Fabrication of Periodic Arrays of Highly Oriented Plasmonic Heterotrimers via Site-Specific Sequential Colloidal Assembly

Plasmonic nanoarrays show applications in biosensors, nanolasers, and photodetectors, but precisely organizing and orienting nanoparticle (NP) trimers on substrates remains a grand challenge. Here, we present a self-assembly strategy to arrange metallic NPs with distinct diameters into centimeter-scale arrays of highly oriented linear trimers by modulating the balance between capillary forces and coordination-electrostatic interactions. We achieved an 88% yield of plasmonic trimers with ±10° orientation uniformity across 1 cm² substrates by optimizing the ionic strength of the NP solutions. The high uniformity and sub-3-nm interparticle gaps of trimers in arrays enabled the collective polarization-dependent optical responses and high-order plasmonic coupling. Our strategy offers a versatile platform for creating complex nanostructure arrays with heterogeneous assemblies for use in plasmonic devices.