Fabrication of Fe3O4 nanorods designed for liquid-phase magnetic biosensing

Alternating current (ac) susceptibility-based magnetic biosensing techniques in liquids are promising biomedical applications of magnetic nanoparticles because the methods have a potential for realizing the simple wash-free detection of diseases. Controlling magnetic relaxation of nanoparticles is crucial in the biosensing; Brownian relaxation based on the particle rotation in liquids should be dominant to improve the sensitivity. Therefore, we focus on magnetically anisotropic Fe3O4 nanorods because it is considered that the particle rotation dominates magnetic response of suspended Fe3O4 nanorods due to the shape magnetic anisotropy. In the present paper, the Fe3O4 nanorods are fabricated and the dynamic magnetic response of Fe3O4 nanorods is evaluated under the liquid phase and the solid phase.