材料科学最新文献

Tunable Mid-Infrared Graphene–Metal Metasurfaces

This cover illustrates the incorporation of a thin Al₂O₃ barrier layer for resolving current limitations of electrically tunable graphene–metal hybrid metasurfaces (article 2303085 by Fei Han, Xuezhi Zheng, Ewald Janssens, and co-workers). The authors' device improves the electronic doping ability of graphene, thereby enhancing the tuning range of mid-infrared metasurfaces. The straightforward approach is not only promising for future compact tunable optical devices, but it also provides guidelines for engineering future 2D material-based optoelectronics.

Leptospirosis is a global public health problem caused by Gram-negative pathogenic bacteria belonging to the genus Leptospira. The disease is transmitted through the urine of infected animals, which contaminates water and soil, leading to the infection of other animals and humans. Currently, several approaches exist to detect these bacteria; however, a new sensitive method for the live-cell imaging of Leptospira is required. In this study, we report the green synthesis of cadmium telluride quantum dots (CdTe QDs) which are unique fluorescent nanocrystals with a high fluorescence quantum yield capable of modifying cell surfaces and are biocompatible with cells. The fabrication of QDs with concanavalin A (ConA), a carbohydrate-binding lectin and known biological probe for Gram-negative bacteria, produced ConA-QDs which can effectively bind on Leptospira and exhibit strong fluorescence under simple fluorescence microscopy, allowing the live-cell imaging of the bacteria. Overall, we performed the simple synthesis of ConA-QDs and demonstrated their potential use as versatile fluorescent probes for the live-cell imaging of Leptospira. This technique could be further applied to track leptospiral cells and study the infection mechanism, contributing to a more thorough understanding of leptospirosis and how to control it in the future.

Stabilization of multiple polarization states at the atomic scale is pivotal for realizing high-density memory devices beyond prevailing bistable ferroelectric architectures. Here, we show that two-dimensional ferroelectric SnS or GeSe is able to revive and stabilize the ferroelectric order of three-dimensional ferroelectric BaTiO₃, even when the latter is thinned to one unit cell in thickness. The underlying mechanism for overcoming the conventional detrimental critical thickness effect is attributed to facile interfacial inversion symmetry breaking by robust in-plane polarization of SnS or GeSe. Furthermore, when invoking interlayer sliding, we can stabilize multiple polarization states and achieve efficient interstate switching in the heterostructures, accompanied by dynamical ferroelectric skyrmionic excitations. When invoking sliding and twisting, the moiré domains exhibit nontrivial polar vortexes, which can be laterally displaced via different sliding schemes. These findings provide an intuitive avenue for simultaneously overcoming the standing critical thickness issue in bulk ferroelectrics and weak polarization issue in sliding ferroelectricity.

In this work, three dimensional (3D) self-supported Ni-FeOH@Ni-FeP needle arrays with core-shell heterojunction structure are fabricated via in situ hydroxide growth over Ni-FeP surface. The as-prepared electrodes show an outstanding oxygen evolution reaction (OER) performance, only requiring the low overpotential of 232 mV to reach 200 mA cm^-2 with the Tafel slop of 40 mV dec^-1. For overall water splitting, an alkaline electrolyzer with these electrodes only requires a cell voltage of 2.14 V to reach 1 A cm^-2. Mechanistic investigations for such excellent electrocatalytic performances are utilized by in situ Raman spectroscopy in conjunction with density functional theory (DFT) calculations. The computation results present that Ni-FeOH@Ni-FeP attains better intrinsic conductivity and the D-band center (close to that of the ideal catalyst), thus giving superior excellent catalytic performances. Likewise, the surface Ni-FeOH layer can improve the structural stability of Ni-FeP cores and attenuate the eventual formation of irreversible FeOOH products. More importantly, the appearance of FeOOH intermediates can effectively decrease the energy barrier of NiOOH intermediates, and then rapidly accelerate the sluggish reaction dynamics, as well as further enhance the electrocatalytic activities, reversibility and cycling stability.

Tailoring the defects in graphene and its related carbon allotropes has great potential to exploit their enhanced electrochemical properties for energy applications, environmental remediation, and sensing. Vertical graphene, also known as carbon nanowalls (CNWs), exhibits a large surface area, enhanced charge transfer capability, and high defect density, making it suitable for a wide range of emerging applications. However, precise control and tuning of the defect size, position, and density remain challenging; moreover, due to their characteristic labyrinthine morphology, conventional characterization techniques and widely accepted quality indicators fail or need to be reformulated. This study primarily focuses on examining the impact of boron heterodoping and argon plasma treatment on CNW structures, uncovering complex interplays between specific defect-induced three-dimensional nanostructures and electrochemical performance. Moreover, the study introduces the use of defect-rich CNWs as a label-free electrode for directly oxidizing glyphosate (GLY), a common herbicide, and its metabolites (sarcosine and aminomethylphosphonic acid) for the first time. Crucially, we discovered that the presence of specific boron bonds (BC and BN), coupled with the absence of Lewis-base functional groups such as pyridinic-N, is essential for the oxidation of these analytes. Notably, the D+D* second-order combinational Raman modes at ≈2570 cm^-1 emerged as a reliable indicator of the analytes' affinity. Contrary to expectations, the electrochemically active surface area and the presence of oxygen-containing functional groups played a secondary role. Argon-plasma post-treatment was found to adversely affect both the morphology and surface chemistry of CNWs, leading to an increase in sp³-hybridized carbon, the introduction of oxygen, and alterations in the types of nitrogen functional groups. Simulations support that certain defects are functional for GLY rather than AMPA. Sarcosine oxidation is the least affected by defect type.

Although tendon predominantly experiences longitudinal tensile forces, transverse forces due to impingement from bone are implicated in both physiological and pathophysiological processes. However, prior studies have not characterized the micromechanical strain environment in the context of tendon impingement. To address this knowledge gap, mouse hindlimb explants are imaged on a multiphoton microscope, and image stacks of the same population of tendon cells are obtained in the Achilles tendon before and after dorsiflexion-induced impingement by the heel bone. Based on the acquired images, multiaxial strains are measured at the extracellular matrix (ECM), pericellular matrix (PCM), and cell scales. Impingement generated substantial transverse compression at the matrix-scale, which led to longitudinal stretching of cells, increased cell aspect ratio, and enormous volumetric compression of the PCM. These experimental results are corroborated by a finite element model, which further demonstrated that impingement produces high cell surface stresses and strains that greatly exceed those brought about by longitudinal tension. Moreover, in both experiments and simulations, impingement-generated microscale stresses and strains are highly dependent on initial cell-cell gap spacing. Identifying factors that influence the microscale strain environment generated by impingement could contribute to a more mechanistic understanding of impingement-induced tendinopathies.

In this article, a novel strategy is presented to selectively separate a mixture of equally sized microparticles but differences in material composition and surface properties. The principle relies on a photosensitive surfactant, which makes particles under light illumination phoretically active. The latter hovers microparticles from a planar interface and together with a superimposed fluid flow, particles experience a drift motion characteristic to its interfacial properties. The drift motion is investigated as a function of applied wavelength, demonstrating that particles composed of different material show a unique spectrally resolved light-induced motion profile. Differences in those motion profile allow a selective fractioning of a desired particle from a complex particle mixture made out of more than two equally sized different particle types. Besides that, the influence of applied wavelength is systematically studied, and discussed the origin of the spectrally resolved chemical activity of microparticles from measured photo-isomerization rates.

In this work, a highly accurate neural network potential (NNP) is presented, named Pt_NNP, and the exploration of the reconstruction of the Pt(001) surface and its vicinal surfaces with it. Contrary to the most accepted understanding of the Pt(001) surface reconstruction, the study reveals that the main driving force behind Pt(001) quasi-hexagonal reconstruction is not the surface stress relaxation but the increased coordination number of the surface atoms resulting in stronger intralayer binding in the reconstructed surface layer. In agreement with experimental observations, the optimized supercell size of the reconstructed Pt(001) surface contains (5 × 20) unit cells. Surprisingly, the reconstruction of the vicinal Pt(001) surfaces leads to a smooth shell-like surface layer covering the whole surface and diminishing sharp step edges.