Nickel Oxide Based Nanoparticles: Green Synthesis, Morphological Assessment, and Their Biological Properties

Nanotechnology has been successfully implemented for improved applications in biological activities and environmental remediation. Nickel oxide nanoparticles (NiO-NPs) are effectively synthesized from bio-inspired sources, and their effectivity is higher than that of chemically synthesized NiO-NPs. Biogenic synthesis is mostly favored due to its low cost and eco-friendliness. Properties of NiO-NPs, such as wide bandgap, semi-conductivity, good electrochemical performance, etc., have proved to be superior to those of other Metal Oxide Nanoparticles. Phytochemicals present in various medicinal plant materials act as chelating agents, capping agents, and stabilizers for the green synthesis of NiO-NPs. While various organic molecules present in microorganisms reduce metal salts to Metal Oxide Nanoparticles as they act as reductants or dispersants, distinct characterization techniques such as XRD, SEM, TEM, UV-VIS, FTIR, EDS, etc. are used to confirm the formation of NiO-NPs and for their morphological studies. Green chemistry is witnessing rapid progress by virtue of its ease of synthesis, inexpensiveness, non-toxicity, and renewability. NiO-NPs have a wide range of applications. Biochemical applications such as antifungal, antibacterial, antidiabetic, anticancer, and anti-larvicidal are discussed with their plausible mechanisms. Photocatalytic activities of NiO-NPs are also studied in detail, in which a light-activated catalyst is used for the reduction or oxidation of organic dyes. The present review systematically represents various routes for green synthesis of NiO-NPs, morphological elucidation through well-known quantitative techniques, and potential applications with respect to catalytic and biological fields.