Synthesis of Magnetic Nanoparticles for Biosensing Studies Using Magneto-Impedance Technology*

Polymer nanocomposites (PNCs) have been shown to be a compact and durable solution for applications such as electromagnetic interference shielding and magnetically tunable microwave devices. We report studies aimed at exploring applications of PNCs to aid in bio-sensing, using the Giant Magneto-Impedance (GMI) effect. GMI is a change in the ac impedance of a ferromagnetic conductor in a varying dc magnetic field, and has been shown to be about 500 times more sensitive than its counterpart, Giant Magneto-Resistance (GMR). In our study, magnetite (Fe$_{3}$O$_{4})$ nanoparticles (mean size, 6$\pm $2 nm) were synthesized by thermal decomposition and dispersed in a polymer provided by the Rogers Corporation to create PNCs with 20, 50, and 80 wt{\%} compositions. The GMI of an amorphous magnetic ribbon was measured with and without the PNCs layered on the ribbon. The effects of nanoparticle concentration on the GMI sensitivity were studied, with a view toward applications in highly sensitive bio-molecular detection.