This work demonstrates the ability of plasmons to switch on the fluorescence of molecular monolayers through a hole injection process, in combination with an electrochemical reduction triggered at the tip and transferred to the monolayer by a redox mediator.

Abstract

A dual and simultaneous modulation of fluorescence intensity and electrochemical current induced by plasmon activation is demonstrated using a combination of electrochemical (SECM) and fluorescence microscopies, employing fluorescent redox monolayers grafted onto gold nanoparticles. The observed electrochemical and optical responses are fully consistent with a direct hole injection from the plasmonically excited metallic nanoparticles into the grafted monolayer. In particular, an unprecedented fluorescence intensity enhancement occurs upon simultaneous electroreduction at the tip and plasmon activation, whereas each process taken separately leads to a fluorescence quenching. The electrochemical current enhancement is significantly larger for functionalized nanoparticles compared to bare ones under plasmon activation, opening the route toward new strategies in photoelectrocatalysis.