The role of pH in the biosynthesis of Fe₃O₄ nanoparticles prepared from Fe(III) nitrate and matoa leaf extract

Research on nanoparticles is becoming a matter of great interest with constant developments. In particular, biosynthesis is attracting a great deal of attention as an eco-friendly and economical method to obtain nanoparticles. In this report, magnetite (Fe₃O₄) nanoparticles are biologically synthesized using matoa leaf extract (Pometia pinnata) as reducing agent and Fe(NO₃)₃•9H₂O as precursor. The biosynthesis was performed under different pH conditions, that is, 7, 9, and 11, and the as-prepared nanoparticles were characterized using UV-vis, TEM & Selected Area Electron Diffraction (SAED), particle size analyzer (PSA), and XRD analyses. The results obtained from the TEM analysis indicate that the smallest nanoparticles, with sizes ranging from 5 to 10 nm, were obtained at pH 11, which was supported by the PSA result. The TEM result also shows that the nanoparticles became agglomerated, and their sizes were rather diverse. The XRD result showed that the crystallinity of the nanoparticles improved with the basicity of the solutions. From the characterization of the biosynthesized nanoparticles, it was concluded that the smallest nanoparticles exhibiting the best crystallinity were found under pH 11 conditions.