Dual Stimuli-Responsive Smart Fluid of Graphene Oxide-Coated Iron Oxide/Silica Core/Shell Nanoparticles

The graphene oxide-coated iron oxide/silica core/shell nanoparticles (Fe 3 O 4 /SiO 2 /GO NPs) are successfully fabricated and adopted as the dual stimuli-responsive smart fluid. The Fe 3 O 4 /SiO 2 /GO NPs exhibit both electrorheological (ER) and magnetorheological (MR) characteristics, attributed to the SiO 2 /GO layer in the shell part and Fe 3 O 4 in the core part, respectively. Particularly, the ER efficiency of the Fe 3 O 4 /SiO 2 /GO NPs-based ER fluid is ca. 191 at the applied electric field of 3 kV mm –1 . Moreover, the MR performance of the Fe 3 O 4 /SiO 2 /GO NPs-based MR fluid is significantly enhanced up to 135-fold at the applied magnetic field of 1 T compared to the zero-field stress. Furthermore, it is remarkable that the Fe 3 O 4 /SiO 2 /GO NPs represent high colloidal stability and outstanding antisettling property because of the electrostatic repulsion between oxygen functional groups on GO nanosheets and the relatively low density compared with other magnetic particles. Dual stimuli-responsive characteristics in addition to the excellent antisedimentation property of the Fe 3 O 4 /SiO 2 /GO NPs-based smart fluid would provide a feasible candidate for practical applications.