Dynamic final-state effect on the Au 4f core-level photoemission of dodecanethiolate-passivated Au nanoparticles on graphite substrates

We have carried out a photoemission study using synchrotron radiation of dodecanethiolate- (DT-) passivated Au nanoparticles supported on the highly oriented pyrolytic graphite (HOPG) substrates. From the detailed line-shape analyses, it is found that Au 4f core-level photoemission spectra of DT-passivated Au nanoparticles on the HOPG substrates consist of the two components, which originate from the inner Au atoms of Au nanoparticles and surface Au atoms bonded to surface passivants of DT molecules. Furthermore, it is found that Au 4f core-level spectra shift to higher binding energy with decreasing the nanoparticle diameter. We attribute these energy shifts to the dynamic final-state effect on the Au 4f core-level photoemission due to the positive charge with a finite lifetime left behind in the nanoparticles in the photoemission final state.