Observation of Effective Permittivity of Water-Dispersible FePt Nanoparticles at Microwave Frequencies

The 2-4 nm FePt nanoparticles were synthesized by chemical reduction and dispersed into the aqueous solution after the surface modification. The dielectric spectra were measured by an open-ended transmission line technique. An open-ended coaxial cable line was designed to transmit the microwave signals into nanoparticle-filled solutions. The reflection signal revealed the dielectric properties of hydrophobic-coated FePt-filled solution was received by the transmission line. The analysis showed that the effective permittivity was around 70 and down to 50 by the external magnetic field. The flexibility of nanoparticles' permittivity revealed in this study implicates their potential applications ranged from in microwave and millimeter-wave components to biomedical drug delivery system and positron emission tomography scan