Thermally-Driven Nanoparticle Array Growth from Atomic Au Precursor Solutions

We observe spontaneous formation of hexagonal and square arrays of sub-10-nm Au nanoparticles by asymmetric heating of a novel precursor material, alkanethiol-passivated atomic Au cluster solutions, on amorphous carbon films. Nanoparticle shape, array symmetry, and lattice constant are controlled by substrate temperature and solvent composition. It is shown that definition of the array lattice points precedes complete particle formation, ruling out an entropy-driven “hard sphere”-type self-assembly process. Mechanisms for monolayer array formation are discussed.