Characterization and antibacterial activity of iron oxide nanoparticles synthesized using co-precipitation method

Iron oxide nanoparticles (IONP) could generate reactive oxygen species (ROS), which support their application for antibacterial purposes. Optimization of the IONP synthesis parameters, such as precursor concentration and stirring rate, is necessary to achieve satisfactory physicochemical properties. This study aims to evaluate the effect of precursor concentrations (0.05 M and 0.10 M) and stirring rates (600 rpm and 800 rpm) on the physicochemical characteristics and antibacterial activity of IONP. The XRD analysis confirmed the presence of the maghemite (ɣ-Fe₂O₃) phase. The synthesized IONP exhibited a cubic and uneven spherical shape with a band gap energy ranging from 1.83 to 1.97 eV. The hydrodynamic particle size ranged from 205 to 368 nm and exhibited a mid-range polydispersity (PDI = 0.3294-0.5991). The zeta potential values were between (-) 34.44 mV and (-) 41.74 mV, implying moderate stability and low aggregation tendency. The increase in precursor concentration reduced the crystallite size and lattice constant; however, micro-strain, crystalline index, and particle size increased. Meanwhile, the stirring rate highly affected morphology, polydispersity index (PDI), and band gap energy. The IONP with 1000 ppm concentration effectively inhibited the growth of bacteria, as confirmed by the zone of inhibition diameter, which was 9.00-17.67 mm for Escherichia coli and 10.67-14.67 mm for Staphylococcus aureus. The application of the magnetic field was also beneficial in enhancing the antibacterial activity of IONP. This study indicates that the precursor concentration and stirring rate must be rigorously controlled to obtain the required characteristics of IONP and its antibacterial activity for infectious diseases.