ACS Materials Letters最新文献

All-solid-state potassium batteries have attracted considerable attention as energy storage devices. The development of suitable ionic conductors has received significant attention for the commercialization of the batteries. Here, we report the potassium-ion conductors KTaCl₆ prepared using the mechanochemical method and then heat treatment. The mechanochemically prepared sample comprises the monoclinic crystalline phase embedded within the amorphous component, as revealed by X-ray diffraction and transmission electron microscopy. The mechanochemically prepared sample exhibits an ionic conductivity of 1.8 × 10⁻⁵ S cm⁻¹ at 30 °C. Upon heat treatment, the sample undergoes crystallization, leading to a decrease in ionic conductivity. It is suggested that the amorphous phase plays a key role in the ion conduction of the KTaCl₆ chlorides.

Perylenediimides (PDIs), which feature strong visible-light absorption, π-electron-deficient planes, and photochemical characteristics, offer a versatile platform for developing tunable and efficient metal−organic framework (MOF) materials through modulation of their bay-substituent groups. Herein, we report ‌two structurally modified MOFs, MOF-Cl₄ and MOF-Br₂, whose PDI components feature different halogen substitution patterns in their bay regions, imparting differential halogen-controlled photochromism. Notably, MOF-Cl₄ exhibited high photosensitivity, whereas MOF-Br₂ was found to be almost photochemically inert. Furthermore, both MOFs could be readily photoexcited to generate their respective excited states or radical anions. Interestingly, experimental and theoretical calculations revealed that these excited states or radical anions demonstrated halogen-controlled photocatalytic activities in the oxysulfonylation of alkynes and the aerobic oxidation of enamines. The photocatalytic performance of MOF-Cl₄ proved superior to that of MOF-Br₂, a difference primarily attributed to the divergent SOMO-1 and optical bandgap of the PDI ligands and MOF materials, induced by the halogen substitution patterns.

Photocatalytic overall water splitting is promising for sustainable H₂ supply but is hindered by severe charge recombination and the reverse reaction. Herein, we design a novel organic/inorganic heterojunction by coupling π-conjugated perylene diimide polymer (PDIP) with aluminum-doped strontium titanate (SrTiO₃:Al) to suppress these reverse processes for boosting photocatalytic H₂ evolution. In situ characterizations reveal a direct Z-scheme charge transfer pathway between PDIP and SrTiO₃:Al, which promotes high‑energy charge carrier separation and suppresses the reverse reaction by spatially segregating the H₂ and O₂ evolution sites onto SrTiO₃:Al and PDIP, respectively. Further, combined with selective co-catalyst engineering for preventing H₂ and O₂ from contacting on the catalyst surface, these reverse processes are fundamentally suppressed. Consequently, the PDIP/SrTiO₃:Al heterojunction exhibits substantially enhanced photocatalytic activity for overall water splitting, achieving an H₂ evolution rate 11.8 times higher than that of pristine SrTiO₃:Al. This dual-suppression strategy provides a validated blueprint for highly efficient solar-to-hydrogen conversion.

We investigate how the assembly of magnetic nanoparticles embedded in a semi-crystalline polymer governs heat generation when submitted to a high-frequency alternating magnetic field by simultaneously monitoring temperature and structural anisotropy through infrared thermography and time-resolved ultra-small-angle X-ray scattering, respectively. A polypropylene matrix is used as a host system to disentangle intrinsic magnetic heating from structural contributions, thereby isolating the additional heat generated by dipolar chain formation above the polymer melting point during successive heating cycles. In contrast, reorienting the chain axis perpendicular to the applied field is found to significantly reduce heat generation. These in situ measurements are complemented by X-ray tomography and scanning electron microscopy experiments, providing a comprehensive view of the underlying mechanisms. Overall, this work establishes a direct relationship between nanoparticle organization and hyperthermia performance, opening new routes for the rational design of functional nanocomposites.

N-heterocyclic microenvironment engineering is critical for modulating the electronic structure and nonlinear optical (NLO) responses of imine-linked covalent organic frameworks (COFs). Using 5′-(4-aminophenyl)–2′,4′,6′-trimethyl-[1,1′:3′,1″-terphenyl]-4,4″-diamine (ATTD), we synthesized three COFs (ACOF-1, ACOF-2, and ACOF-3) via polycondensation with aldehydes bearing N₀, N₁, and N₃ heterocycles, yielding nitrogen contents of 5.25, 6.24, and 8.91%, respectively. Systematic investigation shows that increasing N-content progressively narrows the optical bandgap and strengthens donor–acceptor charge transfer. Open-aperture Z-scan measurements reveal reversible reverse saturable absorption (RSA) to saturable absorption (SA) switching under varying pulse energies for all samples. Closed-aperture Z-scan indicates self-defocusing and RSA for ACOF-1, whereas ACOF-2 and ACOF-3 exhibit asymmetric twin-peak-valley curves, signifying third- and fifth-order nonlinear refractive contributions. Collectively, the N-heterocyclic microenvironment precisely tailors electronic distribution and charge-transfer dynamics, enabling deliberate NLO performance tuning. This work offers a rational guideline for designing high-performance COF-based NLO materials.

Developing sustainable electrocatalysts from waste resources offers an attractive route toward clean energy storage and environmental remediation. Herein, an all-in-waste strategy is reported to upcycle sewage sludge and straw into single-atom catalysts for rechargeable zinc–air batteries. High-energy mechanical shearing coupled with self-atmosphere pyrolysis transforms the waste into hierarchical porous carbon hosting Fe₁–N₄ active sites. The resulting sludge–straw-C catalyst achieves an oxygen reduction reaction kinetic current density of 4.5 mA cm^–2 at 0.75 V, outperforming single-precursor counterparts by 4.1 to 5.6 times. Furthermore, it reduces the oxygen evolution reaction overpotential at 10 mA cm^–2 to 390 mV, a decrease of 120–150 mV. Integrated into rechargeable zinc–air batteries, this catalyst delivers a peak power density of 160 mW cm^–2 and stable cycling over 800 hours. This work provides a scalable and reagent-free route for transforming environmental pollutants into value-added energy materials.

Artificial intelligence-assisted design of electromagnetic wave absorbing coatings is often restricted to geometry or topology optimization within fixed materials. Here, we present a modular particle swarm optimization−proximal policy optimization (PSO−PPO) framework for radar-absorbing metastructures that combines a progressive feature fusion surrogate for 8−18 GHz reflection-loss prediction, a ResNet-based empirical filter for low-performance patterns, and reinforcement learning optimization in a mixed discrete-continuous design space. For broadband single-layer optimization, the framework identifies a generated-material M2/Pt metasurface absorber with a 1.30 mm thickness and a CST-validated effective bandwidth of 6.32 GHz, with field simulations indicating absorption from multiple localized resonances and dielectric loss. The same strategy is extended to multilayer inverse design for prescribed single-peak Gaussian spectra, yielding target responses at 10, 12, and 16 GHz with mean absolute errors (MAEs) of 1.64−2.19 dB. This work demonstrates an efficient route for automated absorber optimization and customized spectral regulation.

Fabricating sustainable room‑temperature phosphorescent (RTP) films without relying on intrinsic chromophores constitutes a fundamental objective, yet it remains an enduring challenge. Here, we present an efficient “top‑down” strategy that directly converts natural bamboo into RTP films. Furthermore, delignification was performed on natural bamboo to extract lignin constituents in the first step. After that, the treated bamboo was subjected to carboxymethylation and subsequently dissolved to form a transparent RTP film (B-film). The as-prepared B-film exhibited blue fluorescence and green phosphorescence, with an RTP lifetime reaching 547.77 ms. Moreover, this film possessed favorable processability and could efficiently transfer energy to Rhodamine B (RhB). As a result, a variety of multifunctional afterglow materials were fabricated by employing the B-film. Simultaneously, the luminescent film underwent rapid and complete biodegradation in soil within 15 days. This work is anticipated to provide a convenient strategy for producing sustainable RTP films from biomass resources.

Postoperative residual disease and insufficient antigenicity after surgical resection are major causes of breast cancer recurrence and metastasis. Pyroptosis enhances antitumor immunity by releasing intracellular antigens but is limited by tight intracellular Ca²⁺ homeostasis and short reactive oxygen species (ROS) lifespan. This study develops a membrane-confined pyroptotic catalytic platform coupling ROS generation with TRP channel-gated Ca²⁺ influx to induce pyroptosis and amplify antigenic stimulation in postoperative residual disease. The system comprises a bifunctional DNAzyme (GH) and a CaO₂-loaded calcium alginate hydrogel (CaO₂-SA). Preoperatively, GH anchors to tumor membranes via nucleolin recognition; postoperatively, CaO₂-SA provides sustained H₂O₂ and Ca²⁺ at the resection site. Membrane-localized GH catalyzes H₂O₂ into hydroxyl radicals to oxidatively damage membranes, activate oxidant-sensitive TRP channels, and drive sustained Ca²⁺ influx. This triggers mitochondrial Ca²⁺ overload and Caspase-3/GSDME pathway activation, inducing potent pyroptosis. The resultant damage-associated molecular patterns amplify antigenicity, addressing insufficient postoperative immunogenicity in breast cancer.

Characterizing the structural and chemical transitions of muscovite mica across various scales and thermal profiles is essential for ensuring the reliability of high-voltage power insulation, aerospace thermal barriers, and nanoscale semiconductor substrates under extreme operational stress. Here, we investigate notch fracture toughness $K_{\mathrm{Ic}}^n$ of muscovite mica as a function of feature size w and temperature T with microscale shear testing. $K_{\mathrm{Ic}}^n$ decreased and then stayed constant as w increased, likely from fabrication-induced changes to the microstructure and roughness. Moreover, $K_{\mathrm{Ic}}^n$ initially decreased and then increased as temperature T increased, with the reversal in trend indicative of a brittle-to-ductile transition. Complementary Raman spectroscopy and molecular dynamics showed that the observed trends were due to an increase in bond lengths and a decrease in critical stresses/strains. In comparing the microscale results to macroscale counterparts, it was surmised that the decrease in brittle-to-ductile transition temperature was due to an increase in the dehydroxylation rate.