Low-coercivity behavior and biomedical potential of cube-like and rounded hematite (α-Fe2O3) nanoparticles: Insights from hydrothermal synthesis

Abstract

Understanding the shape-dependent magnetic properties of hematite (α-Fe2O3) nanoparticles is essential for advancing their biomedical and nanotechnological applications. We synthesized cube-like and rounded hematite nanoparticles using a controlled hydrothermal synthesis method by varying ethanol/water ratios, enabling precise morphological tuning. While the Morin transition temperature (TM) (225–231 K) and coercivity below TM (≈180 Oe) remain largely shape-independent, coercivity above TM exhibits significant shape dependence. Cube-like hematite nanoparticles display ultra-low coercivity (HC = 21 Oe) due to defect-minimized planar surfaces, whereas rounded hematite nanoparticles exhibit higher coercivity (HC = 306 Oe) due to defect-rich curved surfaces and atomic misalignments. MRI relaxivity measurements reveal that rounded hematite nanoparticles enhance transverse relaxivity (5.70 ± 0.17 mM[Fe]-1s−1), while cube-like hematite nanoparticles show higher longitudinal relaxivity (0.0075 mM[Fe]-1s−1), demonstrating morphology-dependent MRI contrast efficiency. With low cytotoxicity and high biocompatibility, the synthesized hematite nanoparticles show promise for biomedical applications, particularly in targeted imaging and magnetic nanodevice development. © 2025 Elsevier B.V.