Enhancing the photocatalytic activity of TiO2 nanoparticles using green Carbon quantum dots

A simple and green method based on chemical fragmentation of wood charcoal is used to produce carbon quantum dots (CQDs). These CQDs are used to form a nanocomposite with synthesized titanium dioxide nanoparticles (TiO2/CQDs). The X-ray diffraction (XRD) analysis of this TiO2/CQDs nanocomposite has revealed that the presence of CQDs in these TiO2/CQDs does not affect the TiO2 NPs crystalline structure; while the characterization using scanning electron microscopy (SEM) analysis shows a porous structure of TiO2 NPs and TiO2/CQDs resulting from the aggregation of nanoparticles with a mean size of around 25 nm and 30 nm for TiO2 NPs and TiO2/CQDs, respectively. Furthermore, a transmission electron microscopy (TEM) analysis displays particle size around 4 nm for CQDs. Besides, the reflectance study in the visible range shows that the presence of CQDs reduces the reflection of sunlight by TiO2 NPs in TiO2/CQDs nanocomposite. Moreover, compared to TiO2 NPs, TiO2/CQDs have a higher rate for methylene blue (MB) photocatalytic degradation. Indeed, an efficiency of up to 100% within ten minutes of sun exposure for the degradation of 7.5 mg/L MB can be achieved using TiO2/CQDs in opposition to thirty minutes using TiO2NPs under the same conditions. This efficiency is obviously due to the reduction of the reflective properties of TiO2 NPs in the visible range by the presence of CQDs in the TiO2/CQDs nanocomposite. These results suggest that TiO2/CQDs could be used as heterogeneous photocatalyst for the degradation of similar compounds in water bodies under solar irradiation.