Insights into the Synthesis Mechanism of Ag 29 Nanoclusters.

The current understanding of the synthesis mechanisms of noble metal clusters is limited, in particular for Ag clusters. Here, we present a detailed investigation into the synthesis process of atomically monodisperse Ag-29 clusters, prepared via reduction of AgNO3 in the presence of dithiolate ligands. Using optical spectroscopy, mass spectrometry, and X-ray spectroscopy, it was determined that the synthesis involves a rapid nucleation and growth to species with up to a few hundred Ag atoms. From these larger species, Ag-29 clusters are formed and their concentration increases steadily over time. Oxygen plays an important role in the etching of large particles to Ag-29. No other stable Ag cluster species are observed at any point during the synthesis.