ACS Materials Letters最新文献

Many transition-metal-based catalysts, including metal–organic frameworks (MOFs), usually undergo reconstruction to form catalytically active oxyhydroxide sites during the oxygen evolution reaction (OER). However, structural transformation of conventional bulk MOFs mostly occurs at the surface, while internal active centers are not utilized, limiting the improvement in electrocatalytic performance. Herein, we demonstrate that reducing the MOF dimension can accelerate the transformation to metal oxyhydroxides and boost the OER activity. An ultralong NiCo-MOF-74 nanowire (NiCo-MOF-74-NW) enriched with surface open metal sites is prepared by a “pre-assembly–crystallization” strategy. Structural characterization and in situ analysis reveal that the nanowire morphology facilitates reconstruction into active CoOOH species during electrocatalysis. NiCo-MOF-74-NW achieves a low overpotential of 292 mV at 100 mA cm^–2, along with enhanced intrinsic activity and favorable reaction kinetics compared to MOF microrods (NiCo-MOF-74-MR). This work provides insights for designing MOF-based electrocatalysts through the decrease of dimensions to promote surface reconstruction.

Metal–organic frameworks (MOFs) represent a well-defined class of materials capable of incorporating catalytically active sites for gas-phase catalysis. However, the reducing conditions of hydrogenation catalysis can lead to nanoparticle formation in MOFs, which can significantly diminish the catalytic activity of single-site metals and reduce the longevity of MOF-based hydrogen solutions. Here, we present a straightforward approach to accessing catalytically active single metal sites in a robust Ni-MFU-4l MOF for gas-phase hydrogenation without the formation of Ni nanoparticles. By carefully tuning the local node chemistry through postsynthetic exchange of the terminal ligand coordinated to the Ni(II) centers in the MOF, from −Cl to −OH or −HCOO, we can readily generate Ni–H active species. We further demonstrate, using in situ pair-distribution function analysis, that these Ni–H sites are the sole catalytically active sites in the terminal ligand-exchanged counterparts, whereas nanoparticles readily form in the parent Ni-MFU-4l-Cl under otherwise identical catalytic conditions.

Group IV color centers in diamond are promising single-photon emitters for quantum information processing and networking. Among them, the tin-vacancy (SnV) center stands out due to its long spin coherence times at cryogenic temperatures above 1 K. While SnV centers have been realized using various fabrication routes, their in situ formation via microwave plasma-enhanced chemical vapor deposition (MW PE CVD) remains relatively unexplored. In this study, SnV centers, identified by a zero-phonon line (ZPL) near 620 nm, were synthesized in nanocrystalline diamond and free-standing microcrystalline diamond using tin oxide (SnO₂) as a dopant source at substrate temperatures of 750°C and 850°C. Photoluminescence measurements reveal that lowering the substrate temperature enhances both the ZPL intensity and spatial uniformity of SnV centers. These results highlight substrate temperature as a key parameter for controlling SnV incorporation during MW PE CVD growth and provide insights into optimizing fabrication strategies for diamond-based quantum technologies.

High overpotential resulting from the slow reaction rate of the oxygen reduction reaction (ORR) at air electrodes limits the practical use of proton exchange membrane fuel cells (PEMFCs) and zinc–air batteries (ZABs). In this study, a simplified single-step synthesis of PdAg alloy nanoparticles loaded on reduced graphene oxide (PdAg-rGO) as a bifunctional catalyst for the ORR and the oxygen evolution reaction (OER) was designed. Electrochemical evaluations revealed that the PdAg-rGO electrocatalyst showed a good ORR E_onset potential in alkaline (0.87 V) and acidic media (0.74 V). For the OER, PdAg-rGO required a 290 mV overpotential to deliver 50 mA cm^–2 and a Tafel slope of 61 mV dec^–1. Notably, PdAg-rGO demonstrated long durability, maintaining stable performance over 120 h in ZAB and over 100 h in PEMFC tests. The findings highlight the practical potential of the PdAg alloy as a robust and versatile ORR catalyst for emerging technologies in energy systems.

The generation and manipulation of photoinduced transient currents, as well as characterization of the emission of resultant electromagnetic waves, are crucial for the design and coherent operation of advanced optoelectronic devices. An ultrafast optical pulse-driven transient photocurrent lasts for picosecond time scale bursts as a terahertz (THz) emission. The emitted radiation, permitted by the intrinsic structural properties of materials, is remarkably enriched with information on associated ultrafast transients and can potentially explore microscopic insights into fascinating nonlinear dynamical characteristics. This review aims to understand terahertz (THz) emission and the underlying ultrafast photophysics in contemporary matter systems. Since THz emission is the manifestation of photocurrents and induced dynamic polarization that sustain a picosecond time scale, it offers a noncontact and noninvasive platform for studying such ultrafast phenomena.

Postoperative recurrence and metastasis remain major causes of mortality in breast cancer due to residual tumor cells and complex metastatic processes. Here, we develop an NIR-responsive MXene-based scaffold that integrates antiplatelet therapy, chemotherapy, and photothermal therapy for postoperative intervention. The scaffold is fabricated by printing sodium alginate, gelatin methacryloyl, and MXene into CaCl₂ solution followed by UV cross-linking. Benefiting from the photothermal capacity of MXene nanosheets, the scaffold enables efficient photothermal conversion and NIR-triggered drug release. Incorporation of the platelet glycoprotein (GPVI) inhibitor evobrutinib disrupts platelet–tumor interactions, thereby suppressing epithelial–mesenchymal transition and tumor invasion. In vivo, the scaffold provides sustained doxorubicin release and photothermal ablation to inhibit residual tumor growth while reducing lung metastasis through GPVI blockade. Transcriptomic analysis further confirms that the scaffold impedes tumor progression by modulating platelet activation and angiogenesis. This multifunctional platform offers a promising strategy for preventing postoperative breast cancer recurrence and metastasis.

The advancement of wearable ion sensors necessitates ion-selective electrodes (ISEs) with high sensitivity and rapid response kinetics. This study introduces a porous conductive film based on a carbon nanocoil (CNC)/Ti₃C₂T_x composite for ISE design. The Ti₃C₂T_x nanoflakes, exhibiting metallically conductive behavior and abundant surface functional groups, form the film’s structural backbone, ensuring stability and superior electrical conductivity. Concurrently, the helical morphology of CNCs induces a porous architecture, significantly enhancing the ion transport efficiency and ion-to-electron transduction pathways. Consequently, the sensor demonstrates high sensitivity (62.3 mV/decade) and a fast response (0.08 s).

The development of stable, high-performance solid electrolytes is critical for advancing all-solid-state lithium batteries (ASSLBs). We report a series of triple-anion electrolytes, Li₂TaS_1–xO_xCl₅ (0 ≤ x ≤ 0.9), synthesized via a rapid 2-hour mechanochemical process. The optimal composition, Li₂TaS_0.4O_0.6Cl₅ (LTSOC), achieves a room-temperature ionic conductivity of ∼4.2 mS cm^–1, over 15 times that of Li₂TaSCl₅. XRD confirms its amorphous nature, while ^6/7Li NMR reveals one magnetically equivalent lithium environment due to fast ion-exchange dynamics. Raman spectroscopy shows extensive anion mixing within Ta-centered octahedra, where O^2– and S^2– occupy axial positions, linking Ta–O–S–Cl units, while Li⁺ primarily migrates along equatorial Cl^–-lined pathways. Nanoindentation reveals a reduced elastic modulus with oxygen incorporation. When employed with commercial NMC811, LTSOC delivers an initial capacity of 187 mAh g^–1 at 0.1C, with ∼81.8% retention after 100 cycles and Coulombic efficiency exceeding 99%. These results demonstrate the promise of amorphous, mixed-anion solid electrolytes for scalable, high-performance ASSLBs.

Electrocatalysis holds great promise in the field of sustainable energy conversion. Surface-curvature engineering has recently emerged as a powerful strategy to boost catalytic performance by tailoring the electronic structures, charge transport, and local microenvironments. Despite promising advancements, a deep mechanistic understanding of how surface curvature influences catalytic activity through electronic and spatial effects remains insufficient. This Review systematically elucidates the fundamental mechanisms arising from highly curved surfaces in diverse catalysts. We first clarify key concepts and characterization techniques for curved electrocatalysts. Subsequently, we analyze the unique reaction mechanisms of carbon- and metal-based curved catalysts across various reactions. Then, the surface curvature effect on the catalytic stability of electrocatalysts are discussed. Finally, we propose future challenges and opportunities for surface-curvature strategies. This review provides a comprehensive understanding of the impact of surface curvature on catalytic behavior and serves as a reference for proof-of-concept designs of highly active curved electrocatalysts.