Enhancing the photocatalytic activity of TiO۲ 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 (TiO۲/CQDs). The X-ray diffraction (XRD) analysis of this TiO۲/CQDs nanocomposite has revealed that the presence of CQDs in these TiO۲/CQDs does not affect the TiO۲ NPs crystalline structure; while the characterization using scanning electron microscopy (SEM) analysis shows a porous structure of TiO۲ NPs and TiO۲/CQDs resulting from the aggregation of nanoparticles with a mean size of around ۲۵ nm and ۳۰ nm for TiO۲ NPs and TiO۲/CQDs, respectively. Furthermore, a transmission electron microscopy (TEM) analysis displays particle size around ۴ nm for CQDs. Besides, the reflectance study in the visible range shows that the presence of CQDs reduces the reflection of sunlight by TiO۲ NPs in TiO۲/CQDs nanocomposite. Moreover, compared to TiO۲ NPs, TiO۲/CQDs have a higher rate for methylene blue (MB) photocatalytic degradation. Indeed, an efficiency of up to ۱۰۰% within ten minutes of sun exposure for the degradation of ۷.۵ mg/L MB can be achieved using TiO۲/CQDs in opposition to thirty minutes using TiO۲NPs under the same conditions. This efficiency is obviously due to the reduction of the reflective properties of TiO۲ NPs in the visible range by the presence of CQDs in the TiO۲/CQDs nanocomposite. These results suggest that TiO۲/CQDs could be used as heterogeneous photocatalyst for the degradation of similar compounds in water bodies under solar irradiation.

Keywords:

Carbon Quantum Dots (CQDs) , Fluorescent CQDs , Methylene Blue Photocatalytic Degradation , Reduction of TiO۲ Reflective Property , TiO۲ Nanoparticle Synthesis