Femtosecond dynamic final-state effect in photoemission of surface-passivated metallic nanoparticles on graphite substrates

We have carried out systematic photoemission studies of alkanethiolate- (AT-)passivated metallic (Ag and Au) nanoparticles supported on the highly oriented pyrolytic graphite (HOPG) substrates. The Fermi-level onsets in the photoemission spectra of AT-passivated Ag nanoparticles on the HOPG substrates are not the metallic Fermi-edge, and depend on the nanoparticle diameter and surface-passivant molecules. Furthermore, the core-level photoemission spectra also depend on the nanoparticle diameter.We attribute these unusual spectral features to the dynamic final-state effect in photoemission, indicative of the interaction between the nanoparticle and substrate through the surface-passivants on a femtosecond timescale