Synthesis, characterization, and nuclear magnetic resonance study of chitosan-coated Mn(₁-x)Zn(x)Fe₂O₄ nanocrystals

Ultra-fine crystallites of Mn(₁-x)Zn(x)Fe₂O₄ series (0 ≤ x ≤ 1) were synthesized through wet chemical co-precipitation method followed by calcination at 200 °C for 4 hours. Formation of ferrites was confirmed by X-ray diffraction, TEM selected area diffraction (SAD) and Fourier Transform Infra-red Spectroscopy (FTIR). Nanocrystallites of different compositions in the series were coated with biocompatible chitosan in order to investigate their possible application as contrast agent for magnetic resonance imaging (MRI). Chitosan coating examined by FTIR, revealed a strong bonding of chitosan molecules to the surface of the ferrite nanocrystallites. Spin-spin, τ₂ relaxivities of nuclear spins of hydrogen protons of the solutions for different ferrites were measured from concentration dependence of relaxation time by nuclear magnetic resonance (NMR). All the compositions Mn(₁-x)Zn(x)Fe₂O₄ of series possess higher values of τ₂ relaxivity thus making them suitable as contrast agents for τ₂ weighted imaging by MRI.