Shape transformation from silver triangular nanoprisms to nanodisks: Raman characterization and sculpturing mechanism

Abstract

The sculpturing action of chloride ions on silver nanoplates is investigated. Recent reports show that the shape transformation from silver triangular nanoprisms to nanodisks by addition of chloride ion occurs after a threshold concentration. In this work, a chemical study of this threshold concentration is presented. There is theoretical and experimental evidence that the morphological change only depends on the chloride ion concentration and not on the Cl$^{-}$/Ag molar ratio. Besides, the chloride ion etching ability is attributed to the (AgCl)$^{\circ}$ complex, which controls the morphology change through a stepwise process where a silver atom is removed from the (110) plane, and is subsequently deposited on the (111) plane (i.e. from the nanoplate vertex to the basal plane). The threshold chloride ion concentration in the shape transformation coincides with the point where Ag$^{+}$ ion and (AgCl)$^{\circ}$ concentrations are the same. On the other hand, the quantitative formation of AgCl$_2^{-}$ avoids the stepwise process, and then the colloidal system is destabilized. Furthermore, the analysis of the Raman spectra supports the transformation mechanisms.