Quasi-linear assemblies of silver nanoparticles by highly localized anodic dissolution of copper in the hydrosol

The assembly of silver nanoparticles into quasi-linear superstructures in solution has been demonstrated. A small dc voltage applied to fine-tipped, L-shaped copper electrodes immersed in aqueous carboxylic acid-derivatized silver nanoparticle solution leads to the anodic dissolution of copper ions. The controlled release of Cu ²⁺ ions within the gaps results in local screening of repulsive coulombic interactions between the silver nanoparticles and the consequent formation of aggregates that are extremely stable in time. Atomic force and transmission electron microscopy images of the silver nanoparticle solution after application of an electric field showed the presence of a large number of silver nanoparticle assemblies in open, quasi-linear structures. Such open structures do not form if Cu ²⁺ ions are added directly to the silver nanoparticle solution.