Materials Science and Engineering: R: Reports最新文献

The limited activity and stability of conventional anodes in seawater have posed a significant obstacle to sustainable green hydrogen production directly from seawater via electrolysis. To address these challenges, we engineered Ti₃C₂Tx-MXene by incorporating iron and boron into its matrix (tagged FBT) for selective oxygen evolution reaction (OER). Positioning B underneath the top layer induces charge disparity on the Fe-sites, which influences the subsequent growth of the ZIF-67 metal-organic framework (MOF) on the MXene surface through Fe-O-Co ionic bonds. DFT calculations reveal a favorable binding energy of −2.30 eV at the heterointerface for ZIF-67 adsorption to the surface of FBT via O-Co bond, a shortened bond length of 1.94 Å, confirming the formation of ionic bonds. These ionic bonds tune the active sites for an enhanced and selective OER over chlorine evolution reaction (CER), preventing active Fe species' leaching and ensuring stability at >1.56 A cm⁻² in 6 M alkaline seawater over 370 hours. Further, FBT and ZIF-67/FBT require low overpotentials of 521.2 and 508 mV, respectively, to deliver 1 A cm⁻² in 6 M alkaline seawater. Our findings demonstrate a robust strategy to significantly expand the potential of MXenes from simple conductive substrates to efficient OER catalysts for seawater splitting and beyond.

High-entropy alloys (HEAs) stand out from multi-component alloys due to their attractive microstructures and mechanical properties. In this investigation, molecular dynamics (MD) simulation and machine learning (ML) were used to ascertain the deformation mechanism of AlCoCrCuFeNi HEAs under the influence of temperature, strain rate, and grain sizes. First, the MD simulation shows that the yield stress decreases significantly as the strain and temperature increase. In other cases, changes in strain rate and grain size have less effect on mechanical properties than changes in strain and temperature. The alloys exhibited superplastic behavior under all test conditions. The deformity mechanism discloses that strain and temperature are the main sources of beginning strain, and the shear bands move along the uniaxial tensile axis inside the workpiece. Furthermore, the fast phase shift of inclusion under mild strain indicates the relative instability of the inclusion phase of hexagonal close-packed (HCP). Ultimately, the dislocation evolution mechanism shows that the dislocations are transported to free surfaces under increased strain when they nucleate around the grain boundary. Surprisingly, the ML prediction results also confirm the same characteristics as those confirmed from the MD simulation. Hence, the combination of MD and ML reinforces the confidence in the findings of mechanical characteristics of HEA. Consequently, this combination fills the gaps between MD and ML, which can significantly save time, human power, and cost to conduct real experiments for testing HEA deformation in practice.

Evaporating metallic films on two-dimensional (2D) materials is a necessary process to build electronic devices, but it produces bond breaking and metal penetration in the 2D material, which degrades its properties and the figures-of-merit of the devices. Evaporating the metal in ultra-high vacuum (10⁻⁹ Torr) is a recognized method to reduce the damage, but the higher complexity and cost of the setup and its lower throughput makes developing other solutions highly desirable. All studies on ultra-high vacuum evaporation of metals on 2D materials evaluated the figures-of-merit of transistors fabricated following different protocols, with very scarce or without sub-nanometre information. Moreover, such studies employed 2D materials produced by chemical vapour deposition (CVD), which contain relatively large amounts of native defects, and hence, post-evaporation analyses do not allow identifying which defects are native and which ones are generated during metal evaporation. In this article we analyse the structure of defect-free mechanically exfoliated 2D materials via cross-sectional transmission electron microscopy (TEM) before and after Au evaporation (on top), and calculate the density of defects introduced. We find that evaporating the metal in a moderate vacuum atmosphere of 5 × 10⁻⁶ Torr is sufficient to avoid damage, leading to a nearly perfect van der Waals interface. By using density functional theory simulations we find that the presence of water molecules on the surface of the 2D material slightly distorts the position of the atoms in the crystalline hexagonal network, weakening the covalent bonds and reducing the energy for defect formation. We fabricate Au/h-BN/Au devices and observe that evaporating the Au at 5 × 10⁻⁶ Torr produces much less out-of-plane leakage current than evaporating at 3 × 10⁻⁵ Torr. The approaches here presented are easy to use and facilitate the introduction of 2D materials in electronic devices and circuits.

Hydrogen has emerged as a clean and renewable energy source with the potential to mitigate global energy and environmental crises. Electrolytic water splitting, a highly efficient and sustainable technology, has garnered significant attention for hydrogen production. However, the slow kinetics of the oxygen evolution reaction on the anode and the high energy consumption limit the practicality of industrial-scale electrocatalytic water splitting. To address the challenge, the development of advanced electrolytic systems and the exploration of alternative oxidation reactions are crucial. This review highlights the recent advancements in coupled electrocatalytic hydrogen production strategies, including urea and hydrazine oxidation, value-adding electrosynthesis using small molecules, and waste upcycling and degradation. Various catalysts, the pertinent catalytic mechanisms for anodic oxidation reactions, and methods to decrease the energy barriers are discussed. Furthermore, the potential challenges and prospects for energy-saving electrolysis and promotion of hydrogen production are examined. A comprehensive understanding of these strategies and their implications is important to the development of efficient and sustainable hydrogen production.

The ternary and additive strategy, introducing a third component into a binary blend and add suitable additives, opens a simple and promising avenue to improve the power conversion efficiency (PCE) of organic solar cells (OSCs). This study investigates the optimization of OSCs by introducing volatile additives and a third component, L8-BO-X, which tunes the active layer morphology and improves the performance of the devices. Utilizing various characterization techniques, such as the grazing-incidence wide-angle X-ray scattering (GIWAXS), film-depth-dependent light absorption spectroscopy (FLAS), and the femtosecond-resolved transient absorption (fsTA) spectroscopy, the effects of these adjustment on crystallinity, phase separation, exciton generation, and charge transport in photovoltaic device are explored. The incorporation of the third component and volatile additives results in less anisotropy in molecular orientation and thus faster exciton splitting at the D-A interface, enhanced π-π stacking coherence length and longer exciton lifetime, and eventually an enhanced power conversion efficiency (PCE) of 19.6 % (certified as 19.07 % in the National Institute of Metrology in China) and exceptional photostability, with the devices retaining 82 % efficiency after 1200 hours of continuous light exposure.

Resistive switching (RS) devices, often referred to as memristors, have exhibited interesting electronic performance that could be useful to enhance the capabilities of multiple types of integrated circuits that we use in our daily lives. However, RS devices still do not fulfil the reliability requirements of most commercial applications, mainly because the switching and failure mechanisms are still not fully understood. Density functional theory (DFT) and/or molecular dynamics (MD) are simulations used to describe complex interactions between groups of atoms, and they can be employed to clarify which physical, chemical, thermal and/or electronic phenomena take place during the normal operation of RS devices, which should help to enhance their performance and reliability. In this article, we review which studies have employed DFT and/or MD in the field of RS research, focusing on which methods have been employed and which material properties have been calculated. The goal of this article is not to delve into deep mathematical and computational issues – although some fundamental knowledge is presented – but to describe which type of simulations have been carried out and why they are useful in the field of RS research. This article helps to bridge the gap between the vast group of experimentalists working in the field of RS and computational scientists developing DFT and/or MD simulations.

Triterpenoids are natural bioactive compounds that demonstrate cytotoxic and chemopreventive activities by inhibiting various intracellular signals and transcription factors. Despite their efficacy, triterpenoid chemotherapeutics face significant challenges in cancer therapy because of their poor aqueous solubility, which restricts the utilization of potent drug variants. Consequently, there is a pressing need to develop a solubilized form of triterpenoid encapsulated within mechanically robust biomaterials, to facilitate injectable and minimally invasive delivery. In this study, we focused on ginsenoside compound K (CK), a natural pentacyclic triterpenoid. It was conjugated to hyaluronic acid (HA-CK) and employed as a novel guest molecule for binding to β-cyclodextrin-grafted hyaluronic acid (HA-βCD), which is the host polymer. This interaction resulted in the creation of an injectable supramolecular hydrogel (HG-Gel) through a straightforward mixing process involving host–guest interactions between βCD and CK. The physical properties of the hydrogels were easily manipulated by altering the molecular weight of HA and the grafting degree of βCD and CK in HA. Notably, the supramolecular hydrogel precursors exhibited excellent cell viability for normal cells, sparing over 80 % of NIH 3T3 and HaCaT cells. Intriguingly, these hydrogels facilitated effective delivery to CD44-overexpressing cancer cells, suppressing cell proliferation. Enhanced trafficking of CK to cancer cells heightened caspase-dependent apoptosis in B16F10 cells, with the extent of cell death contingent on the expression levels of CD44 in cancer cells. This effect of CK seems to be mediated through the induction of intracellular reactive oxygen species (ROS) and mitochondrial membrane potential loss. In melanoma tumor-bearing mouse models, HG-Gels effectively inhibited tumor growth. Importantly, no side effects were observed on normal tissues, underscoring the safety of naturally derived biomaterials. This study underscores the superiority of HG-Gels as a platform for utilizing triterpenoid saponins in melanoma therapy, suggesting their potential for enhancing the safety and efficacy of triterpenoids in cancer treatment.

Ultrafast UV photodetectors (UV PDs) are crucial components in modern optoelectronics because conventional detectors have reached a bottleneck with low integration, functionalities, and efficiency. Core-shell metal oxide nanobrushes (MOx NBs)-based UV PDs have enhanced the absorption, tunable performance, and good compatibility for diversified applications, including imaging, self-powered systems, remote communications, security, and wearable electronics. Core-shell PDs are developed with complex hierarchical or heterostructured configurations that encapsulate 1D MOx nanowires on 1D nanostructures (NSs) to transport high charge carrier mobility or efficiency by reducing scattering and recombination rates. This review presents a thorough development of MOx core-shell microstructure for the enhancement of detection response and stability with controlled parameters for multifunctional applications. Significant roles of MOx NBs-based UV PDs exploring various growth techniques and complex photodetection mechanisms with their challenges, limitations, and prospects, providing valuable insights for propelling the progression of photodetector technology in this comprehensive review are discussed meticulously. The novelty of MOx NBs-based UV PDs lies in their distinctive brush-like morphology aspect, tunable properties, and improved performance compared to other NSs, for rapid and sensitive response ( ̴µs-ms) under UV light illumination. The diverse photoresponse parameters and multifunctional applications of UV PDs incorporating MOx NBs are carefully summarized, which will set the roadmap for future photodetector technology.

Maintaining battery stability is the greatest concern for the next generation of electronic devices, such as automotive and foldable electronics. Advanced lithium batteries experience mechanical fracturing during cycling due to structural changes, reducing their lifespan. Self-healing properties can effectively mitigate this issue, thereby increasing the device's durability. Utilizing intrinsic self-healing polymers (SHPs) is a prevalent strategy, addressing mechanical defects and enhancing electrochemical properties independently. This review begins with a discussion of the SHPs and their various mechanisms of self-healing capability, followed by a presentation of approaches and their strategies for competing with Silicon-based, Li-Metal, and Li-Sulfur batteries. SHPs or binders have a high potential to deal with the critical problems of cracks and volume change problems. Also, it discussed promising methods for employing self-healing materials to combat integrity and stability obstacles. It provided an overview of boosting Li-adsorbing systems, de-lithiation behavior, extending cycle life, and high retention capacity based on the coverage and interlayer binding role, increasing diffusion, and enhancing cycle life. This work would encourage researchers to concentrate substantially on developing self-healing properties for designing high-energy and durable lithium batteries.

Electrically conductive coordination frameworks (ECCF) firmly anchored on renewable and sustainable alginate substrates are fundamentally important yet still challenging for flexible electronics. Herein, we report an interfacial self-assembly strategy to prepare alginate-anchored ECCF for constructing flexible and ultrastable light-gas dual sensors. By combining free Cu ions with trispectral linker, well-defined ECCF with a metal catechol structure (Cu-CAT) is directly grown on alginate fabrics (AF), which perfectly solves swelling problem of the hydrated alginate and improves flexibility and toughness of the electronic platform. By precisely tuning the thickness of as-prepared Cu-CAT nanowire film, the resultant AF/Cu-CAT sensor acts as not only a stable and self-powered light sensor in wide spectral range but also a selective NH₃ sensor operating at room temperature. Remarkably, the flexible sensor demonstrates light-gas synergistic effect, facilitating the adsorption-desorption kinetic by 358 % and thus achieving ultrafast and ultrastable response. This work provides a feasible approach for manufacturing ECCF-functionalized flexible organo-substrates and pushes forward a significant step toward the electric-field modulation of flexible sensors.