Effective Electrochemical Modulation of SERS Intensity Assisted by Core-Shell Nanoparticles

An effective and reversible tuning of the intensity of surface-enhanced Raman scattering (SERS) of nonelectroactive molecules at nonresonance conditions by electrochemical means has been developed on plasmonic molecular nanojunctions formed between Au@Ag core-shell nanoparticles (NPs) and a gold nanoelectrode (AuNE) modified with a self-assembled monolayer. The Au@ Ag nanoparticle on nanoelectrode (NPoNE) structures are formed in situ by the electrochemical deposition of Ag on AuNPs adsorbed on the AuNE and can be monitored by both the electrochemical current and SERS signals. Instead of introducing molecular changes by the applied electrode potential, the highly effective SERS intensity tuning was achieved by the chemical composition transformation of the ultrathin Ag shell from metallic Ag to insulating AgCl. The electrode potential-induced electromagnetic enhancement (EME) tuning in the Au@Ag NPoNE structure has been confirmed by finite-difference time-domain simulations. Moreover, the specific Raman band associated with Ag-molecule interaction can also be tuned by the electrode potential. Therefore, we demonstrated that the electrode potential could effectively and reversibly modulate both EME and chemical enhancement in Au@Ag NPoNE structures.

Automated summary

An effective method has been developed to tune the intensity of surface-enhanced Raman scattering (SERS) of non-electroactive molecules by electrochemical means, involving the formation of nanostructures between Au@Ag core-shell nanoparticles and a gold nanoelectrode. The tuning is achieved by transforming the chemical composition of the thin Ag shell from metallic Ag to insulating AgCl, instead of introducing molecular changes by the electrode potential. The electrode potential can also tune the electromagnetic enhancement (EME) and specific Raman bands associated with Ag-molecule interaction in the Au@Ag nanostructures.