Effect of synthesized carbon quantum dots on the photocatalytic properties of ZnO

ABSTRACT. In this work, synthesized carbon quantum dots (CQDs) and zinc oxide nanoparticles (ZnO NPs) are used to form ZnO/CQDs nanocomposite. The characterization of this nanocomposite using X-ray diffraction (XRD) indicates that ZnO NPs and ZnO/CQDs nanocomposite have the same profile, suggesting that the presence of CQDs does not impinge the crystal structure of ZnO in ZnO/CQDs nanocomposite. Besides, an analysis performed with scanning electron microscopy (SEM) displays plate-like nanostructure with an average thickness of about 22 nm and 25 nm for ZnO NPs and ZnO/CQDs, respectively. Furthermore, the reflectance study in the visible range shows a reduction of sunlight reflection intensity of ZnO/CQDs compared with the reflection intensity of ZnO NPs. In addition, the photocatalytic studies indicate that the rate of photocatalytic degradation of methylene blue (MB) of ZnO/CQDs nanocomposites is higher than that of ZnO NPs. Indeed, in optimized conditions, the photocatalytic activity can reach 100% within 45 min of sunlight exposure for the degradation of 7.5 mg/L MB using ZnO/CQDs while it takes 90 min using ZnO NPs under the same conditions. These fascinating results is attributed to the reduction of the reflective properties of ZnO/CQDs.   KEY WORDS: Fluorescent carbon quantum dots (CQDs), Photocatalytic degradation of methylene blue, Sunlight reflectance property, Synthesis of ZnO nanoparticles Bull. Chem. Soc. Ethiop. 2023, 37(2), 463-476.                                                               DOI: https://dx.doi.org/10.4314/bcse.v37i2.15