Green synthesis of meso-porous CuFe2O4 nanoparticles through aloe-vera assisted sol–gel auto-combustion method

Abstract

An environmentally friendly green technology approach was employed to synthesize CuFe₂O₄ nanoparticles at a lower temperature using the sol–gel auto-combustion method with natural aloe-vera as a green fuel, followed by annealing of the sample at 400 ºC. The structural, morphological, vibrational, mechanical, optical, surface area and magnetic characterizations were performed using XRD, SEM-EDAX, FTIR-Raman, UV-DRS, BET and VSM techniques. XRD pattern reveals the CuFe₂O₄ spinel cubic phase (Fd3m-227) with trace amounts of CuO and α-Fe₂O₃ phases. The estimated crystallite sizes for as-prepared and annealed samples were found to increase. An agglomerated morphology with irregular shape of particles was observed. Raman spectroscopy identified five vibrational modes of the CuFe₂O₄ phase. FTIR analysis detected tetrahedral and octahedral metal–oxygen modes, providing a deeper understanding of the sample’s mechanical behaviour. The bulk-to-rigidity modulus ratio (B/G) of ~ 1.530 to 1.538, and Cauchy pressure (C_p) of ~ − 1.98 and − 2.50 GPa for as-prepared and annealed samples confirm the material’s brittle mechanical nature. The optical bandgap (~ 1.60 eV) and Urbach energy (~ 0.369 eV) values were very similar for both as-prepared and annealed samples. The samples exhibit semiconducting behavior with significant defect levels, as confirmed by analysis of Urbach energy. The specific surface area of 107.37 m²/g and 74.63 m²/g, and pore size between 6.49 nm and 6.98 nm confirmed the mesoporosity of the prepared samples. The magnetic analysis revealed the S-shaped hysteresis curves with soft ferrimagnetic behaviour with a lower magnetic saturation value of ~ 6.8 emu/g, magnetic remanence of ~ 0.48 emu/g, and coercivity ranging from 80 to 97 Gauss. The magnetic saturation decreases while increasing coercive field and magnetic anisotropy as crystallite size increases with an increase in annealing temperature to 400 ºC. The magnetic and optical properties of prepared copper ferrite nanoparticles indicate their green synthesis and their potential for catalysis, magnetic separation, electromagnetic shielding, and biomedical applications.