Plasmonic Truncated Satellite Octahedral Nanoparticles: Interior Nanocavities and Exterior Nanotrenches Synergistically Maximize Near-Field Focus

We synthesized a new type of complex nanoparticle: truncated satellite octahedral Au nanoparticles (SONs). The synthesis began with octahedral Au nanoparticles, followed by selective Pt deposition and a mild polyol synthesis to generate triakis-octahedral Ag nanoparticles (TONs). Subsequent Au deposition on the TONs led to the formation of cavities within the shell, and selective growth of truncated satellite structures from each (111) facet resulted in SONs with exposed line-shaped nanotrench gaps along the edges of the outer octahedral structure. The SONs exhibited strong near-field focusing in single-particle surface-enhanced Raman spectroscopy (SERS) measurement due to (1) efficient focusing by the exterior line-shaped nanotrench gaps and (2) activation of internal hot nanocavities as the exterior Au shell enabled 785 nm light penetration, producing additional field enhancement. SONs were applied to SERS-based imaging of liposarcoma cells, and the high signal stability of SON nanoparticles enabled cell imaging for up to 4 weeks.