Tunable shell thickness in analyte-responsive core-shell plasmonic arrays at liquid-liquid interface for dual-mode optical sensing.

The presence of H2S in aqueous environment can cause serious health risks to human health. Allicin (diallyl trisulfide, DATS) serves as a quality marker for garlic and garlic products due to its anticancer and antibacterial properties. Although surface-enhanced Raman scattering (SERS) has garnered significant attention, the small Raman scattering cross-section of molecules like H2S and DATS makes direct detection challenging. We present a novel method using thickness-tunable Ag@Ag2S core-shell plasmonic arrays at the liquid-liquid interface (LLI). The H2S-concentration-dependent Ag2S shell thickness effectively regulates the size of NP, the number of Raman reporter molecules, and the interparticle spacing, resulting in major changes in reflectance and SERS. The low detection limits (151 ± 0.96 pM for H2S and 6.6 ± 0.53 nM for DATS) and the high recovery (93.3%-111.0%) obtained from actual water samples indicate the potential for practical application, offering a new solution for detecting trace H2S and related compounds.