One-pot green synthesis of ZnO–CuO nanocomposite and their enhanced photocatalytic and antibacterial activity

C R Rajith Kumar, Virupaxappa S Betageri, G Nagaraju, G H Pujar, Onkarappa H S and Latha M S

Abstract

This work focused on employing Calotropis gigantea leaf extract as reducing agent/fuel and (Zn(NO₃)₂.6H₂O), (Cu(NO₃)₂.3H₂O) as precursors to synthesise ZnO–CuO nanocomposite by solution combustion method. Prepared nanocomposites were characterised using x-ray powder diffraction (XRD), scanning electron microscope (SEM) with energy dispersive x-ray analysis (EDAX), high-resolution transmission electron microscopy (HR-TEM) and Fourier transform infrared spectroscopy (FT-IR). XRD result revealed crystalline nature with average crystallite size of 35 nm. SEM images indicate that particles are agglomerated and EDAX confirms the composition of elements with pure phase. HR-TEM images indicated that average sizes of the prepared ZnO–CuO nanocomposite were 10–40 nm with spherical and hexagonal shapes. The presence of functional groups such as Zn−O, Cu−O, −OH, −C–O, and C–H was confirmed by FT-IR spectrum. The optical energy bandgap was estimated using Kubelka-Munk equation by the aid of diffuse reflectance spectroscopy (DRS). The synthesised nanocomposite showed superior photocatalytic activity of degradation efficiency 97.93% against methylene blue dye. Further, anti-bacterial activity was investigated by agar well diffusion procedure against two bacterial strains (Escherichia coli and Staphylococcus aureus) and significant zone of inhibition to the bacterial strains was observed.