Binary Plasmonic Assembly Films with Hotspot-Type-Dependent Surface-Enhanced Raman Scattering Properties

Tuning and controlling the plasmon coupling of noble metal nanoparticles are significant for enhancing their near-field and far-field responses. In this work, a novel heterogeneous plasmonic assembly with a controllable hot spot model was proposed by the conjugation of Au nanospheres (NSs) and Au@Ag core-shell nanocube (NC) films. Three hotspot configurations including point-to-point type, point-to-facet type, and facet-to-facet type were fabricated and transformed simply by adjusting the doping ratio of nanoparticles in the co-assembly film. Expectedly, the localized surface plasmon resonance (LSPR) property and surface-enhanced Raman scattering (SERS) performance of the binary assembly film exhibit distinct diversity due to the change in the hotspot conformation. Interestingly, the point-to-facet hotspot in hybrid assembly films can provide the most extraordinary enhancement for SERS behavior compared with single-component Au NS and Au@Ag NC plasmonic assemblies, which is further confirmed by the finite-different time-domain simulation results of dimer nanostructures. In addition, the two-dimensional binary assemblies of Au NS doping in Au@Ag NCs with excellent sensitivity and high reproducibility were successfully applied in the identification of ketamine. This work opens a new avenue toward the fabrication of plasmonic metal materials with collective LSPR properties and sensitive SERS behavior.

Automated summary

Tuning and controlling the plasmon coupling of noble metal nanoparticles are crucial for enhancing their responses in near-field and far-field. A novel heterogeneous plasmonic assembly with a controllable hot spot model was proposed in this work, showing significant enhancement for SERS behavior in point-to-facet hotspots. The binary assemblies of Au NS doping in Au@Ag NCs demonstrate excellent sensitivity and high reproducibility in the identification of ketamine, indicating a new avenue for fabricating plasmonic metal materials with collective LSPR properties and sensitive SERS behavior.