Green synthesis of nickel oxide nanoparticles and its photocatalytic degradation and antibacterial activity

In the present work, we report the biosynthesis of Nickel oxide (NiO) nanoparticles using Senna auriculata aqueous flower extract and their evaluated to the photocatalyst and antimicrobial activities. The synthesized nanoparticles were analysed using UV-Visible (UV-Vis), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Photoluminescence (PL), High resolution transmission electron microscopy (HR-TEM), Dynamic light scattering (DLS), Zeta potential (ZE) and Surface area analysis. The XRD shows the obtained peaks are indexed to the crystalline planes (111), (200), (220), (311) and (222) confirmed that the NiO nanoparticles possessed a good crystalline nature. UV-Vis confirmed that NiO nanoparticles had a direct bandgap at 3.25 eV. DLS analysis and ZE values validated the stability of NiO nanoparticles (53 nm and - 24 mV). HR-TEM analysis revealed that the synthesized NiO nanoparticles had a spherical structure with uniform distribution along the surface. The FT-IR analyses show that the surface of synthesized nanoparticles acts as a reducing and stabilising agent for proteins, carboxyl and hydroxyl groups. The antibacterial activities of biosynthesized NiO nanoparticles are greater against Gram-negative (Escherichia coli) than the Gram-positive microorganism. The catalyst activity of synthesized nanoparticles regarding methylene blue (MB) dye degradation under direct visible light irradiation was studied. The degradation effectiveness against MB dye was found to be 97% for 90 min. Overall, these studies show that Senna auriculata is an effective sell being planted and has the highest probability of being used in the design and development of nanoparticles for environmental pollution and human health.