Stimuli-responsive magneto-/electro-chromatic color-tunable hydrophobic surface modified Fe 3 O 4 @SiO 2 core–shell nanoparticles for reflective display approaches

In order to provide stimuli-responsive properties under magnetic- and electric-forces enabling reflective color-changes in a liquid medium, the surface of silica coated-iron oxide core–shell nanoparticles (Fe3O4@SiO2) is successfully modified with two-different types of silane coupling agents to improve the dispersion stability as well as the color change strength as a result of the effectively increased repulsion. A stimuli-responsive magneto- and electro-chromatic ink is prepared by mixing hydrophobic surface modified Fe3O4@SiO2-Fx (x = 0 and 13) core–shell nanoparticles and a dispersing agent in a low dielectric medium (LDM). The magneto-chromatic and electro-chromatic stimuli-responsive properties are visually confirmed. Moreover, the optical reflective color spectra and color gamut calculated from the CIE chromaticity coordinates of the hydrophobic surface modified Fe3O4@SiO2-F13 core–shell nanoparticles (with “F moiety” in the molecular structure) under an applied voltage range of 0 V to 10 V show that the hydrophobic surface modified magnetite nanoparticles are promising candidates for reflective display applications.