Ye Zhu

Semiconducting MoSe ₂ is susceptible to photon reabsorption, while metallic NbSe ₂ yields low optical damage thresholds, each limiting their nonlinear optical (NLO) performance. Combining these contrasting traits, this study demonstrates that equimolar heterometallic Mo _(1−x) Nb _x Se ₂ , undergoes structural reconfiguration that substantially enhances NLO responses, as revealed by second harmonic generation (SHG) and nonlinear optical absorption (NOA) measurements. Pronounced SHG is observed in odd‐layer samples across 840–1020 nm, with a 32.5% higher optical damage threshold than NbSe ₂ . Further, anomalous SHG persists in even layers, attributed to strain‐induced symmetry breaking and emergence of non‐zero Berry curvature under substantial alloying. This rare behavior distinguishes the alloy from its binaries and enables integration into piezoelectric, ferroelectric, and spin‐valley‐coupling platforms. Furthermore, straindriven bandstructure modifications also yield prominent saturable absorption (SA) at 1 µm, as demonstrated by the generation of ultrafast‐ultrashort laser pulses of 2.292 ps with repetition rate of 11.21 MHz in Yb‑doped fiber laser system and exceptional reverse‐SA (RSA) at 1.5 µm, exhibiting intrinsic “selftriggered” optical‐limiting (10.21% and 18.15% improvements over respective binaries), suitable for laserprotection devices. Overall, the study provides a systematic strategy to engineer and enhance NLO functionalities in binary 2D materials, facilitating the development of functional NLO photonics devices.

A central challenge for conjugated polymers is to achieve long-range order while remaining solution processable, which is essential for matching the electrical performance of their counterparts of crystalline inorganic semiconductors. In this work, we show that n-doped poly(benzodifurandione) (n-PBDF) can undergo polymerization-driven spontaneous assembly (PSA), in which chain growth, chemical doping, and structural ordering are intrinsically coupled, yielding long-range chain extension over hundreds of nanometers. We reveal that the spontaneously formed n-PBDF nanoribbons arise from a self-initiated, convergent growth mechanism driven by cooperative monomer-polymer interactions and stabilized by proton-coupled duplex chains and the polymer’s intrinsic polyelectrolyte character. With long-range extended chains in the nanoribbons, the aligned n-PBDF thin films demonstrate metallic-level conductivity (>10 ⁴ siemens per centimeter).

Dry reforming of methane (DRM) demands catalysts that simultaneously resist coking and sintering at high temperature. Here, we show that sodium aluminate (NaAlO2) acts as a highly effective interfacial modifier, creating a functional Ni−NaAlO2 metal−support contact that couples reaction-relevant CO2 retention with robust Ni stabilization. Temperature-programmed desorption reveals that NaAlO2 retains CO2-derived species up to 700 °C, driven by the strong basicity of its ionic Na−Al−O lattice, while structural analysis confirms strong interfacial metal−support coupling that preserves the size of metallic Ni. In situ spectroscopy reveals a bifunctional perimeter pathway under DRM conditions, where these CO2-derived oxygen-containing species hosted on NaAlO2 efficiently oxidize CHx intermediates generated on adjacent metallic Ni sites. These coupled interfacial functions enable stable, near-coke-free DRM operation with suppressed Ni sintering for 110 h on stream, drastically outperforming a reference Ni/Al2O3 catalyst that deactivates via severe sintering, coking, and reactor blockage within 24 h. Crucially, NaAlO2 dissolves in water and undergoes reversible hydration/dehydration, enabling uniform post-synthetic deposition onto pre-formed Ni catalysts via a simple aqueous impregnation−drying step. We demonstrate that this modular interface incorporation successfully upgrades both a commercial Ni reforming catalyst and a reference Ni/Al2O3 catalyst without rebuilding the parent catalyst structures, significantly improving their coke and sintering resistance. Overall, this work establishes NaAlO2 as a deployable interfacial modifier for coupled CO2 handling and metal stabilization in practical reforming applications.

Single-layer transition metal dichalcogenides (TMDs), such as WS2, offer promising catalytic performance and good electron mobility, making them attractive cocatalysts for photo- and electrocatalysis. However, their structural instability under reaction conditions often leads to formation of inactive bulk metal oxides and contamination of final products, limiting long-term performance and industrial applicability. Herein, we demonstrate that this instability can instead be harnessed as a constructive transformation pathway. Under mild aqueous conditions, exfoliated WS2 monolayers undergo spontaneous transformation at the interface with anatase TiO2, resulting in the formation of highly dispersed tungsten species anchored on the oxide surface and accompanied by the generation of abundant oxygen vacancies. Comprehensive structural, spectroscopic, and theoretical analyses reveal that strong interfacial interactions direct the oxidation pathway away from bulk oxide formation and toward stabilized, atomically dispersed active sites with modified local electronic structures. The resulting catalyst exhibits enhanced charge separation, improved conductivity, and markedly improved stability and performance under photocatalytic conditions. These serendipitous findings reframe TMD degradation as a beneficial process and establish a strategy for repurposing unstable metal sulfide monolayers into functional components of robust photocatalytic systems.

Achieving co-optimization of performance and bias stability is crucial for enabling broader applications of indium-gallium-zinc oxide (IGZO) transistors in next-generation electronics. In this work, back-gate IGZO transistors with different gate stacks are systematically characterized to elucidate the role of interfacial layers (ILs) between the IGZO channel and the HfO2 insulator in device performance and bias stability. The transistor with the HfO2/ZrO2 stack exhibits a near-zero threshold voltage of −0.02 V and a low subthreshold swing of 75.2 mV/dec, outperforming counterparts with HfO2 or Al2O3 ILs. Driven by the larger chemical potential gradient at the IGZO/HfO2 interface, the IGZO film deposited on the HfO2 stack contains the highest concentration of oxygen vacancies (OVs). A large fraction of induced OVs structurally relax into deep-level traps that pin the Fermi level (EF) and impede electron injection at source/drain (S/D) contacts. In contrast, the IGZO films on ZrO2 and Al2O3 ILs exhibit substantially lower OV concentration and thus weaker EF pinning, resulting in reduced S/D contact barriers. Bias stress stability measurements further highlight the critical importance of both robust gate stacks and stable IGZO/high-k interfaces. Ultimately, this gate stack engineering offers a feasible pathway to fabricate high-performance and reliable IGZO transistors for advanced applications.

The deterministic control of quantum phases via ultrafast light-matter interaction lies at the frontier of modern physics. While light can trigger hidden phases inaccessible through equilibrium pathways, these photo-induced metastable states are typically transient or highly volatile, limiting their practical utility. Here, we demonstrate a hybrid optical-thermal strategy that utilizes photo-induced topological defects as kinetic gateways to unlock a robust, hidden charge density wave (CDW) phase in the van der Waals antiferroelectric (AFE) In2Se3. Using complementary ultrafast electron diffraction and microscopy, we show that an initial optical quench induces a metastable state characterized by long-lived topological defects via the Kibble-Zurek mechanism; upon thermal cooling, these defects act as heterogeneous nucleation seeds, lowering the kinetic barrier for the system to evolve thermodynamically into a hidden CDW state. Remarkably, this phase transition is fully reversible: a single laser pulse resets the system to a defect-engineered intermediate phase, preserving the topological landscape for subsequent switching. Our results establish a paradigm for using photo-induced topological defects to imprint kinetic pathways, providing a blueprint for the discovery of hidden quantum landscapes and the development of high-speed, non-volatile memory technologies.

Topological phases, as characterized by their topological invariants, have been considered as distinct states from the raw phases and hold great promise as tiny yet robust information carriers for the era of artificial intelligence^1,2. However, these nontrivial states are typically found under non-equilibrium conditions, or stabilized by extrinsic electrical or mechanical boundary constraints^3-6, which limit their applications. Particularly in ferroelectrics, it usually entails a maximized depolarization field produced by interfacial bound charges to balance the large elastic and gradient energies as dipole whirling at the atomic scale^7-10. Despite substantial attempts, achieving highly ordered topological polar crystals in bulk ferroelectrics still remains a challenge^11-14. Here we show that a two-dimensional polar hedgehog lattice with a period down to 4 nm can crystallize spontaneously free from any external boundary constraints in a family of A-site layer-ordered perovskites. Using advanced scanning transmission electron microscopy, we observe the polar hedgehog vortices in real space and disclose the physical nature as the cooperative assembly of modulated in-phase and out-of-phase octahedral rotations, further underpinned by hybrid improper ferroelectricity. Theoretical calculations show that the exchange interaction of phonons describing the octahedral rotations is the primary driving force of this intriguing dipole topology. Our findings not only clarify the ambiguity in the structure and origin of the widespread superstructure in layer-ordered perovskites but also demonstrate a viable framework for designing nontrivial structures and functionalities beyond perovskites.

High-entropy alloy (HEA) nanomaterials are promising catalysts for proton exchange membrane water electrolysers (PEMWE), yet their crystalline structures have typically been restricted to thermodynamically stable phases. Here, using Au nanomaterials with distinct crystal phases as templates, we synthesize and stabilize Au@HEA core-shell nanostructures through a general and robust wet-chemical method in which the HEA is composed of up to ten metallic elements (Ir, Pt, Ni, Fe, Co, Rh, Pd, Ru, Cu and Mn). Phase-dependent water electrolysis is demonstrated as a proof-of-concept application. The hexagonal close-packed 4H-Au@4H-IrPtNiFeCo catalyst exhibits superior activity and stability for the acidic hydrogen evolution reaction, oxygen evolution reaction and overall water electrolysis compared with the conventional face-centred cubic IrPtNiFeCo catalyst. In a PEMWE at 60 °C, the 4H-Au@4H-IrPtNiFeCo catalyst achieves 3,000 mA cm^-2 at only 1.90 V and maintains stable operation for over 1,200 h at 1,000 and 2,000 mA cm^-2, with degradation rates of ~6.3 and ~15.7 µV h^-1, respectively. This work offers a strategy for designing highly efficient and stable HEA catalysts with tailored phases for future practical water electrolysis.