Preparation of concentrated stabilizer-free dispersions of uniform silver nanoparticles

Abstract

Stable concentrated aqueous dispersions of uniform 10 nm silver nanoparticles were prepared in absence of colloid stabilizers by reducing silver nitrate with phloroglucinol at room temperature and elevated pH. The key feature of the precipitation process entails triggering suddenly the electrons transfer between the reacting species coexisting in a homogeneous solution (‘latent reaction mixture’). The ensuing silver nucleation occurs rapidly and uniformly in the entire reaction volume leading to the formation of highly uniform dispersed nanoparticles. The phloroglucinol oxidation byproducts play an important role in preventing the aggregation of nanoparticles and facilitating the preparation of highly stable dispersions containing up to 62 wt% Ag (5.7 mol.dm−3). A mechanism rationalizing the long-term stability of silver sols at such high metal content is proposed. The rheological properties of concentrated dispersions permit the inkjet printing of electrically conductive patterns suitable for incorporation in sensors, RFID tags, solar cells, displays, and other electronic devices.