Regioselective plasmonic coupling in metamolecular analogs of benzene derivatives

In analogy with benzene-derived molecular structures, we construct plasmonic metamolecules by attaching Au nanospheres to specific sites on a hexagonal Au nanoplate. We employ a ligand exchange strategy that allows regioselective control of nanosphere attachment and study resulting structures using correlated electron microscopy/optical spectroscopy at the single-metamolecule level. We find that plasmonic coupling within the resulting assembly is strongly dependent on the structure of the metamolecule, in particular the site of attachment of the nanosphere(s). We also uncover a synergy in the polarizing effect of multiple nanospheres attached to the nanoplate. Regioselective control of plasmonic properties demonstrated here enables the design of novel structure-dependent electromagnetic modes and applications in three-dimensional spatial nanosensors.