Dual electric and magnetic responsivity of multilayered magnetite-embedded core/shell silica/titania nanoparticles with outermost silica shell

Abstract

Multilayered magnetite-embedded core/shell silica/titania (SiO₂/TiO₂) nanoparticles with an outermost silica shell (SiO₂/TiO₂@Fe₃O₄/SiO₂) were synthesized and used to develop stimuli-responsive smart fluids. Benefiting from the incorporation of the various materials, these smart fluids demonstrated electrorheological (ER) and magnetorheological (MR) activities under applied external electric (E) and magnetic (H) fields, respectively, and electromagnetorheological (EMR) characteristics with the simultaneous application of E and H fields. The inner SiO₂/TiO₂ core nanoparticles, embedded Fe₃O₄ nanoparticles and the outer SiO₂ shell served as electroresponsive, magnetoresponsive and preventative materials toward corrosion, sedimentation and aggregation. The EMR performance of these fluids depended on the direction of the applied E and H fields. Notably, a 6.6-fold enhancement in EMR activity was observed with parallel application of E and H fields compared to perpendicular direction. This study demonstrates an effective approach to precisely and spatially control the rheological/mechanical properties of dual-responsive smart fluids via both field-induced and directional control of external fields.