Double-sided structural color of Fe sub(3)O sub(4)iO sub(2) nanoparticles under the electric field

The double-sided structural color of Fe sub(3)O sub(4)iO sub(2) NPs under external electric field was found. Corresponding colloidal suspension of Fe sub(3)O sub(4)iO sub(2) showed a highly adjustable structure color change on both sides of the display cell with the applying of electric fields. As the applied voltage increased, the color changed from red to green then to blue at positive plate, at the same time, the color changed from red to gray then to red at the negative plate. Under a certain electric field, the reflection peak move backwards within a particular range of wavelength. It may be caused by the emergence of another repulsive force-"solvation force" at small interparticle distances.