Developing effective antibacterial agents has become an important challenge, especially with the increasing prevalence of antibiotic-resistant bacteria. Spinel ferrite nanocomposites have attracted considerable interest in biomedical applications due to their magnetic properties and antibacterial potential. The study investigates the effects of calcination temperatures (350, 450, and 550 °C) on the magnetic and antibacterial properties of Co0.6Ni0.2Cd0.2Fe2O4 spinel nanocomposites synthesized using the sol–gel method. Understanding this relationship will provide valuable insights into optimizing ferrite-based nanomaterials for medical applications, particularly as antibacterial agents. The resulting nanocomposite was characterized using various techniques. X-ray diffraction study verified the existence of a pristine spinel phase in the specified spacing group of \(Fd\overline{3 }m\) . In addition, the crystal size slowly grew from 36.74 nm to 41.29 nm as the calcination temperature rose from 350 °C to 550 °C, but the average strain values went down from 1.79 to 1.56. The field emission-scanning electron microscopy analysis showed that the average particle size of Co0.6Ni0.2Cd0.2Fe2O4 ferrite was 39.83, 40.96, and 41.60 nm at different calcination temperatures. The energy-dispersive X-ray spectroscopy has also confirmed the presence of Co, Ni, Cd, Fe, and O in all samples. Fourier transform infrared spectroscopy revealed the fingerprint bands υ1 (~ 578) and υ2 (~ 381) at 550 °C. Vibrating sample magnetometer analysis revealed that saturation magnetization increases from 53.95 to 57.37 emu/g1 at 350 and 550 °C, respectively. The antibacterial examination performed via the agar well diffusion technique demonstrated that the Gram-positive bacteria, such as Staphylococcus aureus and Streptococcus mutans, were the most sensitive strains. They exhibited significant susceptibility at the highest concentration of 500 µg/mL (± 25 mm and ± 24 mm). In contrast, Gram-negative bacteria, including Acinetobacter baumannii and Escherichia coli, showed slightly less sensitivity (± 16.2 mm and ± 15 mm). Overall, the synthesized Co0.6Ni0.2Cd0.2Fe2O4 spinel nanocomposite demonstrated potent antibacterial activity and can be considered a promising material for biomedical applications.
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