Efficient photocatalytic methylene blue dye degradation from green-synthesized silver-doped iron oxide (Ag@Fe2O3) nanostructures

This study presents an environmentally friendly method for synthesizing Ag@Fe₂O₃ nanostructures through a hydrothermal technique that utilizes Saussurea obvallata leaf extract as a reducing and capping agent. The material was characterized using UV-Vis, FTIR, XRD, SEM-EDX, and TEM-SAED-line profile analysis. The UV-Vis shows a maximum absorbance peak at 380 nm, showing a band gap of 3.26 eV. FTIR analysis revealed several functional groups (vibrational modes), including 944 and 514 cm^-1 (Fe-O) and 445 cm^-1 (Ag-O). XRD spectra analysis confirmed the crystalline nature and, using the Scherrer equation, showed an average crystallite size of 49.57 nm. EDX confirmed the presence of only Ag, Fe, and O elements. SEM and TEM-SAED analyses revealed an echinus-like morphology with an interplanar spacing of 126 pm of the nanostructures. The photocatalytic activity of Ag@Fe₂O₃ was investigated through the degradation of methylene blue (MB) dye in the presence of UV-visible light irradiation. It was observed that 97.10% MB dye degradation occurred within 60 min, with the rate constant and half-life being 0.03025 min^-1 and 22.90 min, respectively. It was deduced that the synergistic interaction of Ag with Fe₂O₃ promoted the separation of charge, significantly diminishing electron-hole recombination. This research presents plant extract as a readily available, cost-effective, and environmentally friendly way to produce highly efficient photocatalysts for degrading wastewater dye compounds.