Plasmonic Multi‐Layered Built‐in Hotspots Nanogaps for Effectively Activating Analytes

Abstract Multi‐layered plasmonic nanostructures are able to highly promote the near‐field confinement and effectively activate analytes, which are of predominate significance but are extremely challenging. Herein, the semi‐open Au core@carved AuAg multi‐shell superstructure nanoparticles (multi‐Au@Ag‐Au NPs, multi = mono, bi, tri, tetra, and penta) are reported with a high designability on electromagnetic field and capability of effectively capturing analytes. By controlling synthetic parameters such as the number of galvanic exchange and Ag growth, multi‐Au@Ag‐Au NPs are successfully obtained, with tunable layer numbers and asymmetric nanoholes. Due to collective plasmon oscillations of multi‐layered built‐in nanogaps, the electromagnetic field strength of a single penta‐Au@Ag‐Au entity reach 48841. More importantly, the penta‐Au@Ag‐Au NPs show a remarkable light‐harvesting capability, which is adaptive to different Raman lasers, supporting high‐diversity detection. Additionally, the structural specificity allows analytes to be sufficiently captured into interior hotspots, and further achieve highly sensitive detection with limit of detection down to 3.22 × 10 −12 M. This study not only provides an effective pathway for integrating abundant hotspots and activating target molecules in single plasmonic superstructure, but stimulates advancements in SERS substrates for various applications.