Surface-Passivant Dependence of Dynamic Charging Effect in Alkanethiolate-Passivated Au Nanoparticles on Graphite Substrates Studied by Photoelectron Spectroscopy

We have performed a photoemission study of various alkanethiolate- (AT-) passivated Au nanoparticles with diameter of 4 nm on the highly oriented pyrolytic graphite (HOPG) substrates. It is found that the photoemission spectra in the vicinity of Fermi level of all the present AT-passivated Au nanoparticles on the HOPG substrates do not exhibit the usual metallic Fermi edge, with the steep slope being away from the Fermi level. Moreover, it is found that these spectral features depend on the surface-passivant molecules. We attribute the unusual spectral features in the vicinity of Fermi level to the dynamic charging effect in photoemission final-state, indicative of the interaction between the nanoparticle and substrate through the surface-passivants on a femtosecond time scale.