Direct Visualization of Plasmon- Induced Hole Injection in Electroactive Luminescent Monolayers on Gold Nanoparticles

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.