Mass Spectrometry and Dynamics of Gold Adatoms Observed on the Surface of Size-Selected Au Nanoclusters

We report the imaging, mass spectrum, and dynamical behavior of adatoms and small clusters observed on the surface facets of size-selected, truncated octahedral gold clusters, Au-N (N = 923 +/- 23), via aberration-corrected scanning transmission electron microscopy. Our quantitative atom counting measurements show that most (similar to 70%) of the species on the surface are single Au adatoms. Such species are now proposed as key elements of the atomic structure of both monolayer-protected nanoclusters (nanoparticles) and self-assembled monolayers and may also play a role in gold nanocatalysis. The adatoms are found on both {100} and {110 facets with similar probabilities.