Hexoctahedron in a Nanoframe: Tailoring Stationary and Open Nanogaps for Single-Particle Surface-Enhanced Raman Scattering

Plasmonic nanostructures with sharp features and nanogaps have been of immense interest in surface-enhanced Raman scattering (SERS) applications due to their strong hot spots generated at such morphological features. Here, we report a synthetic route to produce Au hexoctahedron-in-a-nanoframe structures (Au HIAFs), in which the high-curvature vertices of the Au hexoctahedral nanocrystal core fit tightly into the frame corners without the aid of an anchoring linker, realizing stationary, open nanogaps at sharp features within a single nanostructure. The prepared Au HIAFs can effectively exploit both sharp feature- and gap-enhanced electromagnetic fields, thereby exhibiting prominent SERS performance at the single-particle level. Due to the finely controlled, linker-free nanogaps of the Au HIAFs, the SERS detection of a series of analyte molecules could also be possible with an identical single Au HIAF through the reversible adsorption and desorption of analytes, highlighting their potential as a practical, reusable substrate for SERS-related applications.