From Nanoparticles to Nanoplates: Preferential Oriented Connection of Ag Colloids during Electrophoretic Deposition

The Ag nanostructured films are fabricated based on electrophoretic deposition (EPD) in the Ag colloidal solution produced by laser ablation in water, under a constant current deposition mode. It has been found that the obtained films are of tunable and controllable morphologies and structures depending on EPD parameters. Importantly, there exists significant crystal growth for the building blocks of the film during EPD, in addition to normal particles' coagulation. With increasing the current density of EPD, the size of the building blocks in the film decreases, and the shape evolves from polyhedral particles to regular nanoplates, and to irregular equi-axial particles. Correspondingly, the film structure changes from discontinuous film, consisting of the isolated aggregates of the building blocks, to the homogeneous and dense film, consisting of equi-axial particles. Further experiments have revealed that formation of the regularly shaped single crystal building blocks is attributed to the crystal growth induced by the oriented connection of the nanoparticles, with fresh surface, in the colloidal solution and/or on the substrate during EPD. This study not only provides a new method to control and tune the morphology and structure of films in a simple way, but also deepens the understanding of the physical mechanism of EPD.