Microwave-Assisted Biosynthesis of ZnO Using Sentul <i>(Sandoricum koetjape) </i>Peel Extract: Effect of Microwave Irradiation Power

Abstract

Physical and chemical approaches for synthesizing ZnO have disadvantages, such as requiring high temperatures, expensive equipment, and dangerous substances. Preparation of ZnO nanoparticles has shifted its focus to the biosynthesis technique involving plant extracts in order to support ecologically friendly activities. In this study, biosynthetic ZnO nanoparticles were produced using Sentul (Sandoricum koetjape) peel extract under two distinct microwave irradiation powers (i.e., 360 W and 720 W) for three minutes. The effects of microwave irradiation power on the morphology and optical properties of ZnO were investigated. Prior to microwave irradiation, Sentul (Sandoricum koetjape) peel extract (20g/l) and zinc nitrate hexahydrate (0.2M) as a precursor were mixed homogeneously. Morphological, structural, and optical absorption of the samples were characterized using field effect scanning electron microscopy (FESEM), X-ray diffractometer (XRD), and UV-Vis spectroscopy, respectively. Surprisingly, the surface morphology of ZnO displays geometric forms resembling flowers. Higher irradiation power resulted in uniformly smaller ZnO nano-flowers. The crystal structure of both ZnO samples is wurtzite with a hexagonal structure. Maximum light absorption occurs at 349 nm and 358 nm, respectively, for ZnO samples subjected to 360 W and 720 W of microwave radiation. However, the bandgap energies are 3.29 and 3.28 eV, which is significantly less than the bandgap energy of bulk ZnO. (3.37 eV). According to the results, it is possible to control the form and size of ZnO nanoparticles using microwave heating.