Investigation of structural and optical properties of NiO nanoparticles mediated by Plectranthus amboinicus leaf extract

Abstract Nickel oxide nanoparticles were successfully synthesized by biogenic synthesis method using nickel nitrate as the precursor, mediated by Plectranthus amboinicus leaf extract. The structure of the sample was identified using XRD and confirmed that the particles are with good crystalline nature with an average size is around 100 nm. The morphological and Elemental composition was analysed with SEM and EDAX analysis. There are some agglomerates because of bio molecules present in the leaf extract. The functional groups were identified using FTIR spectroscopy and the strong absorption peak at 452 cm−1 confirms the presence of Ni-O vibration. The bandgap of the synthesized NiO particles was calculated from the Tauc plot based on UV–Vis spectroscopy and found that the value of the energy gap is 3.6 eV. The dielectric constant and dielectric loss concerning various temperatures was calculated and the sample was tested for its antibacterial and antifungal activities. It showed a moderate positive effect in antibacterial test and a positive reaction in the antifungal activity against the fungal strain Candida.