In this protocol, the synthesis, antibacterial activity, and catalytic performance of super paramagnetic iron oxide nanoparticles (SPIONs) coated with L-arginine (Arg) grafted alginate (Alg), as an environmental benign heterogeneous catalyst are reported. The SPIONs coated materials were prepared by the co-precipitation method and characterized by Fourier transform infrared spectrometer (FT-IR), scanning electron microscope (SEM (, transmission electron microscopy (TEM), X-ray diffraction (XRD (, vibrating-sample magnetometer (VSM (, thermal gravimetric analysis (TGA), and energy dispersive X-ray spectroscopy (EDS). Moreover, the synthesized Fe3O4@Alg@CPTMS@Arg was employed for the preparation of 2,4,5-triarylimidazoles derivatives via a one-pot three-component reaction between ammonium acetate, aldehyde derivatives, and benzil under reflux in ethanol. Fe3O4@Alg@CPTMS@Arg exhibited highly effective catalytic activity. Apart from the catalytic activity, a study on the antibacterial activity of the prepared amino acid modified Fe3O4 nanoparticles, Fe3O4@Alg@CPTMS@Arg, was carried out on bacterial strain and compared with the antibacterial activity of the bare alginate. The results shown high antibacterial activity for the prepared nanocomposites against both Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) compared to alginate. It is assumed that the antibacterial synergism is the combined effect of alginate and L-arginine.