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<jats:title>Abstract</jats:title> <jats:p>Monolayer Fe$_2$C is expected to possess strong electronic correlations, which can significantly contribute to electronic and magnetic properties. In this study we consider electronic and magnetic properties of MXene Fe$_2$C within the DFT+DMFT approach.~We establish the existence of local magnetic moments $\mu_{\rm loc}=3.3\mu_B$ in this compound, characterized by sufficiently long lifetime of $\tau\sim 350$~fs. We also calculate exchange interaction parameters accounting for electronic correlations using the recently developed approach for paramagnetic phase. At low temperatures, we obtain the strongest exchange interaction $11$~meV between next nearest neighboring Fe atoms, located above (or below) the carbon plane, and the subleading interaction $6$~meV between the next to next nearest neighboring atoms, located across the carbon plane. The resulting dependence of the Berzinskii-Kosterlitz-Thouless (BKT) and Curie temperatures on magnetic anisotropy is obtained.The BKT temperature for the pristine Fe$_2$C is $T_{\rm BKT}\simeq 300$~K, which makes this compound a good candidate for the two-dimensional ferromagnet with XY anisotropy.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Liquid phase exfoliation (LPE) is the most promising method for the low-cost, scalable production of two-dimensional nanosheets from their bulk counterparts. &amp;#xD;Extensive exfoliation occurs in most solvents due to the huge amount of energy introduced by sonication or shear mixing. However, the subsequent dispersion is not always stable, with extensive reaggregation occurring in some solvents. &amp;#xD;Identifying the optimal solvent for a particular layered material is difficult and requires a fundamental understanding of the mechanism involved in maintaining a stable dispersion. &amp;#xD;Here, we use molecular dynamics calculations to show that when graphene is immersed in a solvent, distinct solvation layers are formed irrespective of the choice of solvent and their formation is energetically favourable for all considered solvents. &amp;#xD;However, energetic considerations such as these do not explain the experimental solvent-dependence of the dispersion concentration. &amp;#xD;Instead, we find that solvents with high diffusion coefficients parallel to the graphene layer result in the lowest experimental concentration of graphene in solution. &amp;#xD;This can be explained by the enhanced ease of reaggregation in these solvents. Solvents with smaller diffusion coefficients result in higher experimental graphene concentrations as reaggregation is prevented. In the low diffusion limit, however, this relationship breaks down. We suggest that here the concentration of graphene in solution depends primarily on the separation efficiency of the initial exfoliation step. Based on this, we predict that the concentration of exfoliated graphene in solvents such as benzaldehyde and quinoline, which have low diffusion constants, can be increased dramatically by careful tuning of the experimental sonication parameters. &amp;#xD;</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Nitric oxide plays an important role in cardiovascular function, immune response, and intercellular signaling. However, due to its short lifetime, real-time detection of nitric oxide is challenging. Herein, an electrochemical sensor based on fibronectin-modified, solution-processed graphene ink for nitric oxide detection is developed using a facile fabrication method involving spin-coating and hot-plate annealing. The sensor is first electrochemically characterized with a nitric oxide donor, spermine NONOate, exhibiting a dynamic range of 10 – 1000 μM. The fibronectin-functionalized graphene supports the attachment and growth of MDA-MB-231 breast cancer cells, as confirmed by optical microscopy. Extracellular nitric oxide production is stimulated using the amino acid L-arginine. Nitric oxide production results in morphological changes to the adhered cells, which are reversible upon the addition of the nitric oxide synthase antagonist Nω-nitro-L-arginine methyl ester (L-NAME). The production of nitric oxide is also confirmed using real-time amperometric measurements with the fibronectin-functionalized graphene sensors. While this work focuses on nitric oxide detection, this potentially scalable platform could be extended to other cell types with envisioned applications including the high-throughput evaluation of therapeutics and biocompatible coatings.&amp;#xD;</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Bilayer CrI<jats:sub>3</jats:sub> attracted much attention due to peculiar switching between the layered ferromagnetic and antiferromagnetic order upon stacking alternations. This discovery pointed out that the interlayer Cr-Cr exchange interaction, despite being much weaker than the intralayer exchange, plays an important role in shaping the magnetic properties of bilayer CrI<jats:sub>3</jats:sub>. In this work we delve into the anisotropic part of the interlayer exchange with the aim to separate the contributions from the Dzyaloshinskii-Moriya (DMI) and the Kitaev interactions (KI). We leverage the density functional theory calculations with spin Hamiltonian modeling and develop an energy mapping procedure to assess these anisotropic interactions with μeV accuracy. After inspecting the rhombohedral and monoclinic stacking sequences of bilayer CrI<jats:sub>3</jats:sub>, we reveal a considerable DMI and a weak interlayer KI between the sublattices of a monoclinic bilayer. We explain the dependence of DMI and KI on the interlayer distance, stacking sequence, and the spin-orbit coupling strength, and we suggest the dominant superexchange processes at play. In addition, we demonstrate that the single-ion anisotropy in bilayer CrI<jats:sub>3</jats:sub> is highly stacking-dependent, increasing by 50% from monoclinic to rhombohedral bilayer. Remarkably, our findings prove that iodines, owing to spatially extended 5p orbitals which feature strong spin-orbit coupling, are highly efficient in mediating the DMI across the van der Waals gap. Our study gives promise that the interlayer chiral control of spin textures, demonstrated in thin metallic films where the DMI is with a much longer range, can be achieved with similar efficiency in semiconducting two-dimensional van der Waals magnets.&amp;#xD;&amp;#xD;</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Here, we exfoliated high-quality turbostratic graphene with a clean interface at a high production rate (10 g/h) directly from graphite using an industrial-friendly technique i.e., plasma spraying, catching note of its growing global interest. The reduction of the (002) X-ray diffraction peak and the transparent scanning electron microscope (SEM) image are used to characterize the exfoliation. The thickness of exfoliated graphene layers is measured using an atomic force microscope (AFM). Turbostratic nature (twist) in graphene is identified based on the appearance of three Raman combination bands (TS1, TS2, and TS3) between 1800 cm-1 and 2300 cm-1. The twist between the layers is precisely measured using selected area electron diffraction (SAED), and the turbostratic nature is confirmed by observing a moiré pattern utilizing a high-resolution transmission electron microscope (HR-TEM). The produced turbostratic graphene exhibited large variability in twist angles (2⁰-30⁰) with a visible moiré pattern. The high crystalline quality and clean interface between single layers of graphene were confirmed by the moiré pattern and SAED. Later, we demonstrated the mechanism underlying the twist in our exfoliated graphene, which could open the way for the production of high-quality turbostratic graphene with clean interfaces.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>As is well known, how to deeply understand the charge separation and charge transfer capabilities of catalysts, as well as how to optimize these capabilities of catalysts to improve hydrogen production performance, remains a huge challenge. In recent years, a new type of carbon material graphdiyne (GDY) has been proposed. GDY acetylene has a special atomic arrangement that graphene does not have a two-dimensional network of sp<jats:sup>2</jats:sup> and sp conjugated intersections makes it easier to construct active sites and improve photocatalytic ability. In addition, GDY also has the advantage of adjusting the bandgap of other catalysts and inhibiting carrier recombination, making it more prone to hydrogen evolution reactions. In addition to using mechanical ball milling to produce GDY, NiWO<jats:sub>4</jats:sub> without precious metals was also prepared. The sheet-like structure of GDY in the composite catalyst provides a anchoring site and more active sites for the granular NiWO<jats:sub>4</jats:sub>. And the composite catalyst fully enhances the good conductivity of GDY and its unique ability to enhance electron transfer, greatly improving the ability of NiWO<jats:sub>4</jats:sub> as a single substance. Through <jats:italic>in-situ</jats:italic> x-ray photoelectron spectrometer, it was demonstrated that a p–n heterojunction was constructed between GDY and NiWO<jats:sub>4</jats:sub> in the composite catalyst, further enhancing the synergistic effect between the two, resulting in a hydrogen production rate of 90.92 <jats:italic>μ</jats:italic>mol for the composite catalyst is 4.56 times higher than that of GDY and 4.97 times higher than that of NiWO<jats:sub>4</jats:sub>, respectively, and the stability of the composite catalyst is significantly higher than that of each single catalyst.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The development of lateral heterostructures (LHs) based on two-dimensional (2D) materials with similar atomic structure but distinct electronic properties, such as transition metal dichalcogenides (TMDCs), opened a new route towards realisation of optoelectronic devices with unique characteristics. In contrast to van der Waals vertical heterostructures, the covalent bonding at the interface between subsystems in LHs is strong, such that the morphology of the interface, which can be coherent or contain dislocations, strongly affects the properties of the LH. We predict the atomic structure of the interface with account for the mismatch between the primitive cell sizes of the components, and more important, the widths of the joined materials using parameters derived from first-principles calculations. We apply this approach to a variety of TMDCs and set a theoretical limit on when the transition of the interface from coherent to dislocation-type should occur. We validate our theoretical results by comparison with the initial stage of two-dimensional heteropitaxial growth of junctions between MoS<jats:sub>2</jats:sub> and TaS<jats:sub>2</jats:sub> on Au(111).</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Layered material heterostructures (LMHs) can be used to fabricate electroluminescent devices operating in the visible spectral region. A major advantage of LMH-light emitting diodes (LEDs) is that electroluminescence (EL) emission can be tuned across that of different exciton complexes (e.g. biexcitons, trions, quintons) by controlling the charge density. However, these devices have an EL quantum&amp;#xD;efficiency as low as~10<jats:sup>−4</jats:sup>%. Here, we show that the superacid bis-(triuoromethane)sulfonimide (TFSI) treatment of monolayer WS<jats:sub>2</jats:sub>-LEDs boosts EL quantum efficiency by over one order of magnitude at room temperature. Non-treated devices emit light mainly from negatively charged excitons, while the emission in treated ones predominantly involves radiative recombination of neutral excitons. This paves the way to tunable and efficient LMH-LEDs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Graphene plasmons, including those in intercalated graphene, are an important research focus, with the promise of enabling light manipulation and providing a unique platform for gaining fundamental insights into many-body electronic interactions. In the present work, we discuss the results of low-energy plasmonic excitations in epitaxial quasi-free monolayer graphene formed by intercalation of Sn beneath the buffer layer on 4H-SiC(0001). &amp;#xD;The quantitative analysis of the sheet plasmon dispersion revealed that the Sn-induced ($1\times1$) interface is metallic and results in formation of charge-neutral graphene. A redshift of the 2D plasmon was found, but only after doping with potassium.&amp;#xD;The Sn-diluted interface, revealing a ($\sqrt{3}\times\sqrt{3}$) reconstruction and resulting in intrinsically n-type doped graphene, behaves comparably to the buffer layer for epitaxial monolayer graphene. &amp;#xD;Furthermore, it seems that a dipolar coupling of the longitudinal charge density fluctuations in graphene to the interface layer triggers the formation and the loss energy of a plasmonic multipole component, which therefore makes it suitable for studying proximity effects of excitations in electronically weakly coupled 2D heterosystems.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Two-dimensional (2D) van der Waals (vdW) magnets have recently emerged as novel skyrmion hosts. This discovery has opened a new material platform for tuning the properties of topological spin textures, such as by exploiting proximity effects induced by stacking of 2D materials into heterostructures, or by directly manipulating the structural composition of the host material. Previous works have considered the effect of varied composition in the bulk crystals of the vdW magnet Fe<jats:sub>3-x</jats:sub>GeTe<jats:sub>2</jats:sub>, but so far the effects on the hosted spin textures have not been thoroughly investigated. In this work, real-space x-ray microscopy is utilized to image magnetic stripe domain, skyrmion and composite skyrmion states in exfoliated flakes of Fe<jats:sub>3-x</jats:sub>GeTe<jats:sub>2</jats:sub> with varying Fe deficiency x. In combination with supporting mean-field and micromagnetic simulations, the significant alterations in the magnetic phase diagrams of the flakes, and thus the stability of the observed spin textures, are revealed. These arise as a result of the varying temperature dependence of the fundamental magnetic properties, which are greater than can be explained by the removal of spins, and are consistent with previously reported changes in the electronic band structure via the Fe deficiency.</jats:p>