Studying and Controlling Order Within Nanoparticle Monolayers Fabricated Through Electrophoretic Deposition

Electrophoretic deposition (EPD) is introduced in a new light: as a process for the fabrication nanoparticle monolayers (NPMs).Using EPD, NPMs are fabricated from a variety of different types of NPs such as iron oxide, cobalt ferrite, TiO2, indium tin oxide, and more, and these NPMs display local order between NPs As order between NPs within an array has been shown to affect the properties of said array, the mechanisms that generate order are investigated. Order within two systems is studied, one incorporating superparamagnetic iron oxide NPs and the other incorporating ferromagnetic cobalt ferrite NPs. In the iron oxide NPMs, magnetic dipole interactions are shown to have little effect on the order within the NPM. We observe that the order within the iron oxide NPM is generated during the drying of the film after NPs have deposited. From this it is inferred that capillary forces likely generate order. Within the cobalt ferrite NPMs, the magnetic easy axes of the NPs are observed to align, indicating that magnetic interactions likely generate order.