Electronic structure of ensembles of gold nanoparticles: Size and proximity effects

The valence-band electronic structure of alkanethiol stabilized gold nanoparticles (NPs) with different core sizes has been studied using x-ray photoemission spectroscopy. A reduction of density of state near the Fermi level is observed for small particles (< 3 nm diam) that are separated by more than 1 nm. A significant cross-coupling between the particles is found when their separation is decreased below 1 nm that restores the density of states at the Fermi edge. The observations are interpreted as a result of changes in the screening of Coulomb blockade effects in the NP system due to tunneling between particles at the shorter separations.