Nanostructure, Band Gap, and Antibacterial Activity of Spinel Fe₂MO₄/OO Magnetic Fluids

This research aimed at investigating Fe₂MO₄ ferrofluids nanostructure, with M was Fe, Ti and Cr. Fe₂MO₄ nanoparticles were synthesized through coprecipitation method, and the phase and crystallinity were analyzed using XRD instrument. The obtained results showed the Fe₃O₄ phase, but there was a shift in diffraction peak position contributed by the doping of Ti²⁺ and Cr³⁺ ions. Furthermore, a similar change occurred in the lattice parameter, crystal volume, and particle size. The particle sizes of Fe₃O₄, Fe₂TiO₄, and Fe₂CrO₄ particles were 10.2, 13.4, and 6.9 nm, respectively. The functional groups of the Fe₂MO₄/OO ferrofluids were characterized using FTIR and obtained the Fe-O stretching band shift due to the modification of structure. Furthermore, FTIR analysis was used as a reference to confirm functional groups of the ferrofluids. The absorbance data collection was performed through the characterization using UV-Vis instrument, and there was intervalence charge transfer at a wavelength near infra-red indicating there was Fe element and nanoparticle interface which raised an optimum absorption at the interval of 400-550 nm. Furthermore, through the obtained absorbance data, there was an energy gap of 2.2-2.24 eV. Interestingly, the results of antibacterial testing results through the dilution method showed a modification of structure could increase the antibacterial activity of the Fe₂MO₄/OO ferrofluids by minimizing the percentage of surviving colony number.