The synthesis of metallic nanoparticles has ignited intense interest over the last decade due to their unique properties, which make them applicable in a variety of fields of science and technology. In this study, iron oxide nanoparticles (Fe2O3 NPs) were synthesized, characterized, and their antibacterial activity was determined using a low-cost and simple method. Method: In this paper, magnetic nanoparticles were synthesized by a physical method of pulsed laser ablation in a liquid medium with 600 mJ energy. Magnetic Fe2O3 NPs were prepared by using a 1064 nm Nd-YAG laser and bombarding the α-Fe2O3 target in a deionized aqueous solution. An absorption spectrometer was used to study the optical properties and structures of nanoparticles, the prepared nanoparticles were analyzed using Fourier transform infrared (FTIR) spectroscopy. Besides, utilizing FESEM, the morphological and surface characteristics were examined. The antibacterial activity of Fe2O3 NPs against several pathogenic Gram-positive and Gram-negative bacteria isolated from various human infection sites was investigated using a disk diffusion experiment with laser pulse lengths of (100 nm, 150 nm, 200 nm and 300 nm) with the same laser energy. Result: The results showed the success of this method as the first sign that can be inferred from the change in the color of the solution to prepare nanoparticles. Fe2O3 NPs are mostly spherical in shape, with nano sizes ranging between 66.7 nm and 9.5 nm. The energy gap was found to be in the range of 1.79–2.39 eV for almost all nanoparticles prepared. Fe2O3 NPs were formed in almost spherical surface morphology with regular size and shape. The results showed their effect on stopping the growth of bacteria of type E. coli maximum zone of inhibition of 20 mm and 19 mm of S. epidermidis, 18 mm of type S. mutans and 16 mm of P. aeruginosa. As a result, in this study, it was shown that Fe2O3 NPs produced in water by laser ablation method can be used as antibacterial agents due to these properties.
