High-Resolution Analysis of Small Silver Clusters by Analytical Ultracentrifugation.

Although silver particles are used in various applications and a countless amount of synthesis routes exist, their formation mechanism is still poorly understood. Especially the first species formed directly after nucleation challenge analysis methods with their small size and transient nature. Analytical ultracentrifugation (AUC) has already proven to provide high size resolution and therefore enables the characterization of early nucleation species. Herein, we present an experiment of multiwavelength (MWL)-AUC of silver clusters, which revealed seven different cluster species. They consist of less than ten atoms and therefore represent the first species formed after nucleation. Using MWL-AUC, UV/Vis spectra could be allocated to each of them, which is shown for the first time. These findings can contribute to develop a nucleation mechanism for silver nanoparticles.