Magnetic-field tunability of optical properties in colloidal suspensions of goethite (alfa-FeOOH) nanorods

The dependence of polarized optical properties of colloidal suspensions of goethite (?-FeOOH) nanorods in water and PAO base fluids under the action of an applied magnetic field are investigated in the ultraviolet, visible and near infrared from 300 to 1500 nm wavelength. We found that the transmittance in the NIR range can be tuned by changing magnetic field direction and strength. Moreover, we found that the magnetic field dependence of optical properties is strongly connected to the base fluid where magnetic nanoparticles are suspended. The obtained results show that the optical properties of goethite-based suspensions are very sensitive to even weak external magnetic fields, with promising perspectives for sensing applications.