Etching coupled with secondary deposition weakening the Raman enhancement of Ag coated Au nanobipyramids and its application in SERS detection of S2−

Silver coated gold nanobipyramids (Au NBPs@Ag) have opened up a wide range of applications in sensing based on the etching, due to the fact that a tiny change in shape or composition could directly lead to optical changes. Here, we developed an ultrasensitive surface-enhanced Raman scattering (SERS) method for S 2− sensing by using Au NBPs@Ag as nanoprobes. This strategy was revealed to be related to the redox reaction between S 2− and the silver nanoshell of the Au NBPs@Ag. The silver nanoshell was gradually etched as the S 2− concentration was gradually increased. Meanwhile, the generated Ag 2 S was secondary deposited on the surface of etched Au NBPs@Ag. Thus, the etching of silver shell and secondary deposition of Ag 2 S induced SERS decrease of the nanoprobes, which was not only highly selective toward S 2− but also showed a linear logarithmic dependence on S 2− concentrations from 10 −5 to 10 −8  M, with a limit of detection (LOD) of 4.7 × 10 −8  mol/L. Spike recovery tests in tap water demonstrated recoveries of 104.00%, 98.86%, and 105.32% with relative standard deviations (RSD) between 2.52% and 3.98%, validating high accuracy for S 2− detection. This approach provided a novel SERS strategy for trace sulfide monitoring in drinking water systems.