Assembly of Gold Nanostar Cores Within Silica Shells and Its Impact on Solid-State SERS and Nonenzymatic Catalytic...

Metal core and dielectric shell nanoparticles (NPs) have garnered considerable attention for their multifaceted properties and extensive applications across diverse fields of nanoscience and nanotechnology. However, a literature gap exists regarding the impact of assembled metallic nanostar cores within a single shell, particularly concerning surface-enhanced Raman scattering (SERS) and electrochemical sensing. In this study, we have demonstrated the better performance of assemblies of gold nanostars (AuNSs) enclosed in single silica shell for SERS enhancement and electrocatalytic activity, particularly in the fields of ascorbic acid (AA) and glucose sensing. We have devised a method to isolate and passivate nanostar assemblies, ranging from 2 to 30 nanostars per assembly, with a functionalized silica (SiO₂) shell, facilitating their preservation. The engineered thickness of the silica shell ensures unhindered optical measurements while elucidating the influence of multiple AuNS cores. Due to the formation of nanogaps and nanojunctions between AuNSs within assembly, we have achieved a maximum SERS enhancement factor (EF) of 1.416 × 10¹⁰ for the rhodamine 6G analyte. Utilizing assembled AuNS cores within a single silica shell, we have demonstrated AA (sensitivity of 5.278 × 10^-5 μA μM^-1 cm^-2) and glucose (sensitivity of 7.519 × 10^-4 μA μM^-1 cm^-2) sensing via a nonenzymatic electrochemical pathway.