Solvent-Induced Charge Formation and Electrophoretic Deposition of Colloidal Iron Oxide Nanoparticles

Abstract Among the various solution processes that utilize colloidal NPs, electrophoretic deposition (EPD) has recently emerged as an efficient technique for the fabrication of dense and robust NP films. However, the interaction between colloidal NPs and the organic solvent in EPD systems has not been fully investigated. In this study, we investigate the charge formation role of the solvent in EPD systems using hexane, toluene, and chloroform with different ratios of the solvents (10:0, 7:3, 5:5, 3:7, and 0:10). As the ratio of toluene to hexane in the solvent increases, the NP film becomes thicker and rougher. In contrast, increasing the ratio of chloroform to hexane significantly reduces the film thickness. A zeta potential is measured to determine the influence of the solvent on the EPD process. The zeta potential distribution of the NPs dispersed in toluene is broader than that of the NPs in chloroform, suggesting that the solvent might control the surface charge and influence the film thickness. These results indicate that the choice of the solvent can be a key factor in determining the morphology and processability of NP films fabricated via EPD.