Highly Sensitive Electro-Plasmonic Switches Based on Fivefold Stellate Polyhedral Gold Nanoparticles.

Electron-photon coupling in metal nanostructures has raised a new trend for active plasmonic switch devices in both fundamental understanding and technological applications. However, low sensitivity switches with an on/off ratio less than 5 have restricted applications. In this work, an electrically modulated plasmonic switch based on a surface-enhanced Raman spectroscopy (SERS) system with a single fivefold stellate polyhedral gold nanoparticle (FSPAuNP) is reported. The reversible switch of the SERS signal shows high sensitivity with an on/off ratio larger than 30. Such a high on/off ratio arises primarily from the plasmonic resonance shift of the FSPAuNP with the incident laser due to the altered free electron density on the nanoparticle under an applied electrochemical potential. This highly sensitive electro-plasmonic switch may enable further development of plasmonic devices.