All-Hot-Spot Bulk Surface-Enhanced\nRaman Scattering\n(SERS) Substrates: Attomolar Detection of Adsorbates with Designer\nPlasmonic Nanoparticles

Abstract

Here we report a synthetic pathway toward Au truncated\noctahedral\ndual-rim nanoframes wherein two functional facets are formed including\n(1) eight hot nanogaps formed by hexagonal nanoframes embracing core\ncircular nanorings for near-field focusing and (2) six flat squares\nthat facilitate the formation of well-ordered arrays of nanoframes\nthrough self-assembly. The existence of intra-nanogaps in a single\nentity enables strong electromagnetic near-field focusing, allowing\nsingle-particle surface-enhanced Raman spectroscopy. Then, we built\n“all-hot-spot bulk SERS substrates” with those entities,\nwherein the presence of truncated terraces with high homogeneity in\nsize and shape facilitate spontaneous self-assembly into a highly\nordered and uniform superlattice, exhibiting a limit of detection\nof attomolar concentrations toward 2-naphthalenethiol, which is 6\norders lower than that of monorim counterparts. The observed low limit\nof detection originates from the combined synergic effect from both\ninter- and intraparticle coupling in a superlattice, which we dubbed\n“all-hot-spot bulk SERS substrates”.