Controlling crystal habit and magnetic properties of Fe3O4 nanoparticles through the stirring velocity for bio-detection applications

Iron Oxide nanoparticles possess great potential in technological as well as biomedical applications. Significant biomedical applications include drug delivery, cancer hyperthermia, bio-detection, magnetic separation of biomolecules, etc. Among most suitable entities are magnetite, i.e., Fe3O4 nanoparticles. Several synthetic approaches have been attempted to achieve size, shape as well as properties control and biofunctionalization. In this work, we focus on controlling crystal habit and magnetic properties via stirring velocity for potential bio-detection applications. Magnetite nanoparticles were synthesized by a simple co-precipitation method at temperature of 60ºC but at varying stirring velocities. Characterization was carried out via XRD, SEM-EDS, TEM-SAED, as well as magnetic properties were estimated by VSM and GMR. Saturation magnetization (Ms), remanent magnetization (Mr) and coercive field (Hc) were determined during VSM analysis, while the measurement of the output voltage as a function of the applied field for a bare GMR sensor were estimated to check utility of Fe3O4 nanoparticles as a label bio-detection application. At different stirring velocities, nanoparticle size was estimated by XRD, SEM and TEM, and the result are complimentary to each other. Fe3O4 nanoparticles with size 10.19±0.21 nm, 10.5± 0.33 nm, 12.5±0.35 nm and 12.79±0.15 nm at stirring velocities of 500, 600,700 and 800 rpm, respectively. XRD and EDS confirmed the formation and composition of Fe3O4 phase. This stirring velocity was found to be suitable for obtaining nanoparticles with an average size below 20 nm, and increasing the stirring velocity resulted in larger sizes and a more uniform distribution of shapes. Finally, GMR experiments have shown that the prepared Fe3O4 could be used as an effective magnetic label for bio-detection applications.