Using Voronoi Tessellations to Assess Nanoparticle-Nanoparticle Interactions and Ordering in Monolayer Films Formed through Electrophoretic Deposition

Monolayers of iron oxide nanoparticles of two 50 different sizes, 9.6 nm and 16.5 nm, were fabricated through electrophoretic deposition. The arrangements of nanoparticles within the films were analyzed using the technique of Voronoi tessellations. These analyses indicated that the films possessed equivalent degrees of ordering, and that the films were uniform over centimeter length scales. Precise measurements of the interparticle spacing were obtained, and the magnitudes of magnetic dipole interactions were calculated. The dipole-dipole interaction among the larger nanoparticles was 14 times larger than that of the smaller nanoparticles, indicating that magnetic coupling interactions could not have been the lone source of ordering in the system.