材料科学最新文献

AlGaN/GaN based high-electron-mobility transistors utilize the excellent electronic and transport properties of Gallium Nitride and related compounds, making them highly sought after for high-power and high-frequency applications. However, threading dislocations that form during the GaN epitaxy growth on lattice mismatched Si substrates impact the device performance and reliability by causing an early breakdown and carrier trapping phenomena. For applications exceeding 1 kV, the growth of thick GaN stacks on 200 mm Si wafers introduces significant strain, compromising substrate integrity. This has triggered the development of engineered substrates for GaN epitaxy and the re-evaluation of the subsequent epitaxial growth. In this study, we have investigated the current transport properties of detrimental dislocations in AlGaN/GaN heterostructures grown on AlN engineered substrates (commonly referred to as QST®) and on conventional Si (111) substrates. This study has been achieved by developing a correlative nanoscale characterization methodology implementing conductive atomic force microscopy, cathodoluminescence microscopy, and electron channelling contrast imaging and revisiting dislocation-sensitive etching behaviour. This allowed us to observe vertical conduction paths manifesting themselves only in certain types of dislocations and to analyse the associated current transport mechanisms. Our modelling of the local current-voltage characterization on such dislocations, which are only 1% of the total dislocation density, directly associate them to the conduction mechanism via Poole-Frenkel emission in the reverse bias and variable range hopping in the forward bias.

Staphylococcus aureus remains a leading cause of skin and soft-tissue infections, and antibiotic resistance undermines treatment. Vaccination is a key strategy that has the potential to address antibiotic resistance. However, subunit vaccines require multiple doses and have a slower response. In this study, we engineered a nanoparticle vaccine that multivalently displays a fusion antigen (HI) composed of the non-hemolytic Hla_H35L variant and the N2 domain of IsdB on the self-assembling mi3 scaffold. We systematically characterized the physicochemical properties of HI-mi3 and evaluated its immunogenicity and protective efficacy. Moreover, its mechanisms underlying its protective effect were investigated in vitro and in vivo. Here, HI-mi3 assembled into monodisperse nanoparticles with high purity and thermal robustness. Two doses elicited rapid, high anti-HI IgG titers with a predominance of IgG1 over IgG2a/IgG2b. HI-mi3 significantly reduced the lesion area and bacterial burden. In addition, HI-mi3 enhanced antigen uptake, increased CD80/CD86 and MHC II expression on BMDCs, and elevated CD11c⁺CD80⁺/CD86⁺ cells in draining nodes. Thus, HI-mi3 is a stable, safe, and highly immunogenic nanoparticle vaccine that confers protection against SA skin infection after a short, two-dose regimen, supporting further development toward clinical translation.

Bismuth vanadate (BiVO₄, BVO) is a widely studied photoanode material for photoelectrochemical (PEC) water splitting due to its suitable band gap, which enables efficient visible light absorption. However, its practical performance is significantly limited by poor charge carrier separation and low mobility, resulting in high recombination rates and reduced photocatalytic efficiency. To overcome these challenges, we propose a novel doping strategy involving the substitution of V⁵⁺ sites with cations of varying oxidation states, specifically 4⁺, 5⁺, and 6⁺ to modulate the structural, electronic, and catalytic properties of BVO. Using density functional theory (DFT) calculations, we systematically investigate the impact of these dopants on the crystal structure, electronic band structure, charge transport behavior, and oxygen evolution reaction (OER) energetics. Among the doped systems, Ti⁴⁺-doped BVO (Ti-BVO) demonstrates superior OER performance, primarily due to a reduced hole effective mass and an improved charge carrier mobility of 0.3802 cm² V^-1 s^-1 for holes and 0.1527 cm² V^-1 s^-1 for electrons. Additionally, the increased diffusion lengths for holes (99.2 nm) and electrons (62.89 nm) contribute to more efficient charge separation and transport. The calculated overpotential for Ti-BVO is significantly reduced to 0.41 V, compared to 0.97 V for pristine BVO, indicating a substantial improvement in reaction kinetics. These findings provide valuable insights for designing BVO-based next-generation photoanode materials.

Designing coatings with a wide spectrum of functions such as self-healing, liquid repellency, anticorrosion, and a high level of mechanical robustness is crucial in engineering applications. However, simultaneously meeting two or more conflicting requirements remains a challenge. In this work, a holistic, skin-inspired tri-layer coating is proposed to resolve the conflicting requirements of self-healing, liquid repellency, and corrosion resistance in hydrophilic polymer materials. The rational design of multiple gradients in self-healing, wetting, and strength endows a sustained liquid repellency, corrosion resistance, and self-healing even under harsh environments, as well as strong adhesion with metal substrate. The skin-inspired tri-layer coating exhibits complete self-healing even in harsh aqueous environments, owing to the synergistic interaction between layers. The tri-layer structure consists of a hydrophobic epidermis-like barrier layer, a hydrophilic self-healing polymer middle layer, and a micro-arc oxidation porous base layer that provide strong interfacial adhesion and mechanical support. The hydrophilic polymer layer, composed of polyvinyl alcohol and tannic acid, rapidly repairs damaged coating regions through hydrogen bonding and diffusion, triggered by water molecules. Meanwhile, the hydrophobic outer layer acts as a sealing barrier, limiting excessive diffusion of the hydrophilic polymer. Such an integrated skin-inspired coating strategy provides new insights into design and manufacturing multifunctional polymeric coatings to tackle the critical challenges in a variety of engineering services.

Electrocatalytic carbon dioxide (CO₂) reduction reaction (CO₂RR) to valuable liquid fuels offers a promising solution for global warming. The challenges of low CO₂ delivery and poor product selectivity hinder the practical application of CO₂RR technology. This study proposes electrocatalytic CO₂-to-formic acid (HCOOH) conversion using a cypress-like carbonic anhydrase/antimony-decorated bismuth (CA/Sb-decorated Bi) biohybrid. The carbonic anhydrase (CA) as CO₂ shuttle can enrich CO₂ concentration on the electrode surface, accelerating the CO₂ hydration kinetics and reaction rate. Density functional theory (DFT) calculations indicate that the introduction of Sb can alter the adsorption energy of H* and HCOO*, which is beneficial for CO₂RR to form HCOOH. Besides, CA/Sb-decorated Bi biohybrid can suppress competitive hydrogen evolution reactions (HER). Consequently, the CA/Sb-decorated Bi biohybrid achieves the Faradaic efficiency of 93.41% and 100% selectivity for HCOOH at -1.3 V. This work demonstrates the application potential of enzyme modification and metal decorating in CO₂RR for the development of sustainable energy.

Magnetization switching plays a key role for high-density, ultrafast, non-volatile spin-based devices. Although domain modulation via interfacial or thickness effects has been studied, the impact of fabrication structures on switching remains underexplored. Here, we investigate geometric and boundary effects on magnetotransport in patterned SrRuO₃ (SRO) films made via advanced micro/nanoscale processing. Channel miniaturization to one micrometer hugely increases saturation field from 9 to 32.5 kOe. Edge magnetic anisotropy induces pronounced multi-step magnetization switching, validated by micromagnetic simulations. Non-volatile electrical modulation of magnetization is achieved in multiferroic films: 10 nm SRO exhibits a voltage-tunable high-field magnetoresistance (MR); 7.8 nm SRO shows a suppressed multi-step switching alongside a high-field modulation of MR; particularly, 2.6 nm SRO has a coercive field altered from 21.6 to 12.1 kOe by ±9 V. These results stem from ferroelectric polarization and antiferromagnetism. This switching process, regulated by geometry and external bias, enables advances in multistate memory and artificial synapses.

Wireless flow sensing technologies have attracted significant interest for enabling safe operation and performance optimization in gas-liquid two-phase flow systems. Nevertheless, the real-time quantitative monitoring of liquid flow rates without phase separation remains a considerable challenge. In this work, we present a wireless, self-powered, and real-time quantitative liquid flow measurement system utilizing a gas-liquid electricity generator (GLEG) based on the triboelectric effect. The GLEG features a dual-electrode configuration consisting of an external ring electrode and an internal porous electrode, which efficiently harvests mechanical energy from high-speed continuous gas-liquid mixed flow and converts it into usable electrical power. By integrating a sensor circuit board with a power regulation module, a microcontroller unit, and wireless transmission components, we demonstrate a fully self-sustained sensing system capable of real-time quantitative monitoring in gas-liquid mixed flow environments. Under continuous flow conditions with an air pressure of 0.6 MPa and flow speed of 30 m/s, the system achieves real-time measurement of liquid flow rates in the range of 0-90 mL/min with an accuracy of 95%. This triboelectric nanogenerator-based wireless sensing platform offers a promising approach for in situ parameter analysis and measurement in multiphase flow systems.