Electrochemical tuning Localized Surface Plasmon Resonance of Au-Ag core-shell nanoparticle for Surface-Enhanced Raman Scattering*

Active control of the localized surface plasmon in metallic nanoparticles is of fundamental importance for surface-enhanced Raman spectroscopy (SERS) application. By oxidation-reduction chemistry of Ag-AgCl shells or clusters on the surfaces of AuNP, we induced dielectric-conductive shell or clusters between AuNP and GME. Self-assembled monolayer modified on GME experienced different electromagnetic field produced by surface plasmon of Ag/AuNP or AgCl/AuNP, thus, induced extreme but reversible changes in SERS intensity. Meanwhile, the redox process of Ag-AgCl is confirmed by time-resolved electrochemical current (i-t). Simultaneously SERS and i-t measurement on Ag/AuNP-on-GME show our ability to manipulate the morphology of narrow inter AuNP-GME gaps. With the assistant of Ag shell or cluster on AuNP-on-GME, Raman enhancements can be tuned much more dramatically by electrochemical bias.