Noble metal nanoplates represent a remarkable class of nanostructures that provide a highly compatible geometry for integration with wafer-based processing since the combination unites two systems that have an inherently two-dimensional character. With colloidal syntheses providing exacting controls over nanoplate size, shape, and composition and lithographic processes providing avenues for deterministic positioning, the possibility of carrying out seed-mediated liquid-phase growth modes on arrays of substrate-immobilized seeds becomes attractive. The application of this approach to nanoplate geometries is, however, complicated by the fact that their growth in liquid media requires crystalline seeds with stacking fault defects that act as symmetry-breaking structures able to promote a two-dimensional growth mode in an otherwise isotropic metal. If the nanoplates are to lie flat on the substrate, then it is further required that the seeds have their [111]-axis normal to the substrate surface where the stacking faults occur only along this direction. In this presentation, we demonstrate the utility of using a crystalline substrate as the primary driver for forming substrate-based gold seeds with the internal defect structures and crystallographic alignment required for nanoplate growth. Using this capability along with other controls that are unique substrate-based syntheses, we implement both plasmon-mediated and chemical reduction methods for generating arrays of hexagonal nanoplates, nanotriangles, and helical spirals. The overall process, which is carried out using benchtop techniques, combines nanoimprint lithography, vapor-phase directed assembly of crystalline seeds, and liquid-phase seed-mediated synthesis. Taken together, the work advances the practices and knowhow needed to fully exploit one of the most important nanostructure architectures and, from a broader perspective, contributes to an ongoing effort that sees single-crystal nanomaterials integrated into device platforms.

Periodic arrays of single-crystal gold nanoplates – placing new controls on planar growth modes

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