Effect of precursor concentration on the bandgap energy and particles size for green synthesis of hematite α-Fe2O3 nanoparticles by the aqueous extract of Moltkia ciliata and evaluation of the antibacterial activity

Green synthesis of metal oxide nanoparticles using plant extracts is a promising alternative to the traditional method of physical and chemical synthesis, as it is a wide research field and environmentally friendly methods. In the current study, iron oxide nanoparticles (alpha-Fe2O3-NPs) were bio-synthesized by using Moltkia ciliata plant extract with different concentration of ferric chloride (FeCl3). To improve the yield, we relied on changing the concentration of the saline solution (0.1, 0.05, and 0.025M(. These alpha-Fe2O3 NPs were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and energy-dispersive X-ray (EDX). UV-Vis analysis shows absorption maximums at the range 200-400nm belonging to Fe-O, and FT-IR shows clear peaks in the range 450-500 cm(-1), which are attributed to the vibration of Fe-O, while the SEM and DRX results are constructed. There are similarities in the structure of the samples in terms of shape and size, despite their different concentrations. Antibacterial studies were used against Gram-positive and -negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus). The sample synthesized at a concentration of 0.05M showed the highest antibacterial activity (inhibition zone) up to 11.7 mm at a concentration of 0.025 M for Klebsiella pneumoniae. This study concluded that the biosynthetic alpha-Fe2O3 using Moltkia ciliata extract gave significant antibacterial activity.