Evolution Analysis of Silver Nanoparticles Synthesised by Lactam Reduction: A Case Study of ϵ-Caprolactam

Abstract

Without using protecting agent and solvent, silver nanoparticles (Ag NPs) were synthesised by using lactams as reducing agents. Being the most commercially available lactam, ϵ-caprolactam (CL) was taken as a model to illustrate the evolution of Ag NPs in the medium of lactams. The results showed that there were two different stages involved in the Ag NP evolution process. In the first stage, particles were stabilised against further coalescence at a smaller size (< 5 nm) because of face-bound CL. In the second stage, the Ostwald ripening mechanism cooperated with continuous reduction of residual silver ions, which resulted in the resultant particles being distributed with different size distribution. The participation of CL in the reducing and protecting procedures raised a complex evolution of Ag NPs.