Investigation of optical and thermal properties of CuO and ZnO nanoparticles prepared by Crocus Sativus (Saffron) flower extract

Abstract

Among all the metal oxide nanoparticles, CuO and ZnO nanomaterials are very popular and showcase the tremendous properties. They can be prepared from various physical, mechanical, biological, and chemical methods. But, a biological method like the green synthesis of metal oxide nanoparticle by plant or flower extract has become more popular due to its simplicity, low cost, feasibility, and eco-friendly impact. In the present paper, we have prepared both CuO and ZnO nanoparticles by Crocus Sativus (Saffron) flower extract followed by calcination at 400 °C for 15 min. The prepared metal oxide nanoparticles were characterized by UV–visible spectroscopy to study the bandgap energy, and the value was found to be 3.52 eV for CuO and 3.4 eV for ZnO nanoparticles, respectively. The morphology of the prepared metal oxide nanoparticles was studied by scanning electron microscopy, and phase, strain, and crystallite size were investigated by using X-ray diffraction. The investigation of the thermal properties of the CuO and ZnO nanoparticles was performed by thermogravimetric and differential thermal analysis. We determined the percentage weight loss, enthalpy change, and activation energy at 6, 8, and 10 °C/min heating rates. The activation energy of CuO and ZnO nanoparticles was calculated by the Kissinger method and was found to be 13.34 and 8.86 kJ/moles, respectively. The particle size of CuO and ZnO nanoparticles was found to be 300 and 450 nm, respectively. The Fourier-transform infrared spectroscopy was performed to study the functional groups present in both the nanoparticles.