Effect of annealing temperature on structural, optical and photocatalytic properties of CuO nanoparticles

Abstract

In this study, pure crystallographic CuO nanoparticles are successfully synthesized via the sol-gel method through the reduction of copper acetate in water as a solvent. The as-prepared nanoparticles are characterized by X-ray diffraction (XRD), UV-Vis spectrophotometer and transmission electron microscopy (TEM). In order to study the effect of annealing temperature on their morphological and optical behavior, the obtained nanoparticles are annealed at different temperatures, from 200°C to 800°C. XRD studies revealed that by increasing temperature, the full width at half maximum (FWHM) of peaks decreases indicating the enhancement of the grain size of the CuO nanoparticles. Our result also reveals that the optical band gap decreases with the increase of temperature, which can be fully reflected by its variation from 3.83 eV to 2.21 eV when nanoparticle's size varied from 9.84 nm to 188.33 nm respectively, figured out in TEM analysis. In the studied annealed range temperature, the obtained Eg values remain widely higher than reported bulk values. The photocatalytic deactivation/degradation process significantly enhanced the activity of CuO-NPs under UV-visible light in the presence of MB dye, we compare then the photodegradation spectra of CuO-NPs annealed at 200°C, 400°C, 600°C and 800°C, obtained by UV-visible spectroscopy.