On the use of Au@Ag core-shell nanorods for SERS detection of Thiram diluted solutions.

Rod-shaped gold-silver core-shells (AuNR@Ag) were synthesized for an analysis of the amplification of Raman scattering (surface-enhanced Raman scattering, SERS). The microscopy characterization confirmed a hierarchically structured nanoparticle with well-defined size and morphology, however, with a degree of dispersion in terms of shell thickness and symmetry of Ag deposition. In this paper, we analyze the possible effects of such structural dispersion in the SERS spectra of 4-aminobenzothiol (4-ABT) and in its detection at low concentrations in solutions. The interpretation of experimental results was supported by classical electrodynamics simulations based on the boundary element method (BEM). We verified that even in the case of asymmetrical Ag deposition onto AuNRs, a large SERS normal may be observed, which leads to the possibility of using such nanostructures for SERS applications aiming at low analyte concentrations detections. We show that the SERS substrates based on such AuNR@Ag present very high sensitivity for the detection of ultra-low concentrations of 4-ABT reaching a detection limit of 1.10 mol L, which indicates the possibility of analytical applications in the detection of analytes such as pesticides.