NMR Relaxation Efficiency of Aqueous Solutions of Composite MgxZnyFe3−x−yO4 Nanoparticles

Abstract

The results of proton nuclear magnetic resonance (NMR) relaxation measurements in aqueous solutions of Mg_xZn_yFe_3−x−yO₄ magnetite-based composite magnetic nanoparticles (MNPs) are discussed. It is shown that their transverse relaxivity (relaxation efficiency) r₂ is significantly higher than the longitudinal relaxivity r₁ and depends on the magnetic nanoparticles composition and preparation method. A polyelectrolyte layer adsorbed on the nanoparticle surface increases both relaxivity values. The carbonate-synthesized MNPs possess higher values of r₂ and r₁ as compared with base-precipitated complex oxides. Relaxivity r₂ is shown to be affected by stability of MNPs in aqueous solutions and the aggregation behavior apparently can be assessed through the NMR relaxation measurements.