Measuring the energy of plasmonic hot-holes by single particle electrochemistry

GARGIULO, JULIÁN; PENSA, EVANGELINA; LAURI, ALBERTO; SCHLÜCKER, SEBASTIAN; CORTÉS, EMILIANO; MAIER, STEFAN A.

Copenahue

Conferencia; Surface Plasmon Photonics 9; 2019

Plasmonic hot carriers have been recently identified as key elements for photocatalysis at visible wavelengths. The possibility to transfer energy between metal plasmonic nanoparticles (NP) and nearby molecules depends not only on carrier generation and collection efficiencies but also on their energy at the metal-molecule interface. The initial carrier energy can be as high as the energy of the absorbed photon exciting the plasmon. However, the effective energy of the carrier at the metal-molecule interface can be significantly lower than the theoretical maximum, because transport and injection of the carrier can significantly damp its energy. Here, we performed a screening of the energy that plasmonic hot-holes can provide to a nearby molecule. We monitored an aniline electro-polymerization reaction catalysed by an illuminated 80 nm gold NP. The formation of polyaniline is monitored optically through changes in the scattering spectra of the single AuNP. Our results show that exciting the AuNP at its plasmon resonance reduces up to 0.24 eV the energy required to start the polymerization reaction. In order to understand the mechanism behind this photocatalytic effect and disentangle thermal from hot-carrier effects, the reactivity of illuminated particles was studied at different wavelengths and constant temperature. It was found that even if the absorbed energy at each excitation wavelength is the same, the reactivity of the hot-holes follows the plasmon resonance profile. This work highlights the role of plasmon excitation in photocatalysis besides other absorption mechanisms and demonstrate a method to measure the carrier?s effective extracted energy.