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Green nanomaterials have been extensively used in the environmental and agricultural applications due to their advantages of biocompatibility, eco-friendly, and cost-effectiveness. In this study, we have employed P. granatum leaf extract as a capping and stabilizing agent for the biofabrication of nickel oxide (NiO) nanoparticles to remove dyes effectively. The key factors which influenced the removal of Methylene Blue (MB) and Congo Red (CR) dyes under both visible and UV light exposure were identified. The experimental findings demonstrated the significant degradation efficiencies, with MB and CR reaching degradation levels of 91.7 % and 81.2 %, respectively. Furthermore, the face-centered cubic (fcc) structure with a space group of (Fm3m) of NiO was observed from the powder X-ray diffraction (XRD) analysis. Additionally, the morphology of NiO nanoparticles were investigated using scanning electron microscopy (SEM). Morphological analysis using high-resolution transmission electron microscopes (HR-TEM) with energy-dispersive X-ray spectroscopy (EDX), revealed the formation of spherical, cylindrical, and rod-shaped, nanoparticles and their elemental composition respectively. Fourier-transform infrared spectroscopy (FTIR) analysis has provided valuable insights into the molecular vibrations and the formation of Ni-O bonds within the NiO lattice. In the PL spectrum, the observed emission peaks at 484 and 545 nm indicate the presence of defects within the NiO structure. Raman spectroscopy further confirms the 2M vibrational mode and a reduction in antiferromagnetic coupling in the samples. Additionally, investigations on NiO nanoparticles at concentrations ranging from 50 to 500 mg/ml have exhibited their influence on bacterial activity against Bacillus cereus and Bacteroides fragilis. [ABSTRACT FROM AUTHOR]

In this study, we described a green, sustainable, and feasible method for synthesizing 5 nm NiO nanoparticles. Eggplant skin was chosen as an appropriate bio-template with a high potential to induce its structure into the desired metal oxide. Two approaches were used and compared to synthesize NiO bio-template: hydrothermal and sol-gel. The morphology and physical properties of the obtained NiO nanoparticles were evaluated using FESEM, TEM, XRD, BET, FT-IR, TGA, and UV–Vis analyses. All these methods confirm that the hydrothermal method is a better approach for synthesizing NiO bio-template nanoparticles than the sol-gel method. UV–Vis analysis revealed that the NiO nanoparticles produced by the hydrothermal method have a low bandgap of 2.88 eV, which is a key factor for photocatalytic applications. [ABSTRACT FROM AUTHOR]