Tailoring Iron Oxide Nanoparticles via pH-Controlled Phyllanthus emblica Extract: A Dual-Functional Platform for Dye Remediation and Biomedical Applications

Green synthesis offers a sustainable approach to nanoparticle manufacturing using plant-derived phytochemicals as natural reducing and capping agents. Herein, iron oxide nanoparticles (IONPs) biosynthesis was performed using Phyllanthus emblica extract at pH conditions (6, 9 and 12), indicating the significant role of reaction environment in nanoparticle formation and stability. Herein we performed phyto-IONPs and successfully synthesized them in various pH and systematically characterized them for their structure, optics and functionality. X-ray diffraction analysis revealed phyto-IONPs to be crystalline with mean crystallite sizes of 32.82, 27.56, and 37.26 nm for pH 6, 9, and 12, respectively. Transmission electron microscope showed mostly spherical nanoparticles with mean particle size 23.8 ± 2.6 nm (pH 6), 24.3 ± 2.7 nm (pH 9) and 25.1 ± 2.8 nm (pH 12). Dynamic light scattering measurements showed relatively larger hydrodynamic diameters, being 343, 189 and 279 nm, demonstrating the particle aggregation characteristics, in colloidal systems. The zeta potential values of –20.3, –26.8, and –25.2 mV indicated moderate colloidal stability, with pH 9 showing relatively better dispersion among the three conditions studied. UV-Vis spectroscopy and Tauc plot showed band gap energy of 3.23, 2.59, and 3.02 eV, which means tunable optical properties with pH variability. Fe–O–Fe stretching vibrations were also observed by FTIR spectra at 693, 676, and 626 cm -1 . Results showed BET analysis of surface areas of 2.37, 4.35 and 1.81 m 2 /g corresponded to pore sizes of 20.11, 27.83 and 23.72 nm. The catalytic activity of Phyto-IONPs was evaluated for methylene blue (MB) dye degradation and eosin yellow (EY) dye degradation. The degradation efficiencies attained significantly improved with H 2 O 2 (85.90% for MB and 83.08% for EY at pH 9), which clearly corresponds to more efficient activity of the catalysts under mildly alkaline conditions. The NPs synthesized at pH 9 exhibited the highest antioxidant activity, with IC 50 values of 79.13 μg/mL (DPPH) and 74.32 μg/mL (ABTS). Overall, the results suggest that pH was significant in characterizing the physicochemical properties of the phyto-IONPs, that was the basis for the stimulated catalytic and antioxidant activity, and pH 9 was highest.