Ball mill-hydrothermal method for one-step synthesis of zinc oxide/carbon quantum dot (ZnO-CQD) nanocomposites as photocatalyst for degradation of organic pollutants

In this work, we report a cost-effective, green, one-step, and new method without any extra materials to prepare ZnO/CQD photocatalyst. Hence, ZnO nanoparticles and zinc oxide/carbon quantum dot (Z-CQD) nanocomposites were synthesized using zinc salt, KOH, and sucrose through the new green ball mill-hydrothermal method. The prepared nanomaterials were characterized by FT-IR, TEM, XRD, FE-SEM, TGA, and UV–Vis absorption. The analysis of the TGA result shows the presence of around 6 wt% of CQD in Z-CQD nanocomposite. The presence of CQD in ZnO nanoparticles decreased the bandgap. The photocatalytic performance of ZnO and Z-CQD were compared by evaluating the degradation of phenazopyridine (PhP), a drug pollutant, and rhodamine B (RhB), an organic dye pollutant, under UV light. The results showed that the degradation rate of RhB is higher than that of PhP. In addition, in the case of RhB, the degradation rate by Z-CQD is higher than that of pure ZnO. Therefore, the presence of carbon quantum dots showed a positive effect on the rate of photocatalytic degradation.