Epitaxially aligned single-crystal gold nanoplates formed in large-area arrays at high yield

Well-tailored nanomaterials with a single-crystal character provide ideal building blocks for on-chip plasmonic devices. Although colloidal methods have demonstrated mastery over the synthesis of such structures, it has proven quite difficult to deploy these same nanomaterials on substrate surfaces in a highly deterministic manner where precise control over position and orientation is ensured. Herein, we demonstrate a room-temperature two-reagent liquid-phase seed-mediated synthesis of gold nanoplates directly on substrate surfaces in arrays over a square-centimeter area. The synthesis is reliant on benchtop lithographic and directed-assembly processes that give rise to single-crystal seeds of gold that express both an epitaxial relationship with the underlying substrate and the internal defect structure required to promote a two-dimensional growth mode. The resulting structures are highly faceted and, because seed-substrate epitaxy is imposed upon the growing nanoplates, are identically aligned on the substrate surface. Nanoplate yields are increased to values as high as 95% using a post-processing sonication procedure that selectively removes a small population of irregularly shaped nanostructures from the substrate surface, and in doing so, gives rise to an uncompromised plasmonic response. The work, therefore, advances the techniques needed to integrate single-crystal nanomaterials with wafer-based technologies and provides leading-edge capabilities in terms of defining large-area arrays of plasmonic structures with the nanoplate geometry.