Star fruit extract-mediated green synthesis of metal oxide nanoparticles

The present study deals with the green synthesis, physical characterization, and antibacterial activity testing of various metal oxide nanoparticles (NPs) formed by making use of the star fruit extract. Followed by the synthesis of metal oxide NPs such as ZnO, MgO, and CuO, these have been characterized thoroughly for the optical properties, surface functionality, crystallinity, morphology, and elemental composition. From the UV-vis studies, the observation of absorption bands at 336, 292, and 421 nm confirms the presence of ZnO, MgO, and CuO NPs, respectively. Also, the powder XRD pattern confirm that the prepared NPs are crystalline in nature and fall in the nanoscale size range of 11-22 nm. The field emission scanning electron microscopy (FESEM) provided surface morphological studies of ZnO, MgO, and CuO NPs suggested that the particles are formed in many different shapes of spherical, rod, and hexagonal shape, respectively. The X-ray spectroscopy studies performed in parallel to the FESEM analysis provided a proof for the persistence of Zn, Mg, Cu, and O elements in the respective samples, and thereby confirming for the successful formation of ZnO, MgO, and CuO. Further testing of the antibacterial activity against the clinically important pathogens, such as Staphylococcus aureus, Bacillus, and Pseudomonas, the as-synthesized ZnO, CuO, and MgO NPs are proved to be highly effective. From the overall analysis, this green synthesis route is facile and can be beneficial for the large-scale production of metal oxide NPs that have potential biotechnological significance.