Synthesis of Ag clusters in microemulsions: A time-resolved UV–vis and fluorescence spectroscopy study

The combined use of the microemulsion technique and the kinetic control allows the preparation of small silver clusters. By using UV–vis and fluorescence spectroscopy the main stages by which the clusters grow, before the formation of nanoparticles, were elucidated. Transmission electron microscopy (TEM) and scanning tunnelling microscopy (STM) were used to further characterize the samples. Two main stages were clearly identified, which are associated with: (1) the formation of Agn clusters with n<10, which self-aggregate into one atom high 2D nanodiscs of 3.2 nm size and (2) Agn clusters, which self-aggregate into 3D nanostructures of 1.5 nm in size. The fluorescence properties observed with both stages show that the formed clusters are small enough to display a molecule-like behaviour.