We have employed scanning tunnelling microscopy (STM) in ultra-high vacuum (UHV) to explore the assembly and electron transport properties of an ordered layer of passivated gold clusters adsorbed onto an alkanethiol passivated Au(111) surface. The passivation of the Au(111) surface stabilises the cluster layer. STM images show ordered hexagonal arrays of the nanoparticles extending over distances >100 nm with a mean nearest neighbour spacing of 6.5 nm. I-V measurements show a strong non-linear I-V relationship, as well as equidistant steps of width similar to0.15 V above a bias voltage of similar to2 V, attributed to a Coulomb staircase, i.e., single electron charging, in this structure.