MXene-based Ti2C/Ta2C lateral heterostructure: an intrinsic room temperature ferromagnetic material with large magnetic anisotropy.

Two-dimensional (2D) lateral heterostructures (LH) combining Ti2C and Ta2C MXenes were investigated by means of first-principles calculations. Our structural and elastic properties calculations show that the lateral Ti2C/Ta2C heterostructure results in a 2D material that is stronger than the original isolated MXenes and other 2D monolayers such as germanene or MoS2. The analysis of the evolution of the charge distribution with the size of the LH shows that, for small systems, it tends to distribute homogeneously between the two monolayers, whereas for larger systems electrons tend to accumulate in a region of ∼6 Šaround the interface. The work function of the heterostructure, one crucial parameter in the design of electronic nanodevices, is found to be lower than that of some conventional 2D LH. Remarkably, all the heterostructures studied show a very high Curie temperature (between 696 K and 1082 K), high magnetic moments and high magnetic anisotropy energies. These features make (Ti2C)/(Ta2C) lateral heterostructures very suitable candidates for spintronic, photocatalysis, and data storage applications based upon 2D magnetic materials.

Exploring a novel class of Janus MXenes by first principles calculations: structural, electronic and magnetic properties of Sc2CXT, X = O, F, OH; T = C, S, N.

The already intriguing electronic and optical properties of the MXene Sc2C family can be further tuned through a wide range of possible functionalizations. Here, by means of density functional theory, we show that the 36 possible elements of the Janus MXT (M: Sc2C, X: O, F, OH, T: C, N, S) family, built by considering the four possible structural models (i) FCC, (ii) HCP, (iii) FCC + HCP, and (iv) HCP + FCC, are all potentially stable. The analysis of their mechanical properties shows the excellent mechanical flexibility of functionalized MXenes (f-MXenes) under large strain, making them more suitable for applications where stress could be an issue. Interestingly, while Sc2C presents a metallic character, Sc2COS, Sc2CFN and Sc2COHN are found to be semiconductors with bandgaps of 2.5 eV (indirect), 1.67 eV (indirect) and 1.1 eV (direct), respectively, which presents promising applications for nano- and optoelectronics. Moreover, Sc2CFC presents a ferromagnetic ground state with the 2 × 2 × 1 supercell magnetic moment of 3.99 µB, while the ground state of Sc2COHC might be antiferromagnetic with a magnetic moment of 3.98 µB, depending on the environment. Remarkably, the band structures of Sc2CFC and Sc2COHC present a half-metallic character with an HSE06 fundamental band gap of 0.60 eV and 0.48 eV, respectively. Our results confirm the extraordinary potential of the Janus MXT (M: Sc2C, X: O, F, OH, T: C, N, S) family for novel applications in 2D nano-,opto- and spintronics.

Theoretical characterisation of point defects on a MoS2 monolayer by scanning tunnelling microscopy.

Different S and Mo vacancies as well as their corresponding antisite defects in a free-standing MoS2 monolayer are analysed by means of scanning tunnelling microscopy (STM) simulations. Our theoretical methodology, based on the Keldysh nonequilibrium Green function formalism within the density functional theory (DFT) approach, is applied to simulate STM images for different voltages and tip heights. Combining the geometrical and electronic effects, all features of the different STM images can be explained, providing a valuable guide for future experiments. Our results confirm previous reports on S atom imaging, but also reveal a strong dependence on the applied bias for vacancies and antisite defects that include extra S atoms. By contrast, when additional Mo atoms cover the S vacancies, the MoS2 gap vanishes and a bias-independent bright protrusion is obtained in the STM image. Finally, we show that the inclusion of these point defects promotes the emergence of reactive dangling bonds that may act as efficient adsorption sites for external adsorbates.

Tuning the conductance of single-walled carbon nanotubes by ion irradiation in the Anderson localization regime.

Carbon nanotubes are a good realization of one-dimensional crystals where basic science and potential nanodevice applications merge. Defects are known to modify the electrical resistance of carbon nanotubes; they can be present in as-grown carbon nanotubes, but controlling their density externally opens a path towards the tuning of the electronic characteristics of the nanotube. In this work, consecutive Ar+ irradiation doses are applied to single-walled nanotubes (SWNTs) producing a uniform density of defects. After each dose, the room-temperature resistance versus SWNT length (R(L)) along the nanotube is measured. Our data show an exponential dependence of R(L) indicating that the system is within the strong Anderson localization regime. Theoretical simulations demonstrate that mainly di-vacancies contribute to the resistance increase induced by irradiation, and that just a 0.03% of di-vacancies produces an increase of three orders of magnitude in the resistance of a SWNT of 400 nm length.

Cardiotoxic effects of nitrofurantoin and tertiary butylhydroperoxide in vitro: are oxygen radicals involved?

Langendorff rat hearts were perfused for 15, 30 or 75 min. with the oxygen radical generators nitrofurantoin (0.25 or 0.5 mmol/l) or tertiary butylhydroperoxide (0.25 mmol/l). Both agents reduced the force of contraction and increased the release of glutathione, oxidized glutathione, lactate dehydrogenase and creatine phosphokinase into the perfusion fluid. The tissue concentration of glutathione was reduced. While there were no signs of an increased production of conjugated dienes, the tissue concentration of malondialdehyde was greater than in control experiments. The variability of the latter effect was large, however, and in most cases the increase was not statistically significant. Addition of catalase (100 mU/ml) or catechin (0.5 mmol/l) to the perfusion medium abolished the nitrofurantoin induced release of oxidized glutathione but did not not prevent or attenuate enzyme leakage from the cells and the development of a negative inotropic effect. These results suggest that the cardiotoxic effects of nitrofurantoin and tertiary butylhydroperoxide cannot be explained by the appearance of oxygen radicals alone and that an increased lipid peroxidation is not the mechanism which is primarily responsible for cell death.

Processing of atriopeptin prohormone by nonmyocytic atrial cells.

Atriopeptin (AP) is synthesized and stored in the mammalian atria as a 126 amino acid prohormone (AP126). Upon secretion, the prohormone undergoes site specific proteolysis within the atria to yield the carboxyl terminal 28 amino acid hormone (AP28). The atrial cell responsible for AP126 bioactivation has not yet been determined. Primary neonatal rat atrial cell cultures were generated with and without depletion of nonmyocytic cells. The molecular form of AP detected in the conditioned media of mixed cultures was determined to be AP126. Addition of dexamethasone to these cultures resulted in the appearance of a peptide that co-migrated with AP28. In contrast, no AP126 processing was detected in the conditioned media of myocyte enriched cultures when grown in the presence of dexamethasone. Readdition of nonmyocytic atrial cells to myocyte enriched cultures successfully reconstituted the steroid induced AP126 processing. Incubation of recombinant AP126argarg with nonmyocytic atrial cell cultures resulted in the generation of AP28argarg. We conclude that a nonmyocytic atrial cell is responsible for AP126 processing in vitro.