Rhombohedron and plate-like hematite (α-Fe2O3) nanoparticles: synthesis, structure, morphology, magnetic properties and potential biomedical applications for MRI

Hematite nanorhombohedrons and nanoplates have been prepared through a hydrothermal synthesis process. The nanoplates possess width of 100 nm and thickness of 30 nm whereas hematite nanorhombohedrons (cube-like particles) have an edge length of 50 nm. The magnetization show that the Morin transitions of the samples occur at nearly the same temperature showing slightly shape-dependent magnetic properties (T-M(P) = 242 K (plates) and T-M(R) = 221 K (rhombohedrons). The nanorhombohedrons exhibit hysteresis properties with low coercivity H-C(R) = 22 Oe at room temperature, whereas nanoplates show much higher coercivity (similar to 24 times higher) H-C(P) = 522 Oe and strongly shape-dependent magnetic properties. The coercivity below the Morin transition is also observed for nanorhombohedmns H-c(R) = 178 Oe and for nanoplates H-C(P) = 2280 Oe. The transverse relaxivity rate R-2 (1/T-2) measured on 15.2 T magnetic resonance imaging (MRI) scanner was higher for nanoplates than for nanorhombohedrons (12.63 vs 10.72 mM(-1)s(-1)). The properties of the samples are discussed in relation to the particle shape.

Automated summary

Hematite nanorhombohedrons and nanoplates were prepared through a hydrothermal synthesis process, with the nanoplates showing higher coercivity and transverse relaxivity rate compared to the nanorhombohedrons, indicating a shape-dependent magnetic behavior.