Solvatochromism of a silver-epoxy nanocomposite dispersed in organic solvents

Abstract

Fresh and aged silver-epoxy nanocomposites were dispersed in aprotic solvents having different dielectric constants (ε) like Acetone (Ace), N, N-dimethylformamide (DMF), and dimethylsulphoxide (DMSO). Different colors and hues of the dispersions depending on the dielectric constant of the solvents were observed, suggesting a solvatochromic behavior. Aggregated and isolated triangular silver nanoprisms with sharp corners were predominant for fresh and aged dispersions in Acetone (ε = 21.0), respectively. Whereas, aggregated and isolated truncated triangular silver nanoprisms were observed for the ones in DMF (ε = 36.7), respectively. Stacks of elongated silver nanoparticles (Nps) predominated for both fresh and aged dispersions prepared in DMSO (ε = 47.2). It was found that as the dielectric constant of the solvents increases the average size of the Nps diminishes and the silver nanoprisms were transformed into elongated shapes, for both fresh and aged samples. These morphologies have an important impact on the position and shape of the plasmonic resonance. The dipolar optical extinction maximum of the silver Nps of aged samples was linearly red-shifted with an increase in the dielectric constant of the solvents. On the other hand, it was observed higher stability for silver Nps dispersed in DMSO and DMF compared with Ace in both fresh and aged samples. The results show the influence of the solvent dielectric constant on the optical properties, size distribution, morphology, and stability of the silver Nps. A solvatochromic mechanism of the silver Nps based on the coalescence of small silver seed Nps (< 40 nm) is proposed.