National Science Review最新文献

[This corrects the article DOI: 10.1093/nsr/nwaf246.].

Developing nano-iontronic devices that minimize ionic interference is essential for precise measurements in complex physiological systems. Graphdiyne (GDY), a novel carbon allotrope featuring sub-nanometer pores, enables effective regulation of ionic transport and is therefore a promising material for high-performance iontronic applications. Here, we report a pH-responsive nano-iontronic device fabricated by stacking and overlapping graphdiyne (so-GDY) layers onto the tip of the nanopipette. This so-GDY-based pH nano-iontronic sensor exhibits a linear decrease in ionic current under negative potential as the pH decreases from 8.00 to 5.50. This response is attributed to protonation of the oxygen-containing functional groups on the so-GDY surface and edges, which diminishes the negative surface charge and thereby reduces ionic conductivity. A key advantage of this nano-iontronic device is its excellent selectivity, demonstrating robust resistance to interference from divalent cations (Mg²⁺, Ca²⁺) and small molecules within the pH range of 8.00-5.50, while maintaining stable detection currents. The so-GDY-based pH nano-iontronic device transports monovalent cations up to 5 times more rapidly than divalent cations, alongside excellent repeatability, reversibility, and stability. This combination of features yields a biocompatible, high-resolution tool for minimally invasive, real-time pH measurements at the single-cell and even at a single-organelle level, opening new avenues for investigating cellular dynamics and disease pathogenesis with enhanced clarity.

While correlated phenomena of flat bands have been extensively studied in twisted systems, the ordered states that emerge from interactions in the intrinsic flat bands of kagome lattice materials remain largely unexplored. The newly discovered kagome metal CsCr₃Sb₅ offers a unique and rich platform for this research, as its multi-orbital flat bands at the Fermi surface result in a complex interplay of pressurized superconductivity, antiferromagnetism, a structural phase transition and density wave orders. Here, using ultrafast optical techniques, we provide strong spectroscopic evidence for a charge density wave transition in CsCr₃Sb₅, resolving previous ambiguities. Crucially, we identify rotational symmetry breaking that manifests as a three-state Potts-type nematicity. Our elastoresistance measurements directly demonstrate the electronic origin of this order, as the rotational-symmetry-breaking E _{2 g} component of the elastoresistance shows divergent behaviour around the transition temperature. This exotic nematicity results from the lifting of degeneracy of the multi-orbital flat bands, akin to phenomena seen in certain iron-based superconductors. Our study pioneers the investigation of ultrafast dynamics in flat-band systems at the Fermi surface, offering new insights into the interactions between multiple elementary excitations in strongly correlated systems.

The electrical structure of Earth's interior, resolved by using geophysical surveys, is key to understanding its composition, dynamics and relevant properties. Electrically anomalous zones in the upper mantle have been frequently observed, yet the origin remains debated. The geophysically imaged electrical anomalies cannot be properly interpreted if the constraints on the mantle materials from petrological and geochemical surveys and mineral physics experiments are not combined. Studying mantle samples has revealed widespread heterogeneities in their mineral constituents, elemental compositions and thermodynamic properties, in addition to the local occurrence of melts and fluids. The heterogeneities are macroscale, ranging on the levels of meters to kilometers. Four conductive candidates have been identified for the electrical anomalies by using laboratory experiments under mantle conditions, including olivine owing to its oxidized state (but not water), lithologies (such as pyroxenites, eclogites and phlogopite-bearing assemblages due to enriched Fe, water and/or F), partial melt and aqueous fluids. Such materials are able to cause electrical anomalies in a variety of settings that are geophysically detectable, if connected forms, rational fractions and/or suitable temperature and redox states are spatially maintained along certain direction(s). Hydrous minerals except phlogopite (within their stability fields) and non-silicate minerals such as graphite, sulfides and carbonates are usually hard to produce mantle electrical anomalies. Mantle macroscale heterogeneities cause heterogeneous electrical structures. Geophysically imaged electrical anomalies in the upper mantle are intimately related to its petrological and geochemical evolution.

Twisted bilayer MoTe₂ (tMoTe₂) has recently emerged as an exceptional platform for realizing strongly correlated and topological quantum phases. Yet, its microscopic electronic structure remains largely unexplored. Here, we use scanning tunneling microscopy/spectroscopy (STM/STS) to directly image the moiré flat bands in dual-gated tMoTe₂ devices with twist angles of 2.3°-3.8°. A dual-gate design allows independent tuning of band filling and displacement field, enabling detailed spectroscopic mapping. We find that the low-energy flat bands are localized at MX and XM sites and form a topological honeycomb lattice at zero electric field. An applied electric field lifts the degeneracy of the layer, driving a transition to two decoupled triangular lattices with trivial topology. Our results match first-principles calculations, revealing K-valley hybridization as the microscopic origin. At large moiré potential, we observe Wigner molecular crystals forming a Kagome lattice at filling ν _MX = 3, demonstrating electric-field control of topology and correlation in tMoTe₂.

Atomically thin 2D membranes with minimum ion transport pathways and low ion transport resistance are ideally suited for constructing ion-selective membranes for electric power generation, and have attracted considerable recent interest. However, the practical applications of such 2D membranes for electric power generation have been severely limited due to the lack of nanoporous 2D membranes with narrow distributed nanopore arrays and sufficient charge density. Here, we report a centimeter-scale ultrathin graphene nanomesh (GNM) membrane with narrow pore size distribution (∼1.5 nm) and rich in carboxylic groups (GNM-COO^-) for efficient osmotic power generation. The high-density nanometer pores anchored by negatively charged carboxylic groups allow efficient transport of K⁺ while selectively blocking Cl^-. We show that the GNM-COO^- membrane with asymmetric charge structure exhibits a diode-like ionic rectification property and facilitates directional ion transport. When employed as an ion-selective membrane for osmotic power generation, the designed GNM-COO^- membrane delivers an exceptionally large output power density (175.1 W m^{- 2}) at a 50-fold salinity gradient, and retains stable power generation performance for 2 months. This work provides a strategy to develop high-performance ion-selective membranes for the sustainable harnessing of blue clean energy.

Nanofluidic devices have been widely utilized to simulate electronic functionalities recently, due to their unique ion transport behaviors, such as non-linear ion transport, selectivity etc. However, the correlation between the ion transport behavior and the transitions among various nanofluidic capacitive and inductive hysteresis still remains poorly understood, which impedes the development of nanofluidic systems. Here, we report a concentration-dependent transition between capacitive and inductive hysteresis in gold-nanoparticle-stacked nanochannels. Quantitative analysis reveals that this transition is governed by the interionic distance relative to the Bjerrum length, establishing a universal mechanism for ion transport modulation. Notably, our system enables unidirectional plasticity (both facilitation and depression) by simply altering the ionic species, demonstrating programmable plasticity without structural reconfiguration. Additionally, a high-pass filter (HPF) circuit with tunable cut-off frequency is implemented through two identical nanofluidic devices. These findings establish a new paradigm for multifunctional nanofluidic devices and provide a rational foundation for the design of aqueous-phase neuromorphic computing circuits.