Spinel ferrite nanoparticles offer a unique combination of magnetic functionality and antimicrobial activity, motivating the development of sustainable synthesis routes and compositional tuning strategies for biomedical and environmental applications. This study aimed to elucidate how the cobalt/manganese ratio modulates the structural, magnetic, and antibacterial properties of CoxMn(1−x)Fe2O4 nanocomposites prepared via a novel henna-green/microwave-assisted hydrothermal method that leverages henna extract as an eco-friendly capping agent. Thermal analysis of Co0.5Mn0.5Fe2O4 showed multistep mass losses associated with dehydration and precursor/henna decomposition. FTIR bands near ~ 520 and ~ 420 cm− 1 confirmed spinel M–O vibrations in tetrahedral and octahedral sites with composition-dependent shifts. XRD verified a cubic spinel phase of MnFe2O4 with minor phases of α-Fe2O3 and Mn2O3 while Co incorporation promoted notably pure CoFe2O4 ; crystallite sizes ranged from 37.5 nm (CoFe2O4) to 43.6 nm (MnFe2O4). SEM revealed Co/Mn-dependent morphologies (flower-like plates, elongated plates, segmented cubes, round disks, polygonal structures). XPS confirmed mixed valence states (Co2+/Co3+, Mn2+/Mn3+, Fe2+/Fe3+) and lattice/defect oxygen components. All compositions were ferromagnetic, with the highest coercivity for Mn0.25Co0.75Fe2O4 (772 G) and composition-driven increases in magnetization (Ms up to 92 emu/g; Mr up to 22 emu/g). Antimicrobial testing showed strongest overall activity against S. aureus, with maximal reduction for CoFe2O4 (94%); E. coli reduction peaked at 54% (CoFe2O4), while C. albicans reduction was highest for MnFe2O4 (37%). Collectively, the henna-assisted microwave-hydrothermal route enables composition-controlled Co–Mn ferrite nanocomposites whose phase assemblage, morphology, magnetic hardness, and antimicrobial performance can be tailored by the Co/Mn ratio, supporting application-specific design of multifunctional ferrite materials.
Ghalib et al. (Mon,) studied this question.