Structural and magnetic properties of magnetic nanoparticles play a crucial role in whether these particles are promising candidates for magnetic immunoassays. To tune such properties in a systematic fashion, we synthesize highly monodisperse binary and ternary zinc- and cobalt-doped iron oxide nanoparticles with various sizes, compositions, and morphologies via high temperature decomposition syntheses. Since our magnetic immunoassays are based on the Brownian relaxation mechanism of nanoparticles, we pay a particular attention to tune, determine, and understand different relaxation processes in these particles at different stages. We run series of complementary characterizations such as transmission and scanning electron microscopy (TEM-SEM), elemental analysis (ICP-OES), and static and dynamic magnetic measurements to fully understand physicochemical properties of synthesized nanoparticles. These particles are often solely dispersible in organic solvents. We therefore next phase transfer them to water using our custom-designed polymeric ligands to enhance their anti-fouling properties using protocols established in our Lab. After the surface modification, these particles carry various functional groups, offering a variety of conjugation chemistries to label them with proteins and biomolecules.
