Chemistry of Materials最新文献

Liquid-crystalline organic semiconductors are rapidlygaining attentionas next-generation materials for organic field-effect transistors(OFETs) due to their high charge mobility and thermal durability.However, thermal treatment at temperatures exceeding the transitionpoint of the liquid-crystalline phase degrades device performance,and the relationship between structure and performance remains unclear.In the present study, we investigate 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene, which exhibits outstanding charge-carriertransport properties among liquid-crystalline organic semiconductors.The aggregation structure in thin films is analyzed by combining X-raydiffraction, infrared spectroscopy, and atomic force microscopy, dependingon the heating conditions. Meanwhile, the OFET mobility is measuredin comparison with this structure. A comparative analysis identifiescrystallographic and conformational disorders responsible for thedegradation in OFET performance. This is due to the fact that, evenafter cooling to room temperature, flipped molecules resulting fromthe liquid-crystalline phase transition partially remain in the polycrystallinefilm. In other words, the OFET mobility of liquid-crystalline organicsemiconductors is governed by the film crystallinity, for which theconformational ordering of the alkyl side chains is a prerequisitebut not a sufficient condition. The results demonstrate a clear structure–performancerelationship in liquid-crystalline organic semiconductors, thus facilitatingthe fabrication of high-mobility OFET devices.

Developing high-performance cathode materials is crucialfor advancinggrid-scale sodium-ion batteries (SIBs). Here, we introduce a P2-typelayered oxide cathode material, Na_0·67Ni_0·33Mn_0·51Ru_0·16O₂, whichdemonstrates exceptional electrochemical performance through a robustdual cationic–anionic redox mechanism. This material deliversa high discharge capacity of 175.6 mAh g⁻¹ at anaverage voltage of 3.6 V and maintains remarkable cycling stabilitywith ∼93% capacity retention after 1000 cycles. A key to thisperformance is the strategic Ru doping, which plays a pivotal rolein electronically stabilizing the oxidized oxygen states. By mediatingthe reversible formation of oxygen holes and preventing oxygen undercoordination,the Ru dopant stabilizes the anionic redox process. Unlike Na-richlayered oxides, this ligand-to-metal charge-transfer mechanism effectivelysuppresses detrimental oxygen evolution and preserves the structuralintegrity of the layered Na-deficient P2-type framework. This designstrategy enables a synergistic redox landscape, confirmed by ex situ and operando advanced characterizationsand theoretical calculations such as Fukui functions, offering criticalinsights into the rational design of high-capacity cathode for next-generationSIBs.

Targeted halide substitution provides an effective routeto accessstructural motifs in thio-LISICON systems. Here, partial substitutionof S^2– by Cl^– in Li₄GeS₄ stabilizes a hexagonal polymorph near the compositionLi_3.25GeS_3.25Cl_0.75. Ab initio structuredetermination by joint refinement of time-of-flight neutron powderdiffraction and X-ray diffraction data supports a P6₃mc average structure built on a hexagonalclose-packed anion framework. The resulting framework exhibits a distinctLi-site topology with symmetry-inequivalent Li environments, includinga shared tetrahedral framework site and additional tetrahedral andoctahedral interstitial sites. Systematic investigation of the Li_4–xGeS_4–xCl_x series shows that the hexagonalphase is preferentially stabilized near the nominal x = 0.75 composition, for which no secondary crystalline phase wasdetected by PXRD. Structural analysis indicates that halide substitutionproduces a rearranged and partially disordered Li substructure. Bond-valenceenergy landscape calculations show that the computed Li-energy topologyis highly sensitive to the representation of Li/Ge occupational disorder,with a Ge-free sensitivity model recovering the crystallographic Li1-relatedminimum and markedly altering the calculated percolation topology.Li_3.25GeS_3.25Cl_0.75 exhibits a room-temperatureionic conductivity of 3.91 × 10^–6 S cm^–1. These results demonstrate that halide substitutioncan stabilize hexagonal polymorphs and reorganize the Li substructurein sulfide solid electrolytes, providing a platform for examininghow structural disorder and Li-site topology influence ion transport.

Layered halide perovskites (LHPs)offer a powerful platformtoprecisely engineer excited-state carrier dynamics and optoelectronicperformance via compositional tuning of B-site metals. Here, we contrastprototypical lead-based (BA)₂PbBr₄ with itsdouble-perovskite analogue (BA)₄AgBiBr₈ to isolatethe role of B-site chemistry in dictating photoactivity in these emerginglayered semiconductors. Nonadiabatic molecular dynamics integratedwith interpretable machine learning models reveal the detailed impactof time-dependent structural distortions on the instantaneous electronicstructures in these LHPs. The alternating [AgBr₆]^5– and [BiBr₆]^3– octahedral arrangementin (BA)₄AgBiBr₈ gives rise to intrinsicallystronger structural fluctuations and enhanced electron–phononcoupling, leading to faster nonradiative recombination than that ina more rigid Pb-based framework. Extensive SHapley Additive exPlanationsanalyses further depict that the thermally driven octahedral distortionsin the [AgBiBr₈]⁴⁺ layers exert the strongestcontrol over excited-state charge dynamics at ambient conditions.The intrinsic structural anisotropy in adjacent Ag/Bi-centered octahedrastrengthens electron–phonon coupling, activating nonradiativerecombination channels and consequently suppressing the photoluminescence.Our findings establish a mechanistic link among inorganic sublatticecomposition, structural dynamics, and carrier lifetimes, presentingkey design principles to realize high-performing lead-free LHPs foroptoelectronics.

Thermal interface materials (TIMs) require both efficientheattransfer, reliable interfacial contact, and long-term damage tolerance,yet highly filled polymer composites often suffer from poor deformability,irreversible interfacial damage, and increased contact thermal resistance.Herein, a dual-network self-healing polydimethylsiloxane (SH-PDMS)matrix was designed using a dual-functional cross-linker that integratespermanent covalent cross-links with reversible Diels–Alder(DA) dynamic bonds. The permanent network provided structural stability,while the reversible DA bonds enabled thermally triggered networkrearrangement and self-healing. Thermally conductive composites containingAl₂O₃, boron nitride, and ZnO/carbon fiber fillerswere further prepared to examine how filler architecture affects self-healingbehavior, recoverable thermal transport, and interfacial contact thermalresistance. Among the tested composites, ZnO/carbon fiber/SH-PDMSachieved the highest thermal conductivity of 2.5 W·m^–1·K^–1 owing to the formation of long-rangeconductive pathways and local thermal bridges. After mechanical damage,the thermal conductivity of all composites decreased substantiallybut recovered to more than 90% of the original value after healing,demonstrating efficient restoration of disrupted heat-transfer pathways.Notably, the thermal conductivity recovery was much higher than thecorresponding mechanical recovery, indicating that heat-transfer restorationdoes not require complete recovery of the load-bearing network. Thethermally treated SH-PDMS-based TIMs also exhibited reduced contactthermal resistance under mild pressure, with ZnO/carbon fiber/SH-PDMSreaching 0.205 K·cm²·W^–1 at70 psi. In an LED–TIM–heat sink assembly, the ZnO/carbonfiber/SH-PDMS TIM reduced the maximum LED temperature from 68.1 °Cto 51.8 °C. These results demonstrate that the dual-network SH-PDMSmatrix provides a promising route for self-healing TIMs with recoverablethermal transport and low contact thermal resistance.

Fluorine-freeionic liquids and salts are attracting growing interestas safer and more sustainable electrolyte components for Li-ion batteries,addressing both the flammability of conventional carbonate-based electrolytesand the environmental persistence of fluorinated anions. This motivatesthe use of the nonfluorinated acesulfame (ACE^–)anion, derived from potassium acesulfame, a toxicologically evaluatedtabletop sweetener. Further, ether-functionalized cations may facilitatelithium-ion transport by promoting favorable lithium coordinationenvironments. Here, two ionic electrolytes were prepared by combiningthe ACE^– anion with either the cyclic-ether N-ethyl-N-methyloxazolidinium (C₂moxa⁺) cation or the N-methoxy-N,N,N-trimethylammonium(N_111(1O1)⁺) cation, where the ether is functionalizedon the side chain, and lithium acesulfame (Li-ACE) to evaluate theirpromise as battery electrolytes. The thermal and transport propertiesand the ion dynamics were studied and compared at various Li-ACE concentrations.Among all the lithium-based electrolyte systems, [N_111(1O1)][ACE] containing 10 mol % Li-ACE exhibited the highest conductivity,reaching 5.4 × 10^–4 S cm^–1 at 50 °C. However, [C₂moxa][ACE] exhibited a higherLi⁺ diffusivity ratio at both 20 and 50 mol % Li-ACE content,indicating that the cyclic ether oxygen may create a distinct localchemical environment that facilitates greater relative mobility ofLi⁺. Additionally, the Li⁺ solvation environmentin acesulfame-based electrolytes was elucidated using combined experimentaland simulation approaches. In both electrolytes, Li⁺ wasfound to coordinate with ACE^- through the nitrogenatom as well as the sulfonyl and carbonyl oxygens. Moreover, moleculardynamics simulations suggest that smaller Li–Li clusters wereformed in [C₂moxa][ACE] electrolytes compared to [N_111(1O1)][ACE], which may contribute to the enhanced Li⁺ mobility compared with ACE^– in [C₂moxa][ACE] electrolytes at 20 and 50 mol %. These results indicatethat cation chemistry plays an important role in tuning Li⁺ solvation structure, ion clustering, and ion transport.

Controllinglocal coordination environments of second-orderJahn–Teller(SOJT)-active post-transition metal cations remains a significantchallenge due to their inherent preference for asymmetric environments.Previously, we reported that the high-symmetry Y³⁺ sitein layered Bi₂YO₄Cl can serve as a structuraltemplate to stabilize a centrosymmetric coordination environment forBi³⁺ (up to 40% replacement), effectively suppressing theSOJT distortion. In this study, we re-examined the synthesis processof Bi₂(Y_1–xBi_x)O₄Cl and successfully increased the Bioccupancy at the high-symmetry site to x = 0.8, approximatelydoubling the previously accessible composition range. At this highsubstitution level, the system is practically better described asa Y-substituted Bi₃O₄Cl rather than a Bi-substitutedBi₂YO₄Cl. First-principles calculations, togetherwith comparative experiments using other trivalent cation dopantsof different ionic radii, reveal that chemical pressure is a key factorgoverning the suppression of the SOJT distortion and the resultingband gap narrowing. These findings provide insight into the stabilizationof unusually high-symmetry coordination environments in SOJT-activepost-transition-metal compounds for tuning their electronic structures.

Two-dimensional covalent organic frameworks (2D COFs)are promisingporous materials with vast yet largely unexplored design space arisingfrom diverse building blocks (BBs) and crystal topologies. Efficientcrystal structure prediction (CSP) and inverse design of 2D COFs thereforeremain highly challenging. Here, we develop COFFlow, a flow-matching-based generative framework for CSP of 2D COFs.A COF-specific deconstruction algorithm is introduced to consistentlydecompose periodic COFs into experimentally relevant BBs across diversetopologies, enabling direct generative assembly of periodic frameworksfrom BB representations. Systematic evaluations demonstrate that COFFlow can reliably and efficiently generate structurallyconsistent and chemically valid 2D COFs. Beyond the commonly usedmatch rate (MR), we further introduce validity rate (VR) to assessthe chemical validity of generated structures. The models exhibitnontrivial extrapolation capability toward unseen BBs and crystaltopologies, although preserving chemical validity under strong distributionshifts remains challenging. To demonstrate the practical utility ofthe framework, we integrated COFFlow with data-drivenscreening and inverse design of 2D COFs for methane storage. Usingdeliverable capacity as the target metric for adsorbed natural gasapplication, we identified several previously unreported 2D COFs withperformance among the highest reported to date. More broadly, thiswork establishes a scalable framework for AI-driven discovery anddesign of reticular materials.

Oxygen loss in magnetite drives thecation redistributionand localstructural reconstruction that control the rate of iron oxide reduction,but this coupling has resisted direct simulation: the reconstructiondevelops far beyond DFT-accessible scales, and classical potentialscannot describe mixed-valence Fe–O with the required fidelity.We developed a DFT-validated Fe–O Deep Potential trained onbulk, defective, and surface configurations and applied it in large-scalemolecular dynamics with an imposed stochastic oxygen-removal protocol.The potential reproduces DFT energy and force trends together withvacancy and surface energetics. DFT single-point checks on oxygen-deficientconfigurations and equation-of-state calculations for Fe₃O₄ and FeO further delineate the transferability of thepotential, with larger deviations emerging in the most strongly oxygen-deficientstates. As oxygen is removed, four-coordinated O environments decreasewhile six-coordinated wüstite-like motifs emerge, grow, andcoalesce into extended local domains. Deep-Potential nudged elasticband (DP-NEB) calculations, benchmarked against selected DFT single-pointenergies, show that the coupled O/Fe-vacancy configuration gives thelowest Fe-migration barrier among the selected local rearrangementpathways. Time-windowed mean-squared displacements yield apparentFe and O diffusivities that evolve in the nonstationary lattice. Thesesimulations establish a defect-mediated solid-state response towardwüstite-like local order under imposed oxygen-deficient conditions,rather than the formation of a complete equilibrium Fe_1–xO phase. The protocol isolates oxide-side reconstruction and doesnot explicitly treat hydrogen chemistry.

The convergence of artificial intelligenceand biomedicine is creatingopportunities for smart sensing systems in precision medicine. Conventionalsensors, however, remain dependent on external power sources. Shortbattery life, difficult replacement, and potential biological riskslimit their use in implantable, wearable, and long-term monitoringapplications. Self-powered smart sensing systems offer a promisingalternative. These devices harvest ambient energy from mechanical,thermal, chemical, or biological sources and convert it directly intoelectricity. The result is an integrated sense-and-power unit. Thisparadigm provides a direction for next-generation medical devices.In this review, we summarized recent progress in the field by focusingon two key healthcare applications. The first is the ultrasensitivedetection of biomarkers for early cancer diagnosis. The second isthe construction of intelligent closed-loop wound management systemsthat combine real-time monitoring with precise treatment. We discussedthe working mechanisms, core materials, and system architectures ofthese devices. We also identify current challenges and outline futureresearch directions. We intend this review for a broad interdisciplinaryaudience, including researchers in materials science, electronic engineering,biomedical engineering, and clinical medicine who are working on self-poweredsensing systems for healthcare.