Large-scale preparation of size-controlled Fe3O4@SiO2 particles for electrophoretic display with non-iridescent structural colors

Monodisperse colloidal particles have promising applications in electrophoretic displays with vivid colors, reversibility and low switching times. In this study, a facile, effective and large-scale strategy for preparing size-controlled Fe3O4@SiO2 particles is reported. Multiple Fe3O4 particles were synthesized by a modified solvothermal method using sodium citrate as a surface modifier with a binary solvent, and were then coated with a SiO2 layer to obtain a highly negatively charged surface via a modified Stöber method. Owing to the easily controlled sizes and sufficient surface charges, Fe3O4@SiO2 particles can be assembled into colloidal amorphous arrays with the balance of electrostatic repulsion and electrophoretic forces. The reflections cover wavelengths ranging from 802 to 453 nm, and were optimized by investigating the dependence of the particles on variables such as particle size, particle volume fraction, and electric field intensity. The large-scale preparation of electrically responsive Fe3O4@SiO2 particles facilitates an electrophoretic display with broad-range colors, showing the practical potential in industrial application.