GREEN SYNTHESIS AND STRUCTURAL–OPTICAL CHARACTERIZATION OF A ZNO/FE₃O₄ NANOCOMPOSITE: IMPLICATIONS FOR ADSORPTIVE AND PHOTOCATALYTIC DYE REMOVAL APPLICATIONS

Abstract

Synthetic organic dyes are a large group of long-lasting water pollutants that pose a significant environmental and health risk. Advanced photocatalytic oxidation processes, involving semiconductor nanocomposites, offer a sustainable method for converting them into fully metallized compounds. A zinc oxide/iron(III) oxide (ZnO/Fe₃O₄) nanocomposite was synthesized using a single-pot precipitation method, employing Camellia sinensis (green tea) leaf extract as a natural reducing and stabilizing agent, without the use of any hazardous chemical reducing agents. The crystalline phase structure was confirmed by X-ray diffraction (XRD), with the results indicating that the dominant phase was hexagonal zinc oxide (wurtzite) (JCPDS PDF#79-0206), with a trace amount of cubic iron(III) oxide (spinel) (JCPDS PDF#19-0629); hematite (α-Fe₂O₃) was excluded as a systematic reflection. Zinc oxide (ZnO) and iron oxide (Fe₃O₄) particles exhibited average crystalline sizes of approximately 16.2 ± 1.8 nm and 25.95 nm, respectively, according to the Debye-Scherer equation. A near-band edge transition was observed at approximately 370 nm using UV-Vis absorption spectroscopy, and Tauke chart analysis (R² = 0.994) indicated a moderate redshift (ΔE ≈ 0.24 eV) of the direct optical band gap from that of pure zinc oxide, which is consistent with the observed interelectron coupling at the ZnO/Fe₃O₄ heterojunction. These results provide a solid foundation for evaluating the efficiency of absorption and photocatalytic decolorization under visible light irradiation in the future.