Exploring the effect of crystalline phase on photocatalytic, antimicrobial and antioxidant performance of magnetic iron oxide nanoparticles

Iron oxide nanoparticles (IONPs) with different crystalline phases constitute an outstanding category of functional materials due to their promising magnetic characteristics, biocompatibility, and non-toxicity. To investigate the effect of phase, a comparative study has been carried out based on diverse applications. For this purpose, highly crystalline, pure, and spherical-shaped Fe3O4 (Magnetite) and α-Fe2O3 (Hematite) NPs have been synthesized with particle sizes 14 and 16 nm respectively. The X-ray diffraction patterns confirmed the cubic and rhombohedral crystal structures of the Fe3O4 and α-Fe2O3 NPs respectively. The photocatalytic dye degradation efficacy towards various toxic organic pollutants, Crystal violet (CV), Malachite green (MG), and Eosin yellow (EY) dyes, at a loading of 20 mg/L nanocatalyst and 120 minutes of sunlight exposure revealed the relatively superior performance of the α-Fe2O3 NPs. The antifungal and antibacterial studies against broad-spectrum microbes unveiled a noteworthy variation in the microbial growth inhibition capacity of these IONP polymorphs. Furthermore, the antioxidant assay indicated the potential free radical scavenging capability of Fe3O4 NPs (IC50 = 116.56 µg/ml) over α-Fe2O3 NPs (IC50 =187.01 µg/ml). The oxidation state (Fe2+/Fe3+), crystal structure, surface atomic coordination, energy band gap, number of active sites, cationic vacancies, etc. are some of the primary factors contributing to the distinctive performance of the different crystalline phases of the IONPs.