Intermetallic Nanocrystal Discovery through Modulation of Atom Stacking Hierarchy.

A library of compositionally and structurally well-defined Au-Cu alloy nanocrystals has been prepared via scanning probe block copolymer lithography. These libraries not only allow one to map compositional and structure space but also the conditions (e.g., cooling rate) required to access specific structures. This approach enabled the realization of a previously unobserved architecture, an intermetallic nanoprism, that is a consequence of hierarchical atom stacking. These structures exhibit distinctive diffraction patterns characterized by non-integer-index, forbidden spots, which serve as a diagnostic indicator of such structures. Inspection of the library's pseudospherical particles reveals a high-strain cubic-tetragonal interfacial configuration in the outer regions of the intermetallic nanocrystals. Since it is costly and time-consuming to explore the nanomaterials phase space via conventional wet-chemistry, this parallel kinetic-control approach, which relies on substrate- and positionally isolated particles, may lead to the rapid discovery of complex nanocrystals that may prove useful in applications spanning catalysis and plasmonic sensing.