This article reports a simple, cost-effective, and eco-friendly biosynthesis of ZnO/Fe3O4 nanocomposites using Callistemon viminalis leaves’ water extract. For the first time, we used a green synthetic route via C. viminalis leaves’ extract to prepare ZnO/Fe3O4 nanocomposites (NCs) using zinc acetate and ferric chloride as precursor materials. Fourier transform infrared (FTIR) spectroscopic results revealed polyphenolic compounds mainly phenolic acids present in the plant extract acted as both reducing and stabilizing agents to synthesize ZnO/Fe3O4 NCs. Outcomes of XRD and X-ray photoelectron spectroscopy confirmed the formation of ZnO–Fe3O4 heterojunction in ZnO/Fe3O4 NCs, with crystallite sizes of 45, 35, and 60 nm, respectively, according to Debye–Scherrer’s formula. EDX confirmed Zn, Fe, and O in the ZnO/Fe3O4 nanocomposite. Scanning electron microscopy and transmission electron microscopy (TEM) analyses revealed the existence of both ZnO and Fe3O4 in the NCs with some agglomeration. The thermal stability of NCs was evaluated using thermogravimetric analysis (TGA) and differential thermal analysis (DTA) in a nitrogen atmosphere. In addition, as-prepared ZnO/Fe3O4 NCs along with biosynthesized ZnO and Fe3O4 (prepared by C. viminalis extract) nanoparticles were examined for photodegradation of methylene blue under visible light irradiation for 150 min. The result reveals that the photodegradation efficiency of ZnO/Fe3O4 NCs (99.09%) was higher compared to that of monometallic ZnO (84.7%) and Fe3O4 (37.1%) nanoparticles.

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In this study, biomolecules of the aqueous leaf extract of Azadirachta indica were used as a green catalyst for the synthesis of bimetallic- ZnO/MgO nanocomposites (ZM NCs). The function of biomolecules for the fabrication of biosynthesized ZM NCs was studied by FT-IR spectroscopy while the existence of both MgO and ZnO in ZM NCs was confirmed by SEM and TEM micrographs. Results of EDX spectroscopy with element mapping revealed the homogenous distribution of magnesium and zinc in the as-prepared nanocomposites. Powder XRD analysis reflects the polycrystalline nature of NCs with crystallite size ~33nm whereas XPS analysis confirmed the formation of ZnO-MgO heterojunction in ZnO/MgO NCs. In addition, biosynthesized and characterized ZMNCs were evaluated for photodegradation performance using methylene blue solution (40ppm) under visible light irradiation. The achieved degradation efficiency of ZnO/MgO NCs (95.7%) was higher compared to biosynthesized monometallic nanoparticles {ZnO (82.4% and MgO (80.1%)}.

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Herein, we have described one pot synthesis of Cu2OZnO nanocomposites via green route using Callistemon viminalis aqueous leaf extract first for antimicrobial applications and facile synthesis of phenyl xanthenedione. FTIR spectroscopic study of Cu2O-ZnO NCs was carried out to confirm bioreduction of copper and zinc ions by biomolecules present in leaf extract. Elemental composition was detected by Energy Dispersive X-ray spectral study whereas powder XRD analysis revealed nanosize and lattice interaction in the bimetallic composite. Biosynthesized nanocomposites were also screened by SEM, TEM and TGA/DTA techniques. Purity and presence of oxides of copper and zinc in the product had been investigated by X-ray Photoelectron spectroscopy (XPS). Furthermore, synergistic effect of copper and zinc was examined by comparing antimicrobial (against S.aureus, P.aeruginosa and Candida albicans) and catalytic activity (for Phenylxanthenedione synthesis) of Cu2O-ZnO nanocomposites with that of Cu2O nanoparticles. The results indicate that Cu2O-ZnO nanocomposites possess more potential as compared to Cu2O nanoparticles.