Synthesis of Gold Nanorod@AuAg Hollow Shell Nanostructures with Enhanced Refractive Index Sensitivity and SERS Activity

Hollow core‐shell noble metallic nanoparticles have garnered significant attention due to their plasmonic properties, which are markedly enhanced by the hollow structure. However, precisely controlling the size and shape of the shell and cavity in such structures remains a challenge. Here, a novel strategy is reported that eliminates the need for etchants, utilizing monodispersed gold nanorods (AuNRs) as templates to synthesize hollow Au@AuAg core‐shell nanostructures. By precisely regulating the CTAB/CTAC and Au/Ag ratios during the co‐deposition of Au and Ag atoms onto the AuNRs, uniform bimetallic hollow shells are achieved without the use of corrosive etching agents. High‐resolution TEM and EDS characterizations confirm the formation of crystalline AuAg alloy shells surrounding the AuNRs cores, with well‐defined cavities. Compared to pure silver shells, the AuAg alloy shells exhibit superior stability. Furthermore, the resulting Au@AuAg nanostructures with hollow shells demonstrate significantly enhanced refractive index sensitivity and surface‐enhanced Raman scattering (SERS) activity relative to pristine AuNRs, making them highly promising for biomedical applications such as biosensing and bioimaging.