Mesoporous CoFe2O4 nanocrystals: Rapid microwave-hydrothermal synthesis and effect of synthesis temperature on properties

Abstract

Cobalt ferrite (CoFe2O4) nanoparticles of the size of 7–20 nm have been easily synthesized by microwave-hydrothermal route with rapid heating at 100, 150, and 200 °C. The XRD and TEM studies establish that the pure spinel CoFe2O4 phase is obtained at all the synthesis temperatures. FTIR examination presents the bands representative of cubic CoFe2O4 phase and triton X-100 surfactant. Thermal analysis shows nominal weight loss between 25 and 1000 °C demonstrating high thermal stability of the samples. Electron microscopy examination reveals spherical morphology with the particle size increasing as the synthesis temperature increases. The EDX spectrum reveals the stoichiometric proportion to be nearly 1:2 for Co: Fe as anticipated, and the elemental mapping results show the extreme distribution of elements Co, Fe, and O. The SAED patterns show bright and distinct diffraction rings associated with the different lattice planes of cubic CoFe2O4 phase. The clear lattice fringes in HRTEM images endorse the single-crystalline nature of the nanoparticles. N2 sorption studies demonstrate mesoporous structure with specific surface area decreasing with rising synthesis temperature. These nanoparticles exhibit hysteretic magnetization at room temperature, characteristic of the ferrimagnetic material, with the room temperature saturation magnetization close to that of bulk CoFe2O4. The MS value increases, but Mr and Hc values decrease as the synthesis temperature/particle size increases. It is anticipated that the findings of this study will offer more insight into the effective use of microwave-hydrothermal synthesis to tailor the properties of CoFe2O4 nanoparticles for applications.