Synthesis and evaluation of Gd3+-doped Ni-Zn nanocatalyst for structural, optical, magnetic properties, and high photocatalytic activity for wastewater treatment

Abstract

Pure and gadolinium-doped Ni-Zn ferrite nanoparticles were synthesised via the sol–gel auto-combustion route. X-ray diffraction analysis confirms the phase formation of cubic spinel structure with the Fd-3 m space group. Average crystalline size and microstrain were obtained from W-H plots, with values of 52 to 107 nm and 0.9 to 1.6, respectively, indicating the nanoparticle nature of NZGF. FTIR spectra revealed two characteristic spinel bands at 386 cm⁻¹ and 570 cm⁻¹, and the presence of functional groups. SEM micrographs show semi-spherical and polygon-shaped nanoparticles for higher doping levels, suggesting that the Gd doping impacts the morphology of the prepared samples. The optical properties were evaluated by UV–vis spectroscopy. It was found that the optical band gaps ranged from 1.65 to 1.71 eV. A smaller band gap energy signifies the semiconducting behaviour of NZGF. At room temperature, magnetic characterisation revealed that the samples exhibited low coercivity (≤50 Oe), reduced saturation magnetisation, and magnetic anisotropy, as determined by fitting the experimental data to the law of approach to saturation. The photocatalytic performance was assessed via the degradation of methylene blue (MB) dye under visible light irradiation. The incorporation of Gd³⁺ ions significantly enhanced the degradation efficiency from 21.4 % to 66.4 %. These findings indicate that precise tuning of the structural and compositional parameters can simultaneously optimize both the magnetic and photocatalytic functionalities of the material, highlighting its potential suitability for soft magnetic components and wastewater remediation applications.