Correlating pH-controlled green synthesis of NiO nanoparticles with their magnetic properties and catalytic performance

Nickel oxide nanoparticles (NiO) were prepared through environmentally friendly methods, using Nigella sativa seed extract as a stabilizing agent and different pH for the working solutions (pH=7, 9 and 11, respectively). In a second step, these NiO NPs were characterized with various and complementary techniques, as X-ray diffraction (XRD), Fourier transfer infrared spectroscopy (FTIR), Brunauer-Emmett-Teller method (BET), scanning electron microscopy (SEM) with EDS profiles, and a vibrating sample magnetometer (VSM). XRD patterns confirmed the one and only formation of NiO, as revealed by the Rietveld refinement procedure. The use of Williamson equation showed a significant variation in structural and microstructural parameters. Fourier transfer infrared spectroscopy (FTIR) analysis revealed vibration modes specific to Ni-O nanomaterials at 470 cm-1. On the other hand, magnetic investigations highlighted the fact that NiO, obtained in a solution with a pH equal to 9,called NiO-9, has the highest Ms and Mr values, of the order of 1.524 and 0.084 emu/g respectively, thus improving its ferromagnetic performance. Moreover, in the presence of NaBH4 and with the aim to reduce 4-nitrophenol to 4-aminophenol, in the case of water treatment, it appeared that the total time for the catalytic activity of NiO-9 was the lowest, i.e., 30 min. Moreover, NiO-9 was characterized by the faster rate constant, namely 0.29 min-1, which could be linked to intrinsic properties of this material (microstrain, electroactive sites and generated carrier charges).

Automated summary

Nickel oxide nanoparticles were prepared using environmentally friendly methods and characterized using various techniques. Nickel oxide prepared at pH 9 exhibited the highest magnetic properties and catalytic activity.