Irié Bi Irié Williams^{1, 2,}, Aka Alla Martin¹, Moro Koua³, Pomi Bi Boussou Narcisse¹, Koffi Koffi Kra Sylvestre¹, Essy Kouadio Fodjo¹

ZnO/CQDs and ZnS/CQDs nanostructures were prepared by simply mixing ZnO and ZnS nanoparticles with carbon quantum dots (CQDs) to compare their photocatalytic performance in the degradation of methylene blue (MB). X-ray diffraction (XRD) analysis revealed that the presence of CQDs does not affect the crystalline structure of the ZnO and ZnS nanoparticles (NPs). Furthermore, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis revealed a porous structure resulting from the aggregation of NPs with average diameters of approximately 30 nm and 39 nm, respectively for the ZnO/CQDs and ZnS/CQDs nanocomposites. Furthermore, the study of reflectance in the visible spectrum of sunlight showed that the presence of CQDs reduces reflectance, with reflectance percentages of approximately 86% and 88%, respectively for ZnO/CQDs and ZnS/CQDs nanoparticles. Under optimal conditions between 11 a.m. and 3 p.m. with solar exposure, photocatalytic activity achieved 100% degradation of MB (10 mg/L) in aqueous solution in 80 minutes and 120 minutes, respectively for ZnO/CQDs and ZnS/CQDs. The best photocatalytic performance was achieved in the presence of ZnO/CQDs. Consequently, CQDs derived from charcoal can be used for enhancing the photocatalytic properties of semiconductors for the degradation of organic pollutants in aqueous media under irradiation.

Nanoparticles (NPs), carbon quantum dots (CQDs), photocatalysts, methylene blue (MB), degradation