CoFe2O4–Fe3O4 bimagnetic heterostructure: a versatile core-shell nanoparticle with magnetically recoverable photocatalytic and self heating properties

Abstract

CoFe2O4–Fe3O4 (Fe/Co = 2.3, 2.75 & 3.5) core-shell magnetic nanocomposite (MNC) was successfully prepared by combined sonochemical and reverse co-precipitation method using cost effective and readily available precursor. The structure, morphology, thermal, optical and magnetic properties of the MNC was extensively studied and the product was found suitable for use as an environmentally safe recyclable photocatalyst for pollution control. The self-heating properties of the MNC was also investigated for magnetic hyperthermia application. The studies of Infrared (IR) and Ultraviolet-visible (UV-Vis) spectroscopy confirmed the synthesis and formation of the bimagnetic heterostructure. The x-ray Diffraction studies and Transmission Electron Microscopy (TEM) analysis confirmed the formation of subnanometer clusters (<10 nm) in the asprepared samples. The results of Differential Scanning Calorimetry (DSC)/Thermo-Gravimetric Analysis (TGA) analysis of the as prepared samples showed transformation of intermediate Fe-phases to Fe3O4 during sample heating at 420 °C. This transformation accompanied structural changes in the asprepared sample that led to the formation of the coreshell structure which was observed in the TEM images of the annealed sample with Fe/Co ratio (x = 3.5). The magnetization-hysteresis (M-H) studies was done on the asprepared and annealed samples using the Vibrating Sample Magnetometer (VSM). The VSM studies showed significant improvement of magnetization and coercivity in the annealed samples making it suitable for re-usability in photocatalytic reaction and magnetic hyperthermia application. The degradation of phenolphthalein (a non-biodegradable organic chemical) in the presence of UV light irradiation was used as a reference reaction to confirm the photocatalytic properties of the CoFe2O4–Fe3O4 MNC, which could be well isolated from the media at the end of degradation, by applying an external magnetic field and reused. The nanocomposite was also investigated for magnetic hyperthermia using induction heating properties and the result infer that it is also a promising material for hyperthermia application.