Exploration of the structural, physical and antimicrobial properties of aluminium-doped nickel-strontium ferrite nanoparticles synthesised by the sol–gel route

Using the sol–gel auto-combustion method to synthesise aluminium-doped nickel-strontium ferrite nanoparticles makes a thermally stable material with a yield of 69.4%. The optical band gap of the material ranges from 3.62 to 3.75 eV, with maximum absorption at 302.57 nm. The X-ray diffraction reveals that the average particle size ranges between 18 and 25 nm with the FCC crystal structure, as confirmed by high-resolution transmission electron microscopy. The presence of all elements was validated by energy dispersive X-ray spectroscopy. The paramagnetic behaviour was revealed by a vibrating sample magnetometer. The total surface area ranges from 8.00 to 24 m²g⁻¹. At P/Po (0.99), the total pore volume ranges from 0.011 to 0.037 cm³g⁻¹. The average pore diameter ranges from 5.44 nm to 6.49 nm and shows isotherm type III with an H₃ hysteresis loop. A dielectric study revealed that ε’ and tan δ decreased with Al³⁺, Sr²⁺ and Ni²⁺ ions doping lower dielectric loss and dielectric constant. These nanoparticles execute antimicrobial activity against Gram-positive and Gram-negative microorganisms as well as against fungal pathogens.