Green synthesis of ZnO/Fe3O4 nanoparticles with nigella sativa extract: Efficient degradation of methylene blue and antimicrobial properties

Zinc oxide (ZnO), iron oxide (Fe3O4) NPs, and ZnO/Fe3O4 nanocomposites (NCs) were synthesized using Nigella sativa (NS) seed extracts. These nanomaterials (NMs) were characterized by multiple analytical techniques like UV-visible spectrophotometers, FTIR spectroscopy, SEM, and XRD spectroscopy. The UV-visible spectrum showed 364 nm, 330 nm, and 331nm for ZnO NPs, Fe3O4 NPs, and ZnO/Fe3O4 NCs, respectively. Moreover, it was confirmed when the samples were run through FTIR techniques, and it was observed that the availability of bioactive functional groups was involved in the decline of bulk compounds to NPs. XRD showed their average nanoparticle size based on applying the formula of full width at half maximum (FWHM) for ZnO NPs, Fe3O4 NPs, and ZnO/Fe3O4 NCs at 29.52 nm, 22.08 nm, and 12.82 nm, respectively. In this study, the reduction of Methylene Blue (MB) dye was done by NPs and NCs, and their catalytic activities were investigated by a UV-visible spectrophotometer. MB dye showed the maximum absorption peak at 664 nm, and the reaction of MB was reduced using synthesized products with an accompanying color change reaction from blue to colorless within 60 min at 84%, 86%, and 99.5% degradation for ZnO NPs, Fe3O4 NPs, and ZnO/Fe3O4 NCs with rate constants of 0.00035, 0.00065, and 0.0015 Lmol-1S-1. The 2nd order rate constant was observed in this study. The agar disc diffusion method was used to investigate the potential antibacterial activity of synthesized NPs and NCs. This study is best suited for Gram-positive bacteria. NS seed extract-based synthesis of NCs could be an excellent catalyst and biological application for environmental pollution.