Gold nanoparticle superlattices self-assembled at a solid/liquid interface

Abstract

Three-dimensional superlattices of gold nanoparticles were self-assembled at a highly oriented pyrolytic graphite (HOPG)/water interface under a strongly acidic condition. The surface of the gold nanoparticles is protected by mercaptosuccinic acid (MSA). The small angle X-ray diffraction (SAXD) pattern proved the presence of a large unit cell due to superlattice formation. The faceted morphology of the superlattices studied by scanning electron microscopy (SEM) was another indication of their crystalline nature. Scanning tunneling microscopy (STM) was used to investigate the surface image of the superlattices, demonstrating a well-ordered hexagonal arrangement of nanoparticles. Geometrical optimization using PM3 molecular orbital calculations suggested that CH/π interactions between the protonated form of MSA and HOPG surface would contribute to the initial-stage adsorption of the nanoparticles.