Passivant dependence of nanoparticle-substrate interactions of alkanethiolate-passivated au nanoparticles on graphite substrates

We have carried out the photoemission study of monodisperse Au nanoparticles passivated with the various alkanethiolate on the highly oriented pyrolytic graphite (HOPG) substrate. The photoemission spectra in the vicinity of the Fermi level of alkanethiolate-passivated Au nanoparticles on the HOPG substrates are not the metallic Fermi edge. The steep slopes of Fermi level onsets move away from the Fermi level and depend on the surface-passivant molecules. We have analyzed the obtained spectra with the dynamic final state effect model that takes into account the Coulomb interaction between the photoelectron and photohole with a finite lifetime during the photoemission process. The calculated results based on the dynamic final state effect model reproduce the experimental ones fairly well. Furthermore, it is found that the photohole lifetime depends on the molecular length of surface-passivant. We attribute the passivant dependence of photoemission spectra to the surface-passivant dependent nanoparticle-substrate interaction.