Polyelemental nanoparticles, which may form multiple crystal structures and geometric architectures, depending on thermodynamic and kinetic conditions, have applications in fields spanning catalysis to plasmonics. However, the composition and crystal structure combinations that have been explored thus far are limited by a lack of combinatorial methods for precisely synthesizing such systems. In this presentation, we discuss a chip-based library that allows for the combinatorial synthesis of polyelemental nanoparticles and the subsequent correlative investigation into their structure–function relationships. Using attoliter polymer nanoreactors that contain metal precursor ions, spatially encoded nanoparticle arrays with controlled sizes and compositions can be synthesized. The spatial encoding enables one to then correlate the composition, crystal structure, and optical responses of individual nanoparticles through various characterization techniques including microscopy and spectroscopy. As an example, we synthesized Au-Cu alloy nanocrystals with arbitrary elemental ratios in either chemically disordered (high-temperature) or ordered (intermetallic, low-temperature) structures that are close to their thermodynamically stable states using a kinetically controlled annealing process. Correlative electron microscopy techniques were used to identify the atom stacking hierarchy, including symmetry, chemical ordering, and stacking discontinuity, down to the single particle level. A multi-well electrochemical testing system was used to rapidly determine the electrochemical properties of these particles, which directly correlate back to their elemental compositions and crystal structures. Additionally, when combined with first-principle calculations, this approach reveals the impact of the bulk and surface structure and non-stoichiometry of alloys to electrochemical processes. Taken together, this combinatorial approach shows vast promise for elucidating the relationship between thermodynamics, hierarchical structures, and electrochemical properties for alloy nanocrystals in a combinatorial manner, and may provide insights that facilitate the design of new functional nanomaterials.

Attoliter polymer reactors as combinatorial tools for understanding alloy nanocrystal structure−function relationship

2019 Spring National Meeting

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