Green synthesis of iron oxide nanoparticles using Bombax malabaricum for antioxidant, antimicrobial and photocatalytic applications

The present work describes the successful fabrication of iron oxide nanoparticles (Fe3O4 NPs) through a green approach using the gum extract of the Bombax malabaricum (B. malabaricum) plant. The bioactive molecules/phytochemicals present in the gum extract of B. malabaricum were found to be responsible for the synthesis and fabrication of engineered nanoparticles (NPs). The Fe3O4 NPs were characterized via UV-VIS, FTIR, and TEM. As indicated by TEM micrographs, the uniform rounded-shaped NPs with an average mean diameter of 09 ± 02 nm were observed. The antibacterial activity of Fe3O4 NPs was investigated against 3 g-positive bacterial strains (Staphylococcus aureus, Bacillus halodurans, and Micrococcus luteus) and 1 g-negative bacterial strain (Escherichia coli) respectively. The antifungal activity of Fe3O4 NPs against the fungal species of Aspergillus niger and Aspergillus flavus was also investigated. The methodologies of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydrogen peroxide (H2O2) radical scavenging assays were also utilized to evaluate the antioxidant potential of synthesized NPs. The enhanced biomedical applications of these NPs were attributed to the extremely small size of the synthesized NPs. Furthermore, the photocatalytic potential of Fe3O4 NPs was also studied by using the degradation reaction of the model pollutant of methylene blue (MB) dye. The influence of the reaction variables on the response (i.e. degradation percentage; D%) was investigated by using two different optimization approaches designated as one-factor-at-a-time (OVAT) and response surface methodology (RSM) approaches. The comparative analysis of these strategies adds to the novelty of our work as the modeling of the photocatalytic reaction via statistics is a rare approach and requires investigation. The RSM exhibited better D% results (98.721%) in comparison to OVAT (94.23%) indicating that rather than the conventional OVAT approach, the RSM should be utilized for the optimization of the MB dyes. Furthermore, it was observed that MB dose acted as the main rate-limiting factor for optimizing the reaction. These additional insights regarding photocatalysis can only be acquired by using the statistical modeling approach.