Influence of Reaction Solvent on Crystallinity and Magnetic Properties of MnFe2O4 Nanoparticles Synthesized by Thermal Decomposition

This study reports the synthesis of three kinds of manganese-doped magnetic ferrite nanoparticles (MnFe2O4) in benzyl ether, octyl ether, and 1-octadecene by a simple and low cost thermal decomposition method. It was found that benzyl ether results in a dramatic improvement in nanoparticle crystallinity owing to its stronger reducibility compared to octyl ether and 1-octadecene, as demonstrated by X-ray diffraction and TEM measurements. Raman spectroscopy detection also indicated that the reducing solvent of benzyl ether was in favor of forming magnetite-like structure ferrite, while maghemite-like structured ferrite was obtained in octyl ether and 1-octadecene. The saturation magnetization (MS) of MnFe2O4 synthesized in benzyl ether was 85 emu/g [Fe], which was 3 and 5 times larger than MnFe2O4 synthesized in octyl ether and 1-octadecene, respectively. The specific absorption rate (SAR) of MnFe2O4 nanoparticles synthesized in benzyl ether was 574 W/g, while MnFe2O4 nanoparticles synthesized in octyl ether and 1-octadecene have had much smaller SAR of 76 and 33 W/g, respectively. MnFe2O4 nanoparticles synthesized in benzyl ether also exhibit higher relaxivity (r2=207 mM−1 s−1) than those synthesized in octyl ether and 1-octadecene (r2=65 and 22 mM−1 s−1). It was obvious that MnFe2O4 nanoparticles synthesized in reducing benzyl ether have higher crystallinity and thus higher MS, SAR, and r2 values, which can serve as a better candidate for hyperthermia and magnetic resonance imaging