Controlled synthesis and self-assembly of ZnFe2O4 nanoparticles into microspheres by solvothermal method

Abstract

Zinc ferrite (ZnFe2O4) colloidal nanoparticle assemblies (CNAs) were prepared controllably by solvothermal synthesis without the assistance of a template or surfactant. The x-ray diffraction (XRD) results confirm the formation spinel structure of ZnFe2O4 with the grain size around 11 ± 3 nm. Scanning electronic microscope (SEM) images show that the CNAs are sub-microspheres self-assembled by nanoparticles with size about 284-346 nm changed with reaction conditions. The composition of elements Zn, Fe and O in the ZnFe2O4 CNAs is identified by using EDAX analysis. Roomerature vibration magnetic measurements (VSM) demonstrates the as-obtained ZnFe2O4 CNAs showing superparamagnetic behavior with saturation magnetization values between 58 and 66 emu g-1. The UV-vis diffuse reflectance (UV-vis DRS) analysis revealed that the band gap energy is increased (blue shift) with decrease of particle size. The nitrogen adsorption-desorption analysis shows that CNAs are meso and microporous with a specific surface area from 71.68 to 92.92 m2g-1. The reaction time and different amounts of anhydrous sodium acetate (NaAc) influence the crystallinity, size, magnetic property and surface area of the ZnFe2O4 CNAs.