Ultra-small silver nanoparticles as advanced materials: from synthesis to properties and applications

Abstract

Ultra-small silver nanoparticles (NPs), typically described as Ag nanoclusters (NCs), are defined as isolated Ag particles less than 2 nm in size with up to a hundred Ag atoms. Particles in this sub-2 nm size regime display discrete and size-tunable electronic transitions owing to their strong quantum confinement effects, which lead to interesting molecule-like properties such as strong luminescence. In the past few years, luminescent metal NCs have emerged as a new class of promising optical probes for biomedical and environmental applications due to their ultrafine size, excellent photostability, and low toxicity. Currently, the synthesis and applications of Au NCs have been extensively explored in the cluster community. However, the same expansion does not occur in the Ag field possibly due to its susceptibility to oxidation, although it is well-known that Ag is featuring with intriguing physicochemical properties, relative abundance, and low cost. In this thesis, two simple, scalable, and generalized strategies, based on mild etching kinetics via delicately playing with cluster chemistry, are developed for the synthesis of highly luminescent Ag NCs. In addition, several application explorations, including environmental monitoring, biomolecular recognition, and antimicrobial agent development, have been successfully demonstrated by using the as-synthesized luminescent Ag NCs.