Wet Chemical Synthesis of Monodisperse Colloidal Silver Nanocrystals Using Digestive Ripening

Silver metal nanocrystals with passivating ligand shells of dodecanethiol were synthesized by a one-phase wet chemical method. Postsynthesis thermochemical processing, known as digestive ripening, was used to focus the size distribution from a very broad distribution to 5.6 ± 0.4 nm. Chemical analysis of the final Ag nanocrystals showed a metallic core with a densely packed ligand shell. No oxidation was observed despite the entirely aerobic conditions. The size distribution was found to change most dramatically after the two steps proceeding digestive ripening, namely, ligand exchange and precipitation. Imaging also showed that the digestive ripening mechanism of Ag nanocrystals could be significantly different than that for Au, and involved a competitive silver thiolate side product. This synthesis was optimized to produce Ag nanocrystals with little to no silver thiolate materials.