Nano Letters最新文献

The quantum spin Hall effect in 1T′-phase MoTe₂ promises topological protection at >250 K, yet direct observation of its nonequilibrium dynamics has remained elusive, requiring nanoscale spatial and ultrafast temporal resolution. Here, we employ time-resolved photoemission electron microscopy to visualize the carrier dynamics in bilayer 1T′-MoTe₂ at room temperature. We identify a topological edge mode spatially confined below 200 nm, exhibiting photoemission intensity an order of magnitude stronger than the bulk. Strikingly, the edge state shows an ultralong lifetime exceeding 3.2 ps, in stark contrast to the sub-100 fs relaxation of bulk states, a dynamical dichotomy that is absent in the topologically trivial 2H phase. Supported by first-principles calculations, we ascribe this robustness to spin-selective suppression of backscattering and electron–hole recombination in the helical edge channel. Our findings provide direct evidence of low-dissipation edge transport in a 2D-compatible system, advancing its prospects for ultrafast topological electronics and spintronics.

We report a template-free and scalable method for the continuous production of mesoporous phenolic resin beads using a flow system. The synthesis can be monitored in situ using spectroscopic methods to capture the stepwise transition from soluble oligomers to insoluble polymer networks. With a combination of high porosity, abundant functional groups, and hydrophilic/hydrophobic surface features, the mesoporous beads interact favorably with a broad range of micropollutants. When incorporated with superparamagnetic nanoparticles and fluorescein isothiocyanate, the resultant beads exhibit magnetic separability and fluorescence traceability under ultraviolet light. The multifunctionality allows the beads to efficiently adsorb Pb²⁺, methylene blue, and rhodamine B for rapid removal from a suspension using a magnet, making them well-suited for portable water treatment. This approach is extendible to the scalable synthesis of other functional nanomaterials for environmental remediation.

Nucleation and growth of solid phases from species dissolved in an electrolyte govern battery performance, defining capacity, efficiency, rate capability, stability, and safety. However, classical nucleation–growth models often do not realistically describe working cells, failing to capture highly asymmetric out-of-plane growth and finite reactant supply. Here, we introduce a nucleation–growth model to fit potentiostatic nucleation transients that explicitly accounts for a finite amount of reactant and its depletion, reproducing the characteristic current rise upon nucleation, peak, and subsequent decay without ad hoc corrections. Both instantaneous nucleation and progressive nucleation are considered. The model is applied to the nucleation and growth of Li₂S at a catalyzed electrode from a lithium polysulfide solution, yielding nucleus densities of up to 6.7 × 10⁹ cm^–2 and an effective reaction rate constant of 1.8 × 10^–3 s^–1. Beyond Li–S batteries, the framework can be extended to other conversion and metal-deposition chemistries in which finite-supply effects dominate.

Wafer-scale fabrication of high-performance metal oxide semiconductor (MOS) gas sensors, with good reproductivity/uniformity, is essential for their batch deployments as either selective sensors or smart electronic noses, but it remains a big challenge. In this work, we propose a top-down approach for manufacturing O₃ sensors from commercial indium tin oxide (ITO) glasses, which mainly involves laser patterning (etching) and Ar/H₂ plasma treatment. Increased surface roughness induced by Ar/H₂ plasma treatment (60 min) and localized heating (180 °C) via self-heating enable an exceptional O₃ sensing performance, including a drastically improved O₃ response, good selectivity, weak humidity interference and long-term stability. The present ITO sensor enables real-time precise monitoring of ambient O₃ from background-level ∼25 to 200 ppb, verified by the UV photometric ozone analyzer. Moreover, wafer-scale fabrication of sensor arrays with uniform O₃ sensing performance has been demonstrated, raising the hope of smart O₃ sensors for ambient ppb-level O₃ monitoring.

High mechanical strength and high ionic conductivity are mutually exclusive in conventional hydrogels. Herein, we report a hydrogel that overcomes this trade-off by incorporating trace MXene into a PVA/ANF matrix via a salting-out strategy. MXene induces a coarse-grained porous structure, where thick pore walls enhance mechanics while enlarged pores facilitate ion transport. The resulting hydrogel achieves a tensile strength of 6.08 MPa, toughness of 9.59 MJ/m³, fracture strain of 250%, and ionic conductivity of 3.4 S/m. It also exhibits high strain sensitivity (GF = 3.26) within 0–120% strain. Attached to the human body, the hydrogel enables precise motion monitoring, demonstrating promise for wearable sensing. Our findings suggest a general structural engineering strategy to overcome the trade-off between ionic conductivity and mechanical properties in soft materials.

Unraveling nanoscale corrosion pathways is essential for understanding materials degradation mechanisms and designing corrosion-resistant metal alloys. Here, we directly visualize the corrosion of Pt–Ni nanododecahedra in 0.1 M HCl using liquid cell TEM. Each nanoparticle features a Ni-rich core and a Pt-rich frame. Our observation reveals that corrosion proceeds in two distinct stages: first the Ni-rich core dissolves without forming porosity, yielding small Pt nanocrystals and transient NiCl₂·6H₂O at the retreating interfaces; then the Pt-rich frame fragments into ∼5 nm Pt₃Ni nanocrystals that subsequently dissolve uniformly, accompanied by fleeting Pt chlorides. A percolation-based theory explains the observed behaviors: The core’s ∼8% Pt lies below the Pt connectivity threshold, preventing Pt scaffold formation, whereas the frame’s 48% Ni exceeds the Ni percolation threshold and collapses. Ordered Pt₃Ni suppresses Ni percolation, thereby enforcing uniform dissolution. These findings reveal how composition and structural ordering govern heterogeneous corrosion in Pt–Ni architectured nanoparticles.

Vanadium dioxide (VO₂) undergoes a rutile-to-monoclinic metal–insulator transition (MIT) at 340 K. Marked by abrupt resistivity changes of 10⁴–10⁵ Ω·cm, this property has long attracted interest for electronic applications. However, when VO₂ is a few nanometers thick, substrate-induced strain destabilizes the MIT, which limits device performance. To overcome this, two-dimensional (2D) VO₂ nanostructures grown with a remote distance from substrates can reveal intrinsic strain-free electrical behavior and enable high-performance MIT-based devices. We report the growth of few-nanometer-thick 2D VO₂ via remote van der Waals epitaxy. Transmission electron microscopy confirmed the monoclinic (M1) crystal structure. Conductive atomic force microscopy (c-AFM) measurements demonstrated a complete onset of 2D MIT at 1.5 V, achieving an on/off ratio of nearly 10⁴.

High-throughput, label-free monitoring of cellular differentiation remains a major challenge in stem cell biology and regenerative medicine. Raman spectroscopy offers rich molecular specificity without perturbing the cell state, but the analytical complexity of large, unlabeled spectral data sets has limited its adoption. Here, we introduce a scalable computational framework that adapts algorithms from single-cell genomics for the analysis of line-illumination Raman spectroscopy data. Applying this approach, we track the stepwise differentiation of human induced pluripotent stem cells into hepatocyte-like cells at single-cell resolution across more than 1.8 million spectra. By integration of unsupervised clustering with supervised learning, our pipeline enables rapid analysis (<2 min per imaging field), monitoring key biochemical markers, such as cytochromes, glycogen, and lipids, and real-time discrimination of successful and aberrant differentiation without labeling. This work establishes a generalizable strategy for Raman-based cell state profiling and supports non-invasive, in-line monitoring in stem cell manufacturing pipelines.