Chemistry of Materials最新文献

Atomic layer deposition(ALD) supercycles, formed bycombiningdistinct binary ALD cycles in different ratios offer a versatile routeto deposit multicomponent materials. However, predictive compositioncontrol is often limited by initial growth effects that arise whenswitching between ALD chemistries. These effects are particularlyrelevant for the deposition of metal phosphate thin films but remaininsufficiently understood. Here, we investigate supercycles combiningone zinc oxide (ZnO_x: diethylzinc (DEZ)–O₂ plasma) and varied (n = 1–5) phosphorusoxide (PO_y: trimethylphosphate (TMP)–O₂ plasma) ALD subcycles to deposit zinc phosphate thin films.The resulting films exhibit tunable morphology and stoichiometry,spanning compositions from P-doped ZnO_x over P-rich zinc orthophosphate to Zn-rich zinc metaphosphates asa function of the supercycle definition. The film growth also showsa strong dependence on the supercycle definition and is quenched beyonda critical number of PO_y subcycles. Experimentaldata complemented by density functional theory (DFT) demonstrate thatthe surface reactions of both DEZ and TMP are highly sensitive tothe growth surface established by the preceding subcycles, particularlythe balance between surface groups that promote facile precursor chemisorptionand those which demonstrate only weak interactions with precursors.As the phosphorus content increases, the film growth is suppressedby the depletion of sites promoting chemisorption, limiting the achievablestoichiometry control for practical growth rates of the films. Thesefindings highlight how initial growth effects govern supercycle ALDand underscore their importance for achieving controlled synthesisof metal phosphate materials.

Electrochemicalnitrate reduction reaction (NO₃RR) andcarbon dioxide reduction reactions (CO₂RR) can serve asenvironmental remediation tools for pollution control and thus supporta circular economy for sustainability. The electrochemical processrelies heavily on electrode materials; thus, developing highly activeand efficient electrocatalysts for these reactions in a green andcost-effective way is essential. In this study, we examined cobaltporphyrins with different modifications for electrochemical NO₃RR and CO₂RR to independently produce ammonia andacetic acid/formic acid. The carboxylic acid group-substituted cobalttetrakis(p-tolyl) porphyrin showed a high Faradaic efficiency of 94%for ammonia, 33.8% for CH₃COOH, and 21.1% for HCOOH atvarious potentials in a neutral pH (∼7) electrolyte. Computationalresults suggest enhanced binding of key NO₃RR and CO₂RR intermediates to the −COOH group-substituted cobaltporphyrin during electrocatalysis.

Viscoelastic hydrogels are increasingly being used inthe biomedicalfield, with applications ranging from 3D cell culture to drug delivery.Boronate ester (BE) formation is one of the dynamic covalent reactionsthat can be used for viscoelastic hydrogel design. BE formation standsout for the stability and relative bioorthogonality of its precursors,i.e., phenylboronic acids and diols. However, BE hydrogels usuallylack stability, are soft, and behave like fast-relaxing viscoelasticliquids at physiological pH due to low BE binding strength. To addressthese limitations, we performed a combinatorial screening of BE crosslinkingpairs based on PBAs and cyclic cis-diols, using hyaluronicacid as a base polymer. Our study revealed the unique ability of norbodiol,a bridged bicyclic cis-diol, to form BE hydrogelswith all the PBAs tested. We demonstrated that this is due to norbodiol’sexceptional association constants (K_a)with PBAs, which can reach values of up to 6600 M^–1. Compared to a list of other diols, we further showed that the remarkableproperties of norbodiol could be explained by its rigid bicyclic structureand the specific three-dimensional orientation of its two hydroxylgroups. These findings provide initial insights toward a deeper understandingof the optimal diol structure for BE formation and stability. Norbodiol-basedBE crosslinking produced hydrogels whose relaxation properties were20- to 200-fold greater than those of previous systems. We furtheroptimized two hydrogel formulations with single or dual BE crosslinkingfor use in various biomedical applications, highlighting the potentialof our discovery.

Here, we report a novel approach to borate flux synthesisin whichrefractory oxide additives alter reaction phase outcome. In the absenceof refractory additives, reactions of copper oxide and boron oxideflux yielded single crystals of the previously reported Cu₁₅(BO₃)₆(B₂O₅)₂O₂ (Cu₃B₂O₆), containingsolely trigonal planar-coordinated borate monomers and dimers. Additionof TiO₂ led to the discovery of a novel structural prototypeCu_7–x+yTi_x(BO₃)(B₂O₅)(B₃O₇)O (Cu_7–x+yTi_xB₆O₁₆), which crystallizes in space group P1̅, with a = 3.31989(4) Å, b = 10.54906(13) Å, c = 17.9143(2) Å, α= 75.5076(10)°, β = 88.8619(10)°, and γ = 86.7381(10)°for x = 0.276(7), y = 0.0135(15).It consists of quasi-2D layers of Cu²⁺ cations enclosingtrigonal planar borate monomers, dimers, and the uncommon (B₃O₇)^5– trimer. Adjacent layers are connectedby oxygen and disordered Cu/Ti sites. In contrast, both ZrO₂ and HfO₂ grew single crystals of the previously reportedmaterial CuB₂O₄ containing solely tetrahedrallycoordinated boron in a 3D framework. Ex situ X-ray μCT imagingof the ZrO₂ reaction shows CuB₂O₄ crystals growing at the interface of ZrO₂ and the flux,suggesting that ZrO₂ (and by extension, HfO₂) acts as a heterogeneous nucleation substrate that stabilizes thefour-coordinate boron tetrahedra. Magnetization of Cu_7–x+yTi_xB₆O₁₆ is reported, showing an antiferromagnetictransition at T_N = 12.8K. We then differentiate refractory additives into two distinct classes,flux-resistant and flux-susceptible, with ZrO₂ and HfO₂ as B₂O₃-flux-resistant refractory additivesand TiO₂ as a B₂O₃-flux-susceptiblerefractory additive. These results demonstrate that refractory additivescan provide a useful handle for directing phase formation and accessingnew materials in flux synthesis, and provide challenge cases to benchmarkemerging AI models in unconventional materials stabilization and crystalgrowth methods.

Piezocatalytic water splitting presents an emerging routefor producing“green hydrogen” that can overcome several limitationsof photocatalytic and electrocatalytic systems. However, existingpiezocatalysts are few, and the insufficient polarization efficiencyof these piezocatalysts is a critical obstacle to practical applications.Rational design of a macroscopic polarizable piezocatalyst from thedesign point of crystal structure for highly efficient hydrogen evolutionis promising but still challenging. In this study, we propose a chemicalcosubstitution strategy using the classic BiOIO₃ with anAurivillius-related crystal structure as the parent structure, wheresynergistic substitution of O^2–/IO₃^– with F^–/SeO₃^2– yields a macroscopic polarizable piezocatalyst, bismuth selenitefluoride BiFSeO₃. Systematic morphological engineeringtuned by mechanical ball milling (1–4 h) revealed a volcano-shapedstructure–activity relationship between H₂ evolutionactivity and milling duration, with the 3-h milled sample (e.g., BiFSeO₃-3 nanosheets) achieving the maximum rate of 1.059 mmol·g^–1 h^–1. Furthermore, mechanistic investigationsintegrating PFM, EPR, and band theory confirm the enhanced piezoelectricproperties (d₃₃ = 196 pm V^–1) and strain-drivencharge separation pathways in BiFSeO₃-3 nanosheets.

Quantum spin liquids (QSLs) are exotic states of matterwhere geometricfrustration and quantum fluctuations suppress conventional magneticorder. S = 1/2 kagome antiferromagnets (KAFMs) are an ideal platformfor realizing such behavior, and several mineral-inspired Cu²⁺-based kagome systems have emerged as promising candidates. Amongthese, Averievite (Cu₅V₂O₁₀CsCl)offers a structurally distinct route to frustrated magnetism throughits copper oxovanadate framework, which hosts alternating kagome andhoneycomb layers. Prior studies have shown that targeted Zn²⁺ substitution on the honeycomb Cu_H site can suppress magneticorder and promote QSL-like behavior. Here we investigate Mg²⁺ substitution in the Averievite family, motivated by the geometricflexibility and favorable scattering contrast of Mg²⁺ relativeto Zn²⁺, the previously explored diamagnetic dopant. Hereinwe present the novel Mg_xCu_5–xV₂O₁₀CsCl (x = 0, 0.5, 1, 2) family, utilizing X-ray diffraction, single-crystalelectron diffraction, and SQUID magnetometry to obtain precise structuralparameters, including site occupancies, antisite disorder, and localcoordination information, and to correlate these with the varied magneticbehavior. Increasing Mg²⁺ content leads to a pronouncedsuppression of both the structural and long-range magnetic ordering,alongside an increased mean field antiferromagnetic interaction, signalingenhanced magnetic frustration. Crucially, electron diffraction datais indicative of less than 1% Mg²⁺ antisite disorder ontothe kagome lattice in the Mg₂ compound. This contrastswith Zn-based analogues, preserving the integrity of the S = 1/2 kagomenetwork. At x = 2, neither long-range order nor spinfreezing is observed down to 2K, giving a new S = 1/2 KAFM with earlyhallmarks of QSL behavior and establishing Mg-doped Averievite asa clean and highly tunable platform for exploring QSL ground states.

Boraneclusters represent a unique class of molecular materialsfeaturing electron-deficient bonding and diverse polyhedral architectures.While their electronic, photophysical, and chemical properties havebeen extensively explored, the influence of polyhedral architectureon their mechanical behavior remains largely unknown. Here, we investigatethe nanomechanical properties of two prototypical-docosahydrooctadecaboraneisomers (syn-B₁₈H₂₂ and anti-B₁₈H₂₂) through nanoindentationexperiments, density functional theory (DFT) calculations, crystallographicand energy-framework analyses. The crystals exhibit exceptional mechanicalrobustness, displaying elastic modulus (E) of ∼20GPa for syn-B₁₈H₂₂ (syn -B₁₈) and ∼17 GPa for anti-B₁₈H₂₂ (anti -B₁₈), despite being composed exclusively of boron andhydrogen atoms and lacking conventional strong hydrogen-bonding networks.Structural analyses reveal that both isomers adopt three-dimensionalinterlocked packing arrangements sustained by multiple B···μHBB, B-H···B, and B···B contacts. In contrast, the parent single-polyhedral boranecrystal of B₁₀H₁₄ exhibits a substantially lowerelastic modulus (∼9 GPa) and has lower-dimensional interactionnetworks in the solid state. The structure-mechanical property correlationpresented here establishes a clear relationship between polyhedralarchitecture, intermolecular interaction topology, and mechanicalperformance in borane molecular crystals. More broadly, this workidentifies macropolyhedral fusion as a structural design strategyfor enhancing the mechanical robustness of cluster-based molecularsolids and expands the emerging materials chemistry of borane-derivedcrystalline materials.

Long-duration energystorage is needed to acceleratedecarbonization.Lithium-ion batteries are currently state-of-the-art but require costlytransition metal oxide cathodes, which can limit their scalability.Dual-graphite batteries are a promising chemistry featuring a graphiteanode and graphite cathode, where cation and anion intercalation occurat the former and latter electrodes, respectively. Conventional small-molecule-basedelectrolytes face safety issues due to their flammability and volatility,and they limit the energy density of dual-graphite batteries due tothe presence of species other than the active ions. Molten salt electrolytesare thus a promising alternative to conventional dual-graphite batteryelectrolytes due to their intrinsic safety and energy density. Here,we report the investigation of a low-melting, single-cation imide-basedbinary molten salt electrolyte to enable “Carbon-and-Salt”batteries. We find that both anions in the Li(FSI)_x(FTFSI)_1–x electrolytesthat were studied reversibly intercalate into graphite cathodes, butthat FTFSI^– preferentially intercalates and is presentin greater compositions in anion-graphite intercalation compoundscompared to the bulk electrolytes. Furthermore, we find that lithiumco-intercalates with the anions, suggesting the inability of anionsto fully de-solvate from tightly-bound aggregate networks. The systematicinvestigation of anion and cation (co-)intercalation behavior fromimide-based molten salts is important to guide the design of next-generationsolvent-free and transition-metal-free “Carbon-and-Salt”batteries.

Competing magneticphases in frustrated systems provide a fertileground for unusual magnetic and electronic responses owing to theirsensitivity to external perturbations. The distorted kagome antiferromagnetHoPtSn is an example of such a system, exhibiting successive magnetictransitions and multiple field-induced metamagnetic states at lowtemperatures. Here, we combine magnetic susceptibility, heat capacity,magnetotransport, and magnetization under hydrostatic pressure measurementson single crystals to investigate the interplay between the competingmagnetic phases in HoPtSn. At ambient pressure, HoPtSn undergoes twomagnetic transitions at T_N1 ≈ 7.3K and T_N2 ≈ 2.7 K. The lower-temperaturetransition is accompanied by pronounced thermal and magnetic hysteresis,indicating its first-order character. Magnetization measurements reveala series of field-induced transitions and a strongly anisotropic low-temperaturephase diagram. Correspondingly, the magnetotransport exhibits sharpanomalies across the metamagnetic transitions together with clearfield-history dependence, while Hall resistivity measurements revealadditional features that emerge within the ordered state. These resultspoint to a strong coupling between electronic transport and magneticreconstruction. Hydrostatic pressure leaves T_N1 nearly unchanged, while it gradually shifts T_N2 to higher temperatures, indicating that the competingmagnetic phases respond differently to lattice compression, whilethe first-order transition remains robust throughout the investigatedpressure range. Electronic structure calculations reveal several Dirac-likecrossings near the Fermi level, suggesting possible interplay betweenthese features and the complex magnetic phase space. Taken together,our results show that HoPtSn hosts a delicate balance between competingmagnetic states, whose reconstruction leaves distinct signatures inthe transport properties and can be continuously tuned by pressure.These findings highlight distorted kagome antiferromagnets as a promisingplatform for exploring the interplay between magnetic phase competitionand electronic transport.