Composition-adjustable Ag–Au substitutional alloy microcages enabling tunable plasmon resonance for ultrasensitive SERS

Engineering the surface plasmon resonance (SPR) properties is a critical issue for improving device performance in the fields of plasmonics, nanophotonics, optoelectronics, and electrochemistry. Here, we demonstrated a programmable manipulation of the surface plasmon resonance (SPR) effect using composition-adjustable Ag–Au substitutional alloy microcages (SAMCs) through a facile NaBH4-cooperative galvanic replacement reaction. The SPR frequency of the Ag–Au SAMCs can be continuously and exquisitely manipulated without resonance damping or broadening via accurate adjustment of the elemental composition distribution at the perfect homogeneity on the atomic-level. Significantly, both the tunable SPR frequency and excellent chemical stability synergistically endow the hollow Ag–Au SAMCs with excellent SERS sensitivity and reproducibility, which lays a foundation for the realization of trace detection of thiram at an ultralow concentration of 1 × 10−12 M. This strategy is a promising candidate for efficient promotion of the SERS activity for metal-based substrates.