Binary\nPlasmonic Assembly Films with\nHotspot-Type-Dependent Surface-Enhanced\nRaman Scattering Properties

Abstract

Tuning and controlling the plasmon\ncoupling of noble metal nanoparticles\nare significant for enhancing their near-field and far-field responses.\nIn this work, a novel heterogeneous plasmonic assembly with a controllable\nhot spot model was proposed by the conjugation of Au nanospheres (NSs)\nand Au@Ag core–shell nanocube (NC) films. Three hotspot configurations\nincluding point-to-point type, point-to-facet type, and facet-to-facet\ntype were fabricated and transformed simply by adjusting the doping\nratio of nanoparticles in the co-assembly film. Expectedly, the localized\nsurface plasmon resonance (LSPR) property and surface-enhanced Raman\nscattering (SERS) performance of the binary assembly film exhibit\ndistinct diversity due to the change in the hotspot conformation.\nInterestingly, the point-to-facet hotspot in hybrid assembly films\ncan provide the most extraordinary enhancement for SERS behavior compared\nwith single-component Au NS and Au@Ag NC plasmonic assemblies, which\nis further confirmed by the finite-different time-domain simulation\nresults of dimer nanostructures. In addition, the two-dimensional\nbinary assemblies of Au NS doping in Au@Ag NCs with excellent sensitivity\nand high reproducibility were successfully applied in the identification\nof ketamine. This work opens a new avenue toward the fabrication of\nplasmonic metal materials with collective LSPR properties and sensitive\nSERS behavior.