Synthesis of iron oxide nanoparticles through one-pot green synthesis using Simarouba Glauca leaf extract and the effect of annealing temperature on antibacterial activity

The aim of the study was to investigate the influence of different annealing temperatures on the characteristics of green synthesised iron oxide nanoparticles. Fe2O3 nanoparticles were prepared through one-pot green synthesis using the extract of freshly plucked leaves of Simarouba Glauca. To examine the effects on the particles’ characteristics, morphology, crystallinity, and antibacterial activity, the particles were annealed at various temperatures of 300°C, 400°C, 500°C, and 600°C. The samples were characterised by performing various analyses such as Scanning electron microscopy, X-ray Diffraction, UV-vis Spectroscopy, as well as antibacterial tests. The SEM analysis did not depict any change in morphology on increasing annealing temperature. The results from the X-ray diffraction spectrum indicate that the crystallite size of synthesised particles fall well within the nanometre range. The pattern shows a transition from amorphous nature to crystalline nature with an increase in annealing temperature along with the formation of α-Fe2O3 (Haematite) at the highest annealing temperature. This was supported by calculating crystallinity, which revealed a sharp rise with rising temperature. XRD pattern was also used in determining the dislocation density and microstrain of the samples. Both these characteristics had a significant reduction at subsequent higher temperatures which indicated a crystal structure refinement. The bandgap for each sample was determined by UV-vis absorption spectrum by constructing the Tauc plot. A significant variation was observed in the absorption spectrum curves of the samples treated over different temperatures. The antibacterial activity of all the samples was tested by filter paper disc agar diffusion method. Escherichia coli and Staphylococcus aureus were chosen as the Gram-negative and Gram-positive bacteria respectively to test the inhibitory action. The samples did not exhibit any activity and annealing temperature did not affect the same. In conclusion, the annealing temperature only had significant effects on crystallinity and absorption while the other properties like morphology and antibacterial activity remain unaffected.