Magnetic properties of mesoporous hematite/alumina nanocomposite and evaluation for biomedical applications

A porous hematite/alumina nanocomposite is produced by sol-gel combustion synthesis. The XRPD, Raman and FTIR methods show the presence of α-Fe2O3 phase while SEM, TEM, EDS and BET techniques further reveal the formation of porous ellipsoid-like nanostructure of hematite nanoparticles coated by amorphous alumina. Hematite nanoparticles have a size of ~40 nm whereas the porous hematite/alumina nanocomposite particles are ~100 nm in size with characteristic pores of ~7 nm. The M(H) at 300 K exhibits coercivity HC = 293 Oe and magnetization MS = 2.71 emu/g and at 5 K HC = 1150 Oe and MS = 9.25 emu/g. The M(T) under H = 100 Oe shows a bifurcation between ZFC/FC magnetization curves at all measurement temperatures Tirr>350 K (irreversibility temperature) and blocking temperature at TB ~ 305 K. Unexpectedly, the M(T) measurements under H = 10 kOe reveal the suppressed Morin transition at TM = 225 K. The analysis of the results and data from the literature reveal that the porous surface structure of hematite induces the atypical magnetic properties. A magnetic resonance imaging (MRI) properties show the transverse relaxivity rate (r2) of 0.44 mM−1s−1 at 7 T and 1.06 mM−1s−1 at 15.2 T. The investigated nanocomposite particles could be useful in biomedical applications due to their low cytotoxicity and porous nanostructure.