Structural, optical, and magnetic characterization of Cu-Zn-Ni spinel ferrite nanoparticles with antibacterial potential.

One of the most pressing challenges in biomedical applications is the growing prevalence of bacteria that are resistant to multiple antibiotics. Metal-based nanoparticles are emerging as a promising strategy to address this problem, which is the focus of the present work. Cu0.15Zn0.2Ni0.65Fe2O4 nano-ferrite was synthesized via the co-precipitation method. The chosen cation ratio preserves the spinel phase while Ni improves magnetic response, and Zn enhances magnetic softness and site stability. For comparison, single-cation ferrites NiFe2O4, ZnFe2O4, and CuFe2O4 were synthesized using the same procedure to enable a consistent evaluation of antibacterial activity. All ferrites were characterized using XRD and FTIR. Additional analyses including UV-Vis, SEM, EDX, XPS, TEM, VSM, and Atomic Absorption Spectroscopy (AAS) were performed for Cu0.15Zn0.2Ni0.65Fe2O4 sample. XRD confirmed a cubic spinel phase for all ferrites. FTIR provided further evidence of cation redistribution of tetrahedral and octahedral sites. AAS verified the availability of Cu2+, Zn2+, and Ni2+ ions, supporting their contribution to antibacterial activity. VSM showed soft magnetic behavior with ~ 54.3 emu/g saturation magnetization. Antibacterial tests demonstrated that Cu0.15Zn0.2Ni0.65Fe2O4 exhibits stronger inhibitory activity against S. aureus and E. coli at both low and high concentrations. At 500 μg/mL, the inhibition zone reached ~ 20 mm for S. aureus and ~ 17 mm for E. coli, The MIC values were found to be 40 μg/mL for S. aureus and 80 μg/mL for E. coli, indicating stronger sensitivity of Gram-positive bacteria. After establishing its individual performance, comparison has been obtained with single-cation ferrites. Across all trials, Cu0.15Zn0.2Ni0.65Fe2O4 consistently produced larger inhibition zones, showing clear superiority. The superior antibacterial activity is attributed to the synergistic incorporation of Cu2+, Zn2+, and Ni2+ within a single spinel lattice, giving Cu0.15Zn0.2Ni0.65Fe2O4 strong intrinsic antibacterial activity and improving performance over single-cation ferrites, confirming its novelty and potential for biomedical applications.