Green Synthesis of Iron (III) Oxide Nanoparticles Using Croton macrostachyus Stem Bark Extract and Their Antibacterial and Antifungal Activities

In this study, maghemite nanoparticles (γ‐Fe 2 O 3 NPs) were successfully synthesized using Croton macrostachyus stem bark extract (CMSBE) and hexahydrate ferric chloride (FeCl 3 .6H 2 O). The biomolecules found in the plant extract were screened through visual observations, and these molecules were used as reducing, capping and stabilizing agents during the synthesis of γ‐Fe 2 O 3 NPs. The synthesized γ‐Fe 2 O 3 NPs were characterized via different spectroscopy techniques (UV–Vis, FT‐IR, XRD, SEM and TGA/DTA). In UV–Vis spectra, the maximum absorption peak of γ‐Fe 2 O 3 NPs was observed at 410 nm; this is due to the charge transfer from O 2- into Fe (0), confirming the formation of γ‐Fe 2 O 3 NPs. For the synthesis of γ‐Fe 2 O 3 NPs, the synthesis parameters, including temperature (70°C), pH (7), reaction time (50 min), FeCl 3 .6H 2 O concentration (6 mM) and extract volume (7.5 mL), were systematically optimized. In FT‐IR spectra, the band was observed at 530 cm −1 due to Fe‐O stretching vibration, and this validates the formation of γ‐Fe 2 O 3 NPs. The XRD analysis confirmed the crystalline nature of the nanoparticles with an average crystallite size of 4.12 nm. The SEM image showed the quasispherical‐shaped particles with noticeable agglomeration. Therefore, most of the characterization methods confirm the formation of γ‐Fe 2 O 3 NPs. TGA/DTA analysis showed a total weight loss of 29.74% and high thermal stability at higher temperatures. The synthesized γ‐Fe 2 O 3 NPs using CMSBE exhibited notable antibacterial activity against both gram‐positive ( Bacillus [25.6 ± 0.06] and Staphylococcus aureus [26.25 ± 0.06]) and gram‐negative ( Escherichia coli [28.2 ± 0.01] and Klebsiella pneumoniae [24.5 ± 0.02]) bacteria as well as antifungal activity against Saccharomyces cerevisiae (12.05 ± 0.03) at 100 μg/mL. This eco‐friendly synthesis approach is presented as a promising route for producing biocompatible γ‐Fe 2 O 3 NPs with potential applications in biomedical fields.