Seeing Is Believing: How Does the Surface of Silver Nanocubes Change during Their Growth in an Aqueous System

The seed-mediated growth involving cetyltrimethylammonium chloride (CTAC), silver trifluoroacetate (CF3COOAg), ascorbic acid (H2Asc), and Ag seeds covered by poly(vinylpyrrolidone) (PVP) in aqueous medium is a robust route to Ag nanocubes with tunable sizes. However, mechanistic details such as changes to the surface remain elusive. Herein, we address this issue by leveraging the high sensitivity and water compatibility of surface-enhanced Raman scattering (SERS). Our results reveal that the addition of CTAC results in ligand exchange between PVP and chloride and the further introduction of CF3COOAg leads to the deposition of AgCl on Ag seeds. The H2Asc subsequently introduced increases the electron density on the surface of the seeds due to electron transfer, as manifested by rapid and pronounced enhancement of the SERS signals from AgCl and CTA+. The electrons from H2Asc also enable reduction to directly transform AgCl in contact with Ag into Ag atoms and enlarge the seeds into nanocubes.