Room-Temperature Superparamagnetism and Enhanced Photocatalytic Activity of Magnetically Reusable Spinel ZnFe2O4 Nanocatalysts

Abstract

Spinel ZnFe2O4 nanoparticles (NPs) were successfully synthesized by a simple microwave irradiation method (MIM) using glycine as the fuel. For the comparative study purpose, it was also prepared by a conventional heating (CHM) method. Powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), high-resolution scanning electron microscope (HR-SEM), high-resolution transmission electron microscope (HR-TEM), energy-dispersive X-ray (EDX) spectra, and selected area electron diffraction (SAED) analysis showed that the samples were pure-phase spinel ZnFe2O4 nanoparticle-like morphology without any other secondary-phase impurity. UV-Visible diffuse reflectance spectra (DRS) and room temperature photoluminescence (PL) spectra confirmed the optical band gap (Eg) and defect state of the samples. The calculated Eg values of the samples are 1.98 and 2.11 eV for ZnFe2O4-CHM and ZnFe2O4-MIM, respectively. Vibrating sample magnetometer (VSM) analysis shows that the Ms value is 37.66 emu/g for ZnFe2O4-MIM, which is higher than the ZnFe2O4-CHM (24.23 emu/g) sample, which confirms that both the products showed a superparamagnetic behavior. ZnFe2O4-MIM was found to have a higher surface area than ZnFe2O4-CHM, which in turn leads to the improved performance towards the photocatalytic degradation (PCD) of methylene blue (MB), and it was found that the sample ZnFe2O4-MIM shows a higher PCD efficiency (91.43%) than ZnFe2O4-CHM (84.65%); also, the samples show high activity, good reusability, remarkable stability, and environmentally friendly materials for industrial and technological applications.