G. Di Martino,V. A. Turek,  A. Lombardi, I.  Szabó, B. de Nijs,  A. Kuhn, E. Rosta, J.J. Baumberg

Nano Lett. 2017, 17, 4840-4845

We study in real time the optical response of individual plasmonic nanoparticles on a mirror, utilised as electrodes in an electrochemical cell when a voltage is applied. In this geometry, Au nanoparticles are separated from a bulk Au film by an ultrathin molecular spacer. The nanoscale plasmonic hotspot underneath the nanoparticles locally reveals the modified charge on the Au surface and changes in the polarizability of the molecular spacer. Dark field and Raman spectroscopy performed on the same nanoparticle, show our ability to exploit isolated plasmonic junctions to track the dynamics of nano-electrochemistry. Enhancements in Raman emission and blue-shifts at negative potential show the ability to shift electrons within the gap molecules.

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