Octahedral-Shaped Fe3O4 Nanoparticles With Enhanced Specific Absorption Rate and R2 Relaxivity

Herein, we have synthesized citric acid functionalized monodisperse (6-12 nm) octahedral-shaped Fe3O4 nanoparticles (NPs). The as-prepared octahedral-shaped Fe3O4 NPs exhibit a bulk-like magnetization (similar to 92 emu/g) value due to lesser surface spin disorder. In addition, compared with spherical morphology, these octahedral NPs (Oct-NPs) exhibit much higher specific absorption rate (SAR) value as a potential candidate for hyperthermia treatment and higher R-2 value as an efficient contrast agent for magnetic resonance imaging. The enhanced R-2 relaxivity and SAR values are attributed to the higher saturation magnetization (MS) value and a larger surface area of Oct-NPs. The R-2 value of 12 nm-sized Oct-NPs suspension is 353 mM(-1)s(-1), which is 3.5 times higher than that of the commercial contrast agent. With increase in size (6-12 nm), the R-2 value gradually increases from 198 to 353 mM(-1)s(-1); this increase is a consequence of the MS enhancement as well as the surface area.