magnets.•Magnetic hardening of Fe16N2 for rare-earth-free permanent magnet ...applications.•AFM-Fe16N2 composite magnets have large coercivity and maximum energy product.
Monte Carlo methods are widely used to study magnetism. However, their use to the calculation of coercivity has been problematic because of difficulties in quantifying Monte Carlo time. Here we propose a new approach of studying coercivity based on Monte Carlo sampling of the switching time at different reverse fields. This method allows comparative analysis of how coercivity is affected by various factors without needing time quantification of the Monte Carlo step. We apply the new method to study antiferromagnet-ferromagnet exchange coupling systems and show that practically large coercivity and enhanced maximum energy product can be achieved by properly adding antiferromagnet to high-magnetization ferromagnets such as Fe16N2. The finding is important to the design of new rare-earth-free permanent magnets.
is a major global pathogen, and its infection represents a key factor in the etiology of various gastric diseases, including gastritis, peptic ulcers, and gastric carcinoma. The efficacy of current ...standard treatment for
infection including two broad-spectrum antibiotics is compromised by toxicity toward the gut microbiota and the development of drug resistance, which will likely only be resolved through novel and selective antibacterial strategies. Here, we synthesized a small molecule, zinc linolenate (ZnLla), and investigated its therapeutic potential for the treatment of
infection. ZnLla showed effective antibacterial activity against standard strains and drug-resistant clinical isolates of
with no development of resistance during continuous serial passaging. The mechanisms of ZnLla action against
involved the disruption of bacterial cell membranes and generation of reactive oxygen species. In mouse models of multidrug-resistant
infection, ZnLla showed
killing efficacy comparable and superior to the triple therapy approach when use as a monotherapy and a combined therapy with omeprazole, respectively. Moreover, ZnLla treatment induces negligible toxicity against normal tissues and causes minimal effects on both the diversity and composition of the murine gut microbiota. Thus, the high degree of selectivity of ZnLla for
provides an attractive candidate for novel targeted anti-
treatment.
is a major global pathogen and has been implicated in gastritis, peptic ulcer, and gastric carcinoma. The efficacy of the extensive therapy of
infection with antibiotics is compromised by the ...development of drug resistance and toxicity toward human gut microbiota, which urgently demands novel and selective antibacterial strategies. The present study was mainly performed to assess the
and
effects of a natural herbal compound, dihydrotanshinone I (DHT), against standard and clinical
strains. DHT demonstrated effective antibacterial activity against
(MIC
, 0.25/0.5 μg/ml), with no development of resistance during continuous serial passaging. Time-kill curves showed strong time-dependent bactericidal activity for DHT. Also, DHT eliminated preformed biofilms and killed biofilm-encased
cells more efficiently than the conventional antibiotic metronidazole. In mouse models of multidrug-resistant
infection, dual therapy with DHT and omeprazole showed
killing efficacy superior to that of the standard triple-therapy approach. Moreover, DHT treatment induces negligible toxicity against normal tissues and exhibits a relatively good safety index. These results suggest that DHT could be suitable for use as an anti-
agent in combination with a proton pump inhibitor to eradicate multidrug-resistant
.
•Proposed a strategy to enhance the coercivity of rare-earth-free magnets.•Permanent magnet design out of high-magnetization materials such as Fe16N2.•Quantified the trade-off between saturation ...magnetization and coercivity.•Clarified some practical aspects of Monte Carlo simulations of hysteresis loops.
In the pursuit of rare-earth-free permanent magnets, materials with large saturation magnetization (Ms) stand out. However, large Ms results in low anisotropy field, thus additional source of coercivity is needed to make useful magnets for a broad range of applications. In this paper, we investigate the use of interface coupling to an antiferromagnet (AFM) as a means to increase coercivity for permanent magnet design. Results on the effects of Néel temperature, AFM anisotropy, interface coupling strength, AFM volume ratio, as well as temperature dependence are obtained using Monte Carlo (MC) simulations. And before that, we clarify some practices in MC simulations of magnetic hysteresis. The origin of coercivity enhancement is investigated by examining the magnetization reversal process, which is found to agree with well-established theory of exchange bias. Finally, discussions and design suggestions are made on the AFM materials, the geometry, and experimental realization.
Perpendicular magnetic materials with low damping constant and high thermal stability have great potential for realizing high-density, non-volatile, and low-power consumption spintronic devices, ...which can sustain operation reliability for high processing temperatures. In this work, we study the Gilbert damping constant (α) of perpendicularly magnetized W/CoFeB/MgO films with a high perpendicular magnetic anisotropy (PMA) and superb thermal stability. The α of these PMA films annealed at different temperatures (T
) is determined via an all-optical Time-Resolved Magneto-Optical Kerr Effect method. We find that α of these W/CoFeB/MgO PMA films decreases with increasing T
, reaches a minimum of α = 0.015 at T
= 350 °C, and then increases to 0.020 after post-annealing at 400 °C. The minimum α observed at 350 °C is rationalized by two competing effects as T
becomes higher: the enhanced crystallization of CoFeB and dead-layer growth occurring at the two interfaces of the CoFeB layer. We further demonstrate that α of the 400 °C-annealed W/CoFeB/MgO film is comparable to that of a reference Ta/CoFeB/MgO PMA film annealed at 300 °C, justifying the enhanced thermal stability of the W-seeded CoFeB films.
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