Al-doped zinc ferrite nanoparticles: Preparation and evaluation of thermal, structural, morphological and anticancer properties

Highlights: • Doping with Al³⁺ leads to decrease in lattice parameter as compared with pure ZnFe₂O₄. • The W-H plot, which gives information about the dislocation of crystal planes. • Significant variations in the energy band gap values were obtained due to Al-doping. • Annealed Al-doped ZnFe₂O₄ NPs shown less viability towards MCF7 and A549 as compared with pure ZnFe₂O₄. -- Abstract: The aim of this study was to evaluate the thermal, structural, optical, morphological and anticancer properties of ZnFe₂O₄ (ZFO) and Al_xZn_1−xFe₂O₄ (x = 0.05) (ZAFO) nanoparticles. Zinc ferrite nanoparticles were prepared by chemical co-precipitation method, using polyethylene glycol (PEG) as the capping agent. The synthesized pure and Al-doped ZnFe₂O₄ nanoparticles were annealed at different temperatures such as 500, 600, 700 and 800 °C. X-ray diffraction analysis was used to determine lattice parameters like X-ray density, oxygen position parameter, distribution of cation among tetrahedral and octahedral sites, ionic radii, and edge lengths of the tetrahedral (A) and octahedral (B) sites and micro strain values. The calculated micro strain values were found to be decreasing with increasing annealing temperatures in both ZnFe₂O₄ and Al_xZn_1−xFe₂O₄ (x = 0.05) samples. The FTIR results confirmed ferrites tetrahedral (~540 cm⁻¹) and octahedral sites (~431 cm⁻¹) metal oxygen vibrations. The morphology of the synthesized ZnFe₂O₄ and Al_xZn_1−xFe₂O₄ (x = 0.05) nanoparticles were studied by field emission scanning electron microscopy (FE-SEM) and particle size was found to be<100 nm. Band gap energy at different temperatures were calculated using Tauc plots and found to be decreasing with increase in annealing temperatures for both ZnFe₂O₄ and Al_xZn_1−xFe₂O₄ (x = 0.05) nanoparticles. The anti-cancer properties were observed at the in vitro level by MTT (3-[4, 5-dimethylthiazol-2-yl]-2, 5 diphenyltetrozolium bromide) assay against human Breast cancer cell line, MCF-7 (Human Breast adenocarcinoma) and lung cancer cell line A549 (Human Lung Carcinoma). Among the pure and Al doped samples used in the present study, the ZnFe₂O₄ (ZFO-3) sample annealed at 700 °C showed less viability in A 549 (Human Lung Carcinoma), whereas Al_xZn_1−xFe₂O₄ (ZAFO-1) sample annealed at 500°C showed less viability in MCF-7 (Human Breast Adenocarcinoma). Toxicity studies have shown that ZnFe₂O₄ and Al_xZn_1−xFe₂O₄ (x = 0.05) NPs reduced cell viability and induced cell membrane damage dose dependently in the concentration range of 25–100 µg/mL