Bimetallic Core@Shell Au@Ag nanoparticles as SERS substrates for dexamethasone detection

The detection of dexamethasone (DEX) at low concentrations requires sensitive analytical methods. In this study, CTAC-functionalized Au, Ag, and bimetallic Core@Shell Au@Ag nanoparticles were evaluated as substrates for surface-enhanced Raman spectroscopy (SERS), allowing a comparative assessment of their performance in DEX detection. Au-NPs and Ag-NPs exhibited quasi-spherical morphologies, with average diameters of 26.3 ± 3.3 nm and 39.7 ± 10.2 nm, respectively, whereas Au@Ag-NPs exhibited a Core@Shell structure consisting of a quasi-spherical Au core and a cubic Ag shell with an average edge length of 58.5 ± 4.8 nm. UV–Vis spectroscopy revealed characteristic plasmonic responses, while zeta potential measurements showed positively charged nanoparticle surfaces consistent with CTAC functionalization. Conventional Raman spectroscopy did not reveal detectable DEX bands under the experimental conditions employed. In contrast, SERS measurements showed characteristic DEX bands, with the most prominent signal located at approximately 1698 cm -1 . Au-NPs enabled DEX detection at millimolar concentrations, while Ag-NPs exhibited detectable signals down to 1 µM. Notably, Au@Ag-NPs allowed the identification of DEX at 1 nM, the lowest concentration evaluated in this study. These results demonstrate the superior low-concentration detection capability of Au@Ag-NPs under the investigated conditions and highlight the potential of bimetallic Core@Shell nanoparticles as SERS substrates for label-free DEX detection