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Abstract The construction of thin film heterostructures has been a widely successful archetype for fabricating materials with emergent physical properties. This strategy is of particular importance for the design of multilayer magnetic architectures in which direct interfacial spin-spin interactions between magnetic phases in dissimilar layers lead to emergent and controllable magnetic behavior. However, crystallographic incommensurability and atomic-scale interfacial disorder can severely limit the types of materials amenable to this strategy, as well as the performance of these systems. Here, we demonstrate a method for synthesizing heterostructures comprising magnetic intercalation compounds of transition metal dichalcogenides (TMDs), through directed topotactic reaction of the TMD with a metal oxide. The mechanism of the intercalation reaction enables thermally initiated intercalation of the TMD from lithographically patterned oxide films, giving access to a family of multi-component magnetic architectures through the combination of deterministic van der Waals assembly and directed intercalation chemistry. 

Abstract Electronic and geometric interactions between active and support phases are critical in determining the activity of heterogeneous catalysts, but metal–support interactions are challenging to study. Here, it is demonstrated how the combination of the monolayer‐controlled formation using atomic layer deposition (ALD) and colloidal nanocrystal synthesis methods leads to catalysts with sub‐nanometer precision of active and support phases, thus allowing for the study of the metal–support interactions in detail. The use of this approach in developing a fundamental understanding of support effects in Pd‐catalyzed methane combustion is demonstrated. Uniform Pd nanocrystals are deposited onto Al₂O₃/SiO₂spherical supports prepared with control over morphology and Al₂O₃layer thicknesses ranging from sub‐monolayer to a ≈4 nm thick uniform coating. Dramatic changes in catalytic activity depending on the coverage and structure of Al₂O₃situated at the Pd/Al₂O₃interface are observed, with even a single monolayer of alumina contributing an order of magnitude increase in reaction rate. By building the Pd/Al₂O₃interface up layer‐by‐layer and using uniform Pd nanocrystals, this work demonstrates the importance of controlled and tunable materials in determining metal–support interactions and catalyst activity.