Carbon graphite surfaces modified with two-dimensional arrays of N-acetyltripeptide-protected gold nanoparticles

We obtain carbon graphite surfaces modified with two-dimensional (2D) arrays of N-acetylglutathione-protected gold nanoparticles by simple immersion of highly oriented pyrolytic graphite (HOPG) in aqueous acidic solution containing the gold nanoparticles. The mean core diameter of the gold nanoparticles immobilized on HOPG is about 6 nm, whereas that of the as-prepared sample is about 1 nm. A combined study with scanning electron microscopy (SEM) and scanning tunneling microscopy (STM) reveals that small gold nanoparticles with their diameter of 1-2 nm never adsorb onto the HOPG surface. Simple quantum chemical calculations suggest marginal importance of the protective ligand-graphite interaction, yielding that the gold core-graphite van der Waals attractive interaction plays a major role toward the spontaneous 2D assembly of the nanoparticles. We believe this approach has great potential to improve biofunctional or electrocatalytic activities of carbon materials.