Investigations on structural, optical, and photocatalytic properties of Sm- substituted Ni-Zn ferrite nanoparticles for wastewater remediation

The sol-gel auto combustion method was successfully employed to synthesize pure and Sm doped Ni-Zn ferrite, Ni _0.5 Zn _0.5 Fe _2−x Sm _x O ₄ (x = 0.00, 0.02, 0.04, 0.06, and 0.08) nanoparticles, and studied their structural, optical, and photocatalytic properties. The X-ray diffraction studies confirmed the formation of a single-phase cubic spinel structure with lattice distortion, upon Sm ³⁺ substitution. The average crystallite size of the undoped sample was calculated and found 26.02 nm by using Debye-Scherrer equation. A decrease in crystallite size was observed upon Sm ³⁺ substitution due to induced lattice strain. Structural stability and effective dopant incorporation were confirmed by the distinctive tetrahedral and octahedral M-O vibrations, recorded in FTIR spectra. According to UV-visible absorption studies Sm ³⁺ doping resulted to a red shift in the absorption edge narrowing band gap (1.89 → 1.71 eV). As a function of increasing Sm ³⁺ concentration, Urbach energy has been decreased suggesting better electronic uniformity with reduced optical disorder. UV light-driven dye degradation was employed to evaluate the photocatalytic performance of the prepared ferrite samples in which Sm-doped sample with x = 0.08 composition, exhibited noticeably higher activity with maximum degradation efficiency of 98% and rate constant of 0.111 min ^− 1 . After consecutive five cycles, reusability studies showed good catalytic stability maintaining over 90% efficiency. These findings demonstrated the effectiveness and stability of Sm ³⁺ substituted Ni-Zn ferrites as UV-light active photocatalysts.