Precursor Dependent Structural Phase Evolution in Hydrothermally Prepared Cu2O Octahedrons and Cu Micro-Flakes and Their Structural and Optical Properties

Cuprous oxide (Cu2O) and metallic copper particles with different microstructures have been prepared by a single-step hydrothermal method by using copper acetate monohydrate and sodium hydroxide as precursors, d-glucose as reducing agent, and poly (vinylpyrrolidone) as stabilizing agent. It was found that the concentration of the NaOH in the reactant solution played a significant role in the structural phase formation of the product. Further, it was also optimized to get either the single phase of Cu2O or Cu or the mixed phase of Cu2O and Cu depending on the NaOH content in the reaction mixture. The product material was systematically investigated by x-ray diffraction (XRD), Rietveld refinement, UV-Vis, Raman spectroscopies, scanning electron microscopy (SEM), and X-ray energy dispersive spectroscopy (XEDS). A thorough analysis of the XRD patterns in a standard method as well as by Rietveld refinement have shown the cubic phases for both Cu2O and Cu. The same phases have been retained in the mixed phase sample also. Optical band gap was determined through Tauc plot to be 1.95 eV. Microstructural studies by SEM showed that the Cu particles were formed as micro flakes whereas the Cu2O particles were formed with the well-defined octahedral morphology. The XEDS analysis confirmed the chemical composition in Cu2O. This work reports the dependence of NaOH concentration in the reactant solution on the type of product (single phase or a mixed phases of Cu2O and Cu) and their structural and optical properties.