Green synthesis of Au on ZnO (Au/ZnO) nanoparticles using Ocimum americanum leaf extract: Nature changes of optic, structure, and morphology

Green synthesis of Au on ZnO nanoparticles surface were successfully prepared using Ocimum americanum leaf extract. The reaction was carried out at room temperature using the green synthesis method. The nature changes of optic, structure, and morphology of Au on ZnO nanoparticles surface were characterized using UV-vis diffuse reflectance spectroscopy (UV-Vis DRS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Energy-dispersive X-ray spectroscopy (EDS). UV-vis DRS showed the change of optical properties and the band gap energy values of ZnO and Au/ZnO nanoparticles from 3.21 eV to 3.09 eV. Analysis of FTIR showed the decrease of absorption peak in functional group of -OH, C=C, moreover there is a shift in C-C absorption peak and strong vibration of Zn-O-Au which occurred at wavenumber of 519 cm-1. XRD showed the crystallite size average of ZnO and Au/ZnO is 65.78 nm and 81.99 nm. SEM showed the morphology of Au/ZnO is sphere. EDX shows the mass percent of element composition for Au, Zn, and O is 2.28, 75.50, and 16.11. From the existed data, can be concluded the presence of gold greatly affects to optical properties, structure, and morphology of ZnO nanoparticles surface.