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 x 10(5). 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.