Cyclic electroplating and stripping of silver on Au@SiO₂ core/shell nanoparticles for sensitive and recyclable substrate of surface-enhanced Raman scattering

A simple and convenient methodology to fabricate silver-coated Au@SiO₂ core/shell nanomaterials (Au@SiO₂@Ag nanostructures) is developed by cyclic electroplating and stripping of AgNO₃ on the surface of Au@SiO₂ core/shell nanoparticles, and the proposed nanostructures served as sensitive and reproducible surface-enhanced Raman scattering (SERS) substrates. Silver coverage of nanostructured Au@SiO₂@Ag could be easily controlled by electrodeposition time without substrate motion. The Au@SiO₂@Ag nanostructures possess a hexagonal array multiplying the hot spots. SERS of the nanostructures was examined at different electrodeposition times using rhodamine B (RdB) as probe molecule and 785 nm excitation. Optimum SERS was observed when silver was electrodeposited at -0.4 V for 1 min. RdB can be detected down to 10^-11 M even without the resonance SERS effect, and the enhancement factor was found at 1.03 × 10⁵. Additionally, silver shells could be easily stripped electrochemically when immersed in the H₂SO₄ solution for rebuilding and recycling the SERS substrates. The results validate the feasibility for quantitative detection of biomolecules in organisms and combine the advantages of recyclability and sensitivity.