Heterodimers with various bonding positions: Synthesis, plasmon coupling and surface enhanced Raman scattering

Abstract

The novel plasmonic heterodimer with an adjustable self-assembled hot spot is synthesized via the bonding of single core-shell Au@Ag nanocube (Au@Ag NC) and varisized Au nanosphere (Au NS) based on the biotin-streptavidin interaction between single and ensemble assemblies. Due to the various bonding positions, three modes of heterodimers nanostructures (Middle, Vicinity, and Vertice modes) are prepared, and an obvious hot spot generates between the nanosphere and nanocube, showing different characteristics for surface plasmonic resonance effect. The obtained surface enhanced Raman scattering enhancement factors for the three modes of nanostructures have a narrow distribution and can be controlled in order of magnitude via adjusting the dimension of Au NS on single Au@Ag NC. Specifically, the heterodimer with Vertice mode can significant enhance the electric field in the bonding position, which reflects the synergistic action for the inter-particle plasmon coupling effect and the lightning rod effect. This microstructure and corresponding optical characteristic of the heterodimers are of great significance for research in related fields, including plasmonic device, biological detection, and in situ tracking in cells.